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Contents PageIntroduction ...................................... 2/2

Air-InsulatedOutdoor Substations ....................... 2/4

Circuit-BreakersGeneral ............................................. 2/10Circuit-Breakers72 kV up to 245 kV .......................... 2/12Circuit-Breakers245 kV up to 800 kV ........................ 2/14Live-Tank Circuit-Breakers .......... 2/16Dead-Tank Circuit-Breakers ........ 2/20

Surge Arresters .............................. 2/24

Gas-Insulated Switchgearfor SubstationsIntroduction ..................................... 2/28Main Product Range ..................... 2/29Special Arrangements .................. 2/33Specification Guide ....................... 2/34Scope of Supply ............................. 2/37

Gas-insulatedTransmission Lines (GIL) .............. 2/38

Overhead Power Lines ................. 2/40

High-Voltage DirectCurrent Transmission .................... 2/49

Power Compensation inTransmission Systems .................. 2/52

2

High VoltageHigh Voltage

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

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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).

Gas-insulated transmission lines (GIL)

A special application of gas-insulatedequipment are gas-insulated transmissionlines (GIL). They are used where high-volt-age overhead lines are not suitable for anyreason. GIL have a high power transmis-sion capability, even when laid under-ground, low resistive and capacitive lossesand low electromagnetic fields.

Fig. 1: Outdoor switchgear

Fig. 2: GIS substations in metropolitan areas

Siemens Power Engineering Guide · Transmission and Distribution · 4th Edition 2/3

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High-Voltage Switchgear for Substations

Turnkey Installations

High-voltage switchgear is normally com-bined with transformers and other equip-ment to complete transformer substationsin order to Step-up from generator voltage level

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

high-voltage grid system(HV/HV) 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 are

always fully informed of the state of theart, even before a new standard or specifi-cation is published.

Quality/Environmental Management

Our own high-performance, internationallyaccredited test laboratories and a certifiedQM system testify to the quality of ourproducts and services.Milestones: 1983: Introduction of a quality system

on the basis of Canadian standardCSA Z 299 Level 1

1989: Certification of the SWH qualitysystem in accordance withDIN EN ISO 9001 by the GermanAssociation for Certification ofQuality Systems (DQS)

1992: Repetition audit and extensionof the quality system to the completeEV H Division

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

1994: Certification of the environmental-systems in accordance withDIN EN ISO 14001 by the DQS

1995: Mutual QEM Certificate

Ancillaryequipment

Design

CivilEngineering

Buildings,roads,foundations

StructuralSteelwork

Gantries andsubstructures

Major com-ponents,

e.g. trans-former

SubstationControl

Control andmonitoring,measurement,protection, etc.

AC/DC

auxililiaries

Surge

diverters

Earthing

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

Know how, experience and worldwidepresence

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 theworld’s first GIS substation using SF6 asinsulating and quenching medium. Gas-in-sulated transmission lines have featuredin the range of products since 1976.


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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 only authorized per-sons have access.Relevant IEC 60060 specifications apply tooutdoor switchgear equipment. Insulationcoordination, including minimum phase-to-phase and phase-to-ground clearances,is effected in accordance with IEC 60071.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 EN 50110 (VDE 0105) (e.g. 5 safetyrules) are complied with Protective measures during operation,

e.g. use of switchgear interlock equip-ment

Protective measures against voltagesurges and lightning strike

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

Stresses

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

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

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

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: Minimum clearances (depending on

rated voltages) between various activeparts and between active parts andearth

Arrangement of conductors Rated and short-circuit currents Clarity for operating staff Availability during maintenance work,

redundancy Availability of land and topography Type and arrangement of the busbar

disconnectorsThe 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 (Finite ElementMethod) simulation (Fig. 4).

ker


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When rated and short-circuit currents arehigh, aluminum tubes are increasingly usedto replace wire conductors for busbarsand feeder lines. They can handle ratedcurrents up to 8000 A and short-circuitcurrents up to 80 kA without difficulty.Not only the availability of land, but alsothe lie of the land, the accessibility and lo-cation of incoming and outgoing overheadlines together with the number of trans-formers and voltage levels considerablyinfluence the switchgear design as well.A one or two-line arrangement, and possi-bly a U arrangement, may be the propersolution. Each outdoor switchgear installa-tion, especially for step-up substations inconnection 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.


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

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 (Fig. 5) is preferrablyused in applications for feeding industrialconsumers. Two overhead lines are con-nected with two transformers and inter-linked by a single-bus coupler. Thus eachfeeder of the switchgear can be main-tained without disturbance of the otherfeeders. This arrangement assures a highavailability.

Special layouts for single busbars up to145 kV with withdrawable circuit-break-er and modular switchbay arrangement

Further to the H arrangement that is builtin many variants, there are also designswith withdrawable circuit-breakers andmodular switchbays for this voltage range.For detailed information see the followingpages:

Fig. 5: Module plan view

= T1

M

M

M

M

MM

– F1

– Q0

– T1

– T1

– T5

– Q1

– Q0

– Q8

– T1

– T5

– Q1

– Q0

– Q8

– Q1 – Q1

= T1

– F1

– Q0

– T1

– Q10 – Q11


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170017006300

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-Q11-Q12

25003100

2145014450

=T1

4500

-Q0 -T1625 6257000

-Q11-Q12 -Q9

3100-Q0

-T1/-T5

25002500

2247


Withdrawable circuit-breaker

GeneralFor 123/145 kV substations with singlebusbar system a suitable alternative is thewithdrawable circuit-breaker. In this kind ofswitchgear busbar- and outgoing discon-nector become inapplicable (switchgear

Fig. 6a: H arrangement with withdrawable circuit-breaker, plan view and sections

Fig. 6b: H arrangement with withdrawable circuit-breaker, ISO view Fig. 7: Technical data

without disconnectors). The isolating dis-tance is reached with the moving of thecircuit-breaker along the rails, similar to thewell-known withdrawable-unit design tech-nique of medium-voltage switchgear. Indisconnected position busbar, circuit-break-er and outgoing circuit are separated fromeach other by a good visible isolating dis-

tance. An electromechanical motive unitensures the uninterrupted constant movingmotion to both end positions. The circuit-breaker can only be operated if one of theend positions has been reached. Move-ment with switched-on circuit-breaker isimpossible. Incorrect movement, whichwould be equivalent to operating a discon-nector under load, is interlocked. In theevent of possible malfunction of the posi-tion switch, or of interruptions to travelbetween disconnected position and operat-ing position, the operation of the circuit-breaker is stopped.The space required for the switchgear isreduced considerably. Due to the arrange-ment of the instrument transformers onthe common steel frame a reduction in therequired space up to about 45% in compar-ison to the conventional switchgear sec-tion is achieved.DescriptionA common steel frame forms the base forall components necessary for reliable oper-ation. The withdrawable circuit-breakercontains: Circuit-breaker type 3AP1F Electromechanical motive unit Measuring transformer for protection

and measuring purposes Local control cubicleAll systems are preassembled as far aspossible. Therefore the withdrawable CBcan be installed quite easily and efficientlyon site.The advantages at a glance Complete system and therefore lower

costs for coordination and adaptation. A reduction in required space by about

45% compared with conventionalswitchbays

Clear wiring and cabling arrangement Clear circuit state Use as an indoor switchbay is also pos-

sible.

Technical data

123 kV (145 kV)

1250 A (2000 A)

31.5 kA, 1s,(40 kA, 3s)

230/400 V AC

220 V DC

Nominal voltage [kV]

Nominal current [A]

Nominal short [kA]time current

Auxiliary supply/motive unit [V]

Control voltage [V]


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30002000 2000

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-Q8 -Q0-Q1 -T1-T5

-Q10/-Q11 -Q0-Q1-T1 =T1-F1

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8000

19000

11500

8000

3000

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9500

19000 AA

The advantages at a glance Complete system and therefore lower

costs for coordination and adaptation. Thanks to the integrated control cubicle,

upgrading of the control room isscarecely necessary.

A modular switchbay can be insertedvery quickly in case of total breakdownor for temporary use during reconstruc-tion.

A reduction in required space by about50% compared with conventionalswitchbays is achieved by virtue of thecompact and tested design of the mod-ule (Fig. 8).

The application as an indoor switchbay ispossible.


Fig. 9: Technical data

Modular switchbay

GeneralAs an alternative to conventional substa-tions an air-insulated modular switchbaycan often be used for common layouts.In this case the functions of several HVdevices are combined with each other.This makes it possible to offer a standard-ized module.Appropriate conventional air-insulatedswitchbays consist of separately mountedHV devices (for example circuit-breaker,disconnector, earthing switches, transform-ers), which are connected to each other byconductors/tubes. Every device needs itsown foundations, steel structures, earthingconnections, primary and secondary termi-nals (secondary cable routes etc.).

DescriptionA common steel frame forms the base forall components necessary for a reliable op-eration. The modul contains: Circuit-breaker type 3AP1F Motor-operated disconnecting device Current transformer for protection and

measuring purposes Local control cubicleAll systems are preassembled as far aspossible. Therefore the module can be in-stalled quite easily and efficiently on site.

Technical data

123 kV (145 kV)

1250 A (2000 A)

31.5 kA, 1s,(40 kA, 3s)

230/400 V AC

220 V DC

Nominal voltage

Nominal current

Nominal shortcurrent

Auxiliary supply

Control voltage

Fig. 8: Plan view and side view of H arrangement with modular switchbays


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Top view

Section A-A

20500

R1 S1 T1 R2S2T2

8400 1940048300

9000A

A

6500

4500

End bay

Normalbay 9000

8000

2500Dimensions in mm


Fig. 12: Busbar area with pantograph disconnector of diagonal design, rated voltage 420 kV

Fig.11: Central tower 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. 10).

