ieee std 1031-2011, ieee guide for the functional specification of transmission static var

IEEE Guide for the FunctionalSpecification of Transmission Static Var Compensators

Sponsored by the Substations Committee

IEEE 3 Park Avenue New York, NY 10016-5997 USA 17 June 2011

IEEE Power & Energy Society

IEEE Std 1031TM-2011(Revision of

IEEE Std 1031-2000)

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IEEE Std 1031™-2011 (Revision of

IEEE Std 1031-2000)

IEEE Guide for the Functional Specification of Transmission Static Var Compensators

Sponsor Substations Committee

of the

IEEE Power & Energy Society Approved 14 May 2011 IEEE-SA Standards Board


Abstract: An approach to preparing a specification for a transmission static var compensator is documented by this guide. The intention of this document is to serve as a base specification with an informative annex provided to allow users to modify or develop specific clauses to meet a particular application. Keywords: filters, harmonics, IEEE 1031, static var compensators, static var system, thyristor-controlled reactor (TCR), thyristor valves, thyristor-switched capacitor (TSC), thyristor-switched reactor (TSR)

•

The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright © 2011 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 17 June 2011. Printed in the United States of America. IEEE, National Electrical Safety Code, and NESC are registered trademarks in the U.S. Patent & Trademark Office, owned by the Institute of Electrical and Electronics Engineers, Incorporated. PDF: ISBN 978-0-7381-6712-1 STD97141 Print: ISBN 978-0-7381-6713-8 STDPD97141 IEEE prohibits discrimination, harassment, and bullying. For more information, visit http://www.ieee.org/web/aboutus/whatis/policies/p9-26.html. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.


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iv Copyright © 2011 IEEE. All rights reserved.

Introduction

This introduction is not part of IEEE Std 1031-2011, IEEE Guide for the Functional Specification of Transmission Static Var Compensators.

This document is a revision of IEEE Std 1031TM-2000. The guide has been renamed and provides an example and general information that may be considered when developing a technical specification for a transmission static var compensator (SVC).

This guide is not a tutorial, and application of its contents in preparing a technical specification shall be done with sufficient technical knowledge and understanding. This guide may not include all topics necessary for every SVC application and does not address any commercial conditions applicable to specific projects.

This guide was prepared by a task force of Working Group I4, FACTS Controllers in Substations, of the High Voltage Power Electronic Stations Subcommittee for the IEEE PES Substations Committee.

Notice to users

Laws and regulations

Users of these documents should consult all applicable laws and regulations. Compliance with the provisions of this standard does not imply compliance to any applicable regulatory requirements. Implementers of the standard are responsible for observing or referring to the applicable regulatory requirements. IEEE does not, by the publication of its standards, intend to urge action that is not in compliance with applicable laws, and these documents may not be construed as doing so.

Copyrights

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Users of IEEE standards should be aware that these documents may be superseded at any time by the issuance of new editions or may be amended from time to time through the issuance of amendments, corrigenda, or errata. An official IEEE document at any point in time consists of the current edition of the document together with any amendments, corrigenda, or errata then in effect. In order to determine whether a given document is the current edition and whether it has been amended through the issuance of amendments, corrigenda, or errata, visit the IEEE Standards Association web site at http://ieeexplore.ieee.org/xpl/standards.jsp, or contact the IEEE at the address listed previously.

For more information about the IEEE Standards Association or the IEEE standards development process, visit the IEEE-SA web site at http://standards.ieee.org.


v Copyright © 2011 IEEE. All rights reserved.

Errata

Errata, if any, for this and all other standards can be accessed at the following URL: http://standards.ieee.org/reading/ieee/updates/errata/index.html. Users are encouraged to check this URL for errata periodically.

Interpretations

Current interpretations can be accessed at the following URL: http://standards.ieee.org/reading/ieee/interp/ index.html.

Patents

Attention is called to the possibility that implementation of this guide may require use of subject matter covered by patent rights. By publication of this guide, no position is taken with respect to the existence or validity of any patent rights in connection therewith. The IEEE is not responsible for identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the legal validity or scope of Patents Claims or determining whether any licensing terms or conditions provided in connection with submission of a Letter of Assurance, if any, or in any licensing agreements are reasonable or non-discriminatory. Users of this guide are expressly advised that determination of the validity of any patent rights, and the risk of infringement of such rights, is entirely their own responsibility. Further information may be obtained from the IEEE Standards Association.


vi Copyright © 2011 IEEE. All rights reserved.

Participants

At the time this IEEE guide was completed, Taskforce 1 of the Static Var Compensators Working Group had the following membership:

Heinz Tyll, Chair

Hubert Bilodeau Samrat Datta Godwin Duru Mikael Halonen Ki Cheong Ho Christopher Horwill

George Karady Janet Kowalski Lauri Latipaa Peter Lips Wayne Litzenberger David Monkhouse Mansour Pourcyrous

Vittal Rebbapragada Mark Reynolds Devki Sharma Dan Sullivan Austin Tingley Duane Torgerson

The following members of the individual balloting committee voted on this guide. Balloters may have voted for approval, disapproval, or abstention.

William J. Ackerman S. Aggarwal Ali Al Awazi George Becker Hubert Bilodeau Wallace Binder Chris Brooks Arvind K Chaudhary Robert Christman Jerry Corkran Alireza Daneshpooy Gary Donner Gearold O. H. Eidhin Gary Engmann David Gilmer Edwin Goodwin Randall Groves Mikael Halonen David Harris Steven Hensley

Gary Heuston Christopher Horwill Lars Juhlin Yuri Khersonsky Joseph L. Koepfinger Jim Kulchisky Donald Laird Chung-Yiu Lam Greg Luri William McBride Georges Montillet Jerry Murphy Jeffrey Nelson Arthur Neubauer Michael S. Newman Lorraine Padden Christopher Petrola Donald Platts Michael Roberts Charles Rogers

Bartien Sayogo Devki Sharma Gil Shultz Hyeong Sim James Smith Jerry Smith David Solhtalab John Spare Gary Stoedter K. Stump John Toth Heinz Tyll Eric Udren John Vergis Jane Verner Ilia Voloh John Wang Kenneth White James Wilson Jian Yu


vii Copyright © 2011 IEEE. All rights reserved.

When the IEEE-SA Standards Board approved this guide on 14 May 2011, it had the following membership:

Richard H. Hulett, Chair John Kulick, Vice Chair Robert Grow, Past Chair Judith Gorman, Secretary

Masayuki Ariyoshi William Bartley Ted Burse Clint Chaplin Wael Diab Jean-Philippe Faure Alex Gelman

Paul Houzé Jim Hughes David Law Thomas Lee Hung Ling Oleg Logvinov Ted Olsen Gary Robinson

Jon Rosdahl Sam Sciacca Mike Seavey Curtis Siller Phil Winston Howard Wolfman Don Wright

*Member Emeritus

Also included are the following nonvoting IEEE-SA Standards Board liaisons:

Satish Aggarwal, NRC Representative Richard DeBlasio, DOE Representative Michael Janezic, NIST Representative

Don Messina

IEEE Standards Program Manager, Document Development

Soo H. Kim IEEE Standards Program Manager, Technical Program Development


viii Copyright © 2011 IEEE. All rights reserved.

Contents

1. Overview .................................................................................................................................................... 1 1.1 Scope ................................................................................................................................................... 1 1.2 Purpose ................................................................................................................................................ 1 1.3 Application .......................................................................................................................................... 2 1.4 Word usage .......................................................................................................................................... 2

2. Normative references .................................................................................................................................. 2

3. Definitions, acronyms, and abbreviations .................................................................................................. 3 3.1 Definitions ........................................................................................................................................... 3 3.2 Acronyms and abbreviations ............................................................................................................... 5

4. SVC project description ............................................................................................................................. 6

5. Scope of supply and schedule ..................................................................................................................... 6 5.1 Scope of supply ................................................................................................................................... 6 5.2 Equipment, materials, and services furnished by the user ................................................................... 7 5.3 Schedule .............................................................................................................................................. 8

6. Site and environmental data ....................................................................................................................... 8

7. Power system characteristics ...................................................................................................................... 8

8. Main SVC characteristics ........................................................................................................................... 9 8.1 SVC rating ......................................................................................................................................... 10 8.2 Control objectives .............................................................................................................................. 12 8.3 Harmonic performance ...................................................................................................................... 12 8.4 Telephone and radio interference ...................................................................................................... 14 8.5 Audible noise ..................................................................................................................................... 15 8.6 Loss evaluation .................................................................................................................................. 15 8.7 SVC availability and reliability ......................................................................................................... 17

9. Main components—required functions and features ................................................................................ 18 9.1 Thyristor valves ................................................................................................................................. 18 9.2 Thyristor valve cooling system .......................................................................................................... 20 9.3 Control equipment and operator interface ......................................................................................... 21 9.4 Monitoring and protection ................................................................................................................. 22 9.5 Reactors ............................................................................................................................................. 24 9.6 Capacitor banks ................................................................................................................................. 24 9.7 Power transformers ............................................................................................................................ 24 9.8 Disconnect and grounding switches .................................................................................................. 25 9.9 Auxiliary power supplies ................................................................................................................... 25

10. Spares ..................................................................................................................................................... 25 10.1 Spares strategy ................................................................................................................................. 25 10.2 Spare parts storage ........................................................................................................................... 26 10.3 Spare parts accounting ..................................................................................................................... 26


ix Copyright © 2011 IEEE. All rights reserved.

11. Engineering studies ................................................................................................................................ 26 11.1 Information submitted with bid ....................................................................................................... 26 11.2 Premanufacturing engineering and design verification studies ....................................................... 27 11.3 Postcommissioning studies .............................................................................................................. 29

12. Tests ....................................................................................................................................................... 29 12.1 Factory tests of valves ..................................................................................................................... 29 12.2 Factory tests of controls ................................................................................................................... 29 12.3 Tests of other components ............................................................................................................... 30 12.4 Field tests ......................................................................................................................................... 30

13. Documentation ....................................................................................................................................... 30

14. Training .................................................................................................................................................. 30

15. Balance of plant ...................................................................................................................................... 31 15.1 Buildings and structures .................................................................................................................. 31 15.2 Fire protection .................................................................................................................................. 31 15.3 Site requirements and conditions ..................................................................................................... 32

Annex A (informative) Bibliography .......................................................................................................... 33

Annex B (informative) Notes for a functional specification ........................................................................ 35

Annex C (normative) Method of calculating thyristor valve losses ............................................................. 73


IEEE Guide for the Functional Specification of Transmission Static Var Compensators

IMPORTANT NOTICE: This standard is not intended to ensure safety, security, health, or environmental protection. Implementers of the standard are responsible for determining appropriate safety, security, environmental, and health practices or regulatory requirements.

This IEEE document is made available for use subject to important notices and legal disclaimers. These notices and disclaimers appear in all publications containing this document and may be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at http://standards.ieee.org/IPR/disclaimers.html.

1. Overview

1.1 Scope

This document provides general guidelines towardguide assists users in specifying the preparation of a functional requirements for transmission static Var compensators (SVCs) using conventional thyristor technology. Many sections will be useful for compensator systems using gate turn-off thyristor technology [static synchronous compensator (STATCOM)] or other semiconductor devices, or SVCs associated with high-voltage direct current (HVDC) converter stations, or industrial and distribution applications. Although this guide may not directly serve for SVCs primarily associated with industrial drives nor with the correction of load disturbances or phase unbalance, many sections will be useful also for these applications.

General terms and conditions forming the commercial part of a specification for a particular project are outside the scope of this document.

1.2 Purpose

Starting at Clause 4, This document presents technical sections that may be used as the basis of a functional SVC specification. The wording deliberately uses “should” rather than “shall” because this document is a guide, not a specification. The user of this guide might wish to make this adjustment when converting sections into a specification. Annex B of this document contains supplemental information intended to further develop specific clauses. Further information is referenced by the same subdivision numbering used in the main text.


The guide describes the following:

Newer developments in SVC component equipment and particularly control systems

Updated information on latest practices for SVC applications

Clarification on topics which led to misunderstanding in the previous version

An informative annex to allow users to modify or develop specific clauses to meet a particular application

1.3 Application

The guide should be considered as a general purpose resource and does not include all details needed for a specific application. Likewise, because transmission SVCs are typically designed to address a specific application, not every part of this guide may be applicable. The user of this guide should evaluate how, and to what extent, each clause applies to the development of an SVC specification.

Clause 3 gives definitions such as a static var compensator (SVC), a static var system (SVS), and associated other reactive elements. This guide applies to the SVC.

1.4 Word usage

In this document, the word shall is used to indicate a mandatory requirement. The word should is used to indicate a recommendation. The word may is used to indicate a permissible action. The word can is used for statements of possibility and capability.

2. Normative references This guide should be used in conjunction with the following publications. When the following standards are superseded by an approved revision, the revision shall apply.

The following referenced documents and URLs are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained). For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.

Accredited Standards Committee C2-1997, National Electrical Safety Code ‚NESC .1, 2 ANSI C63.16, American National Standard Guide for Electrostatic Discharge Test Methodologies and Criteria for Electronic Equipment.1

BS EN 61803, Determination of Power Losses in High-Voltage direct current (HVDC) Convertor Stations with Line-Commutated Converters.2


IEC 61954-2011, Power Electronics for Electrical Transmission and Distribution Systems—Testing of Thyristor Valves for Static VAR Compensators. 3

IEC/TR 60815-05, Guide for the Selection of Insulators in Respect of Polluted Conditions.

1 ANSI publications are available from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036, USA (http://www.ansi.org/). 2 EN publications are available from the European Committee for Standardization (CEN), 36, rue de Stassart, B-1050 Brussels, Belgium (http://www.cenorm.be). 3 IEC publications are available from the Sales Department of the International Electrotechnical Commission, Case Postale 131, 3 rue de Varembé, CH-1211, Genève 20, Switzerland/Suisse (http://www.iec.ch/). IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036, USA.

IEEE Std 18TM, IEEE Standard for Shunt Power Capacitors.4,5

IEEE Std 80TM, IEEE Guide for Safety in AC Substation Grounding.

IEEE Std 139TM, IEEE Recommended Practice for the Measurement of Radio Frequency Emission from Industrial, Scientific, and Medical (ISM) Equipment Installed on User’s Premises.

IEEE Std 519-1992TM, IEEE Recommended Practices and Requirements for Harmonic Control in Electric Power Systems.

IEEE Std 693TM, IEEE Recommended Practice for Seismic Design of Substations. IEEE Std 1303TM, IEEE Guide for Static Var Compensator Field Tests. IEEE Std C37.90TM, IEEE Standard for Relays and Relay Systems Associated With Electric PowerApparatus.

National Electrical Safety Code® (NESC®) (Accredited Standards Committee C-2).6

3. Definitions, acronyms, and abbreviations

3.1 Definitions

For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary: Glossary of Electrical and Electronics Terms & Definitions should be referencedconsulted for terms not defined in this clause.7

commercial operation: The acceptance, by the user, of the static var compensator (SVC) from the supplier.

contract start: The date a contract to supply a static var compensator (SVC) becomes effective, and the user has given notice to proceed.

control range: The total inductive plus capacitive range of reactive current or megavar variation of the static var compensator (SVC), at the point of connection.


lagging operation: Inductive megavarsoperation or reactive power absorption of the static var compensator (SVC), similar to a shunt reactor.

leading operation: Capacitive operation or reactive power generation of the static var compensator (SVC), similar to a shunt capacitor.

mechanically switched capacitor (MSC)/mechanically switched capacitive damping network (MSCDN): A shunt-connected circuit containing a mechanical power-switching device in series with a capacitor bank and sometimes also a damping current limiting reactor (MSC). In typical MSCDN branches, the reactor/auxiliary capacitor is paralleled by a resistor.

4 IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854-4141, USA (http://standards.ieee.org/). 5 The IEEE standards or products referred to in this clause are trademarks owned by the Institute of Electrical and Electronics Engineers, Incorporated. 6 The NESC is available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854-4141, USA (http://standards.ieee.org/). 7 The IEEE Standards Dictionary: Glossary of Terms & Definitions is available at http://shop.ieee.org/. 2National Electrical Safety Code and NESC are both registered trademarks and service marks of the Institute of Electrical and Elec- tronics Engineers, Inc. 4IEC publications are available from the Sales Department of the International Electrotechnical Commission, Case Postale 131, 3, rue de Varembé, CH-1211, Genève 20, Switzerland/Suisse (http://www.iec.ch/). IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036, USA.

mechanically switched reactor (MSR): A shunt-connected circuit containing a mechanical power switching device in series with a reactor.

point of common coupling (PCC8): The connection point between the SVC and the power system at which performance requirements are defined. busbar from which other loads sensitive to voltage may be connected as well as the static var compensator (SVC) and any disturbing load it is required to compensate.

point of connection (POC9): For an SVC with a dedicated transformer, the high-voltage (HV) bus to which the whole is connected. For an SVC connected to an existing transformer or direct connected at low voltage, the busbar to which the SVC is connected.

reference voltage (Vref10): The point on the voltage/current (V/I) characteristic where the static var compensator (SVC) is at zero output (i.e., where no vars are reactive power is absorbed from, or supplied to, the transmission system at the point of connectionwhere the voltage is controlled).

response time: The duration from a step change in control signal input until the voltage changes by 90% of its final change, before any overshoot.

settling time: The duration from a step change in control signal input until the SVC output settles to within ±5% of the required control output.

slope: The ratio of the voltage change to the current change over a defined controlled range of the SVC normally the full (inductive plus capacitive) linearly controlled range of the static var compensator (SVC) at nominal voltage, expressed as a percentage.

static synchronous compensator (STATCOM (static compensator): A static synchronous generator operated as a shunt- connected SVC, whose capacitive or inductive output current can be controlled independently of the ac system voltage.


static var compensator (SVC): A shunt-connected static var generator or absorber whose output is adjusted to exchange capacitive or inductive current to maintain or control specific parameters of the electrical power system (typically bus voltage).

static var system (SVS): A combination of different static var devices and mechanically switched var compensators devices whose outputs are coordinated.

thyristor-controlled reactor (TCR): A shunt-connected thyristor-controlled inductor reactor in series with a thyristor valve. The effective reactance of the inductor is varied in a continuous manner by partial conduction of the thyristor valve.

thyristor-switched capacitor (TSC): A shunt-connected thyristor-switched capacitor whose effective reactance is varied in a stepwise manner by full- or zero-conduction operation of the thyristor valve.capacitor (or capacitor arranged as a filter) in series with a thyristor valve which is used to switch the capacitor ON or OFF. A current limiting reactor or a damping network is connected in series with the capacitor and the thyristor valve.

thyristor-switched reactor (TSR): A shunt-connected reactor in series with a thyristor valve that is used to switch the reactor ON or OFF. thyristor-switched inductor whose effective reactance is varied in a stepwise manner by full- or zero-conduction operation of the thyristor valve.

voltage/current (V/I) characteristic: The relationship between the steady-state current of the SVC and the voltage at its point of connection.

