A Segment Insulation Diagnosis Method of Power Cable Based on Attenuation Coefficient in Frequency Domain

In recent years, the frequency domain reflection (FDR) method has been widely used in power cable defect location detection. However, the FDR method only diagnoses the change of insulation state at the defect and ignores that of the cable body. Thus, based on the mathematical model of the reflected wave of the power cable, a method to diagnose the insulation state of each segment of the power cable by using the attenuation coefficient is proposed in this article. In the method, the reflection coefficient spectrum (RCS) of a power cable and the location of defects are obtained by the traditional FDR method, and the power cable is divided into several segments based on the location of defects. Then, the two-point interpolation fast Fourier transform (I2pFFT) algorithm is used to estimate the attenuation coefficient of each segment in the RCS. Theoretically, the value of the attenuation coefficient is a characteristic of the change of the dielectric constant of the cable, thus the insulation state of the power cable can be diagnosed by attenuation coefficient. Finally, the feasibility and validity of the proposed method are verified by simulation and field 2 km/27.5 kV cable, respectively. The experimental results show that the proposed method can effectively diagnose the insulation state of each segment of the power cable.