Fig. 10: Substation with rotary disconnector, in-line design

18000

9000


12500

16000

7000 17000 17000

Section

10000

10400

Top view

180005000

13300

Dimensions in mmBus system Bypass bus

8000 28000 48000 10000

400040005000

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. 11).

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. 12).


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Fig.13 : 1 1/2 Circuit-breaker design

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-penditure for equipment is 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 enable (even in the caseof multiple conductors) high short-circuitcurrents to be mastered. Two arrange-ments are customary: External busbar, feeders in line with

three conductor levels Internal busbar, feeders in H arrange-

ment with two conductor levels (Fig. 13).

Planning principles

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

– Reliable mastering of normal andexceptional stresses

– Protection against surges and light-ning strikes

– Protection against surges directlyon the equipment concerned (e.g.transformer, HV cable)

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

Positive incorporation into surroundings– As few overhead conductors as

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

EMC grounding systemfor modern control and protection

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 58e-mail: [email protected]

29000


18000

17500

480008500


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Circuit-Breakers for 72 kV up to 800 kV

General

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

rated and short-circuit currents evenafter many switching operations

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 circuit-breakers. This makes Siemens circuit-breakers 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 2/30 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, are made up of thesame range of components, i.e.: Interrupter unit Operating mechanism Sealing system Operating rod Control elements.

Fig. 14: Circuit-breaker parts

Circuit-breaker for air-insulated switchgear

Controlelements

Circuit-breaker in SF6-insulated switchgear

Interrupterunit

Operatingmechanism


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Interrupter unit –two arc-quenching principles

The Siemens product range includes high-voltage circuit-breakers with self-compres-sion interrupter chambers and twin-nozzleinterrupter chambers – for optimumswitching performance under every operat-ing condition for every voltage level.

Self-compression breakers

3AP high-voltage circuit-breakers for thelower voltage range ensure optimum useof the thermal energy of the arc in thecontact tube. This is achieved by the self-compression switching unit.Siemens patented this arc-quenching prin-ciple in 1973. Since then, we have contin-ued to develop the technology of the self-compression interrupter chamber. One ofthe technical innovations is that the arc en-ergy is being increasingly used to quenchthe arc. In short-circuit breaking operationsthe actuating energy required is reduced tothat needed for mechanical contact move-ment. That means the operating energy istruly minimized. The result is that the self-compression interrupter chamber allowsthe use of a compact stored-energy springmechanism with unrestrictedly high de-pendability.

Twin-nozzle breakers

On the 3AQ and 3AT switching devices, acontact system with graphite twin-nozzlesensures consistent arc-quenching behaviorand constant electric strength, irrespectiveof pre-stressing, i.e. the number of breaksand the switched current. The graphitetwin-nozzles are resistant to burning andthus have a very long service life. As aconsequence, the interrupter unit of thetwin-nozzle breaker is particularlypowerful.Moreover, this type of interrupter chamberoffers other essential advantages. General-ly, twin-nozzle interrupter chambers oper-ate with low overpressures during arc-quenching. Minimal actuating energy isadequate in this operating system as well.The resulting arc plasma has a compara-tively low conductivity, and the switchingcapacity is additionally favourably influ-enced as a result.

The twin-nozzle system has also provenitself in special applications. Its specificproperties support switching without re-striking of small inductive and capacitivecurrents. By virtue of its high arc resist-ance, the twin-nozzle system is particularlysuitable for breaking certain types of shortcircuit (e.g. short circuits close to genera-tor terminals) on account of its high arc re-sistance.

Operating mechanism –two principles for allspecific requirements

The operating mechanism is a central mod-ule of the high-voltage circuit-breakers.Two different mechanism types are availa-ble for Siemens circuit-breakers: Stored-energy spring actuated

mechanism, Electrohydraulic mechanism,depending on the area of application andvoltage level, thus every time ensuring thebest system of actuation. The advantagesare trouble-free, economical and reliablecircuit-breaker operation for all specific re-quirements.

Specific use of the stored-energyspring mechanism

The actuation concept of the 3AP high-volt-age circuit-breaker is based on the stored-energy spring principle. The use of such anoperating mechanism in the lower voltagerange became appropriate as a result ofdevelopment of a self-compression inter-rupter chamber that requires only minimalactuation energy.

Advantages of the stored-energy springmechanism at a glance:

The stored-energy spring mechanism of-fers the highest degree of operationalsafety. It is of simple and sturdy design– with few moving parts. Due to theself-compression principle of the inter-rupter chamber, only low actuating forc-es are required.

Stored-energy spring mechanisms arereadily available and have a long servicelife: Minimal stressing of the latch mech-anisms and rolling-contact bearings inthe operating mechanism ensure reliableand wear-free transmission of forces.

Stored-energy spring mechanisms aremaintenance-free: the spring charginggear is fitted with wear-free spur gears,enabling load-free decoupling.

Specific use of the electrohydraulicmechanism

The actuating energy required for the 3AQand 3AT high-voltage circuit-breakers athigher voltage levels is provided by provenelectrohydraulic mechanisms. The inter-rupter chambers of these switching devic-es are based on the graphite twin-nozzlesystem.

Advantages of the electrohydraulicmechanism at a glance:

Electrohydraulic mechanisms provide thehigh actuating energy that makes it pos-sible to have reliable control even oververy high switching capacities and to bein full command of very high loads in theshortest switching time.

The switch positions are held safelyeven in the event of an auxiliary powerfailure.

A number of autoreclosing operationsare possible without the need forrecharging.

Energy reserves can be reliably con-trolled at any time.

Electrohydraulic mechanisms are mainte-nance-free, economical and have a longservice life.

They satisfy the most stringent require-ments regarding environmental safety.This has been proven by electrohydraulicmechanisms in Siemens high-voltagecircuit-breakers over many years of serv-ice.


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Fig. 15: The interrupter unit

The interrupter unit

Self-compression system

The current path

The current path is formed by the terminalplates (1) and (8), the contact support (2),the base (7) and the moving contact cylin-der (6). In closed state the operating cur-rent flows through the main contact (4).An arcing contact (5) acts parallel to this.

Major features:

Self-compression interrupter chamber Use of the thermal energy of the arc Minimized energy consumption High reliability for a long time

Siemens circuit-breakers for the lowervoltage levels 72 kV up to 245 kV, whetherfor air-insulated or gas-insulated switch-gear, are equipped with self-compressionswitching units and spring-stored energyoperating mechanisms.

Breaking operating currents

During the opening process, the main con-tact (4) opens first and the current commu-tates on the still closed arcing contact. Ifthis contact is subsequently opened, anarc is drawn between the contacts (5). Atthe same time, the contact cylinder (6)moves into the base (7) and compressesthe quenching gas there. The gas thenflows in the reverse direction through thecontact cylinder (6) towards the arcing con-tact (5) and quenches the arc there.

Breaking fault currents

In the event of high short-circuit currents,the quenching gas on the arcing contact isheated substantially by the energy of thearc. This leads to a rise in pressure in thecontact cylinder. In this case the energy forcreation of the required quenching pres-sure does not have to be produced by theoperating mechanism.Subsequently, the fixed arcing contact re-leases the outflow through the nozzle (3).The gas flows out of the contact cylinderback into the nozzle and quenches the arc.

Closed position Open position

Terminal plateContact supportNozzleMain contactArc contactContactcylinderBaseTerminal plate

123456

78

8

7

6

543

21

OpeningMain contact open

OpeningArcing contact open


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The operating mechanism

Spring-stored energy type

Siemens circuit-breakers for voltages up to245 kV are equipped with spring-stored en-ergy operating mechanisms. These drivesare based on the same principle that hasbeen proving its worth in Siemens low andmedium-voltage circuit-breakers for dec-ades. The design is simple and robust withfew moving parts and a vibration-isolatedlatch system of highest reliability. All com-ponents of the operating mechanism, thecontrol and monitoring equipment and allterminal blocks are arranged compact andyet clear in one cabinet.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

Uncomplicated, robust constructionwith few moving parts

Maintenance-free Vibration-isolated latches Load-free uncoupling of charging

mechanism Ease of access 10,000 operating cycles

Fig. 16

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

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818

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1615

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1312

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9

Fig. 17: Combined operating mechanismand monitoring cabinet


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Major features

Erosion-resistant graphite nozzles Consistently high dielectric strength Consistent quenching capability across

the entire performance range High number of short-circuit breaking

operations High levels of availability Long maintenance intervals.The interrupter unit

Twin-nozzle system

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).

Fig. 18: The interrupter unit

Siemens circuit-breakers for the highervoltage levels 245 kV up to 800 kV, wheth-er for air-insulated or gas-insulated switch-gear, are equipped with twin-nozzle inter-rupter chambers and electrohydraulicoperating mechanisms.

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.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 60000 andANSI is fully assured, even after a numberof short-circuit switching operations.

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Arc

Breaker inclosed position

Precompression Gas flow duringarc quenching

Breaker inopen position

Upper terminalplateFixed tubesMoving contacttubeBlast cylinderBlast pistonArc-quenchingnozzlesLower terminalplateOperating rod

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The operating mechanism

Electrohydraulic type

All hydraulically operated Siemens circuit-breakers have a uniform operating mecha-nism concept. Identical operating mecha-nisms (modules) are used for single or tri-ple-pole switching of outdoor circuit-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 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 side inthe form of a closed circuit.

Main features:

Plenty of operating energy Long switching sequences Reliable check of energy reserves

at any time Switching positions are reliably

maintained, even when the auxiliarysupply fails

Excessive strong foundations Low-noise switching No oil leakage and consequently

environmentally compatible Maintenance-free.