8 Refer to Figure 1. 9 Refer to Figure 1. 10 Refer to Figure 1.


Figure 1—Explanatory figure to POC, PCC, and Vref

3.2 Acronyms and abbreviations

BIL basic impulse level ac alternating current CT current transformer EMI electromagnetic interference ETT electrically triggered thyristors FACTS flexible AC transmission systems GTO gate turn-off dc direct current GIC geomatically induced current HV high voltage HVDC high-voltage direct current LTT light-triggered thyristors LV low voltage MSC mechanically switched capacitor MSCDN mechanically switched capacitive damping network MSR mechanically switched reactor PCC point of common coupling PT potential transformer PLC power line carrier POC point of connection QP quasi-peak


RI radio interference rms root mean square STATCOM static synchronous compensator SVC static var compensator SVS static var system SWC surge withstand capability TCR thyristor-controlled reactor THD total harmonic distortion TIF telephone influence factor TNA transient network analyzers TSC thyristor-switched capacitor TSR thyristor-switched reactor TVI television interference V/I voltage/current VSC voltage sourced converter VT voltage transformer

4. SVC project description

This specification is for the design, manufacture of equipment, construction, installation, test, commission, warranty, training, and placement into commercial operation of an SVC at substation connected to the busbar.

The purpose of the SVC is to regulate the voltage of the kV busbar. The nominal ratings of the SVC are Mvar leading at 1.0 pu voltage to Mvar lagging at 1.0 pu voltage.

A regional and local site location map is shown in Figure xy _. A simplified system, one-line diagram showing the sources, interconnected transmission lines, and other system components is attached in Figure xy _. A proposed one-line diagram of the substation after installation of the SVC is shown in Figure xy . The area for the SVC facility is shown in Figure xy . The points of electrical interconnection of the supplier-furnished SVC and the user-furnished facilities are shown on the following figures:

Figures xy ___

(site location) (system one line diagram / substation electrical environment) (power circuit) (grounding) (station service) (control and protection)

and, for turnkey projects

(fencing) (site subsurface and geotechnical data) (other)


The design and layout of the SVC facility should provide for future expansion requirements as shown in Figure xy .

The “figures xy” mentioned previously are figures that may be attached to the specification as additional information but are not necessary information for the design of the basic SVC components

See Annex B for additional discussion of the SVC specification.

5.Scope of supply and schedule

5.1 Scope of supply

The equipment, materials, and services to be furnished by the supplier may include, but are not limited to, the list shown in Table 1.

Table 1 —Example for equipment , materials , and services to be furnished by the supplier

b) High-voltage (HV) ac equipment, transformer, switchgear, circuit breaker, disconnects, potential

transformers (PTs), current transformers (CTs), surge arresters grounding transformers

c) Reactors, capacitors, and harmonic filters

For turnkey supply, following are added:

No. Item Check if requested

Turnkey projects

Remarks

1 SVC thyristor valve and valve cooling equipment

2 Step down or coupling transformer 3 HV switchgear: circuit breaker,

disconnects, grounding switches 4 Low voltage (LV) switchgear (circuit

breaker, disconnects, grounding switches) and cables if used for connection to LV bus

5 Measuring equipment Voltage transformers (VTs) Current transformers (CTs)

6 Surge arresters 7 Grounding transformers 8 Reactors 9 Capacitors 10 Harmonic filters 11 SVC station services 12 SVC yard control, protection, and alarm

and monitoring systems 13 Special maintenance equipment and tools


14 Training program for operation and maintenance personnel

15 Spare parts 16 Testing and commissioning services 17 Documentation including instruction

manuals 18 Civil works for the SVC, including the

switchyard, fencing, drainage, and access andparking

X

19 SVC building, including air conditioning and grounding X

20 SVC foundations and structures to mount busbars, including grounding and ground matconnections

X

21 Fire detection and protection systems (building and components)

22 Physical security systems 23 Others

5.2 Equipment, materials, and services furnished by the user

The nonelectrical data to be supplied by the user is given in Clause 6; the electrical data is in Clause 7 through Clause 9.

The user should furnish the following equipment, materials, and services:

a) Site for the SVC available calendar days after contract start

b) Source of water for construction

c) Source of temporary station service power for construction at kV,available calendar days after contract start

d) sources of permanent station service power for the SVC at ___ kV,available _calendar days after contract start e) Existing facilities and equipment

5.3 Schedule

Project completion is calendar days after contract start. The supplier’s project schedule is due calendar days after contract start and should include such details as dates for commencement and completion of work on several controlling features of the project, dates for user-furnished services, dates on which supplier-furnished drawings will be provided and approval given, and dates and length of time of any required power outages.

Design review meetings should be held between the user and supplier to review and discuss progress of the design and supply of the SVC. The first design review should be held within calendar days after contract start. Subsequent design reviews should be held every calendar daysaccording to the agreed project schedule.


6. Site and environmental data

The SVC should be designed to meet all rating and performance requirements specified in this document while operating in the site and environmental conditions listed in Table 2.

Table 2 —Example for site and environmental data

No. Type of information Value Units

1 Site elevation above sea level m 2 Maximum ambient dry-bulb temperature °C 3 Maximum ambient wet-bulb temperature °C 4 Minimum ambient air temperature °C 5 Maximum daily average ambient air temperature °C 6 Minimum daily average ambient air temperature °C 7 Ice loading conditions (thickness) mm 8 Maximum ground snow depth m 9 Maximum frost depth m 10 Maximum steady wind velocity m/s 11 Wind gust factor or maximum wind gust m/s 12 Seismic zone and withstand data as per IEEE Std 693TM 13 Isokeraunic level days/year 14 Dust concentration (or pollution level per IEC 60815-05) mg/cm2 15 Salt concentration mg/cm2 16 Solar radiation level W/cm2 17 Ground Earth resistivity Ohm-m 18 Humidity %


7. Power system characteristics The alternating current (ac) power system characteristics apply at the point of connection prior to SVC installation. Normal SVC operation is required within the parameter values and durations given in Table 3.


r) Lightning impulse protective level (BIL) ___________ kV peak

8. Main SVC characteristics

The output of an SVC can be adjusted continuously (smoothly) or in discrete steps depending on the thyristor branches connected to the SVC LV side. If the proposed SVC configuration is made up by only switchable branches (TSC and TSR), the switching of the largest branch should not result in voltage step larger than % at the point where the voltage/current (V/I) characteristic is defined.

8.1 SVC rating

These clauses define the ratings of the compensator equipment. More detailed information on the following items are added to Annex B:

a) The SVC should regulate the kV bus voltage to a reference voltageof kV (1.0 per unit), continuously adjustable between per unit and per unit.

b) The nominal capacitive reactive power output of the SVC should be MVar at 1.0 pu ac bus voltage and nominal system frequency, and 20 °C ambient temperature. Refer to the voltage/current (V/I) characteristic on Figure 3 at point A.

c) The nominal inductive reactive power output of the SVC should be MVar at 1.0 pu ac bus voltage (and nominal system frequency, and 20 °C ambient temperature. Refer to the voltage/current (V/I) characteristic on Figure 3 at point B.

d) The nominal slope of the characteristic should be adjustable in steps of not greater than _% between % and _%, on a basis of (A+B (optional G+B)) MVA (see Figure 2 and Figure 3).

e) The SVC should continue to generate reactive power during a temporary undervoltage down to the value given in line 6 of Table 3 for the duration given in line 7 of Table 3 (point C optional C' on Figure 2 and Figure 3); the SVC may be tripped (or blocked) if the undervoltage persists for more than s.

f) The SVC should continue to absorb reactive power during a temporary overvoltage in a controlled manner up to the value given in line 4 of Table 3 for the duration given in line 5 of Table 3 (point D on Figure 2 and Figure 3); the SVC may be tripped if the overvoltage persists for more than s.

g) (Optional) The temporary capacitive reactive power output of the SVC should be Mvar at per unit ac bus voltage for s (Figure 3, point G), after 1 h operation at or below the level specified under item b).

h) (Optional) Continued controllable conduction of the SVC to absorb reactive power should be possible up to per unit ac bus voltage for s, following 1 h operation at or below the level specified under item c).

i) The SVC should be capable of repeating temporary operation as defined in any one of items e), f), or g) every min.

j) The compensator transformer and all bus equipment such as filter branches, TSC branches, thyristor-switched reactor (TSR branches, thyristor-controlled reactor (TCR) branches,


capacitor bank branches, and reactor bank branches (whether at HV or LV) should be rated to withstand the specified continuous and shortterm operation, and to withstand or be protected against voltage and current stresses that exceed these conditions.

k) All equipment in the SVC system should be capable of sustaining, without damage, any fault limited by the maximum design short-circuit level of the system and the SVC transformer impedance. Taken with its normally connected, if a coupling transformer, all SVC equipment should sus- tain, without damage, any internal fault no matter what fault level is available on the HV system(s)used.

Figure 2—V/I characteristic of the SVC to define ratings at nominal voltage operating points

A is defined by item b) giving the nominal capacitive susceptance, OA. Bdesign point for continuous operation. B is defined by item c) giving the nominal inductive susceptance, OB.design point for continuous operation. C, C' is defined by Clause 7 (lines 6 and 7 of Table 3).

Below point C, C' the SVC should normally block TSC branches, if included, and await a recovery of voltage before resuming normal action.

D is defined by Clause 7 (lines 4 and 5 of Table 3). It is an extension of line 0B. E is an extension of line 0A at maximum reference voltage (K) and minimum slope. F is an extension of line 0B at maximum reference voltage (K) and maximum slope. G is defined by item g) giving the capacitive design point for short time operation.

H and J give minimm voltage settings for continuous operation at maximum and minimum slope, respectively.K is a most severe operating condition, chosen to define filter component ratings.


H is an extension of line 0A at minimum reference voltage (M) and maximum slope. J is an extension of line 0B at minimum reference voltage (M) and minimum slope. K is the maximum reference voltage. L is the nominal reference voltage. M is the minimum reference voltage.

Figure 3—Details of SVC operating points

8.2 Control objectives 8.2.1 SVC functions, with priority

The desired function(s) and the priority in which the SVC should respond to them are as follows:

a) Control of three-phase average or positive sequence of the fundamental voltage in steady state

and post faultdynamic operation, with slope in the range of _% to %.

b) Control of phase voltage based on either

1) Individual phase voltage or 2) Positive and negative sequence voltage

c) Control of voltage with superimposed reactive power control. The reactive power returns SVC output slowly to a preset steady-state value, so that its megavar capacity to support voltage is held in reserve.

d) Voltage control with superimposed damping control based on active power, speed, or frequency measurements to damp oscillations or to enhance the power transfer capability.

e) The SVC should not trip during the dead time of ms during automatic reclosing operations.

8.2.2 Response

The change of measured system voltage to small disturbance (typically <3%) should reach 90% of the desired total change within ms of the initiating control signal a % step change of voltage reference. The maximum overshoot should not exceed % of the ordered change final value, and the settling time should not exceed ms, after which the voltage should be within ±5% of the final value (see Figure 4). This response is requiredcharacteristic within these limits shall be achieved when the system three-phase fault MVA is between the minimum and the maximum value defined in Clause 7. The response of the system voltage using the actual controller should be validated on a real-time simulator. A Thevenin network equivalent is sufficient for this purpose.


Figure 4—Definition of response and settling time

8.3 Harmonic performance

The SVC system should be designed to minimize the effects of resonance among its shunt capacitor banks, filter branches, and the ac system as well as to limit the harmonic distortion imposed on the connected transmission system. The maximum permissible voltage distortion in transmission systems (often termed “planning level”) is given in various national standards. The contribution of harmonic distortion from the SVC should not exceed a specific amount that has to be stated by the SVC purchaser so as not to result in excessive voltage distortion in cases where high harmonic distortion already exist due to other harmonic sources.

The SVC purchaser will also need to indicate whether the full planning level limit (taking into account the distortion already existing) is available for the distortion due to the SVC or only a part of that planning level is available based on the size of the SVC as a proportion of the total MVA capability of the substation (refer to Appendix E of IEC 61000-6-3:2011 [B20]11).

Consideration should also be given as to whether the specified limits are “incremental,” i.e., due only to the effects of SVC generated harmonics, or “aggregate,” i.e., due to the effects of the SVC generated harmonics plus the effects that the SVC has on preexisting distortion (due to magnification or attenuation). The latter is preferred because the principal concern in respect of power quality is the total change that the SVC causes. This is particularly relevant in TSC applications where often only an incremental specification is provided; a low loss designed TSC while not generating harmonic distortion itself can, however, lead to a significant increase in preexisting distortion due to resonance between it and the supply system.

The SVC purchaser should also specify whether the performance limits are such as to satisfy planning levels at the PCC itself only, or to satisfy planning limits at “remote” busbars also (to a certain degree this depends on the performance standard chosen).


8.3.1 Filter performance

The maximum voltage distortion levels as specified should be met for the following:

The continuous range of system and environmental conditions stated in Clause 6 and Clause

7

Variation in tolerance of total filter capacitance, including permissible fuse failures due to manufacturing tolerance, ambient temperature, aging, and changes in capacitance up to alarm level

Variation in tolerance for SVC parameters, such as transformer winding unbalances,

valve firing variations, and unequal reactor and capacitor reactance between phases These performance requirements may be exceeded for system conditions outside the continuous normal envelope specified in Clause 7.

Calculation should take into account all possible combinations and should not be applied equally on each filter branch.

A more detailed description is available in B.5.3.

Typically, one or more filter branches are used to limit the distortion levels in the system.

8.3.2 Filter component rating

The harmonic filter components (and other SVC components) should be rated to carry continuously the harmonic currents caused by the background harmonic distortion of the system and the harmonic currents produced by the SVC itself. Unless otherwise specified, harmonic currents from the system and the SVC should be added quadratically (root sum of squares). the same order should be added arithmetically. All filter harmonic currents of different order should be added quadratically (root sum of squares).

11 The numbers in brackets correspond to those in the bibliography in Annex A.

The rated voltage of capacitors should be derived from the largest arithmetic sum of the power-frequency and individual harmonic voltages obtained from stress calculations in continuous operating conditions.

NOTE—Maximum fundamental voltage and maximum harmonic contributions may not exist at the same time for SVC configurations including TSCs or MSCs.12

For the filter capacitor voltage rating, the loss of capacitor unit or elements should be considered up to the trip level.

The rated voltage of so-called “low-voltage” capacitors (e.g., in double- or triple-tuned filters) should be chosen such as to also withstand imposed transient stresses from energization or other switching events.

Filter rating should take into account additional constraints generated by geomagnetically induced current (GIC) when it applies.


A more detailed description is also available in B.5.3.

8.4 Telephone and radio interference

8.4.1 Telephone interference

For additional details, refer to subclause 6.9 of IEEE Std 519TM-1992.13 Limits for telephone interference should be given, where applicable, as follows:

The I × T product should be less than _, where I × T is defined as the square root of the

sum of the squares of harmonic current (In) and the corresponding weighting factor from the “C-message” weighting factors established in IEEE Std 519-1992.

The kV × T product, otherwise known as telephone influence factor (TIF), should be less than

, where kV × T is defined as the square root of the sum of the squares of harmonic voltage (Vn) and the corresponding weighting factor from the “C-message” weighting factors established in IEEE Std 519-1992

TIFs are required in cases when telephone lines are running close by. Where a current-based criterion is required, the specification of system harmonic impedance, in particular minimum resistance, needs careful definition.

Typical values for TIF are in the range of 20 to 50 and 10 000 A to 30 000 A for the I × T value. More information is provided in B.5.4.1. The user should specify the impedance and the equivalent circuit or model that has to be used for the calculation.

8.4.2 Radio interference . In addition, the radio frequency emissions produced by the SVC should not exceed μV/m over the range of 150 kHz to 1 MHz, when measured 500 m from the SVC station perimeter, except where overhead lines leave the station. The measurements should be made in accordance with IEEE Std 139-1988, based on quasi-peak detector readings.

8.4.2 Broadband interference

The electromagnetic interference generated by substations and transmission lines is propagated by radiation and conduction. The purpose of these general requirements are (1) to limit the electromagnetic noises likely to disturb the power line carrier and (2) to protect the band used in the aid to navigation (200 kHz to 415 kHz), the domestic broadcasting band, and other communication systems located in the frequency range of 5 kHz and 30 MHz, under all conditions of short-time durations or continuous operation. There could be also a need to protect control and protection equipment. The SVC design and layout should take necessary precautionary measures to avoid misoperation, damage, or danger to any equipment or system due to broadband interference and effects. The potential for higher frequency emissions should be limited to avoid interference with any properly licensed or authorized radio, television, microwave, or other equipment in service. Typical guidelines are given in B.5.4. However, the user has to refer to local standards to determine the specific limits acceptable for his or her respective country.


12 Notes in text, tables, and figures of a standard are given for information only and do not contain requirements needed to implement this standard. 13 Information on references can be found in Clause 2.

More detailed information is described in IEEE Std 139TM and is available in B.5.4.2.

8.5 Audible noise

The supplier should design and construct the SVC to limit the audible noise interior and exterior to the facilities. Local noise ordinances and safety codes can be used to establish maximum allowable audible noise levels for interior and exterior areas. Audible noise limits outside the SVC building typically apply at the substation fence line. Inside the building, they apply at a specified distance (typically 3 m) from the emitting source and include the following:. An example for measurement locations is given in B.5.5. The supplier should also be responsible for establishing existing audible noise levels prior to construction of the facilities and for preparation of a report. The final report should record audible noise levels prior to and after construction.

The SVC specification should establish whether a supplier, customer, or third-party acoustic consultant will be responsible for the measurement of audible noise levels. In addition to measurement locations (as discussed previously), the time of day, SVC output levels, instrumentation, and reporting format may be identified.

Existing audible noise levels should be established at the identified locations prior to the construction of the facilities and can be included as part of the specification to bid if available. It is recommended that both preconstruction and postenergization audible noise measurements be performed by the same party using identical instrumentation.

For installations where audible noise output of the SVC is strictly enforced and in cases where ambient noise levels vary, such as in windy environments, the accuracy and repeatability of the acoustic measurements may be critical in establishing compliance with specified values. Class 1/type 1 sound level meters as specified by IEC 61672-1:2003 [B21] and ANSI S1.4-1983 [B4], respectively, are recommended in these applications.

a) Station fence dB(A) b) Within compressor areas dB(A) c) At a distance of m outside of compressor area enclosure(s) dB(A) d) At a distance of m outside of mechanical equipment areas dB(A) e) Maintenance workshop dB(A) f) Control rooms dB(A) g) Relay rooms dB(A) h) Other accessible rooms dB(A)


8.6 Loss evaluation

Power losses of electrical apparatus are becoming increasingly important due to the high cost of energy. The SVC purchaser should clearly state how the cost of losses is considered in the whole SVC project. Some SVC purchasers may consider SVC losses only for information; others may consider cost-evaluated losses in the overall SVC costs. The purchaser should state whether the cost of losses is to be considered in the evaluation of the bid. The losses shall be stated for the POC.

The bidder should supply the estimated or warranted total losses (kW) calculated in accordance with the equations summarized in Annex B and Annex C. It should be assumed that ambient temperature is °C, the busbar voltage is per unit, and the slope setting is %. The SVC may not operate at these conditions, but they provide a common base for evaluation.

