According to the requirement for field measurement of circuit breakers

a testing method of opening and closing time under two-terminal grounding condition is proposed. The testing requirements for opening and closing time of a circuit breaker under two-terminal grounding condition are analyzed

the measurement method and technical solutions of switching signal criterion are obtained

and the testing method and field test scheme of circuit breaker and GIS under two-terminal grounding condition are provided. Comparison with the conventional testing method indicates that the proposed testing method of opening and closing time of circuit breaker with twoterminal grounding completely meets the requirement for field maintenance.