Can anybody speak to the current best practices around running underground power lines? I see these types of articles about above-ground distribution systems from time-to-time, particularly in California. I feel lucky that my area has underground power, but that was installed back in the 1980s. Would it be prohibitively expensive for Boulder’s utility provider to move to underground distribution? I can’t help but think it could be worth the cost to reduce wildfire risk and offer more reliable service.

Think of it like this: overhead power lines require you to dig a 5-7’ deep hole that’s 2’ in diameter every 90’. Underground power supplied through cable requires you to bury the cable minimum 3’ in the ground in rigid ductwork the entire 90’. Any time that cable runs under a roadway that ductwork needs to be encased in concrete. In urban and semi urban areas you also compete with other buried infrastructure for space - sewer, city/municipal infrastructure, gas, electrical transmission, etc.

While underground distribution systems are less prone to interruption from bad weather it depends on the circuit design. If the underground portion of the circuit is fed from overhead power lines coming from the distribution substation you will still experience interruptions from faults on the overhead. These faults can also occur on overhead transmission circuits (the lines feeding the distribution substations and/or very large industrial customers).

Underground distribution comes at a cost premium compared to overhead distribution. It’s akin to the cost of building a picket fence vs installing a geothermal heating system for your home. This is why new sub divisions will commonly have underground cable installed as the entire neighborhood is being constructed - there’s no need to retrofit underground cable into an existing area and so the costs are lower and borne upfront.

It’s more cost effective for them to turn the power off as a storm rolls through, patrol, make repairs and reenergize then to move everything underground. Lost revenue during that period is a small fraction of the cost of taking an existing grid and rebuilding it underground. This is especially true for transmission circuits that are strung between steel towers over enormous distances.

Boulder County is working on utility undergrounding, https://bouldercolorado.gov/services/utility-undergrounding, and in particular they are working on undergrounding at Chautauqua, https://bouldercolorado.gov/news/undergrounding-chautauqua, which is next door to the NIST facility.

1/3-1/2 of the cost of the electricity we pay is distribution.

Some of it is physical infrastructure (transformers, wire, poles), but a lot of it is labor.

Labor is expensive in US. It’s a lot of labor to do, plus they’ll likely need regulatory approval, buying out land, working through easements.

At the same time you have people screaming about how expensive energy is.

Furthermore they have higher priorities, replacing ancient aging infrastructure that’s crumbling and being put on higher load every day.

Its very hard to repair and keep track of underground.

https://practical.engineering/blog/2021/9/16/repairing-under...