Flashover performance of polluted composite insulators under AC and hybrid AC/DC field stress

摘要

Integration of a DC transmission system into the existing AC system is proposed in order to transmit more power from north to the south of Germany. Effects of such hybrid AC/DC fields on the dielectric characteristics of insulators, bushings and other power system components are unknown. The outdoor insulators of transmission lines and substations suffer from different pollution such as industrial contaminants, fog, drizzle and natural dust. These contaminations may affect the electrical performance of insulators or even lead to flashover of the insulators. There is a lot of researches about ac flashover of outdoor insulators. But in case of hybrid AC/DC voltage stress more detailed investigations are needed. In this paper the hybrid AC/DC flashover performance of insulators with various pollution layers are investigated. In order to have a comparative investigation between AC and hybrid AC/DC flashovers, four types of pollutions have been applied to the composite insulators and the flashover voltage have been measured under AC and hybrid AC/DC voltages with two different ratios of AC and DC voltages. The results show that the contribution of pollutant layer on the surface of insulator has a major effect on the flashover voltage unlike the conductivity of pollutant layer.