Siemens Power Engineering Guide Transmission Distribution

Power Engineering GuideTransmission and Distribution

Siemens Power Engineering Guide Transmission & Distribution

Your local representative:

Distributed by:Siemens AktiengesellschaftPower Transmission and Distribution GroupInternational Business Development,Dept. EV IBD

P.O. Box 3220D-91050 ErlangenPhone: ++49-9131-73 4540Fax: ++49-9131-73 4542

Power Transmission and Distributiongroup online:http://www.siemens.ev.de

Power Engineering GuideTransmission and Distribution For further information to each chapter:

High VoltageDesign of Air-insulated Outdoor SubstationsFax.: ++49-9131-73 18 58

Gas-insulated Swichgear for SubstationsFax.: ++49-9131-73 46 62

Gas-insulated Transmission LinesFax.: ++49-9131-734490Circuit Breakers for 72 kV up to 800 kVFax.: ++49-3 03 86-2 58 67

High-voltage Direct Current TransmissionFax.: ++49-9131-73 35 66

Power Compensation in Transmission SystemsFax.: ++49-9131-73 45 54Power Compensation in Distribution SystemsFax.: ++49-9131-73 13 74

Surge ArrestersFax.: ++49-3 03 86-2 67 21

Worldwide Service for High- and Medium-voltage Switchgear and SubstationsFax.: ++49-9131-73 44 49

Medium VoltagePrimary DistributionFax.: ++49-9131-73 46 39Containerized SwitchgearFax.: ++49-68 94-89 12 94

Secondary DistributionFax.: ++49-9131-73 46 36

Medium Voltage DevicesFax.: ++49-9131-73 46 54

Low VoltageSIVACONFax.: ++49-3 41-4 47 04 00

TransformersDistribution TransformersFax.: ++49-70 21-50 85 48

Power TransformersFax.: ++49-9 11-4 34 2147

Power CablesLow- and Medium-Voltage CablesFax.: ++49-9131-73 24 55 and ++49-9131-7310 92High- and Extra High CablesFax.: ++49-9131-73 47 44

Accessories for Low- and Medium-Voltage CablesFax.: ++49-23 31-35 7118

Accessories for High-Voltage CablesFax.: ++49-23 31-35 71 18

Protection and Substation ControlFax.: ++49-911-4 33-85 89

Power Systems ControlSCADA/EMS/DMSFax.: ++49-9 11-4 33-81 22Control Room TechnologyFax.: ++49-911-433-8183

Power Network TelecommunicationFax.: ++49-89-722-2 44 53 or ++49-89-7 22-4 1982

Energy MeteringFax.: ++49-9 11-4 33-80 37

Overhead Power LinesFax.: ++49-9131-72 95 93

System PlanningFax.: ++49-9131-73 44 45

High-Voltage Power Transmission SystemsFax.: ++49-9131-734672


Contents

High Voltage

Medium Voltage

Low Voltage

Transformers

Power Cables

Protection and Substation Control

Power Systems Control

Energy Metering

Overhead Power Lines

System Planning

High-Voltage Power Transmission Systems

Annex: Conversion Factors and TablesSupplement: Facts and Figures

Adress Index of Local Siemens Partners

ForewordGeneral Introduction


Quality and Environmental Policy

Quality Our first priority

Transmission and distribution equipmentfrom Siemens means worldwide activitiesin engineering, design, development, man-ufacturing and service.The Power Transmission and DistributionGroup of Siemens AG, with all of its divi-sions and relevant locations, has beenawarded and maintains certification toDIN/ISO 9001 (EN 29001).

Certified qualitySiemens Quality Management Systemgives our customers confidence in thequality of Siemens products and services.Certified to be in compliance withDIN/ISO 9001 (EN 29001), it is the reg-istered proof of our reliabilty.


Siemens AG is one of the worldsleading international electrical andelectronics companies.With 370 000 employees in more than190 countries worldwide, the companyis divided into various groups.The Power Transmission and Distribu-tion Group of Siemens with 22 500employees around the world plans,develops, designs, manufactures andmarkets products, systems and com-plete turn-key electrical infrastructureinstallations. These involve high-voltageand HVDC, medium-voltage and low-voltage components and systems,switchyards, switchgear and switch-boards, transformers, cables, telecon-trol systems and protection relays,network and substation control, power-factor correction and load-flow man-agement system. Also included are therequired software, application engi-neering and technical services.The group owns a growing number ofengineering and manufacturing facili-ties. Presently we account for 57 plantsand more than 70 joint ventures inmore than 100 countries throughout theworld. All plants are, or are in the pro-cess of being certified to ISO 9000/9001practices. This is of significant benefitfor our customers. Our local manufac-turing capability makes us strong inglobal sourcing, since we manufactureproducts to IEC as well as ANSI/NEMAstandards in plants at various locationsaround the world.

This Power Engineering Guide is de-vised as an aid to electrical engineerswho are engaged in the planning andspecifying of electrical power genera-tion, transmission, distribution, control,and utilization systems. Care has beentaken to include the most importantapplication, performance, physical andshipping data of the equipment listed inthe guide which is needed to performpreliminary layout and engineeringtasks for industrial- and utility-type in-stallations.The equipment listed in this guide isdesigned, rated, manufactured andtested in accordance with the Interna-tional Electrotechnical Commissions(IEC) recommendations.However, a number of standardizedequipment items in this guide are de-signed to take other national standardsinto account besides the above codes,and can be rated and tested to ANSI/NEMA, BS, CSA, etc. On top of that, wemanufacture a comprehensive range oftransmission and distribution equipmentspecifically to ANSI/NEMA codes andregulations.Two thirds of our product range isless than five years old. For our cus-tomers this means energy efficiency,environmental compatibility, reliabilityand reduced life cycle cost.For details, please see the individualproduct listings or inquire.Whenever you need additional infor-mation to select suitable products fromthis guide, or when questions abouttheir application arise, simply call yourlocal Siemens office.

Foreword by the Executive Management

Siemens Power Transmission and Dis-tribution Group is capable of providingeverything you would expect from anelectrical engineering company with aglobal reach.The Power Transmission and Distribu-tion Group is prepared and competent,to perform all tasks and activities in-volving transmission and distributionof electrical energy.Siemens Power Transmission andDistribution Group is active worldwidein the field of power systems and com-ponents, protection, management andcommunication systems (details shownin supplement Facts and Figures).Siemens service includes the settingup of complete turnkey installations,offers advice, planning, operation andtraining and provides expertise andcommitment as the complexity of thistask requires.Backed by the experience of worldwideprojects, Siemens can always offer itscustomers the optimum cost-effectiveconcept individually tailored to theirneeds.We are there wherever and when-ever you need us to help you buildplants better, cheaper and faster.

