gas insulated switchgear for substations - high voltage

2/28 Siemens Power Engineering Guide · Transmission and Distribution · 4th Edition

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Gas-Insulated Switchgear for Substations

Introduction

Common characteristic features ofswitchgear installation

Because of its small size and outstandingcompatibility with the environment, SF6 -insulated switchgear (GIS) is gaining con-stantly on other types. Siemens has beena leader in this sector from the very start.The concept of SF6 - insulated metal-en-closed high-voltage switchgear has proveditself in more than 70,000 bay operatingyears in over 6,000 installations in all partsof the world. It offers the following out-standing advantages.

Minimal space requirements

The availability and price of land play animportant part in selecting the type ofswitchgear to be used. Siting problemsarise in■ Large towns■ Industrial conurbations■ Mountainous regions with narrow

valleys■ Underground power stationsIn cases such as these, SF6-insulatedswitchgear is replacing conventionalswitchgear because of its very small spacerequirements.

Full protectionagainst contact with live parts

The all-round metal enclosure affordsmaximum safety for personnel underall operating and fault conditions.

Protection against pollution

Its metal enclosure fully protects theswitchgear interior against environmentaleffects such as salt deposits in coastalregions, industrial vapors and precipitates,as well as sandstorms. The compactswitchgear can be installed in buildingsof uncomplicated design in order to mini-mize the cost of cleaning and inspectionand to make necessary repairs independ-ent of weather conditions.

Free choice of installation site

The small site area required for SF6-insu-lated switchgear saves expensive gradingand foundation work, e.g. in permafrostzones. Other advantages are the shorterection times and the fact that switchgearinstalled indoors can be serviced regard-less of the climate or the weather.

Protection of the environment

The necessity to protect the environmentoften makes it difficult to erect outdoorswitchgear of conventional design, where-as buildings containing compact SF6-insu-lated switchgear can almost always bedesigned so that they blend well with thesurroundings.SF6-insulated metal-enclosed switchgearis, due to the modular system, very flexibleand can meet all requirements of configu-ration given by network design and operat-ing conditions.

Each circuit-breaker bay includes the fullcomplement of disconnecting and ground-ing switches (regular or make-proof),instrument transformers, control and pro-tection equipment, interlocking and moni-toring facilities commonly used for thistype of installation (Fig. 39).Beside the conventional circuit-breakerbay, other arrangements can be suppliedsuch as single-bus, ring cable with load-breakswitches and circuit-breakers, single-busarrangement with bypass-bus, coupler andbay for triplicate bus. Combined circuit-breaker and load-break switch feeder, ringcable with load-break switches, etc. arefurthermore available for the 145 kV level.

Fig. 39: Typical circuit arrangements of SF6-switchgear

Adam Rowe

SMALL POWER 6

Siemens Power Engineering Guide · Transmission and Distribution · 4th Edition 2/29

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Main product range of GISfor substations

SF6 switchgear up to 550 kV(the total product range covers GIS from66 up to 800 kV rated voltage): Fig. 40.The development of the switchgear isalways based on an overall production con-cept, which assures the achievement ofthe high technical standards requiredof the HV switchgear whilst providing themaximum customer benefit.

This objective is attained only by incorpo-rating all processes in the quality manage-ment system, which has been introducedand certified according to DIN EN ISO9001 (EN 29001).Siemens GIS switchgear meets allthe performance, quality and reliabilitydemands such as:

Compact space-saving design

means uncomplicated foundations, a widerange of options in the utilization of space,less space taken up by the switchgear.

Fig. 40: Main product range

Minimal-weight construction

through the use of aluminum alloy and theexploitation of innovations in developmentsuch as computer-aided design tools.

Safe encapsulation

means an outstanding level of safetybased on new manufacturing methodsand optimized shape of enclosures.

Environmental compatibility

means no restrictions on choice of locationthrough minimal space requirement, ex-tremely low noise emission and effectivegas sealing system (leakage < 1% per yearper gas compartment).

Economical transport

means simplified and fast transport andreduced costs because of maximum possi-ble size of shipping units.

Minimal operating costs

means the switchgear is practically mainte-nance-free, e.g. contacts of circuit-breakersand disconnectors designed for extremelylong endurance, motor-operated mecha-nisms self-lubricating for life, corrosion-freeenclosure. This ensures that the first in-spection will not be necessary until after25 years of operation.

