Abstract:

In order to solve the partial discharge problem of the EVT inner cone casing in the primary and secondary fusion ring cabinet,the electrostatic field analysis is carried out first to extract the electric field distribution in the area with relatively concentrated electric field.Then according to the high voltage electrode voltage sharing technology and the gas-solid composite insulation theory,the structure of the EVT center copper rod,the shape of the EVT end and the matching clearance with the high pressure end face of the casing are optimized.After optimization,the maximum field strength along the three interfaces of the EVT inner cone casing is reduced from 2.85 kV/mm to 1.75 kV/mm,and the maximum field strength at the end of the casing is reduced from 3.90 kV/mm to 2.35 kV/mm.The feasibility of the method is verified theoretically.The partial discharge test shows that the local discharge quantity is reduced from 42.54 pC to 1.05 pC after optimization,which proves the practical feasibility of the method,and provides a favorable guidance for the research and development of the composite insulation structure related to the quasi-primary and secondary fusion of 10 kV and higher voltage levels.

Key words: electronic voltage transformer(EVT), inner cone casing, partial discharge, electric field analysis, insulating structure