New Life for Aging Cables
Cable Rejuvenation Viable Option for Underground Cable Repair
By Glen Bertini, Novinium
Medium voltage underground cable is designed to be used and not seen. Pad mount electrical transformer boxes containing and connected by underground residential distribution (URD) cable are a ubiquitous sight throughout residential neighborhoods, spaced on average 330 feet apart. Most consumers who live in communities with underground cable are unaware of the jumble of cables that each box comprises, and they rarely think about whether the URD itself is well maintained. Most electric utilities, on the other hand, are constantly responding to aging cable issues and the threats they represent.
Utilities face significant challenges when addressing deteriorating URD conditions. The most common URD reliability issues occur when moisture diffuses into the cable’s dielectric layer, gradually diminishing its insulative properties. This condition is called water treeing because of the tree-shaped structure observed when the degraded cable is viewed microscopically. When the insulation on the cable connecting two transformers degrades to a point of failure, the lights go out in the entire neighborhood.
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