04 - pcs915a busbar protection

PCS-915A

Busbar Protection

Instruction Manual

NR Electric Co., Ltd.

Preface

PCS-915A Busbar Protection i

Date: 2013-06-03

Preface

Introduction

This guide and the relevant operating or service manual documentation for the equipment provide

full information on safe handling, commissioning and testing of this equipment.

Documentation for equipment ordered from NR is dispatched separately from manufactured goods

and may not be received at the same time. Therefore, this guide is provided to ensure that printed

information normally present on equipment is fully understood by the recipient.

Before carrying out any work on the equipment, the user should be familiar with the contents of

this manual, and read relevant chapter carefully.

This chapter describes the safety precautions recommended when using the equipment. Before

installing and using the equipment, this chapter must be thoroughly read and understood.

Health and Safety

The information in this chapter of the equipment documentation is intended to ensure that

equipment is properly installed and handled in order to maintain it in a safe condition.

When electrical equipment is in operation, dangerous voltages will be present in certain parts of

the equipment. Failure to observe warning notices, incorrect use, or improper use may endanger

personnel and equipment and cause personal injury or physical damage.

Before working in the terminal strip area, the equipment must be isolated.

Proper and safe operation of the equipment depends on appropriate shipping and handling,

proper storage, installation and commissioning, and on careful operation, maintenance and

servicing. For this reason, only qualified personnel may work on or operate the equipment.

Qualified personnel are individuals who:

Are familiar with the installation, commissioning, and operation of the equipment and of the

system to which it is being connected;

Are able to safely perform switching operations in accordance with accepted safety

engineering practices and are authorized to energize and de-energize equipment and to

isolate, ground, and label it;

Are trained in the care and use of safety apparatus in accordance with safety engineering

practices;

Are trained in emergency procedures (first aid).

Instructions and Warnings

The following indicators and standard definitions are used:

Preface

PCS-915A Busbar Protection ii Date: 2013-06-03

DANGER!

It means that death, severe personal injury, or considerable equipment damage will occur if safety

precautions are disregarded.

WARNING!

It means that death, severe personal, or considerable equipment damage could occur if safety

precautions are disregarded.

CAUTION!

It means that light personal injury or equipment damage may occur if safety precautions are

disregarded. This particularly applies to damage to the device and to resulting damage of the

protected equipment.

WARNING!

The firmware may be upgraded to add new features or enhance/modify existing features, please

make sure that the version of this manual is compatible with the product in your hand.

WARNING!

During operation of electrical equipment, certain parts of these devices are under high voltage.

Severe personal injury or significant equipment damage could result from improper behavior.

Only qualified personnel should work on this equipment or in the vicinity of this equipment. These

personnel must be familiar with all warnings and service procedures described in this manual, as

well as safety regulations.

In particular, the general facility and safety regulations for work with high-voltage equipment must

be observed. Noncompliance may result in death, injury, or significant equipment damage.

DANGER!

Never allow the current transformer (CT) secondary circuit connected to this equipment to be

opened while the primary system is live. Opening the CT circuit will produce a dangerously high

voltage.

WARNING!

Exposed terminals

Do not touch the exposed terminals of this equipment while the power is on, as the high voltage

generated is dangerous

Preface

PCS-915A Busbar Protection iii

Date: 2013-06-03

Residual voltage

Hazardous voltage can be present in the DC circuit just after switching off the DC power supply. It

takes a few seconds for the voltage to discharge.

CAUTION!

Earth

The earthing terminal of the equipment must be securely earthed

Operating environment

The equipment must only be used within the range of ambient environment detailed in the

specification and in an environment free of abnormal vibration.

Ratings

Before applying AC voltage and current or the DC power supply to the equipment, check that they

conform to the equipment ratings.

Printed circuit board

Do not attach and remove printed circuit boards when DC power to the equipment is on, as this

may cause the equipment to malfunction.

External circuit

When connecting the output contacts of the equipment to an external circuit, carefully check the

supply voltage used in order to prevent the connected circuit from overheating.

Connection cable

Carefully handle the connection cable without applying excessive force.

Copyright

Version: R1.02

P/N: EN_YJBH5301.0086.0003

Copyright NR 2013. All rights reserved

NR ELECTRIC CO., LTD.

69 Suyuan Avenue. Jiangning, Nanjing 211102, China

Tel: +86-25-87178185, Fax: +86-25-87178208

Website: www.nrelect.com, www.nari-relays.com

Email: [email protected]

We reserve all rights to this document and to the information contained herein. Improper use in particular reproduction and dissemination

to third parties is strictly forbidden except where expressly authorized.

The information in this manual is carefully checked periodically, and necessary corrections will be included in future editions. If

nevertheless any errors are detected, suggestions for correction or improvement are greatly appreciated.

We reserve the rights to make technical improvements without notice.

Preface

PCS-915A Busbar Protection iv Date: 2013-06-03

Documentation Structure

The manual provides a functional and technical description of this relay and a comprehensive set

of instructions for the relays use and application.

All contents provided by this manual are summarized as below:

1 Introduction

Briefly introduce the application, functions and features about this relay.

2 Technical Data

Introduce the technical data about this relay, such as electrical specifications, mechanical

specifications, ambient temperature and humidity range, communication port parameters, type

tests, setting ranges and accuracy limits and the certifications that our products have passed.

3 Operation Theory

Introduce a comprehensive and detailed functional description of all protective elements.

4 Supervision

Introduce the automatic self-supervision function of this relay.

5 Measurement and Recording

Introduce the management function (measurment and recording) of this relay.

6 Hardware

Introduce the main function carried out by each plug-in module of this relay and providing the

definition of pins of each plug-in module.

7 Settings

List settings including protection settings, system settings, communication settings, label settings,

VEBI settings and etc., and some notes about the setting application.

8 Human Machine Interface

Introduce the hardware of the human machine interface (HMI) module and a detailed guide for the

user how to use this relay through HMI. It also lists all the information which can be view through

HMI, such as settings, measurements, all kinds of reports etc.

9 Communication

Introduce the communication port and protocol which this relay can support, IEC60970-5-103,

IEC61850 and DNP3.0 protocols are introduced in details.

10 Installation

Introduce the recommendations on unpacking, handling, inspection and storage of this relay. A

guide to the mechanical and electrical installation of this relay is also provided, incorporating

Preface

PCS-915A Busbar Protection v

Date: 2013-06-03

earthing recommendations. A typical wiring connection to this relay is indicated.

11 Commissioning

Introduce how to commission this relay, comprising checks on the calibration and functionality of

this relay.

12 Maintenance

A general maintenance policy for this relay is outlined.

13 Decommissioning and Disposal

A general decommissioning and disposal policy for this relay is outlined.

14 Manual Version History

List the instruction manual version and the modification history records.

Preface

PCS-915A Busbar Protection vi Date: 2013-06-03

1 Introduction

PCS-915A Busbar Protection 1-a

Date: 2012-08-31

1 Introduction

Table of Contents

1 Introduction ..................................................................................... 1-a

1.1 Application ....................................................................................................... 1-1

1.2 Function ........................................................................................................... 1-2

1.3 Feature ............................................................................................................. 1-2

1.4 Abbreviation .................................................................................................... 1-3

1 Introduction

PCS-915A Busbar Protection 1-b Date: 2012-08-31

1 Introduction

PCS-915A Busbar Protection 1-1

Date: 2012-08-31

1.1 Application

PCS-915A is a numerical busbar differential protection intended to be used for protecting and

monitoring of double busbars with bus coupler arrangement, single busbar arrangement and

single busbar with single bus section arrangement of various voltage levels. It is capable to protect

up to 25 bays including bus coupler and bus section (bay 01 is connected with bus coupler (BC),

the rest bays are taken as feeder 01~24).

PCS-915A utilizes NRs innovative hardware platform supporting both conventional CT/VT and

electronic current and voltage transformer (ECVT). It is compliant to several communication

protocols, such as IEC60870-5-103, IEC61850 and DNP3.0 protocol.

BB1

BC

*

*

**

VT1

VT2

PCS-915

FR50BF 87B

BB2

Figure 1.1-1 Typical application-Double busbars with BC arrangement

Note!

The bay label of displayed alarm signals, tripping signals, binary input signals, settings and

sampled values related with each feeder and busbar will change with the corresponding

description settings. Please refer to Section 7.8 for details.