Description of function

Closing:The hydraulic valve is opened by elec-tromagnetic means. Pressure from thehydraulic storage cylinder is thereby ap-plied 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.

Fig. 21: Schematic diagram of a Q-range operating mechanism

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.


Fig. 19: Operating unit of the Q range AIS circuitbreakers

Fig. 20: Operating cylinder with valve block andmagnetic releases

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


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Live-Tank Circuit-Breakers for 72 kV up to 800 kV

Fig. 23: 800 kV circuit-breaker 3AT5

Fig. 24: 245 kV circuit-breaker 3AQ2

Fig. 22: 145 kV circuit-breaker 3AP1FG with triple-polespring stored-energy operating mechanism

Circuit-breakersfor air-insulated switchgearStandard live-tank breakers

The construction

All live-tank circuit-breakers are of thesame general design, as shown in the illus-trations. They consist of the following maincomponents:1) Interrupter unit2) Closing resistor (if applicable)3) Operating mechanism4) Insulator column (AIS)5) Operating rod6) Breaker base7) Control unitThe uncomplicated design of the breakersand the use of many similar components,such as interrupter units, operating rodsand control cabinets, ensure high reliabilitybecause the experience of many breakersin service has been applied in improvementof the design. The twin nozzle interrupterunit for example has proven its reliability inmore than 60,000 units all over the world.The control unit includes all necessarydevices for circuit-breaker control and mon-itoring, such as: Pressure/SF6 density monitors Gauges for SF6 and hydraulic pressure

(if applicable) Relays for alarms and lockout Antipumping devices Operation counters (upon request) Local breaker control (upon request) Anticondensation heaters.

Transport, installation and commissioningare performed with expertise and effi-ciency.The tested circuit-breaker is shipped inthe form of a small number of compactunits. If desired, Siemens can provideappropriately qualified personnel for instal-lation and commissioning.


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Fig. 26: Type 3AP1FG

Fig. 25: Type 3AT4/5

Fig. 27: Type 3AQ2

1 Interrupter unit2 Closing resistor3 Valve unit4 Electrohydraulic

operatingmechanism

5 Insulator columns6 Breaker base7 Control unit

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2

1 Interrupter unit2 Post insulator3 Circuit-breaker base4 Operating mechanism

and control cubicle5 Pillar

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1

Interrupter unitArc-quenching nozzlesMoving contactFilterBlast pistonBlast cylinderBell-crank mechanismInsulator columnOperating rodHydraulic operating mechanismON/OFF indicatorOil tankControl unit

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653721

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10111213


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Type 3AP1/3AQ1 3AP2/3AQ2

Spring-stored energy mechanism/Electrohydraulic mechanism

O - 0.3 s - CO - 3 min - CO or CO - 15 s - CO

Technical data

60…25060…250

120…240, 50/60 Hz

25 years

Rated voltage [kV]Number of interrupter units per poleRated power-frequency withstand [kV]voltage 1 min.Rated lightning impulse withstand [kV]voltage 1.2 / 50 µsRated switching impulse [kV]withstand voltageRated current up to [A]Rated short-time current (3 s) up to [kA]Rated peak withstand current up to [kA]Rated short-circuit-breaking [kA]current up toRated short-circuit making [kA]current up toRated duty cycleBreak time [cycles]Frequency [Hz]Operating mechanism typeControl voltage [V, DC]Motor voltage [V, DC]

[V, DC]Design data of the basic version:Clearance Phase/earth [mm]in air across the contact gap [mm]Minimum creepage Phase/earth [mm]distance across the contact gap [mm]DimensionsHeight [mm]Width [mm]Depth [mm]Distance between pole centers [mm]Weight of circuit-breaker [kg]Inspection after

72.5 123 145 170 245/300

1 1 1 1 1

140 230 275 325 460

325 550 650 750 1050

– – – – –/850

4000 4000 4000 4000 4000

40 40 40 40/50 50

108 108 108 135 135

40 40 40 40/50 50

108 108 108 135 135

3 3 3 3 3

50/60 50/60 50/60 50/60 50/60

700 1250 1250 1500 22001200 1200 1200 1400 1900/2200

2248 3625 3625 4250 6150/76263625 3625 3625 4250 6125/7500

2750 3300 3300 4030 5220/55203200 3900 3900 4200 6600/7000 660 660 660 660 8001350 1700 1700 1850 2800/3000

1350 1500 1500 1600 3000

362 420

2 2

520 610

1175 1425

950 1050

4000 4000

63 63

170 170

63 63

170 170

3 3

50/60 50/60

2750 3400 2700 3200

7875 10375 9050 10500

4150 48008800 94003500 41003800 4100

4700 5000


Fig. 28a


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Fig. 28b * with closing resistor

3AT2/3AT3*

Electrohydraulic mechanism

O - 0.3 s - CO - 3 min - CO or CO - 15 s - CO

245 300 362 420 550

2 2 2 2 2

460 460 520 610 800

1050 1050 1175 1425 1550

– 850 950 1050 1175

4000 4000 4000 4000 4000

80 63 63 63 63

216 170 170 170 170

80 63 63 63 63

216 170 170 170 170

2 2 2 2 2

50/60 50/60 50/60 50/60 50/60

2200 2200 2700 3300 38002000 2400 2700 3200 3800

6050 6050 7165 9075 137506070 8568 9360 11390 13750

4490 4490 6000 6000 67007340 8010 9300 10100 136904060 4025 4280 4280 51353000 3400 3900 4300 5100

5980 6430 9090 8600 12500

362 420 550 800

4 4 4 4

520 610 800 1150

1175 1425 1550 2100

950 1050 1175 1425

4000 4000 4000 4000

80 80 63 63

200 200 160 160

80 80 63 63

200 200 160 160

2 2 2 2

50/60 50/60 50/60 50/60

2700 3300 3800 50004000 4000 4800 6400

7165 9075 10190 1386012140 12140 17136 22780

4990 6000 6550 840010600 11400 16600 222006830 6830 7505 90604350 4750 7200 10000

14400 14700 19200 23400

48…25048…250 or

208/120…500/289 50/60 Hz

25 years

3AT4/3AT5*


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Fig. 29b: SPS-2 circuit-breaker 170 kV

Circuit-breakersin dead-tank design

For certain substation designs, dead-tankcircuit-breakers might be required insteadof the standard live-tank breakers. Forthese purposes Siemens can offer thedead-tank circuit breaker types.

Main features at a glance

Reliable opening and closing

Proven contact and arc-quenchingsystem

Consistent quenching performancewith rated and short-circuit currentseven after many switching operations

Similar uncomplicated design for allvoltages

High-performance, reliable operatingmechanisms

Easy-to-actuate spring operatingmechanisms

Hydraulic operating mechanisms withon-line monitoring

Economy

Perfect finish Simplified, quick installation process Long maintenance intervals High number of operating cycles Long service life

Individual service

Close proximity to the customer Order specific documentation Solutions tailored to specific problems After-sales service available promptly

worldwide

The right qualifications

Expertise in all power supply matters 30 years of experience with SF6-insulat-

ed circuit breakers A quality system certified to ISO 9001,

covering development, manufacture,sales, installation and after-sales service

Test laboratories accredited to EN 45001and PEHLA/STL

Dead-Tank Circuit-Breakers for 72 kV up to 245 kV

Fig. 29a: SPS-2 circuit-breaker 72.5 kV


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Type SPS-2/3AP1-DT

38 48.3 72.5 121 145 169 242

80 105 160 260 310 365 425

200 250 350 550 650 750 900/1050

– – – – – – –/850

4000 4000 4000 4000 4000 4000 4000

40 40 40 63 63 63 63

Rated voltage [kV]

Rated power-frequency [kV]withstand voltage

Rated lighting impulse [kV]withstand voltage

Rated switching impulse [kV]withstand voltage

Rated nominal current up to [A]

Rated breaking current up to [kA]

Operating mechanism type

Technical data

Spring-stored-energy mechanism

Dead-Tank Circuit-Breakers for 72 kV up to 245 kV

Subtransmission breakerType SPS-2 and 3AP1-DT

Type SPS-2 power circuit-breakers(Fig. 29a/b) are designed as general, defi-nite-purpose breakers for use at maximumrated voltages of 72.5 and 245 kV.

The construction

The type SPS-2 breaker consists of threeidentical pole units mounted on a commonsupport frame. The opening and closingforce of the FA2/4 spring operating mecha-nism is transferred to the moving contactsof the interrupter through a system of con-necting rods and a rotating seal at the sideof each phase.The tanks and the porcelain bushingsare charged with SF6 gas at a nominalpressure of 6.0 bar. The SF6 serves as bothinsulation and arc-quenching medium.A control cabinet mounted at one endof the breaker houses the spring operatingmechanism and breaker control compo-nents.Interrupters are located in the aluminumhousings of each pole unit. The interrupt-ers use the latest Siemens puffer arc-quenching system.The spring operating mechanism is thesame design as used with the Siemens3AP breakers. This design has been in ser-vice for years, and has a well documentedreliability record.Customers can specify up to four (in somecases, up to six) bushing-type currenttransformers (CT) per phase. These CTs,mounted externally on the aluminum hous-ings, can be removed without disturbingthe bushings.

Operating mechanism

The type FA2/4 mechanically and electrical-ly trip-free spring mechanism is used ontype SPS-2 breakers. The type FA2/4 clos-ing and opening springs hold a charge forstoring ”open-close-open“ operationsA weatherproof control cabinet has a largedoor, sealed with rubber gaskets, for easyaccess during inspection and maintenance.Condensation is prevented by units offer-ing continuous inside/outside temperaturedifferential and by ventilation.

