And for those who haven't looked on the map, Pullman, Washington is in the middle of the Palouse country, the richest wheat land in the world. Most definitely rural in nature. You don't have to go far to see how power is provided to a farm. Don's a lucky man living there. Oh yeah, I'm biased. High school and college there.
Ghery S. Pettit From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, December 11, 2007 1:12 PM To: [email protected] Subject: RE: stray voltage ??? 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] CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. 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