🚀 go-pugleaf

In article <CGJnLH.Iws@csc.ti.com> rbeck@ra.csc.ti.com writes:
>In article <1993Nov15.145144.4940@dale.ksc.nasa.gov>, lrobbins@dale.ksc.nasa.gov (Lloyd Robbins) writes:
>|> According to someone I talked to who used to work for FPL, the price
>|> difference between poles and underground is 10-20 times more expensive 
>|> for underground. (Which I find rather hard to believe, but he was
>|> adamant about it.)

Actually, having had two breaks in overhead cable in front of my house
in the past 8 months, I can believe it...  The first time, a falling
tree limb took out a distribution cable, and knocked out most of my
neighborhood.  I called the emergency number, and power was back up
in less than an hour.  The broken cable was repaired and restrung
live.  The second time, a falling tree branch hit the house, taking
out the power feed to the house in the process.  It was around 3 o'clock
in the morning.  2 guys came out and reinstalled the cable in less
than 45 minutes.  In the rain.  With live cables.  After cutting
away enough of the fallen limb to work around.

I grew up in a neighborhood served by
buried cables.  Any time they had to dig up and fix a cable fault,
power was out for a minimum of an hour, usually several hours.

>There are probably "hidden costs" that we wouldn't think about.  Such
>as conduit for the cables, digging the trenches, stringing the cable
>through the conduit, digging & repairing any streets intersecting the
>right-of-way, etc...  I can see where it would be less costly to erect
>a few towers & string cable than it would be to put everything
>underground.
>
>Then there's the cost of maintaining that installation once it's
>buried.  Any repairs are harder to find and more costly to fix.


I mentioned this topic to a friend of mine, who works in the research
division of a major electric utility.  Specifically, she has been
involved in the testing and characterization of transmission lines
for several years.  Here are her comments.  They do not represent
the official public position of the utility she works for, hence
I am keeping her affiliation and idendity anonymous.

Quoted text (preceded with ">" and text enclosed in brackets ("[]) is mine;
the rest is my friend's.

Please note the distinction between "transmission lines" and
"distribution lines".  Roughly analogous to "interstate expressway"
vs. "highway".

----begin quoted text---

> Anyhow, someone said "well, let's just have them bury it - maybe the
> homeowner's association could split the difference on price".

Out of sight out of mind, eh? While burying distribution lines is common
depite the fact that it's expensive (at least 10x) and somewhat problem 
ridden (plastic cables are easily damaged by water), burying transmission
cables (the only ones that require significant right of way) is
*extremely* expensive, has its own environmental problems and can
be a problem on the system. Cables in general have high capacitance
that severly limits the length that you can put in a stretch (~40 km).
Greater than that and you must go DC (even more expensive, but good
for system stability), or have reactive compensators (expensive and bad
for system stability). Plastic transmission cables are only coming
into being very slowly because of the difficulty with quality control and
worries with utilities' experience with distribution. The current
technology is oil-paper, where the conductor is wrapped in paper and stuck
in a pipe that is filled with high-pressure oil. That oil must be pumped
around, must have reservoirs to deal with expansion due to temperature
change, and is a general pain in the ass. And you think it's easy to
keep miles and miles of oil-filled pipe from leaking?

If people are worried about magnetic fields, they should first get rid of
their electric blankets, hair dryers and toasters. Then the distribution
lines (they carry more current than transmission lines).
--
[Ed.  Note: transmission lines carry more power, but less current, because of
 the high voltage involved (Power = Voltage X Current).  Magnetic fields
 are generated by electrical currents, not by voltage.]
--                                                      Transmission lines
also have lower fields than they used to because they're now transposing 
the outer phases on a dual circuit line (also cuts down on inductance).

Utilities are spending tons of money on studies for this crap and there 
has yet to be anything conclusive. All of the so-called positive studies 
have been discredited for one reason or another. Personally, I would love 
to have a transmission line in my back yard, it would give the dog some 
room to run.

I'd rather not post myself, as no matter how big the disclaimer some jerk
might think that I'm posting for [utility name]. Besides, I haven't looked
up all the numbers lately, and the only thing you can really be sure of in what
I'm saying are the comments about cable technology. I'm currently
working on qualification tests for plastic, transmission class cables.

> I just hate to see these sorts of things go by
> without folks understanding the fine print on the other side of
> the coin....  :)

Usenet brings that quality out in people.

----end quoted text---


Since I'm bothering with this, I'll go ahead and offer to collect and
relay any further comments or questions on the subject, though I
can't guarantee quick turnaround... :')

Disclaimer:  I have no connection to any power generation or transmission
utility, aside from the sockets in my walls.
-- 
Jonathan E. Quist        jeq@lachman.com       Lachman Technology, Incorporated
DoD #094, EGFC #002, KotPP, KotCF '71 CL450-K4 "Gleep"   Naperville, IL
 __       "I love Boris Yeltsin.  He's kind of like Ted Baxter's
 \/   chubby older brother."  - WBEZ (Chicago) personality Aaron Freeman