Author Topic: How is Neutral Wire Neutral in Mains Electricity?  (Read 17967 times)

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Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #75 on: January 20, 2020, 10:15:29 pm »
Neutral and earth are supposed to be bonded in the panel. That's what existed in the original structure.

In the first panel. And this discussion shows precisely why nobody else does it that way..
 

Offline sokoloff

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #76 on: January 21, 2020, 12:06:30 am »
The inspector has a crystal-clear NEC reference on his side (assuming the AHJ has adopted NEC of 2008 or later, which seems likely) to require a four-wire feed. I have no issue with that.

I do think it's ridiculous that he demanded you disconnect the additional ground rods for the outbuilding and I'd have done exactly as you did in that case-reconnect them as soon as you had the sign-off and heard his car door close.
 

Offline CatalinaWOW

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #77 on: January 21, 2020, 07:16:31 am »
OK.  I'm the slow guy in the back of the class.  Why does the fourth case kill you?   It requires the place the person is standing on to have a better path back to the ground rod than any of the ground or neutral wiring, which is certainly a possibility, but not a sure thing, and maybe not even likely.  Having a local ground rod in the right hand building may make it more likely, but might not.
« Last Edit: January 21, 2020, 07:18:15 am by CatalinaWOW »
 

Offline GeorgeOfTheJungle

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #78 on: January 21, 2020, 11:33:41 am »
OK.  I'm the slow guy in the back of the class.

No, I'm the slow one, I don't even understand those drawings.
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Online Siwastaja

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #79 on: January 21, 2020, 11:51:21 am »
Line (1, 2, 3), neutral, CPC. Line and neutral are live. Terminology already well under control, at least for some of us..

Thanks, this is the key. As you confirm, line and neutral are both live. It's sad that "live" is just one letter from "line", both written and pronounced. "live and neutral", a phrase which shouldn't exist at all, produces 503 000, "line and neutral" 1 210 000 results on Google, same order of magnitude.

Similar discussions happen everywhere, on- and offline, and they are always total train wrecks.

Statements like "neutral and earth are the same", as seen in this thread, as well, while technically correct to a limited degree, are extremely dangerous and easily misunderstood. This statement has a scope: N and PE are the same, inside a certain distribution box which connects them together, when the wiring is correct. But a large percentage of people reading these discussions are not electricians wiring up distribution boxes; instead, they might apply what they hear when wiring appliances.

Logical thinking based on the definitions:

Live = dangerous,
PE = not dangerous (otherwise it wouldn't be exposed everywhere!),
Neutral = Live (by definition),

Substituting Live = dangerous:
Neutral = dangerous
Substituting Neutral = PE, as suggested by many (including in this thread!)
Dangerous = not dangerous - a logical mismatch

Hence,

Claim "Neutral = PE" does not hold (as per the rating of dangerousness based on definition of being live or not, which exists for good reasons).

This is unsurprising - if neutral and PE were the same thing, why bother having the two?
« Last Edit: January 21, 2020, 04:46:56 pm by Siwastaja »
 

Offline paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #80 on: January 22, 2020, 08:50:26 am »
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.

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

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #81 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.)
 

Offline paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #82 on: January 22, 2020, 02:53:20 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.)

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.
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Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #83 on: January 22, 2020, 07:17:57 pm »
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.

...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?
 

Offline IanB

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #84 on: January 22, 2020, 07:30:16 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?

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?
 

Offline paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #85 on: January 23, 2020, 11:06:06 am »
I found this interesting...  I think the point that the ground charge between the building and outbuilding being different is covered.  Doesn't necessarily need to be lightening, but static.  The resistance through the potentially dry soil will be significantly higher than through a copper conductor to equalizer the charge differential between the buildings.  As I understand it anyway.


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Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #86 on: January 23, 2020, 08:59:23 pm »
Doesn't necessarily need to be lightening, but static.  The resistance through the potentially dry soil will be significantly higher than through a copper conductor to equalizer the charge differential between the buildings.
Slightly changing the subject... I had an amazing demonstration of static in the atmosphere a few years ago. Our whole family is ham radio operators and we had (at that time) a 1/4 wave multiband vertical antenna on the top of our house, with LMA-400 coax coming to a permanent N-female outlet on the wall in the family room. All equipment was unplugged because nobody was using it. I heard a "SNAP" sound which I didn't recognize. Happened again after 15-30 seconds. Kept repeating every once in a while, which allowed me to start tracking it down. I finally found that the N-female was arcing from its center conductor to the shield... the arc was VERY visible and quite loud when you were near. I presumed there was a buildup of static outside, mentioned that to the family, and shortly thereafter we got the first clap of thunder. A significant rain/thunderstorm followed.

This was a great learning opportunity for my then perhaps 10YO son (who had his General at the time). We regularly discussed antenna theory, so many volts per meter, etc. but nothing makes it real like seeing how a metal rod in the air can pick up enough voltage potential to visibly arc across a connector!

