stabilize the voltage

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jwelectric

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I did a search but couldn?t find anything that would help me answer this question. Any comments would be appreciated.

What does this mean in 250.4(A)(1), ?and that will stabilize the voltage to earth during normal operation.??

How is the voltage stabilized?
 
iwire

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IMO they mean the difference of potential between the grounded conductor and the earth will be stabilized.

That said I do not see how that is possible considering our connection to earth is not like a bolted fault but more like a connection to a variable resister.
 
Rockyd

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I'm voting the grounding system is much like shorting a capacitor. Just that the plates are a little bigger than we care to think about!
 
iwire

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Rockyd said:
I'm voting the grounding system is much like shorting a capacitor. Just that the plates are a little bigger than we care to think about!
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Is it not a given that under normal conditions the grounding conductor would be the same potential as the earth?
 
raider1

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iwire said:
IMO they mean the difference of potential between the grounded conductor and the earth will be stabilized.

That said I do not see how that is possible considering our connection to earth is not like a bolted fault but more like a connection to a variable resister.
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I agree with Bob.

This has been my understanding of "stabilizing the voltage to earth".

Chris
 
wbalsam1

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jwelectric said:
I did a search but couldn?t find anything that would help me answer this question. Any comments would be appreciated.

What does this mean in 250.4(A)(1), ?and that will stabilize the voltage to earth during normal operation.??

How is the voltage stabilized?
Click to expand...

I think it's intention is directed at ensuring adequate earthing acting to limit the uncontrolled flow of stray current as a result of the Poco's primary to secondary neutral connection.
 
tom baker

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On an ugrounded 480V system a ground fault will result in a capacitive charge, discharge event which can lead to a ringing voltage up to 2200 volts. There used to be a lot of motor failures with ungrounded systems due to the windings being the weakest point.
So you question answer may be related to the above. The CMP for the 08 changes had an excellent commentary on why ground and why bond where they were discussing some global changes. I don't have those here to post.
 
Rockyd

Rockyd

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Per the OP -How is the voltage stabilized? Long answer short via the GEC. For the whole picture as to how that happens, reading the whole post-

Is it not a given that under normal conditions the grounding conductor would be the same potential as the earth?
Click to expand...

I agree with Bob for the most part. However, we have funny things happen in the world. Where there is opportunity for charges to build on oposite sides of the "plates", grounding insures that there is "zero potential" between the plates, based on the principles laid out in 250.4(A)(1) It's about incidental contact of high voltages. I consider grounding, and bonding two seperate, but related, issues.

In 250.24(A)(2) and In 250.24(A)(3) the BIG difference is that in (3) Shall be connected to earth so as to limit the voltage to ground on these materials VS shall be connected together and to the electrical supply source in a manner that establishes an effective ground fault current path.

In 250.24(A)(2) is to drain (limit) into the earth (via the GEC per 250.24(D)), to balance (create zero potential) any voltage imposed per (A)(1).

In 250.24(A)(3) Is normally to interrupt the OCPD to stop current flow to protect life or property.
 
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