FACTS Introduction

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FACTS – Flexible Alternating Current Transmission Systems

For Cost Effective and Reliable Transmission of Electrical Energy

Klaus Habur and Donal O’Leary (1)

Flexible alternating current transmissionsystems (FACTS) devices are used for thedynamic control of voltage, impedance andphase angle of high voltage AC lines. FACTSdevices provide strategic benefits forimproved transmission system managementthrough: better utilization of existingtransmission assets; increased transmissionsystem reliability and availability; increaseddynamic and transient grid stability;increased quality of supply for sensitiveindustries (e.g. computer chip manufacture);and enabling environmental benefits.Typically the construction period for a factsdevice is 12 to 18 months from contractsigning through commissioning. This paperstarts by providing definitions of the mostcommon application of FACTS devices aswell as enumerates their benefits (focussingon steady state and dynamic applications).Generic information on the costs andbenefits of FACTS devices is then providedas well as the steps for identification ofFACTS projects. The paper then discussesseven applications of FACTS devices inAustralia, Brazil, Indonesia, South Africa andthe USA. The paper concludes with somerecommendations on how the World Bankcould facilitate the increased usage ofFACTS.

Introduction

The need for more efficient electricity systemsmanagement has given rise to innovativetechnologies in power generation andtransmission. The combined cycle power stationis a good example of a new development inpower generation and flexible AC transmissionsystems, FACTS as they are generally known,are new devices that improve transmissionsystems.

Worldwide transmission systems are undergoingcontinuous changes and restructuring. They are

becoming more heavily loaded and are beingoperated in ways not originally envisioned.Transmission systems must be flexible to reactto more diverse generation and load patterns. Inaddition, the economical utilization oftransmission system assets is of vitalimportance to enable utilities in industrializedcountries to remain competitive and to survive.In developing countries, the optimized use oftransmission systems investments is alsoimportant to support industry, createemployment and utilize efficiently scarceeconomic resources.

Flexible AC Transmission Systems (FACTS) is atechnology that responds to these needs. Itsignificantly alters the way transmissionsystems are developed and controlled togetherwith improvements in asset utilization, systemflexibility and system performance.

What are FACTS devices?

FACTS devices are used for the dynamic controlof voltage, impedance and phase angle of highvoltage AC transmission lines. Below thedifferent main types of FACTS devices aredescribed:

Static Var Compensators (SVC’s), the mostimportant FACTS devices, have been used for anumber of years to improve transmission lineeconomics by resolving dynamic voltageproblems. The accuracy, availability and fastresponse enable SVC’s to provide highperformance steady state and transient voltagecontrol compared with classical shuntcompensation. SVC’s are also used to dampenpower swings, improve transient stability, andreduce system losses by optimized reactivepower control.

Thyristor controlled series compensators(TCSCs) are an extension of conventional seriescapacitors through adding a thyristor-controlledreactor. Placing a controlled reactor in parallel

FACTS – For cost effective and reliable transmission of electrical energy

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with a series capacitor enables a continuous andrapidly variable series compensation system.The main benefits of TCSCs are increasedenergy transfer, dampening of poweroscillations, dampening of subsynchronousresonances, and control of line power flow.

STATCOMs are GTO (gate turn-off typethyristor) based SVC’s. Compared withconventional SVC’s (see above) they don’trequire large inductive and capacitivecomponents to provide inductive or capacitivereactive power to high voltage transmissionsystems. This results in smaller landrequirements. An additional advantage is thehigher reactive output at low system voltageswhere a STATCOM can be considered as acurrent source independent from the systemvoltage. STATCOMs have been in operation forapproximately 5 years.

Unified Power Flow Controller (UPFC).Connecting a STATCOM, which is a shuntconnected device, with a series branch in thetransmission line via its DC circuit results in aUPFC. This device is comparable to a phaseshifting transformer but can apply a seriesvoltage of the required phase angle instead of avoltage with a fixed phase angle. The UPFCcombines the benefits of a STATCOM and aTCSC.

Exhibit 1: UPFC circuit diagram

The section on Worldwide Applications containsdescriptions of typical applications for FACTSdevices.

