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  • 8/2/2019 FACTS for Cost Effective and Reliable Transmission of Electrical Energy





    FACTS Flexible Alternating Current Transmission Systems

    For Cost Effective and Reliable Transmission of Electrical Energy


    lexible alternating current transmissionsystems (FACTS) devices are used for theynamic control of voltage, impedance and phase angle of high voltage AC lines. FACTSevices provide strategic benefits for improved transmission system managementhrough: better utilization of existing transmission assets; increased transmissionystem reliability and availability; increased dynamic and transient grid stability;ncreased quality of supply for sensitive industries (e.g. computer chip manufacture);nd enabling environmental benefits.Typically the construction period for a factsevice is 12 to 18 months from contract signing through commissioning.

    n order to increase the reliability of the nations power grid, this paper proposes using an Evolutionary Algorithm (EA)o optimize the placement of a limited number of Flexible AC Transmission System (FACTS) devices on power lines.We benchmark against a brute-force placement and compare our EA approach with a greedy algorithm approachuggested by previous research to show that the EA approach results in superior placements.

    This paper starts by providing definitions of the most common application of FACTS devices as well as enumeratesheir benefits (focussingon steady state and dynamic applications). Generic information on the costs andbenefits ofACTS devices is then provided as well as the steps for identification ofFACTS projects. The paper then discusses twopplications of FACTS devices in Brazil and Indonesia.

    ntroductionOur nation is becoming ever more dependent on its electrical power grid, while at the same time the power grid is becomingncreasingly vulnerable to both natural and intentional disruption . Increasing the reliability of our power grid is therefore ofaramount importance.

    The need for more efficient electricity systems management has given rise to innovative

    echnologies in power generation and transmission. The combined cycle power stations a good example of a new development in power generation and flexible AC transmissionystems, FACTS as they are generally known,are new devices that improve transmissionystems.

    Worldwide transmission systems are undergoing continuous changes and restructuring. They are becoming more heavily loadednd are be in operated in ways not originally envisioned. Transmission systems must be flexible to react to more diverseeneration and load patterns diverse generation and load patterns. In addition, the economical utilization of transmission systemsset is of vital importance to enable utilities in industrialized countries to remain competitive and to survive.In developingountries, the optimized use of transmission systems investments is also important to support industry, create employment andtilize efficiently scarce economic resources.

  • 8/2/2019 FACTS for Cost Effective and Reliable Transmission of Electrical Energy





    Flexible AC Transmission Systems (FACTS) is a technology that responds to these needs. Itignificantly alters the way transmission systems are developed and controlled together with improvements in asset utilization,ystem flexibility and system performance

    What are FACTS devices?

    ACTS devices are used for the dynamic control of voltage, impedance and phase angle of higholtage AC transmission lines. Below the different main types of FACTS devices are described:

    Static Var Compensators (SVCs):-

    he most important FACTS devices, have been used for a number of years to improve transmission economics by resolvingynamic voltage problems. The accuracy, availability and fast response enable SVCs to provide high performance steady statend transient voltage Control compared with classical shunt compensation. SVCs are also used to dampen power swings,mprove transient stability, and reduce system losses by optimized reactive power control.

    Thyristor controlled series compensators (TCSCs):-

  • 8/2/2019 FACTS for Cost Effective and Reliable Transmission of Electrical Energy





    hese are an extension of conventional seriescapacitors through adding a thyristor-controlled reactor. Placing a controlledeactor in parallel with a series capacitor enables a continuous andapidly variable series compensation system.The main benefits of TCSCs are increased energy transfer, dampening of powerscillations, dampening of subsynchronous resonances, and control of line power flow.

    STATCOMs :-

    hese are GTO (gate turn-off type thyristor) based SVCs. Compared with conventional SVCs (see above) they dont requirearge inductive and capacitive components to provide inductive or capacitive reactive power to high voltage transmissionystems. This results in smaller landequirements. An additional advantage is the higher reactive output at low system voltages where a STATCOM can beonsidered as a current source independent from the system voltage. STATCOMs have been in operation of approximately 5ears.

    Unified Power Flow Controller (UPFC):-

    Connecting a STATCOM, which is a shunt connected device, with a series branch in the transmission line via its DC circuit

    esults in a UPFC. This device is comparable to a phasehifting transformer but can apply a series voltage of the required phase angle instead of aoltage with a fixed phase angle. The UPFC combines the benefits of a STATCOM and a TCSC.

  • 8/2/2019 FACTS for Cost Effective and Reliable Transmission of Electrical Energy





    Benefits of utilizing FACTS devices:-

    he benefits of utilizing FACTS devices in electrical transmission systems can beummarized 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 sensitive industries

    Environmental benefits

    Better utilization of existing transmissionsystem assets :-

    n many countries, increasing the energy transfer capacity and controlling the load flow ofansmission lines are of vital importance, especially in de-regulated markets, where the

    ocations of generation and the bulk load centers can change rapidly. Frequently, adding newansmission lines to meet increasing electricity demand is limited by economical andnvironmental constraints. FACTS devices help to meet these requirements with the existingansmission systems.

    ncreased transmission system reliability and availability :-

    ransmission system reliability and availability is affected by many different factors. AlthoughACTS devices cannot prevent faults, they can mitigate the effects of faults and make electricityupply more secure by reducing the number of line trips. For example, a major load rejectionesults in an over voltage of the line which can lead to a line trip. SVCs or STATCOMsounteract the over voltage and avoid line tripping.

    ncreased dynamic and transient grid stability :-

    ong transmission lines, interconnected grids, impacts of changing loads and line faults canreate instabilities in transmission systems. These can lead to reduced line power flow, loopows or even to line trips. FACTS devices stabilize transmission systems with resultingACTS For cost effective and reliable transmission of electrical energy higher energy transfer capability and reduced risk ofne trips.

    ncreased quality of supply for sensitive industries :-

    Modern industries depend upon high quality electricity supply including constant voltage, andequency and no supply interruptions. Voltage dips, frequency variations or the loss of supplyan lead to interruptions in manufacturing processes with high resulting economic losses.ACTS devices can help provide the required quality of supply.

    nvironmental benefits :-

    ACTS devices are environmentally friendly. They contain no hazardous materials and produce no waste or pollutanse. FACTSelp distribute the electrical energy more economically through better utilization of existing installations thereby reducing theeed for additional transmission lines.

  • 8/2/2019 FACTS for Cost Effective and Reliable Transmission of Electrical Energy





    Applications and technical benefits of FACTS devices:-

  • 8/2/2019 FACTS for Cost Effective and Reliable Transmission of Electrical Energy





    xhibits 2 to 4 below describe the technical benefits of the principal FACTS devices including steady state applications inddressing problems of voltage limits, thermal limits, loop flows, sh


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