Girl in critical condition after fault earth electric shock - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: March 05, 2018, 09:21:14 am
content: http://www.watoday.com.au/wa-news/perth-girl-remains-in-critical-condition-as-investigations-into-electric-shock-continue-20180305-h0x1ju.htmlQuote

author: dmills
author_rank: Super Contributor
timestamp: March 05, 2018, 11:22:18 am
content: Ouch!Earth exported from the equipotential zone in a TN-C-S install, then an upstream neutral fault from the sound of things.Not common, but it can happen, which is why you are really not supposed to do that, but a plumber fitting an outside tap will generally not spot the danger.Regards, Dan.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 05, 2018, 12:05:30 pm
content: Quote from: dmills on March 05, 2018, 11:22:18 amOuch indeedQuoteSo, what's the fault current path? - from live, via equipment neutral/earth to (presumably) "earthed" tap thence to true ground?Seems almost unreasonable to expect a plumber to be aware of the risk.

author: station240
author_rank: Unknown
timestamp: March 05, 2018, 12:15:09 pm
content: https://www.9news.com.au/national/2018/03/04/21/31/perth-girl-fighting-for-life-after-electric-shock-at-home"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.""She claims she reported a problem with the electricity at the public housing property to the Department of Housing, about an hour before her daughter was shocked"http://www.abc.net.au/news/2018-03-05/denishar-woods-remains-in-critical-condition-after-electric-sho/9510242"She said her organs reached 38 degrees Celsius and she was on a cooling pad in hospital to try to limit the damage.""Ms Harrison she was out watering in the garden on Saturday night when the power to the house went out.When she went to the meter box to turn the power back on, she received a small electric shock.She said she contacted the Department of Housing emergency contact line to notify them of the fault, but she said no one warned her not to touch anything."Someone in the Department of Housing (WA) NEEDS to go to jail for this shit.All the warning signs were there that the house was live at mains voltage.The power went out because the Neutral was completely disconnected due to a fault, possibly underground. When the running tap was touched the circuit was completed, earth on house (tap) to ground, to earth in street power cabling.related storieshttp://www.abc.net.au/news/2018-03-05/what-causes-taps-to-be-electrified/9508664What could have been done ?1) Touch nothing on, in or attached to the house.2) Switch off the main breaker, using an insulating material, like a length of timber, plastic rod etc.3) Properly investigate the original complaints, months ago, and fix it before be became lethal.4) Report a live meterbox to the power company, who will warn of the dangers and rush out to make it safe.Here is hoping the girl and her mother are OK, longer term.

author: station240
author_rank: Unknown
timestamp: March 05, 2018, 12:24:36 pm
content: Quote from: grumpydoc on March 05, 2018, 12:05:30 pmIn Australia, there are multiple Earth stakes and Neutral to Earth ties.The house has 1 earth stake and one jumper between that Earth and Neutral. Same for power poles (metal ones anyway), transformers, and underground cable junctions.So a broken Neutral between the house and street, leaves the only return path as being the ground via two earth stakes. The copper water pipe with running water was a lower resistance current path, just needed a human to complete it. Active is fuse for 80amps for the meter, so everything drawing power in the house was using that completed circuit.

author: dmills
author_rank: Super Contributor
timestamp: March 05, 2018, 12:44:36 pm
content: Quote from: grumpydoc on March 05, 2018, 12:05:30 pmThat's the one, it is even nastier then it sounds because if the fault is somewhere upstream, even switching off the incoming isolator will not make it safe, that switch isolates live and neutral in the -S part of the arrangement, but the fault lies in the combined neutral/earth -C- part and so other loads will still drive the local 'earth' away from the ground.UK practise is that there is a ground rod at every house in these installations (As well as, in theory, at every buried cable junction) so as to limit the voltage rise in the event of this fault (Multiple earthed neutral), but a combination of lost neutral and touching a metal fitting outside the zone with (probably) wet hands, while on wet ground, just OUCH!Within the house all the exposed metal is supposedly firmly bonded together (Pipes, taps, the bath) by fairly butch conductors to ensure that even in the event of such a fault it is not possible to get between it and a low impedance ground (This is the equipotential zone), but an outside tap on metal pipework, yea that's harsh.These systems are actually not an unreasonable design choice as they are actually significantly safer MOST of the time then TT systems (Separate earth relying on a rod) which can wind up with such a high loop impedance that even a 100mA RCD will not trip on a fault. TN-S (Totally separate earth back to the transformer) is usually cost prohibitive (and has some issues of its own).Incidentally, TN-C-S is a pain when you are a radio ham and thus want lots of wire outside the zone....Regards, Dan.

author: sokoloff
author_rank: Super Contributor
timestamp: March 05, 2018, 01:02:20 pm
content: Quote from: station240 on March 05, 2018, 12:15:09 pmWho? The person who took the call that an occupant reported a shock when resetting a circuit breaker? Is that person expected to be qualified to know, from a telephone report, of the condition at the property? That's expecting WAY too much out of a call center agent, IMO.

author: senso
author_rank: Frequent Contributor
timestamp: March 05, 2018, 01:13:09 pm
content: Would plastic water pipes prevent this?I know that water is a conductor, but that as good as a metal pipe, also, why would the girl get shocked if the metal pipe is buried, so it should have better earthing than someone standing on grass with shoes.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: March 05, 2018, 01:16:20 pm
content: The EXACT same thing happened to me when I was a kid.I'd been playing with the garden hose, soaking wet ground, bare feet. Went to turn off the garden tap and got a huge electric shock. I couldn't let go and was stuck there while my friend ran to get my mum who kicked me off the tap. It affected our whole neighbourhood.Fortunately I'm right handed so most of the current would have flowed down my right side, away from my heart. I could very easily have been killed.

author: sokoloff
author_rank: Super Contributor
timestamp: March 05, 2018, 01:53:25 pm
content: Quote from: senso on March 05, 2018, 01:13:09 pmI imagine the metal pipe was service from the house, not a buried pipe. Imagine a pipe that goes through the basement and emerges at a hose bib a few feet above ground on the outside of the house.

