Condition monitoring of 11-132 kV cable accessories

The purpose of condition monitoring of cable accessories is to predict failures before they occur. Those accessories which are about to fail (and not cable accessories in good condition) can then be replaced, thereby reducing the incidence of cable accessory failures. Condition monitoring includes both periodic tests (perhaps in accordance with a defined maintenance programme) and continuous on-line monitoring. The costs of any monitoring exercise need to be weighed against the benefits which can be obtained in terms of failure reduction. Frequent periodic testing in accordance with a rigid maintenance programme may not be cost effective. Reliability centred maintenance techniques have been developed which take account of failure modes and mean time between failures in order to achieve the most effective condition monitoring and overall maintenance programmes. These techniques can be applied to condition monitoring of cable joints and terminations in the voltage range 11 to 132 kV. The various methods which can be used to monitor the condition of joints and terminations are considered and include: acoustic emissions, EM probes, optical fibre temperature sensors, discharge mapping, HF current probes, IR thermal imaging cameras, and visual examinations