Reliability

means our overall product concept whichincludes, but is not limited to, the use offinite elements method (FEM), three-dimensional design programs, stereolitho-graphy, and electrical field developmentprograms assuring the high standard ofquality.

Smooth and efficientinstallation and commissioning

transport units are fully assembled andtested at the factory and filled with SF6 gasat reduced pressure. Plug connection of allswitches, all of which are motorized, fur-ther improves the speediness of site instal-lation and substantially reduces field wiringerrors.

Routine tests

All measurements are automatically docu-mented and stored in the EDP informationsystem, which enables quick access tomeasured data even if years have passed.

For further information please contact:

Fax: ++49-9131-7-34498e-mail: [email protected]

500

4480

5170

All dimensions in mm

Switchgear type 8DN8 8DN9 8DQ1

Details on page 2/30 2/31 2/32

Rated voltage [kV] up to 145 up to 245 up to 550

Rated power- [kV] up to 275 up to 460 up to 740frequencywithstand voltage

Rated lightning [kV] up to 650 up to 1050 up to 1800impulse withstandvoltage

Rated switching [kV] – up to 850 up to 1250impulse withstandvoltage

Rated (normal) current [A] up to 3150 up to 3150 up to 6300busbar

Rated (normal) current [A] up to 2500 up to 3150 up to 4000feeder

Rated breaking [kA] up to 40 up to 50 up to 63current

Rated short-time [kA] up to 40 up to 50 up to 63withstand current

Rated peak [kA] up to 108 up to 135 up to 170withstand current

Inspection [Years] > 25 > 25 > 25

Bay width [mm] 800 1200/1500 3600

4740

3470

3500

2850


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Fig. 41: Switchgear bay 8DN8 up to 145 kV

Fig. 42: 8DN8 switchgear for rated voltage 145 kV Fig. 43

SF6-insulated switchgearup to 145 kV, type 8DN8

Three-phase enclosures are used for type8DN8 switchgear in order to achieve ex-tremely low component dimensions. Thelow bay weight ensures minimal floorload-ing and eliminates the need for complexfoundations. Its compact dimensions andlow weight enable it to be installed almostanywhere. This means that capital costs canbe reduced by using smaller buildings, orby making use of existing ones, for instancewhen medium voltage switchgearis replaced by 145 kV GIS.The bay ist based on a circuit-breakermounted on a supporting frame (Fig. 41).A special multifunctional cross-couplingmodule combines the functions of the dis-connector and earthing switch in a three-position switching device. It can be used as■ an active busbar with integrated discon-

nector and work-in-progress earthingswitch (Fig. 41/Pos. 3 and 4),

■ outgoing feeder module with integrateddisconnector and work-in-progress earth-ing switch (Fig. 41/Pos. 5),

■ busbar sectionalizer with busbar earthing.For cable termination, a cable terminationmodule can be equipped with either con-ventional sealing ends or the latest plug-inconnectors (Fig. 41/Pos. 9). Flexible single-pole modules are used to connect overheadlines and transformers by using a splittingmodule which links the 3-phase encapsulatedswitchgear to the single pole connections.Thanks to the compact design, up to threecompletely assembled and works-testedbays can be shipped as one transport unit.Fast erection and commissioning on siteensure the highest possible quality.The feeder control and protection can belocated in a bay-integrated local controlcubicle, mounted in the front of each bay(Fig. 42). It goes without saying that wesupply our gas-insulated switchgear with alltypes of currently available bay control sys-tems – ranging from contactor circuit con-trols to digital processor bus-capable baycontrol systems, for example the modernSICAM HV system based on serial buscommunication. This system offers■ Online diagnosis and trend analysis ena-

bling early warning, fault recognition andcondition monitoring.

■ Individual parameterization, ensuring thebest possible incorporation of customizedcontrol facilities.

■ Use of modern current and voltage sensors.This results in a longer service life and loweroperating costs, in turn attaining a consider-able reduction in life cycle costs.