For example, if the description setting of feeder 01 i.e. [NameDef_Bay02] is set as Fdr01,

the three-phase initiating contact of BFP for feeder 01 is [BI_BFI_Fdr01]. If

[NameDef_Bay02] is set as 0001, the three-phase initiating contact of BFP for feeder 01

is [BI_BFI_0001].

In this instruction manual, only take the default settings in Table 7.8-1 as an example to

introduce.

1 Introduction

PCS-915A Busbar Protection 1-2 Date: 2012-08-31

1.2 Function

PCS-915 provides the following functions

1. Protection function

Busbar differential protection (87B)

Steady-state percentage differential protection

DPFC percentage differential protection

Bus coupler protection

SOTF protection (50)

End zone fault protection (50DZ)

Breaker failure protection (50BF)

Overcurrent protection (50/51)

Pole discrepancy protection (62PD)

Feeder breaker failure protection (50BF)

Note!

DPFC is the abbreviation of Deviation of Power Frequency Component. When a fault

occurs in the power system, the fault current consists of three parts: the pre-fault power

frequency components, the power frequency variables during the fault and the transient

variables during the fault. DPFC is the power frequency variables during the fault.

2. Auxiliary protection

Dynamic busbar replica

CT circuit failure supervision

VT circuit failure supervision

Disconnector position alarm

1.3 Feature

1. Protection and Control

Parallel calculation of double DSP system

Independent fault detector element

Accurate measurement which can prevent any undesired trip

1 Introduction


Date: 2012-08-31

Less than 20ms typical trip time for busbar differential protection

High sensitive percentage restraint differential protection

Matching to different CT ratios and settable CT adjustment coefficient

A well proven adaptive weighted anti-saturation algorithm

Friendly human machine interface

Comprehensive event recorder

Multi-language option - English, Chinese and Russian

2. Time synchronization

Receiving PPS (pulse per second) and PPM (pulse per minute) via external contact

Receiving PPS, PPM and IRIG-B signal via RS-485

Receiving time synchronization message from substation automation system

3. Event recorder and disturbance recorder

1024 latest fault reports

1024 latest self-supervision reports

1024 latest status change of binary input reports

32 latest fault waveforms (The file format of disturbance recorder is compatible with the

international COMTRADE file)

4. Communication

2 rear RS-485 communication ports supporting with IEC 60870-5-103 protocol, ModBus

protocol or DNP3.0 protocol

4 Ethernet ports at most (depend on the chosen CPU type) supporting with IEC 60870-5-103

protocol or IEC 61850-8-1 protocol

1 rear RS-485 communication port for time synchronization

1 RS-232 communication rear ports for printer

A front multiplex RJ45 port for local communication with a PC

1.4 Abbreviation

Symbol Description

FD Fault detector

BBx Busbar No.x, x is the number of each busbar

1 Introduction

PCS-915A Busbar Protection 1-4 Date: 2012-08-31

Symbol Description

feeder xx Feeder No.xx, xx is the number of each feeder

VCE Voltage controlled element

BBP Busbar differential protection

BFP Breaker failure protection

BFI Breaker failure initiation

EFP End zone fault protection

PD Pole disagreement

SAS Substation automatic system

RTU Remote terminal unit

CT Current transformer

VT Voltage transformer

DPFC Deviation of power frequency component

2 Technical Data


Date: 2013-06-03

2 Technical Data

Table of Contents

2 Technical Data ................................................................................. 2-a

2.1 Electrical Specifications ................................................................................. 2-1

2.1.1 Alternating Analog Current................................................................................................... 2-1

2.1.2 Alternating Analog Voltage ................................................................................................... 2-1

2.1.3 Power Supply ....................................................................................................................... 2-1

2.1.4 Binary Input .......................................................................................................................... 2-1

2.1.5 Binary Output ....................................................................................................................... 2-2

2.2 Mechanical Specifications ............................................................................. 2-2

2.3 Ambient Temperature and Humidity Range .................................................. 2-2

2.4 Communication Port ....................................................................................... 2-3

2.4.1 EIA-485 Port ........................................................................................................................ 2-3

2.4.2 Ethernet Port ........................................................................................................................ 2-3

2.4.3 Optical Fibre Port ................................................................................................................. 2-3

2.4.4 Print Port .............................................................................................................................. 2-4

2.4.5 Clock Synchronization Port ................................................................................................. 2-4

2.5 Type Tests ........................................................................................................ 2-4

2.5.1 Environmental Tests ............................................................................................................ 2-4

2.5.2 Mechanical Tests ................................................................................................................. 2-4

2.5.3 Electrical Tests ..................................................................................................................... 2-4

2.5.4 Electromagnetic Compatibility ............................................................................................. 2-5

2.6 Certifications ................................................................................................... 2-6

2.7 Measurement Scope and Accuracy ............................................................... 2-6

2.8 Management Function .................................................................................... 2-6

2.8.1 Clock Performance .............................................................................................................. 2-6

2.8.2 Fault and Disturbance Recording ........................................................................................ 2-6

2 Technical Data

PCS-915A Busbar Protection 2-b

Date: 2013-06-03

2.8.3 Binary Input Signal............................................................................................................... 2-6

2.9 Protective Functions ....................................................................................... 2-7

2.9.1 Busbar Differential Protection .............................................................................................. 2-7

2.9.2 Switch-onto-fault Protection ................................................................................................. 2-7

2.9.3 Bus coupler/bus section Overcurrent Protection ................................................................. 2-7

2.9.4 Bus coupler/bus section Pole Disagreement Protection ..................................................... 2-7

2.9.5 Bus coupler/bus section Breaker Failure Protection ........................................................... 2-7

2.9.6 Feeder Breaker Failure Protection ...................................................................................... 2-7

2 Technical Data


Date: 2013-06-03

2.1 Electrical Specifications

2.1.1 Alternating Analog Current

Phase rotation ABC

Nominal frequency (fn) 505Hz, 605Hz

Rated Current (In) 1A 5A

Linear to 0.05In~40In

Thermal withstand

-continuously

-for 10s

-for 1s

-for half a cycle

4In

30In

100In

250In

Burden < 0.15VA/phase @In < 0.25VA/phase @In

Accuracy 0.5%In

2.1.2 Alternating Analog Voltage

Phase rotation ABC

Nominal frequency (fn) 505Hz, 605Hz

Rated Voltage (Un) 100V~130V

Linear to 1V~170V

Thermal withstand

-continuously

-10s

-1s

200V

260V

300V

Burden at rated < 0.20VA/phase @Un

Accuracy 0.5%Un

2.1.3 Power Supply

Standard IEC 60255-11:2008

Rated Voltage 110Vdc/125Vdc, 220Vdc/250Vdc

Operating Range 80%~120% of rated voltage

Permissible AC ripple voltage 15% of the nominal auxiliary voltage

Burden

Quiescent condition

Operating condition

2 Technical Data


Date: 2013-06-03

Maximum permissible voltage 120% of rated voltage

Withstand voltage

-continously 2000Vac, 2800Vdc

Response time for logic input

2 Technical Data


Date: 2013-06-03

C)

