On Sun, 01 Jul 2018 22:05:18 +0100, Rod Speed
wrote:



"Jimmy Wilkinson Knife" wrote in message
news
On Sun, 01 Jul 2018 15:58:41 +0100, Bob F wrote:

On 6/29/2018 7:58 PM, Rod Speed wrote:
"Jimmy Wilkinson Knife" wrote in message
news On Sun, 24 Jun 2018 22:11:44 +0100, Rod Speed
wrote:

Cursitor Doom wrote
ARW wrote

I wish he would try it.

I'm not wasting more time on that oaf, but just wondering whether
we should be moving on to a 'post-earth world' for other reasons..

To some extent we have with double insulated appliances most
obviously.

But there is still a problem with washing machines, dishwashers,
electrical water heaters and ovens and stoves etc which arent
really practical to do double insulated.

How is that a problem?
Because when a fault shows up in one of those, there
will be no indication of a fault at all and the protection
that nothing earthed used to provide is now gone.
So you no longer have any protection, and that is
over the entire collection of houses etc that are
powered from that transformer in the substation if you
dont have individual transformers for each house.

The case could be not connected to anything, and the power could be
isolated from ground. If one side of the power touched the casing,
nothing would happen, as it would have no desire to go to ground.
Yes, but with those devices that have other grounds
likely present via the water pipes etc, you now have
a problem that the case is at mains voltage and
touching that and the ground simultaneously and
that can certain kill you with that in separate hands
as is most likely in that situation.

What causes the danger is because live wants to go to ground,
through you.
And that can happen post fault when the fault
produces no visible effects and the device keeps
working and there are other grounds available.

A big problem of having no ground reference in the power lines is that
any leak to ground in any device in any house sharing the transformer
with you can float the entire power supply to any level. If some
device like a high voltage low current power supply made contact to
either of the power phases, there would be nothing to stop all the
power lines in those houses from floating up to whatever voltage it
drives. Then that power could arc from the power connectors anywhere
to any nearby ground or even a person standing on a concrete floor.

With devices using power referenced to ground, every device would be
sinking that low current device to ground.

You're talking about the output from a say 1kV low current power supply.

That voltage is normally 11KV and it isnt low current either.

It's not normally anything. You can buy HV PSUs at any voltage. I have
one here that's variable up to 3kV.

So one of those outputs touches the supply line, so what?

We arent talking about one of those touching the supply line,
we are talking about a fault in one of the heater elements in
an appliance earthing one side of the floating supply.

Which makes things no worse than the earthed supply we have now.

How is that going to want to go to anywhere but the other side of that
power supply's output?

It earths one of the supply rails and does that completely
silently with a floating supply, wont even blow a fuse.

And then, when anyone gets between a supply line and
earth, they get electrocuted and since that is quite likely
to see the current go thru their body because what is
in contact with the supply line is usually a different arm or
foot to what is in contact with the earth, high risk of dying.

And an RCD can't protect that individual in that situation.

We're discussing an HV power supply. It's output won't go to ground, it's
ISOLATED.

"Jimmy Wilkinson Knife" wrote in message
news
On Sun, 01 Jul 2018 22:05:18 +0100, Rod Speed
wrote:



"Jimmy Wilkinson Knife" wrote in message
news
On Sun, 01 Jul 2018 15:58:41 +0100, Bob F wrote:

On 6/29/2018 7:58 PM, Rod Speed wrote:
"Jimmy Wilkinson Knife" wrote in message
news On Sun, 24 Jun 2018 22:11:44 +0100, Rod Speed
wrote:

Cursitor Doom wrote
ARW wrote

I wish he would try it.

I'm not wasting more time on that oaf, but just wondering whether
we should be moving on to a 'post-earth world' for other reasons.

To some extent we have with double insulated appliances most
obviously.

But there is still a problem with washing machines, dishwashers,
electrical water heaters and ovens and stoves etc which arent
really practical to do double insulated.

How is that a problem?
Because when a fault shows up in one of those, there
will be no indication of a fault at all and the protection
that nothing earthed used to provide is now gone.
So you no longer have any protection, and that is
over the entire collection of houses etc that are
powered from that transformer in the substation if you
dont have individual transformers for each house.

The case could be not connected to anything, and the power could be
isolated from ground. If one side of the power touched the casing,
nothing would happen, as it would have no desire to go to ground.
Yes, but with those devices that have other grounds
likely present via the water pipes etc, you now have
a problem that the case is at mains voltage and
touching that and the ground simultaneously and
that can certain kill you with that in separate hands
as is most likely in that situation.

What causes the danger is because live wants to go to ground,
through you.
And that can happen post fault when the fault
produces no visible effects and the device keeps
working and there are other grounds available.

A big problem of having no ground reference in the power lines is that
any leak to ground in any device in any house sharing the transformer
with you can float the entire power supply to any level. If some
device like a high voltage low current power supply made contact to
either of the power phases, there would be nothing to stop all the
power lines in those houses from floating up to whatever voltage it
drives. Then that power could arc from the power connectors anywhere
to any nearby ground or even a person standing on a concrete floor.

With devices using power referenced to ground, every device would be
sinking that low current device to ground.

So one of those outputs touches the supply line, so what?

We arent talking about one of those touching the supply line,
we are talking about a fault in one of the heater elements in
an appliance earthing one side of the floating supply.

Which makes things no worse than the earthed supply we have now.

The difference is that with your scheme, you know it doesnt matter
if you touch a bare active line, because its floating. If one of the heater
elements has silently earthed one side of the supply, in any of the
houses supplied from that 11KV to 240V street transformer, if you
touch that active then, that can kill you.

With the current approach, the failure of the heating element will trip
the RCD so you have replace the heating element and cant ignore it.

How is that going to want to go to anywhere but the other side of that
power supply's output?

It earths one of the supply rails and does that completely
silently with a floating supply, wont even blow a fuse.

And then, when anyone gets between a supply line and
earth, they get electrocuted and since that is quite likely
to see the current go thru their body because what is
in contact with the supply line is usually a different arm or
foot to what is in contact with the earth, high risk of dying.

And an RCD can't protect that individual in that situation.

We're discussing an HV power supply.

Nope, we're discussing your proposal that mains supplys should be floating.

On Wed, 18 Jul 2018 05:47:09 +1000, cantankerous geezer Rot Speed blabbered,
again:

We're discussing an HV power supply.

Nope, we're discussing your proposal that mains supplys should be floating.

*I* keep discussing your idiocy and pathetic trolling! LOL

--
Cursitor Doom about Rot Speed:
"The man is a conspicuous and unashamed ignoramus."
MID: