My reference is the construction manual of the local power utility, in
possession of a co-worker who is a former employee of said utility.
I checked out the construction method specifically. I was riding down a
local road, and noticed the utility poles were strung with three low
voltage wires (120-0-120) feeding the houses, and ONE high voltage wire,
with transformers interposed at every third house or so. I looked more
closely at transformer wiring, and noticed to my surprise that one end of
the transformer primary is tied to neutral on the secondary side. I asked
my co-worker about this, who said that yes this is how it is done, and who
then showed me the construction manual. (The manual also specifies the
periodic grounding of the shared neutral/ground wire).
The transformers are not really autotransformers - the primary connections
both come out through high voltage bushings, and there are no turns sharing
current between input and output. But the two winding do get tied together.
BTW, my company provides protective relays to power utilities, so although
we are not in the business of putting up power distribution systems,
information like this is not unusual to find around here.
Don Borowski
Schweitzer Engineering Labs
Pullman, WA, USA
"Tarver, Peter"
<peter.tarver@SAN
MINA-SCI.COM> To
Sent by: <[email protected]>
[email protected] cc
Subject
12/11/2007 12:38 RE: stray voltage ???
PM
> From: Don Borowski
> Sent: Tuesday, December 11, 2007 11:01 AM
>
> Take the
> simple case of several farms or residences being fed from one
> high-voltage phase, each with its own transformer. In this
> case, there are two wires on the high voltage side. One wire
> is grounded (periodically, by a grounding wire running down
> the pole to a ground rod) and one wire is "hot" at the
> distribution voltage. When a transformer is installed to
> create a service drop, the center tap (neutral) of the
> transformer secondary is tied to the ground wire on the high
> voltage primary side (and also tied to a ground rod).
Do you have a reference for this arrangement, Don? This would tend to make
the arrangement like a collection of autotransformers and is contrary to my
understanding of the US distribution system.
Regards,
Peter L. Tarver, PE
[email protected]
Regards,
Peter L. Tarver, PE
[email protected]
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