This paper presents systematic research of a grounding down-lead design and its optimization for a novel Y-shaped composite pylon. A grounding down-lead inside the cross-arm is proposed as a potential grounding method. The transient response to lightning surges is modeled in PSCAD/EMTDC for a flash of lightning striking at the tip of the pylon. Aiming at the characteristic of the pylon structure, we propose theoretical formulas to calculate the surge impedance of the inclined down-lead circumscribed by composite materials. Besides, potential multi-factors affecting BFR such as the configuration as well as the length of the down-lead, the pylon span, the dielectric constant of the filling material, the electromagnetic propagation speed of the lightning, and the capacitances between down-lead and phase conductors are investigated, after which the grounding lead system of the pylon and filling materials are determined. Afterwards, the applicability of the multi-down-lead system to increase critical current ( I_c ) is discussed considering the lightning current capacity and the corona generation. Finally, we verify the insulation of the down-lead system. Compared with that of traditional Eagle and Donau towers, the backflashover rate (BFR) of the Y-shaped pylon with an optimized down-lead system is lower than that of traditional ones.

中文翻译：

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新型400 kV复合铁塔引下线系统的设计与优化

本文对新型 Y 型复合塔的接地引下线设计及其优化进行了系统研究。横臂内部的接地引下线被提议作为潜在的接地方法。在 PSCAD/EMTDC 中对雷电浪涌的瞬态响应进行建模，以了解电塔尖端的闪电。针对塔架结构特点，提出复合材料外接倾斜引下线电涌阻抗计算公式。此外，影响 BFR 的潜在多因素如引下线的配置和长度、塔架跨度、填充材料的介电常数、雷电的电磁传播速度以及引下线之间的电容和相导体进行了调查，确定塔架接地系统和填充材料。之后，多引下线系统增加临界电流的适用性（ I _c ) 的讨论考虑了雷电电流容量和电晕产生。最后，我们验证引下线系统的绝缘性。与传统鹰塔和多瑙塔相比，优化引下线系统的Y型塔的回火率（BFR）低于传统塔。