The effects of water immersion on the electrical properties of miniature XLPE cables

The results of an investigation into the effects of water immersion on the electrical properties of miniature cables are reported. The capacitance, dissipation factor and breakdown voltage of cables immersed in water at different temperatures and subjected to various voltages and frequencies were measured. The breakdown voltage decreased in two stages, the first stage corresponding to the growth of bow-tie trees or saturation of the insulation with water and the second stage with the occurrence of surface-originating water trees. The frequency accelerated ageing was significant between 60 Hz and 400 Hz but there was little effect between 400 Hz and 1 kHz.