Overvoltage protection scheme for series capacitor banks on high voltage distribution systems

An analysis of the overvoltage protection requirements for a series capacitor bank on a high-voltage distribution system (16/27.6 kV) is presented. The problems encountered in providing the required degree of protection are illustrated with an actual case study of an installation implemented by Ontario Hydro. The overvoltage protection scheme, an essential component of the series capacitor bank installation, was reliable and effective in two years of service that saw no capacitor failures. The scheme is based on readily available, off-the-shelf equipment and can be easily adapted to any installation with similar operating requirements. The ring gap, which is the only custom-made component of the system, is simple and could be fabricated by most utilities´ machine shops