A STATISTICAL VACUUM CIRCUIT-BREAKER MODEL FOR SIMULATION OF TRANSIENT OVERVOLTAGES

A statistical model of a medium voltage vacuum circuit breaker was developed in EMTP by using new powerful TACS MODELS. The model includes the are voltage characteristic, calculation of mean chopping current value with known di/dt, the dielectric breakdown voltage characteristic, contacts separation dynamics, probability of high frequency are quenching capability and probability of high frequency (HF) zero current passings. The influence of a switching-off time is studied and a statistical estimation is given of the transient overvoltages expected for a specific network configuration. The relation between the switching-off times and the overvoltages is also presented. In addition to these results the paper includes explanation of the modeling technique in the EMTP for all elements constituting the distribution network and validation of the vacuum breaker model behavior. This approach provides valuable information to engineers constructing metal-enclosed switchgear, electric utilities and other users who are going to install vacuum breakers in medium voltage networks.