In recent years, the method based on the vertical lifting method to enter and exit the equipotential of mid-range-wire has been applied to 500kV and above lines. However, for 220kV and 110kV lines, this method has not been applied due to the lack of research on the technical requirements for safe operation. In this paper, aiming at the common 220 and 110kV mixed voltage lines in Jinhua areal, the discharge characteristics of the interphase combination gap are studied, and the discharge characteristics formula of the interphase combination gap of entering and exiting the mid-range-wire equipotential is obtained, and the application safety of this method is analyzed by checking the interphase combination gap. The results show that for this kind of line, the risk rate of live working on middle wirel is less than 1.0×10-5 by using this method, which meets the safety requirements of live working.

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