Size Assessment of Power Cable Shield Corrosion Defects Using Double-Frequency Time–Frequency-Domain Reflectometry

Cable shield corrosion defects are a common threat to power cables, requiring precise detection and sizing for effective management. Such defect detection and location methods are widely researched. However, essentially none of them can accurately assess the length of shield corrosion defects. To solve this issue, we develop a model to represent the impact of shield corrosion. Building upon this model, we propose a double-frequency time-frequency domain reflectometry (TFDR) method. The innovation of double-frequency TFDR lies in conducting two successive measurements, with the center frequency of the second signal being twice that of the first. The length of the shield corrosion defects is determined by analyzing the measured signals using the spectrum ratio. The proposed method is validated through simulations on a 10-kV system and experiments with a SYV50-type cable. The results show that estimation errors for the defects' equivalent inductance and length are below 2% and 0.3%, respectively. Hence, double-frequency TFDR emerges as a powerful tool for assessing cable shield corrosion.