Circuit breaker overvoltages at transmission line protection adjustment

The transmission line protection adjustment includes the single-phase openings of circuit breaker at small capacitive current. The single-phase opening can be responsible for an extra increase in the magnitude of the transient recovery voltage comparing to the three-phase opening. Using computer simulations, the over-voltages between circuit breaker contacts were calculated as basic data for the highest electric field during their opening. The measurements on a new 232-km long 400 kV transmission line were in good agreement with the obtained results