Study on the Key Equipment's Insulation Level of ±800kV UHVDC Power Transmission Project

China is currently pushing on constructing ±800kV UHVDC power transmission projects. The Yunnan-Guangdong power transmission project to be built in 2009 will be the first UHVDC power transmission project around the world. The paper has presented insulation level and insulation coordination for the key equipment, which would be adopted in the Yunnan-Guangdong UHVDC Project. The research result herein reveals that, compared to 1.6 times insulation level of the key equipments of traditional ±500kV project, it is practical to reduce that of UHVDC project respectively, and the technical measurement would be rational arrangement of arrester and smoothing reactor and reasonable reduction of insulation margin. Furthermore, the test voltage level corresponding to long DC operation voltage has also been discussed in this paper, which is for evaluating internal insulation withstanding capability.