Transport and storage temperature

range -40C to +70C

Permissible humidity 5%-95%, without condensation

Pollution degree

Altitude

2 Technical Data


Date: 2013-06-03

Wave length 1310nm

Transmission power Min. -20.0dBm

Minimum receiving power Min. -30.0dBm

Margin Min +3.0dB

2.4.3.3 For Synchronization Port

Characteristic Glass optical fiber

Connector type ST

Fibre type Multi mode

Wave length 820nm

Minimum receiving power Min. -25.0dBm

Margin Min +3.0dB

2.4.4 Print Port

Type RS-232

Baud Rate 4.8kbit/s, 9.6kbit/s, 19.2kbit/s, 38.4kbit/s, 57.6kbit/s, 115.2kbit/s

Printer type EPSON 300K printer

Safety level Isolation to ELV level

2.4.5 Clock Synchronization Port

Type RS-485

Transmission distance

2 Technical Data


Date: 2013-06-03

Overvoltage category

Insulation resistance

measurements Isolation resistance >100M@500VDC

2.5.4 Electromagnetic Compatibility

1MHz burst disturbance test

IEC 60255-22-1:2007

Common mode: class III 2.5kV

Differential mode: class III 1.0kV

Electrostatic discharge test

IEC60255-22-2:2008 class IV

For contact discharge: 8kV

For air discharge: 15kV

Radio frequency interference tests

IEC 60255-22-3:2007 class III

Frequency sweep

Radiated amplitude-modulated

10V/m (rms), f=80~1000MHz

Spot frequency

Radiated amplitude-modulated

10V/m (rms), f=80MHz/160MHz/450MHz/900MHz

Radiated pulse-modulated

10V/m (rms), f=900MHz

Fast transient disturbance tests

IEC 60255-22-4:2008

Power supply, I/O, Earth: class IV, 4kV, 2.5kHz, 5/50ns

Communication terminals: class IV, 2kV, 5kHz, 5/50ns

Surge immunity test

IEC 60255-22-5:2008

Power supply, AC input, I/O port: class IV, 1.2/50us

Common mode: 4kV

Differential mode: 2kV

Conducted RF Electromagnetic

Disturbance

IEC 60255-22-6:2001

Power supply, AC, I/O, Comm. Terminal: Class III, 10Vrms, 150

kHz~80MHz

Power Frequency Magnetic Field

Immunity

IEC 61000-4-8:2001

class V, 100A/m for 1min, 1000A/m for 3s

Pulse Magnetic Field Immunity IEC 61000-4-9:2001

class V, 6.4/16s, 1000A/m for 3s

Damped oscillatory magnetic field

immunity

IEC 61000-4-10:2001

class V, 100kHz & 1MHz100A/m

Auxiliary power supply performance

- Voltage dips

-Voltage short interruptions

IEC60255-11: 2008

Up to 500ms for dips to 40% of rated voltage without reset

100ms for interruption without rebooting

2 Technical Data


Date: 2013-06-03

2.6 Certifications

ISO9001:2008

ISO14001:2004

OHSAS18001:2007

ISO10012:2003

CMMI L4

EMC: 2004/108/EC, EN50263:1999

Products safety(PS): 2006/95/EC, EN61010-1:2001

2.7 Measurement Scope and Accuracy

Item Range Accuracy

Phase range 0 ~ 360 0.5% or 1

Frequency fn3Hz 0.01Hz

Currents from protection measurement current transformers

Current 0.05 ~ 40.00In 2.5% of rating or 0.02In

Voltage 0.05 ~ 1.20Un 1.0% of rating or 0.01Un

2.8 Management Function

2.8.1 Clock Performance

Real time clock accuracy 3s/day

Accuracy of GPS synchronization 1ms

External time synchronization IRIG-B (200-98), PPS, IEEE1588 or SNTP protocol

2.8.2 Fault and Disturbance Recording

Maximum duration 6000 sampled points (24 sampled points per cycle)

Recording position 2~50 cycles before pickup of trigger element

2.8.3 Binary Input Signal

Resolution of binary input signal 1ms

Binary input mode Potential-free contact

Resolution of SOE 1ms

2 Technical Data


Date: 2013-06-03

2.9 Protective Functions

Note!

The meanings of symbols mentioned in the following sections are given here.

In -- rated secondary current of reference CT

U2n -- rated secondary phase-to-phase voltage of VT

2.9.1 Busbar Differential Protection

current setting range 0.05In~20.00In

Tolerance of current setting 2.5%xSetting or 0.02In, whichever is greater

Accuracy of voltage setting 2.5% or 0.01U2n whichever is greater

2.9.2 Switch-onto-fault Protection

Current setting range 0.05In~20.00In

Tolerance of current setting 2.5% of setting or 0.02In whichever is greater

2.9.3 Bus coupler/bus section Overcurrent Protection

Current setting range 0.05In~20.00In


Time setting range 0.000~10.000s

Tolerance of time setting 1%xSetting + 40ms

2.9.4 Bus coupler/bus section Pole Disagreement Protection

Residual current setting range 0~20.00In

Negative-sequence current setting range 0~20.00In




2.9.5 Bus coupler/bus section Breaker Failure Protection

Current setting range 0~20.00In




2.9.6 Feeder Breaker Failure Protection

Phase current setting range 0~20.00In

2 Technical Data


Date: 2013-06-03

Residual current setting range 0~20.00In

Negative-sequence current setting range 0~20.00In




Undervoltage setting range 01.732U2n

Residual voltage setting range 0U2n

Negative sequence voltage setting range 0U2n

Accuracy of voltage setting 2.5% or 0.01Un whichever is greater

3 Operation Theory


Date: 2012-08-31

3 Operation Theory

Table of Contents

3 Operation Theory ............................................................................ 3-a

3.1 Overview .......................................................................................................... 3-1

3.2 Busbar Differential Protection ....................................................................... 3-2

3.2.1 Fault detector (FD) element................................................................................................. 3-3

3.2.2 Percentage differential element ........................................................................................... 3-4

3.2.3 Voltage controlled element of busbar differential protection (VCE_BBP) ........................... 3-6

3.2.4 Faulty busbar zone discrimination ....................................................................................... 3-7

3.2.5 Backup busbar differential elements ................................................................................... 3-8

3.2.6 Detection of CT saturation ................................................................................................... 3-8

3.2.7 External Block Signal ........................................................................................................... 3-9

3.2.8 Logic scheme ....................................................................................................................... 3-9

3.3 Bus Coupler/Section (BC/BS) Protection ..................................................... 3-11

3.3.1 BC/BS switch-onto-fault (SOTF) protection ....................................................................... 3-11

3.3.2 BC/BS overcurrent protection ............................................................................................ 3-12

3.3.3 BC/BS breaker failure protection (BFP) ............................................................................ 3-13

3.3.4 BC/BS end zone fault protection ....................................................................................... 3-14

3.3.5 BC/BS pole discrepancy protection (PD) .......................................................................... 3-15

3.4 Feeder breaker Failure Protection (BFP) .................................................... 3-16

3.4.1 Initiation contact ................................................................................................................. 3-16

3.4.2 Current criterion ................................................................................................................. 3-17

3.4.3 Voltage control element of breaker failure protection(VCE) .............................................. 3-17

3.4.4 Logic scheme ..................................................................................................................... 3-18

3.5 Identification of disconnector position ....................................................... 3-19

3.6 VT Circuit Supervision .................................................................................. 3-20

3.7 CT Circuit Supervision ................................................................................. 3-21

3 Operation Theory


Date: 2012-08-31

3.7.1 CT circuit failure ................................................................................................................. 3-21

3.7.2 CT circuit abnormality ........................................................................................................ 3-21

3.8 BC breaker substitution ............................................................................... 3-21

List of Figures

Figure 3.1-1 Double-busbar arrangement ................................................................................. 3-2

Figure 3.2-1 Sketch diagram of double busbars with one bus section arrangement ......... 3-2

Figure 3.2-2 Operation characteristic of steady-state percentage restraint differential

element .................................................................................................................................. 3-5

Figure 3.2-3 Waveform of CT saturation during external fault ............................................... 3-9

Figure 3.2-4 Logic scheme of busbar differential protection ............................................... 3-10

Figure 3.3-1 Logic scheme of SOTF protection ..................................................................... 3-12

Figure 3.3-2 Logic scheme of overcurrent protection........................................................... 3-13

Figure 3.3-3 The logic scheme of BFP .................................................................................... 3-14

Figure 3.3-4 The logic scheme of end zone fault protection ................................................ 3-15

Figure 3.3-5 The logic scheme of pole discrepancy protection ........................................... 3-16

Figure 3.4-1 The logic scheme of BFP (for the bay that main transformer is not connected)

.............................................................................................................................................. 3-18

Figure 3.4-2 The logic scheme of BFP (for the bay that main transformer is connected) 3-19

Figure 3.8-1 BC breaker substituting through BB2 ............................................................... 3-22

Figure 3.8-2 BC breaker substituting through BB1 ............................................................... 3-23

3 Operation Theory


Date: 2012-08-31

3.1 Overview

PCS-915 provides busbar differential protection (BBP), bus coupler/section protection (includes

overcurrent protection, switch-onto-fault protection, pole disagreement protection, end zone fault

protection and breaker failure protection), feeder breaker failure protection, CT circuit supervision

and VT circuit supervision.

The device can support several busbar arrangements, such as double-busbar arrangement,

single-busbar arrangement and single busbar with single bus section arrangement. The switch

method of each busbar arrangement is listed as below:

System settings

Busbar arrangement En_SingleBB En_SingleBB_with_SingleBS

Double-busbar 0 0

Single-busbar 1 0

Single busbar with single bus section 0 1

Please refer to Section 7.1 about detailed description of each system setting. For single busbar

with bus section arrangement, the system setting [Cfg_DS_BBx] (x=1, 2) is used to indicate which

busbar zone the feeder is connected to.

