The influence of moisture on low voltage oil-and-paper insulated distribution cables

The nature of failure in low voltage (LV) systems is still not well understood, despite substantial research activity aimed at understanding degradation mechanisms in medium and high voltage cables. Investigation into the movement of moisture in oil-and-paper insulated LV cable cores shows that moisture ingress is far from uniform. The transfer of moisture across the composite insulation has been measured using Karl-Fisher titration and a tracer dye. Experiments are reported on factory laid-up cables. These are used to develop an understanding of the mechanism of moisture diffusion which occurs prior to breakdown. It is found that the combination of Karl-Fisher titration and tracer dyes is required in order to fully identify the distribution of moisture in the cable.