Failure Analysis of Components Due to 480-V Ground Faults

While many preferred methods exist for protecting components against damage from ground fault currents on 480-V systems, few analyses (if any) have been made concerning the effects on components (molded-case breaker, overload relay, etc.) due to a failure or absence of a ground fault protective device to clear a ground fault. Unlike fuses, which by definition could be considered self-protecting, no such feature exists in relays, molded-case breakers, or overload relay heater elements. The need for sensitive ground fault protection is clarified as by using known I2t techniques to examine the circuit components.