Two phases to house - loss of neutral

[Jamie]

Sylvia Else wrote:

D Yuniskis wrote:

Sylvia Else wrote:

Phil Allison wrote:

The MEN system:

In Australia, AC power delivery uses a system called " Multiple
Earth Neutral " - which requires that the neutral conductors in a
premises be connected to the plumbing system at the distribution
board (ie power box). It also requires that an earth stake be
installed for the same purpose, but some older premises may not have
this.


If as you say, neutral has to be tied to Earth at the premises, then
I can indeed see that the situation might not be so bad.


Grounding the mains to "plumbing" *was* common in the US many
years ago. Now, I believe, you *must* ground to a metal
rod driven into the earth (8 ft?). Note that if the water
meter was removed, your earth-through-plumbing would fail.

On the face of it, having significant current flowing from neutral to
Earth would have to indicate a fault. It would be nice for the
breakers to trip in such a situation, but I can't see that they will.


This is how GFCI breakers work -- they watch for current "leaking"
off to ground someplace other than in the "return" conductor.


In the scenario I outlined, the currents in the live and neutral
conductors passing through the breakers would remain equal, so they
wouldn't trip.

What I need is something to detect current through the link between
neutral and ground, which would then disconnect both phases. Of course,
it could trip as the result of a fault with the neigbour's neutral wire,
but I could live with that.

Sylvia.
You need to pass the live and neutral through a common mode

transformer. when one leg gets shorted to ground, it unbalances.
You wrap another winding in that coil which will then produce some
current for you to trigger a protection device. The current will only
be present when the common mode becomes unbalanced due to them
canceling each other out under normal operation.

This will accommodate for both legs.

have a good day..

 

[Phil Allison]

"Trevor Wilson"

**AFAIK, the US system is fundamentally different to ours.

** In the US and Canada - it is NOT permitted to link neutral and earth
or plumbing within a premises.

See here under the heading "Regulations".

http://en.wikipedia.org/wiki/Earthing_system

The MEN system used here in Australia seems to be unique.

See last para on same page.


...... Phil

 

[Phil Allison]

"kreed"

From what I can gather, pretty much every home in the US has a 120v -
0 - 120v system where the 2x 120v's are 180 degrees out of phase.
Between the 2 phases 240v is available for stoves, air conditioners
etc.

In Australia, most separate homes have a straight single phase 240v
supply, its not common for there to be 2,3 separate phases to the
average house. Therefore the scenario Sylvia mentions is less likely
to occur, as not many people have this multi phase system.

The exception here could be blocks of flats, if the main neutral to
the building fails, and there isn't a good earth, the imbalance could
be a risk.

** There is always a good "earth" available - courtesy of the water mains
in the street being linked to neutral at every premises.


...... Phil

 

[Allodoxaphobia]

On Tue, 24 Nov 2009 09:28:48 +0800, TonyS wrote:

Sylvia Else wrote:
I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two
sets are unlikely to represent equal loads, the net result would be a
large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?

I had exactly this happening two years ago.
My supply has 3 phases ... <-snip-

Oh?? Really?!?!

 

[Trevor Wilson]

Phil Allison wrote:

"Trevor Wilson"


**AFAIK, the US system is fundamentally different to ours.


** In the US and Canada - it is NOT permitted to link neutral
and earth or plumbing within a premises.

See here under the heading "Regulations".

http://en.wikipedia.org/wiki/Earthing_system

The MEN system used here in Australia seems to be unique.

See last para on same page.

**Interesting. I'd have thunk that some places in Europe might employ a
similar system. Guess not. Ever since I ran across my first US audio product
with a high value resistor to chassis from (allegedly) Neutral, I realised
that the US system was highly flawed.


--
Trevor Wilson
www.rageaudio.com.au

 

[kreed]

On Nov 24, 12:16 pm, Sylvia Else <syl...@not.at.this.address> wrote:

Phil Allison wrote:
"Dave Platt"
Sylvia Else

I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two
sets are unlikely to represent equal loads, the net result would be a
large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.
It's a huge issue.

** Sylvia lives in Sydney, Australia and is a MASSIVE TROLL.

Nuts of her the post such a COUNTRY SPECIFIC message to a US newsgroup.

Last time I checked, multiphase power supply was pretty universal, and
the principles to be applied in understanding the consequences of faults
would be the same. Or perhaps you want to argue that the different
voltage in Australia is the deciding factor.

Sylvia.

From what I can gather, pretty much every home in the US has a 120v -
0 - 120v system where the 2x 120v's are 180 degrees out of phase.
Between the 2 phases 240v is available for stoves, air conditioners
etc.

