中文摘要：

作为输电线路雷电屏蔽分析模型中的关键物理过程，关于上行先导起始机制及其判据的研究尚待深入。基于先导放电物理机制，建立了导线表面稳定上行先导起始仿真模型，并利用模拟电荷法计算分析了导线周围电场分布特征。结果表明，稳定先导起始时，导线周围平均电场强度达到流注场强的区域几乎不受雷电参数和导线参数的影响，由此提出一种上行先导起始新判据，即当线路周围一定区域内的平均电场强度达到流注场强时，稳定连续的上行先导起始。长间隙放电观测结果及对国内外典型线路雷电屏蔽性能的计算结果与运行数据相符，验证了该判据的有效性。通过与以往上行先导起始判据的比较分析，指出已有的输电线路先导起始判据可能会夸大上行先导的引雷作用。

英文摘要：

As a key physical process of the lightning shielding analysis model, the inception mechanism and criterion of the upward leader need further understanding and clarification. Based on the leader discharge theory, a numerical simulation model for analyzing the inception of stable upward leader issued from a conductor was presented. The charge simulation method was utilized to analyze the electric field distribution around the conductor. Results show that the influence of lightning parameters and conductor parameters on the range of the area, where the average electric field near the conductor exceeds the electric field of the streamer zone when a stable upward leader incepts, is quite limited. The paper thereby proposed a new inception criterion for the upward leader, the kernel of which is‘when the average electric field of a certain distance from the conductor reaches the electric field of the streamer zone, a stable upward leader will incept.’ The observation results of long air gap discharge for the horizontal conductors under laboratory conditions were used to verify the proposed criterion. A lightning shielding analysis model was established based on the proposed criterion, which reproduced the shielding failure performance of the typical 500 kV transmission lines in China and UHV transmission lines in Japan. The model-based calculation results agree well with the field data, which shows effectiveness and validity of the proposed criterion. Also, comparative analysis indicates that the existing criteria may somewhat overestimate the upward leader inception from transmission lines.