The device has 2 plug-in modules (protection DSP module and fault detector DSP module) to

perform calculation. The protection DSP module is responsible for calculation of protection

elements, and fault detector DSP module is responsible for calculation of fault detectors. Any fault

detector of fault detector DSP module picks up to provide positive supply of output relays. The

relays will trip only if the fault detector and the corresponding protection element operate

simultaneously. On the premise of 24 samples per cycle, all data measurement, calculation and

logic discrimination can be processed within one sampling period. The event recording and

protection logic calculation are completed simultaneously.

The following figure shows double busbars arrangement and application mode.

3 Operation Theory


Date: 2012-08-31

*

BB2

BB1

Panel A

BC

* * * *

PCS-915

VT1

VT2

Figure 3.1-1 Double-busbar arrangement

3.2 Busbar Differential Protection

In order to be easy to explain the protection function and scheme, the first busbar is defined as

busbar No.1 (BB1) and the second busbar is defined as busbar No.2 (BB2). In the case of project

application, the number of each busbar can be set based on on-site case. The polarity marking of

feeder CT should be on the busbar side and the polarity of BC CT should be on the BB1 side.

Please refer to the sketch diagram of primary system Figure 3.2-1.

*

BB2

BB1

BC

* * * *

Discriminative

zone No.2

Discriminative

zone No.1Check zone

Figure 3.2-1 Sketch diagram of double busbars with one bus section arrangement

3 Operation Theory


Date: 2012-08-31

Note!

The protective device only identifies the physical position of busbar, ignoring the number of

busbar, takes the busbar arrangement in Figure 3.2-1 as an example, the protective device

will refer the busbar of which the polarity of BC CT is towards as BB1.

The primary protection of PCS-915 is phase-segregated percentage restraint differential

protection. The differential circuits include check zone differential circuit and discriminating zone

differential circuits of each busbar zone. The check zone differential element is used to distinguish

between internal and external fault of the overall busbar system, it measures the current from all

the circuits connected to the busbar system except BC and BS. The discriminating zone

differential elements are used to select faulty zone by measuring the current of all the circuits

connected to individual zones of the busbar system separated by BC and BS.

Discriminating zone No.1 is defined as discriminating differential element of BB1. Discriminating

zone No.2 is defined as discriminating differential element of BB2.

3.2.1 Fault detector (FD) element

PCS-915 provides three independent FD elements for busbar differential protection, which are

DPFC voltage FD element, DPFC current FD element and differential current FD element. If any of

these three elements picks up, the positive supply to the output relays is then available and wait

for the tripping signal from busbar differential protection. The fault detector output signal will last

for 500ms after the corresponding fault detector element drop off.

1. DPFC voltage FD element

When DPFC voltage of any phase of any busbar is larger than the threshold, DPFC voltage FD

element picks up, the operating criterion is:

u>UFloat+0.05Un Equation 3.2-1

Where:

u: Instantaneous value of phase-to-phase DPFC voltage

UFloat: Float threshold value, automatically varied with the gradually voltage changing

0.05Un: Fixed threshold value, Un is the rated secondary phase-to-ground voltage.

If voltage is not sampled or VT circuit failure is detected, DPFC voltage FD element will quit

automatically.

2. DPFC current FD element

If DPFC check zone restraint current is larger than the threshold, DPFC current fault detector

element will operate, the operating criterion is:

si>SIFloat+0.5In Equation 3.2-2

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Date: 2012-08-31

Where:

si: Instantaneous value of DPFC check zone restraint current of any phase (scalar sum of current

change of all circuits/bays for check zone)

SIFloat: Float threshold value, automatically varied with the gradually current changing

0.5In: Fixed threshold value, In is the rated secondary current of reference CT.

3. Differential current FD element

When any phase of the check zone differential current is larger than the setting, this element will

operate. The operating criterion is:

ID> [I_Pkp_Pcnt_BBP] Equation 3.2-3

Where:

ID: Differential phase current of check zone

[I_Pkp_Pcnt_BBP]: Current setting of busbar differential protection

3.2.2 Percentage differential element

The percentage restraint differential element includes steady-state percentage restraint differential

element and DPFC percentage restraint differential element.

Steady-state percentage restraint differential element

The differential current: ID =

m

1j

jI

The restraint current: IR =

m

1j

jI

The operating criterion is:

R

D

KI

]_Pcnt__[I

I

BBPPkpI

D

Equation 3.2-4

Where:

K: Restraint coefficient of steady-state differential element

Ij: The current of the j-th feeder (Feeder j) connected

[I_Pkp_Pcnt_BBP]: Current setting of busbar differential protection

The operation characteristic is shown as below.

3 Operation Theory


Date: 2012-08-31

[I_Pkp_Pcnt_BBP]

Operation region

IR

ID

ID=IR

ID=kIR

Figure 3.2-2 Operation characteristic of steady-state percentage restraint differential element

To enhance the sensitivity of steady-state check zone differential element for a fault occurred in

the weak source bus zone when the BC breaker is open, dual restraint coefficients [0.5, 0.3] and

[0.6, 0.5] are adopted for steady-state check zone and discriminating zones respectively.

When one of the following conditions is fulfilled, the busbar steady-state percentage restraint

differential protection will operate.

1. Steady-state check zone differential element with high restraint coefficient (0.5) operates and

steady-state discriminating zone differential element with low restraint coefficient (0.5)

operates.

2. Steady-state check zone differential element with low restraint coefficient (0.3) operates and

steady-state discriminating zone differential element with high restraint coefficient (0.6)

operates.

DPFC percentage differential element

The DPFC percentage restraint differential element is adopted to enhance the performance of

busbar protection against high impedance fault and the influence of heavy loading condition. The

busbar DPFC differential protection is formed by DPFC percentage restraint differential element

and steady-state check zone percentage restraint differential element with fixed restraint

coefficient 0.2.

The DPFC differential current: ID =

m

1j

jI

The DPFC restraint current: IR =

m

1j

jI

3 Operation Theory


Date: 2012-08-31

The operating criterion is:

R

/

D

RD

DPickupDFloatD

IKI

0.2II

III

Equation 3.2-5

Where:

K': DPFC restraint coefficient

Ij: DPFC current of the j-th feeder (Feeder j) connected

IDFloat: Float threshold value of DPFC check zone differential current

IDPickup: Fixed threshold value of DPFC check zone differential current, which derives from the

setting of [I_Pkp_Pcnt_BBP]

Similar to steady-state percentage restraint differential element, dual restraint coefficients are also

introduced to DPFC differential element. The restraint coefficients are fixed at [0.65, 0.3] and [0.65,

0.5] for DPFC check zone and discriminating zones respectively.

When the steady-state check zone percentage restraint differential element with fixed restraint

coefficient of 0.2 operates, if one of the following conditions is fulfilled, the busbar DPFC

percentage restraint differential protection will operate.

1. DPFC check zone percentage restraint differential element with high restraint coefficient (0.65)

operates and DPFC discriminating zone percentage restraint differential element with low

restraint coefficient (0.5) operates.

2. DPFC check zone percentage restraint differential element with low restraint coefficient (0.3)

operates and DPFC discriminating zone percentage restraint differential element with high

restraint coefficient (0.65) operates.

3.2.3 Voltage controlled element of busbar differential protection (VCE_BBP)

Voltage controlled element is used as an auxiliary condition.

The operating criteria are:

UP [V_UV_VCE_BBP] Equation 3.2-6

3U0 [V_ROV_VCE_BBP] Equation 3.2-7

U2 [V_NegOV_VCE_BBP] Equation 3.2-8

Where:

UP: Secondary rated phase-to-ground voltage

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3U0: Residual voltage (calculated internally)

U2: Negative sequence voltage

[V_UV_VCE_BBP]: Phase-to-ground voltage setting for blocking BBP

[V_ROV_VCE_BBP]: Residual voltage setting for blocking BBP

[V_NegOV_VCE_BBP]: Negative sequence voltage setting for blocking BBP

Busbar differential protection is always blocked by voltage control element. Busbar differential

protection can not operate to trip faulty busbar zone unless the voltage of corresponding busbar

zone met any of above criterions.

