Design of the Polymer Insulator between HVDC Converter Valve Modules

The polymer insulator between HVDC converter valve modules is one of the key elements of ultra-high voltage dc transmission. In prior to designing dimension of shed, end fitting, and sealant of polymer insulator, the dc electric field analysis should be conducted. Therefore, the electrical conductivity of the polymer specimens was measured for various temperature since the electrical conductivity depends on the temperature. Based on measured electrical conductivity of specimens, the dc electric field analysis for 4 types of polymer insulators were carried out. From the simulation results, the specimen with the lowest dc electric field was selected. Besides, the dielectric strength of polymer should also be determined in designing the polymer insulator. Therefore, the experiment on determining the dielectric strength of the polymer was conducted. The test jig for breakdown tests was fabricated corresponding to the IEC 60243–1 standard. The dc breakdown tests were corresponded to the IEC 60243–2. In addition to breakdown test, the surface flashover test was also conducted. The test jig was designed using the uniformity of electric field based on the dc electric field analysis and the surface flashover test on the polymer specimens was performed.