Benefits of utilizing FACTS devicesThe benefits of utilizing FACTS devices inelectrical transmission systems can besummarized as follows:

• Better utilization of existing transmissionsystem assets

• Increased transmission system reliabilityand availability

• Increased dynamic and transient gridstability and reduction of loop flows

• Increased quality of supply for sensitiveindustries

• Environmental benefits

Better utilization of existing transmissionsystem assetsIn many countries, increasing the energytransfer capacity and controlling the load flow oftransmission lines are of vital importance,especially in de-regulated markets, where thelocations of generation and the bulk load centerscan change rapidly. Frequently, adding newtransmission lines to meet increasing electricitydemand is limited by economical andenvironmental constraints. FACTS devices helpto meet these requirements with the existingtransmission systems.

Increased transmission system reliabilityand availabilityTransmission system reliability and availability isaffected by many different factors. AlthoughFACTS devices cannot prevent faults, they canmitigate the effects of faults and make electricitysupply more secure by reducing the number ofline trips. For example, a major load rejectionresults in an over voltage of the line which canlead to a line trip. SVC’s or STATCOMscounteract the over voltage and avoid linetripping.

Increased dynamic and transient gridstabilityLong transmission lines, interconnected grids,impacts of changing loads and line faults cancreate instabilities in transmission systems.These can lead to reduced line power flow, loopflows or even to line trips. FACTS devicesstabilize transmission systems with resulting


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higher energy transfer capability and reducedrisk of line trips.

Increased quality of supply for sensitiveindustriesModern industries depend upon high qualityelectricity supply including constant voltage, andfrequency and no supply interruptions. Voltagedips, frequency variations or the loss of supplycan lead to interruptions in manufacturingprocesses with high resulting economic losses.FACTS devices can help provide the requiredquality of supply.

Environmental benefitsFACTS devices are environmentally friendly.They contain no hazardous materials andproduce no waste or pollutanse. FACTS helpdistribute the electrical energy moreeconomically through better utilization of existinginstallations thereby reducing the need foradditional transmission lines.

Applications and technical benefits of FACTS devices

Exhibits 2 to 4 below describe the technicalbenefits of the principal FACTS devicesincluding steady state applications in addressingproblems of voltage limits, thermal limits, loopflows, short circuit levels and subsynchronousresonance. For each problem the conventionalsolution (e.g. shunt reactor or shunt capacitor) isalso provided (as well as for dynamicapplications – see below), as well as dynamicapplications of FACTS in addressing problemsin transient stability, dampening, postcontingency voltage control and voltage stability.FACTS devices are required when there is aneed to respond to dynamic (fast-changing)network conditions. The conventional solutions

are normally less expensive than FACTSdevices – but limited in their dynamic behavior. Itis the task of the planners to identify the mosteconomic solution.In Exhibits 3 and 4 information is provided onFACTS devices with extensive operationalexperience and widespread use such as SVC,STATCOM, TCSC and UPFC. In addition,information is provided on FACTS devices thatare either under discussion, development or asprototype in operation such as the thyristorcontrolled phase-angle regulator (TCPAR); thethyristor controlled voltage limiter (TCVL); andthe thyristor switched series capacitor (TCSC).

Technical benefits of the main FACTS devices

Exhibit 2: Benefits of FACTS devices for different applications

Better


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Steady state applications of FACTS

Issue Problem Corrective Action Conventional solution FACTS deviceLow voltage at heavyload

Supply reactive power Shunt capacitor, Seriescapacitor

SVC, TCSC, STATCOM

Remove reactive powersupply

Switch EHV line and/orshunt capacitor

SVC, TCSC, STATCOMHigh voltage at light load

Absorb reactive power Switch shunt capacitor,shunt reactor

SVC, STATCOM

Absorb reactive power Add shunt reactor SVC, STATCOMHigh voltage followingoutage Protect equipment Add arrestor SVC

Supply reactive power Switch shunt capacitor,reactor, series capacitor

SVC, STATCOMLow voltage followingoutage

Prevent overload Series reactor, PAR TCPAR, TCSC

Voltage limits

Low voltage andoverload

Supply reactive powerand limit overload

Combination of two ormore devices

TCSC, UPFC,STATCOM, SVC

Add line or transformer TCSC, UPFC, TCPARLine or transformeroverload

Reduce overloadAdd series reactor SVC, TCSC

Thermal limits

Tripping of parallelcircuit (line)

