Analysis and Design of Post Insulator of Transmission Line Towards the CRAFT NNBI Test-Bed

High voltage transmission line (HVTL), which adopts the gas insulated transmission line (GITL) technology, is an important link between the radio frequency ion source system and the power supply system for the negative-ion based neutral beam injectors (NNBI) system. Post insulators in the HVTL play the role of supporting high voltage conductors, and their performance and reliability directly determine the technical level and long-term operation reliability of the whole HVTL. In this paper, two kinds of metal inserts with different structures are proposed and their insulation properties are compared, and then the factors affecting the insulation performance of the post epoxy resin composite insulator are analyzed, including the column radius of the post insulator, the radius of the metal insert, the embedding depth of the metal insert, and the arc height of the metal insert. And draw the following conclusion by finite element analysis: from the point of view of the electric field, the comprehensive good insulation performance can be obtained by reducing the column radius of the post insulator, increasing the radius of the metal insert, reducing the embedding depth of the metal insert and increasing the arc height of the metal insert, appropriately. According to the design requirements of the insulation, the structural design parameters of the main post insulator and metal inserts in the HVTL are preliminarily determined, which lays a theoretical and engineering foundation for the follow-up engineering design of the insulation support of the HVTL.