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Reliability of underground power lines?

N

N9WOS

Jan 1, 1970
0
I was watching one of those discovery channel shows talking about the
crumbling of American infrastructure. One of the things they covered was the
power reliability problems in Deerfield IL. To the point that they sued the
power company. They talked about old power lines being the problem, and
showed pictures of old above ground poles. But I really think they missed
the actual problem with the system in Deerfield.

The primary cause of the outages in Deerfield is the underground part of the
system. Not the aboveground part.

Deerfield is on of those communities that went to the expense of having most
of the wiring put underground in a lot of the developments. It was direct
burial installation. The problem is, it is over 20 years since the power
lines were installed, and they are reaching end of life. The only answer to
fixing it is, you have to completely rip everything out and replace it.

There power company has already replaced several miles of underground line,
but that is just a fraction of what is there. If they do replace all of the
lines, it will keep everything running for about another 20 years, then they
rill have to repeat it all again.

End of life for overhead lines is 50 to 60 years. Some are still in service
long after that in dry areas. The industry is finding out that the end of
life for buried lines seems to be 20 to 25 years.

Some places I had read about were even more depressing. They stated that it
would take them 20 years to replace all the lines. Which, given the 20 year
lifespan, means that when they finish, they will instantly start back at the
beginning again. Or basically, continuous perpetual replacement of the power
system.

From what I have seen, power companies have seem to accept that fact,
because they are putting the power lines in conduit for most of the newer
installations. That allows them to pull the lines and replace them without
having to dig up the land in-between. But the idea of pulling and replacing
everything every 20 years is not hopeful in regard to power prices. Because
every customer pays for that work with their power bill.

And it will also mean more scheduled outages, because you can't relplace
them while the system is live, so when you pull the wires and replace them,
everyone is out of juice.

And that doesn't help the countless places that have already had their lines
directly buried over the last 20 to 30+ years. All those communities are on
a runaway train headed right for endless power problems, and major
excavation and replacement of their systems.

A lot of the people wanted underground lines so they could have trees
without fighting the power company, but in a round about way, they are going
to have to have those trees removed to replace the underground lines in 20
years. So there is no way to win.

With all the communities pushing for underground lines, are we, as a country
setting are selves up for a lot of power related headaches in the future?
 
I was watching one of those discovery channel shows talking about the
crumbling of American infrastructure. One of the things they covered was the
power reliability problems in Deerfield IL. To the point that they sued the
power company. They talked about old power lines being the problem, and
showed pictures of old above ground poles. But I really think they missed
the actual problem with the system in Deerfield.

The primary cause of the outages in Deerfield is the underground part of the
system. Not the aboveground part.

Deerfield is on of those communities that went to the expense of having most
of the wiring put underground in a lot of the developments. It was direct
burial installation. The problem is, it is over 20 years since the power
lines were installed, and they are reaching end of life. The only answer to
fixing it is, you have to completely rip everything out and replace it.

There power company has already replaced several miles of underground line,
but that is just a fraction of what is there. If they do replace all of the
lines, it will keep everything running for about another 20 years, then they
rill have to repeat it all again.

End of life for overhead lines is 50 to 60 years. Some are still in service
long after that in dry areas. The industry is finding out that the end of
life for buried lines seems to be 20 to 25 years.

Some places I had read about were even more depressing. They stated that it
would take them 20 years to replace all the lines. Which, given the 20 year
lifespan, means that when they finish, they will instantly start back at the
beginning again. Or basically, continuous perpetual replacement of the power
system.

From what I have seen, power companies have seem to accept that fact,
because they are putting the power lines in conduit for most of the newer
installations. That allows them to pull the lines and replace them without
having to dig up the land in-between. But the idea of pulling and replacing
everything every 20 years is not hopeful in regard to power prices. Because
every customer pays for that work with their power bill.


You forget that in Deerfield, as in many areas of the northeast and
much of the rest of North America, wind and ice storms reduce the
lifespan of overhead wires significantly.

Where we have above-ground hydro services, lines come down every
couple of years - and sometimes more than once in a winter - as well
as every 10 years or so in the summer due to high winds knocking down
trees etc.