Fig. 30

Included in the control cabinet are neces-sary auxiliary switches, cutoff switch, latchcheck switch, alarm switch and operationcounter. The control relays and three con-trol knife switches (one each for the con-trol, heater and motor) are mounted on acontrol panel. Terminal blocks on the sideand rear of the housing are available forcontrol and transformer wiring.For non US markets the control cabinet isalso available similar to the 3AP cabinet(3AP1-DT).


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Type 3AT 2/3-DT

550

860

1800

1300

4000

50/63

Electrohydraulic mechanism

Rated voltage [kV]

Rated power-frequency [kV]withstand voltage

Rated lighting impulse [kV]withstand voltage

Rated switching impulse [kV]withstand voltage

Rated nominal current up to [A]

Rated breaking current up to [kA]

Operating mechanism type

Technical data

Dead-Tank Circuit-Breakers for 550 kV

Circuit-breakerType 3AT2/3-DT

Composite insulators

The 3AT2/3-DT is available with bushingsmade from composite insulators –this has many practical advantages.The SIMOTEC® composite insulators man-ufactured by Siemens consist of a basicbody made of epoxy resin reinforced glassfibre tubes. The external tube surface iscoated with vulcanized silicon. As is thecase with porcelain insulators, the externalshape of the insulator has a multishedprofile. Field grading is implemented bymeans of a specially shaped screeningelectrode in the lower part of the compos-ite insulator.The bushings and the metal tank of thecircuit-breaker surround a common gasvolume. The composite insulator used onthe bushing of the 3AT2/3-DT is a one-piece insulating unit. Compared with con-ventional housings, composite insulatorsoffer a wide range of advantages in termsof economy, efficiency and safety.

Interrupter unit

The 3AT2/3-DT pole consists of two break-ing units in series impressive in the sheersimplicity of their design. The proven Siemenscontact system with double graphite noz-zles assures faultless operation, consist-ently high arc-quenching capacity and along operating life, even at high switchingfrequencies. Thanks to constant further de-velopment, optimization and consistentquality assurance, Siemens arc-quencingsystems meet all the requirements placedon modern high-voltage technology.

Hydraulic drive

The operating energy required for the3AT2/3-DT interrupters is provided by thehydraulic drive, which is manufactured in-house by Siemens. The functional principleof the hydraulic drive constitutes a techni-cally clear solution which offers certainfundamental advantages.Hydraulic drives provide high amounts ofenergy economically and reliably. In thisway, even the most demanding switchingrequirements can be mastered in shortopening times.Siemens hydraulic drives are maintenance-free and have a particulary long operatinglife. They meet the strictest criteria forenviromental acceptability. In this respect,too, Siemens hydraulic drives have proventhemselves throughout years of operation.

Fig. 31


Fax: ++ 49-3 03 86-2 58 67


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Dead-Tank Circuit-Breakers for 550 kV

Fig. 32: The 3AT2/3-DT circuit-breaker with SIMOTEC composite insulator bushings


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MO arresters are used in medium, highand extra-high-voltage power systems.Here, the very low protection level and thehigh energy absorption capability providedduring switching surges are especially im-portant. For high voltage levels, the simpleconstruction of MO arresters is always anadvantage.Another very important advantage of MOarresters is their high degree of reliabilitywhen used in areas with a problematicclimate, for example in coastal and desertareas, or regions affected by heavy indus-trial air pollution. Furthermore, some spe-cial applications have become possibleonly with the introduction of MO arresters.One instance is the protection of capacitorbanks in series reactive-power compen-sation equipment which requires extremlyhigh energy absorption capabilities.

Arresters with polymer housings

Fig. 34 shows two Siemens MO arresterswith different types of housing. In additionto what has been usual up to now – theporcelain housing – Siemens offers alsothe latest generation of high-voltage surgearresters with polymer housing.

Surge Arresters

Introduction

The main task of an arrester is to protectequipment from the effects of overvolt-ages. During normal operation, it shouldhave no negative effect on the powersystem. Moreover, the arrester must beable to withstand typical surges withoutincurring any damage. Nonlinear resistorswith the following properties fulfill theserequirements: Low resistance during surges so that

overvoltages are limited High resistance during normal operation,

so as to avoid negative effects on thepower system and

Sufficient energy absorption capabilityfor stable operation

With this kind of nonlinear resistor, thereis only a small flow of current when contin-uous operating voltage is being applied.When there are surges, however, excessenergy can be quickly removed from thepower system by a high discharge current.

Fig. 33: Current/voltage characteristics of a non-linear MO arrester

Fig. 34: Measurement of residual voltage onporcelain-housed (foreground) and polymer-housed(background) arresters

Nonlinear resistors

Nonlinear resistors, comprising metaloxide (MO), have proved especially suita-ble for this.The nonlinearity of MO resistors is consid-erably high. For this reason, MO arresters,as the arresters with MO resistors areknown today, do not need series gaps.Siemens has many years of experiencewith arresters – with the previous gappedSiC-arresters and the new gapless MO ar-resters – in low-voltage systems, distribu-tion systems and transmission systems.They are usually used for protecting trans-formers, generators, motors, capacitors,traction vehicles, cables and substations.There are special applications such as theprotection of Equipment in areas subject to

earthquakes or heavy pollution Surge-sensitive motors and dry-type

transformers Generators in power stations with

arresters which posses a high degreeof short-circuit current strength

Gas-insulated high-voltage metal-enclosed switchgear (GIS)

Thyristors in HVDC transmissioninstallations

Static compensators Airport lighting systems Electric smelting furnaces in the glass

and metals industries High-voltage cable sheaths Test laboratory apparatus.

Current through arrester Ia [A]

150 °C

20 °C115 °C

2

1

010-4

Rated voltage ÛR

Continuous operatingvoltage ÛC

10-3 10-2 10-1 102 103 1041 10

Arrester voltage referredto continuous operatingvoltage Û/ÛC


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Seal

Pressure relief diaphragm

Compressing spring

Metal oxide resistors

Composite polymer housingFRP tube/silicon sheds

Flange with gas diverter nozzle

Surge Arresters

Fig. 35: Cross-section of a polymer-housed arrester

Fig. 36: Gas-insulated metal-enclosed arrester(GIS arrester)

Fig. 35 shows the sectional view of suchan arrester. The housing consists of a fiber-glass-reinforced plastic tube with insulatingsheds made of silicon rubber. The advan-tages of this design which has the samepressure relief device as an arrester withporcelain housing are absolutely safe andreliable pressure relief characteristics, highmechanical strength even after pressurerelief and excellent pollution-resistant prop-erties. The very good mechanical featuresmean that Siemens arresters with polymerhousing (type 3EQ/R) can serve as postinsulators as well. The pollution-resistantproperties are the result of the water-repel-lent effect (hydrophobicity) of the siliconrubber, which even transfers its effects topollution.

The polymer-housed high-voltage arrest-er design chosen by Siemens and the high-quality materials used by Siemens providea whole series of advantages includinglong life and suitability for outdoor use,high mechanical stability and ease of dis-posal.Another important design shown in Fig. 36are the gas-insulated metal-enclosed surgearresters (GIS arresters) which have beenmade by Siemens for more then 25 years.There are two reasons why, when GIS ar-resters are used with gas-insulated switch-gear, they usually offer a higher protectivesafety margin than when outdoor-type ar-resters are used (see also IEC 60099-5,1996-02, Section 4.3.2.2.): Firstly, they canbe installed closer to the item to be pro-tected so that traveling wave effects can

be limited more effectively. Secondly, com-pared with the outdoor type, inductance ofthe installation is lower (both that of theconnecting conductors and that of the ar-rester itself). This means that the protec-tion offered by GIS arresters is much betterthan by any other method, especially in thecase of surges with a very steep rate ofrise or high frequency, to which gas-insu-lated switchgear is exceptionally sensitive.Please find an overview of the completerange of Siemens arresters in Figs. 37 and 38,pages 26 and 27.

Access cover withpressure reliefdevice and filter

Spring contact

Enclosure

Grading hood

Metal-oxide resistors

Supporting rods

SF6-SF6 bushing(SF6-Oil bushing on request)


Fax: ++49-3 03 86-26721e-mail: [email protected]


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Low-Voltage and Medium-Voltage Arrestersand Limiters (230/400 V to 52 kV)

Fig. 37: Low and medium-voltage arresters

Type Low-voltage arresters Medium-voltage arrestersand limiters

3EA2 3EF13EF23EF33EF43EF5

3EC3 3EE2 3EH2 3EG5 3EK5 3EK7 3EQ1-B

Low-voltageover-headline sys-tems

Motors,dry-typetransformers,airfield light-ing systems,sheath voltagelimiters,protectionof convertersfor drives

DC sys-tems (loco-motives,overheadcontactlines)

Gene-rators,motors,meltingfurnaces,6-arresterconnec-tions,powerplants

Distri-butionsystemsmetal-enclosedgas-in-sulatedswitch-gearwithplug-inconnec-tion

Distri-butionsystemsandmedium-voltageswitch-gear



AC and DClocomotives,overheadcontact lines

1 10 3 30 45 30 60 30 25

12 4 36 52 36 72.5 36 30

1 15 4 45 52 45 75 45 37 (AC) 4 (DC)

5 1 10 10 10 10 10 10 10

– 3EF1/2 0.83EF3 93EF4 12.53EF5 8

10 10 1.3 3 5 3 10

1 x 38020 x 250

3EF4 15003EF5 1200

1200 1200 200 300 500 300 1200

Line dis-connec-tion

40 40 300 16 20 20 20 40

Polymer Polymer Porcelain Porcelain Metal Porcelain Porcelain Polymer Polymer

Applications

Nom. syst. [kV]voltage (max.)

Highest [kV]voltage forequipment (max.)

