Circuit breaker models for simulations of short-circuit current breaking and slow-front overvoltages in HV systems

Various circuit breaker models have been developed as a tool to evaluate the breaker interrupting capability and to investigate interaction between the breaker and the external circuit. This paper presents selected models of high voltage SF6 circuit breakers (Cassie-Mayr, Schwarz-Avdonin, and an ideal switch with a predefined chopping current level), followed by analysis of the models impact on the 400 kV overhead line fault clearing process. Several study cases have been performed to demonstrate the impact of the circuit breaker model on the arcing time and on the transient recovery voltage (TRV) during breaking of the near-to-generator faults. The results obtained indicate that the arc voltage introduced by the circuit breaker model can force the fault current zero crossing and in consequence can significantly change the breaking conditions. It particular, in the study cases where the arc voltage has significant impact on the breaking conditions (such as the near-to-generator fault), the models applied accurately represent arc voltage during the entire current interruption process.