脉冲电压法检测空心电抗器的FFT波形特征及其故障判别方法

脉冲电压法是检测空心电抗器匝间绝缘故障的有效方法,但其时域检测波形的故障特征识别难度大,本文提出利用其FFT波形特征来判别故障的方法。通过有限元法计算了空心电抗器不同部位故障时线圈组非故障各层线圈电感值及线圈组总电感值的变化规律。为线圈组模型添加脉冲振荡回路,将得到的电抗器两端电压的时域波形利用FFT转换为频域波形。对比分析了不同故障部位的FFT波形变化特征,认为不同故障部位的空心电抗器FFT波形衰减谐振频率的变化是由电感值的变化引起的,为频域故障判据提供了数学支持。以故障线圈组的FFT波形峰值点对应频率为判据,提出了基于FFT波形特征的电抗器故障及故障程度的判别方法,并进行了实例验证。所得结果进一步拓展了脉冲电压法检测空心电抗器匝间短路故障的有效性和精确性,为进一步准确判断空心电抗器匝间短路缺陷提供了方法指导。

FFT Waveform Characteristic Detection and Fault Recognition of Air-core Reactor by Pulse Voltage Method

The pulse voltage method is an effective method for detecting inter?turn insulation faults in air?core reactors,but it is difficult to identify fault features in the time domain detection waveform.In this paper,a method to identify faults by using its FFT waveform characteristics is proposed.The finite element method is used to calculate the variation rules of inductance of each of layer and total inductance of the coil group of no?fault of coil group in case of fault at different positions of air core reactor.To add pulse oscillation circuit to the coil group model to transform the time domain waveform of voltage on both ends of reactor into frequency domain waveform by way of FFT.The FFT waveform variation feature of different fault locations are compared,thinking that the variation of the attenuation resonant frequency of FFT waveform of air core reactor at different fault positions is due to the variation of inductance,which provides mathematical support for the frequency domain fault criterion.Taking the frequency corresponding to the peak point of the FFT waveform of the faulty coil group as the criterion,a method for judging the fault and the degree of fault of the reactor based on the characteristics of the FFT waveform is proposed,and verified by actual example.The results obtained further expand the effectiveness and accuracy of the pulse voltage method for detecting the turn?to?turn short?circuit faults of air?core reactors,and provide method guidance for further accurately determining the turn?to?turn short?circuit defects of air?core reactors.