SVC protection and control basics (for Entergy's porter SVC with external capacitor bank switching)

The static VAr compensator provides reactive power and voltage support to the transmission system by switching local SVC capacitors and by switching remote capacitor banks. The fast capacitor switching in the SVC is accomplished by using light triggered thyristors, and remote capacitor switching will be handled by the SVC controls, transmission operation centers, remote terminal units (RTUs), and existing capacitor banks at remote substations. This paper will focus on the control based over/under-voltage and thermal overload protection for the thyristors and also on the logic and the techniques used to switch the remote capacitors. The relay-based protection included in the SVC installation will also be discussed briefly in this paper.