While it sounds like a good idea to go to fully underground power lines, in reality it isn’t such a workable idea. Remember, power companies are in
the business of making money. It it was cheaper in the long run, they would have went to underground lines long ago.
There is many problems with underground lines that make them unreliable in their own right. As many industry people have studied and found out. The
number of power outages is less with underground systems. But the length of the outages is much longer. And the number of outages goes up
exponentially as the system ages.
Underground lines can not be installed where it floods at any time. If it floods, even for a short time, it may take weeks to get power back. It may
require changing large portions of equipment that was submerged. There is underground installation equipment that is rated for submergence. But the
actual reliability of that equipment when it’s actually submerged is hit and miss at best. And that rating is only for short time submergence. If
left underwater long enough, then it will fail.
Underground lines age badly. Ceramic insulators on overhead lines have almost an unlimited life. Poles have 40 to 100 years life expectancy depending
on climate. The insulation used in underground cables has a very limited life. Current usable life is about 20 years. After that, all the underground
lines need to be replaced. If you don’t, then the system will become so prone to random failure that it will not be usable.
Just because you have underground lines, doesn’t mean you can have trees on the right of way. The right of way still needs to be constantly cleared
of anything that puts down deep roots. Tree roots will grow around the line and stretch it, causing failure. And when a tree gets blown down, it will
rip the line out of the ground.
And the thing that complicates all of that. Underground power lines make it hard to find faults. You have to separate the line into its smallest
segments to find out which one is faulted. It can take days to localize some faults. And repair sometimes takes weeks. In the mean time power has to
routed around the fault which often entails installation of temporary overhead lines, or insulated cables ran along the top of the ground until the
failed line can be dug up and replaced. In an aboveground system, a simple visual check will usually locate the problem 99% of the time. Fixes are
usually finished with an hour or less of bucket time.
There is several small towns that are experiencing a lot of the aging problems now. They are some of the first ones that went to underground lines
around 20 to 25 years ago. The lines are done past their usable lifespan. The power outage problems are getting so bad in the areas that some of them
have tried to sue the power company for negligence. The problem is, the very people that are suing are the ones that demanded that the town go to all
underground utilities 20+ years ago. And they don’t want to fork over the required cash to completely replace the underground lines. They are trying
to blame the power company for a condition they caused. And more importantly, they are trying to force the electric company (and all the rest of the
rate payers) to foot the bill for the replacement, so they don’t have to directly pay for the whole operation.
Some of the towns finally seen the error of their ways and have went BACK to overhead lines because they realized the cost of replacing the
underground lines every 20 years was totally intolerable.
Some of the newer underground cable coming off the production line has a projected life of up to 30+ years but that is unproven at this point.
Short sections, like is often used from an overhead line, to the pad mount transformer behind a house, or building, can last up to 30 to 40 years in
some cases, but the odds of it’s failure grow exponentially past 20 years. It makes sense to leave it in place until failure when it’s failure
will not affect the larger system as a whole. But when that line is the mainline which means complete system outage when there is a failure at any
point along the system, then the entire line will have to be replaced when it reaches that point, or the downtime of the system will be more than
it’s uptime. And things will only go down from there.
That is the irony I see in people calling for underground lines so they won’t be bothered by hurricanes. Those very hurricanes, and the flooding
that is associated with them is why it’s impossible to use underground lines. The cost of troubleshooting the flooded underground lines and
replacing the failed parts will take longer, and cost more than the complete replacement of the overhead lines in question every time a storm comes
edit on 3-10-2012 by Mr Tranny because: (no reason given)