Shunt Capacitor Bank Fundamentals and Protection

Shunt capacitor banks are used to improve the quality of the electrical supply and the efficient operation of the power system. Studies show that a flat voltage profile on the system can significantly reduce line losses. Shunt capacitor banks are relatively inexpensive and can be easily installed anywhere on the network. This paper reviews principles of shunt capacitor bank design for substation installation and basic protection techniques. The protection of shunt capacitor bank includes: a) protection against internal bank faults and faults that occur inside the capacitor unit; and, b) protection of the bank against system disturbances. Section 2 of the paper describes the capacitor unit and how they are connected for different bank configurations. Section 3 discusses bank designs and grounding connections. Bank protection schemes that initiate a shutdown of the bank in case of faults within the bank that may lead to catastrophic failures are presented in Section 4. The paper does not address the means (fuses) and strategies to protect individual elements or capacitor units, nor the protection of capacitor filter banks. System disturbances and basic capacitor bank control strategies are also discussed.