Klaus VogesVice President

Siemens AktiengesellschaftPower Transmission and Distribution


HV/HVtransformer level

feeding the subtrans-mission systems

Remotehydro-electricpower station

Generatorunit trans-former

Subtransmission system up to 145 kV

Regional supply system

Urban and/or industrialareas, also with localpower stations

Internal supply system

Large industrial com-plexes also with ownpower generation

Regional supply system

Rural areas

HV/MVStep-down trans-

former level

Interconnected transmission system up to 550 kV

Long-distance transmissionEHV AC up to 800 kV or HV DC

Power generation

Main substation with transformers up to 63 MVA

HV switchgear MV switchgear

General Introduction Transmission and Distribution

The sum of experience forintegral solutions

The worlds population is on the increaseand the demand for electrical energy inthe developing and newly industrializingnations is growing rapidly. Safe, reliableand environmentally sustainable powertransmission and distribution is thereforeone of the great challenges of our time.Siemens is making an important contribu-tion towards solving this task, with future-oriented technologies for the construction,modernization and expansion of powersystems at all voltage levels.The Siemens Power Engineering GuideTransmission and Distribution gives a shortsummary of the activities and products ofthe Power Transmission and DistributionGroup.Transmission and distribution networks arethe link between power generation and theconsumers, whose requirements for elec-trical energy determine the actual genera-tion. Industry, trade and commerce as wellas public services (transportation and com-munication systems including data pro-cessing), not to mention the private sector(households), are highly dependent upona reliable and adequate energy supply ofhigh quality at utmost economical condi-tions. These are the basic conditions forinstallation and operation of transmissionand distribution systems.

Transmission

The transmission of electrical energy fromthe generating plants, which are locatedunder the major constraints of primary en-ergy supply, cooling facilities and environ-mental impact, to the load centers, whoselocations are dictated by high-density urbanor industrial areas, requires a correspond-ingly extensive transmission system.These mostly interconnected systems, e.g.up to 550 kV, balance the daily and season-al differences between local available gen-erating capacity and load requirements andtransport the energy to the individual re-gions of demand. For long-distances and/orhigh-capacity transmission, extra-high-volt-age levels up to 800 kV or DC transmissionsystems are in use.In interconnected transmission systems,more and more substations for the sub-transmission systems with high-voltagelevels up to 145 kV are needed as closeas possible to the densely populated areas,feeding the regional supply of urban or in-dustrial areas. This calls for space-savingenclosed substations and the applicationof EHV and/or HV cable systems.

Fig. 1: Transmission: Principle configuration of transmission system


DistributionIn order to feed local medium-voltagedistribution systems of urban, industrial orrural distribution areas, HV/MV main sub-stations are connected to the subtransmis-sion systems. Main substations have tobe located next to the MV load center foreconomical reasons. Thus, the subtrans-mission systems of voltage levels up to145 kV have to penetrate even further intothe populated load centers.The far-reaching power distribution sys-tem in the load center areas is tailored ex-clusively to the needs of users with largenumbers of appliances, lamps, motordrives, heating, chemical processes, etc.Most of these are connected to the low-voltage level.The structure of the low-voltage distri-bution system is determined by load andreliability requirements of the consumers,as well as by nature and dimensions ofthe area to be served. Different consumercharacteristics in public, industrial andcommercial supply will need differentLV network configurations and adequateswitchgear and transformer layout. Espe-cially for industrial supply systems withtheir high number of motors and highcosts for supply interruptions, LV switch-gear design is of great importance forflexible and reliable operation.Independent from individual supply charac-teristics in order to avoid uneconomicalhigh losses, however, the substations withthe MV/LV transformers should be locatedas close as possible to the LV load centersand should therefore be of compact de-sign.The superposed medium-voltage systemhas to be configured to the needs of thesesubstations and the available sources(main substation, generation) and leadsagain to different solutions for urban orrural public supply, industry and large build-ing centers.Despite the individual layout of networks,common philosophy should be an utmostsimple and clear network design to obtainn flexible system operationn clear protection coordinationn short fault clearing time andn efficient system automation.The wide range of power requirementsfor individual consumers from a few kW tosome MW, together with the high numberof similar network elements, are the maincharacteristics of the distribution systemand the reason for the comparatively highspecific costs. Therefore, utmost standard-ization of equipment and use of mainte-nancefree components are of decisive im-portance for economical system layout.Siemens components and systems caterto these requirements based on worldwideexperience in transmission and distributionnetworks.

Fig. 2: Distribution: Principle configuration of distribution systems

Consumers

MV/LVtransformer

level

Low-voltage supply system

Large buildings withdistributed transformersvertical LV risers andinternal installation per floor

Industrial supply withdistributed transformerswith subdistribution boardand motor control center

Public supplywith pillars andhouse connectionsinternal installation

Local medium-voltage distribution system

Ring type

Connection oflarge consumer

Industrial supplyand large buildings

Public supply

Spot systemFeeder cable

Medium voltage substations

MV/LV substationlooped in MV cableby load-break switch-gear in differentcombinations forindividual substationdesign, transformersup to 1000 kVA

LV fuses

Circuitbreaker

Load-breakswitch

Consumer-connection substation loopedin or connected to feeder cable with circuitbreaker and load-break switches for connec-tion of spot system in different layout

Main substation with transformers up to 63 MVA

HV switchgear MV switchgear




Fig. 3: Protection, operation and control:Principle configuration of operation, protection and communication systems

Power system switchgear

SCADA functions Distributionmanagementfunctions

Network analysis

Power andschedulingapplications

Graficalinformationsystems

Training simulator

System coordination level

Control room equipment

Unit protection Overcurrent Distance Differential etc.

Unit switchinginterlocking

Control

Unit coordination levelOtherunit

Substation protection Substation control Data processing

Switchgearinterlocking

Data and signalinput/output

Automation

Otherunit

Substation coordination level

Power system substation

Power network telecommunication systemsOthersub-stations

Othersub-stations

Power line carriercommunication

Fiber-opticcommunication

Protection, operation and controlSafe, reliable and economical energy sup-ply is also a matter of fast, efficient andreliable system protection, data transmis-sion and processing for system operation.The components required for protectionand operation benefit from the rapid devel-opment of information and communicationtechnology.Modern digital relays provide extensivepossibilities of selective relay setting andprotection coordination for fast fault clear-ing and minimized interruption times. Ad-ditional extensive system data and infor-mation are generated as an essential basisfor systems supervision and control.Powerful data processing and manage-ment system have been developed. Modu-lar and open structures, full-graphics userinterface as well as state-of-the-art appli-cations are a matter of course.Siemens network control systems assurea complete overview of the current oper-ating conditions from the interconnectedgrid right up to the complete distributionnetwork. This simplifies system manage-ment and at the same time makes it morereliable and more economical. The openarchitecture of the power system controloffers great flexibility for expansion to meetall the demands made and can be integrat-ed into existing installations without anyproblems. Visualization of system behaviorand supply situation by advanced controlroom equipment assist the highly respon-sible function of systems operators.

Overall solutions System planning

Of crucial importance for the quality ofpower transmission and distribution is theintegration of diverse components to formoverall solutions.Especially in countries where the increasein power consumption is well above theaverage besides the installation of gener-ating capacity, construction and extensionof transmission and distribution systemsmust be developed simultaneously andtogether with equipment for protection,supervision and control. Also, for the exist-ing systems, changing load structure and/or environmental regulations, together withthe need for replacement of aged equip-ment will require new installations.Integral power network solutions are farmore than just a combination of productsand components. Peculiarities in urban de-velopment, protection of the countrysideand of the environment, and the suitabilityfor expansion and harmonious integrationin existing networks are just a few of thefactors which future-oriented power sys-tem planning must take into account.

