The Static Var Compensator for services increases the quality of the energy in many aspects. The benefits of stabilized voltage levels and reactive power compensation improve system stability and increase the power transfer capacity of a transmission line. A static VAR compensator is a parallel combination of controlled reactor and fixed bypass capacitor shown in the figure below. The thyristor switch assembly in the SVC controls the reactor. The firing angle of the thyristor controls the voltage across the inductor and, therefore, the current flowing through the inductor. In this way the consumption of reactive energy by the inductor can be controlled.
The SVC is able to adjust the reactive power less in an unlimited range without delay. Improves the stability of the system and the power factor of the system. The most commonly used SVC schemes are the following.
1. Thyristor controlled reactor (TCR)
2. Switched thyristor capacitor (TSC)
3. Auto reactor (SR)
4. Reactor controlled by thyristors - fixed capacitor (TCR-FC)
5. Switched thyristor capacitor - Thyristor controlled reactor (TSC-TCR)
Advantage of static VAR compensator
• Increased power transmission capacity of transmission lines.
• Improved the transient stability of the system.
• Controls steady state and temporary overvoltages.
• Improved the load power factor and, therefore, reduced line losses and improved system capacity.
The static VAR compensator has no rotating parts and is used for compensation of the overvoltage impedance and compensation by sectioning a long transmission line.