For each operating point, losses are calculated for the parts of the SVC in operation or connected, whether conducting current or not. If more than one combination of SVC parts might operate at a given output, both values should be given and separately summated, with explanation, and the average taken forward to the summation.

Losses in switchgear, busbars, cables, clamps, connectors, and so on are excluded. Losses associated with harmonic currents are also omitted from loss calculations for evaluation (although they should be considered to determine ratings of cooling plant and the like). Refer also to BS EN 61803. Losses in the equipment described in 8.6.1 through 8.6.7 should be included in the calculations.

8.6.1 Thyristor valve losses

Thyristor valve losses are made up from thyristor conduction and switching losses, snubber circuit and voltage divider, and if used, current limiting reactor losses. See Annex C for details.

8.6.2 Transformer losses

The transformer losses are a function of the transformer resistance and the root-mean-square (rms) fundamental current in the transformer and core and stray losses.

Transformer losses are normally measured on test at full load and no load. The no load losses should be stated at nominal voltage and no load, and they should be taken as being consumed at all times.

The full load losses should be used to calculate an equivalent resistance of the transformer. Losses of the transformer at each SVC operating point required in 8.6.7 should then be calculated using this resistance and the predicted transformer current for that SVC output.


8.6.3 Reactor losses

The reactor losses are calculated from the rms fundamental phase current I.

For formulas, see Annex B. This calculation applies to TSC and filter reactors, TCRs, MSRs, and TSRs.

8.6.4 Capacitor bank losses (TSC, MSC, and filters)

In the test reports for each capacitor unit as per IEEE Std 18TM, the dissipation factors (tan delta) are given. An average value for all capacitor units is used to calculate the capacitor bank losses. The formula used isFor formulas, see Annex B.

Pcap = Qcap × DF (2)

where

Qcap is the actual capacitor kvar, and DF is the capacitor dissipation factor, which should include the losses in capacitor fuses.

8.6.5 Resistor losses

Resistors are included in damped filter configurations (e.g., high pass filters and MSCDN). The resistor losses are calculated according formulas shown in Annex B.

where

Rres is the resistor resistance, and I is the fundamental RMS phase current through the resistor.

8.6.6 Auxiliary system power

The power used by the auxiliary systems for pumps, fans, and building cooling and heating systems together with the power needed by each thyristor level, if applicable, is deduced for each specified condition of the ambient temperature and reactive power flow. Nominal auxiliary supply voltage is assumed. The values for auxiliary power can be assumed from previous projects and have to be measured after installation for comparison purposes.

8.6.7 Total loss evaluation

The losses for each equipment in operation that the purchaser wants to include (8.6.1 through 8.6.6) are summed for each load level (state whetherfrom full capacitive to full inductive) required output and should be evaluated as follows:shown in a loss curve over its steady-state operating range at a system voltage of 1.0 pu.


The $/kW values take into account the percentage of time the SVC is expected to operate at or near that Mvar output. The losses in the different operating ranges should be averaged and evaluated by the operating time. Refer to B.5.6.

The sum of the above loss valuescost evaluated losses should be added to the firstinvestment cost of the equipment to determine the total evaluated cost of the SVC.

In addition, the supplier should provide a curve for the total operating losses over the entire steady-state operating range at a system voltage of per unitA similar calculation shall be done after erection and commissioning to determine the final loss costs. If the losses are higher than the losses stated in the bid document, the difference should be calculated as a penalty and can be subtracted from the final cost.

For an SVC with a stepped output variation (e.g., TSCs and/or TSR), the specified operating points/ranges in the enquiry document may not coincide with the specified output values. Nevertheless, the supplier shall provide a loss diagram and a description of how the losses may be evaluated (e.g., linear variation between discrete steps) to fit to the information required in the specification.

8.7 SVC availability and reliability

8.7.1 Definitions

The following definitions apply:

a) Forced outages are outages caused by faults in the SVC equipment that result in loss of

part or all of the essential functions of the SVC.

b) Scheduled outages are outages necessary for preventive maintenance to assure continued and reliable operation of the SVC. They may result in the temporary loss of part or all of the essential functions of the SVC.

c) Outage duration is the elapsed time in hours from the instant the SVC is out of service to the instant it is ready to be returned to service.

The following willmay be included in outage duration:


1) The downtime required to determine the cause of an outage or to determine which equipment or units of equipment to repair or replace.

2) The time required by system operators to disconnect and ground equipment in preparation for repair work and to remove grounds and reconnect equipment after the repairs are complete. Delays caused by unavailability of qualified user personnel are not accumulated in the outage duration.

3) Partial outage. If partial SVC output is available, the duration of equivalent outage should be calculated as the product of the derated condition duration and the proportion of the nominal output range that cannot be achieved during this period.

d) Annual availability is the annual equivalent availability for forced outages, both total and partial, in percent and is defined with duration in hours:

8.7.2 Required availability and reliability

Reliability performance is required of the SVC, as follows:

a) The annual availability for forced outages for the SVC should be at least _%. b) There

should be less than (number) forced outages of the SVC per year.

c) The bidder should state the expected or guaranteed average number and duration of scheduled outages per year.

d) The bidder should guarantee the quoted availability performance for years from commercial operation. The supplier will be notified of major outages. During the guarantee period, the user will maintain records of the number and duration of forced and scheduled outages, hours of operation, and any other relevant data and should make those records available to the supplier on request.

If the actual performance is belowdifferent from the values stated in items a) and b) of 8.7.2, the supplier should provide corrections and modifications to meet the availability guarantees at no extra cost to the user. The availability guarantee should then continue until consecutive years of operation within the guaranteed values have been achieved.

e) Maintenance intervals should occur regularly for inspection and, where necessary, repair. The bidder should suggest the maintenance interval suitable for its equipment and should describe any condition monitoring offered.


9. Main components—required functions and features

All materials that will become a part of the completed work should conform to the specifications given in Clause 2.

9.1 Thyristor valves

9.1.1 Overall performance

The thyristor valves should be designed to ensure operate according to the overall performance requirements of the SVC or SVS.

9.1.2 Valve access

The design of the thyristor support structure should permit access by the user for visual inspection, routine maintenance, and component replacement.

9.1.3 Design robustness

The thyristor valve should be designed with individual thyristors and other components applied in a conservative manner with regard to their basic design parameters, as follows:

a) The thyristor valve should withstand maximum overvoltage and overcurrent stresses due to

system faults and switching.

TCR and TSR valves should be controllable up to the voltage given in line 2 of Table 3. TSC valves should be capable of blocking up to the voltage given in line 4 of Table 3.

b) The thyristor valve design should include an appropriate allowance for unequal voltage distribution across individual thyristors in the valve due to stray capacitor and component tolerances.

c) The SVC should be designed to prevent or, alternatively, to withstand, false firing events (i.e., the firing of any valve at an incorrect time in the cycle or when not ordered). The bidder should describe the details of prevention or withstand inherent in its design.

d) Each thyristor valve should be able to operate within component ratings, generally with at least one failed thyristor. The number of possible failed thyristors should be selected by the supplier, demonstrated to the user, and be consistent with the availability requirements of the SVC.

9.1.4 Maintenance

Thyristor monitoring and maintenance requirements are as follows:

a) A monitoring means to identify any thyristors that have failed should be provided.

b) The thyristor valves should be designed to allow easy replacement of failed thyristors.


Other TSC, TCR, and so on or filter branches should be capable of continued service while a thyristor is being changed or during similar maintenance.

9.1.5 Valve protection

The bidder should state the methods of overvoltage protection of the valves and the voltage levels at which these protections operate, as follows:

a) TCR and TSR valves should be protected against overvoltage by a forced-firing system.

b) TSC valves should not be fired under overvoltage, and interlocks and latches should be provided to avoid false firing.

9.1.6 Testing

The bidder should submit a test program for the thyristor valves, including type tests and routine tests in the factory. Refer also to IEC 61954-2011.

9.2 Thyristor valve cooling system

9.2.1 Liquid cooling (if applicable)

If liquid cooling is used, the following aspects should be considered:

a) A closed-loop recirculating system should provide full heat rejection capacity with

redundancy for pumps, heat exchangers, and fans, appropriate to the SVC availability requirements. The cooling system should be able to maintain full capacity at maximum ambient temperature and maximum SVC reactive power output. The cooling system should be able to operate at the lowest ambient temperature and zero output specified, and the bidder should describe how this operation is done.

b) Replacement of certain cooling equipment (e.g., pumps, fans, and cooler unit), if defective, should be possible while the cooling system still operates.

c) A purifying loop to maintain liquid resistivity should be provided. The bidder should state the design value of liquid resistivity and describe the methods of detecting and responding to abnormal conditions.

d) The quantity of deionizing material should be sufficient for a period longer than the specified maintenance interval operation without replacement. Deionizing materials should be replaceable without cooling system shutdown. Instructions for frequency of inspection and change should be given.

The bidder should describe the necessary maintenance actions and their frequency.

e) Maintenance of closed-loop systems and make up for loss of liquid should not be required

more than once a year.


9.2.2 Air cooling (if applicable)

If air cooling is used, the following aspects should be considered:

a) An air cooling system should provide full heat rejection with redundancy in blowers,

filtering, monitoring, and heat exchangers (if required). The cooling system should permit work on a defective unit without shutting down the system.

b) The bidder should describe the air filtering system and details of monitoring of the status of blowers, filters, and other components.

9.2.3 Cooling system protection

The cooling system should monitor its own operation and the condition of the cooling medium, according to the following requirements:

a) For liquid-cooled systems, the protection system should include, as a minimum, the

following warning alarms:

1) Depleted demineralizer (deionizing) cell

2) Low water resistivity

3) Low coolant level

4) Primary pump stopped 5) Primary fan stopped

6) High coolant temperature

7) Failure of pump cycling scheme

b) For liquid-cooled systems, the protection system should include, as a minimum, the following shutdown alarms, at different measured values than in item a) of 9.2.3:

1) High temperature

2) Low coolant level

3) Both pumps stopped or blocked flow

c) For air-cooled systems, the protection system should include, as a minimum, the following warning alarms:

1) Blower transfer

2) High exhaust air temperature

3) High differential pressure across the filter

4) Low air flow

d) For air-cooled systems, the protection system should include, as a minimum, the following shutdown alarms:

1) Excessive exhaust air temperature

2) Loss of air flow


9.3 Control equipment and operator interface

9.3.1 Control equipment

The control systems should achieve the functional objectives given in 8.2. The accuracy of voltage should be within ±_ _% of the reference voltage. The accuracy of the gradient and linearity of the slope delivered by the SVC should be defined in relation to the current, expressed as a percentage of nominal current at maximum output deviation from the theoretical slope defined in 3.1. The maximum deviation should be less than ± % of nominal current.

The valves and controls should be designed to avoid any “cross-talk” interference between antiparallel thyristor pairs.

When TSC switching is included, the bidder should detail the method of coordination between TCR and TSC switching in and out to achieve smooth net output change. Depending on the control principle (e.g., regulator loop with measured current feedback), the deadband may also be frequency dependent.

9.3.2 Operator interface

The operator interface should consider the following functional aspects:

a) The control interface should provide for local and remote control points. Only one control point

should be active at any one time and as determined by a master control point, but it should be possible to view plant status, control settings, and other SVC parameters at all control points.

b) The local control point should be near the SVC control hardware. It should permit the following control functions to be carried out at the local control point only, during commissioning and maintenance:

1) Start and stop sequences

2) Change of reference voltage and slope settings

3) Alarm acceptance and, where appropriate, reset

c) Each control point should indicate as a minimum: 1) Starting or stopping sequence in progress

2) Reference voltage and slope settings

3) The control point selected

4) Any other settings such as supplementary stabilizing signals

5) SVC ON indication

6) SVC OFF indication

7) Three-phase, high-side line currents of the main transformer


8) Total reactive power generated or absorbed by the compensator

9) Primary voltage, single phase

10) Secondary voltage, single phase

11) SVC branches in/out (where applicable)

12) Status and alarm information as follows (list) 9.4 Monitoring and protection

9.4.1 Monitoring

The central control unit should monitor its own operation and the operations of the various SVC components. Two levels of protection should be provided: warning and shutdown. The first-level alarm (warning) indicates that a problem exists but that the equipment or its proper operation is not in immediate danger. The second-level alarm (shutdown) initiates a reduction in output range or a shutdown of the SVC due to equipment problems that might cause damage if left uncorrected.

The first-level alarms include the following as a minimum:

Auxiliary power supply failure; back-up supply in use

Cooling system fan or pump failure; back-up pump or fan is available

Cooling system problems (e.g., low water resistivity and primary pump stopped)

Capacitor failures can exist but within an acceptable quantity

Loss of redundant thyristors

Branch availability

Loss of signal-measuring controlled busbar voltage, with the control continuing to maintain the last SVC operating point, unless the regulated busbar voltage is also the source of synchronizing voltage

The second-level alarms include the following as a minimum:

Loss of all control power

Loss of cooling system rated capabilities

Loss of source of synchronizing voltage

Excessive number of capacitor failures

Excessive overcurrent in a thyristor valve

Loss of thyristors in excess of redundancy margin

The central control unit should also have a built-in protective system for self-monitoring.


9.4.2 Protection

General principles apply as follows:

a) The protection relays and equipment should receive their primary input from current transformers,

voltage transformers, and so on that are either supplied as part of the SVC equipment or, where indicated, provided by the user. Redundant protective functions should be included and demonstrated, but common PTsVTs and CTs are acceptable.

b) All protection equipment and systems should be properly coordinated to prevent incorrect operations of the protection equipment or systems during normal SVC operation, including anticipated abnormal conditions on the transmission system of the user, as specified. Fail-safe principles should be applied throughout.

c) Security monitors or dependability monitors should be clearly indicated in the system requirements.

9.4.3 Component protection

The following is a list of the possible required protection; additional protection may be provided if deemed necessary:

a) Main transformer:

1) Overcurrent

2) Overtemperature (e.g., liquid and hotspot)

3) Differential

4) Ground fault

5) Gas accumulation

6) Sudden pressure relay

b) Main reactors: 1) Overcurrent

2) Negative sequence protection

c) Capacitor banks (or filters):

1) Overcurrent 2) Unbalance

3) Neutral unbalance

d) Bus:

1) Overcurrent or current differential

2) Ground fault

e) Thyristor valves: 1) Overcurrent


2) Overvoltage

3) High junction temperature

f) Master control: 1) Loss of control power

2) Loss of synchronization signal 9.5 Reactors

Dry-type, air-cored reactors for outdoor use are preferredtypically used for currently produced SVC systems. Only a few SVC installations use iron core air-gapped reactors.

The magnetic field strength at any point where personnel have access during operation should not exceed mT (B.6.5).

All structural and fence metalwork, including foundations, should be designed to avoid, as far as possible, metallic loops and parallel circuits in which induced currents can flow.

9.6 Capacitor banks

Shunt capacitor banks should include capacitor units and protective fuses, suitably connected in series and parallel groups, and an unbalance protection scheme in each capacitor bank to indicate possible capacitor failure.

9.7 Power transformers

The transformer should be designed to carry 100% reactive current. Taps (on load or off load) are not required. The winding insulation class should be consistent with system data (Clause 7).

The transformer should be capable of carrying the harmonic currents and of sustaining the voltage levels associated with the SVC under all normal operating conditions without loss of life. The transformer should be capable of carrying a certain level of dc consistent with the SVC design.

Tests should be made in accordance with the latest revision applicable of IEEE or IEC standards for power transformers.

To ensure minimize harmonic generation, the saturation flux density of the transformer should be higher than the maximum flux density reached during normal operation, and the bidder should state the margin by which it is exceeded. The bidder should also state the steel quality to be used and its reasoning for selecting the margin. This maximum flux density is obtained at the highest secondary voltage during any reactive power generation, highest reference voltage, minimum slope, and minimum continuous frequency.


9.8 Disconnect and grounding switches

Grounding equipment for maintenance and repair should be supplied with each separate circuit (e.g., TCR, TSC, and filter) that can be out of service while the remainder of the SVC continues in operation. Grounding equipment for the SVC secondary bus system and for the transformer should also be supplied.

Where it is required that an SVC circuit be isolated, disconnect switches should be supplied.

Disconnect switches and links should be adequately sized to carry the maximum steady-state current that can flow in them (square root of the sum of the squares of the fundamental and harmonic currents), and the momentary currents due to faults.

9.9 Auxiliary power supplies

The SVC equipment should include all the power supplies necessary for its operation, including step-down transformer, ac distribution boards, batteries, battery chargers, and so on. The power supplies should be sufficient to supply all pumps, fans, valves and valve controls, and building cooling and heating systems.

10. Spares

The basic supply of the SVC should include a full complement of essential spare parts, which are to be furnished at the same time and as part of the SVC supply. It is the supplier’s responsibility, based on the particular design for the SVC, to provide adequate spare parts to meet the reliability and availability requirements specified.

10.1 Spares strategy

A strategy for spare parts should be developed to demonstrate that the complement of spare parts will be adequate to meet the reliability requirements specified as follows:

a) The spares strategy should be based on a tabulation of all of the components in the SVC,

down to the level of the lowest “replaceable module.” (In other words, all components suitable for unit replacement at the first level of maintenance should be included in the tabulation, but individual devices that would not be replaced except as part of a shop or bench repair of a replaceable component should not be in this tabulation.)

b) Each component in the tabulation should be identified for its importance to the operation of the

SVC, according to the following classification:

1) Category A: SVC operation is not possible until this component has been repaired or replaced

(e.g., main step-down transformer and shunt reactor).

2) Category B: SVC operation can continue (or resume) at reduced rating, but further failures may lead to an SVC outage (e.g., TCR, TSC, MSR, and MSC).

3) Category C: SVC operation can continue on an emergency basis, but a critical


function has been lost or bypassed. Some risk of further complications or equipment damage exists until the function is restored (e.g., one of two pumps out of service, protective relaying, uninteruptable power supply, or cooling alarm sensors not in service).

4) Category D: Operation can continue without serious impairment (e.g., building services such as lighting or heating).

c) The tabulation should include the failure rate or the expected replacement rate of the component over a 10-year period.

d) The tabulation should include the manufacturer’s name and model number, suggested

source, and estimated delivery cycle.

Each device should either be:

Included on an inventory list of all site spares. The inventory list should show the

description, quantity, and storage location of each spare, assuming that any time that a spare is used, the item is reordered.

Provided with a contingency plan to obtain a replacement on short notice, if a spare is not

being kept on hand. 10.2 Spare parts storage

The spare parts for the SVC should to be stored on site, and the SVC project should be designed to include suitable storage facilities. Where appropriate, storage arrangements for indoor and outdoor equipment should be seismically qualified.

10.3 Spare parts accounting

An inventory of the spare parts should be prepared at the time when the SVC is turned over to the user and again at the end of the warranty period. Any shortages should be replenished by the supplier so that the spare parts inventory is at its 100% level at the end of the warranty period.