1/2 Siemens Power Engineering Guide Transmission & Distribution

High-voltage Switchgear for Substations

Introduction

High-voltage substations form an importantlink in the power transmission chain be-tween generation source and consumer.Two basic designs are possible:

Air-insulated outdoor switchgearof open design (AIS)

AIS are favorably priced high-voltage sub-stations for rated voltages up to 800 kVwhich are popular wherever space restric-tions and environmental circumstances donot have to be considered. The individualelectrical and mechanical components ofan AIS installation are assembled on site.Air-insulated outdoor substations of opendesign are not completely safe to touchand are directly exposed to the effects ofweather and the environment (Fig. 1).

Gas-insulated indoor or outdoorswitchgear (GIS)

GIS compact dimensions and design makeit possible to install substations up to550 kV right in the middle of load centersof urban or industrial areas. Each circuit-breaker bay is factory assembled andincludes the full complement of isolatorswitches, grounding switches (regularor make-proof), instrument transformers,control and protection equipment, inter-locking and monitoring facilities commonlyused for this type of installation. Theearthed metal enclosures of GIS assurenot only insensitivity to contamination butalso safety from electric shock (Fig. 2).

Fig. 1: Outdoor switchgear

Fig. 2: GIS substations in metropolitan areas

1/3Siemens Power Engineering Guide Transmission & Distribution

High-voltage Switchgear for Substations

A special application of gas-insulatedequipment are: Gas-insulated transmis-sion lines (GIL)

Gas-insulated transmission lines (GIL)are always used where high-voltage cablescome up against the limits of their per-formance.High-voltage switchgear is normally com-bined with transformers and other equip-ment to complete transformer substationsin order ton Step-up from generator voltage level

to high-voltage system (MV/HV)n Transform voltage levels within the

high-voltage grid system(HV/HV)n Step-down to medium-voltage level

of distribution system (HV/MV)

The High-Voltage Division plans and con-structs individual high-voltage switchgearinstallations or complete transformer sub-stations, comprising high-voltage switch-gear, medium-voltage switchgear, majorcomponents such as transformers, andall ancillary equipment such as auxiliaries,control systems, protective equipment,etc., on a turnkey basis or even as generalcontractor.The spectrum of installations suppliedranges from basic substations with singlebusbar to regional transformer substationswith multiple busbars or 1 1/2 circuit-break-er arrangement for rated voltages up to800 kV, rated currents up to 8000 A andshort-circuit currents up to 100 kA, all overthe world.The services offered range from systemplanning to commissioning and after-salesservice, including training of customer per-sonnel.The process of handling such an installa-tion starts with preparation of a quotation,and proceeds through clarification of theorder, design, manufacture, supply andcost-accounting until the project is finallybilled. Processing such an order hinges onmethodical data processing that in turncontributes to systematic project handling.All these high-voltage installations havein common their high-standard of engi-neering, which covers power systems,steel structures, civil engineering, fire pre-cautions, environmental protection andcontrol systems (Fig. 3).

Every aspect of technology and each workstage is handled by experienced engineers.With the aid of high-performance computerprograms, e.g. the finite element meth-od (FEM), installations can be reliably de-signed even for extreme stresses, suchas those encountered in earthquake zones.All planning documentation is produced onmodern CAD systems; data exchange withother CAD systems is possible via stand-ardized interfaces.By virtue of their active involvement innational and international associations andstandardization bodies, our engineers arealways fully informed of the state of theart, even before a new standard or specifi-cation is published. Our own high-perform-ance, internationally accredited test labora-tories and a certified QA system testify tothe quality of our products and services.

Ancillaryequipment

Design

CivilEngineeringBuildings,roads,foundations

StructuralSteelworkGantries andsubstructures

Major com-ponents,e.g. trans-former

SubstationControlControl andmonitoring,measurement,protection, etc.

AC/DC

auxililiaries

Surge

diverter

s

Earth

ing

syste

m

Pow

er c

able

sC

ontr

ol a

ndsi

gnal

cab

les

Carrier-frequ.

equipment

Ventilation

Lightning

Environmentalprotection

Fireprotection

Fig. 3: Engineering of high-voltage switchgear

Milestones along the road tocertification:

n 1983: Introduction of a qualitysystem on the basis of Canadianstandard CSA Z299 Level 1.

n 1989: Certification in accordancewith DIN ISO 9001 by the GermanAssociation for Certification ofQuality Systems (DQS)

n 1992: Accreditation of the test labora-tories in accordance with DIN EN 45001by the German Accreditation Body forTechnology (DATech).

A worldwide network of liaison and salesoffices, along with the specialist depart-ments in Germany, support and advise ourcustomers in all matters of switchgeartechnology.Siemens has for many years been a lead-ing supplier of high-voltage equipment,regardless of whether AIS, GIS or GIL hasbeen concerned. For example, outdoorsubstations of longitudinal in-line designare still known in many countries underthe Siemens registered tradename Kiel-linie. Back in 1968, Siemens supplied theworlds first GIS substation using SF6 asinsulating and quenching medium. Gas-in-sulated transmission lines have featuredin the range of products since 1976.


Design of Air-insulated Outdoor Substations

Standards

Air-insulated outdoor substations of opendesign must not be touched. Therefore,air-insulated switchgear (AIS) is always setup in the form of a fenced-in electrical op-erating area, to which authorized personshave access only.Relevant IEC specifications apply to out-door switchgear equipment. Insulationcoordination, including minimum phase-to-phase and phase-to-ground clearances,is effected in accordance with IEC 71.Outdoor switchgear is directly exposed tothe effects of the environment such as theweather. Therefore it has to be designedbased on not only electrical but also envi-ronmental specifications.Currently there is no international standardcovering the setup of air-insulated outdoorsubstations of open design. Siemens de-signs AIS in accordance with DIN/VDEstandards, in line with national standardsor customer specifications.The German standard DIN VDE 0101 (erec-tion of power installations with rated volt-ages above 1 kV) demonstrates typicallythe protective measures and stresses thathave to be taken into consideration for air-insulated switchgear.

Protective measures

Protective measures against direct contact,i. e. protection in the form of covering,obstruction or clearance and appropriatelypositioned protective devices and mini-mum heights.Protective measures against indirect touch-ing by means of relevant grounding meas-ures in accordance with DIN VDE 0141.Protective measures during work onequipment, i.e. during installation mustbe planned such that the specificationsof DIN VDE 0105 (e.g. 5 safety rules) arecomplied withn Protective measures during operation,

e.g. use of switchgear interlock equip-ment

n Protective measures against voltagesurges and lightning strike

n Protective measures against fire, waterand, if applicable, noise insulation.

