Introduction to Static Var Compensator.pdf

Figure 23 circuit diagram of the three legs phases of

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Figure 23. Circuit diagram of the three legs (phases) of a fixed capacitor (FC) in an SVC. An SVC usually comprises more than one FC. The FCs serve the purpose of supplying a fixed amount of reactive power to the system to which the SVC is connected. Notice that each capacitor in the FC shown in the figure above is connected in series with a small inductor used to filter the prevalent harmonic components produced by the TCR. In other words, adding a tuning inductor in series with each capacitor of an FC makes the FC operate as a harmonic filter. By properly tuning the inductors used in an FC, it is possible to specifically eliminate a particular harmonic component. For example, the inductors in an FC of an SVC could be tuned to filter the 5 th harmonic while the inductors in Voltage (V) Current (A) Voltage across the capacitor The capacitor is switched out at this instant (thyristor value turns off) Holding current The thyristor firing signals are removed at this instant Current flowing in the capacitor Tuning inductors (small) Fixed capacitors ܺ ௅ଵ,ி஼ ܺ ௅ଶ,ி஼ ܺ ௅ଷ,ி஼ ܺ ஼ଵ,ி஼ ܺ ஼ଶ,ி஼ ܺ ஼ଷ,ி஼ Line voltage applied to one leg of TSC To phase A of the SVC step-down transformer To phase C of the SVC step-down transformer To phase B of the SVC step-down transformer
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Main Components of a Static Var Compensator (SVC) Discussion Static Var Compensator (SVC) 23 another FC of the SVC could be tuned to filter the 7 th harmonic. The principles behind the tuning of the inductors used in the FCs in order to filter harmonic components are beyond the scope of this manual. Figure 24. SVC installation used for power factor correction at an electrified railway (© Nissin Electric WuXi Co.,LTD, all rights reserved).
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Main Components of a Static Var Compensator (SVC) Discussion 24 Static Var Compensator (SVC) Layout of an SVC substation Figure 25 shows the typical layout of an SVC substation used for voltage compensation of ac transmission lines. The components corresponding to the numbered boxes in the figure are identified below. 1. Three-phase, step-down transformer 2. Three-phase, step-down transformer cooling unit 3. Thyristor-controlled reactor (TCR) 4. Thyristor-switched capacitor (TSC) 5. Protective inductors of the TSC 6. Filtering capacitors 7. Filtering inductors 8. Filtering circuit breaker 9. Thyristor valves and control building 10. Thyristor valve cooling units Figure 25. Aerial view of an SVC substation in Strathmore, Australia. The components corresponding to the numbered boxes in the figure are identified above (© Siemens AG 2012, all rights reserved). 3 9 2 4 5 7 6 10 8 1
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