气体介质对多间隙气体开关电晕均压与自击穿特性的影响

Effect of gas medium on corona discharge for voltage balance and self-breakdown characteristics in multi-gaps gas switch

快脉冲直线变压器型驱动源(FLTD)是近年来快速发展的新型脉冲功率源技术,多采用多间隙气体开关作为开关器件。电晕均压措施有利于提升开关击穿性能,但不同气体中电晕放电有显著区别。本文首先研究了空气中针电极对单间隙电晕放电特性的影响,确定了电晕针电极的尺寸,之后研究了N2,CO2,SF6/N2混合气体、C4F7N/N2混合气体中的电晕放电特性,研究了电晕均压6间隙气体开关击穿电压及其稳定性随气体种类和气压的变化规律。实验结果表明,N2中电晕电流较大且不稳定,空气中电晕电流比N2中低,且电晕放电较为稳定,微量强电负性气体加入会极大降低电晕放电电流。当采用空气和N2作绝缘介质时,气体开关击穿电压随气压升高线性增加,但存在低值击穿,微量强电负性气体混合N2可显著提升击穿电压的稳定性。1%SF6/99%N2混合气体在0.18 MPa时,击穿电压约为197.33 kV,标准偏差占击穿电压比例为1.50%,1%C4F7N/99%N2混合气体在0.15 MPa时,击穿电压约为190.42 kV,标准偏差为0.55%。这表明,微量环保替代气体C4F7N与N2的混合气体对于提升多间隙气体开关击穿电压稳定性有显著作用。

The fast linear transformer drive(FLTD)is a new type of pulse power source developing rapidly in recent years.It usually adopts multi-gap gas switch(MGS)as its primary switch.The corona discharge for voltage balance was proposed to improve the switch breakdown performance.However,great difference of corona discharge in different gases may exist and affect the performance of MGSs.In this paper,the effects of needle electrode in air on single-gap corona discharge characteristics are studied.The size of corona needle electrode is determined.Then,the corona discharge characteristics in N2,CO2,SF6/N2 and C4F7N/N2 are studied.The breakdown voltage of the 6-gap gas switch and its stability with the gas type and pressure are studied.The experimental results show that the corona current is high in N2.The corona current in air is lower and the corona discharge is stable in air.The addition of electric negative gas will greatly reduce the corona current.When air and N2 are used as the switch gas,the breakdown voltage of the switch increases linearly with the increase of gas pressure,but there is a low breakdown voltage sometimes.When electric negative gas is mixed with N2,the breakdown voltage is significantly higher.When the pressure of 1%SF6/99%N2 mixed gas is 0.18 MPa,the breakdown voltage is about 197.33 kV and the ratio of the standard deviation to the breakdown voltage is 1.50%.When 1%C4F7N/99%N2 mixed gas is 0.15 MPa.The breakdown voltage is about 190.42 kV,and the standard deviation is 0.55%.This indicates that the mixed gas of C4F7N and N2 has a significant effect on improving the breakdown voltage stability of multi-gap gas switch.