More than you want to know about pole pig's

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Don Murray <don@xxxxxxxxxxxxxxx>

First some quotes;

Additive polarity is standard for all 
single-phase distribution transformers 200 KVA 
and below having high-voltage ratings of  9000 volts and below.
Subtractive polarity is standard for all 
single-phase distribution transformers above 200 
KVA  irrespective of voltage rating.
Subtractive polarity is standard for all 
single-phase transformers 200 KVA and below 
having high-voltage ratings above 9000 volts.

Pg. 15-15

Distribution Transformers Tapped 
Windings.  Windings of distribution transformers 
can be manufactured with various taps to broaden 
the range of primary voltages suitable for a 
given installation. The standard taps available 
are on the primary winding of the 
transformer  and are designed to provide 
variations in the number of winding turns in 
steps of  2 ½  percent of the rated voltage. The 
distribution transformers may be designed with 
four 2 ½ percent above rated voltage, two 2 ½ 
percent above and two 2 ½ percent below rated 
voltage, or four 2 ½ percent taps below rate voltage.

Pg. 15-16

The Lineman?s and Cableman?s Handbook, Eighth 
Edition, 1992, Kurtz and Shoemaker, McGraw-Hill, ISBN 0-07-035695-5


Where I work we have 4160/2400 - 12000/6930 - 
20800/12000 volt primary systems. We stock a lot 
of 12KV pots that can be used in the 12&21KV.
When we cut over an area from 4KV to 12 or 21KV, 
we use 4X12KV pots. When all the transformers on 
a circuit are changed to 4X12KV, we drop the 4KV 
feed. We switch all the 4X12 transformers to 12KV and pick up the new feed.
A 4X12KV transformer has a switch on the side, 
just like a 7200/14400, but it is paralleling 3 coils.

I hope this helps.

Don