Planning and implementation of large synchronously switched shunt capacitor banks in the Entergy system

The Western Part of the Entergy system is one of the fastest growing in the system with a high concentration of industrial loads. The power into the area is imported primarily over Richard-Webre and Mt. Olive-Hartburg 500 kV lines. The loss of the Richard-Webre line coupled with an outage of the largest generator in the area (Nelson 6 unit) leads to a reactive power deficiency in the area resulting in a voltage collapse. Amongst the various solutions for the voltage collapse problem, the installation of large shunt capacitor banks was deemed to be one of the most cost-effective option and one that had the least implementation time. Therefore, 140 MVAr capacitor banks were recommended for the Nelson 230 kV and Carlyss 138 kV substations. These capacitor banks were the largest ever installed on the Entergy system. Due to the extremely sensitive nature of loads in the area and potential voltage magnification problems, it was decided to use synchronous closing breakers to switch these capacitor banks. Transient studies were performed to determine the impact of overvoltages introduced during switching of the capacitor banks. This paper focuses on factors that influenced bank sizing and location, results of the switching studies, choice of switching device, installation and operating experience.