Limit circuit (line)loading

Add series reactor,capacitor

UPFC, TCSC

Adjust series reactance Add seriescapacitor/reactor

UPFC, TCSCParallel line load sharing

Adjust phase angle Add PAR TCPAR, UPFCPost-fault sharing Rearrange network or

use “Thermal limit”actions

PAR, SeriesCapacitor/Reactor

TCSC, UPFC, SVC,TCPAR

Loop flows

Flow direction reversal Adjust phase angle PAR TCPAR, UPFCLimit short circuit current Add series reactor, new

circuit breakerSCCL, UPFC, TCSC

Change circuit breaker Add new circuit breaker

Short circuit levels Excessive breaker faultcurrent

Rearrange network Split busSubsynchronousresonance

Potential turbine/generator shaft damage

Mitigate oscillations series compensation NGH, TCSC

Legend for Exhibit 3NGH = Hingorani Damper TCSC = Thyristor Controlled Series CapacitorPAR = Phase-Angle-Regulator TCVL = Thyristor Controlled Voltage LimiterSCCL = Super-Conducting Current Limiter TSBR = Thyristor Switched Braking ResistorSVC = Static Var Compensator TSSC = Thyristor Switched Series CapacitorSTATCOM = Static Compensator UPFC = Unified Power Flow ControllerTCPAR = Thyristor Controlled Phase-Angle Regulator

Exhibit 3: Steady state applications of FACTS

FACTS are a well-proven technology.The first installations were put into service over20 years ago. As of January 2000, the totalworldwide installed capacity of FACTS devicesis more than 40,000 MVAr in several hundredinstallations. While FACTS devices are usedprimarily in the electricity supply industry, they

are also used in computer hardware and steelmanufacturing (SVC’s for flicker compensation),as well as for voltage control in transmissionsystems for railways and in research centers(e.g. CERN in Geneva).


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Dynamic applications of FACTS

Issue Type of System Corrective Action Conventional Solution FACTS deviceA, B, D Increase synchronizing

torqueHigh-response exciter,series capacitor

TCSC, TSSC, UPFC

A, D Absorb kinetic energy Braking resistor, fastvalving (turbine)

TCBR, SMES, BESS

Transient Stability

B, C, D Dynamic load flowcontrol

HVDC TCPAR, UPFC, TCSC

A Dampen 1 Hzoscillations

Exciter, Power systemstabilizer (PSS),

SVC, TCSC, STATCOMDampening

B, D Dampen low frequencyoscillations

- Power systemstabilizer (PSS)

SVC, TCPAR, UPFC,NGH, TCSC, STATCOM

Dynamic voltagesupport

- SVC, STATCOM,UPFC,

Dynamic flow control - SVC, UPFC, TCPAR

A, B, D

Dynamic voltagesupport and flow control

- SVC, UPFC, TCSC

Post ContingencyVoltage Control

A, B, C, D Reduce impact ofcontingency

parallel lines SVC, TCSC,STATCOM, , UPFC

Reactive Support shunt capacitor, shuntreactor

SVC, STATCOM, UPFC

Network control actions LTC, reclosing, HVDCcontrols

UPFC, TCSC,STATCOM

Generation control High-response exciter -

Voltage Stability B, C, D

Load control Under-voltage loadsheddingDemand-SideManagement Programs

-

Legend for Exhibit 4:A. Remote Generation – Radial Lines (e.g. Namibia) B. Interconnected Areas (e.g. Brazil)C. Tightly meshed network (e.g. Western Europe) D. Loosely meshed network (e.g. Queensland, Austr.)

BESS = Battery Energy Storage System STATCOM = Static Synchronous CompensatorHVDC = High Voltage Direct CurrentLTC = Transformer-Load Tap Changer SVC = Static Var CompensatorNGH = Hingorani Damper TCPAR = Thyristor Controlled Phase-Angle RegulatorPAR = Phase-Angle Regulator TCSC = Thyristor Controlled Series CapacitorSCCL = Super-Conducting Current Limiter TCVL = Thyristor Controlled Voltage LimiterSMES = Super-Conducting Magnetic TSBR = Thyristor Switched Braking Resistor

Energy Storage TSSC = Thyristor Switched Series CapacitorUPFC = Unified Power Flow Controller

Exhibit 4: Dynamic applications of FACTS

Investment costs of FACTS devices.The investment costs of FACTS devices can bebroken down into two categories:(a) the devices’ equipment costs, and (b) thenecessary infrastructure costs.

