Evaluation of the Dielectric Response Characteristics and Insulation State of Cables Under Impulse Voltage

To address the shortcomings of the traditional frequency domain spectroscopy (FDS) in cable insulation testing, a new method is proposed to evaluate the cable insulation status based on the dielectric response characteristics of cables under impulse voltage, and its theoretical and experimental validation is carried out. By analyzing the spectral characteristics of the shock signal and the polarization characteristics of the insulation medium, the feasibility of the shock dielectric spectrum method of insulation state assessment is demonstrated; the dielectric response law of cables with different water tree lengths is simulated by using electromagnetic transient program (EMTP), and the feasibility of the method is verified theoretically; the short cable specimens with different water tree lengths are cultivated through the water tree accelerated aging, and an impact experimental platform was built for experimental testing. The experimental results show that: the short cable samples with different degrees of aging can be effectively identified by using the dielectric-frequency spectrum below 1,000 Hz, and the long cable can be effectively determined by using the complex capacitance imaginary part-frequency spectrum to determine whether there are local aging defects. The results of the study show that the dielectric response characteristics under shock can effectively evaluate the insulation aging status of cables.