Stresses

n Electrical stresses, e.g. rated current,short-circuit current, adequate creepagedistances and clearances

n Mechanical stresses (normal stressing),e.g. weight, static and dynamic loads,ice, wind

n Mechanical stresses (exceptionalstresses), e.g. weight and constantloads in simultaneous combination withmaximum switching forces or short-circuit forces, etc.

n Special stresses, e.g. caused by instal-lation altitudes of more than 1000 mabove sea level, or earthquakes

Variables affecting switchgearinstallation

Switchgear design is significantly influ-enced by:n Minimum clearances (depending on

rated voltages) between various activeparts and between active parts andearth

n Arrangement of conductorsn Rated and short-circuit currentsn Clarity for operating staffn Availability during maintenance work,

redundancyn Availability of land and topographyn Type and arrangement of the busbar

disconnectors

The design of a substation determines itsaccessibility, availability and clarity. Thedesign must therefore be coordinated inclose cooperation with the customer. Thefollowing basic principles apply:Accessibility and availability increase withthe number of busbars. At the same time,however, clarity decreases. Installationsinvolving single busbars require minimuminvestment, but they offer only limited flex-ibility for operation management and main-tenance. Designs involving 1 1/2 and 2 cir-cuit-breaker arrangements assure a highredundancy, but they also entail the high-est costs. Systems with auxiliary or bypassbusbars have proved to be economical.The circuit-breaker of the coupling feederfor the auxiliary bus allows uninterruptedreplacement of each feeder circuit-breaker.For busbars and feeder lines, mostly wireconductors and aluminum are used. Multi-ple conductors are required where currentsare high. Owing to the additional short-circuit forces between the subconductors(pinch effect), however, multiple conduc-tors cause higher mechanical stressing atthe tension points. When wire conductors,particularly multiple conductors, are usedhigher short-circuit currents cause a risenot only in the aforementioned pinch ef-fect but in further force maxima in theevent of swinging and dropping of the con-ductor bundle (cable pull). This in turn re-sults in higher mechanical stresses on theswitchgear components. These effects canbe calculated in an FEM simulation (Fig. 4).

Fig. 4: FEM calculation of deflection of wire conductors in the event of short circuit

Horizontaldisplacement in m

Vertical displacement in m

-1.4 -1.0 -0.6 -0.2 0.2 0.6 1.0 1.4

-1.4

-1.2

-1.0

-0.8

-0.6

-1.6

-1.8

-2.0

-2.20


When rated and short-circuit currents arehigh, aluminum tubes are increasingly usedto replace wire conductors for busbars andfeeder lines. They can handle rated cur-rents up to 8000 A and short-circuitcurrents up to 80 kA without difficulty.Not only the availability of land, but alsothe lay of the land, the accessibility andlocation of incoming and outgoing over-head lines together with the number oftransformers and voltage levels considera-bly influence the switchgear design aswell. A one- or two-line arrangement, andpossibly a U arrangement, may be theproper solution. Each outdoor switchgear,especially for step-up substations in con-nection with power stations and largetransformer substations in the extra-high-voltage transmission system, is thereforeunique, depending on the local conditions.HV/MV transformer substations of the dis-tribution system, with repeatedly usedequipment and a scheme of one incomingand one outgoing line as well as two trans-formers together with medium-voltageswitchgear and auxiliary equipment, aremore subject to a standardized designfrom the individual power supply compa-nies.

Preferred designs

The multitude of conceivable designs in-clude certain preferred versions, which aredependent on the type and arrangement ofthe busbar disconnectors:

H arrangement

The H arrangement is preferrably used inapplications for feeding industrial consum-ers. Two overhead lines are connectedwith two transformers and interlinked by asingle-bus coupler. Thus each feeder of theswitchgear can be maintained withoutdisturbance of the other feeders. This ar-rangement guarantees a high availability.

Special layout for single busbars upto 145 kV (withdrawable circuit-breakerarrangement)Further to the H arrangement that is builtin many variants, there are also designsfeaturing withdrawable circuit-breakerswithout disconnectors for this voltagerange. The circuit-breaker is moved electro-hydraulically from the connected positioninto the disconnected position and vice-versa.In comparison with a single busbar withrotary disconnectors, roughly 50% lessground space is required (Fig. 5).


Fig. 5: Substation with withdrawable circuit-breaker

Fig. 6: Substation with rotary disconnector, in-line design

In-line longitudinal layout, with rotarydisconnectors, preferable up to 170 kV

The busbar disconnectors are lined up onebehind the other and parallel to the longitu-dinal axis of the busbar. It is preferable tohave either wire-type or tubular busbarslocated at the top of the feeder conductors.Where tubular busbars are used, gantriesare required for the outgoing overheadlines only. The system design requires onlytwo conductor levels and is therefore clear.If, in the case of duplicate busbars, thesecond busbar is arranged in U-form rela-tive to the first busbar, it is possible to ar-range feeders going out on both sides ofthe busbar without a third conductor level(Fig. 6).

Top view Dimensions in mm

6500

Section A-B Section C-D

A

C

B

D

6500

7000 6500 1330027000

13300

2500

8000 7500

Top view

Section A-A

20500

R1 S1 T1 R2S2T2

8400 1940048300

9000A

A

6500

4500

End bay

Normalbay 9000

8000

2500Dimensions in mm



Central tower layout with rotarydisconnectors, normally only for 245 kV

The busbar disconnectors are arrangedside by side and parallel to the longitudinalaxis of the feeder. Wire-type busbars locat-ed at the top are commonly used; tubularbusbars are also conceivable. This arrange-ment enables the conductors to be easliyjumpered over the circuit-breakers and thebay width to be made smaller than that ofin-line designs. With three conductor levelsthe system is relatively clear, but the costof the gantries is high (Fig. 7).

Diagonal layout with pantographdisconnectors, preferable up to 245 kV

The pantograph disconnectors are placeddiagonally to the axis of the busbars andfeeder. This results in a very clear, space-saving arrangement. Wire and tubular con-ductors are customary. The busbars canbe located above or below the feeder con-ductors (Fig. 8).

1 1/2 circuit-breaker layout,preferable up to 245 kV

The 1 1/2 circuit-breaker arrangement as-sures high supply reliability; however, ex-penditures for equipment are high as well.The busbar disconnectors are of the panto-graph, rotary and vertical-break type. Verti-cal-break disconnectors are preferred forthe feeders. The busbars located at the topcan be of wire or tubular type. Of advan-tage are the equipment connections, whichare very short and allow even in the caseof multiple conductors that high short-cir-cuit currents are mastered. Two arrange-ments are customary:n External busbar, feeders in line with

three conductor levelsn Internal busbar, feeders in H arrange-

ment with two conductor levels (Fig. 9).

Fig. 7: Central tower design

Fig. 8: Busbar area with pantograph disconnector of diagonal design, rated voltage 420 kV

Fig. 9: 1 1/2 circuit-breaker design

18000

9000


12500

16000

7000 17000 17000

Section

10000

10400

Top view

180005000

13300

Dimensions in mm

Bus system By-pass bus

8000 28000 48000 10000

400040005000

29000


18000

17500

480008500



Planning principles

For air-insulated outdoor substations ofopen design, the following planning princi-ples must be taken into account:n High reliability

Reliable mastering of normal andexceptional stresses

Protection against surges and light-ning strikes

Protection against surges directlyon the equipment to be protected(e.g. transformer, HV cable)

n Good clarity and accessibility Clear conductor routing with few

conductor levels Free accessibility to all areas (no

equipment located at inaccessibledepth)

Adequate protective clearances forinstallation, maintenance and transpor-tation work

Adequately dimensioned transportroutes

n Positive incorporation into surroundings As few overhead conductors as

possible Tubular instead of wire-type busbars Unobtrusive steel structures Minimal noise and disturbance level

n EMC grounding systemfor modern control and protection

n Fire precautions and environmentalprotection Adherence to fire protection speci-

fications and use of flame-retardantand nonflammable materials

Use of environmentally compatibletechnology and products

For further information please contact:

Fax: ++ 49-9131- 73 18 58


Gas-insulated Switchgear for Substations

Common characteristic featuresof switchgear 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 64,000 bay operatingyears in over 5,500 installations in all partsof the world. It offers the following out-standing advantages.