Equipment costsEquipment costs depend not only upon theinstallation rating but also upon specialrequirements such as:

• redundancy of the control and protectionsystem or even main components such asreactors, capacitors or transformers,

• seismic conditions,• ambient conditions (e.g. temperature,

pollution level): and• communication with the Substation Control

System or the Regional or National ControlCenter.


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Infrastructure CostsInfrastructure costs depend on the substationlocation, where the FACTS device should beinstalled. These costs include e.g.• land acquisition, if there is insufficient space

in the existing substation,• modifications in the existing substation, e.g.

if new HV switchgear is required,• construction of a building for the indoor

equipment (control, protection, thyristorvalves, auxiliaries etc.),

• yard civil works (grading, drainage,foundations etc.), and

• connection of the existing communication

system with the new installation.

Exhibit 5: Typical investment costs for SVC / Statcom

For typical devices’ ratings, the lower limit of thecost areas shown in Exhibits 5 and 6 indicatesthe equipment costs, and the upper limitindicates the total investment costs including theinfrastructure costs. For very low ratings, costscan be higher and for very high power ratingscosts can be lower than indicated. The totalinvestment costs shown, which are exclusive oftaxes and duties, may vary due to the describedfactors by –10% to +30%. Including taxes andduties, which differ significantly betweendifferent countries, the total investment costs forFACTS devices may vary even more.

Exhibit 6: Typical investment cost for SC, TCSC andUPFC

What are the financial benefits ofFACTS devices?There are three areas were the financial benefitscould be calculated relatively easily.1. Additional sales due to increased

transmission capability.2. Additional wheeling charges due to

increased transmission capability.3. Avoiding or delaying of investments in

new high voltage transmission lines or evennew power generation.

Exhibit 7 gives indicates the possible additionalsales in US$ per year based on different energy Exhibit 7: Overview yearly sales

Length of Line in km100 200 300 400 500

M ill. US$

20

40

60

80

100

120

140

160

500 kV

345 kV

220 kV

132 kV

Source: Siemens AG Database

US$/kVAr

Operating Range in MVAr100 200 300 400 500

20

40

60

80

100

120

140

160

SVC

STATCOM


US$/kVAr

O p e r a t in g R a n g e in M V A r100 200 300 400 500

20

40

60

80

100

120

140

160

UPFC

TCSC

FSC



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costs / prices when a transmission line capacitycan be increased.

Exhibit 8 below gives some indication of typicalinvestment costs for new high voltage ACtransmission lines.

Exhibit 8: Typical costs of new AC transmission lines

Example 1:If through using a FACTS device, a fully loadedtransmission line’s capability could be increasedby 50 MW (e.g. for transmission lines of 132 kVor higher), this could generate additional sales of50 MW equivalent. Assuming a 100% load factorand a sales price of 0.02 US$ per kWh, thiswould result in additional annual electricitysales of up to US$ 8.8 million.

Example 2:Assume that the investment costs of a 300 kmlong 400 kV line are approx. US$. 45 million. Atan interest rate of 10%, this results in annualinterest costs of US$ 4,5 million. Installation of aFACTS device for e.g. US$ 20 million could beeconomically justified, if such an investment canbe avoided or delayed by at least 5 years (5times 4,5 = 22.5).

The above examples are only rough calculationsto indicate the possible direct economicalbenefits of FACTS devices.

There are also indirect benefits of utilizingFACTS devices, which are more difficult tocalculate. These include avoidance of industries’outage costs due to interruption of productionprocesses (e.g. paper industry, textile industry,

production of semi-conductors / computer chips)or load shedding during peak load times.

Maintenance of FACTS devicesMaintenance of FACTS devices is minimal andsimilar to that required for shunt capacitors,reactors and transformers. It can be performedby normal substation personnel with no specialprocedures. The amount of maintenance rangesfrom 150 to 250 man-hours per year anddepends upon the size of the installation and thelocal ambient (pollution) conditions.