11. Engineering studies

11.1 Information submitted with bid

The bidder shall perform engineering studies and submit reports with the proposal that support and summarize the rating of the proposed SVC configuration(s). This should include, but not be limited to, the following items:

a) Report on main equipment rating and design. The bidder should define such items as the

SVC V-I characteristics, design considerations for major equipment rating requirements, verify the SVCs nominal output, and define the maximum fundamental ratings of filter components, TSC, and TCR.


b) Report on preliminary analysis of harmonic performance. The bidder should identify the assumptions and methodology used for calculation of fundamental frequency and harmonic stresses and performance. This should include preliminary verification that the SVC system minimizes the effects of resonance between the SVC branches and the ac system, and verification that the filter

configuration (if used in proposed SVC) limits the harmonic distortion and current distortion at the point of connection to less than the limits identified in the specifications.

c) Report on loss evaluation (8.6).

d) Report on audible noise (8.5).

11.1 Dynamic performance studies Transient and dynamic stability studies verify SVC control system performance during system disturbances, such as major faults and load rejection, and evaluate all functions specified.

a) Study of start-up, including transformer energization, shutdown, and other switching events

b) Study of response time and of the SVC’s behavior and contribution to the system’s recovery from faults

c) Study of SVC protection and protection coordination d) Insulation coordination (including dynamic overvoltages, lightning, and fault and switching

transients) to determine insulation levels, clearance, and arrester ratings

11.2 Premanufacturing engineering and design verification studies

Premanufacturing engineering design and verification studies should be performed by the vendor within the scope of supply after contract start. Engineering studies should be performed within the scope of supply. These studies are in addition to the actual SVC design simulator and field performance tests. The studies should demonstrate that the SVC meets all system and equipment specified performance criteria. Acceptance by the user does not absolve the supplier’s overall responsibility for the proper functioning of the SVC as specified. The bidder should list all engineering studies. Engineering studies should include, but not be limited to, the studies described in 11.2.1 through 11.2.4.

11.2.1 System dynamic performance studies

Dynamic performance studies should verify that the SVC controls the system’s dynamic performance during system disturbances, such as major faults and load rejection, and should evaluate all functions specified under various system conditions (i.e., heavy and light load, and weak and strong system conditions). The following is a list of types of dynamic performance studies:

a) Studies to verify that the SVC provides adequate dynamic control to meet the system and SVC performance criteria for selected local and wide area disturbances


b) Study of response time and of the SVC’s behavior and contribution to the system’s recovery from faults

c) Studies to verify the operation of any supplementary controls designed to damp power oscillations following system disturbances if these controls are to be included

d) Studies to evaluate the interaction of the SVC controls with the other nearby control systems, including HVDC controls, generator controls, and controls of other flexible alternating current transmission systems devices

11.2.2 Harmonic performance and component ratings studies

Studies to verify the adequacy of the SVC harmonic filter design through simulation of the power system response to SVC harmonics. The studies should evaluate resultant maximum harmonic levels at the SVC PCC Determination of , and should determine maximum system harmonic levels should be based on, and thestresses on all SVC components. The system impedance should be represented as described in B.5.3. The study report should include the following:

a) Evaluation of specified system and operating conditions, including maximum and minimum system voltage levels, and maximum and minimum reactive power output of the (Clause 7) under all possible SVC operating conditions b) Evaluation within maximum ranges of filter component tolerances (worst performance values may not occur at detuning extremes) c) Evaluation with maximum system voltage unbalance and firing angle unbalance for

noncharacteristic harmonic generation e) Evaluation of possible resonant overvoltages

d) Evaluation of worst-case resonance condition between SVC and system (refer to B.5.3)

f) Evaluation of GIC effects, if specified

g) Evaluation of the filter thermal ratings based on specified operating conditions h) MSR and

transformer saturation induced harmonics

11.2.3 Electromagnetic transients, control performance and overvoltage studies

Transient overvoltage studies should be performed with the actual controls modeled to verify that the SVC equipment is adequately protected against overvoltages and overcurrents (including excessive valve recovery voltages) from power system transients resulting from switching, fault clearing events, and credible SVC system misoperations. If applicable verification is required, then system harmonics resulting from other system harmonic sources due to GIC or due to subsynchronous resonance conditions do not affect the SVC controls under steady-state or transient conditions. Concerns that should be evaluated include the following:

a) Study of start-up, including transformer energization, shutdown, switching coordination,

and other local area network switching events

b) Study of SVC protection and protection coordination

c) Faults on the high-voltage and low-voltage bus (single line to ground, phase to phase, and three phase)


d) Faults across TCR or TSC

e) The potential for false-firing of any valve under the most severe system conditions

f) Impact of GIC or subsynchronous resonance conditions on controls, if applicable

11.2.4 Insulation coordination study

Overall insulation coordination should be verified by considering the results of 11.2.3 (electromagnetic transients: dynamic overvoltages and fault and switching transients), including the impacts of lightning surges on the SVC equipment. This study should determine and verify insulation levels, clearances, and arrester placement and ratings.

11.2.5 Other studies

Other studies include the following: grounding study, protection coordination, power line carrier (PLC)/radio interference, magnetic field strength, and other studies as applicable.

11.2.6 Software simulation models

The vendor shall provide the following software simulation model(s) to represent and model the proposed SVC adequately in the respective software:

a) Stability model:

The vendor shall provide a detailed SVC dynamics model for use in [Owner-specified software] powerflow and stability simulation software.

The model detail shall be appropriate and complete for positive-sequence power system simulation and analysis that is typically performed with powerflow and transient stability programs. All appropriate control features for such analysis will be modeled, and necessary documentation on the theory and use of model should be provided. The stability model shall be nonproprietary and freely available for distribution.

b) Transients model (as required by the owner): The vendor shall provide a detailed SVC transients model for use in [Owner specified software] transients simulation software.

The model detail shall be appropriate and complete for transient response calculation of the SVC system. All appropriate control features for such analysis will be modeled, and necessary documentation on the theory and use of model should be provided.

Owner to list any additional models, as required.

More detailed information is included in B.8.


11.3 Postcommissioning studies

Refer to 8.6; a similar loss report as submitted with the bid shall be revised to include the as built losses.

12. Tests

Coordination with field tests in IEEE Std 1303-1994 should be required.

12.1 Factory tests of valves Thyristor valves should undergo type and production tests in accordance with IEC 61954-2011. Type tests evidence in lieu may be offered.

Refer to the following guidelines or use them to specify SVC thyristor valve factory tests recommended per IEC 61954-09:1999.

12.1.1 Type tests for TSC, TSR, and TCR valves

a) Dielectric tests

1) Between valve terminals and earth i) AC

ii) Switching impulse iii) Lightning impulse

2) Between phases (for multiple valve units only) i) AC ii) Switching impulse iii) Lightning impulse

3) Between valve terminals

i) AC

ii) Switching impulse

b) Operational tests

1) Periodic firing and extinction 2) Positive voltage transient during recovery 3) Overcurrent with subsequent blocking 4) Without blocking 5) Minimum ac voltage 6) Temperature rise 7) Nonperiodic firing

c) Electromagnetic interference (EMI) tests

1) Firing and extinction


12.1.2 Production tests

a) Connection check. To check that all the main current-carrying connections have been made

correctly.

b) Voltage-grading circuit check. To check the grading circuit parameters and thereby ensure that voltage division between series-connected thyristors will be correct.

c) Voltage withstand check. To check that the valve components can withstand the voltage corresponding to the maximum value specified for the valve.

d) Check of auxiliaries. To check that the auxiliaries (e.g., monitoring and protection circuits) at each thyristor level and the auxiliaries common to the complete valve (or valve section) function correctly.

e) Firing check. To check that the thyristor(s) in each thyristor level turn on correctly in response to firing signals.

f) Pressure test. To check that no liquid leaks exist (for liquid-cooled valves only).

g) Test on individual valve components. All components of the valve should be subjected to rigorous testing, inspection, and quality assessment.

12.2 Factory tests of controls

SVC control function type tests on a simulator should include the following:

Verification of each control function.

Verification of control linearity.

Verification of control redundancy.

Verification of the monitoring system.

Verification of the protection system.

Verification of overall system performance for minor and major system disturbances.

Verification of processor loading of all digital controllers.

Verification of SVC parallel operation with other controls in the system and control stability.

Verification of control equipment performance for auxiliary power supply voltage (ac and dc) and frequency variations (ac).

Climatic test (i.e., verification of control equipment performance for a specified range of ambient temperatures and humidity). If climatic test certificates are available for the conditions specified, no further tests are needed.

Interference tests (i.e., the controls should be tested to operate in the environment of ac

substations and suitable surge withstand capability [SWC]). The tests should be carried out, or


proof of previous testing provided, in accordance with IEEE Std C37.90TM (covering fast transient burst and a damping oscillatory wave) and ANSI C63.16 (electrostatic discharge tests).

Routine production tests of all control functions, and separately of all protection functions, should be made to demonstrate manufacturing quality.

12.3 Tests of other components

All other SVC components should be tested according the relevant equipment standards. Refer to

B.9.1.

12.4 Field tests

Field tests should be carried out in accordance with IEEE Std 1303. 13. Documentation

User should specify the documentation required. Examples are given in Annex B.

14. Training

The supplier should be responsible for providing a training course, at the user’s specified location, which may cover the information listed in this clause. The training course can assume that the user’s personnel are well acquainted with substation equipment, including control protection and communications, but not versed in power electronics.

The training course should cover the following for operations personnel:

Description of the system objective and function of the SVCs, including specified

performance

Valves

Master control and operator interface, access, and so on

Adjustable settings and reasons for their selection

Simulator testing of controls

Protection principles

Operations manuals (Clause 13)

The training course should cover the following for maintenance personnel:


Description of the system objective and function of the SVCs, including specified performance

Valves

Valve testing Master control and operator interface, access, and so on

Valve access, and test equipment and procedure

Valve component replacement procedure

Master controls operator interface test and replacement procedures

Valve base electronics test and replacement procedures

Protection principles and tests

Cooling equipment and its maintenance

Cooling controls and their maintenance

Other specialist equipment (e.g., zero-flux CTs, PTsVTs, and reactors)

Operation and maintenance manuals (Clause 13)

The manuals should be available as texts for each course.

15. Balance of plant 15.1 Buildings and structures

The building should be of a type and design selected by the supplier to meet the functional requirements of the SVC and of the user, as follows:

a) The building should be arranged to house the thyristor valves, SVC controls, and other indoor equipment including spare parts. It should take into account the environmental needs of this equipment and the need to gain access to the equipment for operation and maintenance.

b) The building services should include heating, lighting, ventilation, and air conditioning, as appropriate, for occupied areas or as required to meet the requirements of the installed equipment.

c) The building design should follow all applicable local codes and ordinances.

d) The SVC equipment structures should be designed to meet the requirements of the SVC apparatus [including wind and ice loading, fault-current forces, grounding safety as per IEEE Std 80TM, lightning protection, and seismic (if applicable)]; and designed in accordance with the equipment supplier’s recommendations and nationally recognized standards, such as the National Electrical Safety Code® (NESC®) (Accredited Standards Committee C-2).

15.2 Fire protection

The building (and especially the thyristor valve hall and control room) should be equipped with a fire detection system. The fire detection system should be designed as follows:


a) The failure of any single fire or smoke detector should produce a warning or trouble alarm, but it should not either cause a false “fire detected” alarm or disable the overall fire detection system.

b) The detection of an actual fire should cause the SVC to be shut down and be isolated from all sources of primary electrical energy.

c) Adequate safety equipment (including alarm communication panels, breathing equipment, and evacuation equipment) should be provided in accordance with local regulations (e.g., the Occupational Safety and Health Administration).

15.3 Site requirements and conditions

15.3.1 Construction surveys

Prior to beginning any phase of survey work, the supplier should submit to the user a proposed plan to demonstrate that the lines and grades established by the supplier will meet the requirements specified.

15.3.2 Site conditions

The user should provide the site for permanent installation and rights of way for access. The supplier should be permitted to use such land for construction purposes.

Other items to consider include the following:

a) Protection of existing installations

b) Geological investigations

c) Electric power for construction purposes

d) Water for construction purposes

15.3.3 Safety and health

The supplier should incorporate a safety and health program and take all reasonable precautions to protect the safety and health of employees and members of the public and to prevent damage to public and private property. The safety and health program should be submitted to the user for approval at least days prior to start of construction operations. The program should consider safety meetings, accident records and reporting, personal protective equipment, excavation, structure erection, equipment, environmental quality protection, and safety issues related to substation and transmission line clearances, hot-line orders, and special work permits.


Annex A (informative)

Bibliography

Bibliographical references are resources that provide additional or helpful material but do not need to be understood or used to implement this standard. Reference to these resources is made for informational use only.

[B1] ANSI C37.06-2000, American National Standard for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis—Preferred Ratings and Related Required Capabilities.14

[B2] ANSI C63.2-2009, American National Standard for Electromagnetic Noise and Field Strength Instrumentation, 10 Hz to 40 GHz Specifications.

[B3] ANSI C63.14-2009, American National Standard Dictionary of Electromagnetic Compatibility (EMC) including Electromagnetic Environmental Effects (E3).

[B4] ANSI S1.4-1983, American National Standard Specification for Sound Level Meters.

[B5] Benmoyal, G., et al., “Behavior of the Overvoltage Protection on the TSC Branch of Static Compensators Exposed to Harmonics and Replacement Strategy,” CIGRE SC 34 Colloquium, Antwerp, Belgium, 1993.

[B6] Bonneville Power Administration and Western Area Power Administration, An Annotated Bibliography of HVDC Transmission and FACTS Devices, 1991–1993.

[B7] Bonneville Power Administration and Western Area Power Administration, An Annotated Bibliography of HVDC Transmission and FACTS Devices, 1994–1995.

[B8] CIGRE Guide 139, Guide to the Specification and Design Evaluation of AC filters for HVDC systems (WG 14.30), Chapter 7.15

[B9] CIGRE Publication 25, Static Var Compensators, Working Group 38-01, (I. A. Erinmez, editor), 1986.

[B10] CIGRE Publication 37, Analysis and Optimization of SVC Use on Transmission Systems, Working Group 38-05, 1993.

[B11] Edris, A., Adapa, R., Baker, M. H., Bohmann, L., Clark, K., Habashi, K., Gyugyi, L., Lemay, J., Mehraban, A. S., Meyers, A. K., Reeve, J., Sener, F., Torgerson, D. R., and Wood, R. R. “Proposed terms and definitions for flexible AC transmission systems (FACTS).” IEEE Transactions on Power Delivery, vol. 12, no. 4, pp. 1848–1853, Oct. 1997.

[B12] Forrest, J. A. C., “Harmonic load losses in HVDC converter transformers,” IEEE Transactions on Power Delivery, vol. 6, no. 1, pp. 153–157, Jan. 1991.

[B13] Hingorani, N. G. and Gyugyi, L., Understanding FACTS, New York: Wiley-IEEE Press, 1999.

[B14] IEC 60076-1:2000, Power Transformers—Part 1: General.16


14 ANSI publications are available from the Sales Department, American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036, USA (http://www.ansi.org/). 15 CIGRE publications are available from the International Council on Large Electric Systems, 21 rue d’Artois, 75 008 Paris, France (http://www.cigre.org). 16 IEC publications are available from the Sales Department of the International Electrotechnical Commission, Case Postale 131, 3 rue de Varembé, CH-1211, Genève 20, Switzerland/Suisse (http://www.iec.ch/). IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036, USA.

[B15] IEC 60076-6:2007, Power Transformers—Part 6: Reactors.

[B16] IEC 60099-1996, Surge Arresters—Part 5: Selection and Application Recommendations—Section 1: General.

[B17] IEC 60255-22-4:2008, Measuring Relays and Protection Equipment—Part 22-4: Electrical Disturbance Tests—Electrical Fast Transient/Burst Immunity Test.

[B18] IEC 60871-1:2005, Shunt Capacitors for A.C. Power Systems Having a Rated Voltage Above 1000 V—Part 1: General.

[B19] IEC 61000-4-1:2006, Electromagnetic Compatibility (EMC)—Part 4-1: Testing and Measurement Techniques—Overview of IEC 61000-4 series.

[B20] IEC 61000-6-3:2011, Electromagnetic Compatibility (EMC)—Part 6-3: Generic Standards— Emission Standard for Residential, Commercial and Light-Industrial Environments.

[B21] IEC 61672-1:2003, Electroacoustics—Sound Level Meters—Part 1: Specifications.

[B22] IEC 62271-100:2008, High-Voltage Switchgear and Controlgear—Part 100: Alternating-Current Circuit Breakers.

[B23] IEEE/PES PSRC Working Group, “Static var compensator protection,” IEEE Transactions on PWRD, vol. 10, no. 3, pp 1224–1333, July 1995.

[B24] IEEE Publication 320-2 PWR, Static Var Compensators Planning Operating and Maintenance Experiences, 1990.

[B25] IEEE Std 18TM -2002, IEEE Standard for Shunt Power Capacitors.17, 18

[B26] IEEE Std 430TM-1986, IEEE Standard Procedures for the Measurement of Radio Noise From Overhead Power Lines and Substations.

[B27] IEEE Std 857TM-1996, IEEE Recommended Practice for Test Procedures for High-Voltage Direct- Current Thyristor Valves.

[B28] IEEE Std 1158TM-1991, IEEE Recommended Practice for Determination of Power Losses in High- Voltage Direct-Current (HVDC) Converter Stations.

[B29] IEEE Std C37.90.1TM-2002, IEEE Standard for Surge Withstand Capability (SWC) Tests for Relays and Relay Systems Associated With Electric Power Apparatus.

[B30] IEEE Std C57.12.80TM-2002, IEEE Standard Terminology for Power and Distribution

Transformers. [B31] IEEE Std C57.16TM -1996, IEEE Standard Requirements, Terminology, and

Test Code for Dry-Type Air-Core Series-Connected Reactors.

[B32] IEEE Std C57.91TM-1995, IEEE Guide for Loading Mineral-Oil-Immersed Transformers.


[B33] IEEE Std C57.110TM-1998, IEEE Recommended Practice for Establishing Transformer Capability When Supplying Non-Sinusoidal Load Currents.

[B34] IEEE Std C62.22TM-2009, IEEE Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems.

[B35] Miller, T. J. E., Reactive Power Control in Electric Systems, New York: John Wiley and Sons,

1982.

[B36] Song, Y. H. and Johns, A. T., Flexible AC Transmission Systems (FACTS), New York:

Institute of Electrical and Electronics Engineers, 1999.

17 IEEE publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854- 4141, USA (http://standards.ieee.org/). 18 The IEEE standards or products referred to in this clause are trademarks owned by the Institute of Electrical and Electronics Engineers, Incorporated.


Annex B (informative)

Notes for a functional specification

This annex provides comment and discussion on the preparation of an SVC specification. Reference should be made throughout this clauseannex to the corresponding specification clauses. For ease of reference, the corresponding sections from the main text have been referenced. The term “user” may include purchaser and consultant.

B.1 SVC project description—see Clause 4

B.1.1 Purpose of an SVC

The basic action of an SVC is to change the generation or absorption of reactive power rapidly, in response to a control signal. In most applications, the action is to control a given busbar voltage. Sometimes the purpose is to contribute directly to the reactive power balance at a particular point in an electrical system.