Small space requirements

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

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

Full protection against contact withlive parts

The all-round metal enclosure affordsmaximum safety to the 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 simple design in order to minimize thecost of cleaning and inspection and tomake necessary repairs independent ofweather 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 shorterections times and the fact that switch-gear installed indoors can be servicedregardless 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. 10).Beside the conventional circuit-breakerfield, other arrangements can be suppliedsuch as single-bus, ring cable with load-break switches and circuit-breakers, single-bus arrangement with bypass-bus, coupler,bay 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. 10: Typical circuit arrangements of SF6-switchgear



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).

The development of the switchgear isalways based on an overall production con-cept, which guarantees the achievementof the 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).

Fig. 11: Main product range

Siemens GIS switchgear meets allthe performance, quality and reliabilitydemands such as

Compact space-saving designmeans uncomplicated foundations, a widerange of options in the utilization of space,less space taken up by the switchgear.

Minimal weight by lightweight constructionthrough the use of aluminum-alloy and theexploitation of innovations in developmentsuch as computer-aided design tools.

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

Environmental compatibilitymeans no restrictions on choice of locationby means of minimum space requirement,extremely low noise emission and effec-tive gas sealing system (leakage < 1% peryear per gas compartment).

Economical transport

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

Minimal operating costsmeans 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.

Reliabilitymeans 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 assures the high standard ofquality.

Smooth and efficientinstallation and commissioningtransport 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 improve the speediness of site instal-lation and substantially reduce field wiringerrors.

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

50044

80

5170

All dimensions in mm

Switchgear type 8DN9 8DP3 8DQ1

Details on page 1/10 1/11-1/12 1/13

Bay width [mm] 1200 2200 3600

Rated voltage [kV] up to 145 up to 300 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 1550impulse withstandvoltage

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

Rated normal current [A] up to 3150 up to 5000 up to 6300busbars

Rated normal current [A] up to 2500 up to 4000 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(1s)

Rated peak [kA] up to 100 up to 135 up to 170withstand current

SF6-gas pressure [bar] up to 4.3 up to 4.0 up to 4.3(gauge) switchgear

SF6-gas pressure [bar] up to 6.0 up to 6.0 up to 6.5(gauge) circuit-breaker

Inspection > 20 years > 20 years > 20 years

5000

3800

3400

3200



SF6-insulated switchgearup to 145 kV, type 8DN9

The clear bay configuration of the light-weight and small 8DN9 switchgear isevident at first sight. Control and monitor-ing facilities are easily accessible in spiteof the 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 are located on top of the circuit-breaker.The three-phase encapsulated passivebusbar is partitioned off from the activeequipment.Thanks to single-function assemblies(assignment of just one task to each mod-ule) and the versatile modular structure,even unconventional arrangements can beset up out of a pool of only 20 differentmodules.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 guarantees smooth andefficient installation and commissioning.The following major feeder control levelfunctions are performed in the local controlcabinet for each bay, which is integrated inthe operating front of the 8DN9 switch-gear:n Fully interlocked local operation and

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

n Practical dialogue between the digitalfeeder protection system and centralprocessor of the feeder control system

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

n Protection of all auxiliary current andvoltage transformer circuits

n 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.

12

3 4

5

12

1011

67

9

1 2 3 4 5 6 7

8

9

10

11

1213

14

15

16

17

1 Busbar I2 Busbar II3 Busbar disconnector I4 Busbar disconnector isolator II5 Grounding switch6 Make-proof grounding switch7 Cable isolator8 Voltage transformer9 Cable sealing end

10 Current transformer11 Grounding switch12 Circuit-breaker13 Hydraulic storage cylinder14 Electrohydraulic operating unit15 Oil tank16 Circuit-breaker control

with gas monitoring unit17 Local control cabinet

Fig. 12: Switchgear bay 8DN9 up to 145 kV

Fig. 13: 8DN9 switchgear for operating voltage 145 kV



SF6-insulated switchgearup to 300 kV, type 8DP3

A switchgear system with entirely individ-ual enclosure of all modules for the three-phase system.Similar to the design concept of the 8DN9switchgear, a horizontally arranged circuit-breaker has been chosen to be the baseunit for the 8DP3 switchgear although theencapsulation is entirely single-phase in-stead of three-phase (busbar). Making useof the experience gained with previous145 kV GIS, the current transformer wasintegrated in the circuit-breaker enclosure.Mounted on top of the circuit-breaker tankare housings containing disconnectors,or grounding switches, or both devices.Depending on the application up to twogrounding switches can be installed inthese enclosures. One grounding switchserves as a work-in-progress groundingdevice for the circuit-breaker, whereas theother external switch may be of the stand-ard slow-moving type or be equipped witha spring-drive mechanism to achieve faultmaking capabilities. This feature is oftenrequired at incoming or outgoing feederterminations.The standard design is arranged to accom-modate the double-bus-bar circuits prima-rily used. Naturally all other common circuitrequirements for this voltage level, such asdouble or single bus with bypass and the1 1/2 circuit-breaker arrangement, can befulfilled as well.Care has been taken to design the bussections in such a way that the standardwidth of each bay, including the associatedbusbar section, does not exceed 2.2 m.This solution allows preassembly and test-ing at the factory to a large extent. For ex-ample, a complete 245 kV bay of the GIStype 8DP3 can be shipped pre-tested andonly requiring a minimum amount of instal-lation work on site.Circuit-breaker modules with one inter-rupter unit will meet the requirements foroperating voltages up to 245 kV normally.Voltages above 245 kV, however, as wellas high switching capacities require circuit-breaker units with two interrupter unitsper pole.

1 Busbar disconnector II2 Busbar II3 Busbar disconnector I4 Busbar I5 Grounding switch6 Local control cabinet7 Gas monitoring unit8 Circuit-breaker control unit9 Oil tank

10 Electrohydraulic operating unit11 Hydraulic storage cylinder12 Circuit-breaker13 Current transformer14 Cable sealing end15 Voltage transformer16 Make-proof grounding switch17 Cable disconnector18 Grounding switch

1234

5

6

7 8 9 10 11 12 13

14

15

161718

42

3 1

5

12

1318

16

17

1415

Fig. 15: Complete 8DP3 bay for operating voltage 245 kV being unloaded at site

Fig. 14: Switchgear bay 8DP3 up to 245 kV



1 Busbar disconnector II2 Busbar II3 Busbar disconnector I4 Busbar I5 Grounding switch6 Local control cabinet7 Gas monitoring unit8 Circuit-breaker control unit9 Oil tank

10 Electrohydraulic operating unit11 Hydraulic storage cylinder12 Circuit-breaker13 Current transformer14 Cable sealing end15 Voltage transformer16 Make-proof grounding switch17 Cable disconnector18 Grounding switch