I was really glad no sensitive receivers were connected to that N-female.

Sorry for the thread hijack but your comment brought back a vivid memory.
 

Offline richard.cs

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #87 on: January 24, 2020, 01:51:02 pm »
I have nothing immediately to hand to show a lead-clad cable - presumably because those things are sealed with pitch and not easily cleaned for your viewing pleasure..

I've just stepped outside and taken some for your viewing pleasure. Various copper and aluminium cored PILCs, all four core (L1 L2 L3 and N) with the lead used as a separate earth right back to the substation. Two have undersized neutrals as was historically normal. The one with the orange plastic bags in the photo shows hints of the steel tape armour over the lead, this has been removed on the others.



Modern UK practice uses three core cables, often aluminium, with a combined neutral earth as copper loosely spiralled around the outside (lookup "wavecon") but N and E are always separated before they get to the consumer.
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #88 on: January 24, 2020, 06:01:06 pm »
I have nothing immediately to hand to show a lead-clad cable - presumably because those things are sealed with pitch and not easily cleaned for your viewing pleasure..

I've just stepped outside and taken some for your viewing pleasure. Various copper and aluminium cored PILCs, all four core (L1 L2 L3 and N) with the lead used as a separate earth right back to the substation. Two have undersized neutrals as was historically normal. The one with the orange plastic bags in the photo shows hints of the steel tape armour over the lead, this has been removed on the others.

Modern UK practice uses three core cables, often aluminium, with a combined neutral earth as copper loosely spiralled around the outside (lookup "wavecon") but N and E are always separated before they get to the consumer.

Very nice - but I was thinking more the termination arrangement for a single-phase lead-clad cable as was once brought into properties.
 

Offline IanB

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #89 on: January 24, 2020, 07:22:33 pm »
There doesn't seem to be much separation between the conductors in this cross-section? It looks a bit scary.

 

Offline paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #90 on: January 24, 2020, 07:35:30 pm »
There doesn't seem to be much separation between the conductors in this cross-section? It looks a bit scary.

With such absolutely anal regulations beyond the utility cable in UK houses it is a bit a wonder how scary the distribution networks are.
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Offline richard.cs

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #91 on: January 24, 2020, 09:32:54 pm »
There doesn't seem to be much separation between the conductors in this cross-section? It looks a bit scary.


From memory it's about 3 mm of oiled paper around each conductor so 6mm total between them. I think it's partly that the copper is a bit bent from the cutting and partly that the size of the cable is not clear in the photo, I think it's about 60mm OD.
 

Offline Electro Detective

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #92 on: January 30, 2020, 10:22:01 pm »

...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...



AFAIK RCBOs here in Australia/NZ and the UK are a combination of RCD and MCB combined, usually in a single DIN slot package with active and neutral from the N busbar coming in,

and active and neutral going out to the load/s.

The RCD section work as they should to spec and easy to verify with a decent RCD tester

The MCB section, depending on the current curve (B, C, D, or anyone's guess sometimes.. :-//)  reacts to short circuits and massive 5x > 10x current draw,
but a bit of a fail on slow-ish thermal based gradual over-current.   

The 10 amp rated small breakers fitted to 4 way/6 way power boards/power strips work a lot better in that regard,
once things get ~hot~ anywhere from 8 amps to 20 amps, they will pop reliably,
whilst the 16 or 20 amp RCBO downstream fed with warm wire symptoms just sits there clueless  ??? 

fwiw I use RCBO and power strip to cover all bases,
and if I need a faster and or no brainer solution, a temporary in-line fuse to suit the load or DUT  :phew:

----------------------------

How does the GFCI thing work with 120 and 240 volts over in the US?

Do the separate 120 and 240 circuits have separate rated GFCIs, or go to a Master?

What about 208v branches?

I've seen Youtubers play with 120 <> 240 adapters to pull serious welder current or power homebrew -LightNing- rigs  :scared: 
are they still getting GFCI benefits if GFCI is fitted?
 
Will GFCIs in the US still work with a good centre tapped Neutral connection and failed Earth connection
and how reliably?


More better worded questions coming once the coffee kicks in..  :-[



 

 
« Last Edit: January 31, 2020, 09:14:31 am by Electro Detective »
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #93 on: January 30, 2020, 11:23:59 pm »
Quote
How does the GFCI thing work with 120 and 240 volts over in the US?
Same way. It looks for an imbalance in the current flow, which indicates a secondary path has been found (maybe YOU!), and opens the circuit(s).

Quote
Do the separate 120 and 240 circuits have separate rated GFCIs, or go to a Master?
Here in the US you can buy single pole (one "hot" phase, 120VAC) and double pole (two "hot" phases, 240VAC), in a single unit with a single white pigtail connection to neutral.