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Gas-tight bushingGas-permeable bushing

1 Interrupter unit of thecircuit-breaker

2 Spring-stored energymechanism with circuit-breaker control unit

3 Busbar I with disconnectorand earthing system

4 Busbar II with disconnectorand earthing system

5 Outgoing feeder modulewith disconnector andearthing switch

6 Make-proof earthing switch(high-speed)

7 Current transformer8 Voltage transformer9 Cable sealing end

10 Integrated local control cubicle

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SF6-insulated switchgearup to 245 kV, type 8DN9

The clear bay configuration of the light-weight and compact 8DN9 switchgear isevident at first sight. Control and monitoringfacilities are easily accessible in spite ofthe compact design of the switchgear.The horizontally arranged circuit-breakerforms the basis of every bay configuration.The operating mechanism is easily acces-sible from the operator area. The other baymodules – of single-phase encapsulateddesign like the circuit-breaker module – arelocated on top of the circuit-breaker. Thethree-phase encapsulated passive busbaris partitioned off from the active equipment.Thanks to “single-function” assemblies(assignment of just one task to each module)and the versatile modular structure, evenunconventional arrangements can be setup out of a pool of only 20 different modules.The modules are connected to each otherby a standard interface which allows anextensive range of bay structures. Theswitchgear design with standardized mod-ules and the scope of services mean thatall kinds of bay structures can be set up ina minimal area.The compact design permits the supply ofdouble bays fully assembled, tested in thefactory and filled with SF6 gas at reducedpressure, which assures smooth and effi-cient installation and commissioning.The following major feeder control levelfunctions are performed in the local controlcubicle for each bay, which is integrated inthe operating front of the 8DN9 switch-gear:■ Fully interlocked local operation and

state-indication of all switching devicesmanaged reliably by the Siemens digitalswitchgear interlock system

■ Practical dialog between the digital feed-er protection system and central proces-sor of the feeder control system

■ Visual display of all signals required foroperation and monitoring, together withmeasured values for current, voltage andpower

■ Protection of all auxiliary current andvoltage transformer circuits

■ Transmission of all feeder information tothe substation control and protectionsystem

Factory assembly and tests are significantparts of the overall production conceptmentioned above. Two bays at a time un-dergo mechanical and electrical testingwith the aid of computer-controlled stands. Fig. 45: 8DN9 switchgear for

rated voltage 245 kV

Fig. 44: Switchgear bay 8DN9 up to 245 kV

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Gas-tight bushingGas-permeable bushing

1 Circuit-breaker interrupter unit2 Spring-stored energy

mechanism with circuit-breakercontrol unit

3 Busbar disconnector I4 Busbar I5 Busbar disconnector II6 Busbar II7 Earthing switch

(work-in-progress)

8 Earthing switch(work-in-progress)

9 Outgoing-disconnector10 Make-proof earthing switch

(high-speed)11 Current transformer12 Voltage transformer13 Cable sealing end14 Integrated local control cubicle

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SF6-insulated switchgearup to 550 kV, type 8DQ1

The GIS type 8DQ1 is a modular switch-gear system for high power switching sta-tions with individual enclosure of all mod-ules for the three-phase system.The base unit for the switchgear forms ahorizontally arranged circuit-breaker on topof which are mounted the housings con-taining disconnectors, grounding switches,current transformers, etc. The busbar mod-ules are also single-phase encapsulatedand partitioned off from the active equip-ment.As a matter of course the busbar modulesof this switchgear system are passiveelements, too.Additional main characteristic features ofthe switchgear installation are:■ Circuit-breakers with two interrupter

units up to operating voltages of 550 kVand breaking currents of 63 kA (from63 kA to 100 kA, circuit-breakers withfour interrupter units have to be con-sidered)

■ Low switchgear center of gravity bymeans of circuit-breaker arranged hori-zontally in the lower portion

■ Utilization of the circuit-breaker trans-port frame as supporting device for theentire bay

■ The use of only a few modules andcombinations of equipment in one enclo-sure reduces the length of sealing facesand consequently lowers the risk ofleakage

Fig. 47: 8DQ1 switchgear for rated voltage 420 kV


Fig. 46: Switchgear bay 8DQ1 up to 550 kV

10 Grounding switch11 Current transformer12 Cable sealing end13 Local control cubicle14 Gas monitoring unit

(as part of control unit)15 Circuit-breaker control unit16 Electrohydraulic operating unit17 Oil tank18 Hydraulic storage cylinder

