‘Hardening’ Power Lines

By Jeff Griffin, Senior Editor | July 2010 Vol. 65 No. 7

“Why don’t they just put everything underground?” It’s a question heard repeatedly after major storms knock out vital power and communications services, and one that utilities often were asked after last winter’s storms left hundreds of thousands of Americans without electrical power.

Most everyone considers both electrical and telephone service “essential,” but most storm victims will say they can do without telephones longer than electricity which means no lighting, refrigeration or air conditioning. Homes heated with natural gas or oil require electric-powered fans to distribute heat. Last winter, in parts of the country there were residences and businesses without electrical power for weeks.

Replacing overhead systems with new underground infrastructure seems to make sense to property owners, who don’t recognize that immediately after a major storm is not the time for service providers to put distribution cable underground -- the priority is restoring service, and the only way to do that is to repair and rebuild damaged poles and overhead wires.

In the short term, replacing downed power lines with underground cable is impossible and impractical. In the long run, cost makes it unrealistic to consider replacing all electrical distribution lines with underground cable.

“Multiple studies have shown that broad-based conversion of existing overhead distribution to underground is neither feasible nor cost effective,” said Richard Brown, PhD, P.E., senior vice president at Quanta Technology, a utility infrastructure consulting company based in Raleigh, NC.

“Typically,” Brown continued, “such action would cause rates to double and require a large scaling up of the utility workforce for about 20 years. This does not even consider indirect costs associated with third-party attachments and customer-owned equipment.”

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The cost difference between aerial and underground can vary widely based on a variety of factors, said Brown, but new construction of three-phase primary distribution system underground typically costs from three to five times that of equivalent overhead.

“It is typically much cheaper,” he said “to harden an existing overhead system against extreme weather than to convert to underground. In addition, underground systems also can be susceptible to storm surge damage, and can actually take longer to restore should damage occur.”

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