Analysis of sheath transients in specially bonded cable systems using EMTP

There are many underground cables in electricity transmission and distribution systems. Utilities have to maintain these cables usually at great cost in order to minimise disruption in services due to cable failures. In extreme cases, the cable systems have to be pulled down to check for defects in cable sections and any wear and tear in the cable protection and sheaths. The prohibitive costs of such preventative maintenance procedures has led to the search for alternative means where the costs involved are not quite as high. One option being considered is a monitoring system that can warn on possible failures so that local maintenance action can be taken. Before such a system can be put in place, extensive simulations are required on the practical system to build up a knowledge base of no fault and faulted conditions that can be used by the monitoring system. This paper presents an approach to the analysis of transients in cable sheaths using EMTP. The results show a high potential to develop a monitoring system.