Detrended Fluctuation Analysis of Grounding Current for Thermal Aging Evaluation of Submarine Power Cable

Thermal aging of insulation at landing section is one of the major sources of submarine cable failure. This paper proposes a novel method for thermal aging evaluation of submarine power cables based on the detrended fluctuation analysis (DFA) of grounding current. Samples under different aging degrees are fabricated and the grounding current of each sample is tested. The distortions in grounding currents which contain subtle information closely related to thermal aging degree are collected by removing the fundamental sinusoidal component. DFA is ultimately employed to extract scaling exponents corresponding to different harmonic components as feature parameters reflecting the thermal aging degree. Results show that with the deepening of thermal aging, the scaling exponents of most odd harmonics distinct from each other and show an upward trend, so that these feature parameters can be effectively used to detect the thermal aging degree of submarine cables. Furthermore, it is also found that the scaling exponent has nothing to do with the actual voltage applied on the submarine cable. No extra data is needed except for grounding currents, greatly easing the equipment burden. This novel method proposed enables the effective thermal aging evaluation of submarine power cables with fewer devices, which both ensure the safe operation of submarine power cable and enhance the reliability of the submarine power system.