基于试验分析的变电站接地网冲击特性研究

Experimental Analysis on Impulse Characteristics of Substation Grounding Grid

为有效分析变电站接地网的冲击特性,提高变电站电气设备的运行可靠性和确保人身安全,文中以35 kV变电站用典型接地网为依托,基于量纲相似原理设计和定制了规则形状和不规则形状的两种接地网模型,通过模拟接地网导体变细、断裂和脱焊等典型故障,对接地网模型的冲击特性进行了试验研究。试验结果表明:接地网的冲击特性随冲击电流波形、注入点不同有较大差异,且规则接地网的暂态散流特性优于不规则接地网;对同一冲击电流注入点,冲击电流波形的波头时间越短,接地网的冲击接地电阻越大;冲击电流从接地网中心注入时,对应的冲击接地电阻最小;此外,接地网存在典型故障时,冲击接地电阻较之正常工况均有所增大,但增幅与冲击电流波形的波头时间有关。

To effectively analyze the impulse characteristics of a substation grounding grid and ensure the reliable operation of electrical equipment in the substation as well as the security of personnel, two grounding grid models with regular and irregular configurations were designed according to the real grounding grid in 35 kV substations on the basis of the principle of dimensionless similarity. The typical faults of grounding grid, including corrosion and fracture, were simulated with the models, and experiment was conducted to measure the impulse grounding resistance of the grounding grid models. The experimental results show that： 1）The impulse characteristics vary with the impulse current and the injecting position;2）The transient leakage current characteristics of the regular grounding grid is better than that of the irregular grounding grid; 3）For the same injecting position of impulse current in grounding grid, the shorter the wave head of impulse current, the higher the impulse grounding resistance of the grounding grid;4）The impulse grounding resistance get the smallest when the impulse current is injected to the center of the grounding grid; and 5）The impulse grounding resistance increases when there are typical faults in the grounding grid, and the increment of the resistance depends on the wave head of impulse current.