Phase to “ground”
- Thread starter Djelite
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kwired
Electron manager
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- NE Nebraska
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- EC
If I understand what you are trying to ask, it assumes grounded and ground are the same potential. Though in the real world there often is at least some potential between them when there is current flow on the grounded conductor.
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- retired electrician
Because the definition in Article 100 specifies that point of measurement for the voltage to ground on a grounded system as being between the ungrounded and grounded conductor.
kwired
Electron manager
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- EC
For most of Mike's examples nominal voltage is all that matters.
For troubleshooting or other situations where more precision is needed exact voltages as well as points where measured are more critical.
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- Illinois
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- retired electrician
You have a few days left to submit a Public Input to change the definition. Public Inputs for changes to the 2026 code will be accepted through 5 pm Eastern time, on September 7, 2023.
Thank you sir
I’ve never done it.i’ll look into it
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- Illinois
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- retired electrician
You have to register with an e-mail address. You go to nfpa.org/70 and click on "submit public input for next edition".
You need a very good technical substantiation as to why the change should be made.
Thank you
kwired
Electron manager
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- NE Nebraska
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- EC
I don't think from what was mentioned in OP that he is asking about NEC definitions or changing those but rather what Mike Holt has in some publication that was not specifically mentioned.
It applies to both mike holts illustration and the nec definition. The definition of ground is the earth and neutral is not always grounded or part of ground unless its a corner grounded system Or grounded system. Only when measuring phase to true ground you’ll get voltage close to nominal voltage. Phase to neutral (grounded /grounding as the nec defines it will give you voltage minus vd so it should not be defined as phase to ground. Correct me if im wrong
Consider that if there is voltage drop on the neutral, there is also voltage drop on the associated phase (ungrounded) conductor.
It seems to me that you are trying to arrive at a conclusion that is 1) Ambiguous; and 2) Unnecessary in the context of understanding real-world power systems.
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- Illinois
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- retired electrician
Mike teaches the NEC and will always use the NEC definition for something like this.
My comment to the OP was to his statement that he did not like the definition that I posted from the NEC.
kwired
Electron manager
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- NE Nebraska
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- EC
I don't know the specific document(s) he is referring to, but based on the explanation in OP I am picturing an illustration showing a volt meter connected between a grounded and an ungrounded conductor. Good enough for most general topics. If topic of discussion is a stray voltage type of issue or anything else where one may be concerned with the differential in voltage he most likely would include both grounded conductor and earth ground as well as voltage meter readings between them in the illustration, and pretty much has to to give effective explanation of what is going on in those type of situations
Electromatic
Senior Member
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- Virginia
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I would say it's more the other way around. If, for example, you did not connect the neutral(center of a wye/normally obligated to be grounded) of a transformer secondary to earth, the voltages from each phase to that point would still be the nominal voltage of the secondary. The voltages from each phase to a random spot of earth would be very undefined.
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Yes, Mike often addresses the issue of NEV (neutral to earth voltage) but is very clear what he is talking about when he does that.
Anytime you are talking about "voltage to ground" in the context of the NEC, you have no choice but to take that measurement as specified in the Article 100 definition.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
But Mike's examples in his publications are not NEC, they are his opinion on how to describe, illustrate, etc. whatever topic he is trying to address.
If he has an illustration showing a meter reading between grounded and ungrounded conductor and no additional references to (earth) ground voltages, chances are all that mattered in the discussion was the nominal voltage the items in the illustration would operate at. NEC itself doesn't really have such illustrations that I can think of, and even if the handbook does, it would be in the explanatory material portion which doesn't necessarily comply with NEC style and such and clearly says near front of the book that this content is the opinion of whoever wrote it and not an official NFPA interpretation of the NEC.
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