Research on transient insulation numerical analysis method of circuit breaker in GIS under lightning impulse voltage

In order to reveal the process of insulation destruction of circuit breaker in GIS under lightning impulse voltage, a new method of transient insulation numerical analysis is described in this paper. A combination of the electromagnetic transient analysis method and optimised charge simulation method (CSM) was put forward to calculate and analyse the transient insulation characteristics of 550 kV circuit breaker in GIS under lightning impulse voltage. The results show that, within 0–15 μ, though the voltage of circuit breaker did not reach its peak, there is severe electric field distortion caused by sharp change of voltage with a high probability of circuit breaker insulation breakdown. In addition, as for the circuit breaker insulation structure optimisation design, it is advisable to restrain the change rate of electric field strength amplitude so as to reduce the probability of insulation breakdown, rather than simply verify insulation structure by using maxi‐mum electric field strength as the voltage input parameters of the electrostatic field under the power frequency in accordance with the traditional insulation analysis method, with the purpose of ensuring the circuit breaker can operate safely and reliably for a long time.