Quote
Will GFCIs in the US still work with a good centre tapped Neutral connection and failed Earth connection
Yes, as discussed ad nauseum herein, GFCI's do not rely on an earth reference to operate, reliably or otherwise. They need a neutral connection but not an earth reference. If neutral and earth are bonded then you could argue that the GFCI "has an earth reference", but that is a byproduct and plays no role in how the GFCI operates.
 

Offline paulca

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #94 on: January 31, 2020, 02:39:17 pm »
Yes, as discussed ad nauseum herein, GFCI's do not rely on an earth reference to operate, reliably or otherwise.

So, explain why some of them DO have an earth reference.
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Offline richard.cs

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #95 on: January 31, 2020, 02:57:08 pm »
Yes, as discussed ad nauseum herein, GFCI's do not rely on an earth reference to operate, reliably or otherwise.

So, explain why some of them DO have an earth reference.
All-mechanical RCDs operate on differential current only. The output of the current transformer directly drives the trip coil, the mechanism is sensitively balanced and quite delicate. These are vulnerable to sticking and modern ones often use the CT output to trigger a thyristor and dump a heavier current into the trip coil from the L-N voltage. These therefore don't work in absence of L-N voltage which becomes a safety problem if the neutral is open-circuit upstream of the RCD. A subset of this type therefore use a functional earth connection as a alternate place to pass tripping coil current to.

In UK practice RCBOs are often half the width of an RCD, and sometimes do not switch neutral (this is a rubbish plan but very common). It may be that due the the space constraints these are more likely to have electronic tripping, but in any case it seems far more common for RCBOs to have a functional earth than for RCDs to have them. Also some RCBOs have earth tails that are essentially just there for EMC filtering.
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #96 on: January 31, 2020, 07:28:32 pm »
Yes, as discussed ad nauseum herein, GFCI's do not rely on an earth reference to operate, reliably or otherwise.

So, explain why some of them DO have an earth reference.
The better question would be why some have earth references and some do not. From their presence in the market and their acceptability to (at least) the National Electrical Code, we know that GFCI's without discrete earth references work just fine. So the question becomes why both types are available.

I ran across a discussion of the optional discrete earth connection while replying earlier in this thread, but can't find it again right now. As I recall, GFCI's having discrete earth connections are able to detect yet another type of fault. If so, this would add another "choice" to the range of options in modern circuit breakers and you buy your device based on which of the following options you want: Overcurrent, differential current, arc detection, and now "earth fault" (whatever that last one means). But this thread has focused on the GFCI aspect of operation, and it's crystal clear that an earth reference is NOT required for that.
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #97 on: January 31, 2020, 08:15:23 pm »
But this thread has focused on the GFCI aspect of operation, and it's crystal clear that an earth reference is NOT required for that.

Actually, certain people have latched onto such despite them not being the subject..
 

Offline IDEngineer

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #98 on: January 31, 2020, 09:07:42 pm »
But this thread has focused on the GFCI aspect of operation, and it's crystal clear that an earth reference is NOT required for that.
Actually, certain people have latched onto such despite them not being the subject..
I checked back and you're correct. YOU first raised the question of breakers not operating properly in this response:

https://www.eevblog.com/forum/beginners/how-is-neutral-wire-neutral-in-mains-electricity/msg2879446/#msg2879446

...wherein you said:

Quote
No, then how do you know the breakers will operate correctly?

Prior to that, references to breakers dealt with the OP keeping himself safe. Speaking for me, my comments had been limited to the thread topic, the neutral wire (and its relation to earth), until your query at me about breakers possibly not operating properly. Which I addressed because otherwise casual readers might be misled into believing that breakers require an earth reference, and it's dangerous to leave misinformation uncorrected when dealing with mains voltages.
 

Offline Monkeh

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Re: How is Neutral Wire Neutral in Mains Electricity?
« Reply #99 on: February 01, 2020, 12:28:49 am »
But this thread has focused on the GFCI aspect of operation, and it's crystal clear that an earth reference is NOT required for that.
Actually, certain people have latched onto such despite them not being the subject..
I checked back and you're correct. YOU first raised the question of breakers not operating properly in this response:

https://www.eevblog.com/forum/beginners/how-is-neutral-wire-neutral-in-mains-electricity/msg2879446/#msg2879446

...wherein you said:

Quote
No, then how do you know the breakers will operate correctly?

Prior to that, references to breakers dealt with the OP keeping himself safe. Speaking for me, my comments had been limited to the thread topic, the neutral wire (and its relation to earth), until your query at me about breakers possibly not operating properly. Which I addressed because otherwise casual readers might be misled into believing that breakers require an earth reference, and it's dangerous to leave misinformation uncorrected when dealing with mains voltages.

Now search long and hard for 'GFCI', 'RCD', 'RCCB' or 'RCBO' in my post.. I was referring to the function of MCBs, as not all circuits may require or desire residual current protection (unless you have a TT earthing arrangement - which you might well have created with your, uh, interesting approach to performing electrical work).
 


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