When the protective device is applied to an unearthed system, i.e. the system setting

[Opt_UnearthedSys_Mode] is set as 1, the criteria of voltage control element will be changed.

UPP [V_UV_VCE_BBP] Equation 3.2-9

U2[V_NegOV_VCE_BBP] Equation 3.2-10

Where:

UPP: Phase-to-phase voltage


[V_UV_VCE_BBP]: Phase-to-phase voltage setting for blocking BBP

[V_NegOV_VCE_BBP]: Negative voltage setting for blocking BBP

3.2.4 Faulty busbar zone discrimination

The check zone differential element calculates the current from all circuits connected to the entire

busbar system except BC and BS to distinguish between internal and external fault. The

discriminating zone differential elements calculate the current of all the circuits connected to

individual zones via replica image of disconnector position to determine faulty zone.

When the operation criterion of check zone differential element (steady-state check zone

differential element is supervised by CT saturation detector 2 and DPFC check zone differential

element is supervised by CT saturation detector 1, to be described in the following section) and

any discriminating zone differential element is fulfilled, VCE_BBP of any busbar operates, the

busbar differential protection will operate to trip all bays connected to the faulty busbar.

The protection has a feature of inter-connection operation mode, the feature will be effective

automatically under the following conditions.

1. The binary input [EBI_IntLink_Mode] is energized or the virtual enable binary input

[VEBI_IntLink_Mode] is set as 1, it should be done when two bus zones are coupled together

and unable to detach for a particular system operation condition.

2. On-load transfer condition (when two busbar disconnectors of one feeder are closed at the

3 Operation Theory


Date: 2012-08-31

same time).

Under the inter-connection operation mode, the discriminating zone differential elements measure

the current signals are the same as that of check zone differential element. The coupled busbars

will be tripped simultaneously when there is a fault.

3.2.5 Backup busbar differential elements

If only the check zone percentage restraint differential element (supervised by CT saturation

detector 2) operates, two stages of backup protection with fixed time delay are applied to trip the

corresponding circuit breakers. Stage 1 of backup protection will trip BC/BS (when VCE of any

busbar operates) and the feeders of which CT correction coefficient is not zero and does not have

disconnector position after 240ms. Stage 2 of backup protection will trip the feeders connected to

the busbar of which voltage clocking has been released and the feeders with current larger than

2*In (In: the rated secondary current of reference CT) after 480ms.

3.2.6 Detection of CT saturation

Two detectors are used to prevent unwanted tripping caused by severe CT saturation during

external close up fault. If the differential current is determined to be caused by CT saturation, the

device will block busbar differential protection to prevent mal-operation.

CT saturation detector 1

When DPFC voltage or current FD element operates, the adaptive weighted algorithm for CT

saturation detector will be activated. In case of busbar fault occurs, DPFC differential element will

operate almost at the same time with DPFC voltage FD element or DPFC current FD element,

whereas for external fault, DPFC differential element will not operate before CT saturation at the

fault incipient stage, it will only operate after DPFC voltage element and DPFC current element in

case CT is saturated. Adaptive weighted algorithm for CT saturation detector is derived from the

difference of operating time among these DPFC elements. In coordination with DPFC differential

element, it has performed excellently to distinguish between internal and external fault with CT

saturation.

CT saturation detector 2

Harmonic restraint element is used in CT saturation detector 2 by analyzing the waveforms of

differential current harmonics. The detector enables the busbar differential element to remain

stable for an external fault with CT saturation while to maintain fast tripping for the external fault

evolved to internal fault on the same phase.

The blocking signal of CT saturation detector 2 will only last for 500ms. After that the busbar

differential element is released to operate for complicated fault conditions and minimized affected

area. In practical cases, CT transient saturation will not be more than 500ms.

3 Operation Theory


Date: 2012-08-31

Figure 3.2-3 Waveform of CT saturation during external fault

Above figure shows the current waveforms recorded in dynamic simulation with heavy CT

saturation during external phase-to-phase fault. Protection stability is well achieved in this extreme

case.

3.2.7 External Block Signal

PCS-915 provides a binary input [BI_Blk_BBP] to block BBP through external binary signal. If the

logic setting [En_BI_Blk_BBP] is set as 1, BBP will be blocked if the binary input [BI_Blk_BBP] is

energized. However, if the binary input [BI_Blk_BBP] is energized for longer than 1 second,

PCS-915 will issue an alarm [Alm_Blk_BBP] and the blocking for BBP is released.

3.2.8 Logic scheme

Figure 3.2-4 only takes BB1 as an example, the logic scheme of BB2 is similar to it.

3 Operation Theory


Date: 2012-08-31

DPFC voltage FD element

&

&

DPFC current FD element

DPFC DIF 1

1

DPFC DIF

SP DIF (K=0.2)

500ms&

&

1

SP DIF 1 (K=0.2)

HM REL 1

500ms&

&

[En_BBP]

[EBI_BBP]

SP DIF 1

HM REL

SP DIF

VCE_BBP 1

VCE_BBP x

1

&

&

Op_TrpBB1_Pcnt_BBP

Op_TrpBC_BBP

CT

sa

tura

tion

de

tecto

r 1

240ms[Op_Dly1_Pcnt_BBP]&

1

480ms[Op_Dly2_Pcnt_BBP]

[VEBI_BBP]

VCE_BBP x & BBx is in service

& Op_TrpBB1_DPFC_BBP

SP DIF x

CT circuit failure

[BI_Blk_BBP]

0 1s[En_BI_Blk_BBP]

&

1

Figure 3.2-4 Logic scheme of busbar differential protection

Please refer to Chapter Settings about the description of each setting.

Where:

DPFC current FD element: DPFC current fault detector element, please refer to Section 3.2.1.

DPFC voltage FD element: DPFC voltage fault detector element, please refer to Section 3.2.1.

DPFC DIF: DPFC percentage differential element for check zone

DPFC DIF1: DPFC percentage differential element for bus zone No.1

SP DIF: Steady-state percentage differential element for check zone

SP DIF1: Steady-state percentage differential element for bus zone No.1

SP DIF2: Steady-state percentage differential element for bus zone No.2

3 Operation Theory


Date: 2012-08-31

HM REL: Harmonic release element for check zone

HM REL1: Harmonic release element for bus zone No.1

VCE_BBP 1: Voltage controlled element of BBP of BB1 operates

VCE_BBP x: Voltage controlled element of BBP of any busbar operates

VCE_BBP x & BBx is in service: VCE_BBP of any energized busbar operates

Op_Dly1_Pcnt_BBP: Stage 1 of backup busbar differential protection operates

Op_Dly2_Pcnt_BBP: Stage 2 of backup busbar differential protection operates

Op_TrpBB1_DPFC_BBP: DPFC percentage differential protection operates to trip BB1

Op_TrpBB1_Pcnt_BBP: Steady-state percentage differential protection operates to trip BB1

Op_TrpBC_BBP: BBP operates to trip BC breaker

3.3 Bus Coupler/Section (BC/BS) Protection

PCS-915 provides switch-onto-fault protection, breaker failure protection, end zone fault protection,

pole discrepancy protection and overcurrent protection for BC/BS.

3.3.1 BC/BS switch-onto-fault (SOTF) protection

After any busbar has been maintained and before being put into operation, it is needed to close

BC/BS and make the energizing test firstly. During the energizing process, if any fault occurs in the

energized busbar, SOTF protection will operate to trip BC/BS to clear the fault.

SOTF protection will be enabled for 300ms if any of the following conditions is met.

1. The status of the binary input [BI_52b_BC] changes from 1 to 0.

2. The binary input [BI_52b_BC] is energized and BC current changes from being smaller than

0.04IN to being greater than 0.04IN.

3. The binary input [BI_52b_BC] is energized and BB1 and BB2 are in service.

The logic scheme of SOTF protection is shown as Figure 3.3-1.

3 Operation Theory


Date: 2012-08-31

Ia_BC>0.04IN

&

BB2 is in service

BB1 is in service

1

Ib_BC>0.04IN

&

Ic_BC>0.04IN

Ia_BC>[I_OC_SOTF_BC]

&

[En_SOTF_BC]

Ib_BC>[I_OC_SOTF_BC]

Ic_BC>[I_OC_SOTF_BC]

&

Op_TrpBC_SOTF

[EBI_SOTF_BC]

&

1

0 300ms

&

[VEBI_SOTF_BC]

[BI_52b_BC]

[BI_52a_BC]

&

Figure 3.3-1 Logic scheme of SOTF protection

Please refer to Chapter Settings about the description of corresponding settings.