In most transmission networks, the voltage at various points is largely dependent on the power and reactive power flows between them. Changing the flows, by changing the supply of available vars at a node in the network, results in a change in the voltages of the network. An SVC, therefore, brings the ability to regulate the voltage of a power system by means of appropriate control of reactive generation and absorption at a point in the system.

Where the user has not determined the final ratings and requires studies as part of the contract to make a final definition, a base rating may be specified for bidding and evaluation. SVCs applied in distribution systems are typically less complex than transmission SVCs in their design, manufacture, operation, and maintenance. Industrial SVCs are typically applied at or near a load center to mitigate voltage fluctuations, flicker, phase unbalance, or other load-related disturbances. This guide does not specifically address industrial and distribution SVCs, although many features of the guide may be applicable. Similarly, it does not specifically address a STATCOM, although almost all sections would be relevant to its application to transmission systems.

The wording of Clause 4 anticipates the normal usage of an SVC as being the control of voltage, but an SVC can improve various aspects of power system quality by suitable control action. The improvement of one aspect may sometimes degrade another, however, and it may therefore be necessary to set priorities and/or limits to control actions and their effects. The following are 10 main functional objectives in power system performance for which an SVC may be used; the user is invited to select from these objectives and to insert them in Clause 4, giving the priority required. The specific control functions in Clause 8 may follow from these objectives.


a) Voltage control:

1) Steady-state voltage control:

The controlled voltage may be at a different point from the point of connection of the SVC.

2) Voltage stability:

To increase the capacity of a circuit that is limited by low voltage at the receiving end. To restore busbar voltage to normal after a system disturbance (e.g., due to a fault or load rejection).

3) System stability:

To increase capacity that is limited by dynamic stability between machines or machine groups. Transmission capacity in such cases may be limited by voltage excursions on certain busbars, and the action of the SVC may be to limit these excursions to acceptable values.

4) Power oscillation damping:

The deliberate adjustment of SVC reference voltage is also possible to increase the overall damping of power system oscillations following a disturbance, usually in the range of 0.2 Hz to 2.0 Hz, on the network close to the SVC. Power or frequency measurements are made, combined, and fed into a supplementary control function, which will produce a modulating output, optimized for gain and phase shift, for the range of frequency oscillations for that part of the network.

b) Reactive power control:

1) Coordination of var contributions from other equipment:

To control the switching of externally connected shunt capacitors and reactors.

2) Fast correction of variable loads:

The generation or absorption of vars to counteract the effect on voltage of the variation of power and var demand of loads that are balanced between phases but variable in time (e.g., convertor-fed drives for rolling mills).

3) Fast correction of power factor:

The generation and absorption of vars to meet a particular demand of a load or group of loads or to counteract a flicker-generating load.

4) The correction of unbalance:

The generation or absorption of vars asymmetrically between the phases to counteract the negative phase sequence components of loads or system components. The action can balance phase voltages by adding reactive loads in two phases to offset an active load in the other phase.

c) Control of non-power frequency effects:

1) Harmonic filtering:


To reduce the harmonic voltage distortion caused by either the harmonic currents generated by the SVC itself or other system components.

2) Subharmonic filtering:

The SVC cannot be expected to contribute to the removal of all subsynchronous currents or resonances. However, it may, by suitable control responses in the appropriate frequency range, either avoid worsening them or provide a counteracting effect.

If more than one objective is selected, it is important that the user specify the priority in which the SVC is to respond to the objectives.

B.2 Scope of supply and schedule—see Clause 5

Transmission SVCs or other SVCs together with MSCs or MSRs typically include several of the following power circuit elements:

Coupling Interconnecting power transformer

Switchgear

Shunt-connected TCRs and/or shunt-connected TSCs

Shunt-connected TSRs

Fixed shunt capacitor filter banks

The user should define whether the SVC will be supplied on a “turnkey” basis or as equipment only. In either case, it is important to describe all equipment and services required of the supplier (i.e., which items are included in 5.1 and which in 5.2).

The physical scope of an SVC supply should carefully describe the interfaces between the SVC supplier and all other entities. For example, the interfaces often include the following:

The point of connection at power circuit entry

The point of interconnection for station service power

All communications and operator control interfaces

Infeed of voltage and current signals (e.g., from the PCC if it is outside the scope of supply)

Other physical interfaces that may exist at the SVC substation fence boundary (e.g., water supply, sewer, or driveway)

If any MSC or MSR is required or already exists, it should be described here. If the equipment is to be installed in an existing building, then this requirement should be described here.

The time scales and extent of service and monitoring by the user should be stated.


B.3 Site and environmental data—see Clause 6 It is important to specify all local site and environmental conditions for which the SVC will be designed. The SVC should be designed to meet ambient environmental and system conditions. Usually, the user has the best information on, and access to, the soil and ground conditions at the site, but surveys sometimes need to be carried out. The user should also understand that unnecessarily onerous ambient design conditions may increase the price of the SVC. With this understanding in mind, the design environmental and system conditions should be clearly specified by the user.

Possible additional information for Clause 6 is as follows:

a) Atmospheric pollution levels canmay be given as light, medium, heavy, or very heavy, per

IEC 60815-05.

b) If evaporative or once-through cooling water may be used for heat rejection, its availability and chemical content should be given.

c) The SVC should continue to operate correctly, without protective tripping, up to a seismic event defined by appropriate event spectra for the region in question. In many cases, only the maximum simultaneous horizontal and vertical acceleration may be specified (IEEE Std 693).

d) The SVC should safely shut down and de-energize during a seismic event beyond the level or outside the spectra defined in item c) (IEEE Std 693).

B.4 Power system characteristics—see Clause 7

This clause describes the power system to which the SVC may be connected. The data defines both the normal and extreme conditions at the SVC station for which the SVC may be required to continue in uninter- rupted operation.

The following items might be added:

a) Existing surge arrester data

b) Existing local generators and associated torsional modes of frequency

c) Existing circuit breaker and circuit switcher characteristics

d) Existing ac relay characteristics and configuration

e) Existing power line carrier equipment and characteristics

f) Existing fault disturbance and event recorders

g) AC system topology in local vicinity

It may be desirable to specify additional values of the following to represent extreme operating conditions [i.e., the more severe conditions for which the SVC should remain connected (and, therefore, able to respond normally as soon as conditions recover) but not necessarily act normally]. These values and the required response should be given with the data in Clause 7. It is, therefore, implied that beyond these conditions, the SVC may act to protect itself, as follows:


Maximum continuous ac system voltage

Minimum continuous ac system voltage

Maximum temporary ac system voltage (level and duration)

Minimum temporary ac system voltage (level and duration)

Maximum continuous ac frequency

Minimum continuous ac frequency

Maximum temporary ac frequency (level and duration)

Minimum temporary ac frequency (level and duration)

Maximum rate of change of system frequency (df/dt)

Maximum negative-sequence voltage component (percent of fundamental)

Maximum zero-sequence voltage component (percent of fundamental)

If the SVC is to be connected to an existing transformer’s tertiary winding, it is necessary to describe this transformer and give its full nameplate details and the potential short-circuit current at the tertiary terminals. The knowledge of the saturation characteristic of this transformer as seen from the tertiary side is one important factor for the design and shall be provided in the specification. The busbar voltage that is to be controlled by the SVC action should be identified (Clause 4). It is necessary to take into account that because of the inherent coupling between the primary and secondary windings, the control of one busbar may have an adverse effect on the voltage of the other. Instead of supplying the data described in line 29 of Table 3 (supply system harmonic impedance data), the user may prefer to supply system data and require the contractor to perform calculations of the system’s harmonic response. The data should include load flow data and any known harmonic responses of individual items. This approach is generally not recommended because it is inevitable that each tenderer/contractor will produce different results, and it is often the case that the customer is then unable to determine which is correct!

If known, data of the existing harmonic currents in the system are most valuable. All power systems carry harmonic currents to some degree, and a new filter will act as a sink for them. Estimates of how largeTo identify such currents might besources with their influence on SVC design is not practicable unless those sources are necessary whether they are made by the user or the supplier. major, identifiable sources. In reality, the background distortion comprises amultiplicity of small unidentified harmonic current sources resulting in harmonic voltage distortion. The compromise would be to represent this background distortion as a harmonic voltage source behind a system harmonic impedance. One negative aspect is that the stresses on SVC components might increase strongly if the minimum resistance of the harmonic system impedance is not properly represented.


B.5 Main SVC characteristics—see Clause 8

The detailed SVC design will depend on the user’s specification of the following:

Steady-state and short-term (overload) reactive power and voltage ratings

Control objectives and performance

Harmonic performance

Losses

Reliability and availability requirements

B.5.1 SVC rating—see 8.1

B.5.1.1 See item a) through item c) in 8.1

Where an SVC controls the voltage of a busbar different from its connection point, add “the nominal ac bus voltage to which the SVC is connected is kV and 1 per unit refers to kV.”

The usual primary requirement of the SVC is that it will support the network voltage in postfault and/or heavy load conditions in order to increase the power transmission capability. It may also be required to limit voltage variations caused by the daily load cycle and to minimize temporary overvoltage conditions or to achieve other objectives outlined in Clause 4.

It will normally help to clarify the user’s requirements and the supplier’s responsibility by using the so- called voltage current characteristic of the V/I diagram (refer to Figure B.1) to describe and define the steady-state and overload operating regions and their impact on SVC component rating. It is recommended that the base ratings (points A and B in Figure B.1) be defined at 1 per unit voltage.

System studies are frequently carried out using a per-unit system with, commonly, 100 MVA equal to 1 per unit. This value is convenient for the user to adopt when specifying an SVC. The rated line-to-line voltage is normally the base value, equal to 1 per-unit voltage. The rating of an SVC in Mvar is described as the product of rated line-to-line voltage, rated line current, and the 3. In per-unit terms, with the rated voltage equal to 1 per unit, the per-unit rated Mvar of the SVC is equal to the per-unit rated current on a base of 100 MVA. If the SVC is to achieve rated current at other than 1 per-unit voltage, such extra points require definition.

The nominal capacitive and inductive ratings of the SVC are defined, respectively, as operating points A and B in Figure B.1. The continuous operating range of the SVC is typically specified by bounding the allowable continuous capacitive voltage range and the allowable continuous inductive voltage range. A more detailed overvoltage cycle, based on user experience, may be specified to ensureallow bidders to design to a common basis.

B.5.1.2 See item d) in 8.1

Slopes above 5% are rare.


B.5.1.3 See item e) and item f) in 8.1

The short-term operating range of the SVC is typically specified by bounding the allowable short-term capacitive voltage range (for magnitude and duration) and the allowable short-term inductive voltage range.

Point D in Figure B.1 covers transient and dynamic overvoltages in the system and typically lies in the range of 1.3 per unit to 1.8 per unit.

The temporary minimum operating voltage of an SVC should be specified; a value of 0.4 or 0.5 has sometimes been specified on the basis that a voltage below that level indicates a severe fault condition for which it is better not to switch on capacitors. Otherwise, temporary overvoltages could be made worse when the fault is cleared and voltage recovers. An example of an operating SVC characteristic is given in Figure B.1.

Example data for V/I diagram: Primary voltage: 400 kV = 1.0 pu Design point capacitive: x MVar (A) at 1.0 pu Design point inductive: y MVar (B) at 1.0 pu Reference voltage setting: Vref = 0.95 (M)…1.05 (K) pu Maximum temporary operating voltage: 1.3 pu (D) Minimum temporary operating voltage: 0.6 pu (C) Slope adjustment: 0…10%

The V/I characteristic given by the manufacturer may include the following operating limitations imposed by the overload capabilities of the SVC components: Transformer current limitation (a) Transformer power limitation (b) TCR current limitation (c) Limited steady-state overvoltage operation (d)

Figure B.1—An example of a SVC V/I characteristic


B.5.1.4 See item g) in 8.1

Full capacitive operation of an SVC (point E in Figure B.1) is typically required in system operating conditions where the system demands maximum possible reactive power support to overcome critical system outage conditions (e.g., during system faults and voltage recovery). This operating point is typically not required for continuous SVC operation. Allowing this operating condition taking into account the inherent overload capabilities of the used components may result in lower costs for the whole SVC. Transformer overload capability is described in IEEE Std C57.91TM-1995 [B32]. The time constants on heating of transformers may be hours. The overload characteristics of reactors, capacitors, and valves are shown in Figure B.3.

B.5.1.5 See item h) in 8.1

The maximum operating voltage of a TCR or TSR is bound by the thyristor junction temperature that will permit blocking for control. If the TCR or TSR is continuously firing (i.e., fully on), then no blocking of thyristors occurs. The junction temperature is a function of the through current, but it is of no significance unless the thyristor is required to block (i.e., withstand full voltage). Blocking may be required when system voltage has returned below extreme values. Should high junction temperatures persist, continuous firing should be continued for a few cycles longer to allow the thyristors to cool although control will be temporarily lost. With this possibility in mind, the user may wish to specify a short-term, high-voltage situation, so that the SVC may give all possible assistance at times of system stress by specifying an “overload cycle,” such as Figure B.2, where overvoltages and duration periods are specified. The SVC should be able to recover normal control ability at the start of the continuous period shown.

Additional inductive overload of an SVC may be achieved by controlling the TCR at firing angles higher than 90° within the continuous operating range. If the voltage increases far above nominal voltage, a TCR operation at firing angles of 90° will then result in increased absorption capability for voltage reduction. The valve’s and reactor’s overload characteristics have to be considered for such an operating option. A disadvantage of this operation mode is the increase of generated harmonic currents in the continuous operating range resulting in increased costs for capacitor branches.

The overload characteristics of reactors, capacitors, and valves are shown in Figure B.3.

NOTE—The overload capabilities shown may not be summed up timewise contrary to the overload requirements shown in Figure B.2!


Figure B.2—Example for temporary overvoltage operating conditions

Typical values might be as follows:

1.8 per unit voltage, t1 = 3 cycles

1.4 per unit voltage, t2 = 12 cycles

1.25 per unit voltage, t3 =1 s

1.1 per unit voltage, t = continuous inductive

1.05 per unit voltage, t = continuous capacitive


Figure B.3—Example of overload characteristics of SVC components: (a) example of current overload capability for reactors; (b) example of voltage overload capability

for capacitors; and (c) example of current overload capability for high power thyristor valves


B.5.2 Control objectives—see 8.2

B.5.2.1 SVC functions with priority—see 8.2.1

Select from the menu of 8.2.1 the required functions with priority. Further functions may refer to the

following:

TSC or TCR switching logic

Automatic gain control (optimizer and supervisor)

Control stabilityof external devices

Sensitivity to distortion

The measuring transducer, which supplies the signal of the busbar voltage to be controlled, should be compatible with the performance (e.g., response time) required of the SVC. If separately supplied, the transducer should have an appropriate response (usually one cycle) to the total objective.

Normal control action should be based on measurements of the network voltage. Measurements may be done on a single-phase basis with additional balancing loops to minimize harmonics or by using a rectified mean of all the voltage signals. There is a choice between deliberately balancing each phase (with the disadvantage of responding to unbalance voltages) and responding to the phase-sequence components.

Further functions that can be specified are as follows:

It may be possible to restrict fault-clearance overvoltages.

The SVC should offer the most useful performance under switching and fault conditions. It should minimize energization transients when it is switched ON. To avoid postfault overvoltages, it should not connect capacitors (TSCs) nor be sized to counteract them by extending the inductive capability. During the recovery period immediately after a fault is cleared and while the SVC is resynchronizing its controls to the new network conditions, this recovery time should be a minimum, not exceeding two cycles.

Details should be provided of the synchronizing system to show how it remains functional for up to 1 s during a three-phase fault.

For control accuracy, see 9.3.

The user may also describe any special operating strategy for the potential SVC in the overall system operations of the user. Some concepts are described in B.1.


B.5.2.2 Response—see 8.2.2

The dynamic characteristic of the SVC control system is the response to a step change in the system voltage, so that the SVC remains within its controllable range. Such response time includes the delays in voltage measuring circuits.

An established method of verifying the speed of response of a closed-loop control system is to measure the time to reach 90% of the final value from an ordered small step-change (refer to Figure 4). The overshoot may be limited also. Demonstrat- ing this responseThis validation should be performed on a real-time simulator using the actual controller. A Thevenin network equivalent is difficultsufficient for an SVC, because the parameters are three rms phase quantities that do not change together. However, a this purpose. Several responses should be demonstrated at different gains, slopes, operating points, and short-circuit levels. A small step may beinjected into the control system as a test. If this test is required, it should be specified (small disturbance). The step shall force TSC switching (if applicable) and no limitations within controllable range.

Once at site and in the commissioning process, a step change to an element of an active power system for such verification may be obtained by switching OFF a shunt reactor or capacitor, or another SVC. Alternatively, a simulator or model test, using perhaps a voltage reference step applied to the real control system, is a solution at the factory test stage. The voltage reference step applied shall be representative for a system voltage change. In either case, a series of steps can be made from part reactive to part capacitive output, or vice versa, where different numbers of reactive elements are switched. In practice, there are delays of up to a cycle in measuring three-phase MVA output, and these delays should be taken into account.

Many factors affect the response time of an SVC, in particular, the gain, slope setting, system impedance, and the number of SVCs connected to the busbar. Increasing system impedance (that is, the system becomes weaker) leads to a faster response and ultimately instability. The user may be expected to specify a response time for the normal range of operating short-circuit level, defined in Clause 7. It is important also to define the weakest operating condition so that stability is maintained with a margin, and this condition will define the highest effective loop gain. The user should therefore avoid specifying an unnecessarily short response time for normal operating conditions.

Controls in which the gain setting is adaptive to system strength have been used. A normal range of short- circuit MVA of up to 3:1 should be handled by appropriate choice of the slope, and a response time of 50 ms is reasonable. Above that, i.e., at a much weaker short circuit, the gain is reduced and a response time of 100 ms is advised at a normal short-circuit level. Typically, it is important that the SVC size be specified at less than one third of minimum short-circuit power in order to avoid resonance issues.

The definition of response time may also be based on susceptance as long as the susceptance is based on measured quantities (voltage divided by current); that is, the susceptance signal within the voltage controller is not representative for evaluation of step response requirement.


B.5.3 Harmonic performance—see 8.3

B.5.3.1 General overview

If the SVC includes a TCR, then harmonic currents will be generated. A portion of these harmonic currents will flow into the connected transmission system and may cause difficulties to other equipmenthave negative impacts such as overheating of components or malfunction of control and protection systems. Therefore, a TCR type of the SVC system is usually provided with fixed (i.e., permanently connected) harmonic filters to limit the harmonic currents imposed on the transmission system. On the other hand However, TSC or TSR systems usually do not produce significant harmonic currents, and they may or may not incorporate harmonic filters. SVCs based on the presence of capacitive branches may impact existing distortion levels by (series) resonance effects with the supply system and will have an influence on the harmonic performance at the PCC. The harmonic performance specification has to be developed for these types of configurations to ensure that background levels are not increased beyond planning levels by virtue of resonance effects by indicating maximum permissible magnification (gain) factors.