1234

5

6

7 8 9 10 11 12

13

14

15161718

42

3 1

5

12

1318

16

17

1415

Fig. 18: Switchgear bay 8DP3 up to 300 kV

Fig. 16: 8DP3 switchgear for operating voltage 245 kV and 40 kA Fig. 17: 8DP3 switchgear for operating voltage 245 kV and 50 kA



SF6-insulated switchgearup to 550 kV, type 8DQ1

A modular switchgear system for highpower switching stations with individualenclosure of all modules for the three-phase system.The design concept of the 8DQ1 switch-gear follows in principle that of the 8DP3for voltages above 245 kV, i.e. the baseunit for the switchgear forms a horizontallyarranged circuit-breaker on top of whichare mounted the housings containing dis-connectors, grounding switches, currenttransformers, etc. The busbar modules arealso single-phase encapsulated and parti-tioned off from the active equipment.As a matter of course the busbar modulesof this switchgear system are passiveelements, too.Additional main characteristic features ofthe switchgear installation are:n 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)

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

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

n 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

10 Grounding switch11 Current transformer12 Cable sealing end13 Local control cabinet14 Gas monitoring unit

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

1 Busbar disconnector I2 Busbar I3 Busbar II4 Busbar disconnector II5 Grounding switch6 Circuit-breaker7 Voltage transformer8 Make-proof grounding

switch9 Cable disconnector

12 11 10 9 8 7 6 5

4

3

2

1

181716151413

12

23

1 4

5

6

1110

8

9

7

Fig. 19: Switchgear bay 8DQ1 up to 550 kV

Fig. 20: 8DQ1 switchgear for operating voltage 420 kV


Air con-ditioningsystem

26.90

23.20

Relay room

Groundingresistor

Shuntreactor

13.8 kVswitchgear

15.95

11.50

8.90Cable duct

40 MVA transformer

Radiators

Compensator

2.20

-1.50

Gas-insulatedswitchgear type8DN9


Scope of supply andbattery limits

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

rupters, disconnectors and groundingswitches, instrument transformers, andbusbar housings as specified. For thedifferent feeder types, the following bat-tery limits apply: Overhead line feeder:

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

Cable feeder:according to IEC 859 the terminationhousing, conductor coupling, and con-necting plate are part of the GIS deliv-ery, while the cable stress cone withmatching flange is part of the cablesupply (see Fig. 24 on page 1/18).

Transformer feeder:connecting flange at switchgear bayand connecting bus ducts to trans-former including any compensatorare delivered by Siemens. The SF6-to-oil bushings plus terminal enclo-sures are part of the transformerdelivery, unless agreed otherwise(see Fig. 25 on page 1/18)*.

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

n 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.

n Hydraulic oil for all circuit-breaker oper-ating mechanisms is supplied with theequipment.

n 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-tractors supply.

n 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.

n Mechanical support structures aboveground are supplied by Siemens; em-bedded steel and foundation work ispart of the installation contractors scope.

Fig. 21: Special arrangement for limited space. Sectional view of a building showing the compact nature ofgas-insulated substations

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



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. 21).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. 22).

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.

Transformer

-Z1

-Z1

-T1

-00 -052

-T2-T5

-051 -08 -09-Z2

OHL

-Z2

5806

3500

Overhead line

Transformer

-Z2-08-09-T5-T2-052

-00

-T1-051

-Z1

The standard dimensions and ISO cornerfittings will facilitate handling during trans-port in the 20 ft frame of containership andon a low-loader truck.Operating staff can enter the containerthrough two access doors.

GIS up to 300 kV in a container

The 8DP3 switchgear requires a containerwith a length of 7550 mm, a width of2800 mm and a height of 3590 mm.In any case, the container equipment caninclude full thermal insulation, lighting andan air-conditioning and ventilation unit.

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:n Intermediate solutions for the

modernization of switching stationsn 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

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

n Switching stations for movable, geo-thermal power plants

145 kV GIS in a standard container

The dimensions of the new 8DN9 switch-gear made it possible to accommodateall active components of the switchgear(circuit-breaker, disconnector, groundingswitch) and the local control cabinet in astandard container.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.

Fig. 22: Containerized 8DN9 switchgear with stub feed in this example

Fig. 23: 8DP3 switching bay being hoisted intoa container



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 standards (IEC-Publ. 517 High-voltage metal-enclosedswitchgear for rated voltages of 72.5 kVand above, IEC-Publ. 129 Alternatingcurrent disconnectors (isolators) andgrounding switches, IEC-Publ. 56 High-voltage alternating-current circuit-break-ers). IEEE P 468-1 Gas-Insulated Sub-station (GIS) Standards. Other standardsare also met.

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(overhead line connections) the appli-cable conditions in IEC-Publication 517or IEEE 0468-1 shall also be observed.

Work, material and design

Field welding at the switchgear is notpermitted.Factory welders must be specially qualifiedpersonnel under continuous supervisionof the associated welding society.Material and process specifications neededfor welding must meet the applicable re-quirements of the country of manufacture.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 sub-assembliesshall be only limited by the transport con-ditions.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 but tovisually cover the surface only. The interiorcolor shall be light (white or light grey).In case painted the outside color of theenclosures shall be grey preferably; how-ever, manufacturers standard paint color isacceptable. A satin mat finish with a highscratch resistance is preferred.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). Horizontally mountedbushings require cleaning openings in theenclosure.

For supervision of the gas within the en-closures, density monitors with electricalcontacts for at least two pressure levelsshall be installed at a central and easilyaccessible location (central gas supervisorycabinet) of each switchgear bay. Thecircuit- breakers, however, might be moni-tored by density gauges fitted in circuit-breaker control units.The manufacturer guarantees that thepressure loss within each individual gascompartment 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 20 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 20 years of operation unless thepermissible number of operations is metat an earlier date, e.g. 6,000 operations atfull load current or 20 operations at ratedshort-circuit current.



Arrangement and modules

ArrangementThe arrangement shall be single-phaseenclosed preferably.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 circuit-breaker shall be arranged hori-zontally and the arc chambers and contactsshall 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 complete contact system (fingers,clusters, jets, SF6 gas) shall be designedto withstand at least 20 operations 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 highly reliable hydraulic operating mech-anism shall be employed for closing andopening the circuit-breaker. A standard sta-tion battery required for control and trip-ping may also be used for recharging thehydraulic operating mechanism.

The hydraulic storage cylinder will holdsufficient energy for all standard 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 hydraulic storage cylinder, or theSF6 density within the circuit-breaker hasdropped below a minimum permissiblelevel.

DisconnectorsAll three-phase isolating switches shall beof the single-break type. 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 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.

High-speed grounding switchesMake-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 (C. T.) 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 andremovable without disturbing the gas com-partment to which they are attached.* two interrupters for voltages exceeding 245 kV



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 manufacturers supply. A mating con-nection piece, which has to be fitted to thecable end, will 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. 26: 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.

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.

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). Tolerance:max. 0.4 V measured at 60 ohms (lessthan 1 pC). This test ensures maximumsafety against insulator failure, good long-term performance and thus a very highdegree of reliability.

Pressure tests

Each enclosure of the switchgear shallbe pressure-tested to at least double theservice pressure, so that the risk of mate-rial defects will be fully excluded.