1 Circuit-breaker2 Busbar disconnector I3 Busbar I4 Busbar disconnector II5 Busbar II6 Grounding switch7 Voltage transformer8 Make-proof grounding

switch9 Cable disconnector

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Some examples for specialarrangement

Gas-insulated switchgear – usually accom-modated in buildings (as shown in a tower-type substation) – is expedient wheneverthe floor area is very expensive or restrict-ed or whenever ambient conditions neces-sitate their use (Fig. 50, page 2/34).For smaller switching stations, or in casesof expansion when there is no advantagein constructing a building, a favorablesolution is to install the substation in acontainer (Fig. 49).

Mobile containerized switchgear –even for high voltage

At medium-voltage levels, mobile contain-erized switchgear is the state of the art.But even high-voltage switching stationscan be built in this way and economicallyoperated in many applications.The heart is the metal-enclosed SF6-in-sulated switchgear, installed either in asheet-steel container or in a block housemade of prefabricated concrete elements.In contrast to conventional stationaryswitchgear, there is no need for complicat-ed constructions; mobile switching sta-tions have their own ”building“.

Mobile containerized switching stationscan be of single or multi-bay design usinga large number of different circuits andarrangements. All the usual connectioncomponents can be employed, such asoutdoor bushings, cable adapter boxes andSF6 tubular connections. If necessary, allthe equipment for control and protectionand for the local supply can be accommo-dated in the container. This allows exten-

sively independent operation of the instal-lation on site. Containerized switchgear ispreassembled in the factory and ready foroperation. On site, it is merely necessaryto set up the containers, fit the exteriorsystem parts and make the external con-nections. Shifting the switchgear assemblywork to the factory enhances the qualityand operational reliability. Mobile container-ized switchgear requires little space andusually fits in well with the environment.Rapid availability and short commissioningtimes are additional, significant advantagesfor the operators. Considerable cost re-ductions are achieved in the planning, con-struction work and assembly.Building authority approvals are either notrequired or only in a simple form. The in-stallation can be operated at various loca-tions in succession, and adaptation to localcircumstances is not a problem. These arethe possible applications for containerizedstations:■ Intermediate solutions for the

modernization of switching stations■ Low-cost transitional solutions when

tedious formalities are involved in thenew construction of transformer sub-stations, such as in the procurement ofland or establishing cable routes

■ Quick erection as an emergency stationin the event of malfunctions in existingswitchgear

■ Switching stations for movable, geo-thermal power plants

GIS up to 245 kV in a standard container

The dimensions of the 8DN9 switchgearmade it possible to accommodate all activecomponents of the switchgear (circuit-breaker, disconnector, grounding switch)and the local control cabinet in a standardcontainer.The floor area of 20 ft x 8 ft complieswith the ISO 668 standard. Although thecontainer is higher than the standarddimension of 8 ft, this will not cause anyproblems during transportation as provenby previously supplied equipment.German Lloyd, an approval authority, hasalready issued a test certificate for an evenhigher container construction.The standard dimensions and ISO cornerfittings will facilitate handling during trans-port in the 20 ft frame of a container shipand on a low-loader truck.Operating staff can enter the containerthrough two access doors.

Rent a GIS

Containerized gas-insulated high voltagesubstations for hire are now available. Inthis way, we can step into every breach,instantly and in a remarkably cost-effectivemanner.Whether for a few weeks, months or even2 to 3 years, a fair rent makes our InstantPower Service unbeatably economical.

Fig. 48: Containerized 8DN9 switchgear with stub feed in this example

Fig. 49: 8DN9 switchgear bay in a container

7 Current transformer 8 Outgoing

disconnector 9 Make-proof earthing

switch10 Voltage transformer11 Outdoor termination

1 Cable termination2 Make-proof earthing

switch3 Outgoing

disconnector4 Earthing switch5 Circuit breaker6 Earthing switch

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Fig. 50: Special arrangement for limited space. Sectional view of a building showing the compact nature ofgas-insulated substations

Specification guide formetal-enclosed SF6-insulatedswitchgear

The points below are not considered tobe comprehensive, but are a selection ofthe important ones.