Where we have underground services and buried transformer vaults
problems start with water infiltration around year 20 - 25.
Where above-ground transformer vaults are used, most are still working
fine after 30 years - and the local utility is replacing the buried
vaults with pad-mount above-ground units.

The added advantage of not having 50,000 starlings sitting on the
wires crapping on everything in range also cannot be ignored.
And it will also mean more scheduled outages, because you can't relplace
them while the system is live, so when you pull the wires and replace them,
everyone is out of juice.

When they replace the underground service wires here in Waterloo
Ontario, a 5 minute switch-over outage is a LONG outage.
And that doesn't help the countless places that have already had their lines
directly buried over the last 20 to 30+ years. All those communities are on
a runaway train headed right for endless power problems, and major
excavation and replacement of their systems.

A lot of the people wanted underground lines so they could have trees
without fighting the power company, but in a round about way, they are going
to have to have those trees removed to replace the underground lines in 20
years. So there is no way to win.

With all the communities pushing for underground lines, are we, as a country
setting are selves up for a lot of power related headaches in the future?

Not nearly as much headaches as with the overhead wires exposed to the
elements, ice, wind, trees,etc - as well as the poles being knocked
down by cars that leave the road for any reason.

I think you are over-analyzing things and coming to faulty
conclusions.
 
A

Another Dave

Jan 1, 1970
0
With all the communities pushing for underground lines, are we, as a country
setting are selves up for a lot of power related headaches in the future?

Here in the UK underground power cables on newly-built housing estates
have been standard for at least 45 years and very probably longer.
They're always conduited but I've never heard of ANY being replaced.

Perhaps climate conditions in the US are more extreme but I don't see
how that could make any difference. Temperatures of -25 degrees Celsius
occur in Britain, though admittedly not often.

Another Dave
 
V

vaughn

Jan 1, 1970
0
N9WOS said:
A lot of the people wanted underground lines so they could have trees without
fighting the power company, but in a round about way, they are going to have
to have those trees removed to replace the underground lines in 20 years. So
there is no way to win.

Only true with direct bury construction. If they do the job correctly the first
time by using conduit, there will be no need to dig new ditches to replace the
lines; so your precious tree can stay in place. Further, the conduits will
reduce (but not prevent) power outages caused by digging accidents. Once you
have dug the trench for the direct bury cable, adding the conduit is a
comparatively small incremental expense.

Vaughn
 
D

Dan Lanciani

Jan 1, 1970
0
| With all the communities pushing for underground lines, are we, as a country
| setting are selves up for a lot of power related headaches in the future?

I replaced the direct burial laterals for a house built in the late 50's in
(IIRC) 2003. The lines were still working but I was upgrading the service
from 100A to 200A. We looked at the wires and I would guess they were good
for another decade, though the insulation was starting to show a little
deterioration. Over the same period the wires on the poles had been broken,
replaced, and otherwise maintained (with requisite power interruption) more
times than I can remember. My new laterals are in conduit and absent some
as yet undiscovered plasticizer incompatibility I expect them to last even
longer. So, it may well depend on local conditions, but if the wires on
the poles are subject to any kind of storm damage I think buried conduit
wins easily.

Dan Lanciani
[email protected]*com
 
N

N9WOS

Jan 1, 1970
0
Another Dave said:
Here in the UK underground power cables on newly-built housing estates
have been standard for at least 45 years and very probably longer. They're
always conduited but I've never heard of ANY being replaced.

Perhaps climate conditions in the US are more extreme but I don't see how
that could make any difference. Temperatures of -25 degrees Celsius occur
in Britain, though admittedly not often.

Another Dave

You are referring to something else entirely.

Most of the street level distribution in the UK is low voltage <600V. low
voltage lines do not have the insulation degradation problem. A large
portion of the medium voltage 600V to 60,000V was installed long before
extruded polyethylene lines existed. They are using fluid filled cables.
Fluid filled cables have proven reliability. I am not talking about those
installation.

