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Separately Derived Systems-GES #141
12/09/00 02:53 PM
12/09/00 02:53 PM
Scott35  Offline
OP
Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
This is a carryover from an old thread in a forum, but it should get some thinking started.

Looking for pros and cons in your own opinion and what you feel is NEC related, to a common grounding "Grid" approach.

This would be an interconnection to all grounding electrode systems incororated on a given site.

Reason for it would be all systems will be at the same potential at their grounding point for services and Transformers. This does not include service feeders from utility Transformers. Only from the main service section - outwards.

The goals are to have minimal ground fault Impedances, low [hopefully no] ground loop currents and more secure bonding. The problem of primary flash over would be addressed in this method.

I have seen it done at a few existing locations and wondered why it wasn't more common.

Any thoughts, input, comments and questions are welcome.

Scott "S.E.T."


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Work Gear for Electricians and the Trades
Re: Separately Derived Systems-GES #142
12/10/00 08:21 AM
12/10/00 08:21 AM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,360
I agree....the last installation I did I simply utilized fundamental concepts, more grounding is better than less grounding, and closer grounding is better than further away.
As simplistic as this sounds, it's the gist of the good book's art 250

Re: Separately Derived Systems-GES #143
12/10/00 05:54 PM
12/10/00 05:54 PM
B
Bennie R. Palmer  Offline
Member
Joined: Nov 2000
Posts: 72
Milwaukie, OR 97267 USA
I have made reference to some of my past experience before. I have worked in areas that are at the extreme ends of the geological, and climatic spectrum.
I have worked at the highest and lowest temperature locations on earth. I have probably experienced the extremes of ability to connect a conductor to the earth.
The coral reefs of the South Pacific, presented a variable resistance connection, dependant on the rise and fall of the ocean tide.
The ice cap at the South Pole was a two mile thick insulator. I did not drive ground rods.
The sand of the Sahara Desert, in Libya, was a silicon material that was essentially an insulator.
At a communication, radar site, in Arizona we hit a copper vein, very good connection, and low resistance.
Grounding has to be addressed, with different methods, in different areas. The need will change, according to the systems, and conditions. It is hard to design one procedure to fit all.

Re: Separately Derived Systems-GES #144
12/10/00 09:23 PM
12/10/00 09:23 PM
Scott35  Offline
OP
Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
Thanks to "Sparky" and Bennie for the input. I started this thread to get various ideas from others and to bring up some things that weren't thought of.

Bennie;
I am building on the topic that we had going in the old Holt forum. To me, it was prematurely cut short. It also brought grounding techniques to the attention of others [was apparent from their input].

Would like to get as many of these types of threads going in this forum as possible, since it will have a large amount of Contractors and trades persons visiting.

Any input is great.

BTW: I will try making a 1 line drawing to attach in a message. It can describe the grid method's connections so the consept is more understandable.

Scott "S.E.T."


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Separately Derived Systems-GES #145
12/11/00 11:13 AM
12/11/00 11:13 AM
R
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
When all of the rules in Art 250 are applied, we do have a common grounding grid, but we have to remember what it is that we are trying to do. The connection to ground is not important in clearing system faults, the important connection for fault clearing is the main bonding jumper that ties our equipment grounds to the grounded conductor. When installing a SDS we have an equipment grounding conductor on the primary feed that will be connected to the transformer. We will also be connecting our secondary equipment grounds and secondary grounding electrode system together here. This is where the we get into a common grounding grid type installation. The code is however very clear that where ever possible that the secondary grounding electrode system be as close as possible to the SDS.
Don(resqcapt19)


Don(resqcapt19)
Re: Separately Derived Systems-GES #146
12/15/00 12:01 AM
12/15/00 12:01 AM
Scott35  Offline
OP
Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
A common grid approach will have benifits towards the reduction in equipment damage from a coil blow out/over from the Primary to the Secondary.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Re: Separately Derived Systems-GES #147
12/17/00 06:12 PM
12/17/00 06:12 PM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,360
I guess it's a big concern, one of our local inspectors say's there may be a day when we have to prove 25 ohms or less, maybe with one of those "grounding" meters, which I guess I'll be looking into.....I haven't used one yet...any of you???? any good choices on makes/ models???

Re: Separately Derived Systems-GES #148
12/17/00 06:26 PM
12/17/00 06:26 PM
G
gpowellpec  Offline
Member
Joined: Dec 2000
Posts: 127
Irving, Tx USA
Go to http://www.avointl.com/products/groundtster/index.html. That is Biddle and Megger products. The site also explains the theory of earth and ground testing

Re: Separately Derived Systems-GES #149
12/17/00 06:33 PM
12/17/00 06:33 PM
G
gpowellpec  Offline
Member
Joined: Dec 2000
Posts: 127
Irving, Tx USA
Sparky, when I tried to go to the page I posted from the posting it showed up as a download. Just go to http://www.avointl.com/. Then in the GO TO section click Products, then choose Earth/ground resistance Testers.

Re: Separately Derived Systems-GES #150
12/17/00 09:40 PM
12/17/00 09:40 PM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,360
Thanks, that's a definite bookmark, it seems there are testers that actually test the soil, then there are "loop" testers, as well as those that clamp-on the grounding electrode like an amprobe. I've signed up for their on-line newsletter......maybe i'll learn something new!


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