General

These specifications cover the technicaldata applicable to metal-enclosed SF6 gas-insulated switchgear for switching anddistribution of power in cable and/or over-head line systems and at transformers.Key technical data are contained in thedata sheet and the single-line diagramattached to the inquiry.A general “Single-line diagram” and asketch showing the general arrangementof the substation and the transmission lineexist and shall form part of a proposal.The switchgear quoted shall be completeto form a functional, safe and reliable sys-tem after installation, even if certain partsrequired to this end are not specificallycalled for.

Applicable standards

All equipment shall be designed, built,tested and installed to the latest revisionsof the applicable IEC 60 standards (IECPubl. 60517 “High-voltage metal-enclosedswitchgear for rated voltages of 72.5 kVand above”, IEC Publ. 60129 “Alternatingcurrent disconnectors (isolators) andgrounding switches”, IEC Publ. 60056“High-voltage alternating-current circuit-breakers”), and IEC Publ. 60044 for instru-ment transformers.

Local conditions

The equipment described herein will beinstalled indoors. Suitable lightweight,prefabricated buildings shall be quoted ifavailable from the supplier.Only a flat concrete floor will be providedby the buyer with possible cutouts in caseof cable installation. The switchgear shallbe equipped with adjustable supports(feet). If steel support structures are re-quired for the switchgear, these shall beprovided by the supplier.For design purposes indoor temperaturesof – 5 °C to +40 °C and outdoor temper-atures of – 25 °C to +40 °C shall be consid-ered.For parts to be installed outdoors (over-head line connections) the applicable con-ditions in IEC Publication 60517 shall alsobe observed.

Air con-ditioningsystem

26.90

23.20

Relay room

Groundingresistor

Shuntreactor

13.8 kVswitchgear

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11.50

8.90Cable duct

40 MVA transformer

Radiators

Compensator

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–1.50

Gas-insulatedswitchgear type8DN9

All dimensions in m


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Work, material and design

Aluminium or aluminium alloys shall beused preferabely for the enclosures.Maximum reliability through minimumamount of erection work on site is re-quired. Subassemblies must be erectedand tested in the factory to the maximumextent. The size of the subassemblies shallbe limited only by the transport conditions.The material and thickness of the enclo-sure shall be selected to withstand an in-ternal arc and to prevent a burn-through orpuncturing of the housing within the firststage of protection, referred to a short-circuit current of 40 kA.Normally exterior surfaces of the switch-gear shall not require painting. If done foraesthetic reasons, surfaces shall be appro-priately prepared before painting, i.e. allenclosures are free of grease and blasted.Thereafter the housings shall be paintedwith no particular thickness required butto visually cover the surface for decorativereasons only. The interior color shall belight (white or light grey).All joints shall be machined and all cast-ings spotfaced for bolt heads, nuts andwashers.Assemblies shall have reliable provisionsto absorb thermal expansion and contrac-tions created by temperature cycling. Forthis purpose metal bellows-type compen-sators shall be installed. They must beprovided with adjustable tensioners.All solid post insulators shall be providedwith ribs (skirts).For supervision of the gas within the en-closures, density monitors with electricalcontacts for at least two pressure levelsshall be installed. The circuit-breakers,however, might be monitored by densitygauges fitted in circuit-breaker controlunits.The manufacturer assures that the pres-sure loss within each individual gas com-partment – and not referred to thetotal switchgear installation only – will benot more than 1% per year per gas com-partment.

Each gas-filled compartment shall beequipped with static filters of a capacityto absorb any water vapor penetrating intothe switchgear installation over a periodof at least 25 years.Long intervals between the necessary in-spections shall keep the maintenance costto a minimum. A minor inspection shallonly become necessary after ten years anda major inspection preferably after a periodexceeding 25 years of operation, unlessthe permissible number of operations ismet at an earlier date.

Arrangement and modules

ArrangementThe arrangement shall be single-phase orthree-phase enclosed.The assembly shall consist of completelyseparate pressurized sections designedto minimize the risk of damage to person-nel or adjacent sections in the event of afailure occurring within the equipment.Rupture diaphragms shall be provided toprevent the enclosures from uncontrolledbursting and suitable deflectors provideprotection for the operating personnel.In order to achieve maximum operatingreliability, no internal relief devices maybe installed because adjacent compart-ments would be affected.Modular design, complete segregation,arc-proof bushings and “plug-in” connec-tion pieces shall allow ready removal ofany section and replacement with mini-mum disturbance of the remaining pres-surized switchgear.

