A Jolt of New Life for Old Cable
In this installment of What Works, cable rejuvenation gives a Missouri electric company more bang for its buck.
Between a rock and a hard place: That’s where Joplin, Mo.-based Empire District Electric Co. found itself with its network of aging underground cable.
Most of Empire’s cable was installed in the 1970s, and about a decade ago, Empire c which serves around 215,000 customers in Missouri, Kansas, Arkansas and Oklahoma – faced a rising number of power outages. The lack of reliability frustrated residential and commerical customers, but outright replacement of the more than 17,000 feet of cable that needed initial attention was exceedingly expensive: Estimates were as high as $100 per square foot.
“Our terrain is very rocky, and we bedded the cable with agricultural limestone,” explains Wes Robertson, manager of line operations at Empire Electric. The limestone works its way into the insulation over time, he adds, making it extremely difficult to dig up the cable. In addition, whenever cable is replaced, a second trench has to be dug in order to install the new cable.
“We knew we were going to have to do something,” Robertson says – but replacement wasn’t it. Empire turned instead to cable rejuvenation, a process by which fluid is injected into cable segments, where it permeates the insulation and works to restore cable to full dielectric strength.
Robertson admits that he and the Empire team were skeptical at first about the efficacy of rejuvenation, appealing though the cost savings relative to cable replacement were. “It was hard to believe the process could be done with the cables energized,” Robertson says. But two rounds of injection, treating about 30,000 feet of cable, produced impressive results. Cable failures declined markedly and quickly. Certain residential subdivisions that had experienced as many as 80 cable failures a year saw their annual failures plummet to 10 to 12.