author: dmills
author_rank: Super Contributor
timestamp: March 05, 2018, 02:38:34 pm
content: A foot or two of plastic pipe going thru the wall will at least make this particular fault much less nasty, still tickle a bit probably, but you would not get the kind of current that causes a serious increase in temperature in a human body, tap water is not usually that conductive.I await a report of what actually happened with interest, because while a TN-C-S neutral screwup seems most likely, we don't actually know.Regards, Dan.

author: jordanp123
author_rank: Regular Contributor
timestamp: March 05, 2018, 06:17:56 pm
content: I'm unfamiliar with the Australian regulations but I'm going to assume their close to the same as the us in this regard (Neutral and ground bonded at Utility pole then only neutral and power coming to the house - then neutral and ground bonded again in the main panel- With the water also grounded from the house ground). I've gotten a zing before on the actual ground rods, utility neutral burnt open for a overloaded neutral, sometimes you'll also see the TV lines getting hot and melting due to the alternate current path.

author: dmills
author_rank: Super Contributor
timestamp: March 05, 2018, 06:27:56 pm
content: Don't forget that most of 230V land does not do either split phase or one transformer per customer, so the lost (or high Z) neutral tends to have a fair bit more bite to it depending on exactly where the fault occurs.Not that this is a common fault in a TN-C-S install, you hear about roughly one or two a year, and it is usually obvious when it happens on a three phase feed as the neutral wanging around makes stuff see all sorts of random voltages and lots of stuff usually blows up. Often the root cause is copper thieves removing the neutral bar at the local sub station!This one feels like a fail on a single phase setup, but who really knows until someone publishes a proper report?Regards, Dan.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 05, 2018, 07:02:17 pm
content: too much speculation... for whatever reason (be it neutral or live), how can electricity touches water pipe in the first place? if anyone has to go to jail, its the person who made the installation.

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2018, 07:26:45 pm
content: Quote from: dmills on March 05, 2018, 12:44:36 pmAh.. no, not really. Rods are generally not used with TN-C-S supplies.Quote from: Mechatrommer on March 05, 2018, 07:02:17 pm.. the pipe is earthed. If you lose the earth..

author: metrologist
author_rank: Super Contributor
timestamp: March 05, 2018, 07:54:35 pm
content: My house cold water supply became disconnected from earth at the supply - because a plastic supply line replaced the old galvanized pipe. I believe it was acceptable to attach ground to a cold water pipe within the dwelling. A failed neutral and other short to live could energize all of the water taps. Fortunately, the supply is still connected to long outside runs to irrigation. Also, the electricity was rewired in time to require an additional ground rod at the water supply - where the panel is required to be grounded to the water supply pipe. I still do not like it, but that appears to be the code.

author: dmills
author_rank: Super Contributor
timestamp: March 05, 2018, 09:01:58 pm
content: The water pipes inside the house form part of the equipotential bonding network (That is they are all wired firmly together and connected to the suppliers "Earth terminal"). This bonding ensures that even if something bad happens to the combined earth/neutral people inside the house are reasonably safe because everything they touch is at the same potential.That "Earth terminal is really a connection to the suppliers neutral conductor which should be firmly bonded to earth at multiple points.My suspicion (Without really adequate evidence) is that the combined neutral/earth conductor failed somewhere upstream, at which point all the pipework becomes live (To a greater or lesser extent) via the bonding network (Which keeps things reasonably safe as long as you are inside the equipotential zone), trouble is the kid was outside the zone and touched metalwork that exported the "Earth" from the zone.I surely do see earth rods used in TN-C-S installs, generally with a 16mm^2 cable attached, but I do a lot of radio work so that might be something specific to those sites (Which should probably really be TT anyway).Regards, Dan.

author: Monkeh
author_rank: Super Contributor
timestamp: March 05, 2018, 09:06:42 pm
content: Quote from: dmills on March 05, 2018, 09:01:58 pmIt's really not the norm, though, or correct.Think about this: If I install an earth rod in my house, the only one installed on my entire street (of 30 houses), and we completely lose the supplier neutral.. what happens to my 16mm² straight concentric supply cable when it's handling return current for 30 properties? Considering things here are fused at 300A per phase or something along those lines..Do you really expect a DNO to trust that every house will have a properly installed earth rod to supplement their installation which is entirely out of their control, they cannot inspect, and they cannot test?

author: gildasd
author_rank: Frequent Contributor
timestamp: March 05, 2018, 09:43:05 pm
content: Trying to twist my head around this incident and Belgian rules, I really really really want to avoid the possibility of this happening.As far as I know, in Belgium, it is illegal to use piping as earth conductor.Metal Piping can be earthed, but to the earth, not as the earth.All grounds must be connected to a main ground then to a stake whose length, position and depth below the surface are all regulated (I have two; one fore, one aft).All my water piping is PEX btw.

author: Marvo
author_rank: Contributor
timestamp: March 05, 2018, 10:41:14 pm
content: Best way to avoid it happening is to have an low impedance earth rod at every premises when the supply is PME'd TN-C-S and bond all services. The Ra of the local earth rod needs to be sufficiently low to ensure <50v touch voltage under full supply current.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 05, 2018, 10:53:27 pm
content: They did the whole thing ass backwards. Assuming all copper plumbing in the house was connected to the ground, you only do this if the pipes are already grounded through a buried metal pipe. Pipes can sometimes become isolated by water meters and such, but you are supposed to jumper across them. So either they illegally hooked up the ground to unearthed piping, or there was a modification to the plumbing that isolated it and the idiots didn't check it.

author: sibeen
author_rank: Frequent Contributor
timestamp: March 05, 2018, 11:19:40 pm
content: Quote from: Monkeh on March 05, 2018, 09:06:42 pmI don't know the British standards, but I do know the Aus/NZ relevant standard for this (AS/NZ3000) and I would actually be a bit surprised if the Brit standard varied considerably from the AS/NZ.In AS3000 section 5.3.2.2 states in part"Sprinkler pipes or pipes conveying gas, water, flammable liquid or other conductive non-electrical service enclosures shall not be used as anearthing medium."Next up we have5.3.6.1 General"The connection of the electrical installation earthing system to the general mass of earth shall be achieved by means of an earth electrode."I also just wandered out to the front of my property and there, located directly under my switchboard, is an earth stake which I decided to take a photo ofIn general every house in Australia will have an earth stake which will be connected to an earth bar within the incoming switchboard and the neutral and earth will be bonded within that board.

