Overvoltages caused by disconnect-switch operation

RECENTLY field tests were performed at the Tanners Creek Station of the Indiana and Michigan Electric Company to investigate overvoltages which were produced when a 1,360-foot section of 345-kv bus was de-energized by an air-break disconnecting switch.¹ The high transient overvoltages not only caused severe duty on connected lightning arresters, but also induced surge voltages in the station low-voltage power and control circuits. In conjunction with the field investigations, analytical studies were initiated in an attempt to determine the causes of the overvoltages and to develop remedial measures which could be used to eliminate the overvoltages.