关于冲击接地电阻测量的探讨

Discussion on the Impulse Grounding Resistance Measurement

工频接地阻抗测量的常用方法是IEEE推荐使用的电位降法,基于此,国内的实际操作中,测量方法大致采用远离法和补偿法。但冲击接地阻抗的测量国内外还没有比较成熟的理论。为此,通过数学模型建立目标函数,利用最优化方法—变度量法较精确地求出双指数函数中的参数;借助于傅氏级数把双指数函数转化为很多正弦函数的和。转化结果表明,冲击电流与工频电流类似,冲击接地电阻可按类似工频接地阻抗测量的方法测量;冲击电流下电压和电流引线间的互感比工频电流下大很多,冲击电阻测量时不能忽略引线间的互感。

The most popular method for power grounding resistance measurement is the fall-of-potential method, which is recommended by IEEE. In practice in China, the long-lead method and the compensating method are traditionally used to measure the grounding resistance, which are based on the fall-of-potential method. But the measurement of impulse grounding resistance don＇t have relativily perfect theory at home and aboard. By establishing a mathematical model and using an optimization method, the variable metric method,,an object function is established and parameters of the double exponential function are accurately solved. By aid of the Fourier series, the double exponential function is transformed into the sum of many sinusoidal functions. From transformation result, impulse current is similar to power frequency current, so impulse grounding resistance is measured by the method measuring power frequency grounding resistance. The inductive couplings between current and potential leads are compared respectively in power frequency current and impulse current, and the latter is much higher than the former, so the inductive coupling between current and potential leads can not be neglected in the measurement of the impulse grounding resistance.