Modelling for switching impulse breakdown of live working gaps between equipotential worker and transmission towers

摘要

Air gap discharge voltage is the key parameter to determine the minimum approach distance for live working. In this study, a mathematical-physical model for predicting 50% discharge voltage of the transmission line air gaps considering the effect of live line worker is developed based on the continuous leader inception criterion. Also, the tower structure coefficient S-T is proposed to represent the influence of various tower structures and S-T is calculated by finite element method. Finally, the switching impulse discharge tests of the equipotential worker-tower structure gaps are carried out on 750 kV transmission lines to verify the proposed model. The research results show that the errors between the calculation and experimental data are within +/- 4.03% which demonstrates the feasibility of discharge voltage prediction for complicated live working gaps. This model offers a possible way to determine the safety air gap distance for live working by analytical and numerical calculation rather than costly and time-consuming experiments.