Distribution characteristics for initial time delay of streamer of shielding spheres under operating impulse voltage at high altitudes

Abstract

With continuous promotion of construction of UHV DC projects in high-altitude areas, it is of important theoretical and practical engineering significance to study long gap discharge characteristics at high altitudes. As the initial and key stage for development of long air gap discharge, the initial stage of streamer reflects the randomness of long gap discharge to a certain extent, and time delay characteristics are important indicators to reflect the randomness. In this paper, we build a photoelectric detection system based on the photomultiplier tube and photoelectric integrated sensor, carry out an operating impulse discharge test of long gap of the shielding sphere-plate with different diameters at altitudes of 50 m and 2,200 m respectively, obtain the space field strength, optical power, discharge current and voltage of the whole process of discharge development, and analyze the characteristics of boost time delay and statistical time delay of streamer based on the photoionization model and Weibull Distribution model. According to study results, the average value and dispersibility of initial time delay of streamer increase with the increase of altitude and electrode diameter; the boost time delay t0 of streamer decreases with increase of altitude and increases with increase of electrode size; the statistical time delay ts of streamer can properly comply with Weibull distribution, and its characteristic parameter has a clear physical meaning. The dispersibility of statistical time delay will increase with altitude and electrode size, and compared with electrode size, altitude has a greater impact on the dispersibility of statistical time delay. The study results of this paper have important guiding value for selection and optimization on clear distance of the valve hall of a converter station in high altitude areas.