Mechanisms of failure in oil and paper insulated low voltage distribution cables

Despite substantial research activity aimed at understanding degradation mechanisms in medium and high voltage cables, the nature of failure in low voltage (LV) systems is still not well understood. Early stages of an investigation into the role of moisture in the ageing and degradation of oil/paper insulated LV cables are reported in this paper. Experiments have been performed in which oil-filled paper has been exposed to moisture for varying periods and then time-to-failure at constant working voltage determined. It is shown that moisture plays a key role in determining the rate of cable failure, and that the ionic content of the moisture is critical. Pre-breakdown discharges show potential as signals with which to monitor the condition of these assets.