Where:

BB1(2) is in service: If busbar phase voltage of BB1(2) is greater than 0.3UN or current of any

connected bay is larger than 0.04IN, BB1(2) is thought as in service.

[EBI_SOTF_BC]: The binary input of enabling BC SOTF protection

[BI_52b_BC]: Normally closed auxiliary contact of BC/BS

[BI_52a_BC]: Normally open auxiliary contact of BC/BS

Op_TrpBC_SOTF: BC/BS SOTF protection operates to trip BC/BS breaker

Ia_BC: Phase A current of BC/BS

Ib_BC: Phase B current of BC/BS

Ic_BC: Phase C current of BC/BS

3.3.2 BC/BS overcurrent protection

When temporary usage of the BC/BS breaker to substitute a feeder circuit breaker, typically for the

maintenance of the latter. Overcurrent protection can be provided for this application.

The logic scheme of overcurrent protection is shown as Figure 3.3-2.

3 Operation Theory


Date: 2012-08-31

Ia_BC>[I_OC_BC]

Ib_BC>[I_OC_BC]

Ic_BC>[I_OC_BC]

1

3I0_BC>[I_ROC_BC]

[En_OC_BC]

[EBI_OC_BC]

&

&[t_OC_BC]

Op_TrpBC_OC

[VEBI_OC_BC]

&[t_OC_BC]

Op_TrpBC_ROC

Figure 3.3-2 Logic scheme of overcurrent protection


Where:

[EBI_OC_BC]: The binary input of enabling BC/BS overcurrent protection

Op_TrpBC_OC: Phase overcurrent protection of BC/BS operates to trip BC/BS

Op_TrpBC_ROC: Zero-sequence overcurrent protection of BC/BS operates to trip BC/BS

3I0_BC: Residual current of BC/BS

3.3.3 BC/BS breaker failure protection (BFP)

When tripping signal has been delivered to BC/BS breaker, while the breaker is failed to open

since the BC/BS current is still larger than the setting [I_BFP_BC] with a specific time delay, BFP

will operate to trip all feeders connected to both busbars with the time delay of [t_TrpBB_BFP_BC].

BC/BS breaker failure protection is blocked by voltage controlled element of BBP (Please refer to

Section 3.2.3).

There are several options to initiate BFP:

1. BBP

2. Breaker failure initiating binary inputs are energized

The logic scheme of BC/BS BFP is shown as Figure 3.3-3.

3 Operation Theory


Date: 2012-08-31

Ia_BC>[I_BFP_BC]

Ib_BC>[I_BFP_BC]

Ic_BC>[I_BFP_BC]

1

BBP Trip BB2

1

&

Op_BFP_BB1

VCE_BBP 1

VCE_BBP 2

[BI_BFI_BC_2]

[t_TrpBB_BFP_BC]

1BBP Trip BB1

BBP Trip BC

&

& Op_BFP_BB2[t_TrpBB_BFP_BC]

&

[BI_BFI_BC_1]

Figure 3.3-3 The logic scheme of BFP


Where:

BI_BFI_BC_1: Initiating contact of breaker failure protection for BC/BS

BI_BFI_BC_2: Any binary input of the binary module located in slot No.09 is energized (in order to

prevent BC/BS BFP from mal-operation due to hardware fault of the binary input module.

VCE_BBP 1: voltage controlled element of BBP of BB1, Please refer to Section 3.2.3)

VCE_BBP 2: voltage controlled element of BBP of BB2, Please refer to Section 3.2.3)

3.3.4 BC/BS end zone fault protection

If a fault occurs between BC/BS breaker and BC/BS CT, the fault can not be cleared after busbar

on the breaker side is tripped. In order to clear the fault quickly, a dedicated end zone fault

protection is provided.

After busbar differential protection sends the command to trip BC/BS, if the BC/BS breaker has

been tripped but the BC/BS current is detected, the end zone fault protection will operate and the

BC/BS current will be excluded from discriminative zone percentage differential circuit with a time

delay of 150ms.

If both busbars are in service and BC/BS breaker is open, in order to prevent both busbars from

being tripped during end fault, the BC/BS current will be excluded from discriminative zone

percentage differential circuit in this case.

3 Operation Theory


Date: 2012-08-31

BB No.1

BC Breaker

BB No.2

BC CT

Dead zone

The logic scheme of end zone fault protection is shown as Figure 3.3-4.

&

BB2 is in service

BB1 is in service

&Ia_BC>0.04IN

Ib_BC>0.04IN

Ic_BC>0.04IN

1

Ia_BC>0.1IN

Ib_BC>0.1IN

Ic_BC>0.1IN

1

0 400ms

&

&

IBC is excluded from discriminative

zone percentage differential circuit[BI_52b_BC]

[BI_52a_BC]

&

1

[EBI_Decoupled_BC]

&

SP Trip BC

SP DIF

&

150ms

Figure 3.3-4 The logic scheme of end zone fault protection


BB1(2) is in service: If busbar phase voltage of BB1(2) is greater than 0.3UN or current of any

connected bay is larger than 0.04IN, BB1(2) is thought as in service.

SP DIF: Steady-state percentage differential element for check zone

SP: Steady-state percentage differential element

3.3.5 BC/BS pole discrepancy protection (PD)

Pole discrepancy protection is designed for the case that pole discrepancy of BC/BS breaker is

detected due to one phase of BC/BS breaker is open.

3 Operation Theory


Date: 2012-08-31

Pole discrepancy protection is initiated by series-parallel connected auxiliary contacts of BC/BS

breaker i.e. the binary input [BI_PD_BC].

In addition of series-parallel connected auxiliary contacts of BC/BS breaker, residual and negative

sequence current are used as auxiliary criteria.

The logic scheme of pole discrepancy protection is shown as Figure 3.3-5.

&

[BI_PD_BC]

3I0_BC>[I_ROC_PD_BC]

I2_BC>[I_NegOC_PD_BC]

1

[EBI_PD_BC]

[t_PD_BC]

[En_PD_BC]

&

&

Op_BC_PD

52b_A 52a_A

[BI_PD_BC]

52b_B

52b_C

52a_B

52a_C

[VEBI_PD_BC]

Figure 3.3-5 The logic scheme of pole discrepancy protection


BI_PD_BC: pole discrepancy binary input of BC/BS

Op_BC_PD: pole discrepancy protection of BC/BS operates to trip BC/BS breaker

3I0_BC, I2_BC: Residual and negative sequence current of BC/BS.

3.4 Feeder breaker Failure Protection (BFP)

Breaker failure protection is available for each feeder. When a breaker is determined failed to trip,

the breaker failure protection will trip BC/BS after time delay of [t_TrpBC_BFP] and all feeders

after time delay of [t_TrpBB_BFP].

3.4.1 Initiation contact

For each bay, BFP can be initiated externally via binary inputs by phase-segregated tripping

contacts or three-phase tripping contacts of protective device for the corresponding bay.

1. Phase-segregated tripping contact

[BI_A_BFI_Bayxx]: The binary input for initiating BFP of phase A

[BI_B_BFI_Bayxx]: The binary input for initiating BFP of phase B

[BI_C_BFI_Bayxx]: The binary input for initiating BFP of phase C

3 Operation Theory


Date: 2012-08-31

xx=04~13, 16~25.

2. Three-phase tripping contact

[BI_BFI_Bayxx]: The binary input for initiating BFP of three phases.

xx=02~25.

It is recommended that main transformer should be connected to the bays that only have the

dedicated opto-coupler used by three-phase tripping contact (bay 02, 03, 14, 15). For each bay

that main transformer is connected, a binary input for releasing voltage blocking element

[BI_Rls_VCE_BBP_Trans] is provided. For a transformer, when a fault occurs at the low-voltage

side but the breaker of the high-voltage side fails, the voltage condition of HV side busbar maybe

not met, so the other tripping contact can be connected to the the binary input

[BI_Rls_VCE_BBP_Trans] to release voltage blocking element.

If the bay is tripped by BBP, the breaker failure protection of this bay will be initiated.

For the bay that main transformer is connected, BFP operates can initiate intertripping to trip

breakers of other sides of the main transformer.