I am talking about extruded polyethylene medium voltage cables used in
street level distribution. Extruded dry polyethylene cables were first used
in the 1960's. major reliability/water problems were finally solved and they
finally started seeing widespread use in the 1990's.

Extruded dry polyethylene is the main cable type used in rural/suburban
underground power grids.

The first generation of dry polyethylene installations across the country
are finally reaching the end of life stage. Most of those were installed
using direct burial, because they didn't know the cables would have such a
poor lifespan. That means all the underground systems that have been put in
place the last 20 years are coming up for removal. And they will be removed
the hard way.
 
N

N9WOS

Jan 1, 1970
0
When they replace the underground service wires here in Waterloo
Ontario, a 5 minute switch-over outage is a LONG outage.


Umm...5 minutes... Depends on where you are in relation to the line being
replaced.

If they replace the line, then it means they are replacing it for a reason.
What is that reason? If it is shorted out, then that means that everyone
down stream of that line has been out for... hours? Day?

It will take them a couple hours to find where the trouble spot is. It will
take them a couple hours to verify the cable is dead once they isolate it.
So, four to six hours after the event, you finally know you have to change
it. Do you have that size of cable in stock? Do you have enough? So,
depending on where the power company warehouse is, we are talking 2 hours to
get new cable and hardware to pull it, on scene. Cut ends off old cable, set
up puller, clip end of new cable to old cable, pull, cut and terminal new
ends. An hour or two. Shut the power off to the rest of the neighborhood to
reconnect the isolated section... 5 minutes....

We are talking 10 to 12 hours from lights out to lights on for an
underground cable replacement if it is in a conduit, and requires no
digging. If it does require digging, we are talking a day + of no lights for
the people feed by that line.

That is the general timelines that are given for underground problems around
here in Indiana.
 
N

N9WOS

Jan 1, 1970
0
| With all the communities pushing for underground lines, are we, as a
country
| setting are selves up for a lot of power related headaches in the
future?

I replaced the direct burial laterals for a house built in the late 50's
in
(IIRC) 2003. The lines were still working but I was upgrading the service
from 100A to 200A. We looked at the wires and I would guess they were
good
for another decade, though the insulation was starting to show a little
deterioration. Over the same period the wires on the poles had been
broken,
replaced, and otherwise maintained (with requisite power interruption)
more
times than I can remember. My new laterals are in conduit and absent some
as yet undiscovered plasticizer incompatibility I expect them to last even
longer. So, it may well depend on local conditions, but if the wires on
the poles are subject to any kind of storm damage I think buried conduit
wins easily.

I am not talking about the low voltage 120/240 underground lines that are
after the transformer. I am talking about buried primary lines. 2.4 to
14.4kV that feed pad mounted transformers. They are totally different
animals.

Some neighborhoods have buried low voltage going from poles to the house. I
am talking about the neighborhoods that have the entire system underground.
 
N

N9WOS

Jan 1, 1970
0
Some neighborhoods have buried low voltage going from poles to the house.
The feed to our underground wiring (~35 yearsold) is aerial until it
gets to the subdivision. All the distribution transformers are above
ground (pad mounted). I've not seen the specific area of the
aerial-to-underground transition, but it has to be less than 1/4 mile
away from my house (based on the location of trees downed in a storm 2
weeks ago).



Yea, that is normal fair for around here too.



The local REMC will generally install a maximum of a 1000 feet or so
underground to transformer. What ever the length is on the small spools.
That is what they keep in stock, so, in a worse case scenario; they will
have the stuff on hand to replace it from scratch.



A company pushing newer stuff for mainline usage was trying to sell them on
higher reliability cable, so for grins and giggles they installed about a
quarter mile section feeding one of the major branch circuits. The branch
circuit can be feed from both ends, so if it fails, they can switch it back
to the other side in a mater of hours.



Beyond that, they have a general rule against installing any part of the
mainline underground.



I have about 200 feet of primary cable behind the barn that they ripped out
of a neighbors place down the road. It was only five years old and died a
painful death.



In Bloomington, where they are ripping up and repairing a few intersections,
duke energy is abandoning all the underground sections of line and are going
full overhead. Places that haven't had overhead lines in decades are getting
a line of new poles.
 
