Justifying the proactive replacement of cable

Many utilities have aging underground cable systems that are failing at an increasing rate. Unfortunately, aggressive underground cable replacement programs are often difficult to justify since it is difficult to know whether any specific cable section will fail in the near future. This paper presents a simulation based methodology to justify a proactive cable replacement program. Its application at a large US utility is demonstrated. This methodology involves the sampling of representative circuits, the development of cable failure rate models and system reliability models that can track expected reliability over a twenty year period, and the sequential simulation of system reliability. Three proactive cable replacement scenarios are examined and their economics are compared, considering the integration of other reliability improvement projects.