Online Monitoring for Underground Power Cable Insulation Based on Resonance Frequency Analysis Under Chirp Signal Injection

Online monitoring for underground power cable insulation has become an urgent need in distribution grids, which can lead to proactive maintenance and avoid severe insulation faults. Insulation capacitance has been selected as an effective insulation condition indicator in many researches, but the variation of insulation conductance is always overlooked, resulting in a limited monitoring range and sensitivity. To solve this problem, a novel online monitoring method for underground power cable insulation based on resonance frequency analysis under chirp signal injection is proposed in this article. An online monitoring scheme based on common-mode chirp signal injection is first designed, realizing online monitoring in a nonintrusive manner. The resonance frequency under the injected signal is then analyzed, providing an effective approach to monitor insulation capacitance regardless of the accompanied insulation conductance variation. Simulations and experiments are carried out, proving the effectiveness of the proposed method for different system operating conditions.