Weibull分布在真空断路器容性关合预击穿特性研究中的应用

Application of Weibull Distribution in Prebreakdown Characteristics when Capacitive Closing of Vacuum Circuit Breakers

当前选相合闸技术在断路器的容性开合工况中应用越来越广泛,而预击穿开距的分散性严重制约着选相关合策略。文中的研究目标是采用熔铸法制备灭弧室触头的40.5 kV真空断路器在容性开合运行工况下的预击穿开距分布情况。试验中采用熔铸法制备的直径为50 mm的CuCr40触头作为试品,通过L-C振荡回路产生了幅值6.48 kA、频率207 Hz的关合涌流,考虑35 kV三相不接地系统中容性系数为1.4的情况,关合过程中的外施电压设为46.3 kV。试验结果表明,预击穿开距dpre的余补累积概率满足三参数Weibull分布,并且3只灭弧室试品总是发生预击穿的预击穿开距基本相同,均为约1.6~1.9 mm,而预击穿开距的分散性则各不相同,约为3.4~6.0 mm。这意味着随着关合操作次数的增加,灭弧室的预击穿开距分布会显著变化,因而对于在真空断路器进行容性开合时考虑采用选相合闸技术而言,预击穿开距的分布是至关重要的。

Nowadays the phase controlled switching is a preferred method for capacitive switching.Thus the distribution of pre-breakdown gaps is an important issue for the control strategy.The objective of this paper is to understand the distribution of pre-breakdown gaps for the contact materials manufactured by casting preparing technology in the capacitive service condition of 40.5 kV vacuum circuit breakers(VCBs).In the experiment,CuCr40 contacts with a diameter of 50 millimeters are prepared by casting technology respectively.L-C oscillating circuit generated inrush current with a frequency of 207 Hz and with a peak of 6.48 kA,while the applied voltage was 46.3 kV which is equivalent to the peak voltage for a 35 kV three-phase network whose capacitive voltage factor is 1.4.The experimental results show that the complementary cumulative probability of the pre-breakdown gap dpre follows the 3-parameter Weibull distribution.The prebreakdown gap below which pre-breakdown would always occur is similar for all three test VIs(Vaccum interrupters)which is 1.6~1.9 mm,and the scattering of the prebreakdown gaps is different which is 3.4~6.0 mm,too.It means the distribution of pre-breakdown gaps for all three VIs significantly varies with closing operations.Thus the distribution of prebreakdown gaps is important when employing phase controlled switching in VCBs for the capacitive switching.