Influence of grading capacitors on the breaking capacity of two vacuum interrupters in series

Series coupling of two vacuum interrupters (VIs) is used in special applications to double the current breaking capability. Grading capacitors are usually added to guarantee essentially equal voltage distribution in each interrupter and to lower the rate of rise of the transient recovery voltage. Other solutions are designed without the use of grading capacitors due to aspects such as lack of space and the need to reduce cost. The aim of this paper is to show the influence of grading capacitors on the breaking capacity. A comparison of the performance with a nonequal voltage distribution is presented, considering the case of self grading arrangements without any additional grading means. The focus is on the transient behavior of both cases when re-ignitions occur in the vacuum interrupters.