Contact Failure Characteristic Test and Overheating Analysis of UHV GIL Electrical Connection Structure

As the key component of the conductor of the gas-insulated power transmission equipment, the electrical connection structure bears high current, high stress, and high temperature for a long time. Electrical contact failures become an important issue, while its failure characteristics and mechanisms are ambiguous so far. In this article, based on complex electrical connection structures of gas-insulated transmission line (GIL), equivalent tests were conducted on the contact failure characteristics of such structure. Result shows that poor contact of the such electrical connection structure will cause two types of situations: microgap discharge and contact overheating. The causes of both are different. First, microslip is a kind of cause of discharge faults despite the separation gap is small. The current transfer area ( ${b}$ ) of such contact structure is the main position, where the arc starts. The contact stability at that location should be fully considered in the layout of such electrical connection structure. Second, combined with the surface morphology and element distribution, the mechanism of contact discharge and the source of metal particles are further explained by the occurrence of coating peeling and material transfer behavior. Finally, the difference in contact state is the main reason for a few contacts overheating. There is a significant temperature difference between contacts in different contact states. The temperature rises nonlinearly with the increase of the current under the condition of uneven current carrying. The above research can provide a practical basis for fault analysis and prevention of such electric contact structures in the ultrahigh voltage (UHV) gas-insulated power transmission equipment.