EHV Shunt Capacitor Bank Design and Transient Analysis - A Case Study

Shunt capacitor banks are important for the voltage stability of transmission and distribution networks. In addition, they increase the efficiency of real power transfer. These benefits are amplified in an extra-high-voltage (EHV) system built from longer transmission lines, with expectations for higher reliability. Therefore, a reliable and practical design of EHV shunt capacitor banks is significantly needed. American Electric Power Company (AEP) developed a high-margin, EHV shunt capacitor bank design and protection scheme to reduce the number of failures and ensure proper protection of equipment. In addition, shunt capacitor bank switching may cause transients that can result in damage and misoperations of the capacitor and nearby equipment. This paper describes the design of the EHV (i.e., 345 kV) shunt capacitor bank equipment, protection scheme and transient response and mitigation - with the goal of improving the capacitor's availability and the system's reliability. The findings from this case study may be useful for other similar projects in the industry.