Maximum [kV]ratedvoltage

Nominal [kA]dischargecurrent

Maximum [kJ/kV]energyabsorbingcapability(at thermalstability)

Maximum [A]longdurationcurrentimpulse,2 ms

Maximum [kA]short-circuitrating

Housingmaterial


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High-Voltage Arresters(72.5 to 800 kV)

Fig. 38: High-voltage arresters

Type Metal-oxide surge arresters3EP1 3EP4 3EP2 3EP3 3EQ1 3EQ4 3EQ3

3ER33EP2-K 3EP2-K3 3EP3-K

Medium-andhigh-voltagesystems,outdoorinstal-lations


High-voltagesystems,outdoorinstal-lations

High-voltagesystems,outdoorinstal-lations,HVDC,SC & SVCappli-cations


High-voltagesystems,outdoorinstal-lations

High-voltagesystems,outdoorinstal-lations,HVDC,SC & SVCappli-cations

High-voltagesystems,metal-enclosedgas-insulatedswitch-gear



60 150 500 765 275 500 765 150 150 500

72.5 170 550 800 300 550 800 170 170 550

84 147 468 612 240 468 612 180 180 444

10 10 10/20 10/20 10 10/20 20 10/20 10/20 20

2 3 5 5 3 5 5 4 4 5

5 8 12.5 20 8 12.5 20 10 10 12.5

500 850 1500 3900 850 1500 3900 1200 1200 1500

40 65 65 100 50 65 80 – – –

2.12) 4.52) 12.52) 342)

63) 213) 723) – – –

Porcelain Porcelain Porcelain Porcelain Polymer1) Polymer1) Polymer1) Metal Metal Metal

Applications

Nom. syst. [kV]voltage(max.)

Highest [kV]voltage forequip. (max.)

Maximum [kV]ratedvoltage

Nominal [kA]dischargecurrent

Maximumlinedischargeclass

Maximum [kJ/kV]energyabsorbingcapability(at thermalstability)

Maximum [A]longdurationcurrentimpulse,2 ms

Maximum [kA]short-circuitrating

Minimum [kNm]2)

breakingmoment

Maximum [MPSL]permissibleserviceload

Housingmaterial1) Silicon rubber sheds 2) Acc. to DIN 48113 3) Acc. to IEC TC 37 WG5 03.99; > 50% of this value are maintained after pressure relief


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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


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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.


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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9

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

15.95

11.50

8.90Cable duct

40 MVA transformer

Radiators

Compensator

2.20

–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.


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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: High power ratings

(transmission capacity up to 3000 MVAper System)

High overload capability Suitable for long distances

(100 km and more without compensa-tion of reactive power)

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

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

Multiple earthing points possible Non-flammable, no fire risk in case of

failuresThe 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 is a highly reliable system in termsof mechanical and electrical failures. Oncea system is commissioned and in service,it runs reliably without any dielectrical ormechanical failures as experience over thecourse of 20 years shows. 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. 57 shows the arrangement of sixphases in a tunnel.

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 given so that compen-sation of reactive power is not needed,even for long distances of 100 km andmore.

Reduction of SF6 content

Several tests have been carried out inSiemens facilities as well as in other testlaboratories world-wide since many years.Results of these investigations show thatthe bulk of the insulating gas for industrialprojects involving a considerable amountof gas should be nitrogen, a nontoxic nat-ural gas.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.

Fig. 58: Long-term test set-up at the IPH, Berlin

The characteristics of N2/SF6 gas mixturesshow that with an SF6 content of only15–25% and a slightly higher pressure,the insulating capability of pure SF6 can beattained. Besides, the arcing behavior isimproved through this mixture. Tests haveproven that there would be no externaldamage or fire caused by an internal fail-ure.The technical data of the GIL are shown inFig. 59.

Fig. 57: GIL arrangement in the tunnel of the Wehrpumped storage station(4000 m length, in service since 1975)


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Technical data

up to 550 kV

2000 – 4600 A

1500 – 3000 MVA

≈ 60 nF/km

1–100 km

10%/90%up to 35%/65%

directly buried

in tunnels/sloping galleries/vertical shafts

open air installation

Rated voltage

Rated current lr

Transmissioncapacity

Capacitance

Typical length

Gas mixture SF6/N2ranging from

Laying

clean assembly and productivity is enhan-ced by a high level of automation of theoverall process.

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 active cor-rosion protection system provides protec-tion potential in relation to the aluminumsheath. An important requirement takeninto account is the situation of an earthfault with a high current of up to 63 kA toearth.

Testing

The GIL is already tested according tothe report IEC 61640 (1998) “Rigid high-voltage, gas-insulated transmission linesfor voltages of 72.5 kV and above.”

Long-term performances

Besides nearly 25 years of field experiencewith GIL installations world wide, the long-term performance of the GIL for long-dis-tance installations has been proven by theindependent test laboratory IPH, Berlin,Germany and the Berlin power utilityBEWAG according to long-term test proce-

D

Gas-Insulated Transmission Lines (GIL)

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 to highproductivity in the welding process andtherefore speeds up laying. The reliabilityof the welding process is controlled by anintegrated computerized qualityassurance system.

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 ofseasons. The laying techniques for pipe-lines have been improved over many yearsand they are applicable for GIL as a ”pipe-line for electrical current“too. However,the GIL needs slightly different treatmentwhere the pipeline technique has to beadapted.The laying process is illustratedin Fig. 60.The assembly area needs to be protectedagainst dust, particles, humidity and otherenvironmental factors that might disturbthe dielectric system. Clean assemblytherefore plays an important role in settingup cross-country GILs under normal envi-ronmental conditions. The combination of

Fig. 59: GIL technical data

Fig. 60: GIL laying technique

Fig. 61: Siemens lab prototype for dielectric tests

dures for power cables. The test proce-dure consisted of load cycles with doubledvoltage and increased current as well asfrequently repeated high-voltage tests.The assembly and repair procedures underrealistic site conditions were examinedtoo. The Siemens GIL is the first one inthe world that has passed these tests,without any objection. Fig. 58 shows thetest setup arranged in a tunnel of 3 m di-ameter, corresponding to the tunnel usedin Berlin for installing a 420 kV transmis-sion link through the city.

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 wasthe 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. 57). Thisconnection was commissioned in 1975 atthe Wehr pumped storage station in theBlack Forest in Southern Germany.


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


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Overhead Power Lines

Introduction

Since the very beginning of electric power,overhead lines have constituted the mostimportant component for transmission anddistribution. Their portion of overall lengthof electric circuits depends on the voltagelevel as well as on local conditions andpractice. In densely populated areas likeCentral Europe, underground cables prevailin the distribution sector and overheadpower lines in the high-voltage sector. Inother parts of the world, for example inNorth America, overhead lines are oftenused also for distribution purposes withincities. Siemens has planned, designed anderected overhead power lines on all impor-tant voltage levels in many parts of theworld.

Selection of line voltage

For distribution and transmission of electricpower standardized voltages according toIEC 60038 are used worldwide.For three-phase AC applications, three volt-age levels are distinguished: The low-voltage level up to 1 kV The medium-voltage level between 1 kV

and 36 kV and The high-voltage level up to 800 kV.For DC transmission the voltages varyfrom the mentioned data.Low-voltage lines serve households andsmall business consumers. Lines on themedium-voltage level supply small settle-ments, individual industrial plants andlarger consumers, the electric power beingtypically less than 10 MVA per circuit.The high-voltage circuits up to 145 kVserve for subtransmission of the electricpower regionally and feed the medium-voltage network. This high-voltage levelnetwork is often adopted to support themedium-voltage level even if the electricpower is below 10 MVA. Moreover, someof these high-voltage lines also transmitthe electric power from medium-sized gen-erating stations, such as hydro plants onsmall and medium rivers, and supply large-scale consumers, such as sizable industrialplants or steel mills. They constitute theconnection between the interconnectedhigh-voltage grid and the local distributionnetworks. The bandwidth of electrical pow-er transported corresponds to the broadrange of utilization, but, rarely exceeds100 MVA per circuit, while the surge im-pedance load is 35 MVA (approximately).

2000

1000

500

200

100

50

20

1010 20 50 100 200 500

km

MW Power per circuit

110 kV

220 kV

380 kV

750 kV

Transmission distance

245 kV lines were used in Central Europefor interconnection of utility networks be-fore the changeover to the 420 kV level forthis purpose. Long-distance transmission,for example between the hydro powerplants in the Alps and the consumers, wasperformed out by 245 kV lines.Nowadays, the importance of 245 kVlines is decreasing due to the applicationof 420 kV.

The 420 kV level represents the highestvoltage used for AC transmission inCentral Europe with the task of intercon-necting the utility networks and of trans-mitting the energy over long distances.Some 420 kV lines connect the nationalgrids of the individual European countriesenabling Europewide interconnected net-work operation. Large power plants, suchas nuclear stations, feed directly into the420 kV network. The thermal capacity ofthe 420 kV circuits may reach 2000 MVAwith a surge impedance load of approxi-mately 600 MVA and a transmission capacityup to 1200 MVA.

