Prestriking characteristics when switching on inrush current in 40.5kV VIs

摘要

Nowadays the phase control closing technology is a preferred method for capacitive switching. Thus the distribution of prestrike gaps is important for the control strategy. The objective of this paper is to understand the distribution of prestrike gaps for the contact materials manufactured by infiltration and arc-melted preparing technology in the capacitive service condition of 40.5kV vacuum circuit breakers (VCBs). In the experiment, CuCr50 and CuCr40 contacts with a diameter of 50 millimeters were prepared by infiltration and arc-melted technology respectively. L-C oscillating circuit generated inrush current with a frequency of 207Hz and with a peak of 6.48kA, while the applied voltage was 46.3kV which is equivalent to the peak voltage for a 35kV three-phase network whose capacitive voltage factor is 1.4. The experimental results show that the complementary cumulative probability of the prestrike gap dpre follows the 3-parameter Weibull distribution. The d100 below which prestrike would always occur is similar for all six test VIs, while the scattering of the prestrike gap is different. It means the distributions of prestrike gaps for all six VIs significantly varies with closing operations as the contact materials and preparing technologies are different. Thus the distribution of prestrike gaps is important when employing phase control closing technology in VCBs for the capacitive switching.