Siemes Ais Designs

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

1

2

3

4

5

6

7

8

9

10

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

Siemens Power Engineering Guide · Transmission and Distribution · 4th Edition 2/5

1

2

3

4

5

6

7

8

9

10

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


1

2

3

4

5

6

7

8

9

10

-F1

2530

7600

1050

170017006300

700030006400

25307000

-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]


1

2

3

4

5

6

7

8

9

10

8000

30002000 2000

3000 4500 4500 3000 4000

7500 11500

-Q8 -Q0-Q1 -T1-T5

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

7500

8000

19000

11500

8000

3000

9500

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


1

2

3

4

5

6

7

8

9

10

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).


1

2

3

4

5

6

7

8

9

10


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

Documents

Siemes Ais Designs