Detection and Diagnosis of High Voltage Cable Water-Blocking Buffer Layer Defect based on Frequency Domain Reflection Method

This article investigates the detection and diagnosis of defects in the water-blocking buffer layer of high-voltage cables using frequency domain reflectometry (FDR). Firstly, considering the possibility of the buffer layer affecting the distributed parameters of the cable, a parameter model for the distributed capacitance and distributed conductance of high-voltage cables is derived from electrostatic field theory. Then, based on the surface morphology characteristics of the buffer layer, the state of the buffer layer is classified into dry, moisture, corrosion, and ablation. The volume resistivity and relative permittivity of the buffer layer in different states are tested using sheet samples, and the influence of these states on the distributed conductance and distributed capacitance of high-voltage cables is further analyzed, obtaining the mechanism of how buffer layer defects affect the characteristic impedance of high-voltage cables. Finally, by constructing an experimental platform for detecting buffer layer defects in high-voltage cables in the laboratory, it is confirmed that the FDR method can effectively detect and diagnose defects in the buffer layer of high-voltage cables.