Study on Air Gap Discharge Characteristics of Fittings at the End of Bushing in High Altitude UHV Converter Station

The construction of high-altitude UHV converter stations faces the primary challenge of determining the safety distance required for the external insulation within the converter station valve hall to surrounding objects, and the long-gap safety distance between the valve hall bushing terminal fittings and the ground or the walls directly determines the size of the valve hall. This paper sets up a simulation model of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 800\text{kV}$</tex> converter station valve-side bushings to the ground, to the front wall, and to the side wall to study the electric field distribution characteristics of the bushing fittings, and provides the safety distance for the bushing terminal fittings to the ground and to the wall. Meanwhile, in the Qinghai high-altitude test hall at an altitude of 2300 meters, operational surge discharge tests were carried out on the comprehensive gap between the valve-side bushing terminal fittings and the ground and the wall. The curve of the 50% operational surge discharge voltage U50 versus the power index of the different air gap distances d was fitted, and the discharge characteristics were analyzed.