In Australia, most separate homes have a straight single phase 240v
supply, its not common for there to be 2,3 separate phases to the
average house. Therefore the scenario Sylvia mentions is less likely
to occur, as not many people have this multi phase system.

The exception here could be blocks of flats, if the main neutral to
the building fails, and there isn't a good earth, the imbalance could
be a risk.

 

[D Yuniskis]

Phil Allison wrote:

"Trevor Wilson"

**AFAIK, the US system is fundamentally different to ours.

** In the US and Canada - it is NOT permitted to link neutral and earth
or plumbing within a premises.

"*within* a premises". The neutral *is* "earthed" right outside
the home, typically. The Code goes to great lengths telling
you exactly *how* to earth the mains at the service entrance.

However, this ignores the fact that most residential wiring
is grandfathered into "acceptance". Previously, homes *were*
grounded through their "water main" (e.g., my parents home
has ground at the water meter).

So, you can encounter all sorts of different situations
here in the US (I've even worked on homes with knob & tube
wiring!)

See here under the heading "Regulations".

http://en.wikipedia.org/wiki/Earthing_system

The MEN system used here in Australia seems to be unique.

See last para on same page.

 

[F Murtz]

Sylvia Else wrote:

I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two
sets are unlikely to represent equal loads, the net result would be a
large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?

Sylvia.
not a neutral problem but.

I can remember an old lady complaining that every time she turned the
hot water tap the lights came on half brilliance.and sure enough they did.
she had three phase and an instantaneous three phase water heater.

one phase had gone and the heater caused the dead phase to be live in
series with element.(the water flow closes the heater circuit)

 

[kreed]

On Nov 24, 10:58 am, "Phil Allison" <phi...@tpg.com.au> wrote:

"Stupider than Anyone Else"

I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two sets
are unlikely to represent equal loads, the net result would be a large
overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

** Loss of the neutral conductor in a 3 phase ( or 2 phase) AC supply system
can easily be a DISASTROUS event.

For example:

In the live entertainment productions - high powered lighting and sound
systems operate from 3 phase outlets via a hefty 5 pin plug and socket. If,
due to wear and tear or damage to the plug or socket, one of the phases
drops out - that is an annoyance but not a disaster.

However, if the pin carrying the neutral fails to connect or as is often the
case *disconnects* during a show because of overheating - ALL HELL
BREAKS LOOSE !!

Typically, some of the lamps will glow very brightly for a second or two and
fail, then other previously dim lamps will follow suit. The AC fuses in
amplifiers will pop instantly and some equipment will be seriously damaged
when the PSU sections are destroyed. It all happens in a few seconds, while
the operators stand there with their mouths open !!!

The MEN system:

In Australia, AC power delivery uses a system called " Multiple Earth
Neutral " - which requires that the neutral conductors in a premises be
connected to the plumbing system at the distribution board (ie power box).
It also requires that an earth stake be installed for the same purpose, but
some older premises may not have this.

Because EVERY premises has MEN installed, the ground itself and underground
metal plumbing act as an alternative neutral, should the supply conductor
feeding a given premises fail. The disastrous event sometimes experienced in
live entertainment systems is hardly possible in domestic or commercial
premises.

So the sparky is right.

The scenario you mention with live entertainment is particularly bad,
as when you think about it, unlike a fixed installation you can't bond
the earth and neutral in these portable 3 phase to 240v outlet mains
boxes. If you did, it would trip any earth leakage breakers upstream
- if these are fitted.


To make matters worse, in live entertainment, the major loads are
almost all amplifiers, and lighting. None of these are stable loads
(amplifiers are changing their load current draw constantly with the
music and lights are being dimmed, flashed often in large groups. )


Therefore if the neutral lead fails, there is no bonding to earth to
back it up, unlike a residence, and with the inherent instabilty of
the load balance , massive damage is guaranteed.


> .... Phil

 

[D Yuniskis]

Phil Allison wrote:

"Stupider than Anyone Else Alive "

** Sylvia lives in Sydney, Australia and is a MASSIVE TROLL.

Nuts of her the post such a COUNTRY SPECIFIC message to a US newsgroup.
Last time I checked, multiphase power supply was pretty universal, and the
principles to be applied in understanding the consequences of faults would
be the same.

** 100 % WRONG !!!

The question this insane bitch posted IS country SPECIFIC !!!

Cos it was about her house in * Sydney, Australia *.

Wow, why all the hostility? A "personal gripe"?

Can I suggest that if you don't want to see posts by a particular
person, you simply add his/her name to your "kill file" (or
whatever Microsoft Outlook Express 6.00.2900.2180 uses for that
feature)?

