A Reflection Coefficient Estimation Method for Power Cable Defects Based on Three-Point Interpolated FFT

The reflection coefficient of reflected wave is one of the most important parameters to characterize the damage degree of power cable defect. However, due to the attenuation and the crossing coupling among the reflection coefficients of each defect, the reflection coefficient of the reflected wave can be hardly estimated, resulting in inaccurate power cable fault diagnosis. Thus, a method based on three-point interpolation fast Fourier transform (FFT) to estimate the reflected amplitude of cable defects is proposed. First, three adjacent points on each spectral peak in the frequency domain are selected to accurately analyze the exponential signal in the frequency domain and gain the parameters, including the amplitude and phase of the reflected wave at the defect. Then, the state of the defect is evaluated by the reflection coefficient at the defect. Finally, the simulation result shows that both the amplitude and phase relative errors of the proposed method are less than 10%; meanwhile, the experiment results prove that the proposed method can accurately judge the state of the cable defect.