Influences of semi-conductive coatings on the electric field distribution of GIS spacer interface

Ultra high voltage (UHV) AC Gas Insulated Switchgear (GIS) spacer is one of the most important components in GIS. In the process of long-term operation, partial discharge often occurs at the interface between the center conductor and epoxy resin (EP) basin body if this interface has some defects, and the discharge sometimes even leads to the crack of basin. It has become a bottleneck for the safe and stable operation of GIS equipment. In this paper, the interface material with EP, hydroxy-terminated butadiene nitrile liquid rubber (HTBN) and conductive carbon black was created, and its parameters were measured. With three-dimensional finite element method, the interfacial structure with semi-conductive coatings were designed, the calculation models of GIS spacer which had interfacial layer structure were built. The influences of semi-conductive coatings on the electric field distribution of the interface between center conductor and basin body were studied. To different defects on the conductor surface, the improvement of the semi-conductive coatings to the electric field distribution was analyzed. Compared with the interfacial layer without coatings, there is an 80 percent decrease of electric field intensity of surface defects than that without coatings, which proves its significant shielding effect. The rationality of GIS spacer´s performance of material and structure of semi-conductive coatings are verified, which is helpful to improve the uneven distribution of electric field at the interface of UHV electrical equipment.