RE: PT Questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "terry oxandale by way of Terry Fritz <twftesla-at-qwest-dot-net>" <toxandale-at-cei-dot-net>

At smaller remote stations (i.e switching stations), the only source of
power for testing, drills, and small electric tools, is the PT. The utility
I worked for used PTs (lower voltage) that had two high voltage terminals,
and we never took them out of the field until they either meggered low, or
failed completely, or needed to been updated. The HV PTs used capacitors
(Capacitive Couple Potential Device) that worked on the priciple of voltage
drop across a series of capacitors. These I would think would be useless as
a power transformer such as is needed with the TC.

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, April 28, 2002 10:57 AM
To: tesla-at-pupman-dot-com
Subject: PT Questions


Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>

Hi,

I have questions about HV Potential/Instrument Transformers of the type some
use to power their TCs:

1) Why are they so "beefy" so that they are at least 1 KVA?  Are they used
to power a few lights or other things as well as a voltmeter that only
requires miniscule power?

2) Are most PT primaries "two-horn" style with neither primary side
grounded?

3) Are typical PTs dry, oil immersed, or potted?

3) Does anyone in the US have one for sale at a reasonable price?  I am
interested in a two-horn ungrounded configuration, 14 KV at around 2-3 KVA
intermittent duty,  120 or 240 volt 60 Hz secondary, preferably dry style.
I prefer an ungrounded HV winding so it can drive a bridge rectifier with
one side grounded.

4) What commercial source has the best deals for them?  T&R?  Austin?

5) Do utility companies take them out of service?  Seems like they would
last forever and not need replacement.

Thanks,
--Steve