Investigation on Intermittent XLPE-SiR Insulation Interface Breakdown for Medium-Voltage Cable Joints

Intermittent XLPE-SiR insulation interface breakdown for medium-voltage cable joints is investigated in this paper. Firstly, hypotheses on the intermittent interface breakdown mechanism of cable joints are proposed based on the equivalent interface breakdown circuit model. Secondly, an arc-thermal ablation model is constructed to validate the correlations among the states of the XLPE-SiR insulation interface and the semi-conductive layer, the arc energy, and the range of thermal ablation. Thirdly, Marx’s circuit experiment is conducted to validate the model and hypotheses. The model and experimental results show that the extra heat absorption caused by the insulation ablation and the current limitation of the semi-conductive layer are the two major factors, accelerating the extinction of arcs at the XLPE-SiR insulation interface of cable joints. This negative feedback mechanism will be weakened as the insulation and semi-conductive layer ablate due to long-term discharges. Ultimately, the formation of uncontrollable arcs may trigger serious cable joint faults.