Speaking solely for myself -- but, perhaps, reflecting the
experiences of many "fellow countrymen" -- I think most Americans
have very little exposure to "other cultures/societies/power
distribution systems/etc :> " owing, perhaps, to the large size
of our country and its relative homogeneity. I find it
interesting to hear how things are done "elsewhere" and,
especially, *why*.

("Driving on the PARKWAY and parking in the DRIVEWAY...") ;-)

 

[Bob AZ]

My electrician says it's not an issue, but I can't see why.

Any thoughts?

Sylvia.

Sylvia

Thought one. Get rid of the electrician.

In my experience with loss of neutrals it is the number one cause of
electrical equipment/lighting failure.

Bob AZ

 

[Sylvia Else]

D Yuniskis wrote:

Phil Allison wrote:
"Stupider than Anyone Else Alive "

** Sylvia lives in Sydney, Australia and is a MASSIVE TROLL.

Nuts of her the post such a COUNTRY SPECIFIC message to a US
newsgroup.
Last time I checked, multiphase power supply was pretty universal,
and the principles to be applied in understanding the consequences of
faults would be the same.

** 100 % WRONG !!!

The question this insane bitch posted IS country SPECIFIC !!!

Cos it was about her house in * Sydney, Australia *.

Wow, why all the hostility? A "personal gripe"?

Can I suggest that if you don't want to see posts by a particular
person, you simply add his/her name to your "kill file" (or
whatever Microsoft Outlook Express 6.00.2900.2180 uses for that
feature)?

Trouble is, if Phil were to killfile everyone he abuses, he wouldn't
actually see any posts.

Sylvia.

 

[D Yuniskis]

Sylvia Else wrote:

D Yuniskis wrote:
Phil Allison wrote:
"Stupider than Anyone Else Alive "

** Sylvia lives in Sydney, Australia and is a MASSIVE TROLL.

Nuts of her the post such a COUNTRY SPECIFIC message to a US
newsgroup.
Last time I checked, multiphase power supply was pretty universal,
and the principles to be applied in understanding the consequences
of faults would be the same.

** 100 % WRONG !!!

The question this insane bitch posted IS country SPECIFIC !!!

Cos it was about her house in * Sydney, Australia *.

Wow, why all the hostility? A "personal gripe"?

Can I suggest that if you don't want to see posts by a particular
person, you simply add his/her name to your "kill file" (or
whatever Microsoft Outlook Express 6.00.2900.2180 uses for that
feature)?

Trouble is, if Phil were to killfile everyone he abuses, he wouldn't
actually see any posts.

<frown> So I guess it's "nothing personal"! ;-)

 

[William R. Walsh]

Hi!

I've on occasion wondered what would happen if we lost the neutral line.

(speaking from a 110V perspective as I'm in the US where power is delivered
as 2x110 volt hot leads with one neutral)

The voltage between the two fluctuates wildly, that's what. The more heavily
loaded of the two will have a voltage drop while the lightly loaded one goes
up.

CRT computer monitors get the jitters even when things are relatively
normal. I don't know why this is. Damage can occur to devices when they get
nailed with high voltage.

It won't be a huge issue up to a point for simple devices, or those with
autoranging power supplies that may try to compensate. Everything else will
suffer--motors, transformer type power supplies, etc...and your electrican
*should* know that. A fire could start depending upon how badly something
reacts to the over or under voltage.

William (had it happen here some years ago - one TV and a few surge
protectors got burnt. Curiously, the TV was not completely dead afterwards,
just temperamental about turning on when warm.)

 

[nesesu]

On Nov 23, 6:36 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

"Trevor Wilson"



**AFAIK, the US system is fundamentally different to ours.

** In the US and Canada  -   it is  NOT  permitted to link neutral and earth
or plumbing within a premises.

See here under the heading "Regulations".

http://en.wikipedia.org/wiki/Earthing_system

The MEN system used here in Australia seems to be unique.

See last para on same page.

.....  Phil

Rubbish. In most of Canada, it is manditory that the neutral be bonded
to earth at only ONE point, the service entrance switch enclosure.
From that point an earth conductor is connected to 2 ground rods and
to any metallic piping system(s).
Neutral failure is a not uncommon problem especially with overhead
aluminum 'triplex' service drops. A seagull deficates on the bare
aluminum neutral and it soon rots off leaving an open neutral
condition.
Ground rod to earth resistances of 5 ohms are not uncommon, so a 10A
unbalance between 'phases' could give a 50V offset of the neutral.

Neil S.

