地线绝缘子异常放电等问题在电力系统中时有发生，严重威胁了输电线路的安全运行，主要原因包括地线绝缘子间隙距离选择过小，地线感应电压过大，绝缘间隙电极易松动等。本文研究了带并联间隙的地线绝缘子的绝缘配合问题，通过仿真计算和试验研究，确定了地线绝缘子间隙距离的合理范围。首先，本文搭建了电压等级为750kV的同塔双回输电线路仿真计算模型，计算得到了架空地线采用不同接地方式下感应电压和感应电流的沿线分布及电能损耗。此外，研究了地线感应电量和电能损耗的影响因素，探究了降低地线感应电压的方法。研究结果表明：架空地线采用分段绝缘、单点接地的接地方式时，可以大大降低感应电流和电能损耗，并且可以降低地线发热断股的风险；当架空地线感应电压过大时，可采用降低地线分段距离、绝缘段地线中点接地和输电线路逆向序排列等方式降低感应电压幅值。其次，对地线绝缘子并联间隙进行了工频击穿特性和雷电冲击特性研究，研究结果表明：间隙的击穿电压随间隙距离的增加呈近似线性增长；当间隙距离为10mm和20mm时，在淋雨强度为14mm/min的特大暴雨下，工频击穿电压与干闪电压相比降低超过50%。因此，在地线绝缘子的实际工程应用中，应当考虑降雨对并联间隙工频击穿电压的影响，建议并联间隙距离不应低于20mm。最后，本文对绝缘子洁净状态下和染污状态下的雷电冲击闪络特性及其与并联间隙之间的绝缘配合进行了研究。研究结果表明：染污受潮状态下的单片绝缘子的标准雷电冲击闪络电压有所降低，染污绝缘子闪络发生靠近波前时间时，盐密值的变化对闪络电压影响较小；闪络发生在波尾时，盐密值的变化对闪络电压的影响较大。本文根据绝缘子及并联间隙的绝缘配合结果给出了三种盐密值下并联间隙的最大距离。
Problems such as abnormal discharge of ground insulators often occur in power systems, which seriously threaten the safe operation of transmission lines. The main reasons include the selection of ground insulator gap distance is too small, ground induced voltage is too large, and insulation gap electricity is easily loose. In this paper, the insulation matching problem of ground insulators with parallel gap is studied. Through simulation calculation and experimental research, the appropriate gap distance of ground insulators during operation is determined.Firstly, in this paper, the simulated calculation model of 750kV double-circuit transmission line is established, and the induced voltage and induced current distribution along the line and power loss of the overhead ground wire under different grounded modes is calculated. In addition, the factors affected the induced power and power loss of the ground wires are studied, and the methods of reducing the induced voltage of the ground wire are explored. The results show that when the overhead ground wire are insulated with one point grounded, the induced current and electric power loss can be greatly reduced, and the risk of ground wire heating breaking can be reduced. When the induced voltage of overhead ground wire is too large, the induced voltage amplitude can be reduced by means of ground wire segmented, ground point grounding, and reverse sequence arrangement of transmission lines.Secondly, the power frequency breakdown characteristics and lightning impulse characteristics of the parallel gap of the ground insulator are studied. The results show that the breakdown voltage of the gap increases linearly with the increase of the gap distance. When the gap distance is 10mm and 20mm, the power frequency breakdown voltage is reduced by more than 50% compared with the dry lightning voltage under the extremely heavy rain intensity of 14mm/min. For the practical engineering application of ground insulators, the influence of rainfall on the power frequency breakdown voltage of the parallel gap should be considered. It is recommended that the minimum distance of the parallel gap should not be less than 20mm.Finally, in this paper, the lightning impulse flashover of insulators in clean state and contaminated state, as well as the insulation coordination between insulators and parallel gap are studied. The results show that the standard lightning impulse flashover voltage of a single insulator decreases under the condition of contamination and damp. When the flashover occurs near the wave front time, the change of ESDD has little effect on the flashover voltage; When the flashover occurs at the tail of the wave, the change of ESDD has a great influence on the flashover voltage. Based on the results of insulation coordination between insulators and parallel gap, the maximum suitable distance of parallel gap under three ESDDs are given.
