Showing posts with label electric lines reason over the ground. Show all posts
Showing posts with label electric lines reason over the ground. Show all posts

Tuesday, 14 November 2017

Why aren't power lines in the US burried underground so that everyone doesn't lose power during hurricanes and other natural disasters?


Cost is the major reason why electric lines are not buried.Here are the details:

The first is initial installation. Most underground cable at distribution voltage (4kV to about 35kV but that definition fluctuates) is installed in buried conduit, and basically every construction company can tell you that digging sucks. Even with a geotechnical report, some areas of the country are a total crapshoot as to what you'll find 3' down. In parts of VA it might be the water table, in parts of ID it might be lava rock. Usually the ground is either too soft and the hole/ trench doesn't hold up, or too hard and it takes forever to dig. Either way that means money.

Digging also isn't very pretty, and most places have lots of rules regarding how you dig, when you dig, what you do with the spoils (dirt you dig up) and what you have to do to clean up afterwards. If you dig in the middle of nowhere this isn't bad, but God forbid you're in the rich part of town. Then on top of all this money you spent following the rules you now have to spend another big pile fixing landscaping (ya know that bush you dug up? The fourth one from the end that was almost dead? Yea, that was my great great grandmother's golden bush of infinite happiness! You owe me $5000 for it! No an almost identical bush isn't good enough!).

Not too mention underground conductor is more expensive. The conduit it goes into is an added cost, but it pales in comparison to the price difference between underground wire and what you'd spend on overhead wire for a similar amount of current. Additionally this wire has to hold voltage that is desperately trying to release itself into the surrounding earth, so if you nick it when pulling it in, or damage the insulating jacket in some other way, congratulations you get to pull that wire in again! Because that electricity will arc that gap and the line won't work.

If that happens later on down the road, it's also much more difficult to diagnose and fix. With an overhead line, you can usually tell what's wrong (hint: what parts that should be in the air are now on the ground?) But with underground lines you have to drag out the thumper.

The thumper is a piece of equipment that applies a voltage to a line. The voltage goes higher and higher until it arcs through damaged insulation and makes a thump sound underground. Then a worker has to locate the fault (damaged piece of line) by walking the route of the line and listening for the thump. Now newer equipment is fancy enough to help you get pretty close without much work, but there's still a lot of experience and good luck to finding the fault quickly. By the time you add in the cost of the thumper, the crew's time to actually dig up and fix the line, and the outage time for the customers being fed, you're taking a pretty penny.

Not to mention, mother earth is not kind. If you go to more remote places you can find lines that have been around 60 or 70 years. Not going to find many underground lines that old.
There's also the fact that adding capacity to overhead lines is easier in most cases, but that's a bit too nuanced for this post.

And finally, electricity is pretty easy to move overhead. Water, oil, gas, and sewage are not. In most places the ground where it would make sense to bury power lines is crowded and most of those companies don't want high voltage anywhere near their stuff. Hell they don't even want the pole in the ground because most of the poles are grounded. But any company that will even let you bury near them is going to, at minimum, want an inspector on site while you build, and you get to pay his wages while he's out there. Most companies would rather take you to court than let you build though.
So most of the time, high lines are where it's at!

Edit: All of my experience is in North America. I don't know why Europe manages to get everything underground, but as I mention below I expect its a combination of denser urban areas and government regulation. Some places in the US are experimenting with that, but others probably won't for quite some time.

/u/thekbob linked a great study here: http://www.eei.org/issuesandpolicy/electricreliability/undergrounding/Pages/default.aspx
That goes a lot more in depth about why underground electric utilities are better at some things, and still unlikely to catch on in the states.
Also, I may have given enough information for some really dedicated soul to deduce who I work for. For the record I am not an official spokesperson for any company, any opinions expressed here or in other comments are solely my own and do not reflect the opinions of any other entity.

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