Girl in critical condition after fault earth electric shock

[amyk]

"According to PerthNow, Ms Harrison had reported other power problems at the home in recent months including a “burning electrical smell” where an electrician was unable to find a cause."

I would go find another electrician if that happened, preferably one with a thermal camera.

If no one got shocked, I wouldn't be surprised if a fire broke out soon afterwards. The smell of ozone (arcing) and things getting hot is very distinctive and definitely warrants immediate attention.

[grumpydoc]

I just can't figure it out though. If you turn the main on and get a shock from the meter box, wouldn't you turn it back off again?

You might do but for this type of fault that may well not help.

If the "earth" coming into your building is 230V above true earth and you then connect yourself between the two you are going to be in trouble.

The fuse panel switch in most installations isolates phase & neutral, why would it disconnect earth (in normal conditions).

[BradC]

You and I might, we are used to HV zaps and everything related to them, but she was a young girl.

Her mother copped the first shock off the meter box. She then copped another whopper trying to pull her daughter off the tap.
You're right however, in that your average punter just doesn't have the experience to know what to do.

All in all a tragic situation.

[Mechatrommer]

.. the pipe is earthed. If you lose the earth..

and what moron connected earth return wiring to water piping?

Why *wouldn't* you bond your pipework? It's buried in the dirt, it often connects to an electric hot water system (which is earthed) and it gives more earth surface area than the earth stake.

any underground or buried electrical wiring should be insulated with pvc piping, and have dedicated earth wiring, not tapping through water tap. any wiring before meter should call for armored cable. we are talking about australia here, not south africa or remote place in malaysia. geez i'm really surprised.

[BradC]

any underground or buried electrical wiring should be insulated with pvc piping, and have dedicated earth wiring, not tapping through water tap. any wiring before meter should call for armored cable. we are talking about australia here, not south africa or remote place in malaysia. geez i'm really surprised.

Right. You appear to have the wrong end of the stick.
We are talking about *bonding* our plumbing to the building earth, not using the plumbing as an earth itself (although pre early 70's apparently that was legal. I was too young and my earliest copy of AS3000 is considerably younger than that).

The process of bonding the plumbing means any buried pipework becomes an effective part of the earth stake. It's not used as any interconnection of the earth system. All sub-surface wiring is either in direct burial rated cable or in conduit, and all circuits should carry their own earth.

[sibeen]

The fuse panel switch in most installations isolates phase & neutral, why would it disconnect earth (in normal conditions).

Not in Australia. The main switch into an installation only disconnects the active conductor(s).

[Brumby]

The fuse panel switch in most installations isolates phase & neutral, why would it disconnect earth (in normal conditions).

Not in Australia. The main switch into an installation only disconnects the active conductor(s).

... and I've never seen it any other way in residential installations.  Neutrals from the house all run to a neutral link in the meter box and out to the street neutral.  No switching.  The earth connections are also permanently connected.  The only thing fused and switched are the active lines.



This is the tap everybody seemed interested in....

[dmills]

And that bonding is a GOOD thing, until one very specific type of (very rare) fault happens AND you form the bridge between the bonded "Earthed" pipework and true earth, whereupon current flows and bad things happen (Having it happen while using a hose pipe and probably having wet hands is just a perfect storm).

This is not using the pipework as a deliberate fault current carrying conductor, this is bonding the pipework to the "earth" conductor so that in the event of a fault raising the "earth" conductor touch voltage you cannot be shocked by getting between say the washing machine (Grounded to the "Earth conductor") and the sink (Grounded to the pipework and external earth via the plumbing), it works well UNTIL you manage to bridge the stuff bonded to the "Earth conductor" and true earth.

Very, very unfortunate.

Power electrics and its FMEA is tricky stuff, be careful out there, and yes, this is one of the more obscure failure cases, because switching off the main breaker will quite likely NOT make things safe.

That tap is a classic case of exporting the equipotential zone outside the building, very common, also very wrong, but plumbers are not generally electricians.
Unfortunately the building regs often do not exhibit particularly joined up thinking about these kinds of things, and you can see a plumber not seeing a problem with this (Apart from the cack handed pipework).

Regards, Dan.

[grumpydoc]

The fuse panel switch in most installations isolates phase & neutral, why would it disconnect earth (in normal conditions).

Not in Australia. The main switch into an installation only disconnects the active conductor(s).

Slightly surprised that the main isolator is not DP** but if those are the Australian Regs then those are the regs.

As far as I know it's:

DP in the UK with SP on individual circuits
DP in France with DP on individual circuits

** For single phase, obviously

[Monkeh]

That tap is a classic case of exporting the equipotential zone outside the building, very common, also very wrong, but plumbers are not generally electricians.
Unfortunately the building regs often do not exhibit particularly joined up thinking about these kinds of things, and you can see a plumber not seeing a problem with this (Apart from the cack handed pipework).

As far as I'm aware, at least over here, taps like that are not forbidden in PME installations due to the limited risk of the fault condition occuring simultaneously with use of the tap. It's certainly not ideal, though.

The trouble is, the solutions involve plastic pipework (not very robust) or changing the earthing system (an immense pain which can also leave you with some of the greater flaws of a TT system).

[james_s]

The thing that surprises me is that she remains in critical condition. I figured when it comes to electric shocks, either you're dead before you hit the ground, or you walk away shaken but otherwise ok.

[Monkeh]

The thing that surprises me is that she remains in critical condition. I figured when it comes to electric shocks, either you're dead before you hit the ground, or you walk away shaken but otherwise ok.

Unfortunately there are other damage modes. If it doesn't kill you by inducing VF you can be sat there electrically heating your organs for a while. Various other damage to the heart can be caused without inducing VF. External burns can be quite severe.

