Prediction of Breakdown Voltage of Equipotential Live-Line Work Air Gaps in Transmission Lines: A Computational Discharge Model

Equipotential live-line work (EPLW) is an indispensable technology to ensure the power supply. Due to the huge risks of the strong electric field, the distance of the EPLW air gap should be greater than the minimum approach distance (MAD). MAD is determined by calculating the hazard probability according to the characteristics of the switching overvoltage and the 50% breakdown voltage of EPLW gaps. Currently, the 50% breakdown voltage is obtained by a great many actual-size discharge tests, which costs a large amount of time and workforce. In this article, a computational discharge model was presented to solve the problem. First, the discharge process of EPLW air gap was analyzed based on the test experience. Subsequently, according to each stage of the discharge process, a computational discharge model for predicting the 50% breakdown voltage of EPLW gaps was presented. Finally, the computational discharge model was applied to EPLW air gaps of ±800 kV UHVDC and 1000 kV UHVAC transmission lines. The calculated results agreed well with the test results, and the errors did not exceed 6%. This research can provide theoretical support for the transmission line design and lineman safety protection.