 

[nesesu]

On Nov 23, 6:40 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

"kreed"

From what I can gather, pretty much every home in the US has a 120v -
0 - 120v system where the 2x 120v's are 180 degrees out of phase.
Between the 2 phases 240v is available for stoves, air conditioners
etc.

In Australia, most separate homes have a straight single phase 240v
supply, its not common for there to be 2,3 separate phases to the
average house.  Therefore the scenario Sylvia mentions is less likely
to occur, as not many people have this multi phase system.

The exception here could be blocks of flats, if the main neutral to
the building fails, and there isn't a good earth, the imbalance could
be a risk.

** There is always a good "earth"  available  - courtesy of the water mains
in the street being linked to neutral at every premises.

.....  Phil

All new construction [last 30 years] around here uses iron mains with
rubber sealed joints and plastic service pipe into all homes, so there
is NO bond from the house to the main. The Gas main is plastic, as are
the service drops. So, the only earth connection is the rather 'iffy'
pair of 8' ground rods usually in the rain shadow of the roof
overhang.

Neil S.

 

[terryc]

On Tue, 24 Nov 2009 11:10:26 +1100, Sylvia Else wrote:

the net result would be a
large overvoltage on one set of appliances.

It would be across both sets, but......

My electrician says it's not an issue, but I can't see why.

The neutral is actually grounded to the earth for such a case; hence MEN
(Multiple Earth Neutral), so the neutral would actually travel through
the ground to your neighbours earth stake and back into the neutral phase
there.

If the USA Godzilla remake is to be believed, all your earth worms will
come to the surface as an indicator, (or is that only for correct DC
connections?).

If you are worried about such an event happening, dump a bucket of wter
on your earth stake quarterly and encourage your neighbours to do the
same.

 

[scarborofun]

Allodoxaphobia wrote:

On Tue, 24 Nov 2009 09:28:48 +0800, TonyS wrote:
Sylvia Else wrote:
I have to phases of power supply to my house - so three power lines, two
phases plus neutral.

I've on occasion wondered what would happen if we lost the neutral line.
It seems to me that we'd then have the voltage between the two phases
across two sets of appliances, one set attached to one phase, and the
other set attached to the other phase, with the two sets in series as a
result of their common connection to the neutral wire. Since the two
sets are unlikely to represent equal loads, the net result would be a
large overvoltage on one set of appliances.

My electrician says it's not an issue, but I can't see why.

Any thoughts?
I had exactly this happening two years ago.
My supply has 3 phases ... <-snip-

Oh?? Really?!?!

Yes, why??

 

[kreed]

On Nov 24, 12:40 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

"kreed"

From what I can gather, pretty much every home in the US has a 120v -
0 - 120v system where the 2x 120v's are 180 degrees out of phase.
Between the 2 phases 240v is available for stoves, air conditioners
etc.

In Australia, most separate homes have a straight single phase 240v
supply, its not common for there to be 2,3 separate phases to the
average house. Therefore the scenario Sylvia mentions is less likely
to occur, as not many people have this multi phase system.

The exception here could be blocks of flats, if the main neutral to
the building fails, and there isn't a good earth, the imbalance could
be a risk.

** There is always a good "earth" available - courtesy of the water mains
in the street being linked to neutral at every premises.

..... Phil

That is true in a lot of cases, however I have noticed with a lot of
newer houses, (in QLD anyway) they are using some kind of either black
or grey pvc or poly pipe for home water mains. To make it worse, it
looks to me to be "crimped" together at joins, sometimes with what
look like soft metal rings but not always.

Copper or the old cast iron pipes would provide an excellent Earth,
and excellent soil electrical contact due to the enormous surface area
of the water main in contact with the soil over distance



Mine is all copper, all the way back to the water main, so no problems
here.

 

[Jasen Betts]

On 2009-11-24, Sylvia Else <sylvia@not.at.this.address> wrote:

Phil Allison wrote:
In Australia, AC power delivery uses a system called " Multiple Earth
Neutral " - which requires that the neutral conductors in a premises be
connected to the plumbing system at the distribution board (ie power box).
It also requires that an earth stake be installed for the same purpose, but
some older premises may not have this.

If as you say, neutral has to be tied to Earth at the premises, then I
can indeed see that the situation might not be so bad.

On the face of it, having significant current flowing from neutral to
Earth would have to indicate a fault. It would be nice for the breakers
to trip in such a situation, but I can't see that they will.

Having the breakers trip because a faulty neutral in an neighbours
house (which would cause his neutral current to flow through his earth and
your earth (etc) to the common neutral) could be an annoyance.

bye.