abb special report 2008-02 38-42

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Small footprint,high performanceDesign of an air-insulated switchgear substation based on new technologyLei Jing, Hans-Erik Olovsson, Jianzhong Fan, Richard Thomas

As cities grow, so does their hunger for electrical power. To achievethe necessary bulk transmission, the highest voltage level of a cityspower supply is continuously changing: from 110 kV to 220 kV, evenreaching 500 kV in some mega-cities in China and other countries.This calls for extra-high-voltage (EHV) substations to act as load hubsin the city. However, such developments lead to a conflict betweensubstation footprint and power requirement. In general, the higher thevoltage level, the more power a substation handles and the larger thearea it needs. Such demands, however, conflict with typical limita-tions that are prevalent in city areas. The shortage of land is the mostimportant among these and the huge investment cost is also a veryserious challenge. Furthermore, as an energy distribution center forvery ma ny peopl e, such a substation must perform with highreliability and availability. All this underpins the case for a com-pact substation, featuring reduced customer costs and asm al le r fo ot pr in t wh il e maintaining high availability.

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Powering the economy


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39Special Report Dancing with the Dragon ABB Review

Small footprint, high performance


load-hub substations located in thecity center. The demand for and valueof land is so high, that any compact

substation solution becomes attractive.One obvious approach is to use gas-insulated switchgear (GIS), which

would occupy only 30,000 m 2 for thesame SLD as in 1 [1]. This will, how-ever, be more costly than air-insulatedsubstations. According to China StateGrid [1], a GIS substation requiresaround 40 percent higher investment.Therefore, an alternative for the tradi-tional air-insulated switchgear (AIS)substation, with less footprint andcustomer cost is required.

Safety, environment, andnoise are all factors to beconsidered in the approvalof a substation.

The technology solution Applying new technologies, ABB candesign AIS substations with reduced in-stallation cost and a smaller footprint.

New circuit breaker A section view of a 500 kV bay isshown in 3 . The diagram shows thatthe disconnectors take up most of thespace as each circuit breaker needstwo disconnectors for safe isolation.

With the modern and well proven SF 6 circuit breakers (CB) of the self blast

ly to install, not only because of thelarge numbers of intelligent electronicdevices (IED) and computers, but due

to the extensive cabling for measure-ment and control.

However, in an urban substation, thekey factor is land-related cost. Thepurchase is an integral part of thisprocess, but is only the last step. Un-like general commodities, land cannotbe obtained with money alone. Safety,environment, and noise are all factorsto be considered in the approval of asubstation. The smaller the plot ofland, the less impact a substation hason its surroundings.

1 shows the single-line diagram (SLD)of a 500 kV substation [1]. In this sub-station, there are six 500 kV diameters(1 circuit breaker scheme) andtwelve 220 kV double busbar bays.

In this substation, all primary equip-ment is so large that often an area of60,000 m 2 is used 2 . Obviously, it isdifficult to find a suitable location forsuch an installation in the city.

The fast-increasing power demand,however, makes such substations in-dispensable. Plans of the Beijing elec-tric power company see a 500 kV dou-ble-ring network around the city be-ing completed in 2010. This will fea-ture 10 substations (each for 500 kVand 2600 MW). These include four

Todays technology is making theseobjectives attainable. Firstly, newprimary equipment permits a drastic

reduction in the footprint area. A rev-olution in circuit-breaker design ledby ABB is allowing switchgear config-uration or even integration to be rede-fined, decreasing costs both in termsof land acquisition and equipmentcost. Secondly, innovative optical sen-sors are replacing the traditional ex-pensive and large current transformers(CT). These non-traditional CTs are sosmall that they can be easily integrat-ed with the breaker in the same cir-cuit. Thirdly, the use of such sensorsis an integral aspect of a digital sub-station. This not only enhances sub-station performance, but also saves oninvestment, eg, cables for secondaryinstrument transformer circuits and forthe control of circuit breakers, discon-nectors, and earthing switches.

In an urban substation,the key factor island-related cost.Traditional air-insulated substationsUtilities must meet huge constructionand installation costs when investingin a substation. Obviously, primaryequipment, such as transformers andcircuit breakers, are very expensive,especially when these are for extrahigh voltages. Further, the substationautomation system (SAS) is itself cost-

1 Single line diagram (SLD) of a typical 500 kV substation 2 Layout of a typical 500 kV substation using air-insulated switchgear(AIS)


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42 Special Report Dancing with the Dragon ABB Review

Small footprint, high performance


Lei Jing ABB Corporate ResearchBeijing, [email protected]

Hans-Erik Olovsson ABB Power Systems Vsters, [email protected]

Jianzhong Fan ABB Power Systems, HVDCBeijing, China

[email protected]

Richard Thomas ABB Power ProductsLudvika, [email protected]

References

[1] 500 kV Substation Typical Design, China StateGrid

[2] DCB Buyers and App lication Guide, ABB[3] Bohnert, K., Guggenbach, P. A revolution in high

dc current measurement. ABB R eview 1/2005,610.

bar system is justified without avail-ability being compromised. Compar-ing the layouts in 8 and 9 , it can beseen how busbar and related discon-nectors are eliminated, simplifyingthe layout.

The use of a combineddisconnecting circuitbreaker as primaryequipment opens theopportunity for greatlyimproved efficiency insubstation construction,operation and layout.

In addition, because FOCS and anintelligent interface are used, thecable and related auxiliaries canbe done away with, resulting in amuch simplified control setup andsimplifying connections to theprimary equipment.

8 Traditional switchgear layout with disconnectors and circuit breakers

Line Line

132 kV

Transformer Transformer

9 Switchgear with disconnecting circuit breakers (DCB)

Line Line

132 kV

Transformer Transformer

7 Digital substation configuration

Switching ahead An air insulated substat ion can bedesigned to be more reliable and costefficient by introducing new equip-ment and technologies. The use of acombined disconnecting circuit break-er as primary equipment opens theopportunity for greatly improvedefficiency in substation construction,operation and layout. The innovativecurrent sensor together with an intelli-gent interface enables the implemen-tation of the IEC 61850-based processbus protocol.

a SAS evolution

Technology Overviewconventional modern intelligent

Network level

Station level

Bay level

Process level

modern(retrofit)

intelligent(retrofit)

parallel,hartwired

caling

parallel,hartwired

caling

parallel,hartwired

caling Processbus

Interbaybus

Interbaybus

Stationbus

Stationbus

RTURTURTU

RTURTURTU

b IEC 61850 based SAS

Cigre 2008 ABB Substation Automation

IEC61850 based SA-System MicroSCADA RTU560 REL670 REC670 REF615

SCADA EMSDMS

Bay control

IEC 61850-8-1

IEC 61850-9-2

Stationcomputerand HMI RTU

380 kV

feederterminal

MUP

gateway

20 kV

Bay protection

abb special report 2008-02 38-42

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