Improving the lightning protection effect of multi-circuit tower by installing coupling ground wire

• Erecting coupling ground wire is an effective lightning protection measure to reduce trip-out rate. Various setting positions of coupling ground wire have different impact on lightning protection effects.
• Take typical 500/220 kV and 220 kV quadruple circuit transmission lines for instance, the paper presents effects of setting coupling ground wire on the center of cross-arm at different height.
• The shunt coefficients of tower, ground wires and coupling ground wire, and the coupling coefficient in the condition of various mounting positions are discussed.

Erecting coupling ground wire is a type of effective lightning protection measure to reduce trip-out rate of back flashovers. Nowadays coupling ground wires has been applied on some multi-circuits transmission lines in China. However, various setting positions of coupling ground wire have different impacts on the lightning protection effects, especially the multi-circuit lines. Taking the typical 500/220 kV and 220 kV quadruple circuit transmission lines for example, the paper presents and analyzes the effects of setting coupling ground wire on the center of cross-arm at different heights. The shunt coefficients of tower, ground wires and coupling ground wire, and the coupling coefficients are also compared and discussed in situations that the coupling ground wire is mounted in different positions.