Experiments And Simulation On The High Current Interruption Principle Of The Series Connected Vacuum Gap And CO₂ Gas Gap

With the increasing power system capacity in our country and the rising voice on limiting the usage of SF6 gas around the world,it has been increasingly imperative to develop the environmental-friendly high voltage circuit breakers with higher interruption capacity.The circuit breakers widely applied in power system,which refer to vacuum circuit breaker and SF6 gas circuit breaker,show their interruption advantages and disadvantages.Most researches on environmental-friendly high voltage circuit breakers are launched based on the interruption principle of above mentioned two circuit breakers.Hybrid circuit breaker is composed of series connected vacuum gap and SF6 gas gap.It can utilize the interruption advantages of both vacuum gap and SF6 gas gap to obtain favorable interruption capacity gains.And hybrid circuit breaker shows high developing potential,as it can avoid the interruption disadvantages of the two series connected gaps.Based on the studies on substitutes for SF6 gas and the traditional hybrid circuit breakers which adopt SF6 gas,this paper proposes a novel hybrid circuit breaker,which is series connected by vacuum gap and CO2 gas gap.The hybrid circuit breaker can decrease the influence of greenhouse effect from high voltage circuit breaker with different gas interruption dielectric,meanwhile promising the interruption capacity of the circuit breaker.This paper reviews the development and research status of both vacuum circuit breakers,substitutes for SF6 gas,and hybrid circuit breakers at first.Combined with the summarized interruption principles of different circuit breakers,the problems to be solved in the project and the mainly research works in this paper are illustrated.The black-box arc models of the hybrid circuit breaker based on CO2 gas are built in the simulation platform EMTP-ATP.The interaction characteristics of vacuum gap and CO2 gas gap during the interruption process and the interruption principle of hybrid circuit breakers are simulated and studied.And favorable cooperating interruption strategies for the hybrid circuit breaker are obtained.Then,the test prototype of the hybrid circuit breaker based on CO2 gas is established,and themechanical characteristics of hybrid circuit breaker's actuators are tested.The experimental principle of synthetic test circuit and the experimental schemes for hybrid circuit breakers are outlined later.Based on previous preparations,the current interruption capacity of the hybrid circuit breaker based on CO2 gas is tested.With the comparison of the interruption capacity with the hybrid circuit breaker based on SF6 gas,the dynamic breaking process of the hybrid circuit breaker based on CO2 gas is studied;and the influent factors on the interruption capacity of the hybrid circuit breakers are analyzed.Combining with the analysis of experiment results,the internal structure of rotating arc gas interrupter is regard as the mainly hindrance on the dielectric strength recovery speed of CO2 gas,which has influenced the interruption capacity of hybrid circuit breaker.Then,the test prototype of puffer type CO2 gas gap is designed and established.And the circuits to test dielectric strength recovery of CO2 gas are also established.The static and dynamic dielectric strength recovery characteristics of puffer type CO2 gas gap are tested to verify the feasibility of puffer type gas interrupter for enhancing the dielectric strength recovery speed of CO2 gas.The simulation and experiment results in this paper prove that,under proper interruption control strategy,the hybrid circuit breaker can utilize vacuum gap to assist gas gap at the initial transient period after current-zero.But the dielectric strength recovery speed of CO2 gas in rotating-arc gas interrupter is too slow to cooperate with vacuum gap.As the followed test results reveals,the dielectric strength recovery speed of CO2 gas in puffer type gas interrupter can be significantly improved.Based on the experiment results,it is suggested to optimize the structure of the nozzle system and heating volume in gas interrupter combining with the arc characteristics of CO2 gas,providing a basis for the development of hybrid circuit breaker based on CO2 gas.