Leakage tests

Leakage tests are performed on the sub-assemblies shall ensure that the flangesand covers faces are clean, and that theguaranteed leakage rate will not be ex-ceeded.

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.

Fig. 25: 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.

Fig. 27: Typical arrangements of bay terminationmodules

Fig. 24: 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.



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.


Fax: ++ 49-9131-7-346 62

Fig. 30: 8DN9 circuit-breaker operating mechanismwith plug connections of control circuits

Fig. 28: 8DN9 circuit-breaker control cubicle with gasmonitoring devices

Fig. 29: OHL connection of a 420 kV system

Fig. 33: 8DP3 transformer termination modules

Fig. 32: 8DP3 cable termination modules

Fig. 31: Double-bay arrangement of 8DN9 switchgearbeing loaded for transport


Gas-insulated Transmission Lines (GIL)

Introduction

For high-power transmission systemswhere overhead lines are not suitable,alternatives are gas-insulated transmissionlines (GIL).The GIL exhibits the following differencesin comparison with cables:n High power ratings

(transmission capacity up to 3000 MVAper System)

n Suitable for long distances(100 km and more without compensa-tion of reactive power)

n High short-circuit withstand capability(including internal arc faults)

n Possibility of direct connection to gas-insulated switchgear (GIS) and gas-insu-lated arresters without cable entrancefitting

n Multiple earthing points possiblen Not inflammableThe innovations in the latest Siemens GILdevelopment are the considerable reduc-tion of costs and the introduction of buriedlaying technique for GIL for long-distancepower transmission.SF6 has been replaced by a gas mixtureof SF6 and N2 as insulating medium.

Siemens experience

Back in the 1960s with the introduction ofsulphur hexafluoride (SF6) as an insulatingand switching gas, the basis was found forthe development of gas-insulated switch-gear (GIS).On the basis of GIS experience, Siemensdeveloped SF6 gas-insulated lines to trans-mit electrical energy too. In the early 1970sinitial projects were planned and imple-mented. Such gas-insulated lines wereusually used within substations as busbarsor bus ducts to connect gas-insulatedswitchgear with overhead lines, the aimbeing to reduce clearances in comparisonto air-insulated overhead lines.Implemented projects include GIL laying intunnels, in sloping galleries, in verticalshafts and in open air installation.Flanging as well as welding has been ap-plied as jointing technique.

The gas-insulated transmission line tech-nique has proved a highly reliable systemin terms of mechanical and electrical fail-ures. Once a system is commissioned andin service, it can run reliably without anydielectrical or mechanical failures reportedover the course of 20 years. For example,one particular Siemens GIL will not under-go its scheduled inspection after 20 yearsof service, as there has been no indicationof any weak point.Fig. 34 shows the arrangement of sixphases in a tunnel.

Fig. 34: GIL arrangement in the tunnel of the Wehr pumped storage station(4000 m length, in service since 1975)

Fig. 35: Siemens lab prototype for dielectric tests

Basic design

In order to meet mechanical stability crite-ria, gas-insulated lines need minimumcross-sections of enclosure and conductor.With these minimum cross-sections, highpower transmission ratings are given.Due to the gas as insulating medium, lowcapacitive loads are assured so that com-pensation of reactive power is not needed,even for long distances of 100 km andmore.


Gas-insulated Transmission Lines (GIL)

Several development tests have been car-ried out in Siemens test labs as well as incooperation with the French utility compa-ny Electricit de France (EDF). Dielectrictests have been undertaken on a lab proto-type as shown in Fig. 35.Results of these investigations show thatthe bulk of the insulating gas for industrialprojects involving a considerable amountof such a substance should be nitrogen,a nontoxic natural gas.

Reduction of SF6 content

However, another insulating gas should beadded to nitrogen in order to improve theinsulating capability and to minimize sizeand pressure. A N2/SF6 gas mixture withhigh nitrogen content (and sulphur hexa-fluoride portion as low as possible) wasfinally chosen as insulating medium.To determine the percentage of SF6 anoptimization process was needed to findthe best possible ratio between SF6 con-tent, gas pressure and enclosure diameter.The basic behaviour of N2/SF6 gas mixturesshows that with an SF6 content of only1525%, an insulating capability of 7080%of pure SF6 can be attained at the samegas pressure.The technical data of the GIL are shown inFig. 36.

Jointing technique

In order to improve the gas-tightnessand to facilitate laying, flanges have beenavoided as jointing technique. Instead,welding has been chosen to join the vari-ous GIL construction units.The welding process is highly automated,with the use of an orbital welding machineto ensure high quality of the joints. Thisorbital welding machine contributes tohigh productivity in the welding processand therefore speeds up laying. The relia-bility of the welding process is controlledby an integrated computerized qualityassurance system.

Anti-corrosion protection

Directly buried gas-insulated transmissionlines will be safeguarded by a passive andactive corrosion protection system. Thepassive corrosion protection system com-prises a PE or PP coating and assures atleast 40 years of protection. The activecorrosion protection system provides pro-tection potential in relation to the alumi-num sheath. An important requirementtaken into account is the situation of anearth fault with a high current of up to63 kA to earth.

Laying

The most recently developed SiemensGILs are scheduled for directly buriedlaying.The laying technique must be as compat-ible as possible with the landscape andmust take account of the sequence of

Fig. 37: GIL laying technique

seasons. The laying techniques for pipe-lines have been developed over manyyears and have proved reliable. The high-voltage gas-insulated transmission lineneeds special treatment where the pipe-line technique has to be adapted.The laying process is illustrated in Fig. 37.The assembly area needs to be protectedagainst dust, particles, humidity and otherenvironmental factors that might disturbthe dielectric system. Clean assemblytherefore plays a major role in setting upcross-country GILs under normal environ-mental conditions. The combination ofclean assembly and productivity is en-hanced by a high level of automation ofthe overall process. A clean assemblytent is essential.

References

Siemens has gathered experience withgas-insulated transmission lines at ratedvoltages of up to 550 kV and with systemlengths totalling more than 30 km.The first GIL stretch built by Siemens isthe connection of the turbine generator/pumping motor of a pumped storagestation with the switchyard. The 420 kVGIL is laid in a tunnel through a mountainand has a length of 4000 m (Fig. 34). Thisconnection was commissioned in 1975 atthe Wehr pumped storage station in theBlack Forest in Southern Germany.


Fax ++ 49-9131-7-34490

Fig. 36: GIL technical data

Technical data

up to 550 kV

20004600 A

15003000 MVA

2.2*lr for 10 min.

1.9*lr for 1 h

60 nF/km

1100 km

10%/90%up to35%/65%

directly buried

in tunnels/sloping galleries/vertical shafts

open air installation

Rated voltage

Rated current lr

Transmissioncapacity

Overload capacity

Capacitance

Typical length

Gas mixture SF6/N2ranging from

Laying

P/MCD


Circuit Breakers for 72 kV up to 800 kV

Introduction

Circuit breakers are the main module ofboth AIS and GIS switchgear. They have tomeet high requirements in terms of:n Reliable opening and closingn Consistent quenching performance with

rated and short-circuit currents evenafter many switching operations

n High-performance, reliable maintenance-free operating mechanisms.