Operation of FACTS devicesFACTS devices are normally operatedautomatically. They can be located in unmannedsubstations. Changing of set-points or operationmodes can be done locally and remotely (e.g.from a substation control room, a regionalcontrol centre, or a national control centre).

Steps for the Identification of FACTSProjects1. The first step should always be to conduct adetailed network study to investigate the criticalconditions of a grid or grids’ connections . Theseconditions could include: risks of voltageproblems or even voltage collapse, undesiredpower flows, as well as the potential for powerswings or subsynchronous resonances.2. For a stable grid, the optimized utilization ofthe transmission lines – e.g. increasing theenergy transfer capability – could beinvestigated.3. If there is a potential for improving thetransmission system, either through enhancedstability or energy transfer capability, theappropriate FACTS device and its requiredrating can be determined.4. Based on this technical information, aneconomical study can be performed to comparecosts of FACTS devices or conventionalsolutions with the achievable benefits.

Performance VerificationThe design of all FACTS devices should betested in a transient network analyzer (TNA)under all possible operational conditions andfault scenarios. The results of the TNA testsshould be consistent with the results of thenetwork study, which was performed at the startof the project. The results of the TNA study also

50 100 150 200 250 MW

120

80

40

60

100

20

140

160

Additional transmission capacity of a line

Add

ition

al s

ales

in M

ill. U

S$

0,06

0,04

0,02

0,01

US

$ pe

r kW

h



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provide the criteria for the evaluation of the sitecommissioning tests.

The consistency of the results• of the network study in the beginning of the

project,• of the TNA study with the actual parameters

and functions of the installation before goingto site and

• of the commissioning tests on siteensures the required functionality of the FACTSdevices.

Worldwide ApplicationsSeven projects are described below, whereFACTS devices have proven their benefits overseveral years. These descriptions also indicatehow the FACTS devices were designed to meetthe different requirements of the seventransmission systems. The investment costs forthese devices are consistent with the informationpresented in Exhibits 4 and 5 above.The construction period for a FACTS device istypically 12 to 18 months from contract signingthrough commissioning. Installations with a highdegree of complexity,, comprehensive approvalprocedures, and time-consuming equipmenttests may have longer construction periods.

The Australian InterconnectorThe interconnection of the South Australian,Victoria and New South Wales Systems involvedtransmission at voltages up to 500 kV overdistances exceeding 2200 km. Theinterconnection is for interchange of 500 MW.Two identical – 100 MVAr (inductive) /+ 150MVAr (capacitive) SVC’s at Kemps Creekimprove transient stability. Here each SVCconsists of two thyristor-switched capacitors anda thyristor-switched reactor that can be switchedin combination to provide uniform steps acrossthe full control range.

To ensure reliable operation under all powersystem conditions, the implementation of theSVC design had to be carefully evaluated priorto installation. The behavior of the SVC wasexamined at a transient network analyzer undera wide range of system conditions.

The three-state interconnected system and thetwo SVC’s were successfully put intocommercial operation in spring 1990. The twoSVC’s are equipped only with thyristor-switchedreactors and capacitors with the advantage that

no harmonics are generated and therefor nofilters are necessary.The system operates as expected and provedthe original concepts. As part of theinterconnected system, the compensators atKemps Creek have been called upon on severaloccasions to support the system and have doneso in an exemplary manner.

SOUTH AFRICA: Increase in Line Capacitywith SVCThe Kwazulu-Natal system of the Eskom Grid,South Africa, serves two major load centers(Durban and Richards Bay) at the extremities ofthe system. In 1993, the system was loadedclose to its voltage stability limit, a situationaggravated by the lack of base load generationcapacity in the area. The 1000 MW Drakensbergpumped storage scheme, by the nature of itsduty cycle and location remote from the mainload centers, does not provide adequatecapacity.

Exhibit 9: SOUTH AFRICA: SVC, Illovo.

