Insulation Coordination for 38 kV Circuit Breakers

Based on a review of the impulse insulation requirements for 38 kV circuit breakers and the impact of insulation coordination using modern arresters, a change is suggested in the way the impulse requirements are stated for the circuit breaker. The facets of circuit breaker design which may be affected are indicated. Specifically it is suggested that in the present state of the art, circuit breakers for general application at 34.5 kV should have a standard requirement for 150 kV BIL phase to ground, and 200 kV BIL phase to phase and across the open break.