Umm...5 minutes... Depends on where you are in relation to the line being
replaced.

If they replace the line, then it means they are replacing it for a reason.
What is that reason? If it is shorted out, then that means that everyone
down stream of that line has been out for... hours? Day?

Nope. When they decide to replace underground cabling here it is
generally PREVENTATIVE. They know a problem is developing, so tnhey
run the new line and switch uit over before catastrophic failures.

There were the odd power outages of up to an hour in some areas after
heavy storms when water got into the subterrainian transformer vaults
- which is what triggered the upgrades.
It will take them a couple hours to find where the trouble spot is. It will
take them a couple hours to verify the cable is dead once they isolate it.
So, four to six hours after the event, you finally know you have to change
it. Do you have that size of cable in stock? Do you have enough? So,
depending on where the power company warehouse is, we are talking 2 hours to
get new cable and hardware to pull it, on scene. Cut ends off old cable, set
up puller, clip end of new cable to old cable, pull, cut and terminal new
ends. An hour or two. Shut the power off to the rest of the neighborhood to
reconnect the isolated section... 5 minutes....

We are talking 10 to 12 hours from lights out to lights on for an
underground cable replacement if it is in a conduit, and requires no
digging. If it does require digging, we are talking a day + of no lights for
the people feed by that line.

Mabee the way they do it in your neck of the woods - but not here. In
our subdivision, they generally located the wet line pretty quickly,
then re-configured the feeds to bypass the bad cable. This sometimes
took an hour or so. The cable replacements themselves have never
caused more than a 5 minute outage for the switch-over - even when
replacing the transformers. My UPS carried the computers through
without a hitch - often the only indication the power had been out at
all through the day was a couple of the clocks were flashing.
That is the general timelines that are given for underground problems around
here in Indiana.
Like I said, here in Waterloo Ontario, MUCH shorter.
 
Only true with direct bury construction. If they do the job correctly the first
time by using conduit, there will be no need to dig new ditches to replace the
lines; so your precious tree can stay in place. Further, the conduits will
reduce (but not prevent) power outages caused by digging accidents. Once you
have dug the trench for the direct bury cable, adding the conduit is a
comparatively small incremental expense.

Vaughn
Up here they don't even trench to install new lines. The conduit
follows the "mole" that theyshoot underground from point to point
(transformer pad to transformer pad location, generally) and is
similar to PVC water pipe that comes on a giant spool
 
J

Josepi

Jan 1, 1970
0
I doubt the boys at Wloo North would do the circuit changeover that fast.

They aren't going to dig up your old service wires without dumping the feed
to the house first. The offending house feed would be out for hours, at
least. If the wires need replacing they would typically be blowing the
transformer fuses anyway, or they wouldn't be there, in the first place.


Many times they can put a long lead jumper from your meter base to a
neighbours to keep your house alive.

In Kitchener they don't get into the submersible compartment until the 8kV
is out. Too many accidents have stopped that crap. I don't think Wloo North
uses too many submersibles for a long time.



Like I said, here in Waterloo Ontario, MUCH shorter.
 
J

Josepi

Jan 1, 1970
0
14kV circuits are typically run in duct banks of conduit, encased in
concrete.

The backyards are done like clare stated in many cases. Waterloo is still
running 2.4kV in backyards until they get rid of their substations. With
concentric neutral, direct burial cables the conduit is not needed and too
costly.



Up here they don't even trench to install new lines. The conduit
follows the "mole" that theyshoot underground from point to point
(transformer pad to transformer pad location, generally) and is
similar to PVC water pipe that comes on a giant spoolOn Sun, 25 Jul 2010
15:44:26 -0400, "vaughn"
 
I doubt the boys at Wloo North would do the circuit changeover that fast.

They aren't going to dig up your old service wires without dumping the feed
to the house first. The offending house feed would be out for hours, at
least. If the wires need replacing they would typically be blowing the
transformer fuses anyway, or they wouldn't be there, in the first place.


Many times they can put a long lead jumper from your meter base to a
neighbours to keep your house alive.

