Development of ultra-high voltage insulation technology for the power supply components in neutral beam system on ITER

Dc ultra-high voltage insulation technologies in oil, gas and vacuum have been developed. Based on these technologies, fabrication of dc 1 MV power supply components for the neutral beam (NB) system on ITER has progressed. For DC generators which insulate dc 1 MV for long pulse duration up to 3600 s, oil immersed pressboard with multi-layer structure has been improved to suppress flashover. For 1 MV transmission lines, the R&D results of gas insulations have been applied to realize the compact transmission line containing several high voltage feeders. For a HV bushing which has five stage gaps in vacuum, voltage holding capability in the multistage gaps has been found to be characterized by a total cathode area. Based on these insulation technologies, manufacturing of these components have been completed. As for DC generator and transmission line, voltage holding of 1.2 MV was successfully demonstrated. As for the HV bushing, 240 kV voltage holding for each stage has achieved. These results fulfil the ITER requirements. After that, the installation work of these components has been started in the NB test facility since December 2015