Moisture ingress into low voltage oil-impregnatedpaper insulated distribution cables

Investigations into the effect of moisture on the degradation of oil-impregnated-paper (OIP) insulated low voltage cables have shown that moisture ingress plays a key role in cable failure, and that the ionic content of the moisture is critical. Here moisture ingress into OIP insulated cable is studied in the laboratory. Experiments have been performed in which cable samples have been exposed to moisture for varying periods, allowing the progress of moisture diffusion within the insulation to be studied. Karl-Fischer titration and observation of dye movement have been used to measure moisture transport. Moisture within a ´wet cable´ is shown to be non- uniformly distributed within a sector-shaped core, and dependent on the temperature of the cable. Measurements of insulation conductivity are presented illustrating the resulting macroscopic changes to insulation properties for comparison. An increased rate of penetration of moisture into the cable core results at elevated temperatures, whereas saturation levels are reduced.