author: Bud
author_rank: Super Contributor
timestamp: March 05, 2018, 11:33:56 pm
content: Why it is always girls in these electric shock stories? I think there were 3 lastly and each time it was a girl.

author: digsys
author_rank: Unknown
timestamp: March 05, 2018, 11:51:13 pm
content: DON'T forget to water your stake during long dry spells !! I have a plant drip feed on mine. During our last very long dry spell, app 8yrs,E potential was climbing to 100V+ (depending on loads). Added a 2nd much deeper spike and lots of water. All good since.I knew something was wrong when isolation / test equipment / earth leakage designs were playing up.

author: Brumby
author_rank: Unknown
timestamp: March 05, 2018, 11:56:03 pm
content: Quote from: sibeen on March 05, 2018, 11:19:40 pmThat is my understanding of the current rules - but it was not always so.In years gone by, it was not uncommon for the water piping to be used as the household earth. When the new rules came in, there was no mandate for all properties to change - but I believe if you were to have any electrical work done, then you needed the separate earth spike put in.In this particular instance, I am also curious as to the current path - especially if the tap is out in an open yard with a buried pipe feeding it.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 06, 2018, 12:05:30 am
content: QuoteIt wasn't in the yard, it was probably on the side of the building and fed through the basement.

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2018, 12:09:17 am
content: Quote from: sibeen on March 05, 2018, 11:19:40 pmNever said you should use a water pipe as an earth.QuoteCongratulations, things differ in AU. A TN-C-S system does not need a local electrode and the system does not need electrodes connected to it via massively inadequate conductors.

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 12:09:59 am
content: Quote from: Cyberdragon on March 06, 2018, 12:05:30 amWe don't do basements. It was a copper water pipe and we bury them in the dirt.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 06, 2018, 12:16:16 am
content: Quote from: BradC on March 06, 2018, 12:09:59 amIf you mean you only have taps that come up from the ground on posts, then something extremely fishy was going on. They must have put a plastic conduit around the pipe for some reason. Is this normal?EDIT:https://www.doityourself.com/stry/how-to-insulate-underground-water-pipesWhy the hell were they using metal pipes outside anyway?

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 12:24:06 am
content: Quote from: Cyberdragon on March 06, 2018, 12:16:16 amBecause that's how we do it. Absolutely nothing wrong with burying copper in the ground. We've only recently started the trend of using plastic for water. Until recently (and still if you want to build a house that is not disposable) we used materials that had a known longevity. Every house I've ever lived in (only 6 admittedly) has had full copper plumbing, and all the outdoor stuff was buried.

author: sibeen
author_rank: Frequent Contributor
timestamp: March 06, 2018, 12:26:44 am
content: Quote from: Brumby on March 05, 2018, 11:56:03 pmThat's very true, Brumby. In Australia an underground water pipe was allowed to be used up until the 1976 version of AS3000 was promulgated, and there was no retrospective action enforced so that houses built before this time may have this style of earthing in place. If any upgrade work is carried out on the electrical installation in a house of this vintage the installing electricians is also supposed to upgrade the earthing to meet current standards. Sparkies normally hate working on these types of jobs as telling a client that upgrading a fuse to a circuit breaker also requires 'extra work' doesn't go down well.The main reason for the post was someone had claimed that an earth stake is not the normal method of installation. Whilst there are going to be variances across countries, in Australia it is a mandated method of installation and has been for over 40 years.

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2018, 12:36:49 am
content: Quote from: sibeen on March 06, 2018, 12:26:44 amI was directly responding to someone claiming it was normal for TN-C-S installations in the UK.Context is for kings.

author: raptor1956
author_rank: Frequent Contributor
timestamp: March 06, 2018, 02:07:49 am
content: When I was a kid, about 7-8 years old or there abouts, I had washed my hands in a public restroom then went to dry my hands on what was then new -- the heated electric blower. All was fine during the first cycle but when I went to start the second cycle, being a kid, I decided to hit the one next to it as well and I hit the metal power button of both driers at the same time. I got the shock of a lifetime and I suspect the voltage was 220VAC instead of the normal 120VAC common in the USA -- higher powered devices like clothes driers etc are generally wired to 220 volts versus 120.Well, yes, I did survive, but it could have been real bad if I'd been unable to remove my hands from the button and in this case it was fortunate that it was a button that's pushed versus a knob that needs to be grasped -- that would have made letting go much harder -- or impossible.I don't know if it was outright incompetence of the electrician that installed them or if the documentation from the manufacturer was at fault -- I'd guess both. Any decent electrician should have known about the potential.Brian

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 06, 2018, 02:17:31 am
content: Quote from: Bud on March 05, 2018, 11:33:56 pmMy guess is that they're more likely to use lotion than guys do which would make them more conductive.And one of the stories I wouldn't consider an electrical shock, although she definitely was taken by surprise!

author: John B
author_rank: Frequent Contributor
timestamp: March 06, 2018, 02:29:11 am
content: Quote from: sibeen on March 06, 2018, 12:26:44 amI think that was the case in my current house: a pre 1976 house that had an earth stake installed when the whole electrical box was replaced a year ago. I'm all too happy to have one put in. In fact, I'm surprised it's only one. I would have thought with block size and varying earth moisture you'd probably want a few around the house.Also this story prompted me to check the copper water and gas pipes. All are shorted* to mains earth ground.*a couple of ohms depending on the location in the house. A few earth straps wouldn't go astray.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 06, 2018, 02:48:03 am
content: Quote from: Monkeh on March 05, 2018, 07:26:45 pmand what moron connected earth return wiring to water piping?

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 03:01:02 am
content: Quote from: Mechatrommer on March 06, 2018, 02:48:03 amWhy *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.

author: digsys
author_rank: Unknown
timestamp: March 06, 2018, 03:51:52 am
content: Quote from: BradCYou'd think so BUT in reality -During Melbourne's last, very long hot dry period (8+ years), there were dozens of reported cases of plumbers getting quite serious electric shocksworking on buried plumbing. Some were serious enough to be admitted to hospital, and I believe there were even 1-2 deaths.The ground had dried out so much that there was literally NO earth connection, and any meter faults turned the plumbing LIVE.I noticed the issue, but luckily, instinct told me to bring in a friend, who happened to be a chief electrical inspector and working on the problemat the time. It's why I posted above .. "WATER YOUR STAKE"

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 06, 2018, 03:58:57 am
content: Quote from: digsys on March 06, 2018, 03:51:52 amIf that happens your grounding rods won't work either, so you're just plain screwed.