Fig. 62: Selection of rated voltage for power transmission


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24

50

9.6

210

7

0.59

0.39

9.7

3.4

1.2

0.04

360

–

Rated voltage

20[kV]

Highest system voltage [kV]

Nominalcross-section [mm2]

Conductor diameter [mm]

Ampacity (at 80 °C con-ductor temperature) [A]

Thermal capacity [MVA]

Resistance at 20 °C [Ω/km]

Reactance at 50 Hz [Ω/km]

Effectivecapacitance [nF/km]

Capacitanceto ground [nF/km]

Charging power [kVA/km]

Ground-fault current [A/km]

Surge impedance [Ω]

Surgeimpedance load [MVA]

120

15.5

410

14

0.24

0.34

11.2

3.6

1.4

0.04

310

–

123

150

17.1

470

90

0.19

0.41

9.3

4.0

35

0.25

375

32

300

24.5

740

140

0.10

0.38

10

4.2

38

0.25

350

35

245

435

28.8

900

340

0.067

0.4

9.5

4.8

145

0.58

365

135

bundle2x240

2x21.9

1290

490

0.059

0.32

11.5

6.3

175

0.76

300

160

420

bundle4x240

4x21.9

2580

1700

0.030

0.26

14.4

6.5

650

1.35

240

600

bundle2x560

2x32.2

2080

1370

0.026

0.27

13.8

6.4

625

1.32

250

577

800

bundle4x560

4x32.2

4160

5400

0.013

0.28

13.1

6.1

2320

2.48

260

2170

110 220 380 750


The voltage level has to be selected basedon the duty of the line within the networkor on results of network planning. Siemenshas carried out such studies for utilities allover the world.

Selection of conductorsand ground wires

Conductors represent the most importantcomponents of an overhead power linesince they have to ensure economical andreliable transmission and contribute con-siderably to the total line costs.For many years aluminum and its alloyshave been the prevailing conducting mate-rials for power lines due to the favorableprice, the low weight and the necessity ofcertain minimum cross-sections.The conductors are prone to corrosion.Aluminum, in principle, is a very corrosivemetal. However, a dense oxide layer isformed which stops further corrosive at-tacks. Therefore, aluminum conductorsare well-suited also for corrosive areas, forexample a maritime climate.For aluminum conductors there are a num-ber of different designs in use. All-aluminumconductors (AAC) have the highest conduc-tivity for a given cross-section, howeverpossess only a low mechanical strength,which limits their application to shortspans and low tensile forces. To increasethe mechanical strength, wires made ofaluminum-magnesium-silicon alloys areadopted, the strength of which is twicethat of pure aluminum.All-aluminum and aluminum alloy con-ductors have shown susceptibility againsteolian vibrations. Compound conductorswith a steel core, so-called aluminumcables, steel reinforced (ACSR), avoid thisdisadvantage. The ratio between aluminumand steel ranges from 4.3:1 to 11:1. Expe-rience has demonstrated that ACSR has along life, too.Conductors are selected according to elec-trical, thermal, mechanical and economicaspects. The electric resistance as a resultof the conducting material and its cross-section is the most important featureaffecting the voltage drop and the energylosses along the line and, therefore, thetransmission costs. The cross-section hasto be selected such that the permissibletemperatures will not be exceeded duringnormal operation as well as under shortcircuit. With increasing cross-section theline costs increase, while the costs forlosses decrease. Depending on the dutyof a line and its power, a cross-section canbe determined which results in lowesttransmission costs. This cross-sectionshould be aimed for. The heat balance ofohmic losses and solar radiation againstconvection and radiation determines theconductor temperature. A current densityof 0.5 to 1.0 A /mm2 has proven to be aneconomical solution.

Overhead power lines with voltages high-er than 420 kV are needed to economicallytransmit bulk electric power over long dis-tances, a task typically arising when utiliz-ing hydro energy potentials far away fromconsumer centers. Fig. 62 depicts sche-matically the range of application for theindividual voltage levels dependingon the distance of transmission and thepower rating.

Fig. 63: Electric characteristics of AC overhead power lines (Data refer to one circuit of a double-circuit line)


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High voltage results in correspondinglyhigh-voltage gradients at the conductorsand in corona-related effects such as visi-ble discharges, radio interference, audiblenoise and energy losses. When selectingthe conductors, the voltage gradient hasto be limited to values between 15 and17 kV/cm. This aspect is important forlines with voltages of 245 kV and above.Therefore, bundle conductors are adoptedfor extra-high-voltage lines. Fig. 63 showstypical conductor configurations.From the mechanical point of view theconductors have to be designed for every-day conditions and for maximum loadsexerted on the conductor by wind and ice.As a rough figure, an everyday stress ofapproximately 20% of the conductor ulti-mate tensile stress can be adopted, result-ing in a limited risk of conductor damage.Ground wires can protect a line againstdirect lightning strokes and improve thesystem behavior in case of short circuits;therefore, lines with single-phase voltagesof 110 kV and above are usually equippedwith ground wires. Ground wires madeof ACSR with a sufficiently high aluminumcross-section satisfy both requirements.

Selection of insulators

Overhead line insulators are subject toelectrical and mechanical stress since theyhave to insulate the conductors from po-tential to ground and must provide physicalsupports. Insulators must be capable ofwithstanding these stresses under all con-ditions encountered in a specific line.The electrical stresses result from The power frequency voltage Temporary overvoltages at power

frequency and Switching and lightning overvoltages.Various insulator designs are in use,depending on the requirements and theexperience with certain insulator types.Cap and pin-type insulators (Fig. 64) aremade of porcelain or glass. The individualunits are connected by fittings of malleablecast iron. The insulating bodies are notpuncture-proof which is the reason for rel-atively numerous insulator failures.In Central Europe long-rod insulators(Fig. 65) are most frequently adopted.These insulators are puncture-proof. Fail-ures under operation are extremely rare.Long-rod insulators show a superior be-havior especially under pollution. The ten-sile loading of the porcelain body formsa disadvantage, which requires relativelylarge cross-sections. Composite insulatorsare made of a core with fiberglass-rein-forced resin and sheds of differing plasticmaterials. They offer light weight and hightensile strength and will gain increasingimportance for high-voltage lines.Insulator sets must provide a creepagepath long enough for the expected pollu-tion level, which is classified accordingto IEC 60815 from light with 16 mm/kV upto very heavy with 31 mm/kV.To cope with switching and lightning over-voltages, the insulator sets have to be de-signed with respect to insulation coordina-tion according to IEC 60071-1. Thesedesign aspects determine the gap be-tween the grounded fittings and the liveparts.Suspension insulator sets carry the con-ductor weight and are arranged more orless vertically. There are I-shaped (Fig. 66a)and V-shaped sets in use. Single, double ortriple sets cope with the mechanical load-ings and the design requirements.Tension insulator sets (Fig. 66b, c) termi-nate the conductors and are arranged inthe direction of the conductors. They areloaded by the conductor tensile force andhave to be rated accordingly.

Fig. 64: Cap and pin-type insulator

Fig. 65: Long-rod insulator with clevis and tongueconnection


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Cross arm

Conductor

Cross arm

ConductorCross arm


Fig. 66b: Double tension insulator set for 245 kV (elevation)

Fig. 66a: I-shaped suspension insulator set for 245 kV

Fig. 66c: Double tension insulator set for 245 kV (plan)


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Selection and design of supports

Together with the line voltage, number ofcircuits and type of conductors the config-uration of the circuits determines the de-sign of overhead power lines. Additionally,lightning protection by ground wires, theterrain and the available space at the towersites have to be considered. In denselypopulated areas like Central Europe, thewidth of right-of-way and the space for thetower sites are limited. In the case of ex-tra-high voltages the conductor configura-tion affects the electrical characteristicsand the transmission capacity of the line.Very often there are contradicting require-ments, such as a tower height as low aspossible and a narrow right-of-way, whichcan only be met partly by compromises.The mutual clearance of the conductorsdepends on the voltage and the conductorsag. In ice-prone areas conductors shouldnot be arranged vertically in order to avoidconductor clashing after ice shedding.For low- and medium-voltage lines horizon-tal conductor configurations prevail whichfeature line post insulators as well as sus-pension insulators. Preferably poles madeof wood, concrete or steel are used.Fig. 67 shows some typical line configura-tions. Ground wires are omitted at thisvoltage level.For high and extra-high-voltage power linesa large variety of configurations are availa-ble which depend on the number of cir-cuits and on local conditions. Due to thevery limited right-of-way, more or less allhigh-voltage lines in Central Europe com-prise at least two circuits. Fig. 68 shows aseries of typical tower configurations. Ar-rangement e) is called the ”Danube“ con-figuration and is most often adopted. Itrepresents a fair compromise with respectto width of right-of-way, tower height andline costs.For lines comprising more than two cir-cuits there are many possibilities for con-figuring the supports. In the case of cir-cuits with differing voltages those circuitswith the lower voltage should be arrangedin the lowermost position (Fig. 68g).The arrangement of insulators dependson the task of a support within the line.Suspension towers support the conductorsin straight-line sections and at small bends.This tower type results in the lowestcosts; special attention should therefore bepaid to using this tower type as often aspossible.

