Switching Impulse Characteristics for Air Gap of Valve Hall at 2500 m Above Sea Level in ± 800 kV Ultra High Voltage DC Transmission System

In order to accurately obtain the internal design dimensions of the delivery valve hall of the ± 800 kV UHV DC project above 2500 m altitude. In the Xining high-altitude test base at 2500 m altitude, the discharge characteristics of the phase-to-phase and relative gaps were tested by the lifting method. The switching impulse discharge voltage U50 of the typical gap was obtained, and the fitting of the discharge voltage and the gap distance was given formula. The test results show that the air gap type determines the difference of the growth rate of the discharge characteristic curve, and the increase of the radius of curvature of the equalizing ball electrode on the electrode can significantly improve the switching impulse tolerance of the gap, while for the same air gap, the positive direction. The difference in the electrode profile applied by the switching impulse surge voltage directly leads to a difference in the discharge characteristic curve.