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 04:17:02 am
content: Quote from: digsys on March 06, 2018, 03:51:52 amBonding the pipework "gives more earth surface area than the earth stake". Dry soil in no way makes that statement less true.Your specific instance requires a localised environmental condition *and* simultaneously a wiring fault to raise the potential of the pipework. Not bonding the pipework (which in the majority of cases would contravene AS3000-2007 5.6.2.2) is highly unlikely to have prevented that condition. If in that particular instance equipotential bonding was not required (ie no exposed conductive pipework, non-conductive pipework to all exposed plumbing) then, yeah you might be ok. But a wiring fault is still a wiring fault.That, unfortunately is what happened in the instance being discussed in this thread, although being a State housing building and potentially being related to relatively recent works undertaken might conspire to see the real issues being papered over.

author: sibeen
author_rank: Frequent Contributor
timestamp: March 06, 2018, 04:38:15 am
content: Quote from: digsys on March 06, 2018, 03:51:52 amAn example of safety precautions to counter this is a plumber working on a gas meter. If a pipe has to be disconnected from the meter then a large earthing strap will be connected between the pipe and the meter before any spanner is applied. It avoids any chance of sparking and minimises the possibility of an electrical shock.

author: Brumby
author_rank: Unknown
timestamp: March 06, 2018, 05:07:54 am
content: Five or six years ago I had a leak near the water meter and called in the water authority to deal with it, as the leak was on their side of the meter (luckily).When the workers came out to do the repair, the first thing they did after digging down was the clamp a cable around the spot they were going to break the pipe. Once broken, they then measured the voltage - and if it was above a certain threshold, they could not continue. Fortunately this was OK and the fix completed rather quickly.It was also the first time I had seen liquid nitrogen used first hand. That was cool.

author: mtdoc
author_rank: Super Contributor
timestamp: March 06, 2018, 05:13:13 am
content: Quote from: Brumby on March 06, 2018, 05:07:54 amWhat did they use the liquid N2 for? Freeze the pipe upstream before breaking it?

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 05:26:30 am
content: Quote from: Brumby on March 06, 2018, 05:07:54 amMost plumbing stuff uses 1,1,1,2-Tetrafluoroethane. They spray the pipe to create an ice plug. It's interesting that they dump Kilos of that stuff into the air to freeze a pipe, but if I let any out of the A/C in my car I'm an environmental terrorist.Liquid N2 would be much quicker. I've not seen them use that over here.

author: Brumby
author_rank: Unknown
timestamp: March 06, 2018, 05:42:56 am
content: Actually, I didn't ask - so I might have that wrong.The technique used was to take a styrofoam cup and fit it around the pipe - yes, upstream to the cut - and then pour in a clear liquid that boiled feverishly, just as I have seen LN2. Zero flow check at a nearby tap and then work commenced.

author: Muttley Snickers
author_rank: Unknown
timestamp: March 06, 2018, 06:00:58 am
content: A mate of mine is both a plumber and gas fitter and he uses a carbon dioxide based freezing system, it's done by placing a sleeve similar to a velcro blood pressure wrap around the pipe to be plugged then turning on the bottle of CO2, I'm pretty sure the brand was Edro in Queensland.

author: digsys
author_rank: Unknown
timestamp: March 06, 2018, 08:23:45 am
content: Quote from: Cyberdragonerrrrr that's why I mentioned twice now .. Water your stake ! (and me fitting a drip system). It's impractical to water all your water plumbing,,and you generally don't expect trouble there, but an E-Stake only has 1 use. (also why I went with a 2nd much deeper one),

author: Muttley Snickers
author_rank: Unknown
timestamp: March 06, 2018, 09:20:05 am
content: Although this particular event appears to be a relatively rare occurrence I'm a bit surprised they couldn't or didn't incorporate monitoring of a dropped neutral or bad earth condition into the smart meters which could then have disconnected the active or at the very least generated an alert either locally or remotely until reset.

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 11:55:13 am
content: Quote from: Muttley Snickers on March 06, 2018, 09:20:05 amWe don't have smart meters. We have expensive digital meters that do some neat maths, and if you mortgage a kidney you can get some off peak action but they don't talk back and can't be remotely controlled. We might be a bit backward out West, but then we generally have an affordable and reliable grid too (although AEMO have moved in here recently, so we expect prices to rise and reliability to drop as they start screwing with the market).Quote from: digsys on March 06, 2018, 08:23:45 amLucky for me my stake sits less than 1000mm from the top of the water table.Latest news on the young lady is some form of unquantified brain damage, and she's still unconscious.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?

author: digsys
author_rank: Unknown
timestamp: March 06, 2018, 12:21:48 pm
content: Quote from: BradCYou and I might, we are used to HV zaps and everything related to them, but she was a young girl. She may have been disoriented, traumatized orphysically disabled (muscle / injury), and had no idea of what had happened. Hope she makes it ok

author: amyk
author_rank: Super Contributor
timestamp: March 06, 2018, 12:26:22 pm
content: QuoteI 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.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 06, 2018, 12:28:06 pm
content: Quote from: BradC on March 06, 2018, 11:55:13 amYou 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).