Fig. 67: Configurations of medium-voltage supports

Fig. 68: Tower configurations for high-voltage lines

a b c d

a b c d

e f g h


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Angle towers have to carry the conductortensile forces at angle points of the line.The tension insulator sets permanentlyexert high forces on the supports. Variousloading conditions have to be met whendesigning angle towers. The climatic con-ditions are a determining factor as well.Finally, dead-end towers are used at theends of a transmission line. They carry thetotal conductor tensile forces of the con-nection to the substations.Depending on the size of the supportsand the acting forces, differing designs andmaterials are adopted. Poles made ofwood, concrete or steel are very oftenused for low and medium-voltage lines.Towers with lattice steel design, however,prevail at voltage levels of 110 kV andabove (Fig. 69). When designing the sup-port a number of conditions have to beconsidered. High wind and ice loads causethe maximum forces to act on suspensiontowers. In ice-prone areas unbalanced con-ductor tensile forces can result in torsionalloading. Additionally, special loading condi-tions are adopted for the purpose of failurecontainment, i.e. to limit the extent ofdamage. Finally, provisions have to bemade for construction and maintenanceconditions.Siemens adopts modern computer pro-grams for tower design in order to opti-mize the structures, select componentsand joints and determine foundationloadings.The stability of the support poles and tow-ers needs also accordingly designed foun-dations. The type of towers and poles, theloads, the soil conditions as well as the ac-cessibility to the line route and the availa-bility of machinery determine the selectionand design of foundation.Concrete blocks or concrete piers arein use for poles which exert bendingmoments on the foundation. For towerswith four legs a foundation is providedfor each individual leg (Fig. 70). Pad-and-chimney and concrete block foundationsrequire good bearing soil conditionswithout ground water. Driven or auguredpiles and piers are adopted for low bearingsoil, for sites with bearing soil in a greaterdepth and for high ground water level.In this case the soil conditions must permitpile driving. Concrete slabs can be usedfor good bearing soil, when subsoil andground water level prohibit pad and chim-ney foundations as well as piles. Siemenscan design all types of foundation and hasthe necessary equipment, such as piledrivers, grouting devices, soil and rockdrills, at its command to build all types ofpower line foundations. Fig. 70: Foundations for four-legged towers

Fig. 69: Lattice steel towers of a high-voltage line

Pad-and-chimneyfoundation

Rock anchorfoundation

Auger-boredfoundation

Pile foundation


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Fig. 71: Line profile established by computer

2T+0DH

1WA+0

DA

300.70302.50

232.50

255.00

11

11

f40=fE =

16.2013.00

292.00

279.00282.00

10.0016.00

0.47 292.00

5.746.07

f40=6.15fE =6.60

f40=2.11

281.50286.50 276.50

273.00273.50 280.00

280.50 284.50283.00

275.00275.50

270.50270.50

272.50270.00

267.50265.00

264.00263.o. D.175.00

36.00.0 66.0

106.0132.0 194.0

166.0 251.0264.0

291.0302.0

316.0331.0

346.0360.0

386.0405.0

426.0462

0.0 0.1 0.2 0.3 0.4

190.00g

171°0´Left conductor 251.47 m

190.00g

6.06.0

M20

251.0

M2160.0m

60.0m 50g

20 kV line 4.04.0 42

Roat


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4WA+0

DA

223.00

284.20

3T+8DH

Ground wire: ACSR 265/35 * 80.00 N/mm2

Conductor: ACSR 265/35 * 80.00 N/mm2

Equivalent sag: 11.21 m at 40 °CEquivalent span: 340.44 m

Arable land

ForestFallow land

Road

Stream

Meadow

270.00

292.50

16.00

1.45

f40=5.56fE =5.87

24.20

Bushes, heightup to 5 m

16.7515.86

7.558.44

17.3016.38

11.3812.29

f40=17.46fE =16.52

263.00

064.00

263.00266.50

265.50264.00

261.50258.50

260.00260.00

260.00247.50

236.00229.00

223.00215.50

209.00207.00

0426.0

462.0506.0

534.0544.0

586.0626.0

666.0676.0

688.0744.0

776.0804.0

826.0848.0

904.0910.0

4 0.5 0.6 0.7 0.8 0.9

425.0 13.9g

Road crossingat km 10.543

4.04.0 234.0

169.00g

5.8

Left conductor 235.45 mRoad to XXX 169.00g

152°6´5.8


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Route selectionand tower spotting

Route selection and planning representincreasingly difficult tasks since the right-of-way for transmission lines is limited andmany aspects and interests have to beconsidered. Route selection and approvaldepend on the statutory conditions andprocedures and always involve iterativestudies carried out in the office and sur-veys in the terrain which consider and eval-uate a great variety of alternatives. Afterdefinition of the route the longitudinal pro-file has to be surveyed, identifying allcrossings over roads, rivers, railways,buildings and other overhead power lines.The results are evaluated with computerprograms to calculate and plot the line pro-file. The towers are spotted by means ofcomputer programs as well, which takeinto account the conductor sags under dif-ferent conditions, the ground clearances,objects crossed by the line, technical dataof the available tower range, tower andfoundation costs and costs for compensa-tion of landowners. The result is an eco-nomical design of a line, which accountsfor all the technical and environmental con-ditions. Line planning forms the basis formaterial acquisition and line erection.Fig. 71 shows a line profile establishedby computer.

Siemens’ activities andexperience

Siemens has been active in the overheadpower line field for more than 100 years.The activities comprise design and con-struction of rural electrification schemes,low and medium-voltage distribution lines,high-voltage lines and extra-high-voltageinstallations. To give an indication of whathas been carried out by Siemens, approxi-mately 20,000 km of high-voltage lines upto 245 kV and 10,000 km of extra-high-volt-age lines above 245 kV have been set upso far. Overhead power lines have beenerected by Siemens in Germany and Cen-tral Europe as well as in the Middle East,Africa, the Far East and South America.The 420 kV transmission lines across theElbe river in Germany comprising four cir-cuits and requiring 235 m tall towers aswell as the 420 kV line across the Bospho-rus in Turkey with a span of approximately1800 m (Fig. 72) are worthy of specialmention.


Fax: ++49-9131-33 5 44e-mail: [email protected]

Fig. 72: 420 kV line across the Bosphorus, longitudinal profile

BT2BS2BS1 suspension towertension towerBT

BSBT1

BosphorusEurope Asia

Dimensions in m

70

37.5124124

27.5

112 119 125 162.5

674 1757 668


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HVDC

When technical and/or economical feasibilityof conventional high voltage AC transmis-sion technology reach their limits, highvoltage DC can offer the solution, namely For economical transmission of bulk

power over long distances For interconnection of asynchronous

power grids For power transmission across the sea,

when a cable length is long For interconnection of synchronous but

weak power grids, adding to their stability For additional exchange of active power

with other grids without having to increasethe short-circuit power of the system

For increasing the transmission capacityof existing rights-of-way by changingfrom AC to DC transmission systemSiemens offers HVDC systems as

Back-to-Back (B/B) stations to interconnectasynchronous networks, without any DCtransmission line in between

Power transmission via Dc submarinecables

Power transmission via long-distance DCoverhead lines

Back-to-Back (B/B):

To connect asynchronous high voltagepower systems or systems with differentfrequencies.To stabilize weak AC links or to supplyeven more active power, where the ACsystem reaches the limit of short-circuitcapability.

High-Voltage Direct Current Transmission

Fig. 75: Long-distance transmission

Special features

Valve technology Simple, easy-to-maintain mechanical

design Use of fire-retardant, self-extinguish-

ing material Minimized number of electrical

connections Minimized number of components Avoidance of potential sources of

failure ”Parallel“ cooling for the valve levels Oxygen-saturated cooling water.After more than 20 years of operation, thy-ristor valves based on this technology havedemonstrated their excellent reliability. The recent introduction of direct light-

triggered thyristors with integrated over-voltage protection further simplifies thevalve and reduces maintenance require-ments.

Control systemIn our HVDC control system, high-perform-ance components with proven records inmany other standard fields of applicationhave been integrated, thus adding to theoverall reliability of the system.Use of ”state-of-the-art“ microprocessor

systems for all functions.Redundant design for fault-tolerantsystems.

Filter technologySingle, double and triple-tuned as wellas high-pass passive filters, or any combi-nation thereof, can be installed.Active filters, mainly for the DC circuit,are available.Wherever possible, identical filters areselected so that the performance does notsignificantly change when one filter hasto be switched off.

Turnkey serviceOur experienced staff are prepared to de-sign, install and commission the wholeHVDC system on a turnkey basis.

Project financingWe are in a position to assist our custom-ers in finding proper project financing, too.

General services Extended support to customers from the

very beginning of HVDC system plan-ning including– Feasibility studies– Drafting the specification– Project execution– System operation and– Long-term maintenance– Consultancy on upgrading/replace-

ment of components/redesign of olderschemes, e.g. retrofit of mercury-arcvalves or relay-based controls

Fig. 74: Submarine cable transmission

Fig. 76: Earthquake-proof, fire-retardant thyristor valves in Sylmar East, Los Angeles

Fig. 73: Back-to-back link between asynchronous grids

Cable transmission (CT):

To transmit power across the sea withcables to supply islands/offshore platformsfrom the mainland and vice-versa.

Long-distance transmission (LD):

For transmission of bulk power over longdistances (beyond approx. 600 km, consid-ered as the break-even distance).


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Rehabilitation andmodernization of existingHVDC stations (Fig. 78)

The integration of state-of-the-art micro-processor systems or thyristors allows theowner better utilization of his investment,e.g. Higher availability Fewer outages Lower losses Better performance values Less maintenance.Higher availability means more operatinghours, better utilization and higher profitsfor the owner.The new Human-Machine Interface (HMI)system enhances the user-friendliness andincreases the reliability considerably dueto the operator guidance. This rules outmaloperation by the operator, because anincorrect command will be ignored by theHMI.

Fig. 77: Conventional DC measuring device (1) vs. thenew hybrid-optical device (2) with compositeinsulator (3) shows the reduced space requirementfor the new system (installed at HVDC converter sta-tion Sylmar, USA)

Studies during contract execution on:– HVDC systems basic design– System dynamic response– Load flow and reactive power

balance– Harmonic voltage distortion– Insulation coordination– Interference of radio and PLC– Special studies, if any

Typical ratings

Some typical ratings for HVDC schemesare given below for orientation purposes only:B/B: 100 ... 600 MWCT: 100 ... 800 MWLD: 300 ... 3000 MW (bipolar),whereby the lower rating is mainly deter-mined by economic aspects and the higherone limited by the constraints of the inter-connected networks.

Innovations

In recent years, the following innovativetechnologies and equipment have for ex-ample been successfully implemented bySiemens in diverse HVDC projects world-wide: Direct light-triggered thyristors

(already mentioned above) Hybrid-optical DC measuring system

(Fig. 77) Active harmonic filters Advanced eletrode line monitoring of

bipolar HVDC systems An SF6 HVDC circuit-breaker for use as

Metallic Return Transfer Breaker, devel-oped from a standard AC high-voltagebreaker.


