Analysis of Discharge Characteristics and Gap Factors of Large Electrode in Converter Station

With the increase of voltage level, the size of shielding fittings used in the converter station is getting larger and larger. For example, the diameter of the sphere used in the ± 1100 kV DC project reaches 2 m. Its discharge characteristics are greatly different from the typical rod-plane gap and rod-rod gap. It is of great significance to master the discharge characteristics of large-size electrode gap and the change rule of gap factor for the selection of air gap in converter station and the manufacture of high-voltage DC equipment. In this paper, the discharge curves of the sphere-ground air gap of different diameters such as 0.5–2.0 m are obtained by using the full-scale size sphere-ground air gap of the converter station. Then, according to the definition of the gap factors, the variation rules of the diameter of the sphere-ground, the gap distance and the gap factors are analyzed, and the calculation formula of the gap factor is proposed. The research results can provide an important theoretical basis for the choice of air gap between valve halls and DC field in UHV converter station.