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 12:36:16 pm
content: Quote from: digsys on March 06, 2018, 12:21:48 pmHer 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.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 06, 2018, 01:11:26 pm
content: Quote from: BradC on March 06, 2018, 03:01:02 amany 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.

author: BradC
author_rank: Super Contributor
timestamp: March 06, 2018, 02:13:51 pm
content: Quote from: Mechatrommer on March 06, 2018, 01:11:26 pmRight. 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.

author: sibeen
author_rank: Frequent Contributor
timestamp: March 06, 2018, 02:19:17 pm
content: Quote from: grumpydoc on March 06, 2018, 12:28:06 pmNot in Australia. The main switch into an installation only disconnects the active conductor(s).

author: Brumby
author_rank: Unknown
timestamp: March 06, 2018, 02:26:13 pm
content: Quote from: sibeen on March 06, 2018, 02:19:17 pm... 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....

author: dmills
author_rank: Super Contributor
timestamp: March 06, 2018, 02:38:20 pm
content: 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.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 06, 2018, 02:45:48 pm
content: Quote from: sibeen on March 06, 2018, 02:19:17 pmSlightly 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 circuitsDP in France with DP on individual circuits** For single phase, obviously

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2018, 04:21:15 pm
content: Quote from: dmills on March 06, 2018, 02:38:20 pmAs 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).

author: james_s
author_rank: Super Contributor
timestamp: March 06, 2018, 04:52:55 pm
content: 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.

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2018, 04:58:33 pm
content: Quote from: james_s on March 06, 2018, 04:52:55 pmUnfortunately 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.

author: james_s
author_rank: Super Contributor
timestamp: March 06, 2018, 05:04:19 pm
content: 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.

author: sokoloff
author_rank: Super Contributor
timestamp: March 06, 2018, 05:29:52 pm
content: Quote from: james_s on March 06, 2018, 05:04:19 pmWe 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...)

author: Macbeth
author_rank: Super Contributor
timestamp: March 06, 2018, 08:20:25 pm
content: 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?

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2018, 08:33:23 pm
content: Quote from: Macbeth on March 06, 2018, 08:20:25 pmWho? The only people shown are an 11 year old girl and her mother..

author: Macbeth
author_rank: Super Contributor
timestamp: March 06, 2018, 10:08:17 pm
content: Quote from: Monkeh on March 06, 2018, 08:33:23 pmLad in this video here:http://www.abc.net.au/news/2018-03-05/denishar-woods-remains-in-critical-condition-after-electric-sho/9510242Whatever or whoever is the cause, I do hope the poor girl recovers.

author: Monkeh
author_rank: Super Contributor
timestamp: March 06, 2018, 10:09:05 pm
content: Oh. Well, okay, he's a bit suspect.

author: Electro Detective
author_rank: Super Contributor
timestamp: March 07, 2018, 01:05:44 am
content: 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 wrongIt may even be something from neighbouring properties too, something on the ground/mud/pool etcI hope the girl pulls through okand learns the electrical trade to be a proper sparkieto 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

author: vk6zgo
author_rank: Super Contributor
timestamp: March 07, 2018, 07:25:11 am
content: Quote from: james_s link=topic=105339.msg1445397#msg1445397t date=1520355859Back 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!

author: Macbeth
author_rank: Super Contributor
timestamp: March 07, 2018, 03:15:10 pm
content: Quote from: vk6zgo on March 07, 2018, 07:25:11 amThere 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

author: james_s
author_rank: Super Contributor
timestamp: March 07, 2018, 05:38:37 pm
content: 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.

author: BillB
author_rank: Unknown
timestamp: March 07, 2018, 05:51:28 pm
content: Tragic electrocution story all the way to hot dog cookers within 3 pages! God bless internet forums!

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: March 07, 2018, 08:09:22 pm
content: 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..

author: james_s
author_rank: Super Contributor
timestamp: March 07, 2018, 09:52:54 pm
content: 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?

author: Gyro
author_rank: Super Contributor
timestamp: March 07, 2018, 10:46:58 pm
content: Quote from: BillB on March 07, 2018, 05:51:28 pmI've created an alternative thread in the interests of good taste...https://www.eevblog.com/forum/chat/the-direct-mains-powered-food-based-organic-lighting-and-cooking-thread/

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 08, 2018, 01:00:34 am
content: Quote from: grumpydoc on March 06, 2018, 02:45:48 pmTrue for France.The french regulation (NF C15-100) justifies that depending on neutral line impedance and loading, neutral can be at dangerous voltages wrt earth.Nothing to do with DP disconnects, just to say you can't really take anything for granted: A few years back a kid died in France, after doing sports he rested his wet sweater's back against a public lamp post.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 08, 2018, 10:42:29 am
content: Quote from: shakalnokturn on March 08, 2018, 01:00:34 amGiven that earthing in France is typically TT that makes sense as it would make the installation safe in the case of an upstream neutral fault (assuming the local earth connection is sound).

author: gildasd
author_rank: Frequent Contributor
timestamp: March 08, 2018, 01:19:39 pm
content: This is my instalation:1) cabling inlet2) main breaker3) counter4) three parallel breakers (I have 3 phase)5) to cabinet where 380 is converted to 240.6) differential on each line.So it seems to be similar to the French rules.

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2018, 04:34:03 pm
content: There's a transformer stepping 380 down to 240 inside your house?

author: Monkeh
author_rank: Super Contributor
timestamp: March 08, 2018, 04:36:14 pm
content: Quote from: james_s on March 08, 2018, 04:34:03 pmNo, they have 380V phase-to-phase which is approximately 220V phase-to-earth.

author: james_s
author_rank: Super Contributor
timestamp: March 08, 2018, 04:43:56 pm
content: Ah that makes sense, it was the "converted" terminology that caught me.

author: gildasd
author_rank: Frequent Contributor
timestamp: March 08, 2018, 05:28:42 pm
content: Sorry got muddled in the three concerned languages.Four if “electrician” is considered as one.

author: edgelog
author_rank: Regular Contributor
timestamp: March 08, 2018, 08:46:39 pm
content: Quote from: Monkeh on March 06, 2018, 04:58:33 pmWhat seems more likely is that she had ventricular fibrillation with circulatory arrest for a while, resulting in hypoxic brain damage before she got her circulation back (resuscitation, defibrillation, etc).

author: james_s
author_rank: Super Contributor
timestamp: March 09, 2018, 02:22:44 am
content: Quote from: gildasd on March 08, 2018, 05:28:42 pmYeah no worries, as someone who can speak only one language I can hardly complain if something gets muddled in translation when someone else is courteous enough to converse with me in my native language rather than theirs.I've long found the regional differences in electrical infrastructure interesting. Several years ago when I visited England I had the opportunity to (with direct supervision) replace the breaker panel/"consumer unit" in an outbuilding and add a couple of circuits. Strange activity to do on vacation but I found it fascinating.

