Defect Localization for Power Cables with Chirp Z-Transform of Reflection Coefficient Spectrum

Frequency domain reflectometry (FDR) has been proved promising to locate the defect of power cables, yet the traditional fast Fourier transform (FFT)-based algorithm faces problems including low localization resolution and high data redundancy, resulting in lower accuracy of the defect localization results. In this paper we proposed a defect localization method for power cables based on chirp Z-transform of reflection coefficient spectrum. The method can arbitrarily adjust the resolution of the defect localization function with chirp Z-transform algorithm, thereby obtaining better localization effect at the same sampling points compared with FFT, and also reduces the data redundancy and eliminates the influence of interference peaks. Simulations of the method on artificially defected cables prove its accuracy to identify cable defects of different types, levels, and locations. The maximum absolute localization error was only 0.65 m, and is less affected by the number of sampling points. Field tests on actual 256 m/10kV cables with shielding layer corrosion, and 500 m/10kV cables with shielding layer rupture and loose wrapping further verified the effectiveness of the method, with defect localization errors of 0.64% and 0.21%, respectively. Simulation and field test results prove that the proposed method can effectively locate defects of power cables with higher accuracy and correctness.