357 Magnum has a pretty good post about why it isn’t as easy as many people think. There’s a good link and a video illustrating… issues.
The video is about Los Angeles doing a repair on a buried line back in 1989. I missed that when it happened. It took months and millions of dollars.
That system was a big steel pipe, with the 3 phase conductors run through it. The conductors were individually wrapped in layers of paper for insulation, then the pipe was pressurized with oil. The oil acts as a dielectric for additional insulation and heat management.
Watch the video for the details. One thing that wasn’t addressed in the video struck me. They eventually had to drain all the oil out of the ten mile pipe. I see problems.
I’m betting that was the same type of carcinogenic, PCB-ladened oil that used to be used in transformers. Disposing of that oil would have been a HAZMAT nightmare. Been there, done that. Smaller amount, though.
I used to work on troposcatter radios. They used… oh, I think 1,000 pound transformers, and they filled with that oil. And they leaked.
We finally got to replace them with non-PCB transformers, which were smaller, lighter, and more efficient than the old stuff. But cleaning up everything was a nasty cleansuit affair. The old transformers had to be sealed up. Everything we used — suits masks, gloves, wipes, cleaning solution — had to go into sealed barrels. And the barrels’ exterior had to be decontaminated.
You know, what with the PCB exposure, X-rays from the klystrons, and general radiation from spending years living at high altitudes, it’s a wonder I never got cancer. I’m glad troposcater is pretty a thing of the past.
I think oil-type buried power lines are also going the way of the dodo. It looks like the current preferred technique is heavy duty coaxial lines run through separate concrete ducts, with buried canble vaults for splice points. No oil. But it still costs as much as 15 times what overhead lines do.
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