The design of the harmonic filters and the selection of their components requires careful study, and these studies are described in Clause 11 of this guide. The purpose of Clause 11 is to describe the engineering considerations that go into specifying harmonic performance for a specific SVC system.

The TCR can be thought of as a current source for harmonic currents. These currents flow out of the TCR and divide between the harmonic filters and the transmission system in inverse proportion to the harmonic impedance of the filter and the transmission system. (Refer to 10.4 of Miller [B35] for a further explanation.)

Remark: In SVCs, the TCR is considered as an equivalent harmonic current source, whereas in voltage sourced converters (VSCs), the harmonic source has to be represented as a harmonic voltage source. The principles of performance/rating assessment remain the same.

It is possible for the sum of the harmonic current in the filter and the harmonic current in the transmission line to be greater than the harmonic current produced by the TCR. This phenomenon is known as current amplification and comes about through parallel resonance (otherwise known as anti-resonance) between the filter and the transmission system. (Refer to 5.2.2 of IEEE Std 519-1992 for a further explanation.)

The amount of harmonic currents that a given SVC can impose on the transmission system, without producing unacceptable consequences, will depend on several factors, such as the following:

Size (rating) of the SVC in relation to the capacity of the transmission system

Location and nature of other equipment on the transmission system that may incur with which the SVC may cause interference

Compliance with the specified harmonic performance limits at the PCC only or at all

nodes in the supply system (consideration of remote node effects/mutual impedance effects)

Harmonic impedance of the transmission system Presence of existing harmonics on the power system that will add to the harmonics produced


by the SVC

The determination of acceptable harmonic limits for the SVC system is best done using the methodology of IEEE Std 519-1992 or other national standards in other countries.

NOTE—Even though IEEE Std 519-1992 specifically disclaims applicability to HVDC and SVC systems, the principles described in that standard are suitable for use in specifying the harmonic performance of an SVC.

B.5.3.2 Basics for harmonic performance specification and calculation

Although the harmonic distortion produced by an SVC originates as a current source in the thyristor valves, the harmonic performance of the SVC can be specified in terms of either harmonic voltages or harmonic currents, or in terms of both at the point where the SVC is connected to the transmission system, the PCC, the harmonic voltage is related to the harmonic current by Ohm’s law. That is to say:

Vn Zen I n

where

Vn is the voltage at harmonic n at the PCC

6The numbers in brackets correspond to those in the bibliography in Annex A.

Zen is the harmonic impedance looking into the transmission system at the PCC In is the current injected into the system at harmonic n

Users should examine the system viewed from the proposed point of connection of the SVC or other points such as the PCC, for harmonic impedance (both present and predicted future). Various system conditions should be considered. Plotting the harmonic impedance depending on load and generation level, future system extension, system outage conditions, and so on. Impedance results should be provided in text files: f (Hz), R (Ohm), and X diagram (Ohm) with frequency steps not larger than 1 Hz. From all investigated system cases, R/X diagrams can be plotted for each harmonic frequency with a range chosen to be not less than ±5% of the respective harmonic (refer to Figure B.4). These R/X diagrams will reveal “search areas” (refer to Figure B.4) within which the impedance at each frequency can always be found resulting in worst-case harmonic distortion in the system.

Typically, the maximum value of ny might be in the range of 25 to 29 for TCR-based SVCs using a dedicated SVC transformer but may be chosen higher for direct connected SVCs or VSC-based reactive power controllers.

An example of the harmonic impedance sectors of Zen is given in Figure B.4. NOTES:

1—Each box refers to one frequency

2—Units are per unit resistance and reactance.


Although theoretically the system harmonic impedance values at frequencies above fundamental will lie within a circle on the R/X diagram Figure B.3, to specify that these values can lie anywhere tends of 25 to yield an expensive All studied system cases have to be within a chosen boundary that finally is used to calculate the harmonic distortion at the PCC for each frequency. The same area or an increased area may be used for filter rating calculations.

The system impedance values at harmonic frequencies may also be found in a single search area on a R/X diagram similar to Figure B.4, but using only one search area for all harmonics ny = 2 to the maximum ny specified may result in uneconomic filter design. It is preferable to define smaller areas for each frequency, and harmonic(or harmonic range) and the minimum values of resistance and impedance angle (CIGRE Guide 139 [B8]).

For an SVC connected to a tertiary winding of an existing transformer or when harmonic distortion requirements at remote buses apply, additional impedances have to be considered. The impedances to be calculated are effectively the voltages that appear at the bus of interest for 1 pu current injection at the SVC connection point. For the SVC connected to an existing tertiary winding, the mutual impedances from the tertiary to the primary (HV) and secondary (MV) terminals are needed. The self-impedance is the harmonic impedance seen from the tertiary winding of the transformer. For calculation of harmonic performance at remote buses, the mutual impedance between the points of connection and various remote buses is required. It is preferable that data is given in the form of tables with frequency, self-impedance, and mutual impedances for each system contingency.


Harmonic network impedances for HV and MV sides may, in the worst case, be used for harmonic distortion calculations at both buses for SVCs connected to a tertiary winding; that is, for each harmonic, the impedances within the two loci resulting in the highest voltage distortion may be identified and used for harmonic rating and performance calculations. The use of the previously mentioned self- and mutual impedances will eliminate the risk of overdesign of filters and thereby minimize the cost impact due to unlikely network configurations.

Harmonic distortion at remote buses, caused by the injected SVC current, may be higher than at the injection bus. In those cases, the mutual impedance data are extensive.

Figure B.5 shows the definition for self- and mutual impedances.

Figure B.5—Explanation of self- (Zself) and mutual impedances (Zmut) A current I1_ny injected at node 1 results in a voltage V1_ny at node 1 due to impedance Znet or Zself. A current I1_ny injected at node 1 results in a voltage V2_ny at node 2 due to impedance Z12 or Zmut:

The design of a harmonic filter involves a number of considerations, many of which are conflicting. In order to make the supplier aware of the requirements for a particular project, the filter specification should include the following:

a) The required harmonic performance for normal operation (8.3).

b) Any permissible deviation from the normal performance, which might be accepted under unusual circumstances or for a short time (e.g., possible changes from nominal values of frequency per Clause 7), which will change the tuning of the filter. (Relaxing the required filter performance under unusual or rare conditions may result in considerable cost saving in the filters.)

c) The temperature range (Clause 6) over which the filter should operate. (The capacitance of power capacitors changes slightly with temperature.)


d) The extent to which the filter should perform without one or more capacitor units or filter arms, provided that this condition is alarmed. Internal fused All types of capacitors, where used, should have an unbalance

or other protection to remove the bank if internal elements or external fuses have operatedfailed to the extent that further fuse operation or element failure could lead to damage or an undesired operational condition.

e) The presence of any existing harmonic distortion on the transmission system. The harmonic filter in the SVC will act as a “sink” that may attract any existing harmonics to the SVC. Therefore, these harmonics will impose additional duty on the filter and should be accounted for in the rating of filter components.

f) Values to be specified. Harmonics up to about the 50th harmonic may affect other power apparatus connected to the transmission system. Therefore, it is common to specify limits for the following:

1) Vn is the maximum voltage for any single harmonic below the 50th

2) In is the maximum current at any single harmonic below the 50th, 3) THD is the total harmonic distortion including all harmonics to the 50th

Although no general consensus exists yet for the limits and whether voltage or current distortion is preferable as a design point, IEEE Std 519-1992 presents several tentative suggestions. Alternative subclauses might be the following:

Alternative specification. The maximum voltage distortion at the kV bus should not

exceed % for any individual harmonic and should not exceed % for the rms sum of all the harmonics from the second to the 50th harmonic.

Individual voltage distortion is typically set between 1% and 3%. rms voltage distortion is typically set between 2% and 5%, although lower values may be used in other countries according to applicable national standards.

Alternative specification. The maximum current distortion kV bus in the

specified connection should not exceed % for any individual harmonic and should not exceed % for the rms sum of all the harmonics from the second to the 50th harmonic.

Individual current distortion is typically set between 2% and 8% (e.g., IEEE Std 519-1992). rms current distortion is typically set between 5% and 10%. Specify the base current for 100%.

Current distortion is typically only specified at locations where inductive coupling to other lines may occur.

For rating purposes, it is usually too rather conservative to define the whole of the voltage and current characteristic (refer to Figure 3, area EFJH) as continuous operating range; therefore the user should may define a more limited, practical operating range of the SVC within the characteristic, to be associated with the maximum harmonic stresses on the SVC components. For example, at points E (G) and F in Figure 3, the SVC is unlikely to be generating harmonics. By examining the expected use of the SVC (i.e., normal capacitive output and expected high-voltage reference Point K), it is possible to indicate the most severe continuous operating situation. If the highest capacitive output and highest voltage reference are selected for continuous filter component


ratings, higher costs should be expected than if the normal voltage reference line (line AB in Figure 2) is used and full output is not continuous.

A practice is to determine the rating of each SVC component from the application of the following two criteria:

Highest fundamental frequency stresses plus relevant (associated) harmonic stresses

Highest harmonic stresses plus relevant (associated) fundamental frequency stresses (the latter of which will be lower than in the previous item)

For both criteria listed previously, the effects of background harmonics as well as SVC generated harmonics need to be taken into account, noting that the contribution of background harmonics, especially at low orders, can predominate SVC contributions

B.5.3.3 Effect of background harmonics

As mentioned previously, in most systems, it is impossible to identify discrete major harmonic current sources that finally may be used for calculating additional stresses on the SVC components. A possible approach is to use harmonic voltages that are measured at the PCC over a sufficiently longer time to include effects from working days, holidays, changes in generation pattern, system outages, and so on, or other seasonal effects. Harmonics of order 2 to 21 may be analyzed. Such harmonic voltages may be used behind an impedance to consider effects on harmonic stresses for the SVC components. The maximum component stress can be found by searching for the worst-case resonance condition of system (refer to the impedance example of Figure B.4) and SVC operating configurations. NOTE 1—Special consideration has to be given to the minimum resistance of the harmonic system impedance presentation; it has to be a realistic value relevant to the harmonics under consideration.

NOTE 2—Simultaneous worst-case resonance conditions for all harmonics are not realistic to assume for final component rating.

NOTE 3—The values of system harmonic impedance and background distortion have to be self-consistent (i.e., it should be physically possible for them to occur simultaneously).

Figure B.6 illustrates the procedure on a single line diagram.


B.5.3.4 Modeling of background harmonics

Background harmonics may be modeled as a voltage source or as a current source

B.5.3.4.1 Background harmonics modeled as voltage source

The magnitude of background harmonic voltage source for each harmonic can be taken from either actual system measurements in various system operating conditions, possibly with an allowance for future growth, or from planning levels/compatibility levels. As discussed subsequently, this method has the disadvantage that the effects of resonance between the SVC and the system are neglected

B.5.5 Audible noise, see 8.5

It is helpful if the user makes available (or includes in the scope of supply) an audible noise survey of the situation typically found before the commissioned

B.5.3.4.1.1 Background harmonic voltage source connected directly

Figure B.7 shows a background harmonic voltage source directly connected to the SVC POC. The SVC impedance is composed from the transformer impedance (Ztrans) and the relevant LV branches that may be connected to the LV bus at different SVC operating conditions (Zsec). TCR branches typically may only affect the SVC impedance at very low frequencies. The current and voltage harmonics are calculated for each SVC component. The harmonic current into the SVC, generated from background harmonics, is calculated by:


Figure B.7—Equivalent circuit of SVC and a directly connected harmonic voltage

source The voltage of LV bus where the LV branches are connected will be calculated via:

and the corresponding current through each LV branch (1…n) in operation accordingly:

B.5.3.4.1.2 Background harmonic voltage source behind a network impedance

Figure B.8 shows a background harmonic voltage source connected to the SVC POC via a network impedance.


The harmonic voltage on the secondary side of the SVC is calculated as:

where Zsec is the SVC impedance seen from the secondary side of the transformer and ZSVC is the SVC impedance including the transformer reactance, calculated at every harmonic frequency of interest. After calculating the harmonic voltage at the SVC HV bus and the voltage Vsec, the currents/voltages on the SVC LV branches (1…n) in operation are calculated by:

The magnitude of the background-harmonic voltage source should be considered to vary with the value of the resistance of the source impedance in a manner shown in Figure B.9. Special consideration has to be taken for the resistance of the harmonic system to give reasonable magnitudes of the harmonic voltages at the point of connection.


B.5.3.4.2 Background harmonics modeled as current source

For some projects, the harmonic filter rating calculation considers background harmonics modeled as a current source. To use this information for filter ratings, the background harmonic model described in Figure B.10 may be used. The left figure shows the model that is used to derive a current source for each harmonic that gives a maximum harmonic voltage distortion at the point of connection equal to the specified background source.

The derived current sources are then used in the right model shown in Figure B.10 to calculate the background harmonic currents injected to the SVC together with the resulting component stresses (refer also to Figure B.4). It should be noted that Znet is the harmonic network impedance sectors that have to be provided in the specification.

Background levels in percentage of the system voltage may be taken from planning levels or from system measurements.


B.5.3.5 Aspects of the different models The different models have an effect on the results of harmonic calculation, as follows:

Using the model of Figure B.7 may result in nonrealistic low SVC component stresses because the

effect of the connected system is neglected.

Using the model of Figure B.8 or Figure B.10 may result in nonrealistic high SVC component stresses if properly damping especially of the system components is not considered. In both cases, in particular, proper damping at lower harmonics is required. Here, the frequency- dependent resistances of transformers, reactors, lines, and cables are important to establish the equivalent network impedance.

B.5.3.6 Additional information

In all harmonic calculations, distinguish between harmonic performance and filter component rating, as follows:

Calculating harmonic performance (Dn, THD, TIF, IT, etc.) should be based on harmonic

generation at normal system voltage. Calculation of SVC component rating should consider the whole system voltage operating range together with the corresponding SVC continuous operating range. Different ranges for system frequency and V2/V1, etc should be used.

For the THD, TIF, and IT calculation, a more simplistic approach could be taken by using a whole of maximum harmonic currents covering the whole operating range or several simultaneous harmonics currents at different operating points assuming resonance conditions between SVC and system at all harmonics is not realistic. Calculation of THD, TIF, and IT values could take the worst network impedance of two individual harmonics that contribute the most to these indices. For the other harmonics, the network could be seen as an opened circuit from the PCC for the THD and TIF and as a R//L for the IT calculation.

Background harmonic voltages should be based on rated voltage.

Only low-order background harmonics will make significant contributions to stresses on SVC components. Frequency dependence of the SVC will be typically inductive for harmonic numbers above 7; therefore, at increasing frequencies, the effect on the SVC will be decoupled from the system itself. Therefore, these contributions generally need only be considered for a limited number of harmonics.

Calculating TIF and IT performance, the weighting factor is important at higher harmonics.

Tolerances are generally neglected in stress calculations from background harmonics when system impedance effects are considered. In the case of using directly connected background harmonic voltage at the POC, all SVC component and system frequency tolerances should be considered.

The part of the third harmonic contribution from background harmonics, which is considered to have zero sequence character, is assumed to be trapped in the transformer delta (typically used) and will not be considered for rating of the SVC components.


It should be agreed between user and manufacturer whether it is permissible to assign the rated voltage (Un) of capacitors up to 10% below Um because certain international standards require capacitors to have up to a 10% prolonged overvoltage capability. However, the value of Un assessed from that assumption has to be at least equal to the maximum fundamental frequency voltage on the capacitor bank. If this is not the case, then the assigned Un should be the maximum fundamental frequency voltage. This approach is based on the SVC operating conditions where in certain operating ranges maximum fundamental voltage and harmonic voltages may not occur at the same time.

B.5.4 Telephone and radio interference—see 8.4

B.5.4.1 Limits for telephone interference—see 8.4.1

Although the harmonics produced by power-electronic switching are greatly reduced in magnitude as the frequency increases, any harmonics in the audible band are a concern because they may couple into the telephone system and cause interference. In general, the levels produced by an SVC are not significant. A current standard for limiting the potential for telephone interference is the “C-message” weighting factor curve established in IEEE Std 519-1992 or other weighting factors in national standards of other countries.

B.5.4.2 Limits for broadband interference—see 8.4.2

The potential for higher frequency emissions should be limited to avoid interference with any properly licensed or authorized radio, television, microwave, or other equipment in service. Typical guidelines are given in this annex. However, the user has to refer to local standards to determine the specific limits acceptable for their respective country. Calculations should be done at the project stage to find out what measures are required to meet the limit of radio interference during all possible operating conditions.

The broadband interference includes, but is not limited to, the following frequencies.

B.5.4.2.1 Radio interference (RI): AM band 540 to 1700 kHz; FM band 88 to 108 MHz

Because of the very fast switching action of a solid-state converter, the potential for directly radiated interference from the SVC does exist. However, actual radio interference problems from SVC installations have been extremely rare. Moreover, a utility type of SVC to which this guide applies will usually be part of an HV substation that has some level of corona discharge, particularly if the substation is a conventional air-insulated installation. Usually, the RI produced by the corona discharge from the HV equipment and bus will be greater than the RI produced by the SVC, thereby masking the SVC. Nevertheless, it is prudent to include an RI and television interference (TVI) limit in the SVC specification, typically set between 50 μV/m and 100 μV/m at a distance 500 m away from the SVC station perimeter.


B.5.4.2.2 PLC 14 to 500 kHz

The SVC should incorporate the features necessary to limit the carrier frequency noise levels due to the SVC system and related equipment to the following values:

30 to 100 kHz –10 dbm decreasing to –20 db 100 to 500 kHz –20 dbm

B.5.4.2.3 TVI 54 to 88 MHz, 174 to 216 MHz, 512 to 608 MHz, and 614 to 698 MHz

The SVC components and their layout should be designed such that there are no discharge sources from the SVC system and related equipment that could cause television interference.

B.5.4.2.4 Microwave interference 1 to 170 GHz

The selection of SVC technology and the type test reports of such technologies should be evaluated if such designs could form a source of noise, and if so, the design needs any necessary mitigation so that the signal-to-noise ratio in the voice frequency range on the microwave communication system is not affected.

B.5.4.2.5 Field testing and measurements for compliance with radio frequency and PLC emissions

Measurements should be performed before construction and after commissioning to document actual noise levels for the above four types of communication and frequency bands. Based on these two different measurements, SVC system contribution and compliance will be determined.

It is recommended that due to the banded nature of the measurements required for radiated interference, several instrumentation systems be configured to properly measure the frequencies of interest. Due to the significant directional selectivity of the measurement systems at the frequencies above 450 MHz, a range of antennas will be required. The following list is appropriate for meeting the requirements within the United States and Canada, which specifies the maximum radiated level of 16 dB above 1 μV/m. Other standards may apply outside the United States. It is important to note that the measurement system and antenna selection will be frequency dependent. When investigating the different frequency bands, the following antennae may be chosen:

AM broadcast band (540 kHz to 1700 kHz): directional loop antenna Amateur radio bands (160, 80, 40, 20, 10, 6, and 2 m, as well as 70 cm bands)/marine

telephone: directional loop/log periodic antenna

Very high frequency television and FM radio bands: log periodic antenna

Operational fixed microwave or common carrier microwave bands: frequency-specific broadband feed horns and 1 m parabolic antenna

Cellular telephone and other land mobile service bands: log periodic antenna

Ultra-high-frequency television: log periodic antenna


To characterize the radio frequency interference measurements properly, the following series of steps is recommended in the preconstruction and final acceptance testing periods:

Establish three baseline measure points preferably on the utilities property or right of way with a

semipermanent marker.