The installation of three SVCs in the major loadcenters provides superior voltage controlperformance compared to an additional new linesubject to load switching.A further motivation for choosing SVCs in thiscase are their lower capital cost, reducedenvironmental impact, and the minimization offault-induced voltage reductions compared tobuilding additional transmission lines. Fault-induced voltage reductions cause majordisruption of industrial processes, and mainlyresult from transmission line faults. Thefrequency of such reductions is proportional tothe total line length exposed to the failuremechanisms (viz. sugar cane fires), resulting in


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a desire to minimize the total length oftransmission lines. These SVCs went intocommercial operation in 1995.

BRAZIL: North – South InterconnectionIn Brazil there are two independent transmissiongrids, the North grid and the South grid. Thesetwo grids cover more than 95% of the electricpower transmission in the country.Detailed studies demonstrated the economicattractiveness of connecting the two grids. Interalia they compared the attractiveness of buildingan AC or a HVDC (High Voltage Direct Current)connection of more than 1.000 km long passingthrough an area with a fast growing economyand also with a high hydropower potential. As itis technically much easier and more economicalto build new connections to an AC line than toan HVDC line it was decided to build a new ACline.

Exhibit 10: BRAZIL: TCSC, Serra de Mesa

The line, which is now in operation sincebeginning of 1999, is equipped with SC’s (SeriesCapacitors) and TCSC’s (Controlled SeriesCapacitors) to reduce the transmission lossesand to stabilize the line.

Initial studies indicated the potential for lowfrequency power oscillations between the twogrids which TCSC’s can dampen and therebymitigate the risk of line instability. In addition, theapplication of TCSCs can effectively reduce therisk of subsynchronous resonances (SSRs)caused by the application of SC’s in a line.SSRs in a transmission system are resonancephenomena between the electrical system andthe mechanical system of turbine – generator

shafts in thermal power stations. Under certainconditions SSRs can damage the shaft of theturbine – generator unit, which results in highrepair costs and lost generation during the unitrepair time.

USA: More Effective Long-Distance HVDC-SystemA major addition to the 500 kV transmissionsystem between Arizona and California, USA,was installed to increase power transfer. Thisaddition includes two new series - compensated500 kV lines and two large SVC’s. These SVC’sare needed to provide system security, safe andsecure power transmission, and support thenearby HVDC station of the Los AngelesDepartment of Water and Power (LADWP). Byinstalling the SVCs, the LADWP ensured itscapability to supply high quality electric power toist major customers and to minimize the risk ofsupply interruptions.

The control design for these SVC’s, based ondetailed analysis, is driven by the unique systemrequirement of dampening the complexoscillation modes between Arizona andCalifornia. Extensive testing on a real-timesimulator was done, including the HVDC systemoriginally delivered by another manufacturerbefore the controls were delivered on site. Fieldtests during and after commissioning verifiedthese results. These SVC’s, ones of the largestinstallations ever delivered, went intocommercial operation early 1996.

INDONESIA: Containerized DesignLoad flow and stability studies of the Indonesianpower system identified the need for a SVC witha control range of – 25 MVAr to + 50 MVAr atJember Substation(Bali). The SVC provides fastvoltage control to allow enhanced power transferunder extreme system contingencies, i. e. lossof a major 150 kV transmission line. Fastimplementation of the SVC was required toensure safe system operation within the shortesttime achievable. To achieve the tight schedule,a unique approach was chosen comprising aSVC design based on containerization to thegreatest extent possible to allow prefabrication,pre-installation and pre-commissioning of theSVC system at the manufacturer’s workshop.This reduced installation and commissioningtime on site and is a step forward fortransportable SVC’s that can be easily and


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economically relocated. The Jember SVC wasput into commercial operation 1995 in only 12months after contract signature.

USA: The Lugo SSR DamperThe SSR (Subsynchronous Resonances)damper scheme is a high voltage-thyristor circuitdesigned to solve a complex problem which in1970 and 1971 caused damage to the shafts ofa turbine-generator connected to the 500 kVtransmission network of the Southern CaliforniaEdison System. Analysis of the cause of thefailure identified the SSR phenomenon. SSRcan occur in electrical networks, which utilizehigh levels of conventional SCs to increasetransmission lines power carrying capability bycompensating the line series inductance. TheSSR problem occurs when the amount of SCcompensation results in an electrical circuitnatural frequency that coincides with, andthereby excites, one of the torsional naturalfrequencies of the turbine-generator shaft.

