Isolated Ground

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rochaconstruct

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We are installing a screen room for pulse power experimentation in an existing building, they are asking for an isolated ground from the transformer to feed the screen room. How do you isolate the ground and maintain a safe installation without bonding the TX. Doesn't that make the grounds and bonds all equal potential (as it should)?
 
Re: Isolated Ground

From the secondary, you will run your phase conductors, a neutral if required for single phase loads, a standard equipment ground conductor and an insulated "isolated ground" conductor to the panelboard.
At the secondary of the transformer, you will have the Xo (wye secondary), equipment ground conductor and isolated ground conductor, bonded together. At the panelboard, you will keep the equipment ground conductor and isolated ground conductor, electrically isolated from each other.

http://www.mikeholt.com/documents/grounding/pdf/isolatedground.pdf

[ December 10, 2005, 11:43 AM: Message edited by: ron ]
 
Re: Isolated Ground

I understand a normal isolated ground system. There is a concern that the pulse power experiments could induce or tranmit noise in to the existing grid and create problems. Is this a valid concern?
 
Re: Isolated Ground

250.130 (A) says that the equipment ground has to be bonded to the neutral at the service. The isolated ground can only stay isolated to this point.
 
Re: Isolated Ground

During everyday operations, the isolated ground should be carrying the same amount of current as the equipment ground, 0. What noise would be injected onto the ground conductors due to the load during normal operations?
IG circuits are usually specified when the designer of the load equipment wants to use the ground as a reference in some fashion. How does the equipment work that brings this concern?
 
Re: Isolated Ground

Are you suggestion the building service or the seperatly derived system feeding the screen room?
The experiment has very rapidly expanding and colapsing electrical fields that create a great deal of RF (hence the screen room). The conductors are isolated through the transformer the only common point is the ground/bond.
 
Re: Isolated Ground

250.130 Equipment Grounding Conductor Connections.
Equipment grounding conductor connections at the source of
separately derived systems shall be made in accordance with
250.30(A)(1).

250.30 Grounding Separately Derived Alternating-
Current Systems.
(A) Grounded Systems. A separately derived ac system
that is grounded shall comply with 250.30(A)(1) through
(A)(8). A grounding connection shall not be made to any
grounded circuit conductor on the load side of the point of
grounding of the separately derived system except as otherwise
permitted in this article.

I say at either the transformer, or the first disconnect after the transformer. Basicly this is treated as if it were new service.
 
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