Experimental investigation on the minimum approach distance for live working on 1000kV UHV compact transmission line

The reliability of UHV transmission system is important to the power grid and live working technology is a key method to cope with line components defects or fault without outage plan. In order to satisfy the design requirement of the UHV compact transmission lines, and to provide parameters for live line maintenance on those transmission lines, the air gaps switching impulse voltage discharge tests for typical working positions in the compact transmission line were tested at 1:1 ratio scale simulated tower in this paper. And the discharge characteristics of live working gaps were determined through the up and down voltage method. According to the risk criterion for live working, the minimum approach distance ensure that live working risk less than 1.0 ×10⁻⁵ in AC transmission line during working process exposed to statistical excepted maximum overvoltage level, and the live working minimum approach distance for phase to ground and phase to phase are 8.4m and 11.6m respectively at an altitude of 1000m and the below areas. The minimum approach distance for tension tower is 6.3m. The research results to provide references for the design and maintenance of UHV compact transmission lines and are benefit to ensure the reliability of the power grids.