Considering the state of that tap, I don't think the wording of the original article is quite correct. It looks like she ripped that tap off the wall - it was no simple touch.

[james_s]

Ick, reminds me of an activity we did in elementary school cooking hotdogs with electricity, they tasted rather bad but it was fun. I doubt anyone would get away with such an activity these days.

[sokoloff]

Ick, reminds me of an activity we did in elementary school cooking hotdogs with electricity, they tasted rather bad but it was fun. I doubt anyone would get away with such an activity these days.

We used to clip "leads" from pencils to the AC outlets in electrical shop in industrial arts to make very short-lived incandescent filaments. (We didn't exactly "get away with it" back then either...)

[Macbeth]

Terrible of me to say, and I am only speculating, but perhaps "goldie lookin' chain" there may have been tampering with the upstream from the meter without his mum knowing, perhaps for some educational attic horticulture project for example? Maybe someone tapping behind the meter to run all those grow lamps messed up the wiring, could that cause such a fault? 

[Monkeh]

Terrible of me to say, and I am only speculating, but perhaps "goldie lookin' chain" there may have been tampering with the upstream from the meter without his mum knowing, perhaps for some educational attic horticulture project for example? Maybe someone tapping behind the meter to run all those grow lamps messed up the wiring, could that cause such a fault? 

Who? The only people shown are an 11 year old girl and her mother..

[Macbeth]

Who? The only people shown are an 11 year old girl and her mother..

Lad in this video here: http://www.abc.net.au/news/2018-03-05/denishar-woods-remains-in-critical-condition-after-electric-sho/9510242

Whatever or whoever is the cause, I do hope the poor girl recovers.

[Monkeh]

Oh. Well, okay, he's a bit suspect.

[Electro Detective]

Give me a couple of hours to go through the lot and find the issue/s that caused this, and FIX IT (yes we can...)

It will be a combo of suss wiring, earthing and maybe a flip wired or cheater DIY extension cord or two,
perhaps faulty stuff plugged in, usually a combo of everything done wrong 

It may even be something from neighbouring properties too, something on the ground/mud/pool etc 


I hope the girl pulls through ok
and learns the electrical trade to be a proper sparkie
to do electrical contrator work properly at fair rates for the many clueless women out there that have faith in suss male DIYers and unqualified pretend sparkie tradies that do halfassed inspections and cash grab slap bang work,

...so they can quickly scurry back to their no-life 'pot n pokies' addiction and talk sports BS with their mates   

[vk6zgo]

Ick, reminds me of an activity we did in elementary school cooking hotdogs with electricity, they tasted rather bad but it was fun. I doubt anyone would get away with such an activity these days.

Back in the 1960s there was a device commercially available in Oz to do just that!
It didn't use raw Mains, though.
It had a big fat transformer with the secondary ending in a couple of spikes.

The customer would come in, order  a hot dog, the shopkeeper would grab a pre packaged sausage in a roll, push it onto the spikes, & "lo & behold" several minutes later, there was your meal.
All that was then necessary was to squirt some sauce on it, & the customer went on their way.

They didn't taste too bad, although the charred holes in the roll took a bit of getting used to!

[Macbeth]

Ick, reminds me of an activity we did in elementary school cooking hotdogs with electricity, they tasted rather bad but it was fun. I doubt anyone would get away with such an activity these days.

Back in the 1960s there was a device commercially available in Oz to do just that!
It didn't use raw Mains, though.
It had a big fat transformer with the secondary ending in a couple of spikes.

The customer would come in, order  a hot dog, the shopkeeper would grab a pre packaged sausage in a roll, push it onto the spikes, & "lo & behold" several minutes later, there was your meal.
All that was then necessary was to squirt some sauce on it, & the customer went on their way.

They didn't taste too bad, although the charred holes in the roll took a bit of getting used to!

There was a 70's USA device called the Presto Hot Dogger. This was a consumer device with two racks of spikes between live and neutral.



Perhaps something Big Clive should get his hands on. Try it with and then without his step down transformer 

[james_s]

Hah! That's pretty cool!

In my case it was the teacher that brought in the setup, as I recall we used a couple of screwdrivers as terminals, with a clothes iron in series as a ballast, direct off the 120V mains. The middle part of the hotdog tasted fine, but the holes in the ends had a funny taste as I recall. I also remember there was a book of science experiments in the school library, probably from the 1950s or so. One of the projects in it was a hotdog cooker which consisted of a board with a couple of nails through it connected to a power cord. Kids aren't allowed to do anything fun anymore.

[BillB]

Tragic electrocution story all the way to hot dog cookers within 3 pages!  God bless internet forums!

[IanMacdonald]

Here in the UK they're talking about going over to double pole circuit breakers for individual circuits. I think this is stupid, and will likely lead to accidents. The best thing for the neutral is to remain connected to the system earth. If it is disconnected, it becomes a floating conductor which can acquire a voltage from, for example, water in switchgear. That, and failure of the neutral contacts in the breaker leaves you with a circuit which the load stops working and appears dead, but in which ALL parts of the circuit are actually live. 

IMHO the only times double pole switching should be used are on center-tap feeds such as USA 240v, bench isolating transformer outputs, and for master supply  isolators. Master isolators should be such as to provide positive disconnection of both poles (If either contact fails to open the lever will not go fully over to the off position, so the operator is aware that the circuit is not safe.)

In the 1930's they used to fuse the neutrals, and it was learned that this created a far greater hazard than if not fused. Old mistakes get repeated..

[james_s]

Is there a reason given for considering double pole breakers on a single phase feed? Here in the US the only time you see double pole breakers is on 240V loads that straddle both rails of the split phase panel. Since a US-style 240V circuit consists of two hots you obviously need a double pole breaker, but I can't think of a good reason for running the neutral through the breaker. Surely there's some supposed benefit to the proposal?