Research On Vacuum Arc Current Zero Zone Parameters Of DC Vacuum Circuit Breaker

With the development of DC transmission and DC microgrid,the control and protection of DC grid have received increasing attention.The lack of DC circuit breaker(DCCB)restricts the development of DC grids,and DC vacuum circuit breaker is one of the effective solutions.The key to current breaking of DC vacuum circuit breaker based on commutation principle is current zero zone.Post-arc current and chopping current are important parameters of current zero zone for breaker opening.Post-arc current determines whether the arc can re-ignite,while the chopping current will generate overvoltage in the system,which in turn will cause arc re-ignition.Research on current zero zone has become one of the scientific problems that DC vacuum circuit breakers need to solve.This paper is related to the "Research on the theory of high-voltage DC short-circuit breaking based on intelligent module technology" of the National Natural Science Foundation of China," Research on Vacuum Arc Current Zero Zone Parameters of DC Vacuum Circuit Breaker",using continuous transition mode(CTM)based on Matlab for the precise simulation of post-arc current of DC vacuum circuit breaker based on commutation principle,obtaining the post-arc current development curve,considering the effect of the post-arc current on transient recovery voltage(TRV).The results show that when considering the post-arc current,the transient recovery voltage changes slightly at the beginning.Using the resistance-transfer method to measure DC post-arc current,statistical analysis is implemented on the data that changing the arcing time and current drop rate.The results show that the post-arc current is related to the arcing time and the current drop rate of current zero zone.Arcing time between 0.5ms and 4ms,when the arcing time is longer,the post-arc current is larger,when the current drop rate of current zero zone is larger,the post-arc current is larger.In the case of small current breaking,the influence of current chop on DC breaking is simulated and analyzed.The results show that current chop resulted in a positive overvoltage between the fractures.After the oscillation decreased transient recovery voltage begins to develop.The experimental measurement of current chop is carried out under the circumstance of DC small current in vacuum.Besides,breaking current,arcing time,commutation frequency,and the capacitance of the snubber branch is changed several times to acquire experimental data and perform statistical analysis.The results show that when breaking current is 100-300 A,chop value decreases with the increase of breaking current;when arcing time is 0.5-4ms,chop value decreases with the increase of arcing time;when commutation frequency is 700-4000 Hz,chop off value increases as frequency increases;when snubber branch capacitance is 0-0.1?F,chop value increases as snubber capacitance increases.By measuring the current chop phenomenon in DC breaking process based on commutation principle,it provides a reference for further analysis of current zero zone and current chop of middle-frequency arc extinguish.