中文摘要：

绝缘子雷击闪络判据是输电线路耐雷性能分析的重要组成部分。其中,CIGRE推荐的先导发展法得到了广泛应用。但是该模型没有考虑高海拔、先导通道内部压降El和末跃过程。因此,在特高压工程技术（昆明）国家工程实验室,开展了V串和I串悬挂方式的±800 k V线路用复合绝缘子在正极性雷电冲击下的50%击穿电压U50%和伏秒特性试验。结果表明：V串绝缘子U50%比相同绝缘长度的I串低,且伏秒特性曲线较为陡峭。基于绝缘子/空气间隙放电的物理过程,考虑先导通道内部压降Ul和末跃长度hf,提出了改进的先导发展模型。结合伏秒特性试验数据,I串和V串绝缘子正极性先导发展法系数k与临界先导起始场强E0值分别修正为0.73′10-（-6）m-2/（V-2·s）、495 k V/m和0.53′10-（-6） m-2/（V-2·s）、440 k V/m。修正后的先导发展模型可以作为高海拔地区I串和V串绝缘子的闪络判据。

英文摘要：

The flashover criteria of the insulators are an important part of the lightning protection analysis methods. The leader propagation model recommended by CIGRE is widely used. However, this model hasn＇t considered the high altitude, the average electrical field of the leader El and the height of the final jump hf. Thus, 50% disruptive-discharge voltage U50% and volt/time curve for ±800 k V V-string and I-string composite insulators were measured under positive lightning impulses at the National Engineering Laboratory for UHV Engineering Technology（Kunming）. The experimental results show that the U50% of the V-string is lower than that of I-string, and the volt/time curve of V-string is steeper. An improved leader propagation model is proposed based on the analysis of the flash over/discharge process of the insulator/gap, and the average electrical field of the leader Ul and the height of the final jump hf are considered in the improved leader propagation model. Based on the volt/time curve experimental results, the coefficient k and E0 for I-string in the positive improved leader propagation models are modified to 0.73′10-（-6） m-2/（V-2·s） and 495 k V/m respectively and for V-string are modified to 0.53′10-（-6） m-2/（V-2·s） and 440 k V/m respectively. The improved leader propagation models were proposed for the flash over criteria of I-string and V-string at high altitude.