Re: Pig setup help.

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

Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 

Hi Bart, John and others,

This issue of whether to ground the transformer case (whether it be a pig or
NST) to mains ground or dedicated RF ground seems to be a reoccuring
question that I think has no right or wrong.  I know there are opinions on
both sides and valid ones.  Each solution has its benefits and problems and
how one treats this issue depends on how they define their system.  The
following are the benefits and problems as I see them:

Transformer grounded to mains ground (green wire):

Benefit:  transformer fault (like primary to case short or secondary to case
short) may draw excessive current and blow breaker (note that the balast for
a PIG or PT may not allow this to happen unless ground fault protection is
used).  Case is safer, however one still has the bushings that can kill.

Disadvantage:  A strike to the TC primary (transformer secondary) could
flashover to the case and thus the mains ground and kill sensitive
components (TV, stereo, etc) also plugged into the mains.

Transformer grounded to dedicated earth ground (aka RF ground):

Benefit: a strike to TC primary that results in flashover to transformer
case will directly return to the secondary ground and not contaminate mains
power.

Disadvantage:  transformer fault could result in a HOT case and no blowing
of the breakers if the dedicated earth ground is not adequate.  If adequate,
the protection should be just a good as mains ground, but still no
guarantees for the balasted pig or PT unless ground fault protection is
used.

I think one should define danger zones in their system design.  If the
transformer is within the danger zone,  grounding to the dedicated earth
ground is OK.  If outside the danger zone, the transformer should be
grounded to mains ground and the bushings protected from accidental contact.

One persons opinion,
Gerry R


 > Original poster: Bart Anderson <classi6-at-classictesla-dot-com>
 >
 > Hi Randy,
 >
 > Grounding the case to mains ground is for safety. All equipment with
direct
 > feeds should have their case connected to mains ground (this includes the
 > transformer). In the event of a fault, we don't want the case at a
 > potential that could be lethal. Should there be a fault, the mains breaker
 > will trip and remove all power.
 >
 > Take care,
 > Bart
 >
 > Tesla list wrote:
 >
 > >Original poster: "Randy & Lori" <rburney6-at-comcast-dot-net>
 > >Bart,
 > >
 > >Why the "mains" ground? I have read:
 > >2 or 3 RF Grounds
 > >1 Mains Ground
 > >1 Mains OK if filter is used
 > >
 > >Randy
 > >
 > >-----Original Message-----
 > >From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > >Sent: Saturday, March 13, 2004 12:44 AM
 > >To: tesla-at-pupman-dot-com
 > >Subject: Re: Pig setup help.
 > >
 > >Original poster: Bart Anderson <classi6-at-classictesla-dot-com>
 > >
 > >Hi Steve,
 > >
 > >Tesla list wrote:
 > >
 > > >Original poster: "steve" <steve_vance-at-cablelynx-dot-com>
 > > >I have a question for the list. I have a 10 kva pig I'm running
 > > >at 5 kva to power my coil my 6.5 inch coil. I was reading the archives
 > > >and came across a post about running one of the hv bushings and
 > > >the can to earth ground. Can't find enough information to convince me
 > > >that I fully understand how to do this safely. Someone correct me if
 > >I'm wrong
 > > >on this.... I run one of the hv leads to the can, ground the can to
 > >earth, run
 > > >the other hv lead to one side of the tank circuit, and the other side
 > >of
 > > >the tank
 > > >goes to the rf ground? Or does it need it's own ground rod?
 > > >
 > > >Thanks for any help.
 > > >
 > > >Steve Vance
 > >
 > >You've got it right. The case should be tied to "mains" ground. Then,
 > >240
 > >to the 2 low voltage bushings.
 > >
 > >To bring the inner primary at the same potential (RF ground) as the
 > >bottom
 > >of the secondary, tie one side of the hv terminal to RF ground and the
 > >other end to the tank. The hv terminal to RF ground does not need it's
 > >own
 > >ground. RF ground is where the connection is.
 > >
 > >Take care,
 > >Bart
 > >
 > >
 > >
 > >
 >
 >
 >