Take the measurements of interest in the bands noted previously before significant construction begins from each point including frequency scans across the existing substation installation (if the SVC is being established to an existing substation). This set of baseline measurements should take particular note of high emissions in frequency and direction from the reference sites identified previously.

Take a second set of measurements over a significant range of TCR firing angle ranges after

construction is complete from the same measurement locations as noted previously.

Any significant high measurements should be noted and mitigation if required be completed; also, any remeasurements should be taken and recorded in the commissioning record.

Power line carrier noise measurements should be made using commercially available spectrum analyzers. Appropriate bandwidth and impedance termination will be made.

Radio signal strength should be measured using instruments with average detectors. Radio noise measurement should be in quasi-peak (QP) levels for AM band and peak levels for FM band. Measurements should include at least three complete frequencies scanning at selected locations around the perimeter of the property line. The ambient levels should include all radiated noise from the associated transmission line, structures, and nearby equipment.

Radio noise levels should be measured with an instrument complying with ANSI C63.2-2009 [B2] (1 by 160 ms charge and discharge times, 9 kHz bandwidth). Measurements made with instruments having a bandwidth other than 9 kHz should be corrected to 9 kHz. Measurements may be made with instruments having QP charge and discharge time constants of 1 ms and 600 ms, and a bandwidth of 5 kHz, if those instruments comply with earlier issues of ANSI C63.2-2009. If such instruments are used, the readings should be corrected to a bandwidth of 9 kHz.

Television signal strength and noise measurements will be in accordance with IEEE Std 430TM-1986 [B25] over the range of 30 MHz to 1000 MHz. ANSI C63.14-2009 [B3] defines the instruments to be used. The measuring antenna should be at a height of 30 ft above ground. All data will be reported at a nominal bandwidth of 120 kHz.

B.5.5 Audible noise—see 8.5

Audible noise limits should be specified at various key locations both outside and inside the SVC control building. An example of possible measurement/specification locations is given in Table B.1.


Table B.1—Example possible measurement/specification locations

1 Station fence/property line 2 Within pump equipment area 3 At a defined distance outside of compressor area enclosure(s) 4 At a defined distance outside of mechanical equipment areas 5 Maintenance workshop 6 Control rooms 7 Relay rooms 8 Other accessible rooms

B.5.6 Loss evaluation—see 8.6 and item c) in 11.1 Depending on the SVC’s main control objective, an SVC will typically operate in various operating ranges depending on time. One hundred percent time is the maximum operating time per year. Figure B.11 shows an example for SVCs used for stability purposes and system voltage control.

The losses in the different operating ranges should be averaged and evaluated by the operating time. A summary of the examples above is given in Table B.2.


Table B.2—Example of loss evaluation for SVC type A and type B

SVC A – QSVC % 100 …. 5 cap

5 ……. 5 cap .. ind

5 …. 50 ind

— —

Operating time %

7.5

90

2.5

—

—

= 100% SVC B – QSVC % 100 …. 60

cap 60 …. 20

cap 20 …. 15 cap … ind

15 …. 25ind

25 ….50 ind

Operating time %

10

20

55

10

5

= 100% QSVC % Range 1

cap Range 2

cap Range 3

cap … indRange n

ind

— Pv (range) Average

Pv1

Pv2

Pv3

Pvn

Operating time pu

t1

t2

t3

tn

—

= 1.0 pu

Pveval Pv1 t1 Pv 2 t2 Pv 3 t3 ..... Pvn tn n

Pveval (Pvi ti )

i 1

The cost of losses will be calculated by the following:

Cost of losses = Pveval (kW) × Cl ($/kW)

The factor Cl depends on the purchaser’s experience about the cost of losses in his system. The factor Cl can include loss cost figures for 1 year of operation or can be a value that is capitalized over the lifetime of the SVC.

The losses of a static compensator are an important consideration because they can form a major part of the operating cost. This cost should be evaluated against the capital cost of the equipment. Loss evaluation has an important influence on the SVC design. The evaluation procedure has three steps, as follows:

a) The user should define the expected normal operating points or operating ranges (in

megavar output) of the compensator and the capitalized cost of losses (cost per kilowatt). Several such operating ranges will exist depending on the control purpose of the SVC installation. The capitalized cost of losses for each operating range should be weighted according to the percentage of time that the SVC is expected to operate the averaged output in this range. It should be noted that such weights will be different from those used in a system transformer loss evaluation because SVC output is not likely to be proportional to load current.

b) Each bidder calculates and quotes the kilowatt losses in each operating range. The losses will include the electrical power used for pumps, fans, auxiliaries, and so on. Multiplying each calculated loss by the specified cost per kilowatt sums up to the total evaluated cost of losses, which will be added to the equipment price to compare bids. In some instances, the total evaluated cost of losses has had the same order of magnitude as the equipment price. The bidder will normally choose a design that minimizes the total of the equipment cost and the evaluated cost of losses.


c) During project construction, loss measurements are made at factory testing of the SVC components and for auxiliary power requirements at site during commissioning. The bid calculations have to be reworked on those loss measurements. Adjustments to the contract price may be made to reflect a recalculated loss different from that quoted in the bid.

It is widely agreed that measurement of the actual losses of an operating SVC is not practical. Not only are there difficulties in measuring a small quantity in relation to main circuit currents, but also measuring heat loss at nominal ambient temperature, harmonic impedance, and so on, and finding suitable steady operating conditions either at factory or at site present difficulties. Calculation is, therefore, necessary. Annex C is a recommended procedure to calculate valve losses. For all other SVC components, the loss measurements from factory tests and site measurement can be used.

All losses should be determined to a specific condition (e.g., temperature and network operating conditions that should include the system voltage, reference setting, and slope of the SVC). At each operating point, all elements should be considered in the loss calculation. Thyristor valves, energized but with zero megavar output, still generate losses and should be included. Zero SVC output may not necessarily coincide with zero transformer current. The total SVC losses are normally between 0.5% and 0.8% of the megavar rating of the SVC. Losses caused by the flow of harmonic currents in the filter components should be excluded from this calculation because they represent a small percentage of the total.

B.5.6.1 Thyristor valves—see 8.6.1

Refer to Annex C.

B.5.6.2 Transformer losses—see 8.6.2

The transformer current may not necessarily be zero when the SVC output is zero.

This procedure ignores the losses in a transformer due to harmonic currents (although the transformer design should take them into account). Many SVC designs that use a TCR include a filter on the same busbar, and the filter reduces the harmonic current in the transformer. In other cases, users may wish to specify a calculation of loss due to harmonic currents such as used in HVDC convertors (refer to Forrest [B12] and IEEE Std 1158TM-1991 [B28]).

The loss calculation reflects test measurements that can be used to verify it. The total loss at full load is the sum of core, stray, and copper losses. The core losses vary according to the operating voltage of the transformer at the output in question. As an approximation, the nominal-voltage value may be used throughout. The copper loss and stray loss together are calculated from the fundamental current and measured resistance at that frequency, adjusted for conductor temperature. Stray loss is thus modeled by a resistance. The specification requires an estimate of these losses to be used in the evaluation procedure described above and to be verified later from factory tests.


B.5.6.3 Reactor losses—see 8.6.3

The reactor losses are calculated from the rms fundamental phase current I:

Preac 3 Rreac I2

Rreac is the fundamental frequency resistance. The reactor resistance values should be verified from the test report for the reactors. The tests of quality factor Q should be made with as many connections, clamps, shields, and so on as possible in position.

This calculation applies to TSC and filter reactors, MSRs, TCR, and TSRs. B.5.6.4 Capacitor bank losses (TSC, MSC, and filters)—see 8.6.4

In the test reports for each capacitor unit, the dissipation factors (tan delta) are given. The values received after the Thermal Stability Test should be used. An average value for all capacitor units is used to calculate the capacitor bank losses. The formula used is:

Pcap Qcap DF

where

Qcap is the actual capacitor kvar DF is the capacitor dissipation factor at fundamental frequency, which should include the

losses in capacitor fuses

B.5.6.5 Resistor losses—see 8.6.5

Resistors are used in HP, double-tuned filters, and triple-tuned filters:

Pres 3 Rres I2

where

Rres is the resistor resistance I is the fundamental rms phase current through the resistor

NOTE—For the rating of the resistor, harmonic stresses have to be included in addition.

B.5.6.6 Auxiliary system power—see 8.6.6

The power used by the auxiliary systems for pumps, fans, and building cooling and heating systems together with the power needed by each thyristor level is deduced for each specified


condition of the ambient temperature and reactive power flow. Nominal auxiliary supply voltage is assumed.

B.5.7 SVC availability and reliability—see 8.7

B.5.7.1 Definitions—see 8.7.1

Alternative definitions are possible. Travel time (within a reasonable maximum) can be deducted from outage time.

B.5.7.2 Required availability and reliability—see 8.7.2

A typical figure for SVC forced outage availability is 98%, and the number of events is five per annum. It is reasonable to specify that such levels for an SVC should be guaranteed, provided that the supplier’s recommended spares holding is kept at the site, and the preventive maintenance procedure is followed. It may be necessary to adapt the wording to the calendar year to suit availability records.

Usual guarantee periods are 2 years. Usual maintenance intervals are 12 months.

B.6 Main components—required functions and features—see Clause 9

The specification subclauses concerned with thyristor valves and other main components are intended to be functional and general (i.e., not prescribing the precise form, rating, or quantity of the components, but allowing the bidder freedom to propose an optimum solution). Such an approach should encourage innovation and the most cost-effective solution within the user’s requirements, without compromising the required reliability or established standards of control, protection, ease of maintenance, and so on.

B.6.1 Thyristor valves—see 9.1

The purpose of the thyristor valves is to control (TCR) or switch (TSR) the ac current in a reactor bank or to switch ON and OFF a capacitor bank (TSC). TCR valves control the phase current to provide variable amounts of ac current to the reactor bank, thereby controlling variable inductive vars. TSR valves switch reactor banks in and out to provide blocks of reactive power. TSC valves switch the ac current by allowing either full or zero conduction of current, thereby providing controlled step changes in capacitive vars.

Generally, a single thyristor redundant per phase is sufficient. Small industrial SVCs may have only a single thyristor per phase. In such a case, spare valves are more useful if high availability is needed.

The bidder may be asked to provide a data sheet of ratings of offered thyristors.


B.6.1.1 Valve protection—see 9.1.5

The individual emergency firing protection of TCR valves can be coordinated with the valve surge arrester. If so, the latter should operate first. Light-triggered thyristors and electrically triggered thyristors should have built-in overvoltage protection, or the bidder should explain how the consequences of a faulted light source or light guide are handled.

B.6.2 Thyristor valve cooling system—see 9.2

The purpose of the thyristor-valve cooling system is to remove the heat produced by the thyristor valve and to eject it to the environment. Generally, two types of thyristor cooling systems are possible: water cooled or air cooled. In either case, the cooling system should be completely furnished with all necessary interconnecting piping, ductwork, circulating pumps, blowers, heaters, make-up reservoirs, heat exchangers, filters, water treatment plant (if required), instrumentation, automatic controls, alarms, control power systems, and other necessary equipment.

B.6.2.1 Liquid cooling (if applicable)—see 9.2.1

The heat transfer from the closed liquid system to the ambient air should take place in a water-to-air or water-to-water heat exchanger as follows:

a) One pump should normally operate and a redundant pump should be standing by. If a pump

failure occurs, the second pump should automatically switch in without shutting down the equipment. The pump should change over automatically every month or so to cycle the second pump. A set of alarms should be displayed at the appropriate local and remote control cabinets to alert the operator that a pump problem exists.

The cooling system should be constructed to permit work on a defective pump unit without shutting down the SVC.

b) The purification system should be designed to maintain the resistivity of the water above 1 M /cm. A resistivity transducer located in the outgoing water from the deionizer should detect the depletion of the material. The second purifying loop will continue to operate in the presence of a primary-loop alarm until its deionizer is depleted.

c) If water–water exchangers are used, the secondary water that is passed through to remove heat should be suitably treated for disposal into the environment. Filters and deionizer material should be designed to allow replacements in a relatively short time without shutting down of the cooling unit. (Normal replacement should not be required more than once every 12 months.)

B.6.2.2 Air cooling (if applicable)—see 9.2.2

Either a nonrecirculating (i.e., once through) or a recirculating air system may be provided, depending on the requirement of the thyristor selected by the supplier and on specific site conditions. A once-through air system is one in which outside air is drawn through a filter and then through the thyristor valve, and the heated air is then exhausted to the outside. A recirculated air system is one in which the air is recirculated within the SVC building, and the heated air is cooled with a heat exchanger.


Required design functions and features include the following:

a) Dual blowers with one blower normally operating and the second standing by. If a blower

failure occurs, the second blower should automatically switch in without shutting down the equipment; and an alarm should be displayed at the control cabinets to alert the operator that a blower problem exists.

The cooling system should be constructed to permit work on the defective unit without shutting down the system.

b) Air filtering system (nonrecirculated systems). A warning alarm should register at the control

cabinet when filter replacement is needed. The filter should be designed so that replacement can take place without outage of the SVC, and under normal conditions, it should not be required more than once every 6 months.

c) Monitoring. Sufficient gauges and indicators should indicate the status of any part of the unit for both normal operations and maintenance.

B.6.3 Control equipment and operator interface—see 9.3

Overall accuracy of the controlled variables can typically be ±1% for voltage and ±5% for current.

The primary purpose of the control of the SVC is to control system voltage in response to measured system variables, auxiliary inputs for supplementary control, or operator inputs. It is recommended that the voltage and current measurements are included in the SVC scope of supply to ensure that they are compatible for the required response of controls.

SVC control contains the following:

a) Alternative modes of operation, as required, including a manual mode for site testing and

emergency shutdown by operator.

b) Voltage, current, and reactive power measurement.

c) SVC control by generating of the appropriate firing pulses to the thyristor valves. d) Orderly

start-up and shutdown sequencing.

e) Monitoring and protecting the control itself in progress and the components it controls. The controls may also contain one or more of the following:

f) Automatic return to manual mode of operation at the most recent voltage setting on the loss

of input voltage measurement signal.

g) Automatic voltage control, operative during start-up to prevent unnecessary switching of the reactive elements.

h) Self-check facility that at regular intervals operates equipment to verify its correct

operation.


i) Supplementary control modules for damping and var control.

j) Control system damping with gain supervisor and gain optimizer. On gain supervision, details should be given especially on the onset of instability. The criteria for detection of instability are as follows:

1) Frequency range of the oscillation

2) Amplitude of the oscillation

3) Number of consecutive oscillations above an adjustable threshold

This function should also include an adjustable emergency gain. The user should indicate the type of operator interface that is required, such as follows:

Computer-screen mimic

Mosaic panel (being less used)

Additional to an existing substation’s controls The choice of interface will be determined by whether maintenance staff is present at the site continuously and by the expected location of staff for normal operation and commissioning.

The different level of permission that it requires (operator, maintenance, and so on) and the minimum amount of information that should be displayed should be specified.

The possible requirements of control system construction are as follows:

General construction. The control system components should be mounted in free-standing, indoor, metal-clad cabinets with appropriate seismic rating, where necessary.

Operating environment. Control equipment should be designed to operate properly at the expected maximum allowable ambient indoor air temperature of °C. Supplemental cooling may be provided.

Circuitry. Printed circuit cards should have built-in test points and indicating lights to facilitate testing and maintenance or, if microprocessor based, should have some form of self-checking and fault diagnosis, to be described by the bidder.

Interference tests. The controls should be tested to operate in the environment of ac substations, and suitable SWC (refer to IEEE Std C37.90TM) tests should be carried out or proof of previous testing provided.

B.6.4 Monitoring and protection—see 9.4

B.6.4.1 Protection—see 9.4.2

In addition to the protective features provided as part of the thyristor valves and control, an independent protection system may be provided to protect the compensator components against all abnormal operating conditions that may occur.


Table B.3 is taken from the IEEE/PES PSRC Working Group report [B23].

Table B.3—Overview of suggested SVC protection methods

Protection zone Protection device

Protection function

Notes

87 Differential 50/51 Overcurrent

63/49/71 Gas pressure/temperature/

Low-level oil

Transformer

51N Ground overcurrent 87 Differential 50/51 Overcurrent 59 ph-ph Overvoltage 59G Overvoltage (open corner delta) Ground faults

Low voltage bus

51N Ground overcurrent Used with grounding transformer

60C

Unbalance Cross-connected unbalance

measurement 87 Differential

50/51

Overcurrent Branch faults or limiting reactor

overloads 46 Negative phase sequence Unbalance 60 Zero-phase sequence Unbalance in lieu of 46

59

Overload Capacitor overvoltage using

current measurement

TSC

50N Ground overcurrent Branch faults 87 Differential 50/51 Overcurrent 49 Overload Reactor thermal overload 46 Negative phase sequence Reactor branch unbalance 60 Zero phase sequence Reactor branch unbalance

TCR/TSR

50N Ground overcurrent Branch faults

Overvoltage Arresters across each valve for TSC and break-over diodes for TCR/TSR

Overcurrent Conventional overcurrent or

overload provided in the controls Thyristor failure Monitor thyristors

Thyristor valves in TCR/TSR/TSC

Thermal model

59N Neutral voltage shift Detect failed cans or reactor

60C

Unbalance Detect failed cans via cross

connection


50/51 Overcurrent 59 Overvoltage 87 Differential Filter differential 50/51N Ground overcurrent Ground fault detection

Temperature Alarm and trip for coolant

temperature Flow Alarm and trip for coolant flow

Resistivity Alarm and trip for coolant resistivity

Leakage Loss of fluid

Cooling

Transfer failure or power loss

B.6.5 Reactors—see 9.5

The purpose of the main shunt reactors is to provide the required lagging var supply.

There is considerable debate regarding the acceptable level of magnetic fields that will not cause adverse effects on personnel. The presentcurrent recommendation by the National Radiological Protection Board (of the United Kingdom) is that personnel access should be avoided where fields exceed 1.0 mT. The user should take into account developments in public knowledge of the effects and any relevant legislation.

Design requirements for reactors should include the following:

Each phase reactor may be divided into two reactors, one on each side of the thyristor valve

to limit short-circuit currents resulting when one reactor is shorted or a ground fault occurs.

he user may attach a standard specification.

Supporting structural steel work, including foundations, and fences should be designed to minimize currents induced by the magnetic fields of the reactor.

The purpose of the filter reactors (if required) is to tune the capacitor banks to provide

the necessary reduction of harmonics. Subclauses 9.5 and B.6.5 apply to TSC reactors also, if used.

B.6.6 Capacitor banks—see 9.6

The purpose of the capacitor bank(s) is to provide the required leading var supply and to provide sufficient reduction of harmonic voltages and currents that may be generated by the SVC system. The banks (e.g., shunt capacitors and filter banks) should be designed to avoid resonance with the ac power system regardless of system configuration. Shunt capacitor banks usually include a series reactor for in-rush current limitation.


