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How is Neutral Wire Neutral in Mains Electricity?

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paulca:

--- Quote from: IDEngineer on January 20, 2020, 09:31:45 pm ---Breaker operation is not affected by the earth reference. Even the most recent AFCI/GFCI breakers do not have a connection to earth - only to neutral. And while neutral is bonded to the earth reference at the panel, that is outside the circuit being monitored by the breaker.

--- End quote ---

A quick google (and my own meter box) suggests different.
https://www.google.com/search?q=rcd+functional+earth

sokoloff:
If an AFCI/GFCI breaker is installed in a subpanel, where neutral and ground are not tied together, is the tail on the breaker connected to neutral or to earth? (It’s tied to the neutral bus bar, not to earth.)

paulca:

--- Quote from: sokoloff on January 22, 2020, 02:48:12 pm ---If an AFCI/GFCI breaker is installed in a subpanel, where neutral and ground are not tied together, is the tail on the breaker connected to neutral or to earth? (It’s tied to the neutral bus bar, not to earth.)

--- End quote ---

If that was in response to me.  Mine was in response to the premise that AFCI/GFCI/RCD/RCBO's never have Earth.  This is not the case.  On a small amount of research the UK regulation do not require a functional Earth reference, but many RCD/RCBOs DO have an Earth reference as it allows them to detect somethings in addition to leaked current.  Apparently with a functional earth reference they can still detect leaked current when there is loss of neutral.

IDEngineer:
A few points of clarification:

* RCD's can be breakers or outlets (there are a few other specialized devices out there too, but most people won't encounter them). In the US the term GFCI is much more common, but means the same thing: A device that detects and reacts to an imbalance in current.

* RCBO's are RCD's that also include overcurrent protection. Thus GFCI outlets are RCD's, but GCFI breakers are RCBO's.

* This thread has been discussing breakers, not outlets.

* GFCI outlets (usually) have a separate connection for an earth reference because three-wire appliances expect an earth reference. GFCI breakers typically do not have a (fourth) connection for an earth reference, at least not in the US. The third connection on GFCI breakers is a (usually white) pigtail that is to be connected to neutral, without regard to whether neutral is bonded locally or distantly to an earth reference. A GCFI breaker is therefore designed to function properly with, or without, a bond between neutral and an earth reference.

While digging around on this topic, I ran across this rather interesting tidbit on Eaton's website (they make a lot of electrical devices):


--- Quote ---One of the most misleading statements, but one that seems to be repeated time and again, is that in order to comply with BS EN 61009, RCBOs must have a separate earth connection. This is not true. Certainly, the standard specifies that an RCBO that does have a separate earth connection must behave in a certain way, but nowhere does it state or imply that a separate earth connection is mandatory. In fact, RCBOs are currently available that have no separate earth connection, yet they achieve full compliance with the standard, supported with declaration of conformity documents.
--- End quote ---

...which further reinforces the point that an earth reference is not required for a residual current device to detect an imbalance of current - and by extension, that how the earth reference is obtained will not prevent a GFCI breaker from operating properly.

Hopefully that finally lays to rest the assertion that one type of earth reference is "better" for GFCI's.

Meanwhile, I continue to wait for someone to explain why they feel a copper rod at the other end of 100 feet of wire is somehow a better earth reference than a copper rod within a few feet of the breaker panel. So far, nothing. Quoting the NEC is just hand-waving, since the NEC changes all the time and sometimes contradicts itself with its own changes. What electrical reason makes 100 feet of intermediate wire a better earth reference?

IanB:

--- Quote from: IDEngineer on January 22, 2020, 07:17:57 pm ---Meanwhile, I continue to wait for someone to explain why they feel a copper rod at the other end of 100 feet of wire is somehow a better earth reference than a copper rod within a few feet of the breaker panel. So far, nothing. Quoting the NEC is just hand-waving, since the NEC changes all the time and sometimes contradicts itself with its own changes. What electrical reason makes 100 feet of intermediate wire a better earth reference?

--- End quote ---

For the sake of discussion, let me ask questions.

Suppose the remote building is connected with 100 feet of earth wire back to the main panel in the main building. Now suppose there is a difference in potential between the local terrain and the earth wire connected to the main building (e.g. a lightning strike hitting the ground next to the remote building and raising the local ground potential). This could cause a significant voltage difference between the copper earth wire and the building framework that could potentially cause damage. If the remote building had a local copper ground rod as well as the earth wire back to the main building, would that make things better or worse?

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