Parents-in-law house suffered a power "incident" the other day that
damaged computers, TV, radios, and electric showers. Cabling was
blackened as was the fuse box.

The power supply company say it was an internal fault and certainly no
other houses appear affected. The only clue I have is that light bulbs
brightened before they burnt out, suggesting an over-voltage condition.

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

I can't think of anything that could have raised the voltage on the live
conductor. Could it be that their electric distrubution system
mainatins neutral substantially above earth such that a short of neutral
to earth would raise the voltage applied across appliances?

Any informed speculation welcome.

ian
....

On Tue, 08 Apr 2008 00:03:33 +0100, Ian Worthington wrote:

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

Are you sure? I'm under the impression that supplies across the pond are
110v bi-phase. So things that things that need real amounts of power can
sit across the phases and live off 220v.

--
Cheers
Dave.

Dave Liquorice wrote:
On Tue, 08 Apr 2008 00:03:33 +0100, Ian Worthington wrote:

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

Are you sure? I'm under the impression that supplies across the pond are
110v bi-phase. So things that things that need real amounts of power can
sit across the phases and live off 220v.


No, I'm not! I know they do that in the US so its very possible that
its the case in Colombia too, but as far as I know there's no 220V
service in their house -- certainly no appliances that use it.

If there was, can that fail in such a way as to present a much higher
voltage across the appliances?

i

On Tue, 08 Apr 2008 00:03:33 +0100, Ian Worthington wrote:

Parents-in-law house suffered a power "incident" the other day that
damaged computers, TV, radios, and electric showers. Cabling was
blackened as was the fuse box.

The power supply company say it was an internal fault and certainly no
other houses appear affected. The only clue I have is that light bulbs
brightened before they burnt out, suggesting an over-voltage condition.

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

I'm assuming you mean central America. The nominal voltage there is
110/220v. The 220v supply is for equipment with higher loads, like cookers.

I had a quick look on line for details about the supply industry in
Colombia, there were *lots* of references to the business aspects, but I
drew a blank on tech aspects. I'm guessing the lv distribution system is
split phase, 110-0-110, with the centre point being connected to earth
(call it neutral for the sake of convenience). I somehow don't think it
would be 0-110-220, but you never know!

What I suspect happened, somewhere between your in-laws house and the
transformer there was a break in the neutral. That caused the voltages
across the outers to differ wildly depending on the loads connected.

What you need to ask your in-laws, do they have only a 110v supply or do
they have 110/220. If they have 110/220, there's always a possibility that
the problem could have occured on their wiring. If they are positive they
only have 110v, the laws of physics dictate that the problem could *not*
have occured within their property. It would have to be a problem on the
system supplying them. Proving liability with the supply co is altogether
another matter.

--
the dot wanderer at tesco dot net

In article ,
Ian Worthington writes:
Dave Liquorice wrote:
On Tue, 08 Apr 2008 00:03:33 +0100, Ian Worthington wrote:

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

Are you sure? I'm under the impression that supplies across the pond are
110v bi-phase. So things that things that need real amounts of power can
sit across the phases and live off 220v.


No, I'm not! I know they do that in the US so its very possible that
its the case in Colombia too, but as far as I know there's no 220V
service in their house -- certainly no appliances that use it.

If there was, can that fail in such a way as to present a much higher
voltage across the appliances?

Yes, and it's not at all uncommon with the 120-0-120V supplies.
Loss of the neutral connection means the 0V drifts in reverse
proportion to the load on each side. If the loads on the two
sides were nowhere near ballanced at the time, then one side
(with the lighter load) will have had a significantly higher
voltage than the 120V it's designed for (and the other side
will have an equal drop).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Tue, 08 Apr 2008 09:08:04 +0100, The Wanderer wrote:

Proving liability with the supply co is
altogether another matter.


But it's probably common enough that there are lawyers and electrical
engineers with experience of fighting such cases and that possibly,
approached by such professionals, the leccy co may cough up.

