Lightning arrester choosing for 10kV side with no load of 220kV main transformer

Through the analyzing to arrester thermal breakdown on 10kV side with no load of 220kV main transformer, the fault direct cause is conformed that because the normal voltage of arrester (YH5WS-17/45) is too low, the arrester get over heat, and then thermal breakdown happens. The right nominal voltage choosing methods for gapless arrester and the possibility of gap zinc oxide arrester application are presented in this paper. The shortcoming of the B-phase direct grounding operating type and a arrester parallel connecting with each phase on 10kV side of transformer is the best protecting method are pointed out.