Measurement of Post-Arc Current of Mechanical DC Vacuum Circuit Breaker: A Methodological Study

We addressed the measurement of post-arc current of mechanical DC vacuum circuit breaker with the proposed circuit,consisting of a fast making switch,a high-precision current clamp,a ball-gap discharge manometer,metal-oxide-varister(MOV) ZnO surge-arrestor and a transfer-resistor.The novel method was based on the current transfer mechanism.The vacuum arc discharge was mathematically formulated with modified Mayr model and numerically simulated with MATLAB.The influence of the switching current(I_m),transfer resistor(R_sh) and arcing-time on the peak-current(I_shm),passing only the transfer-resistor immediately after the transference,and its lasting time(Δt) was investigated.The simulated results show that the switching current and transfer-resistance have a major impact.For example,as I_m increases,I_shm decreases with an increase of R_sh,depending little on the arcing time; however,at a fixed R_sh,as I_m increases,I_shm almost remains unchanged.