考虑土壤非线性的输电线路暂态过电压特性研究

Transient Overvoltage Characteristics of Transmission Lines Considering Soil Non-Linearity

土壤非线性效应将导致接地装置接地电阻具有时变特性,进而显著影响输电杆塔的电位分布,因此准确研究考虑土壤非线性效应的输电走廊雷击暂态过电压特性具有重要意义。本研究建立了一种考虑土壤非线性特性的典型220 kV输电线路暂态过电压模型。首先融合接地导体有损长线模型与EMTP,构建考虑土壤非线性特性的接地装置时变电路模型;其次通过现场试验,进行接地装置时变电路模型验证;融入绝缘子串、输电线路模块、同塔双回输电杆塔,联合构建考虑土壤非线性特性的典型220 kV输电线路暂态过电压模型;最后,基于暂态过电压模型研究典型220 kV输电走廊雷击暂态响应特性。研究结果表明:1)接地装置时变电路模型与现场试验结果平均误差仅3.6%,验证了模型的正确性;2)接地装置时变电路模型可准确模拟土壤的非线性变化特性,塔脚过电压在靠近雷电流峰值区域出现陡降,且塔脚过电压值低于单一电阻模型;3)波前时间越短,波尾时间越长,输电杆塔塔顶电位越高。

Soil non-linear effects will lead to a time-varying grounding resistance of the earthing device,which in turn significantly affects the potential distribution of the transmission tower.Therefore,it is important to accurately study the transient overvoltage characteristics of transmission corridors considering soil non-linear effects.A typical 220 kV transmission line transient overvoltage model considering soil non-linear characteristics is developed.Firstly,the grounded conductor lossy long line model and EMTP are integrated to construct a time-varying circuit model for grounding devices considering soil non-linear characteristics;secondly,the time-varying circuit model for grounding devices is verified through field tests;insulator strings,transmission line modules and co-tower double transmission towers are integrated to jointly construct a transient overvoltage model for typical 220 kV transmission lines considering soil non-linear characteristics;finally,based on the transient overvoltage model,the transient response characteristics of typical 220 kV transmission corridor lightning strike are studied.The results show that:1)the average error between the time-varying circuit model of the earthing device and the field test results is only 3.6%,which verifies the correctness of the model;2)the time-varying circuit model of the earthing device can accurately simulate the non-linear variation characteristics of the soil,and the overvoltage at the foot of the tower drops steeply in the area near the peak of the lightning current,and the overvoltage value at the foot of the tower is lower than that of the single resistance model;3)the shorter the wave front time and the longer the wave tail time,the higher the transmission tower top potential.