Peculiarities of Stages in Technical State Change of XLPE Cable Couplings during Operation

Over the past few years, cases of damage to couplings on cable lines with XLPE insulation have become more frequent. Damage results for medium and high voltage couplings are different, as are the mechanisms and stages of damage development. The article shows that discharge phenomena in CL couplings with medium voltage XLPE insulation develop in three stages. The first and second stages are determined by the control of PD activity, the third is characterized by the presence of heat release, determined by thermal imaging control. For CL 110–330 kV, the mechanism of development is different - the appearance of a PD-surface discharge - a breakdown due to a different design of the coupling. The stage of local point temperature rise for high voltage couplings is not relevant due to the large number of barriers. Understanding the mechanism of defect development and the ability to determine at what stage of development it is allows timely identification of couplings in a critical state and planning for dismantling and replacement. It has been established that the state of single-phase medium-voltage cable lines is affected by heating from currents on the grounding leads, which worsen the state of the insulation of the coupling.