The technology of controllable surge arrester can be used to limit switching overvoltage deeply in power system

and the key to the practicality of this technology is the simplicity and reliability of its control elements. In this paper

a new trigger gap is proposed as a control element. The gap does not need external trigger signal and energy

only uses the operating current of the arrester to realize trigger conduction. The close operation of unloaded UHV AC line is taken as typical application

and the control ratio is set at 10%. Firstly

the gap parameters are determined

the gap model is established

and the voltage limiting effect and trigger characteristics of the gap are studied through simulation analysis. Then

the gap structure is proposed

the principle prototype is designed

and the gap trigger function and correctness of the model are verified through prototype test. Finally

the feasibility of gap scheme is determined based on the simulation and test results. The results show that the trigger gap proposed in this paper can trigger reliably at 0.87 times of the rated voltage. The typical trigger delay is 33～333 μs

and is shorter with steeper wavefront of overvoltage. The gap characteristics meet the application requirements

and it is technically feasible to construct controllable surge arrester with this trigger gap.