author: sibeen
author_rank: Frequent Contributor
timestamp: March 09, 2018, 05:25:54 am
content: Unfortunately the young girl's prognosis is not good.http://www.abc.net.au/news/2018-03-09/denishar-woods-undergoes-mri-after-electric-shock-brain-damage/9529346

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 09, 2018, 06:36:38 am
content: Maybe 240V overseas should have been done the way it is done in the US as in 120V from each side to neutral, 180 degrees out of phase? (Of course, then those who argue for 120V would then propose doing 120V as 60V each side to neutral...)

author: james_s
author_rank: Super Contributor
timestamp: March 09, 2018, 06:51:40 am
content: I'm not sure how much difference it would have made. People are killed by 120V occasionally too.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 09, 2018, 07:16:08 am
content: Considering she was just on the edge of surviving, half the voltage in the same situation would probably have been survivable. Apparently one significant damage mechanism in that case was thermal, so half the voltage would actually result in 1/4 the heat.And I'm sure the AC vs DC debate is going to reignite, but there's little data on HVDC shocks. It is generally agreed that DC is less likely to stop the heart, but it would have electrolytic effects that AC doesn't.

author: mac.6
author_rank: Regular Contributor
timestamp: March 09, 2018, 10:13:21 am
content: Depend on what you call HVDC. There is a good documentation on real HVDC accident due to migrants or dumbs young adults climbing on trains in EU, not a nice thing to see when HVDC mean 25kV, even 3kV supplies are instakill.

author: dmills
author_rank: Super Contributor
timestamp: March 09, 2018, 10:15:50 am
content: The other elephant in the room is relative fire risk, half the voltage means that connections for a given power become a lot more critical as I^2R losses rise, I would not be surprised if the increase in electrical fires outweighed the reduction in electrocution from running lower voltage.The US is a poor comparison source for this, given the wide use of timber frame, wirenuts (Yes, I know if done right they are reliable, but there are so many ways to get it wrong) and 'backstab' connectors.Regards, Dan.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 09, 2018, 03:24:16 pm
content: 240V is going to be the same current per VA whether implemented as 240V to neutral or 120V each side to neutral. The difference is that with 120V each side to neutral, the probability of getting a 240V shock across the heart is much reduced. It would give the benefit of 240V and not be that much more dangerous than 120V.Quote from: mac.6 on March 09, 2018, 10:13:21 amAt that point, AC vs. DC is going to make virtually no difference from that standpoint.In data centers, HVDC refers to 380V or so. Low voltage DC is standardized at 48V.

author: james_s
author_rank: Super Contributor
timestamp: March 09, 2018, 04:43:31 pm
content: The backstab terminals are a real issue. I've never seen a fire caused by a wire nut, but I've seen multiple instances of those backstab terminals burning up, one in my own house where I was fortunate that the wire burned off and opened the circuit. For what it's worth, I've seen pictures of the European style screw terminal blocks that have melted down due to screws loosening up over time. Actually I suspect it may be due to the solid copper wire compressing but I'm not certain.With any number of situations like this it's easy to suggest some change in the way things are done that would have prevented this specific incident, but there can be unintended consequences. Virtually everything is a compromise, if you make a change to prevent one sort of accident you may well cause some other accident.

author: dmills
author_rank: Super Contributor
timestamp: March 09, 2018, 08:16:36 pm
content: Indeed, maybe someone fucked up, but that is far from certain, sometimes it is just bad luck.Regards, Dan.

author: Electro Detective
author_rank: Super Contributor
timestamp: March 10, 2018, 10:09:54 pm
content: Quote from: dmills on March 09, 2018, 08:16:36 pmBad luck for the girl she walked into some assholes dodgy 'work', negligence, ignorance, mixed with apathy.I would still investigate the neighbours electrics too, you never know how much cheapskate DIY dumbassery can be lurking to cause something like this in the burbs...

author: dmills
author_rank: Super Contributor
timestamp: March 10, 2018, 10:32:57 pm
content: Possibly, but that is my point, it might well have been dodgy work, or a 30 year old underground cable damaged by a modern heavy truck interacting with subsidence, or with ground movement caused by drought or storm, (Or say an old aluminium overhead feeder with a failed splice, could have been up there for 20 years) no way to predict that!When you decide that TN-C-S is the way to roll, you accept this risk in return for reducing the risks from some more common faults.Energy systems safety is at root a numbers game, there is no such thing as absolute safety in any actually useful system, all you can do is trade things off to minimise overall risk, which is no comfort at all when it is your kid that got sideways with it of course.I would not be assigning blame for this one until we know **EXACTLY** what failed and how, anything else is just speculation.Regards, Dan.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: March 11, 2018, 04:17:03 am
content: Quote from: james_s on March 07, 2018, 09:52:54 pmIt is - as usual - kind of a question of who is responsible. There is the user and the devices used, the electricians installation and the utility, all over a long time. The responsibility for an installation probably ends at the outlet (a GFCI being an exception, but not as preventative safety as it only switches off while the problem actually occurs) and the installation can only be as good as what the utility is guaranteeing to deliver. This guarantee being useless and not preventing all life threatening situations for certain fault conditions. And thats where the rubber meets the road.It is simple for users and devices: in certain parts of the world you can plug the cable into the outlet both ways, so you never know if left or right is Live or Neutral. So you need to switch both or remove the plug to really be "safe" and switch off the live wire. The outlet itself has no regulation to be wired in a certain way except for protective earth. Switches in an installation are however usually single pole and meant to switch the live wire to not expose voltage to e.g. open light bulb sockets.For the installation itself, live and neutral can be seen hot all the time, it would not make a difference for the load at alternating current, but if neutral is disconnected, the open end neutral becomes hot (behind the connected loads), as probably was in this case. I would say for the same reason neutral needs to be an insulated wire, although connected to protective earth.I assume double pole breakers represent some kind of shift of responsibility to improve safety in more cases than before. From simple: neutral fault -> outlets still hot to problems in the utilitys grid.For three phase power there could be a neutral point shift (hope i translated that correctly) if neutral is disconnected/not able to balance out and loads are out of balance, so that the neutral wire gets a voltage above safety limits.Add residential power generation or battery backup (electric vehicle as a storage) to the picture and it is getting more complicated what the utility can guarantee and how, as they are not a single supplier anymore or might not be able to control stability. Since feeds into the grid are not the typical synchronous machine anymore that would slow down or accelerate based on load it might as well generate higher voltages on one phase but stay within the frequency range which results in a neutral point shift. (See e.g.here) Such scenarios are also adding new fault conditions to the range, so it might as well be that such changes are there to accomodate that.But i got another question regarding earth rods during droughts: are lightning rods a thing every house has/needs in Australia?

