On Mon, 18 Jun 2018 19:06:38 +0100, trader_4 wrote:

On Monday, June 18, 2018 at 9:45:12 AM UTC-4, tony sayer wrote:
In article , Jimmy Wilkinson
Knife scribeth thus
On Mon, 11 Jun 2018 21:56:22 +0100, tony sayer
wrote:

In article , Jimmy Wilkinson Knife
scribeth thus
On Mon, 04 Jun 2018 21:37:20 +0100, ARW
wrote:

On 04/06/2018 10:56, Dave Plowman (News) wrote:
In article ,
tony sayer wrote:
Well maybe if they had a transformer for each house, but in the
present
setup its not a good idea to let it float..

Used to work in broadcast, where safety of things like electric
musical
instruments could be a very real problem, given all metalwork in a
studio
was earthed. (Before the days of RCDs, etc)

The norm was to use one isolating transformer per instrument. A
single
large one feeding all simply doesn't provide the same degree of
safety.

Same thing with generators and multiple tools. You only move the
problem
(if there is one) to inside the the genny or transformers supply
area.



Not if the secondary of the transformer isn't earthed, that's the
whole
point of
isolation. Paths to ground through people don't kill anymore. The
electricity
doesn't want to flow from one side of the secondary to ground.


This - is the fallibility of your argument.

You have a balanced isolated supply but in the real world electrical
equipment can and does develop faults. A cooker can develop a
leakage in
an element to the framework of the cooker an immersion heater can
develop a leak from the heating element to the metal case of the unit
thence to the metal hot water tank. A washing machine can do the same
with its heating element and it can also leak water into the motor
thus
in doing so the assumed balanced isolated supply is no more, you are
back unknowingly to the current setup with the live and neutral
system.

No. If my washing machine was fed from an isolated supply, and
developed
a leak to it's chassis, there would be one leg of an isolated
transformer
output on the chassis, with nowhere to go if I touched it, so
completely
safe.

Yes except that there are likely to be other appliances that can develop
leakage such as cookers, immersion heaters , kettles , electric irons
water heaters..

Or an unknown variant of the same, consider that if one unit were to
leak to earth on one side of the supply one on the other how would
you
detect the current flowing away to waste there?

Now you're considering two broken appliances, you're really
pessimistic.

Yes maybe but it can and does happen over time but the danger is you
wouldn't know its happened with a floating supply. With a live neutral
system it does come to notice rather quickly and the fault is noted and
rectified..

You're conflating two different things, bonding the eqpt grounds to one
side of the supply and an earth ground. You could use JWS's isolated
supply idea, where it's not tied to earth ground, but you still tie one
side of the supply to the eqpt ground at the panel. Then you'd be in
the same situation as we are now with a fault to the metal cabinet.
If the fault is on the bonded side, the cabinet is not energized.
If it's on the other side, it trips the breaker.

However if you have the established system you know that one side is
in
earthed and you can prevent all manner of accidental electrocution
with
a rather simple device a Residual Current Breaker this one device has
done more to prevent electrocution than any other

We used to manage with just fuses.

Yes we did manage but then again the human body currents are much less
then what a fuse can sort out..

That's for sure and we had plenty of people electrocuted and dead.
A teacher at my high school years ago died using a shop vacuum to suck
water out of a pool while standing in it. Today that circuit would be
protected by a GFCI (RCD over there?), and he'd be alive.

Why should we protect someone doing something that monumentally stupid?

To do this isolated supply would mean rewiring the UK. New
transformers
would be needed and the space to put them. Do bear in mind that some
residential accommodation like flats might not have the space if you
put
them outside then you'd be doing a lot of road digging and overhead
wiring for what real benefit?.

Why would the isolated transformers be larger?

They'd be many many more of them!. The current 3 phase distribution
system can and does supply many properties with a floating supply to
each property may more individual transformers are needed. Who is going
to pay and to what real benefit?.

I agree it makes no sense to change, but theoretically there is no reason
that several homes could not be on one shared transformer that is not
tied to earth ground just as easily as they are one that is tied to
earth ground.

Indeed, just remove the tie, no extra expense.

The big disadvantage which I addressed much earlier is that
without the service being tied to earth ground, there is no easy, direct
path for abnormal surges to take. With the existing service, if
lightning
strikes the transformer, the pole, the service going into the house, the
vast majority of the energy flows directly to earth ground. With no
earth
ground, now what?

You worry too much.

Let alone the removing of all the metal water pipes in the country.

Just don't put them in in new installations. I'm not asking for
everyone
to suddenly become isolated by next week.

Also
do bear in mind that not everyone is your electrically resistive self
people do have wet bodies in showers, children may not be quite so
hardy
either.

Bull****. Everyone is pretty much the same, save for a few with dodgy
tickers.

And thats -- the reason why your not in charge of the electricity supply
in the country!...
--
Tony Sayer

I agree, he should not be in charge of anything. Every time he
disparages
building and safety codes, I immediately think of that towering inferno
you had over there recently, where I believe codes for what was allowed
for the building covering were not followed. Or even if they were
followed,
the codes then would have been inadequate and a good example of why we
need
codes to stop people from building unsafe structures that wind up killing
everybody.

And how many buildings didn't meet that end? You're a typical newspaper
reader, 1 in 50,000 buildings catches fire and you think they're all
dangerous.