--
John Stumbles

Bob the builder / it'll cost 'yer
Bob the builder / loadsa dosh

Ian Worthington wrote:
Parents-in-law house suffered a power "incident" the other day that
damaged computers, TV, radios, and electric showers. Cabling was
blackened as was the fuse box.

The power supply company say it was an internal fault and certainly no
other houses appear affected. The only clue I have is that light bulbs
brightened before they burnt out, suggesting an over-voltage condition.

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

I can't think of anything that could have raised the voltage on the live
conductor.

Many things. lighning strike, disconneting an indctive load. Losing a
phase on a three phase.


Could it be that their electric distrubution system
mainatins neutral substantially above earth such that a short of neutral
to earth would raise the voltage applied across appliances?

Any informed speculation welcome.

ian
...

On Apr 8, 12:41*pm, The Natural Philosopher wrote:
Ian Worthington wrote:
Parents-in-law house suffered a power "incident" the other day that
damaged computers, TV, radios, and electric showers. *Cabling was
blackened as was the fuse box.

The power supply company say it was an internal fault and certainly no
other houses appear affected. *The only clue I have is that light bulbs
brightened before they burnt out, suggesting an over-voltage condition.

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

I can't think of anything that could have raised the voltage on the live
conductor. *

Many things. lighning strike, disconneting an indctive load. Losing a
phase on a three phase.

Could it be that their electric distrubution system



mainatins neutral substantially above earth such that a short of neutral
to earth would raise the voltage applied across appliances?

Any informed speculation welcome.

ian
...- Hide quoted text -

- Show quoted text -

Since the voltage is mentioned as 110 volts suspect it is similar to
here in Canada (as in much of the Americas) where we have 115-0-115
volts 'single phase'.

That means that there is 230 volts (the two ends of a centre tapped
distribution transformer winding) i.e. between the two outer wires, as
someone has already described.

So if that middle wire. The one that is called 'neutral' and nominally
at zero volts becomes open , either outside or within the house due a
fault such as corroded or loose connection it is possible that 115 +
115 = 230 volts could be impressed through various devices across a
115 volt device.

With twice the intended voltage there is twice the required current
and that means four times the amount of power being dissipated in any
device or equipement that might be switched on at that time! Have seen
that blow smithereens out of TV set.

Whether there IS a bad neutral connection outside or inside will have
to determined; but it could happen again?

Dont know about Colombia but electric utilitiy crews in most countries
pride themselves on a high standard of customer service. Here in this
part of Canada they are are excellent, providing repairs 24 hours a
day during the worst of weather. And usually willing to come and test
the outside connections to a residence, sometimes giving a bit of
advice about testing into the house circuit breaker panel or CU.

We take out hats off the the outside line crews of the Newfoundland
Light and Power Company and Newfoundland Hydro.

Hi Andy.

Thanks for this, and to all who responded.

Fault was confirmed as a disconnected neutral, but apparently inside the
house, so no claim against Codensa. Caused by ingress of rain I'm told.

Two questions:

1. If the neutral gets disconnected, what's the return path for the
current?

2. Luckily my teenage sister-in-law had taken it upon herself to
disconnected the most expensive of the white goods (fridges and washing
machines cost a small fortune out there) and forget to plug them back in
before this fault occurred, so saving them. But, given my
father-in-law's apparently not to be trusted with mains wiring, what
type of safety equipment should I insist is fitted to protect people and
property before I put my hand in my pocket to replace the other damaged
equipment?

ian
....


Andrew Gabriel wrote:
In article ,
Ian Worthington writes:
Dave Liquorice wrote:
On Tue, 08 Apr 2008 00:03:33 +0100, Ian Worthington wrote:

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.
Are you sure? I'm under the impression that supplies across the pond are
110v bi-phase. So things that things that need real amounts of power can
sit across the phases and live off 220v.

No, I'm not! I know they do that in the US so its very possible that
its the case in Colombia too, but as far as I know there's no 220V
service in their house -- certainly no appliances that use it.

If there was, can that fail in such a way as to present a much higher
voltage across the appliances?

