Simulation And Experimental Study On Static Characteristics Of Hybrid Circuit Breaker With Vacuum Gap And CO₂ Gas Gap In Series

With the increasingly emphasis on environment protection,decreasing and limiting the usage of greenhouse gases becomes a consensus.SF6 gas shows excellent electrical properties,but it is also with serious greenhouse effect.And the study on environmental friendly circuit breaker has become a hot issue in the field these years.Among the substitutes for SF6 gas,CO₂ gas attracts widely concern for its stable properties and relative preferable arc interruption capacity.By series connecting vacuum gap and CO₂ gas gap composing hybrid circuit breaker,and utilizing vacuum gap to compensate the relative worse arc interruption capacity of CO₂ gas gap;the interruption capacity of CO₂ gas gap can be enhanced,so as the interruption capacity of the hybrid circuit breaker based on CO₂ gas can match with SF6 gas circuit breaker,providing important research significance and research value for the study on environmental friendly circuit breaker.This paper mainly investigates the electric field distribution of hybrid circuit breaker,the air flow field characteristic of CO₂ gas,and the insulation and static dielectric strength recovery characteristics of CO₂ gas,and the research results may provide experiences and references for the study of environmental friendly circuit breaker.And the mainly work and results are showed as follows:A hybrid circuit breaker model based on vacuum gap and CO₂ gas gap had built to solve the installation mode problem,and then an electric field simulation about this model was operated to test it.The sub model was used to interpolate the electric potential of the air-shed,and then the analysis of simulation was carried out to improve the calculation accuracy and find a new way about the simulation in this area.The results show that the 45 degree angle and the gas gap are installed at the top are the most suitable arrangement for the partial pressure characteristics of the hybrid circuit breaker.In addition,the shunt capacitance in the vacuum gap can adjust the ratio of the two gaps,in order to prevent the breakdown of some gap caused by excessive voltage.Simulation about different structure of CO₂ gas spout was taken to solve the problem that the arcing time of CO₂ gas is too long.It is found that extend the throat length properly can increase the gas flow rate in a long time when the breaker is breaking.Through the simulation of the air-shed with different cylinder radius,it is found that the increasing of the cylinder radius can increase the gas velocity at the nozzle,and the larger the cylinder radius will lead to the larger maximum value of the three observation points.Increasing the cylinder radius can effectively increase the velocity of the gas,so if CO₂ gas was chosen as the arc extinguishing medium,it's better to increase the cylinder radius.According to the insulation and back arc dielectric recovery characteristics of CO₂ gas,the experiments of different CO₂ gas pressure and different gap distances of CO₂ under power frequency withstand voltage and lightning impulse withstand voltage are carried out.The experimental results show that when the CO₂ gas at the pressure of 0.2MPa,the gap distance is 2mm,the breakdown voltage is 14.2k V,the polarity of the lightning impulse breakdown voltage is about 35 k V.When the gas pressure is increased to 1.0MPa,the gap distance is increased to 6mm,the AC breakdown voltage is increased to 69 kV,and the polarity of the lightning impulse breakdown voltage is increased to about 125 k V.The recovery strength test circuit of natural medium of CO₂ was set up,and tested the recovery strength of CO₂ gas.The experimental results show that the natural recovery strength of CO₂ gas is poor,there is almost no recovery in 1ms after the current is zero.When the gas pressure is 0.6MPa and the gas distance is 4mm,the recovery strength of the CO₂ is only 22 k V after the arcing in 10 ms,so the method that only increasing the pressure of CO₂ gas to increase the dielectric recovery rate of the CO₂ gas has limited effect.Compared with SF6 gas,the recovery rate of CO₂ gas is too slow.If we want to use CO₂ gas as the arc extinguishing medium,we can increase the recovery rate of the medium by adding the gas-blast equipment.