Dampening is achieved by using anti-parallelthyristor strings to discharge the SCs atcontrolled times. Network configurationsinvolving Southern California Edison’s Mohavegenerator were simulated and used to study theworst case SSR problem. In this case, with ahigh level of SC (70 percent), the effectivenessof the NGH scheme (comprising outdoor valvesat high-voltage potential platforms) wasevaluated. This device is in successfulcommercial operation since the 1980’s.

USA: The Kayenta TCSCIn the Western Area Power Administration(WAPA) system, USA, transmission of low-costand renewable hydroelectric energy was limitedby a major bottleneck in its high-voltagetransmission network. To overcome thislimitation, WAPA installed a TCSC device atKayenta Substation, Arizona – the first everthree-phase thyristor-controlled seriescompensator. The Kayenta installation, insuccessful commercial operation since 1992,provides for a power transfer increase of 33 %while maintaining reliable system operation. TheKayenta ASC has operated successfully underall system conditions, including severaltransmission line faults. This installationprovides the technology demonstrator for thistype of FACTS device, which, in addition tomaking better use of existing line capacity,

obviated the need for installing an extratransmission line by the local electrical utility.

Future Developments in FACTSFuture developments will include thecombination of existing devices, e.g. combininga STATCOM with a TSC (thyristor switchedcapacitor) to extend the operational range. Inaddition, more sophisticated control systems willimprove the operation of FACTS devices.Improvements in semiconductor technology (e.g.higher current carrying capability, higherblocking voltages) could reduce the costs ofFACTS devices and extend their operationranges. Finally, developments in superconductortechnology open the door to new devices likeSCCL (Super Conducting Current Limiter) andSMES (Super Conducting Magnetic EnergyStorage).

There is a vision for a high voltage transmissionsystem around the world – to generate electricalenergy economically and environmentallyfriendly and provide electrical energy where it’sneeded. FACTS are the key to make this visionlive.


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How the World Bank can facilitate increased usage of FACTS devices

Since FACTS devices facilitate economy and efficiency in power transmission systems in anenvironmentally optimal manner, they can make a very attractive addition to the World Bank’s portfolio ofpower projects. In spite of its attractive features, FACTS technology does not seem to be very well knownin the World Bank. The following is a proposed action plan for giving FACTS technology increasedexposure in the World Bank:(a) informing Bank staff and its stakeholders on FACTS technology, including case studies through

publishing relevant papers (such as this one) on its “Home Page” and as part of its EnergyIssues series;

(b) organizing presentations/workshops/training activities in connection with high profile events (suchas Energy Week) on FACTS technology as well as in the field to provide information toBorrowers. This has now occurred for the Greater Mekong Subregion (GMS) Workshop onEnergy Trade in Bangkok February 2000;

(c) conducting a review of its power sector portfolio over the last twenty years to quantify the level ofusage of FACTS devices in Bank projects and identifying lessons learned: and

(d) reviewing its lending pipeline to identify opportunities for increased usage of FACTS technology.

BoxDesign, Implementation, Operation and Training Needs of FACTS DevicesNetwork studies are very important for the implementation of a FACTS device to determine therequirements for the relevant installation. Experienced network planning engineers have to evaluate thesystem including future developments. Right device – right size – right place – right cost.

Reliable operation of FACTS devices require regular maintenance in addition to using equipment of thehighest quality standards. Maintenance requirements are minimal but important.

Optimal use of FACTS devices depend upon well-trained operators. Since most utility operators areunfamiliar with FACTS devices (compared with for example switched reactors or capacitors), training onthe operation of FACTS devices is therefore very important. What is important for the operators to know isare the appropriate settings of FACTS devices, especially the speed of response to changing phaseangle and voltage conditions as well as operating modes. This training would normally last one to twoweeks.

(1) Klaus Habur is Sr. Area Marketing Manager, Reactive Power Compensation, Power Transmission andDistribution Group (EV) of Siemens AG in Erlangen, Germany. Donal O’Leary, Sr. Power Engineer of the WorldBank is on assignment with the Siemens Power Generation Group (KWU) in Erlangen, Germany. This paper hasbeen reviewed by Messrs. Masaki Takahashi, Jean-Pierre Charpentier and Kurt Schenk of the World Bank.

FACTS Introduction

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