Electronics > Beginners

How is Neutral Wire Neutral in Mains Electricity?

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paulca:

--- Quote from: IanB 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.

--- End quote ---

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

richard.cs:

--- Quote from: IanB 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.


--- End quote ---

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.

Electro Detective:

--- Quote from: IDEngineer 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...


--- End quote ---

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..  :-[



 

 

IDEngineer:

--- Quote ---How does the GFCI thing work with 120 and 240 volts over in the US?
--- End quote ---
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?
--- End quote ---
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
--- End quote ---
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.

paulca:

--- Quote from: IDEngineer on January 30, 2020, 11:23:59 pm ---Yes, as discussed ad nauseum herein, GFCI's do not rely on an earth reference to operate, reliably or otherwise.

--- End quote ---

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

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