A Novel Dampness Diagnosis Method for Distribution Power Cables Based on Time-Frequency Domain Conversion

Dampness invasion of power cable joints may lead to cable insulation degradation gradually. Once the cable joint is severely damp, it rapidly leads to breakdown failure for the power cable insulation system and finally results in catastrophic cable accidents. To avoid power outages, it is of great significance to diagnose cable joints with severe dampness defects. Existing methods have certain limitations. In this article, a novel time-frequency domain conversion method for determining cable joints with severe dampness defects is proposed. For this method, the cable joint is first located by applying the conventional frequency domain reflectometry (FDR) technology. Then, the time domain waveform at the cable joint is obtained based on the proposed time-frequency domain conversion algorithm. Finally, the cable joint with severe dampness defect can be distinguished by judging the polarities of the time domain spectrum at the cable joint. To verify the effectiveness of the proposed method, simulations and experiments are performed with comparisons with the conventional FDR method. Simulation and field detected results prove that the proposed method can effectively distinguish cable joints with severe dampness defects.