Evaluation of Switching Surge Overvoltages on Medium Voltage Power Systems

The increasing application of vacuum circuit-breakers on utility and industrial systems has prompted a renewed and detailed investigation of vacuum switching surge mechanisms. The present paper discusses the mechanisms of switching surge phenomena, and describes how a test-validated computer program is used to establish a thorough understanding of breaker/system interaction. The program uses data on the circuit-breakers derived from several thousand measurements to determine the effects of cable length, surge protection, and MVA rating on switching overvoltage cumulative appearance probabilities of motor and transformer loads.