author: Brumby
author_rank: Unknown
timestamp: March 11, 2018, 08:31:24 am
content: Lightning rods are practically unheard of in residential properties - in Sydney at least.You may come across the odd one where someone has put one up - but you would have to go hunting to find one.We see them atop tall power poles, commercial buildings and other structures. We also see them in electrical switchyards.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 12, 2018, 01:41:34 am
content: Quote from: BradC on March 06, 2018, 02:13:51 pmthe most contradicting statements i figured out of the year... what good an earth stake if its not connected to anything (earth system)?. the fact that the pipework is bonded or a part of (or whatever the term is) the earth stake, and the fact that someone got a really bad shock means that... pipework do got connected to electrical system.Quote from: BradC on March 06, 2018, 02:13:51 pmmeaning now its illegal. i hope so for australians sake, and someone must implement this correctly.Quote from: Brumby on March 11, 2018, 08:31:24 amhigh rise building should require this, here is common for larger (taller) buildings greater than 5 storeys esp government buildings. but... some superheros like to strip the copper bar apart, the bar usually like an inch by 3-5mm thick, very good price in metal scrap yard. this superheros sometime went further into substation or a pole and got some very good toast

author: dmills
author_rank: Super Contributor
timestamp: March 12, 2018, 11:03:05 am
content: Quote from: Mechatrommer on March 12, 2018, 01:41:34 amUsually when the regs change they apply to NEW work but are not applied retrospectively (That would cause huge costs).Back in the 70's I am betting everything was TT or TN-S (Like it was in the UK) and in those situations using buried copper water pipes to extend the earth system probably kind of makes sense on aggregate.Regards, Dan.

author: Beamin
author_rank: Super Contributor
timestamp: March 12, 2018, 12:12:30 pm
content: So how does this work? The neutral line was disconnected from the ground at the breaker? Or are you saying the actual dirt in the earth was live and touching the water pipe which was grounded made for a connection?I lived at a place where 60 volts was between neutral and ground. No point in calling maintenance they refused to hire an electrician. This was a shit hole and not cheap but the cheapest in town so the property managers were horrible. They had the maintenance people fix EVERYTHING regardless if it was legal or not or if they were qualified. The maintenance people had a mixture of: not caring about anything especially their job or the tenants, laziness, no education even high school let alone how to fix things, low IQ and low pay. No lie, one guy talked like forest gump and would make the same mistake over and over. 13 times he tried to fix the same door lock and failed. It would have been totally pointless to call about the electricity because every time they would come to the apartment ( 4 hours late if you were lucky) come in without knocking, they would usually make the problem worse break something else by accident and ALWAYS leave a mess and steal female underwear. One guy asked me to borrow a screw driver I said "how do you not have a screw driver?" "I don't carry around every tool with me all the time!". I wouldn't let him borrow my screw driver because he would find away to break it then lose it then got pissed at me. Nobody gives a sit about poor people until someone dies and they sue.

author: dmills
author_rank: Super Contributor
timestamp: March 12, 2018, 12:54:53 pm
content: Quote from: Beamin on March 12, 2018, 12:12:30 pmAt the transformer (and in some other locations, usually) the star point is connected to earth by a serious grounding arrangement, it is also connected to the combined Earth/Neutral conductor.Each home fed from that transformer then has (Probably) one phase of the supply plus the combined Earth/Neutral brought to the property.The Earth/Neutral is then split (Exactly how and who depends on the country) to produce a neutral (intended to be current carrying) and an 'earth' that should not normally carry current. This earth connection may or may not also have a local ground stake but these are usually rather high impedance.Now it should be clear that in the event of a failure of the combined Earth/Neutral somewhere upstream the combined earth neutral at the property will move away from true earth as current finds a way to true earth to bypass the breakage, and this is a real danger (as the currents can be large and the impedances high, makes for lots of volts), if you have other metalwork in the property connected to true earth.The cure is to bond all the exposed metalwork together and to the suppliers earth, such that everything moves together in the event of a fault, which works just fine and makes the fault a lot less dangerous. The trouble comes when you export this 'equipotential zone' outside the building, like say by adding an outside tap.Now, given a failure in the combined earth/neutral you get the metalwork inside the house being pulled up to line voltage via the loads in the house and the neutral/earth bond), which is not all that dangerous inside the house because any other metal you are likely to touch in the house is ALSO connected to that same potential, but step outside and touch that tap and now you become the path to ground (and hence back to the transformer star point) for potentially not just your house loads, but every load downstream of the fault.The killer is the difference between local "Earth ground" which is effectively connected to the star point and the imported "Earth" from the faulty combined earth neutral.Yet for all this TN-C-S is less problematic then the practical alternatives.Regards, Dan.

author: G7PSK
author_rank: Super Contributor
timestamp: March 12, 2018, 04:13:45 pm
content: Was the fault an earth fault or a power feed fault. A few years ago a horse was killed on a racecourse here in the UK due to an under ground power cable developing a fault, the current flowing through the ground was sufficient to create a lethal potential for any horse crossing the current path. The horse obviously had a lower resistance than the ground which was quite moist at the time. A very similar thing happened to a friend of my sisters horse, she rode it past a street light that had a fault again the current was great enough to kill the horse.http://www.dailymail.co.uk/news/article-1356725/Newbury-horse-deaths-Investigators-remove-cable-racecourse.htmlSeems it a similar thing happened in Australia.https://www.perthnow.com.au/news/wa/police-horse-killed-two-officers-suffer-electric-shocks-ng-c1a708ef6ad3c573bedebc79fc9abb75

author: dmills
author_rank: Super Contributor
timestamp: March 12, 2018, 04:49:02 pm
content: And that is why stable blocks are 'special locations' at least in the UK regs, most large 4 legged critters are sensitive to ground potential gradients, (as are the two legged sort) but we wear (insulating as opposed to metal) shoes and usually don't span 2M at a stride.This was fundamentally a difference in notions of 'ground' with respect to the transformer star point (The mass of earth was connected to it, the neutral/"Earth" conductor was not), and one of them was being held far enough away from the other by a fault in a cable that getting between them was tragic.Not at all an obvious sort of fault until you draw it out.Regards. Dan.