B.6.7 Power transformers—see 9.7

The purpose of the step-down power transformer (where applicable) is to couple the SVC components to the HV transmission system. Some SVCs may not require step-up transformers because a connection point at a suitable voltage (not usually above 36 kV) exists.

The power transformer is a standard transformer. The design of the transformer should be either three single-phase or one three-phase. Detailed transformer specifications may be included as an attachment.

B.6.7.1 Maximum flux density—see 9.7

Noise, core losses, and harmonic currents increase as the flux level in the transformer core approaches its saturation value.

The saturation flux density is the interClause of the flux density axis and the asymptote of the flux-current characteristic in the saturated region (having a slope equal to the air core reactance). As a general rule, the saturation flux density of the transformer should be at least 5% above the expected highest operating flux density to take into account frequency variation and other effects. The pattern of operation may make high flux density rare, and the user may define some operating condition other than maximum secondary voltage at which this margin should be satisfied. The maximum flux density depends on the primary leakage reactance of the transformer. For example, in a case considering a maximum capacitive output of 150 Mvar at 1.1 per unit (current of 0.91 per unit/150 MVA) and assuming a 15% leakage reactance on the primary side, the minimum voltage at which the transformer saturates is calculated:

1.05 × ( 1.1 + 0.15 × 0.91) = 1.30 per unit

B.6.8 Grounding and disconnect switches—see 9.8 The SVC is made up of several major components. As a minimum, the SVC should have a means of being visibly disconnected and grounded from the power system for maintenance or repair. A manual disconnectswitch or a removable, metal-clad circuit breaker can provide this function. Grounding devices or provisions for grounding should be provided.

Each of the following major components may be visibly disconnected (e.g., by a switch or a removable link) and grounded, depending on the availability requirements and whether the policy is to maintain a component of the SVC while the other components continue to operate: TCR, TSR, TSC, MSR, MSC, and filter banks.

Tests should be specified in accordance with the latest revision of IEEE or IEC standards for disconnect switches.


B.6.9 Auxiliary power supplies—see 9.9

The user may modify the requirements if an existing power supply is available at site and adequate for the SVC.

B.7 Spares—see Clause 10

A number of approaches to this question exist, and the choice of a particular strategy for a given project is a matter of engineering judgment and part of the overall SVC planning, design, and specification. The main considerations are as follows:

a) The criticality of the SVC to the overall transmission system. Clearly an SVC that is

essential to a major portion of the transmission grid cannot be allowed to be out of service for lack of parts. Therefore, a generous allotment of spare parts should be provided.

b) The criticality of each component in the SVC. The different components to the operation of the SVC vary in importance:

1) Category A. Due to economic constraints, some costly components may not have

a spare available. Furthermore, such equipment may have long lead times if a replacement were to be needed. In some cases, it may be prudent to provide a spare despite the cost. (Examples are step-down transformers, shunt reactors, and filters.) Another approach, in the case of a transformer, would be to select the voltage ratio to be the same as that already in use elsewhere on the utility system, where a spare transformer may be available. Another approach is to use single-phase transformers with one spare.

2) Category B. Operation with a major element out of service is often possible.

3) Category C. Some SVC components are usually provided with back-up devices or equipments, so that the first failure will not cause an SVC outage. These “in-place spares” should be considered when deciding on the overall spare parts strategy. (Examples are redundant thyristors, back-up pumps, and redundant coolers.)

4) Category D. The failure of some components will not produce an immediate SVC outage. Thus, it may be reasonable to limit the spares of these equipments if replacements can be obtained quickly. (Examples are building service equipments, fault recording equipment, and supervisory equipment.)

The strategy for some SVC installations may call for an on-site spare for category A parts and an on-site spare for all category B or C parts that are not immediately available from other sources. Other strategies may omit spares for all categories for economic reasons. Any parts that are not readily available through normal commercial channels, or whose manufacture is likely to be discontinued during the life of the SVC, should be included in the spares inventory.

c) The likelihood of failure for each component. Today, the failure rates of most electrical

components are known, at least approximately. Thus, it is possible to make a quantitative judgment of the likelihood that a particular device will need to be replaced.


d) The availability of a spare device through normal channels. For example, many components in an SVC have other uses as well, so they are available commercially or may even be kept in a central warehouse by the user. If so, there is less need to provide spares specific to the SVC.

e) The uniqueness of the spare devices. The spare devices that are unique to the SVC are best stored on site. Principally, this strategy refers to components for the thyristor valves and SVC controls. Storage on site ensures that the allows for the devices to be immediately on hand when needed, without the delay needed to draw them from a central stocking area. Therefore, a suitable storage area should be included.

B.8 Engineering studies—see Clause 11

Typically, load flow, stability, and voltage control studies including, where necessary, power oscillation damping studies, are done by the user as part of preparing the specification for the transmission system of concern. Different applicable system conditions are considered to determine the optimal location and size of the SVC. The results of these studies are then reflected in the SVC specification in terms of rating and control requirements. In addition, system harmonic impedance calculations and/or measurements for all practical system conditions are often performed, including an investigation of the potential for magnification of harmonic voltages elsewhere in the system. The results are then presented in the SVC specification, for example, in the form of the impedance loci (Figure B.4). This information is important for any SVC harmonic filter design.

The user may wish to defer some of these studies and to add them to the scope of supply as listed in Clause 11.

In the following paragraphs, studies and necessary input data and modeling are described.

Load flow studies

Objective Determine Current and voltage distribution

Active and reactive power flow Owner-

supplied data Power flow database, contingency list, possible system configuration including changes due to future system stages and emergency conditions (high/low load), system component ratings

Target Check System component stresses below ratings Voltage profile within permissible range

Find out Weak system conditions Model Single-phase fundamental frequency representation for balanced,

three-phase or component systems for unbalanced conditions

Fault level studies

Objective Determine Maximum and minimum short-circuit currents for single-phase, phase-to- phase, and three-phase faults

Owner- supplied data

Short-circuit database, contingency list, clearing times, possible system configurations according to critical operating conditions (high/low load, network stages, etc.)

Target Find out Thermal and dynamic design parameters of station and switchgear setting values for protection devices, interference on other systems, treatment of neutral point connection


Model Single-phase fundamental frequency representation for balanced, three-phase, or component systems for unbalanced conditions

Stability studies

Objective Determine System performance during and after system fault conditions


Powerflow database with compatible dynamic data set, contingency list, clearing times, possible system configurations regarding outages, emergency cases, and protection actions

Target Evaluate Effects on system, power plants, generator controls, and protection devices Find out Transient stability limit and system recovery

Determine Measures for improvement to be regarded in system planning, operating strategies, modifications of control, and protection

Model Differential and algebraic equations in time domain studies, use of eigenvalue analysis for small pertubation modes including relevant controls and mechanics depending on required details, reduced equivalent network

Transient studies

Objective Determine Short-time stresses of system components (overvoltages, overcurrents, and related waveshapes)


Electrogeometric configuration/characteristics of transmission lines, possible system configurations, transient behaviour of components (saturation, capacitive coupling etc.) involved control and fast protection

Target Determine Component stresses versus rating, insulation coordination, maloperation of measurement systems, and control and protection systems

Optimise Control structures and protection coordination Model Detailed three-phase and components representation including major

control and main protection

Harmonic studies (System performance and component rating)

Objective Determine Distortion levels at PCC Voltage and current stresses of filter components

Owner- and subsupplier- supplied data

Harmonic sources—type, magnitude Harmonic system impedances Filter component properties Detuning effects of system and filter components for performance and rating purposes

Target Calculate Distortion levels at PCC Filter design Capacitor voltages and reactor currents

Determine Distortion levels below permissible values Maximum operating voltages and currents of all components for rating purposes

Model Single-phase representation Modelling of components according frequency-dependent parameters Harmonic equivalent impedance area


Harmonic system impedance study

Objective Determine System impedance as seen from the POC of the SVC Mutual impedance between POC and remote buses


Power flow data base, contingency list, possible system configuration including changes due to future system stages and emergency conditions (high/low load), system component ratings

Target Calculate Self and mutual impedances related to the POC of the SVC Impedance results should be provided in text files: f (Hz), R (Ohm), X (Ohm) with frequency steps not larger than 1 Hz

Determine Plot R/X diagrams for different frequencies or frequency ranges Create search areas for use in harmonic calculations

Model Single-phase representation Modeling of components according frequency-dependent parameters

B.9 Tests—see Clause 12

SVC tests to be specified include factory tests, that is, production tests of all components and field (site) tests of components, subsystems, and the complete SVC.

IEEE Std 1303 should be used when specifying SVC field tests. “Mobile” SVCs, which are designed for service in more than one location, may allow for some subsystem tests, now considered field tests, to be done at factory rather than at site in the future. This trend will help reduce commissioning cost, at least for smaller SVCs. The user may also consider staged fault tests.

B.9.1 Factory tests of valves—see 12.1

Factory (type and production) testing of the major components of the SVC, to be performed off site (i.e., at the component factories or test facilities) should be specified per applicable standards as available. Preference between standards and user-specific requirements should be defined. Table B.4 lists the component standards that apply.

Table B.4—List of component standards (informative)

Component

IEEE standards collections Standards collections of other organizations

Transformer IEEE Std C57.12.80TM-2002 [B30] IEC 60076-1-04: 2000:2008 [B14]

Circuit breaker ANSI C37.06 -2000 [B1] IEC 60056-03: 1987IEC 62271-100:2008 [B22]

Reactor IEEE Std C57.16TM-1996 [B31] IEC 60289-05: 1988IEC 60076-6:2007 [B15]

Capacitor 1992IEEE Std 18TM -2002 [B25] IEC 61070-11: 1991IEC 60871-1:2005 [B18]

Arrester IEEE Std C62.22TM -2009 [B34] IEC 60099-1996 [B16]

Protection relays IEEE Std C37.90.1TM-2002 [B29] IEC 60255-22-4:2008 [B17] IEC

60255-20-01: 1984

Thyristor valves IEEE Std 857TM-1996 [B27] IEC 61954-2011 IEC 61956-09: 1999


B.9.2 Factory tests of controls—see 12.2

Special function tests may be requested to confirm the adequacy of the control system for the application at hand. Analog transient network analyzers or digital simulators are typically used for these tests. Often, these function tests are also checked against digital simulations performed as part of the SVC control development and design. Development and function testing of the (digital) controls may thus be linked closely with each other or by one process. In any case, a list of control function tests is an important part of any SVC specification, and the user may wish to make specific additions to this subclause. For interference testing, the IEC 61000-4-1:2006 [B19] series provides similar test procedures.

B.10 Documentation—see Clause 13

The following documentation is typically produced by the SVC supplier and should be specified as deliverables under the contract:

Technical reports

Equipment specifications

Quality assurance documentation

Equipment test reports

One-line drawings, as built

Three-line drawings, as built

Control elementary drawings

Plan and profile drawings, as built

Civil drawings, as built

Mechanical drawings, as built

Architectural drawings, as built

Operator manuals

Equipment maintenance repair manuals

Software and operating system manuals

If computer models of the SVC are required for power system simulation, they should be specified here.

B.11 Training—see Clause 14

The effective use and reliable operation of a static compensator will depend on the people responsible for its operation and maintenance. Their initial training will normally be the responsibility of the supplier within the supply contract, and their continued training updates and the training of new staff will be the responsibility of the user.


Normally, it should be expected that prior to this training the site staff responsible for operation and maintenance will be well versed in the normal practices of an ac station, but it will not be experienced in power electronic equipment. The specification chapters should be prepared based on this premise.

The user should consider how continued updates of staff and training of new staff should be handled after the supply contract is concluded. Preparation of a course video is possible, but it should receive specific budgeting and professional attention independent of the supply contract. Amateur hand-held videos, taken from the back of the room during training course lectures, have not been shown to give useful results.

In particular, the user should allow staff to participate in site installation and commissioning of equipment. This opportunity is a unique and valuable way to learn about the equipment and to have access before energization. The training course should be completed prior to this stage of a project.

B.12 Balance of plant—see Clause 15

Several features tend to be common to most installations, whether fixed or relocatable:

The SVC is frequently located in, or as an extension of, a substation.

The thyristor valves, valve auxiliary equipment, and SVC controls will be located in a custom-

designed building.

The other apparatus (e.g., reactors, capacitors, HV circuit breakers, disconnect and ground switches, arresters, and bus work) will be conventional.

The basic construction techniques adopted by the user for conventional HV substations will be

suitable for the SVC installation.

The few cases where special measures are required for the SVC are in the area of the thyristor valve, valve cooling, controls, and grounding. The supplier should describe what is required for its particular system.

B.12.1 Buildings and structures—see 15.1

A wide variety of building types and styles have been successfully used in SVC installations, ranging from the most simple preengineered industrial building to masonry buildings with full architectural treatment. In general, each of these approaches has been successful when carefully engineered, and the choice is a matter of the user’s preference (and budget). A few specific aspects should be considered, however:

Shielding. The switching of the thyristor valves has the potential for producing

electromagnetic interference. Therefore, the supplier should be consulted in case any specific shielding concerns exist regarding the valve hall or control room.

Circuit security. A number of sensitive circuits are likely to exist between the SVC controls and other apparatus, such as CT and PTVT, and will require shielding or special circuit routing away from sources of electrical noise.


Health hazard. The inquiry should include any particular requirements regarding health hazards, taking into account local legislation. If risk assessment is necessary, then it should be specified here.

Building services. Although the primary purpose of the SVC building is to house the SVC equipment, equipment should be maintained periodically. Personnel are present, even occasionally in an unmanned station. The level of building services should be integral to the SVC design regarding the building environment, particularly for the extremes of operating temperatures that can be permitted and the level of “creature comforts” that will promote efficient maintenance work (e.g., sanitation, heating, lighting, ventilation, and air conditioning).

B.12.1.1 Fire protection—see 15.2

No industry consensus exists yet about what level of fire protection is appropriate for an SVC installation. A reasoned engineering judgment should be applied on an individual basis. The following factors should be considered:

Serious fires have occurred in SVC valve halls and in HVDC valve halls that contain similar equipment.

SVC valves contain few, if any, materials that would support combustion. In other words, some materials in an SVC valve can be made to burn in the presence of an arc, but the flame goes out once the arc is removed.

Capacitors within thyristor valve grading circuits should have metal caps and open-

circuiting pressure switches as protection for internal overpressure.

The SVC building and the equipment in the building represent a significant economic investment, and fire protection that is consistent with this investment should be provided.

In view of the above, it seems prudent to recommend the following:

a) All valve halls and control rooms should be equipped with fire detection apparatus that will

immediately trip the SVC and isolate it from any source of electrical energy.

b) Whether a fire-suppressing system is to be installed should be a matter of judgment and local practice. Appropriate gas-based systems may be specified in lieu of water systems.

c) As much as possible, the fire detection system should be designed to avoid false operation.

Two failure modes exist as follows:

1) Failure to detect a fire and trip the SVC

2) False trip of the SVC when there is no fire

d) Large, oil-filled equipment should be treated in a manner that is consistent with the user’s other oil-filled apparatus of similar size, cost, and importance (e.g., firewalls, oil containment walls, and sumps).

e) It is probably not reasonable to apply fire protection to other outdoor equipment.


Annex C

(normative)

Method of calculating thyristor valve losses

Ideally, the losses in the individual modules or thyristor levels should be measured and the total losses for a valve computed from these measurements. However, electric and/or calorimetric methods to determine losses are, in practice, difficult to undertake, and the following calculation method is intended to replace them to a uniform standard.

C.1 Total losses

Losses are made up of:

Pvalve Pcvalve PTsw Pvd Psn

where

Pvd

is the voltage divider losses Psn is the snubber circuit losses Pvalve is the total thyristor valve losses Pcvalve is the thyristor valve conduction losses PTsw is the thyristor switching losses (total) = PTswON + PTswOFF

Physt is the reactor hysteresis losses

C.2 Conduction losses

For each thyristor firing angle, the thyristor currents should be evaluated as follows. The average

thyristor current:

where

ITAV is the thyristor average current ITCR is the TCR fundamental rms current for a fully conducting thyristor valve

= × × [ × ( ×

is the TCR control angle ( /2 to radians)


The rms thyristor current: C.3)

where ITRMS is the thyristor rms current The thyristor valve conduction losses should then be calculated as

n is the number of series connected thyristors in the valve UTO thyristor threshold voltage rT is the thyristor slope resistance Rbusbar is the dc resistance of valve terminal-to-terminal circuit omitting the thyristors

C.3 Thyristor spreading losses at turn-on

For a TCR valve, losses should be calculated as follows.

Turn-on losses assume that the loss is 0.2 J per pulse; although dependent on the individual thyristor, this is a typical value considered acceptable for this calculation:

PTswON = 3 × 2 × n × 0.2 × freq

For TSR and TSC valves, the switching losses use a typical value again and should be assumed as follows:

PTsw = 0.03 × Pcvalve C.4 Thyristor losses at turn-off

For a TCR valve, turn-off losses should be calculated as follows:


where

PTswOFF is the thyristor switch-off losses Qrr is the thyristor recovery charge U1 is the valve connection voltage (rms fundamental) freq is the system fundamental frequency

Qrr should be defined as:

Qrr = k1 × (dIT/dt)0.6

where

Qrr is the thyristor recovery charge k1 is the thyristor-type defined parameter that is evaluated by experiment (it relates the

stored charge of the thyristor to the turn-off dIT/dt at the relevant operating junction temperature)

(dIT /dt) is the derivative of the valve current at zero crossing in A/μs The preceding equation gives the total losses, of which a fraction (1 – kQ) appears in the thyristors and kQ in the snubber resistors. The factor kQ defines the distribution of the recovery charge:

where

kQ is the thyristor parameter.


The distribution of the recovery charge is illustrated in Figure C.1.

Figure C.1—Thyristor stored charge C.5 Voltage divider losses

The voltage divider losses are dependent on the voltage that is applied across the thyristor valve. This voltage is dependent on the firing angle as calculated:

where

U1 is the thyristor blocking voltage (rms)

The power losses should then be calculated:

= ( where

Rvd is the voltage divider resistance (per level)


C.6 Snubber circuit losses

For a TCR, the snubber circuit losses should be evaluated:

where

Csn is the snubber circuit capacitance (per level)

C.7 Valve reactor loss

Where used, the valve reactor loss consists of three components: resistive loss in the winding, eddy current loss, and hysteresis loss in the magnetic core. If an additional damping circuit is employed across the winding, it also incurs loss. Reactor winding loss and the reactor core eddy current loss (and/or reactor damping resistor loss) are already accounted for in C.2 and C.6, respectively. Hysteresis loss should be calculated as follows: A dc magnetization curve for the core material(s) should be determined for the loop of excitation that a valve reactor normally experiences. From the area enclosed by the loop, a characteristic hysteresis loss in joules per kilogram should be determined and applied to the design of the reactor in question, for example:

Physt nL M k freq

where nL is the number of reactor cores in a valve M is the mass of each core k is the characteristic loss, in joules per unit mass.
