中文摘要：

V串绝缘子在输电线路中得到了广泛应用,但其与I串绝缘子的冲击闪络特性差异尚不明确。为此,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 kV复合绝缘子在操作冲击和雷电冲击作用下的放电试验,并通过有限元仿真软件对2种悬挂方式下复合绝缘子附近的电场分布进行仿真分析。结果表明：当有效绝缘距离相同时,正极性冲击电压下的V串绝缘子50%冲击放电电压低于I串绝缘子,而负极性冲击电压下的V串绝缘子50%冲击放电电压高于I串绝缘子;V串缘子下均压环与横担间的空气间隙的电场分布更接近棒–板间隙,而I串绝缘子2个均压环间的空气间隙的电场分布更接近棒–棒间隙。因此,I串和V串绝缘子间冲击闪络特性的差异是由于电极结构的极性效应引起的。

英文摘要：

V-string insulators are widely used in transmission lines, but the difference of impulse flashover characteristics between V-string insulators and I-string insulators remains unclear. To this end, we carried out discharge tests of ±800 kV V-string and I-string composite insulators under lightning and switching impulses at the（Kunming） National Engineering Laboratory for UHVDC Engineering Technology. The electric field distribution around the tested insulators was calculated and analyzed using the finite element simulation software as well. The results show that, compared with I-string insulators with the same effective insulation distance, the 50% impulse discharge voltage of V-string insulators is higher under negative impulses, but is lower under positive impulse voltages. The electric field distribution of the air gap between grading ring and cross arm in a V-string is similar to that of a rod-plate air gap, while the electric field distribution of the air gap between two grading rings in an I-string insulator is similar to that of a rod-rod gap. It is concluded that the difference of impulse flashover characteristics between V-string and I-string insulators is caused by the polarity effect of different electrode structures.