author: G7PSK
author_rank: Super Contributor
timestamp: March 12, 2018, 05:07:33 pm
content: It's nothing to do with metal shoes as they are in contact with the horn only which is the same as finger/toe nails. It is the soft tissue of the horses hoof that comes into contact with the ground that is conductive, the Frog and the sole. What I was thinking is that in Australia many people go barefoot in the garden same goes for South Africa and Zimbabwe where I have relatives, to me it's crazy but they do and think nothing of it.

author: james_s
author_rank: Super Contributor
timestamp: March 12, 2018, 05:17:52 pm
content: I don't go barefoot outside because I hate getting splinters in my feet. Electrocutions can and do occasionally occur, but it is exceptionally rare. I suspect one is much more likely to be killed by a falling tree branch than an electrical fault in the ground. Around here there are usually one or two deaths each time a substantial storm rolls though, people killed by falling branches or an entire tree falls across a road and flattens an unlucky car going by.

author: dmills
author_rank: Super Contributor
timestamp: March 12, 2018, 05:26:24 pm
content: Learnt something new (about horse anatomy), today was a good day!Regards, Dan.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 13, 2018, 02:17:41 am
content: Quote from: james_s on March 12, 2018, 05:17:52 pmFrom the pictures, it looks like she was wearing shoes but they offered no protection because they were wet.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 14, 2018, 06:45:17 am
content: maybe any old residents should ground (new installation) their every water tap, locally or centrally.. thats the cheapest solution i can see for now..

author: Electro Detective
author_rank: Super Contributor
timestamp: March 14, 2018, 09:29:56 am
content: Quote from: Beamin on March 12, 2018, 12:12:30 pmThis is classic early to mid 1900s BS, it still goes on?Are the lousy cheapass 'landlords' called 'property managers' nowadays?I would have thought that generation of creeps would all be in hell by now, counting the pennies they took with them to keep warm and pass the time...What country is it btw?

author: Beamin
author_rank: Super Contributor
timestamp: March 14, 2018, 11:08:57 am
content: Quote from: Electro Detective on March 14, 2018, 09:29:56 amUSA USA USASo I'm kind of slow: on the pole after the star connection of the three phase trans: the neutral is hooked up to earth which is a physical ground rod. The neutral on the pole disconnected from this? Where did live connect to the ground? Why was she shocked at the house when the pole is normal on the street 50+ feet away?Speaking of USA the pole has three phase 440 on the wires: these go into a transformer and are turned into 2 phase 240 to the house where it split again into two legs on breaker box? How do they do that without making 2 phases out of sync with the 3 or does one house get one pair of the 3 phase and the other house gets another leg sharing one so it balances? Like you balance the two legs in your house?

author: Electro Detective
author_rank: Super Contributor
timestamp: March 14, 2018, 12:35:53 pm
content: "Household power supplies in North America use what's called a split-phase system.The transformer on the pole outside the house takes grid power and steps it down to 240 VAC from end to end on the secondary winding.The secondary winding has a center-tap in it which splits this 240 VAC into two 120 VAC voltages from either end to the center tap.This center tap is defined as Neutral and it is tied to Ground in the circuit breaker box inside the home.The two 120 VAC voltages are 180 degrees out of phase with each other and it is this very antiphase relationship that creates the voltage difference of 240 vac between L1 and L2. "Quote 'borrowed' from SamuraiRepairmanon Youtube who explains and demonstrates it beyond doubt to newbs and doubters"Using an Oscilloscope to Understand 120 VAC Split phase Household Power Supplies"youtube.com/watch?v=vOh2OSJ44eE

author: james_s
author_rank: Super Contributor
timestamp: March 14, 2018, 04:31:09 pm
content: On the pole it's typically 3 phase, 7,200V from phase to neutral. The distribution transformer on the pole connects to one of those phases and steps 7,200V down to center tapped 240V. In some cases a neighborhood may only have single phase in which case it's fed by one of the three phases run down the main line which is generally adjacent to a major arterial road. The neighborhoods adjacent to that line will be staggered amongst the 3 phases in order to balance the load.

author: Beamin
author_rank: Super Contributor
timestamp: March 17, 2018, 09:13:12 pm
content: Quote from: james_s on March 14, 2018, 04:31:09 pmSo this is where I don't understand. If you only take one of the three phases and step down wouldn't you have 1 phase? How does a transformer do this with out spinning parts or sophisticated converters? My friends house had 3 phase to run a bridge port; he took a 240VAC 2 phase motors and spun a 480 3 phase motor using it as a generator. He did this because there wasn't an easy way to get those types of amps out of a power supply that wasn't expensive and unreliable and lossy.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 17, 2018, 09:48:31 pm
content: It "splits" it. Each outer end of the secondary changes from positive to negative (240V) when the current alternates. If you tie into the center of the coil, you get the average, which is zero, with the positive and negative 120V on either side.A 2-phase motor?!Those are incredibly rare (is it an antique?). Unless you mean it's one phase 240V. In that case, you don't need to keep it running, just start it spinning then pass the one phase to the three phase motor and it will keep spinning by itself.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 17, 2018, 11:58:44 pm
content: Things do not seem to be going well for the poor girl, though some of the reports are slightly conflicting.https://www.perthnow.com.au/news/wa/beldon-electric-shock-housing-minister-peter-tinley-visits-denishar-woods-in-princess-margaret-hospital-ng-b88777287z

author: chris_leyson
author_rank: Super Contributor
timestamp: March 18, 2018, 12:21:53 am
content: Thanks for the update grumpydoc it's not the news we wanted to hear but I hope some good comes from this unfortunate accident.