BusbarsAll busbars shall be three-phase or single-phase enclosed and be plug-connectedfrom bay to bay.

Circuit-breakersThe circuit-breaker shall be of the singlepressure (puffer) type with one interrupterper phase*. Heaters for the SF6 gas arenot permitted.The arc chambers and contacts of thecircuit-breaker shall be freely accessible.The circuit-breaker shall be designed tominimize switching overvoltages and alsoto be suitable for out-of-phase switching.The specified arc interruption performancemust be consistent over the entire operat-ing range, from line-charging currents tofull short-circuit currents.

The circuit breaker shall be designed towithstand at least 18–20 operations(depending on the voltage level) at fullshort-circuit rating without the necessityto open the circuit-breaker for service ormaintenance.The maximum tolerance for phase dis-agreement shall be 3 ms, i.e. until the lastpole has been closed or opened respec-tively after the first.A standard station battery required forcontrol and tripping may also be used forrecharging the operating mechanism.The energy storage system (hydraulic orspring operating system) will hold suf-ficient energy for all standard IEC close-open duty cycles.The control system shall provide alarmsignals and internal interlocks, but inhibittripping or closing of the circuit-breakerwhen there is insufficient energy capacityin the energy storage system, or theSF6 density within the circuit-breaker hasdropped below a minimum permissiblelevel.

DisconnectorsAll isolating switches shall be of the single-break type. DC motor operation (110, 125,220 or 250 V), completely suitable for re-mote operation, and a manual emergencydrive mechanism is required.Each motor-drive shall be self-containedand equipped with auxiliary switches inaddition to the mechanical indicators.Life lubrication of the bearings is required.

Grounding switchesWork-in-progress grounding switches shallgenerally be provided on either side of thecircuit-breaker. Additional grounding switch-es may be used for the grounding of bussections or other groups of the assembly.DC motor operation (110, 125, 220 or250 V), completely suitable for remoteoperation, and a manual emergency drivemechanism is required.Each motor drive shall be self-containedand equipped with auxiliary positionswitches in addition to the mechanical in-dicators. Life lubrication of the bearingsis required.

* two interrupters for voltages exceeding 245 kV


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Fig. 52: Cable termination module –Cable termination modules conforming to IEC areavailable for connecting the switchgear to high-volt-age cables. The standardized construction of thesemodules allows connection of various cross-sectionsand insulation types. Parallel cable connections forhigher rated currents are also possible using thesame module.

Fig. 53: Outdoor termination module –High-voltage bushings are used for transition fromSF6-to-air as insulating medium. The bushings can bematched to the particular requirements with regardto arcing and creepage distances. The connectionwith the switchgear is made by means of variable-design angular-type modules.

Fig. 51: Three phase cable termination module.Example for plug-in type cables.

Make-proof high-speed grounding switchesshall generally be installed at cable andoverhead-line terminals. DC motor opera-tion (110, 125, 220 or 250 V), completelysuitable for remote operation, and a manu-al emergency drive mechanism is required.Each motor drive shall be self-containedand equipped with auxiliary positionswitches in addition to the mechanical in-dicators. Life lubrication of the bearingsis required.These switches shall be equipped witha rapid closing mechanism to provide fault-making capability.

Instrument transformersCurrent transformers (CTs) shall be of thedry-type design not using epoxy resin asinsulation material. Cores shall be providedwith the accuracies and burdens as shownon the SLD. Voltage transformers shall beof the inductive type, with ratings up to200 VA. They shall be foil-gas-insulated.

Cable terminations

Single or three-phase, SF6 gas-insulated,metal-enclosed cable-end housings shallbe provided. The stress cone and suitablesealings to prevent oil or gas from leakinginto the SF6 switchgear are part of thecable manufacturer’s supply. A mating con-nection piece, which has to be fitted to thecable end, shall be made available by theswitchgear supplier.The cable end housing shall be suitablefor oil-type, gas-pressure-type and plastic-insulated (PE, PVC, etc.) cables as speci-fied on the SLD, or the data sheets.Facilities to safely isolate a feeder cableand to connect a high-voltage test cableto the switchgear or the cable shall beprovided.

