Transient Lightning Impulse Performance Analysis of a Fully Composite Pylon with an External-grounding Down-lead

In recent years, several modern designs for pylons have been suggested with the focus on reducing environmental impact of overhead lines. Composite based pylons, since introduced in 1960s, have been considered as a promising solution for the next generation of pylons, since they are advantageous with good insulation properties, reduced weight-strength ratio and lower cost. Because of their elegant aesthetic appearance, the novel pylons may also take the place of the conventional steel lattice towers where reducing visual impact is required. Especially in humid and salty regions like seashores or islands, their excellent corrosion resistance makes them the optimal solution comparing with steel lattice towers.

A fully composite pylon has been proposed in order to meet the trend of installing new environmental-friendly overhead lines (OHLs). Since the cross-arm is no longer conductive as it is in traditional steel towers, a proper grounding method must be developed to bring ground potential to the shield wires.

Based on initial study of the fully composite pylon design, a possible method is considered: a grounding down-lead (either a cable or a bare conductor) going down outside the cross-arm and the pylon body. With this grounding method, the transient lightning current will be conducted to the ground only through the grounding down-lead. Consequently, the lightning characteristics of the fully composite pylon will be different from that of traditional ones. In order to evaluate the feasibility of the grounding down-lead in the fully composite pylon, the lightning characteristics of the composite pylon and its transient lightning impulse performance must be analyzed.

Funding: Self-financing.