Capacitive current breaking capability estimation for a 145 kV 40 kA GIS circuit breaker

In this paper, the impact of several 145 kV 40 kA GIS (Gas Insulated Switchgear) circuit breaker design parameters, such as length of the main nozzle throat, contact travel and average opening speed, on the estimated breakdown voltage of the contact gap of an interrupter during capacitive current breaking is analyzed. A new approach for breakdown voltage estimation, which provides full correlation between all circuit breaker design parameters and dielectric characteristics of the contact gap and the criterion for breakdown occurrence, was used for this purpose. The estimated capacitive current breaking capability of the circuit breaker was verified by type testing in KEMA High Power Laboratory, the Netherlands.