Electrical deaths

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Originally Posted by rrich

In another place and another time. . . . .

I took the flashlight (Torch) removed the batteries and bulb. Then with a bit of wire and medical tape I "made" a flashlight. Stupid? Yes. Even my father thought that it was stupid and a waste of medical tape. And I caught h***.

But I learned more about electricity doing that than I was ever taught in science classes in years 5 & 6.

With that small bit of knowledge and a question to a friend who was a sparky, I understood hot, neutral and ground of an AC circuit. Some years later I watched a sparky install a circuit for a clothes dryer. (220 volts using phase A and phase B.) From that I understood our complex electrical system for higher wattage appliances.

The point is, give your kids a torch, a few extra batteries, a bulb and a bit of wire. Challenge them to "make" a torch. What they will learn is priceless and will stay with them all their lives.

What usually kills people is not necessarily the hot wire but ground. We are all aware of the hot wire but almost never aware that we are in contact with ground. Yes, it sounds stupid but the more that you think about it, the more sense it makes.

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Playing with batteries and light globes is extremely useful but there's a bit more to learn about mains AC so that students can be safe. The ground is actually irrelevant - it's the current delivery capability of the supply and the potential difference across the contact points that electrocutes. Teaching these concepts is not all that easy.

Simple/common explanations that use the word "ground" appears to leads to a serious life threatening misconception about mains electricity. In regular surveys I did of university students in my first year physic classes, the majority of students (who had all passed senior high school physics) thought they were totally safe if their body did not touch the actual ground - e.g. they could use rubber boots and do what they liked with mains electricity,. When I asked them to explain why so many people are electrocuted in roof cavities they could not explain it. It also does not take into account that electrocution can happen between two phases of multiphase supply. The concept of electrical potential and potential difference is not all that intuitive which is why it is difficult for most people who usually think in terms of absolutes.

A couple of years ago a local electrical wholesaler closed his shop due to retirement. Behind his main counter was a sheet of ply with a lot of melted and burnt electrical fittings that some of the sparkies had brought in. These ranged from complete fuse boxes that were burnt to 8 double adapters that had melted and fused together off the one power point and a lot of other stuff as well. Most of them were as a result of "home" electricians. The old boy also told me a few stories about when he started in the trade. Head shaking stuff .

I also remember in my second year as an apprentice chippy in NZ, working on a row of shops and an amenity building at our local Uni campus. After installing most of the ali windows the boss got me and another apprentice to install the storm moulds etc. We needed a power drill ( pre-cordless obviously ) so we ran out a couple of cords from the site box and connected them together. Being safety conscious I also plugged the first power cord into one of our transformers then looped it over a few timber frames to keep it off the wet ground and away we went. An hour later the other apprentice had the drill and was pulling it and the attached cable around the corner of the building complaining that it was stuck on something. I went and had a look and was mortified that the cables had dislodged from the timber frame and were lying directly on the muddy ground. Where the two power cords had been tied together they were now in a puddle and under water which was now bubbling ! I yelled out for the other guy to drop the drill then went back and fixed the cables being on the ground. I still can't work out why it didn't blow the fuse ?

Stewie

It wouldn't have blown the fuse because fuses don't work that way. A fuse blows if there is either significant instantaneous overcurrent (maybe 10x normal) or if there is prolonged draw at a slight overcurrent (maybe 1.5 x normal for 30 minutes).

See also: http://www.youtube.com/watch?v=dcrY59nGxBg

A friend was electrocuted at work today. He is alive but badly shaken. :oo: I don't know how badly he was hurt yet.

This happened in a very large office environment where ALL the electrical work was done by professionals. I imagine that there are going to be health and safety inspectors all over the place tomorrow if they aren't already there today.

Doug

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Originally Posted by doug3030

A friend was electrocuted at work today. He is alive but badly shaken. :oo: I don't know how badly he was hurt yet.

This happened in a very large office environment where ALL the electrical work was done by professionals. I imagine that there are going to be health and safety inspectors all over the place tomorrow if they aren't already there today.

Doug

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That's not a good thing. Did he get himself checked out properly? Most people don't realise they need to seek proper medical advice after being zapped by mains. Burns can occur internally which can lead to all sorts of problems. I hope he is OK

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Originally Posted by doug3030

A friend was electrocuted at work today. He is alive but badly shaken. :oo: I don't know how badly he was hurt yet.

This happened in a very large office environment where ALL the electrical work was done by professionals. I imagine that there are going to be health and safety inspectors all over the place tomorrow if they aren't already there today.