In Kitchener they don't get into the submersible compartment until the 8kV
is out. Too many accidents have stopped that crap. I don't think Wloo North
uses too many submersibles for a long time.



Like I said, here in Waterloo Ontario, MUCH shorter.
House feed was not the subject.
 
14kV circuits are typically run in duct banks of conduit, encased in
concrete.

The backyards are done like clare stated in many cases. Waterloo is still
running 2.4kV in backyards until they get rid of their substations. With
concentric neutral, direct burial cables the conduit is not needed and too
costly.



Up here they don't even trench to install new lines. The conduit
follows the "mole" that theyshoot underground from point to point
(transformer pad to transformer pad location, generally) and is
similar to PVC water pipe that comes on a giant spoolOn Sun, 25 Jul 2010
15:44:26 -0400, "vaughn"
Lincoln Village all the cable is in the boulevard, and they changed
ALL the high voltage undergrounds and ALL the transformer vaults over
the last 2 years. It was virtually all done without a trench. A couple
holes here and there, the rest all done with the "mole" - even accros
(under) streets, driveways, and sidewalks. And there are trees along
all the boulevards.
 
J

Josepi

Jan 1, 1970
0
It definitely has taken off in popularity.

I watched, a few years back, as they pulled five conduit tubes (for fibre
optics later) about 2" diameter, different colours, throught the ground over
200m in a stretch. I was quite impressed as they tunnelled right past the
local high tension station...LOL


Lincoln Village all the cable is in the boulevard, and they changed
ALL the high voltage undergrounds and ALL the transformer vaults over
the last 2 years. It was virtually all done without a trench. A couple
holes here and there, the rest all done with the "mole" - even accros
(under) streets, driveways, and sidewalks. And there are trees along
all the boulevards.
 
J

Josepi

Jan 1, 1970
0
My bad.

Reado error.

I totally agree with your comments concerning high voltage burial. Waterloo
is typically a little more advanced in using new methods than Kitchener, the
museum.

Thanx

House feed was not the subject.
 
E

EXT

Jan 1, 1970
0
A lot of the people wanted underground lines so they could have trees
without fighting the power company, but in a round about way, they are
going to have to have those trees removed to replace the underground lines
in 20 years. So there is no way to win.

Around here often the underground installation companies install natural gas
pipes in a unique way. To install natural gas lines they use an air powered
"torpedo" which will drag a cable underground over about 50 to 100 feet at
a time. This cable is used to pull a cone to enlarge the tunnel and then
drag a plastic gas distribution pipe without tearing up the entire route
allowing them to go under trees. I am sure the same technology can be used
to pull wires or conduit for wires.
 
V

vaughn

Jan 1, 1970
0
EXT said:
Around here often the underground installation companies install natural gas
pipes in a unique way. To install natural gas lines they use an air powered
"torpedo" which will drag a cable underground over about 50 to 100 feet at a
time. This cable is used to pull a cone to enlarge the tunnel and then drag a
plastic gas distribution pipe without tearing up the entire route allowing
them to go under trees. I am sure the same technology can be used to pull
wires or conduit for wires.

The "torpedo" that I have seeen is an unguided device. It is a very useful
device that can indeed be used to install conduit, but it does not have near the
accuracy of directional boring. Also, there is always the chance that it will
go "wild" and not emerge where you expect it to. It can even dive! In that
case, you will have a hell of a mess before you finally manage to dig the
expensive bugger out of the ground.

Vaughn
 
J

Josepi

Jan 1, 1970
0
The later units I have seen around KW used directional controls. I suspect
the vibrators in the head do different planes of vibration to change
directions. The guy driving it has a joystick and some method of feedback to
know where it is going. Not sure how they do the feedback or actually
control it. Like you said the older units could be dangerous and full of
surprises.



The "torpedo" that I have seeen is an unguided device. It is a very useful
device that can indeed be used to install conduit, but it does not have near
the
accuracy of directional boring. Also, there is always the chance that it
will
go "wild" and not emerge where you expect it to. It can even dive! In that
case, you will have a hell of a mess before you finally manage to dig the
expensive bugger out of the ground.

Vaughn
 
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