3.4.2 Current criterion

1. Current criterion 1

Phase current is greater than the setting [I_OC_BFP_Bayxx]


Residual current is greater than the setting [I_ROC_BFP_Bayxx]


Negative sequence current is greater than the setting i.e. [I_NegOC_BFP_Bayxx]

3.4.3 Voltage control element of breaker failure protection(VCE)

Voltage control element is used as an auxiliary condition.

The criteria are:

UP[V_UV_VCE_BFP] Equation 3.4-1

3U0[V_ROV_VCE_BFP] Equation 3.4-2

U2[V_NegOV_VCE_BFP] Equation 3.4-3

Where:

UP: Secondary rated phase-to-ground voltage

3U0: Residual voltage


[V_UV_VCE_BFP]: Phase voltage setting for blocking BFP

3 Operation Theory


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[V_ROV_VCE_BFP]: Residual voltage setting for blocking BFP

[V_NegOV_VCE_BFP]: Negative sequence voltage setting for blocking BFP

When the protective device is applied to an unearthed system, i.e. the system setting

[Opt_UnearthedSys_Mode] is set as 1, the criteria of voltage control element will be changed.

UPP [V_UV_VCE_BFP] Equation 3.4-4

U2[V_NegOV_VCE_BFP] Equation 3.4-5

Where:

UPP: Phase-to-phase voltage


[V_UV_VCE_BFP]: Phase-to-phase voltage setting for blocking BFP

[V_NegOV_VCE_BFP]: Negative sequence voltage setting for blocking BFP

3.4.4 Logic scheme

The logic scheme of BFP is shown as Figure 3.4-1.

Ia_Bayxx>[I_OC_BFP_Bayxx]

Ib_Bayxx>[I_OC_BFP_Bayxx]

Ic_Bayxx>[I_OC_BFP_Bayxx]

1

[BI_C_BFI_Bayxx]

1&

[BI_A_BFI_Bayxx]

[BI_B_BFI_Bayxx]

[En_ROC_BFP_Bayxx]

&

&

VCE 1

VCE 2

3I0_Bayxx>[I_ROC_BFP_Bayxx]

I2_Bayxx>[I_NegOC_BFP_Bayxx]

[En_NegOC_BFP_Bayxx]

&

&

&

&BBP operates to trip feeder xx

1

1

&

1

Disconnector position of BB1


&

&

&

&

&

[En_BFP]

[EBI_BFP] &

[VEBI_BFP]Op_Retrip_Bayxx

Op_TrpBC_BFP

Op_BFP_BB1 [t_TrpBB_BFP]

[t_ReTrp_BFP]

[t_TrpBC_BFP]

Op_Retrip_Bayxx

Op_TrpBC_BFP

Op_BFP_BB2 [t_TrpBB_BFP]

[t_ReTrp_BFP]

[t_TrpBC_BFP]

[BI_BFI_Bayxx]

1

Figure 3.4-1 The logic scheme of BFP (for the bay that main transformer is not connected)

3 Operation Theory


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Ia_Bayxx>[I_OC_BFP_Bayxx]

Ib_Bayxx>[I_OC_BFP_Bayxx]

Ic_Bayxx>[I_OC_BFP_Bayxx]

1

1&

&

[En_BFP]

[En_ROC_BFP_Bayxx]

&

&

VCE 1

VCE 2

3I0_Bayxx>[I_ROC_BFP_Bayxx]

I2_Bayxx>[I_NegOC_BFP_Bayxx]

[En_NegOC_BFP_Bayxx]

[BI_Rls_VCE_BFP_Trans]

&

&

1

[EBI_BFP]



1

1

&

&

&

&

&

[t_TrpBC_BFP]

[t_TrpBB_BFP]

[t_ReTrp_BFP]

[t_TrpBB_BFP]

[t_ReTrp_BFP]

[t_TrpBC_BFP]

[VEBI_BFP]

1

BBP operates to trip feeder xx

[BI_BFI_Bayxx]

Op_ReTrp_Bayxx

Op_TrpBC_BFP

Op_BFP_BB1

Op_IntTrp_BFP_Bayxx

Op_ReTrp_Bayxx

Op_TrpBC_BFP

Op_BFP_BB2

Op_IntTrp_BFP_Bayxx

Figure 3.4-2 The logic scheme of BFP (for the bay that main transformer is connected)


3I0_Bayxx: Residual current of bay xx

I2_Bayxx: The negative sequence current of bay xx

Ia_Bayxx: The phase A current of bay xx

Ib_Bayxx: The phase B current of bay xx

Ic_Bayxx: The phase C current of bay xx

Disconnector position of BBx: bay xx is connected to BBx (according to disconnector position of the

bay)

3.5 Identification of disconnector position

In a substation with double busbars layout, feeders may be switched from one busbar to the other

busbar during operation, and it is necessary to identify real time topology of the busbar correctly.

Disconnector positions are adopted for this identification and self-diagnosis is carried out

3 Operation Theory


Date: 2012-08-31

simultaneously. If there is current flowing in a bay but the bay has no disconnector positions for

dual busbars, the protective device can remember the original disconnector position. An

abnormality of disconnector position is detected and disconnector position alarms [Alm_DS_Bayxx]

will be issued with a specific time delay in any of the following cases (xx: from 02 to 25).

1. Disconnector position is changed. The operator should check it and confirm whether it is

correct. The alarm can be reset by energizing the binary input [BI_ConfirmDS].

2. If both disconnectors to BB1 and BB2 of a bay are closed, an alarm signal [Alm_IntLink] will

be issued. The alarm can not be reset by energizing the binary input [BI_ConfirmDS].

3. There is current detected in a bay but the bay has no disconnector positions for dual busbars.

The alarm can not be reset by energizing the binary input [BI_ConfirmDS]. In this case, the

protective device can remember the original disconnector position of the bay, and check its

validity based on the current distribution of system.

4. If discriminating zone differential current is greater than 0.04IN due to the wrong disconnector

position, an alarm will be issued with a time delay and the device can identify the right

disconnector position based on the current distribution of system.

Besides, in order to prevent the feeder from missing-operation because the bay has no

disconnector position, no matter which busbar zone does the fault occur in, the bays whose CT

correction coefficient is not zero but no disconnector position can be detected will be tripped.

Note!

When disconnector position alarm is issued, the operator must check the actual condition

at first and then energize the binary input [BI_ConfirmDS] to reset the alarm if it is correct.

Usually a button on the panel is provided, pressing the button will result in energizing the

binary input [BI_ConfirmDS].

3.6 VT Circuit Supervision

1. If three times busbar negative sequence voltage (3U2) is larger than 0.2UN (UN: the secondary

rated phase-to-ground voltage of VT), an alarm [Alm_VTS_BB1] or [Alm_VTS_BB2] will be

issued with a time delay of 1.25s.

2. If any busbar is in service and the sum of the amplitude of busbar three-phase voltage

(|UA|+|UB|+|UC|) is smaller than UN, an alarm [Alm_VTS_BB1] or [Alm_VTS_BB2] will be

issued with a time delay of 1.25s.

3. When the logic setting [Opt_UnearthedSys_Mode] is set as 1, if three times busbar negative

sequence voltage (3U2) is greater than 0.2UN or any phase-to-phase voltage is smaller than

0.7UN_PP (UN_PP: the secondary rated phase-to-phase voltage of VT), an alarm

[Alm_VTS_BB1] or [Alm_VTS_BB2] will be issued with a time delay of 1.25s.

If the fault detector element picks up due to a disturbance in the system, the VT circuit supervision

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will be disabled. When VCE of a busbar operates, an alarm [Alm_Pkp_VCE_BB1] or

[Alm_Pkp_VCE_BB2] will be issued with a time delay of 3s. When the three-phase voltage returns

to normal condition, the alarm will be reset and the protective device will return to normal operation

condition automatically with a time delay of 10s.

3.7 CT Circuit Supervision

3.7.1 CT circuit failure

1. If check zone differential current is greater than the setting [I_Alm_CTS], an alarm [Alm_CTS]

will be issued with a time delay of 5s and BBP will be blocked. The alarm can be reset only by

pressing reset button on the panel to energize binary input [BI_RstTarg] after the CT circuit

returns to normal condition.

2. If check zone differential current is smaller than the setting i.e. [I_Alm_CTS] and both

discriminating zone currents are greater than [I_Alm_CTS], an alarm [Alm_CTS_BC] will be

issued with a time delay of 5s and BBP will not be blocked but single busbar mode will be

enabled automatically. Under this situation, if any internal fault occurs, faulty busbar will not

be identified. The alarm can be reset only by pressing reset button on the panel to energize

the binary input [BI_RstTarg] even the CT circuit returns to normal condition.

