Partial Discharge Characteristics in XLPE Cable Under DC Step Voltage Boost at Different Temperatures

Partial discharge (PD) can occur in cross-linked polyethylene (XLPE) insulation within high-voltage direct current (HVdc) cables with defects and the continuous development of PD will lead to the final breakdown of the cable. To study the PD behavior caused by defects in HVdc cable and provide effective guidance for the operation and maintenance of the cable, three types of defects were prepared in this article, namely microvoid, protrusion, and interface fouling. For these three typical defects, experimental research on PD under stepped voltage boosting was conducted using the pulse current method at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30~^{\circ }$ </tex-math></inline-formula>C, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~^{\circ }$ </tex-math></inline-formula>C, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$70~^{\circ }$ </tex-math></inline-formula>C, respectively. The research results indicate that the PD inception voltage (PDIV) of interface fouling is higher than that of microvoid and protrusion, while the discharge repetition rate is lower. The PD experimental results of the three types of defects all indicate that, when the defects do not develop significantly, the increase in temperature will reduce PDIV and increase their discharge frequency. The charge transfer model is employed to analyze the impact mechanisms of high temperature and electric field on the PD process, providing a rational explanation of the PD behavior during experiments. In addition, a discharge frequency evaluation method based on the equivalent circuit model of defects is proposed, which may assist in assessing defects’ destructiveness. The experimental findings and evaluation methods obtained in this study can serve as a reference for assessing the defect development process in dc cables under various operating conditions.