Yes, and it's not at all uncommon with the 120-0-120V supplies.
Loss of the neutral connection means the 0V drifts in reverse
proportion to the load on each side. If the loads on the two
sides were nowhere near ballanced at the time, then one side
(with the lighter load) will have had a significantly higher
voltage than the 120V it's designed for (and the other side
will have an equal drop).

In article ,
Ian Worthington writes:
Hi Andy.

Thanks for this, and to all who responded.

Fault was confirmed as a disconnected neutral, but apparently inside the
house, so no claim against Codensa. Caused by ingress of rain I'm told.

Two questions:

1. If the neutral gets disconnected, what's the return path for the
current?

Through the appliances on the other leg.

2. Luckily my teenage sister-in-law had taken it upon herself to
disconnected the most expensive of the white goods (fridges and washing
machines cost a small fortune out there) and forget to plug them back in
before this fault occurred, so saving them. But, given my
father-in-law's apparently not to be trusted with mains wiring, what
type of safety equipment should I insist is fitted to protect people and
property before I put my hand in my pocket to replace the other damaged
equipment?

Safety equipment is heavily dependant on local customs, what's
available, and local regulations. I think you need to ask this
in a Canadian or North American forum. That type of fault is so
rare in the UK that over-voltage trips are never used in domestic
situations. However, that type of fault is very much more common
on North American 120-0-120V (Edison) type supplies, and there
may be equipment and/or procedures which are used to minimise the
incidence or impact of it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 09 Apr 2008 14:39:22 GMT, Andrew Gabriel wrote:

In article ,
Ian Worthington writes:
Hi Andy.

Thanks for this, and to all who responded.

Fault was confirmed as a disconnected neutral, but apparently inside the
house, so no claim against Codensa. Caused by ingress of rain I'm told.

Two questions:

1. If the neutral gets disconnected, what's the return path for the
current?

Through the appliances on the other leg.

Hmm, but the OP had already said that he thought it was a 110 volt supply,
not a 110/220 volt supply. That being the case, there is no return path and
the problem could not have occured in the property, and Codensa are
spinning the FiL a line. Hence my question/comment to the OP that he needs
to establish if it is 110v 2 wire or 110/220v 3 wire.

2. Luckily my teenage sister-in-law had taken it upon herself to
disconnected the most expensive of the white goods (fridges and washing
machines cost a small fortune out there) and forget to plug them back in
before this fault occurred, so saving them. But, given my
father-in-law's apparently not to be trusted with mains wiring, what
type of safety equipment should I insist is fitted to protect people and
property before I put my hand in my pocket to replace the other damaged
equipment?

Safety equipment is heavily dependant on local customs, what's
available, and local regulations. I think you need to ask this
in a Canadian or North American forum. That type of fault is so
rare in the UK that over-voltage trips are never used in domestic
situations.

I agree, it is rare, but I've come across a couple of instances of a
floating star point.

--
the dot wanderer at tesco dot net

Andrew Gabriel wrote:
In article ,
Ian Worthington writes:
Hi Andy.

Thanks for this, and to all who responded.

Fault was confirmed as a disconnected neutral, but apparently inside the
house, so no claim against Codensa. Caused by ingress of rain I'm told.

Two questions:

1. If the neutral gets disconnected, what's the return path for the
current?

Through the appliances on the other leg.

This would surely suggest that the house *must* have both legs of the
120V supply available contrary to what I've been told?


2. Luckily my teenage sister-in-law had taken it upon herself to
disconnected the most expensive of the white goods (fridges and washing
machines cost a small fortune out there) and forget to plug them back in
before this fault occurred, so saving them. But, given my
father-in-law's apparently not to be trusted with mains wiring, what
type of safety equipment should I insist is fitted to protect people and
property before I put my hand in my pocket to replace the other damaged
equipment?

Safety equipment is heavily dependant on local customs, what's
available, and local regulations. I think you need to ask this
in a Canadian or North American forum. That type of fault is so
rare in the UK that over-voltage trips are never used in domestic
situations. However, that type of fault is very much more common
on North American 120-0-120V (Edison) type supplies, and there
may be equipment and/or procedures which are used to minimise the
incidence or impact of it.


