RE: grounding question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>


Hello,
When I moved My electrical service, I was required to ground to the copper
cold water pipe as well as a 8' ground rod. A precursory look up front and
sure enough someone cut the metal pipe going out to the main and replaced it
with plastic.

Needless to say I layed a several feet of copper instead. This could be a
real danger if at least a single ground was not in tack. Ventura Co Ca.

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Friday, October 13, 2006 4:04 PM
To: tesla@xxxxxxxxxx
Subject: Re: grounding question

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 10:45 AM 10/13/2006, you wrote:
>Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
>Hi Jim,
>
>See interspersed comments.
>
>>Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>>
>>At 10:15 PM 10/10/2006, Tesla list wrote:
>>>Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>>>
>>>Your post is very interesting.  Our house also has the breaker
>>>panel grounded to the copper pipe bringing water into the
>>>house.  An electrical contractor for our area says that this
>>>connection is no longer done and instead the breaker panel is
>>>grounded via a rod pounded into the ground at the breaker
>>>panel.  Seems like a step back according to your measurements. I
>>>wonder if the reason for the change has to do with electrolysis of
>>>the copper pipe.
>
>>Nope.. has to do with the fact that water mains are not always
>>metal any more.  Plastic is more and more common.
>
>OK.  Good to know.
>
>
>
>
>
>>>   Anyway, if a grounding rod is good enough for the breaker panel
>>> then why not good enough for a TC RF ground.
>>
>>
>>Lots of reasons.  the breaker panel ground is designed for line
>>frequency grounding, primarily for human life safety....
>
>I understand the safety reasons.  The question is: how is a breaker
>panel that is grounded via a rod in the ground any more safe than a
>TC ground that also is a rod in the ground other than the
>frequencies are different.  Could it be that the heavy guage service
>neutral that comes to the house is also grounded at the distribution
>point and that is what really provides the line frequency ground,
>and the rod in the ground at the breaker panel is more for RF grounding???.

No, more to deal with the possibility of break in the neutral in the
service drop, and to account for voltage drop in the service drop
neutral, so the neutral (in the house) isn't something other than "ground".

The service entrance ground also serves as a common tie point for
other grounding systems (telephone and cable TV, notably), so you
don't get voltage differences between the chassis of a piece of
equipment (connected to ground wire ground) and the shield of the antenna
coax.


>>>The RF choke between RF ground and safety ground is probably fine
>>>for the fundamental RF (say 100KHz), however if a secondary strike
>>>hits an object that is earth grounded, the RF choke may do little
>>>to keep the return current out of the house wiring.
>>
>>I would think that in a "RF isolated" system (such as contemplated
>>here) you'd really, really want to avoid strikes to things NOT
>>connected to the RF ground; i.e. you want strikes ONLY to the
>>counterpoise, and if you have a "grounded" electrode to draw
>>strikes, you want it connected to the counterpoise, not "earth ground".
>
>YES,  and this is why I dont like the RF choke between the mains
>ground and RF ground.  Such a strike could arc over the choke and
>have transient currents in the mains ground.  Of course, without the
>RF choke, the RF ground is not considered safe and anything
>connected to it should be considered in the KEEP OUT zone while operating.


Right.. with the counterpoise ungrounded, it's really no different
than the topload on the "other" coil in a bipolar pair.  The problem
is that one likes to have some connection between the HV transformer
secondary and the core (to limit the voltage across the dielectric in
the transformer, especially in the event of a short (or other low
impedance path.. from a spark or streamer))