When VCE of any busbar operates, CT circuit failure will not be detected.

3.7.2 CT circuit abnormality

1. If check zone differential current is greater than the setting i.e. [I_Alm_SensCTS], an alarm

[Alm_SensCTS] will be issued with a time delay of 5s. The alarm can be reset only by

pressing reset button on the panel to energize the binary input [BI_RstTarg] after the CT

circuit returns to normal condition.

2. If check zone differential current is smaller than the setting [I_Alm_SensCTS] and both

discriminating zone currents are greater than [I_Alm_SensCTS], an alarm

[Alm_SensCTS_BC] will be issued with a time delay of 5s. The alarm can be reset only by

pressing reset button on the panel to energize the binary input [BI_RstTarg] after the CT

circuit returns to normal condition.

3. BBP will not be blocked when CT circuit is abnormal.

3.8 BC breaker substitution

If BC breaker is used temporarily to substitute one of feeder breakers through transfer bus, the

binary input [EBI_BT_BC] should be energized. The binary input [EBI_NegPolar_CT_BT] should

be energized or de-energized according to the busbar arrangement. The polarity mark of feeder

CT is on the busbar side, if the polarity mark of the substituted BC CT is on the busbar side, the

binary input [EBI_NegPolar_CT_BT] should be de-energized and BC current will be calculated in

check zone differential current and discriminating zone differential current. If the polarity mark of

the substituting BC CT is on the feeder side, the binary input [EBI_NegPolar_CT_BT] should be

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energized and negative value of BC current will be calculated in check zone differential current

and discriminating zone differential current.

If BC breaker is used temporarily to substitute one of feeder breakers, the BC current will be taken

as the current of the substituted feeder, whether the positive value or the negative value of the

substituting BC current is calculated in check zone differential current and discriminating zone

differential current depends on the status of the binary input [EBI_NegPolar_CT_BT].

If the normally open auxiliary contact of substituting disconnector of BBx [BI_52a_DSBBx_BT] is

energized, the BC breaker is substituting through BBx, and the BC current will be calculated in

discriminating zone differential current of BBx.

When BC breaker is used to substitute any of feeder breakers, some protection elements (such as

SOTF protection, EFP and BFP) of BC will quit automatically, but overcurrent protection and pole

disagreement protection are still reserved, which can be used as the protection function of the

substituted feeder. In addition, some functions for BC breaker is used as a tie breaker connecting

two busbars are also quit (such as: tripping BC breaker when busbar internal fault happens).

Note!

[EBI_NegPolar_CT_BT] should be energized prior to [EBI_BT_BC].

1. Energizing the binary input [EBI_NegPolar_CT_BT]

*

BB2

BB1

BC

* * * *

Transfer Busbar

Figure 3.8-1 BC breaker substituting through BB2

The polarity mark of BC CT is on the feeder side, the binary input [EBI_NegPolar_CT_BT] should

be energized. Negative value of BC current will be calculated in check zone differential current and

discriminating zone differential current of BB2.

2. De-energizing the binary input [EBI_NegPolar_CT_BT]

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*

BB2

BB1

BC1

* * * *

Transfer Busbar

Figure 3.8-2 BC breaker substituting through BB1

The polarity mark of BC CT is on the busbar side, the binary input [EBI_NegPolar_CT_BT] should

not be energized. Positve value of BC current will be calculated in check zone differential current

and discriminating zone differential current of BB1.

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4 Supervision


Date: 2012-08-31

4 Supervision

Table of Contents

4 Supervision ..................................................................................... 4-a

4.1 Overview .......................................................................................................... 4-1

4.2 Protective Device Supervision ....................................................................... 4-1

4.2.1 Hardware supervision .......................................................................................................... 4-1

4.2.2 Opto-coupler Power Supervision ......................................................................................... 4-1

4.2.3 Binary output supervision .................................................................................................... 4-1

4.2.4 Binary input supervision ...................................................................................................... 4-1

4.2.5 Setting supervision .............................................................................................................. 4-2

4.2.6 Test Mode Supervision ........................................................................................................ 4-2

4.2.7 Hardware Configuration Supervision................................................................................... 4-2

4.3 AC Circuit Supervision ................................................................................... 4-2

4.3.1 Voltage and current drift supervision and auto-adjustment ................................................. 4-2

4.3.2 Sample supervision ............................................................................................................. 4-2

4.4 Secondary Circuit Supervision ...................................................................... 4-2

4.4.1 Voltage Transformer Supervision (VTS) .............................................................................. 4-2

4.4.2 Current Transformer Supervision (CTS) ............................................................................. 4-2

4.4.3 Disconnector position supervision ....................................................................................... 4-3

4.4.4 BC breaker supervision ....................................................................................................... 4-3

4.5 Handle Alarm ................................................................................................... 4-3

4.5.1 List of self-supervision report............................................................................................... 4-3

4.5.2 Self-Supervision Alarm List.................................................................................................. 4-7

4.5.3 Repairmen suggestion of self-supervision report ............................................................... 4-11

Table of Tables

Table 4.5-1 Self-supervision report ........................................................................................... 4-3

Table 4.5-2 Equipment self-check alarm list ................................................................................ 4-7

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Table 4.5-3 Repairmen suggestion .......................................................................................... 4-11

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Date: 2012-08-31

4.1 Overview

PCS-915 is a microprocessor based busbar protection which can provide successive automatic

supervision to the protected object to ensure the power system can quickly restore from any fault

to normal state. When the device is in energizing process before the LED HEALTHY is lightened,

operators need to check the device operating state to ensure the automatic supervision function

can work normally.

The device will be blocked if there is any severe problem occurs in the hardware module or

software program. Before reboot the relay, users are recommended to solve the problem or return

the feedbacks to NR.

When a failure is detected in the system, the fault message will be displayed on the LCD and the

corresponding LED will be lightened. Meanwhile, the corresponding alarm output contacts will be

energized and the failure alarm will be recorded and stored in the device. Users can either view

the fault report directly on LCD or print out the report.

The automatic supervision of PCS-915 has advantages in independent operation to the protection

functions and is capable to identify the fault location when the fault occurs in the system.

4.2 Protective Device Supervision

4.2.1 Hardware supervision

The automatic supervision function can provide monitoring of all chips on protection DSP module

and fault detector DSP module to prevent any damaged or errors during the normal operation. The

alarm signals [Alm_DSP_ProtBrd] or [Alm_DSP_FDBrd] will be issued if any damages or errors

are dectected and the device will be blocked.

4.2.2 Opto-coupler Power Supervision

The automatic supervision can continuously monitor the positive power supply of opto-coupler, if a

failure or damage is detected, then the alarm signal [Alm_Pwr_BI_Bxx] will be issued (xx is the slot

No. of corresponding binary input module).

4.2.3 Binary output supervision

The state of binary outputs of each BO module is continually monitored. If any abnormality is

detected, the alarm signals [Alm_Output_Bxx] will be issued with device being blocked (xx is the

slot No. of corresponding BO module).

4.2.4 Binary input supervision

The state of binary inputs detected by protection DSP module and fault detector DSP module

should be the same. Otherwise, the protective device will be blocked.

If binary input [BI_Blk_BBP] is energized for over 1s, the alarm [Alm_Blk_BBP] will be issued and

the blocking for BBP will be released.

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If any binary input for initiating feeder BFP is energized for over 10s, the alarm

[Alm_PersistFD_BFP] will be issued with BFP blocked.

4.2.5 Setting supervision

PCS-915 has 10 setting groups, while only one group is active at one time. The settings of active

setting group are checked, if any is out of setting scopes, a corresponding alarm signal

[Alm_Setting_Out-of-Range] will be issued with the protective device be blocked.

If the EEPROM on protection DSP module or fault detector DSP module is damaged, it will lead to

any summation error of all setting groups, the alarms [Alm_Setting] and [Alm_Setting_FDBrd] or

[Alm_Setting_ProtBrd] will be issued with the protective device blocked.

4.2.6 Test Mode Supervision

When protection equipment is set to test mode by configuring the corresponding logic setting, the

alarm signal [Alm_BO_Test] is issued without blocking equipment.

4.2.7 Hardware Configuration Supervision

04 - pcs915a busbar protection

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