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dangerous advice?

In a lot of countries there is still earth at all. I encountered this in the canary isles many years ago, and from reports I hear not a lot has changed. Brian

Reply to
Brian Gaff
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About the only situation where it might not be the case is with an IT style feed from a generator or inverter. That may have both sides floating with respect to true earth. I am not aware of any actual fixed distribution systems that operate like that though.

Yup you will get higher shock currents between the two ends of the centre tapped transformer than between one end and the centre. However both will be lethal in the wrong circumstance.

No, if anything it may be slightly less (depending on the earthing scheme). Under load the neutral will tend to rise a little in voltage near the load end, and the line fall a bit, reducing the potential difference. If the earth is independently connected back to the transformer or substation (i.e. TN-S) Then it won't see this voltage rise.

(that's why a neutral to earth short often causes a RCD trip)

Reply to
John Rumm

No, With no load it is neither alive nor dead.

AB

Reply to
Archibald Tarquin Blenkinsopp

After careful consideration I now consider that 95% of what you read or hear on the media and the internet is more or less total rubbish

The other 5% IS total rubbish.

The first question you ask is 'who paid this person to write this'

Reply to
The Natural Philosopher

If there's potential difference WRT ground it's live even if there's no current. Neutral can also be slightly live. ;-)

Reply to
Rob Morley

neutral connections can be live at 240v no less. That's why a combined N&E is not normally permitted in domestic wiring.

The US used to permit it and I gather it was once common for kitchen cookers to have a combined N&E conductor. I hear the incidence of bad outcomes was near zero, but I don't have any direct access to stats to quote.

NT

Reply to
tabbypurr

To measure the potential difference you have to apply a load.

When you apply a load, the line becomes live or dead.

Now my mate Erwin has an iffy pussycat, ................................

AB

Reply to
Archibald Tarquin Blenkinsopp

If you don't apply a load the line is already live or dead.

I considered that aspect and decided it was mostly irrelevant to domestic wiring issues.

Reply to
Rob Morley

In principle you do not have to apply a load, for instance a bridge method can be used which while it may apply a minimal load, or a minimal generator during adjustment has neither at balance.

Reply to
Roger Hayter

Why? Perfectly valid methinks.

The pussycat has been going since 1935 and still isn't dead, or alive come to that.

So a bit of twin & earth might not be quite as old, but I'm sure the same logic can be applied :-)

AB

Reply to
Archibald Tarquin Blenkinsopp

Didn't know Rommel had a cat. ;O)

Reply to
soup

Only at the measuring device itself, the bridge must sink current.

Even a minimal load has affected the system, thus taking the conductor into a condition where it has a potential, or not of course.

AB

Reply to
Archibald Tarquin Blenkinsopp

The bridge at one side of balance supplies current to the DUT and at the other side of balance sinks it. It therefore passes through a point of zero current at balance.

Reply to
Roger Hayter

There is always about .6v drop on a diode as well and you have to load it to see it I'd imagine as a very high impedance can measure voltages with the lead just hanging close to an ac source. Brian

Reply to
Brian-Gaff

Correct, it depends how the bridge is configured of course.

As the observation has been made, it has affected the measured circuit thus the the cable has become live, or not.

A bit like sticking a bowl of milk into tiddles safe, it may not be touched, but the interaction means that Tiddles is alive, or dead maybe.

AB

Reply to
Archibald Tarquin Blenkinsopp

No, you are simply wrong. The potential (emf) on wire is there totally irrespective of current flow into a measuring instrument or anywhere else. There are no quantum effects on the scale involved. For instance, if the voltage is high enough you will get corona effects regardless of current flow.

Reply to
Roger Hayter

Emmission of photons, interaction with the observer.

You must have current flow to get a corona incidentally.

A corona tends to be avoided by Electricity suppliers, perhaps not as wasteful as direct arcing, it does waste power.

AB

Reply to
Archibald Tarquin Blenkinsopp

they waste money but ISTR them tasting ok, at least to a kid

NT

Reply to
tabbypurr

Your statement does not agree with the accepted use of the term "live" in the UK wiring regs.

(that's aside from being nonsense at pretty much any level).

Reply to
John Rumm

Well its the nym shifting Pork Sword innit?

What do you expect?

Reply to
The Natural Philosopher

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