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From: john@newave.UUCP (John A. Weeks III)
Newsgroups: sci.electronics
Subject: Re: Stray Voltage? on 60 Minutes
Message-ID: <746@newave.UUCP>
Date: 11 Apr 91 03:59:49 GMT
References: <3853@uc.msc.umn.edu>
Reply-To: john@newave.mn.org (John A. Weeks III)
Distribution: usa
Organization: NeWave Communications Ltd, Eden Prairie, MN
Lines: 52

In article <3853@uc.msc.umn.edu> dwm@msc.edu (Don Mears) writes:
> Can someone explain what they were talking about on 60 minutes on 4/7
> in the piece on stray voltage from old power lines that caused
> dead and deformed animals, and shocks to people?  These did not look like
> high voltage power lines, just  normal ~10kv distribution lines. 

I did not see the 60 minutes piece, but there are major problems with
stray voltage in Wisconsin on some farms.  What the farmers know is
that milk production and life spans of animals drop and the deformity
rate of calves increases after some electrical change was made.  Some
are related to transmission lines, other cases relate to electrical
wiring problems.  Many cases remain unsolved.

If you have ever seen the inside of a cow barn, you will remember
a lot of pipes running around.  There are piping systems for vacume
(to power the milking equipment), water (for drinking water), milk
(lines to the bulk tank), and pipes to seperate the cows.  Some
barns also have "training wires" (a low strung wire carrying current
that the cow would contact and get zapped on if it tried to go to
the bathroom in the stall--cows are supposed to back up & go in the
gutter, which is lower, thus no zap) and automated feeders.

All of these devices are big electrical conductors.  Most are grounded
only at one point.  Thus, there is the potential for large ground loops
if the metal pieces are not grounded at the same spot.  Any type of
electric current that gets into the system can cause stray voltage
problems.  This current can be natural.  Some folk tales blame the
problems on the rebar rusting in concrete floors.

> The problem must be related to insulator breakdown somewhere or power
> radiated from power lines through the air to other structures.  I don't
> understand why it is not trival to measure.   I don't understand why
> the farmers involved can't circumvent the problem with additional shielding, 
> grounding, or insulation.   I don't understand why replacing the
> just power lines without rerouting them fixes the problem. 

The cases that can be measured are easy to fix.  Usually the voltage is
usually very small, often less than 0.5 volts and as high as 1.75 volts.
But the cases that cannot be measured or isolated are very difficult to
fix.  Wisconsin Public Service and other utilities have programs to help
out farmers that can demonstrate a problem.  The utility companies and some
have spent large sums of money trying to fix these problems, often
unsucessfully.

If you want more information, try writing to one of the power companies
in Wisconsin.  Try Wisconsin Public Service, Dairyland Power Cooperative,
or Wisconsin Power & Light.

-john-

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John A. Weeks III               (612) 942-6969             john@newave.mn.org
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