Thermal Aging-Based Degradation Parameters Determination for Grid-Aged Oil Paper Insulation

Abstract

Elevated thermal stress-related aging is significant on the oil-impregnated paper (OIP) used as insulation in high-pressure gas cables (HPGCs). The aim of this article is to develop a cheap alternative for lab dielectric measuring and characterizing temperature-dependent parameters for OIP. First, this article derives the operating thermal conditions of the grid-aged cable based on IEC standards after analyzing the loading data using machine learning techniques to determine the elevated temperature levels for the experiments. Second, a novel lab-fabricated inexpensive electronics circuit is developed for polarization and depolarization current (PDC) measurements which can be adapted for such measurements over expensive commercial devices. From the measured parameters, an extended three-branch Debye model is optimized using a developed error function approach based on the Akaike information criterion (AIC) and goodness of fit. The model indicated a reduction in the branch resistance with temperature elevation and aging, whereas the branch capacitance revealed an increasing trend. The resultant relaxation time (RC) showed a decrease overall. Last, a short-duration frequency domain spectrum was analyzed and extrapolated to obtain parameters for a wide range of frequencies and fit in a Cole-Cole model, derived for oil-paper insulation. The time constants obtained from this model also confirmed a reducing trend across the temperature and aging variations and the model parameter, the alpha coefficient showed a decreasing trend. Last, the effect of the measured dielectric parameters is reflected with breakdown values to investigate the effect of temperature on the electrical life of insulation.

Research on the Thermal Aging Characteristics of Crosslinked Polyethylene Cables Based on Polarization and Depolarization Current Measurement

“…depolarization current and time, DC conductivity and its non-linear coefficient, 0.1 Hz dielectric loss and its non-linear coefficient, etc., from PDC measurement results, to diagnose the insulation condition of cables [9][10][11][12]. These parameters can reflect the overall electrical performance of the cable.…”

“…The polarization and depolarization current (PDC) measurement has been increasingly applied in the evaluation of the insulation condition in recent years due to its advantages of fewer measurement modules, lightweight equipment, lower cost, and shorter measurement time [6][7][8]. Researchers have extracted various diagnostic parameters such as the polarization current, aging factor, PDC slope, relationship between the depolarization current and time, DC conductivity and its non-linear coefficient, 0.1 Hz dielectric loss and its non-linear coefficient, etc., from PDC measurement results, to diagnose the insulation condition of cables [9][10][11][12]. These parameters can reflect the overall electrical performance of the cable.…”