Local customs in this area of town mainly consist of throwing a coat
hanger over the cables in the street to steal some power whilst trying
to not let it get too close to the petrol-powered cooking stove, (for
example,
http://isw.me.uk/gallery/v/colombia/...2_enterAlbum=0
et al (taken about a mile from my parents in law's house)) so that's
probably not a good starting point....

I'm trying to suggest to the wife we need to talk to an electrician who
knows what they're doing, and she's wondering just how to do this
without upsetting her father... I'm in the dog house at the moment for
plain speaking. Family politics, don't ya just luv it?

i

Ian Worthington wrote:
Andrew Gabriel wrote:
In article ,
Ian Worthington writes:
Hi Andy.

Thanks for this, and to all who responded.

Fault was confirmed as a disconnected neutral, but apparently inside
the house, so no claim against Codensa. Caused by ingress of rain
I'm told.

Two questions:

1. If the neutral gets disconnected, what's the return path for the
current?

Through the appliances on the other leg.

This would surely suggest that the house *must* have both legs of the
120V supply available contrary to what I've been told?


Hi Andy.

I've had it confirmed that the cable from the street carries only one
live plus neutral and earth.

Any ideas?


i

In article ,
Ian Worthington writes:
Ian Worthington wrote:
Andrew Gabriel wrote:
In article ,
Ian Worthington writes:
Hi Andy.

Thanks for this, and to all who responded.

Fault was confirmed as a disconnected neutral, but apparently inside
the house, so no claim against Codensa. Caused by ingress of rain
I'm told.

Two questions:

1. If the neutral gets disconnected, what's the return path for the
current?

Through the appliances on the other leg.

This would surely suggest that the house *must* have both legs of the
120V supply available contrary to what I've been told?


Hi Andy.

I've had it confirmed that the cable from the street carries only one
live plus neutral and earth.

Any ideas?

In which case the raised voltage was fed to you by the power
company, and I would regard that as their fault. I presume
the other leg feeds someone else, in which case the disconnected
neutral must have been at the supply transformer. A disconnected
neutral inside your house cannot do this.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

The Natural Philosopher wrote:
Ian Worthington wrote:

Parents-in-law house suffered a power "incident" the other day that
damaged computers, TV, radios, and electric showers. Cabling was
blackened as was the fuse box.

The power supply company say it was an internal fault and certainly no
other houses appear affected. The only clue I have is that light bulbs
brightened before they burnt out, suggesting an over-voltage condition.

This took place in Colombia, not the UK, and the house didn't have
anything more sophisticated in the way of protection than a fuse box.
110V, almost certainly single phase.

I can't think of anything that could have raised the voltage on the live
conductor.

Many things. lighning strike, disconneting an indctive load. Losing a
phase on a three phase.


Could it be that their electric distrubution system
mainatins neutral substantially above earth such that a short of neutral
to earth would raise the voltage applied across appliances?

Any informed speculation welcome.

ian
...

It doesnt seem to me that the symptoms you describe line up well
with a 110-220v overvoltage fault. Such fault would cause
connected appliances to draw excess current, and the fusebox
would clear this in the normal way. You'd have dead appliances
and popped fuses, but nothing else. The currents involved would
not usually be high enough to blacken fusebox & wiring.

Charring of cable requires either huge current (dead short on
premises, PSCC flows, CU fails to clear fault due to inadequate
breaking capacity) or huge voltage (lightning strike or high voltage
flashover on power company's side)

The next question is where is the cable blackened. This will tell
you if the charring occurred only in the CU (1), or only along one
attached cable (2), or through out the whole installation (3).

1 means charring temps only occurred in the CU, which rules out
lightning
2 means the fault occurred downstream on one cable, so a dead
short.
3 means extreme voltage at the feeder, ie lightning, or I guess less
likely a flashover at the pole pig.

Once you've established here what the fault was, then getting the
cause confirmed in writing by a qualified spark would give you
evidence to argue with. If its excess voltage, they would also need
to confirm that it could not have been caused by anything on the
premises.

Re safety equipment, I dont think there is any for any of the
possible scenarios, including lost neutral.


NT