Re: Grounding HV side of a pig (fwd)

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Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 23 May 2007 17:36:15 -0500
From: Bert Hickman <bert.hickman@xxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Grounding HV side of a pig (fwd)

Stan and all,

It turns out that it doesn't really matter which bushing you ground on a 
two-horned distribution transformer. These transformers are designed to 
be connected from phase-to-phase in a delta connection. Since incoming 
transients can occur on either phase, the transformer's BIL (Basic 
lightning Impulse insulation Level) rating (of at least 95 kV) applies 
for either HV input. You can ground either with impunity.

BTW, if you pull the lid on YOUR pig, you'll find that NEITHER HV lead 
is closest to the core. This is apparently true for either "core" or 
"shell" type oil immersed distribution transformers. To understand this 
better, refer to pages 15.7 and 15.8 in the following section (taken 
from Chapter 15 of "The Lineman's and Cableman's Handbook", 11th edition 
by Thomas Shoemaker and James E. Mack, 2006, ISBN 0071467890). McGraw 
Hill conveniently allows you to download this chapter for inspection:
http://www.mhprofessional.com/downloads/engineering/PDFs/0071467890_Shoemaker/Shoemaker_CH15.pdf

Hope this helped,

Bert
-- 
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Tesla list wrote:
> Original poster: List moderator <mod1@xxxxxxxxxx>
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Wed, 23 May 2007 08:16:59 -0500
> From: Stan <wsmg@xxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Grounding HV side of a pig
> 
> Hey all,
> 
> Mike Hardy(email is screwed-up) wants to ground 1 leg  of the HV side of 
> his 2 horned 10kva pig. Is there a way to determine which horn is the 
> lead closest to the core other then opening it up?
> 
> Thanks,
> Stan
> 
> ps, will be coiling this weekend in Waupaca, WI and firing up Sparky 
> Matic if anyone is going to be in the area. Contact me off list for details.
> http://www.ispdial.com/SkyXPRess_net/MyHomePage/config.cfm?kName=wsmg      
> click on my pics
> 
> 
> 
>