In this paper

a light-triggered ball gap switch is proposed for the test circuit of UHV circuit breaker. The technical scheme and principle of the switch are discussed. Meanwhile

several key factors

which affect the performance of the ball gap switch

are analyzed. By means of the finite element method

the electric field across the ball gap of the switch is calculated and estimated

so as to determine the minimum breakdown voltage distance in cases of the self discharge and the trigger discharge with different gap. The basis of gap selection and the trigger voltage selection are provided for the ball gap switch with different rated voltage. Finally

a prototype of the ball gap switch is developed

the self discharge and trigger discharge tests are carried out. The results show the theoretical analysis offered in the paper are accurate to some extent

and the design idea of the ball gap switch is feasible.