信号注入法在配电网电容电流测量中的研究

Research on capacitive current measurement with signal injection in distribution network

为了使配电网电容电流的测量更简单、安全,提出了一种新的电容电流测试方法。该方法从母线电压互感器二次侧开口三角注入2个幅值相同、频率不同的电流信号,通过测量注入电压与注入电流的幅值与相位关系,可以求解出线路的对地电容值。注入电流信号的频率对测量结果的精度有很大的影响,对于不同对地电容值,频率的选取范围也不相同。该方法通过自适应技术,自动获得最合适测量频段,从而保证了电容电流测量的正确性。通过在实际测量中与理论计算的电容电流值、消弧线圈测量的电容电流值比较,可以验证该方法的测量结果具有很高的精度。采用本方法测量配电网电容电流不需要涉及一次设备,具有安全、便捷的特点。

This paper presents a novel method to measure the capacitance current of the distribution network.In the method,two currents with the same amplitude and different frequencies are injected into the system from the secondary winding of potential transformer(PT)and the voltage of the PT is measured.By the equation erected,the earth capacitance can be calculated.The frequencies of the signal injected are important factors which affect the precision of the measurement.So the frequencies should be selected carefully.For different capacitors,the frequencies are not the same.This method applies an adaptive approach to choose the frequencies automatically.The results of the method are compared with the theoretical value and the results measured by arc suppression coil to prove the feasibility.The use of this method does not involve primary system and is safe,easy and convenient.