Research on Cable Aging Diagnosis Based on Short Circuit Response

Thermal aging is an important reason for the decline of XLPE cable insulation electrical performance. Timely detection and treatment of these aging defects are of great significance to make operation of power system safe and stable. In order to solve the problems of equipment capacity and harsh detection environment in the engineering application of thermal aging detection and diagnosis at the present, a short circuit response method based on the frequency domain characteristics of voltage waveform during short circuit is proposed, and the aging cables are detected and analyzed under experimental conditions. In this method, DC voltage source and short circuit resistance with different values are used. By measuring the short circuit voltage waveform of aging cable samples under different voltages, discrete-time Fourier transform is used to obtain their respective high-voltage frequency domain characteristic spectra based on two mathematical processing methods. Based on the Debye model and the characteristics of thermal aging defects, the two kinds of characteristic spectra of short circuit response method are analyzed. The two kinds of characteristic spectra distinguish the two aging defects by reflecting the polarization characteristic information of XLPE material in the process of thermal aging. One kind of characteristic spectrum mainly shows the overall polarization characteristics of the sample, the second kind of characteristic spectrum mainly reflects the variation of polarization characteristics at different frequencies. In addition, the 10
^-3
Hz characteristic spectrum value of one kind of characteristic spectrum, the real /imaginary peak/valley value of two kinds of characteristic spectrum and their frequency points are extracted as characteristic quantities to study the characteristics of thermal aging defect. The results show that the short circuit response method can effectively identify the thermal aging defects of cables through the high-voltage frequency domain characteristic spectrum. This method has strong anti-interference ability, small power capacity and low requirements for detection equipment. Therefore, it has strong engineering application potential.