Accurate identification of early-stage insulation aging in 10 kV cross-linked polyethylene (XLPE) cables is required for reliable operation of urban power distribution networks. In this study, the frequency- and temperature-dependent vector impedance under operating-voltage-relevant electrical stress was investigated for insulation aging assessment. Cable specimens were thermally aged at 135 °C for 0, 7, 14, 21, and 28 days. Fundamental capacitance and polarization–depolarization currents were measured at different temperatures to characterize the aging response. An operating-voltage-relevant broadband impedance circuit was then constructed, and synchronized voltage and current waveforms were acquired under 6 kV excitation from 100 Hz to 0.1 Hz at different temperatures. The fundamental capacitance and the fitted current constant bn decreased with aging time, indicating that the insulation remained in the early stage of aging. The phase difference and impedance magnitude extracted from the measurements exhibited variation trends consistent with the low-field capacitance and DC current indices. The discrimination among samples with different aging times was enhanced at 0.1 Hz. These results indicated that operating-voltage-relevant broadband impedance measurement provided a rapid sample-level method for evaluating early-stage insulation aging of 10 kV-class XLPE cable samples under operating-voltage-relevant conditions.
Hong et al. (Wed,) studied this question.