Proposed Transient Recovery Voltage Ratings for Power Circuit Breakers

Representative unmodified transient recovery voltages (TRVs) of power systems have been selected to derive the recovery voltage ratings for power circuit breakers. Mathematical expressions have been derived that combine fundamental system parameters such as load current, line impedancee, voltage regulation, and transformer reactance, together with the rated voltage and circuit interrupting capabilities of the breaker, to describe the TRV withstand requirements for power circuit breakers. Two points in a volt-time plane are developed to describe the TRV withstand requirements of power breakers, and numerical values are listed for these proposed rating values. The TRV ratings for fault currents less than rated currents and for kilometric short line faults are also developed. Since the expressions developed describe system recovery voltages, they may also be used to calculate the TRV of actual power systems.