STATIC VAR COMPENSATOR (SVC) AND APPLICATIONS
1. Short notes on voltage control by SVC?
The transmission line voltage is maintained by connecting static var compensator (SVC) in the receiving end side. The comparator will measure the actual and reference values of transmission line voltage; depends on the comparator output the reactive power is injected Into the transmission line, and the transmission line voltage will be controlled.
2. Write down the equation for SVC bus voltage.
VS = VSVC + ISVC XS
3. Give the advantages of the slope in the SVC dynamic characteristics.
The reactive power rating is reduced
SVC is prevented from reaching its reactive power limit too frequently
It provides effective parallel operation of two parallel connected SVC’s
4. What is SVC slope in the dynamic characteristics?
To improve the power system operating performance 2.5% voltage de-regulation will be provided in SVC operation. So this voltage de-regulation results in 5% slope in the SVC dynamic characteristics.
5. How the SVC prevents the reactive power rating, reaching its limit too frequently?
Due to slope in the SVC dynamic characteristics the no load to change in load Variation limit will be increased, so the SVC is prevented from reaching its reactive power limit too frequently. Thus the total reactive power needed is reduced to certain limit.
6. Explain the load sharing of two parallel connected SVC’s.
Without slope in the SVC dynamic characteristics there is a discontinuous gap between capacitive and inductive region. This gap will be reduced by operating two parallel connected SVC’s with slope (2.5% voltage de-regulation) in the SVC dynamic characteristics.
7. What are the conditions involved for influence of the SVC on system voltage?
Coupling transformer ignored, with coupling transformer, System gain
8. What is ESCR?
Effective short circuit ratio (ESCR) =1 / XS
= 1 / (-Δsvc / ΔIsvc)
= BS(equivalent system susceptance)
9. What is system gain? What is per unit system gain?
System gain KN = Vs / ESCR
= Vs / BS
Per unit System gain KN = ΔVsvc / Bsvc
= Qsvc / Sc p.u
10. What is short circuit power?
Short circuit power Sc = ( base voltage)×(short circuit current) = (Vb ) × ( BS. Vs)
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