The problem that the partial discharge level has exceeded acceptable level during dielectric type test of the KGWF-4500/167 thyristor valve that consists of 6 inch thyristor firstly was the dielectric problem

which could affect the safe and reliable operation of thyristor valve.By investigating with a UV camera detailed inspecting in this area

supposing the position appearing partial discharge and verifying it

writer conclude finally partial discharge activity appeared between the bracket and the lower water pipe.The reason partial discharge exceeded acceptable level was that the air clearance was not enough.After a minimum air clearance value has been assessed and verified

the laminate supporting plate has been redesigned by considering 30% margin of air clearance.So

the problem of partial discharge exceeded acceptable level has been resolved.The supporting plates have been redesigned and applied in actual xibei-huazhong BtB extending project.In this paper

a rapid method of finding

analyzing and solving problem witch comes forth during type test of actual project has been introduced.