This paper analyzes a rain flashover accident of a tank-type circuit breaker

and finds that insufficient height of the bushing structure is the main reason for the rain flashover.For 3/2 network connection mode

if a tank-type circuit breaker is adopted

the relay-protection of the corresponding transmission line or transformer will be activated when flashover occurs on the intermediate bushing

and the protection of the corresponding bus bar and the line（transformer） with circuit breaker will be activated when flashover occurs on the bushing near the bus.Silicone rubber skirts on the bushing of tank-type circuit breaker is suggested to prevent this kind of accident.