Overhead line terminations

Terminations for the connection of over-head lines shall be supplied completewith SF6-to-air bushings, but without lineclamps.

Fig. 55: Transformer termination modules

Fig. 54: Transformer/reactor termination module –These termination modules form the direct connec-tion between the GIS and oil-insulated transformersor reactance coils. They can be matched economi-cally to various transformer dimensions by way ofstandardized modules.

Control

An electromechanical or solid-state inter-locking control board shall be supplied as astandard for each switchgear bay. This fail-safe interlock system will positively pre-vent maloperations. Mimic diagrams andposition indicators shall give clear demon-stration of the operation to the operatingpersonnel.Provisions for remote control shall besupplied.


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Fig. 56: The modular system of the 8DQ1 switchgear enables all conceivable customer requirements to be metwith just a small number of components

Tests required

Partial discharge tests

All solid insulators fitted into the switch-gear shall be subjected to a routine partialdischarge test prior to being installed.No measurable partial discharge is allowedat 1.1 line-to-line voltage (approx. twicethe phase-to-ground voltage). This test en-sures maximum safety against insulatorfailure, good long-term performance andthus a very high degree of reliability.

Pressure tests

Each cast aluminium enclosure of theswitchgear shall be pressure-tested to atleast double the service pressure.

Leakage tests

Leakage tests performed on the subassem-blies shall ensure that the flanges and coverfaces are clean, and that the guaranteedleakage rate will not be exceeded.

Power frequency tests

Each assembly shall be subjected to pow-er-frequency withstand tests to verify thecorrect installation of the conductors andalso the fact that the insulator surfaces areclean and the switchgear as a whole is notpolluted inside.

Additional technical data

The supplier shall point out all dimensions,weights and other applicable data of theswitchgear that may affect the local con-ditions and handling of the equipment.Drawings showing the assembly of theswitchgear shall be part of the quotation.

Instructions

Detailed instruction manuals about instal-lation, operation and maintenance of theequipment shall be supplied by the con-tractor in case of an order.

Scope of supply

For all types of GIS Siemens suppliesthe following items and observes theseinterface points:■ Switchgear bay with circuit-breaker inter-

rupters, disconnectors and groundingswitches, instrument transformers, andbusbar housings as specified. For thedifferent feeder types, the following lim-its apply:– Overhead line feeder:

the connecting stud at the SF6-to-airbushing without the line clamp.

– Cable feeder:according to IEC 60859 the termina-tion housing, conductor coupling, andconnecting plate are part of the GISdelivery, while the cable stress conewith matching flange is part of the ca-ble supply (see Fig. 52 on page 2/36).

– Transformer feeder:connecting flange at switchgear bayand connecting bus ducts to trans-former including any expansion jointare delivered by Siemens. The SF6-to-oil bushings plus terminal enclo-sures are part of the transformerdelivery, unless agreed otherwise(see Fig. 54 on page 2/36)*.

■ Each feeder bay is equipped withgrounding pads. The local groundingnetwork and the connections to theswitchgear are in the delivery scopeof the installation contractor.

■ Initial SF6-gas filling for the entireswitchgear as supplied by Siemens isincluded. All gas interconnections fromthe switchgear bay to the integral gasservice and monitoring panel are sup-plied by Siemens as well.

■ Hydraulic oil for all circuit-breaker operat-ing mechanisms is supplied with theequipment.

■ Terminals and circuit protection for aux-iliary drive and control power are pro-vided with the equipment. Feeder cir-cuits and cables, and installation materialfor them are part of the installation con-tractor’s supply.

■ Local control, monitoring, and interlock-ing panels are supplied for each circuit-breaker bay to form completely oper-ational systems. Terminals for remotemonitoring and control are provided.

■ Mechanical support structures aboveground are supplied by Siemens; em-bedded steel and foundation work ispart of the installation contractor’s scope.

* Note: this interface point should always be closelycoordinated between switchgear manufacturer andtransformer supplier.

gas insulated switchgear for substations - high voltage

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