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‘Hardening’ Power Lines
He said typical elements of a “storm hardening tool kit” include: stronger poles, storm guying, push braces, pole class uprating, shorter spans, smaller conductor sizes, fewer attachments, increased vegetation management -- and undergrounding.
Placing power cable underground is not new to the electrical industry. In fact, two of the first compact horizontal directional drills sold went to a Georgia electrical utility to replace aging service lines. For decades, power companies have served new developments with underground cable, and office parks, educational institutions, and government facilities have limited or no aerial infrastructure. Undergrounding used in a hardening program usually is in older neighborhoods most susceptible to damage from high winds and ice.
“Underground conversion,” said Brown “is best coordinated with new construction and with relocations. For example, a roadway widening may require the relocation of overhead lines. At this time, a utility can consider whether the incremental cost of underground conversion is warranted based on hardening and aesthetic benefits.”
For utilities in areas subject to extreme weather, Brown said the best practice is to develop a storm-hardening roadmap.
“This,” he said, “is a multi-year plan that gradually hardens the system in a targeted and cost-effective manner. A typical roadmap will identify and harden certain critical poles, upgrade to Grade B construction in certain cases, and address critical customers such as hospitals and police stations. The addition cost of undergrounding can typically only be justified by aesthetic considerations.”
To date, he added, the most proactive states with regards to hardening are Florida and Texas, due to their high exposure to hurricanes.
Power utilities and regulators in states affected by the severe winter of 2009-2010 surely are evaluating hardening options now.
“Achieving the proper level of infrastructure performance during major storms at the lowest possible cost is a challenging task, but will increasingly be demanded of utilities by their regulators and customers,” concluded Brown.
Quanta Technology is an independent consulting arm of Quanta Services which provides business and technical expertise to energy utilities and industry and assists in deploying strategic and practical solutions to improve their business performance.
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