LADWP is trying to offer reassurance that the plan — while not free of challenge — is the right way to go. Interim General Manager David Hanson told a recent online meeting of a Pacific Palisades community group that fire and power outage risk would be reduced. But he cautioned that underground power isn’t free of issues; outages are less likely and more infrequent because lines are less exposed, but trying to locate and repair a damaged circuit will take longer than doing so in an above-ground system.
“We love undergrounding circuits for their resiliency, however if there is an issue with circuits it takes us longer to restore power so that’s the tradeoff,” he says.
Making the case for its recommendation, the AECOM report emphasizes the reliability and resiliency aspects of underground power. It presents real-world cases showing that “buried systems suffer far fewer and shorter outages, boosting average reliability metrics.” Additionally, underground lines greatly reduce vulnerability to extreme weather and wildfires “by preventing initial ignition” and avoiding storm damage. To overcome some of the construction and accessibility problems inherent to undergrounding, the report suggests building in extra conduit capacity; trenchless excavation; cable-health monitoring; and remote conduit vault sensors.
The Los Angeles effort might end up being closely watched as more utilities and their construction and maintenance contractors contemplate expansion of undergrounding initiatives.
A recent Burns & McDonnell whitepaper, “The Durability of Underground Transmission and the Future of the Grid,” asserts the tactic will gain more traction as its benefits are proven. But a major obstacle is the challenge of making it as accessible and serviceable as overhead transmission and distribution.
“High-voltage underground transmission operates within a significantly less developed support ecosystem,” writes author Bob Hobson, an associate technical consultant with the firm. “The number of certified high-voltage cable jointers is limited, the pool of specialized installation and repair contractors is comparatively small, and access to high-voltage testing equipment is constrained. The number of contractors across North America with full capability in high-voltage underground transmission installation and repair is on the order of fewer than 100 firms, compared to many thousands of companies supporting overhead transmission construction and maintenance.”
If that support infrastructure can be developed, Hobson says, underground power delivery, especially of high-voltage direct current, could be deployed more extensively and rapidly.
“As grid demands increase, ROW constraints intensify and system stability becomes more complex under high renewable penetration, underground HVDC is positioned to become an increasingly important component of transmission expansion.” Hobson says. “Realizing this potential will require deliberate investment in supply chains, workforce development and system planning, transforming repair duration from a perceived limitation into a manageable and predictable aspect of system design.”
