The Insulation Aging State Assessment of High Voltage Cable Based on the Isothermal Relaxation Current

Cross-linked polyethylene(XLPE) cable is widely used in power grid of various countries due to its excellent performance. However, it will be aging due to electric and thermal effects in operation, which will reduce its insulation performance and life, and greatly affect the safety and reliability of power grid. For the realization of the insulation state assessment, this paper introduces the related theory of dielectric response such as the isothermal relaxation current. Combined with the cable aging equivalent model, the isothermal relaxation current peak-split fitting method to represent the different process of relaxation according to the attenuation characteristics of isothermal relaxation current is provided. And its feasibility is verified by using the known data. The results show that the measurement method of isothermal relaxation current can evaluate the aging state of cable insulation effectively.