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Fig. 78: HVDC outdoor valves, 533 kV (Cahora Bassa Rehabilitation, Southern Africa)


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Fig. 79: Human-Machine Interface with structure of HVDC control system




SER

HMI

VCSPole 1

OLCPole 1

OLCSC

OLCPole 2

VCSPole 2

LAN

CLCVBEPole 1

CLCVBEPole 2

OLCPole 2

TFRTFR

DC Yard

DC Protection

Communi-cation link tothe load dis-patch center

Communi-cation link tothe remotestation

GPS

Communi-cation link tothe remotestation

HMI Human-machine InterfaceGPS Global Positioning SystemOLC Open-Loop ControlCLC Closed-Loop ControlVBE Valve Base ElectronicsVCS Valve Cooling SystemsSER Sequence of Event

RecordingTFR Transient Fault RecordingLAN Local Area Network


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Power Compensation in Transmission Systems

Fig. 80: STATCOM inverter hall

Introduction

In many countries increasing powerconsumption leads to growing and moreinterconnected AC power systems. Thesecomplex systems consist of all types ofelectrical equipment, such as power plants,transmission lines, switchgear transform-ers, cables etc., and the consumers.Since power is often generated in thoseareas of a country with little demand, thetransmission and distribution system hasto provide the link between power gener-ation and load centers.Wherever power is to be transported, thesame basic requirements apply: Power transmission must be economical The risk of power system failure must

be low The quality of the power supply must

be highHowever, transmission systems do notbehave in an ideal manner. The systemsreact dynamically to changes in active andreactive power, influencing the magnitudeand profile of the power systems voltage.

Examples:

A load rejection at the end of a long-dis-tance transmission line will cause highovervoltages at the line end. However, ahigh load flow across the same line willdecrease the voltage at its end.

The transport of reactive power througha grid system produces additional lossesand limits the transmission of activepower via overhead lines or cables.

Load-flow distribution on parallel lines isoften a problem. One line could be load-ed up to its limit, while another only car-ries half or less of the rated current.Such operating conditions limit the actu-al transmittable amount of active power.

In some systems load switching and/orload rejection can lead to power swingswhich, if not instantaneously damped,can destabilize the complete grid systemand then result in a “Black Out”.

Reactive power compensation helps toavoid these and some other problems.In order to find the best solution for a gridsystem problem, studies have to be car-ried out simulating the behavior of the sys-tem during normal and continuous operat-ing conditions, and also for transientevents. Study facilities which cover digitalsimulations via computer as well as analogones in a transient network analyzer labo-ratory are available at Siemens.

Further information please contact:



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1 Transformer2 Thyristor-controlled reactor (TCR)3 Fixed connected capacitor/filter bank4 Thyristor-switched capacitor bank (TSC)

3442

1

Concept Operating diagram

Un

Iind Icap



UN

Iind IcapUD

UN

I

US

Id

Fig. 83: STATCOM

Types of reactive powercompensation

Parallel compensation

Parallel compensation is defined as anytype of reactive power compensation em-ploying either switched or controlled units,which are connected parallel to the trans-mission network at a power system node.In many cases switched compensation(reactors, capacitor banks or filters) canprovide an economical solution for reactivepower compensation using conventionalswitchgear.

Static VAr compensator (SVC)

In comparison to mechanically-switchedreactive power compensation, controlledcompensation (SVC, Fig. 81) offers the ad-vantage that rapid dynamic control of thereactive power is possible within narrowlimits, thus maintaining reactive powerbalance.Fig. 82 is a general outline of the problem-solving applications of SVCs in high-voltagesystems.

STATCOM

The availability of high power gate-turn-off(GTO) thyristors has led to the develop-ment of a Static Synchronous Compensa-tor (STATCOM), Fig. 80, page 2/52.The STATCOM is an “electronic generator”of dynamic reactive power, which is con-nected in shunt with the transmission line(Fig. 83) and designed to provide smooth,continuous voltage regulation, to preventvoltage collapse, to improve transmissionstability and to dampen power oscillations.The STATCOM supports subcycle speed ofresponse (transition between full capaci-tive and full inductive rating) and superiorperformance during system disturbancesto reduce system harmonics and resonanc-es. Particular advantages of the equipmentare the compact and modular constructionthat enables ease of siting and relocation,as well as flexibility in future rating up-grades (as grid requirements change) andthe generation of reactive current irrespec-tive of network voltage.

Fig. 82: Duties of SVCs

Fig. 81: Static VAr compensator (SVC)

Voltage controlReactive power controlOvervoltage limitation at load rejectionImprovement of AC system stabilityDamping of power oscillationsReactive power flow controlIncrease of transmission capabilityLoad reduction by voltage reductionSubsynchronous oscillation damping


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Fig. 85: Static Synchronous Series Compensator (SSSC)

Series compensation

Series compensation is defined as insertionof reactive power elements into transmis-sion lines. The most common application isthe series capacitor.

Thyristor-ControlledSeries Compensation (TCSC)

By providing continuous control of trans-mission line impendance, the Thyristor Con-trolled Series Compensation (TCSC, Fig. 84)offers several advantages over conventionalfixed series capacitor installations. Theseadvantages include: Continuous control of desired

compensation level Direct smooth control of power flow

within the network Improved capacitor bank protection Local mitigation of subsynchronous

oscillations (SSR). This permits higherlevels of compensation in networkswhere interactions with turbine-generatortorsional vibrations or with other controlor measuring systems are of concern.

Damping of electromechanical (0.5–2 Hz)power oscillations which often arise be-tween areas in a large interconnectedpower network. These oscillations aredue to the dynamics of interarea powertransfer and often exhibit poor dampingwhen the aggregate power transfer overa corridor is high relative to the transmis-sion strength.

Synchronous Series Compensation (SSSC)

The Static Synchronous Series Compensa-tor (SSSC) is a solid-state voltage genera-tor connected in series with the transmis-sion line through an insertion transformer(Fig. 85). The generation of a boost voltageadvancing or lagging behind the line cur-rent by 90° affects the voltage drop causedat the line reactance and can be used todampen transient oscillations and controlreal power flow independent of the magni-tude of the line current.


I

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UD

Id

Inductive Capacitive

UT

UT

Bypass circuit breaker

Bypass switch

Bankdisconnectswitch 1

Bankdisconnectswitch 2MOV arrester

Dampingcircuit

Thyristor controlledreactor

Capacitors

Triggered spark gap

Valve arrester

Thyristorvalve


90° Ignition angle α

[Z]

Inductive Capacitive

Inadmissiblearea

180°

Fig. 84: Thyristor controlled Series Compensation (TCSC). Example: Single line diagram TCSC S. da Mesa


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Unified Power Flow Controller (UPFC)

The Unified Power Flow Controller (UPFC)is the fastest and most versatile FACTScontroller (Fig. 86). The UPFC constitutesa combination of the STATCOM and theSSSC. It can provide simultaneously andindependently real time control of all basicpower system parameters (transmissionvoltage, impedance and phase angle), de-terminig the transmitted real and reactivepower flow to optimize line utilization andsystem capability. The UPFC can enhancetransmission stability and dampen systemoscillations.


Comparison of reactive powercompensation facilities

The following tables show the character-istics and application areas of UPFC(Fig. 87a), parallel compensation and seriescompensation (Fig. 87b, page 2/56) andthe influence on various parameters suchas short-circuit rating, transmission phaseangle and voltage behavior at this load.

Fig. 86: Unified power-flow controller (UPFC)

Fig. 87a: Components for reactive power compensation, UPFC

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Compen-sationelement

Location Short-circuitlevel

Voltageinfluence

Transmis-sion phaseangle

Voltageafter loadrejection

ApplicationsBehavior of compensation element

Real and reactive powerflow control, enhancingtransmission stabilityand dampening systemoscillations

Limited bycontrol

ControlledControlledReducedUPFC

UPFC (Parallel and/or series compensation)

UPFCE U

Concept Vector diagram

GTOConverter 1

GTOConverter 2

Ua Ub

Ub

UT

Ua

UT


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Voltage stabilizationat high load

Reactive powercompensation at lowload; limitation oftemporary overvoltage

Reactive power andvoltage control,damping of powerswings to improvesystem stability

High

Low

Littleinfluence

Littleinfluence

Littleinfluence

Controlled

Voltagedrop

Voltagerise

Littleinfluence

Littleinfluence

Littleinfluence

StaticVAr com-pensator(SVC)

Shuntreactor

Shuntcapacitor

Compen-sationelement

Location Short-circuitlevel

Voltageinfluence

Transmis-sion phaseangle

Voltageafter loadrejection

ApplicationsBehavior of compensation element

SVCE U

Limited bycontrol

E U

E U

Long transmission lines,power flow distributionbetween parallel linesand SSR damping

Short lines, limitationof SC power

(Very) low

(Much)larger

Muchsmaller

Very good

(Very) slightReduced

VariableThyristorControlledSeriesCom-pensation(TCSC)

Seriesreactor

(Very) high

Long transmission lineswith high transmissionpower rating

Muchsmaller

Very goodIncreasedSeriescapacitor

(Very) low

TCSC

E U

E U

Real power flowcontrol, damping oftransient oscillations

Limited bycontrol

ControlledControlledReducedSSSC

E U

SSSC

Reactive power andvoltage control,damping of powerswings

Littleinfluence

ControlledNoinfluence

STATCOM Limited bycontrol

E UST

E U

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Series compensation

Parallel compensation


Fig. 87b: Components of reactive power compensation, parallel compensation/series compensation

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