Technology reflecting the latest state ofthe art and years of operating experienceare put to use in constant further develop-ment and optimization of Siemens circuitbreakers. This makes Siemens circuitbreakers able to meet all the demandsplaced on high-voltage switchgear.The comprehensive quality system,ISO 9001 certified, covers development,manufacture, sales, installation and after-sales service. Test laboratories are accred-ited to EN 45001 and PEHLA/STL.

Main construction elements

Each circuit breaker bay for gas-insulatedswitchgear includes the full complementof isolator switches, grounding switches(regular or proven), instrument transform-ers, control and protection equipment, in-terlocking and monitoring facilities, com-monly used for this type of installation(See chapter GIS, page 1/8 and following).Circuit breakers for air-insulated switch-gear are individual components and areassembled together with all individualelectrical and mechanical components ofan AIS installation on site.All Siemens circuit breaker types, whetherair- or gas-insulated, consist of the samecomponents of a parts family, i.e.:n Interrupter unitn Operating mechanismn Sealing systemn Operating rodn Control elements.

SF6-insulated circuit breakers

Controlelements

Interrupterunits

Operatingmechanism

Sealing systems

Parts family

Fig. 38: Circuit breaker parts family



The blast cylinder (4) encloses the arc-quenching arrangement like a pressurechamber. The compressed SF6 flows ra-dially into the break by the shortest routeand is discharged axially through the noz-zles (6). After arc extinction, the contacttube (3) moves into the open position.In the final position, handling of test volt-ages in accordance with IEC and ANSI isfully guaranteed, even after a number ofshort-circuit switching operations.

Major features

n Erosion-resistant graphite nozzlesn Consistently high dielectric strengthn Consistent quenching capability across

the entire performance rangen High number of short-circuit breaking

operationsn High levels of availabilityn Long maintenance intervals.

The operating mechanism

The operating mechanism is a centralmodule of the high-voltage circuit breakers.Two different mechanism families are avail-able for Siemens circuit breakers:n Electrohydraulic mechanism for all

AIS and GIS typesn Spring-stored energy mechanism for

AIS types up to 170 kV.

The electrohydraulic operating mechanism

All hydraulically operated Siemens circuitbreakers have a uniform operating mecha-nism concept, whether for 72 kV circuitbreakers with one interrupter unit per poleor breakers from the 800 kV level with fourinterrupter units per pole. Identical operat-ing mechanisms (modules) are used forsingle or triple-pole switching of outdoorcircuit breakers.The electrohydraulic operating mecha-nisms have proved their worth all over theworld. The power reserves are ample, theswitching speed is high and the storagecapacity substantial. The working capacityis indicated by the permanent self-monitor-ing system.

The interrupter unit

Current-path assembly

The conducting path is made up of theterminal plates (1 and 7), the fixed tubes(2) and the spring-loaded contact fingersarranged in a ring in the moving contacttube (3).

Arc-quenching assembly

The fixed tubes (2) are connected bythe contact tube (3) when the breaker isclosed. The contact tube (3) is rigidly cou-pled to the blast cylinder (4), the two to-gether with a fixed annular piston (5) inbetween forming the moving part of thebreak chamber. The moving part is drivenby an operating rod (8) to the effect thatthe SF6 pressure between the piston (5)and the blast cylinder (4) increases.When the contacts separate, the movingcontact tube (3), which acts as a shutoffvalve, releases the SF6. An arc is drawnbetween one nozzle (6) and the contacttube (3). It is driven in a matter of millisec-onds between the nozzles (6) by the gasjet and its own electrodynamic forces andis safely extinguished.

1

2

36

4

5

2

8

7

Arc

Breaker inclosed position

Precompression Gas flow duringarc quenching

Breaker inopen position

Upper terminalplateFixed tubesMoving contacttubeBlast cylinderBlast pistonArc-quenchingnozzlesLower terminalplateOperating rod

1

23

456

7

8

Fig. 39: The interrupter unit



The force required to move the piston andpiston rod is provided by differential oilpressure inside a sealed system. A hydrau-lic storage cylinder filled with compressednitrogen provides the necessary energy.Electromagnetic valves control the oil flowbetween the high- and low-pressure sidein the form of a closed circuit.

Main features:

n Plenty of operating energyn Long switching sequencesn Reliable check of energy reserves

at any timen Switching positions are reliably

maintained, even when the auxiliarysupply fails

n Excessive strong foundationsn Low-noise switchingn No oil-leakage and consequently

environmentally compatiblen Maintenancefree.

Description of function

n Closing:The hydraulic valve is opened by elec-tromagnetic means. Pressure from thehydraulic storage cylinder is therebyapplied to the piston with two differentsurface areas. The breaker is closed viacouplers and operating rods moved bythe force which acts on the larger sur-face of the piston. The operating mech-anism is designed to ensure that, in theevent of a pressure loss, the breakerremains in the particular position.

n Tripping:The hydraulic valve is changed overelectromagnetically, thus relieving thelarger piston surface of pressure andcausing the piston to move onto theOFF position. The breaker is ready forinstant operation because the smallerpiston surface is under constant pres-sure. Two electrically separate trippingcircuits are available for changing thevalve over for tripping.

M

P P

M

Oil tank

Hydraulic storagecylinder

Operating cylinder

Releases

Operating piston

Pilot control

On Off

N2

Main valve

Auxiliaryswitch

Monitoring unitand hydraulic

pump with motor PP

Fig. 43: Schematic diagram of a Q-range operating mechanism

Fig. 40: Operating unit of the Q-range AIS circuitbreakers

Fig. 42: Operating cylinder with valve block andmagnetic releases

Fig. 41: Q-range operating unit for GIS circuitbreaker 8DN9



The spring-stored energyoperating mechanism

Optional to the hydraulic operating mecha-nism, Siemens circuit breakers for voltagesup to 170 kV can be equipped with spring-stored energy operating mechanisms.These drives are based on the same prin-ciple, which has been proving its worth inSiemens low and medium voltage circuitbreakers for decades. The design is simpleand robust with few moving parts and avibration-isolated latch system of highestreliability. All components of the operatingmechanism, the control and monitoringequipment and all terminal blocks arearranged compact and yet clear in onecabinet.Depending on the design of the operat-ing mechanism, the energy required forswitching is provided by individual com-pression springs (i.e. one per pole) or bysprings that function jointly on a triple-polebasis.The principle of the operating mechanismwith charging gear and latching is identicalon all types. The differences betweenmechanism types are in the number, sizeand arrangement of the opening and clos-ing springs.

Major features at a glance

n Uncomplicated, robust constructionwith few moving parts

n Maintenancefreen Vibration-isolated latchesn Load-free uncoupling of charging

mechanismn Ease of accessn 10,000 operating cycles

1234567

89

10111213141516

1718

Corner gearsCoupling linkageOperating rodClosing releaseCam plateCharging shaftClosing springconnecting rodClosing springHand-wound mechanismCharging mechanismRoller levelClosing damperOperating shaftOpening damperOpening releaseOpening springconnecting rodMechanism housingOpening spring

1

2

3

4

5

6

7

818

17

1615

14

1312

11

10

9

Fig. 44

Fig. 45: Combined operating mechanism and monitoring cabinet


Circuit Break

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Siemens Power Engineering Guide Transmission Distribution

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