Doug

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Definitely not good. Sincerely hope it was a minor shock.

In the early '70's my Dad & I were both booted at the same time by 240V. I was standing on a timber workbench holding up a disused TV antenna so we could store & secure it to the underside of the rafters in the shed. Dad touched me while he was standing barefoot on the concrete floor & both of us got thrown to the floor. After some searching with the mains off my uncle, who was an electrical inspector for the regional electricity board, found the culprit - a brass cable clamp. When the shed was wired the pin in the cable clamp had not been driven home fully into the hardwood rafter so the OCD electrician neatened up the clamp with a whack. That damaged the insulation & just happened to be the one the aluminium antenna element contacted.

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Originally Posted by BobL

That's not a good thing. Did he get himself checked out properly? Most people don't realise they need to seek proper medical advice after being zapped by mains. Burns can occur internally which can lead to all sorts of problems. I hope he is OK

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Would you believe the idiots at work told him to go home and have the rest of the day off.

I have not contacted him personally, he is not that close a friend but I have been advised he had the good sense to take himself to a doctor. He is actually a member of the Corporate Health and Safety Committee, ironically.

Doug

My electrocuted friend is doing fine.

Cheers

Doug

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Originally Posted by doug3030

My electrocuted friend is doing fine.

Cheers

Doug

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Good to hear.

Not a good story Doug but I hope your friend will continue to do well and that everything possible is done to find and rectify the cause of the incident. I also trust the installers will be traced and brought to account.

Some years back a lady I worked with had a son who was electrocuted at his school when he put a paper clip into a power socket. The school did not not inform the mother or seek any medical help. Luckily the kid was OK.


In another example of professionals getting it wrong we had electricians working at our school. Our very conscientious WPH&SO did a lockout and informed staff of what was going on. The arrogant sparkie failed to inform Andy of his completion of the work and somehow ripped the fuse box open, put everything in place and left.

All the woodwork machinery was running backwards!!

There was some action taken but I didn't get to find out what.

Hi,
Not wishing to be a grammar/spelling Nazi I still have to point out that the dictionary says "electrocution death electricity". If the victim survives they have had an electric shock and/or injury.
:)
Regards

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Originally Posted by A Duke

Hi,
Not wishing to be a grammar/spelling Nazi I still have to point out that the dictionary says "electrocution death electricity". If the victim survives they have had an electric shock and/or injury.
:)

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Somebody had to say it, I've been looking at the last few posts and thinking I didn't want to be the first. :)

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Originally Posted by BobL

Playing with batteries and light globes is extremely useful but there's a bit more to learn about mains AC so that students can be safe. The ground is actually irrelevant - it's the current delivery capability of the supply and the potential difference across the contact points that electrocutes. Teaching these concepts is not all that easy.

Simple/common explanations that use the word "ground" appears to leads to a serious life threatening misconception about mains electricity. In regular surveys I did of university students in my first year physic classes, the majority of students (who had all passed senior high school physics) thought they were totally safe if their body did not touch the actual ground - e.g. they could use rubber boots and do what they liked with mains electricity,. When I asked them to explain why so many people are electrocuted in roof cavities they could not explain it. It also does not take into account that electrocution can happen between two phases of multiphase supply. The concept of electrical potential and potential difference is not all that intuitive which is why it is difficult for most people who usually think in terms of absolutes.

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I used to work with a sparky who thought I was lying when I said you could hang onto an active (live) wire and not get electrocuted provided you had no electrical connection to ground and no connection to neutral. He did not beleive me, so I showed him!! So many electricans and engineers simply dont understand the basics physics.

When I did my apprenticeship (Instrument fitter, which is/was a dual trade), I was taught to work on live gear. Can't take down a whole factory because of one faulty bit of gear, so you had to fix it live. I beleive this is now illegal, but I cant confirm as I am a good 10+ years out of the trade.

When it comes to electrical work, I am fairly picky. The standard of electrical work done by a lot of electricians these days is absolutly appaling. Take a look at a lot of new building developments and the wiring is so poor I am surpised there has not been more fires/electrocutions.. I like to have pride in my work, so I do it well and I do it properly. I dont do electrical work anymore, but when I hire electricians to work on my house I expect the same standard of work that I used to do when I was on the tools. Unfortunatly that comes at a cost.

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Originally Posted by Pearo

I used to work with a sparky who thought I was lying when I said you could hang onto an active (live) wire and not get electrocuted provided you had no electrical connection to ground and no connection to neutral. . . . . . .

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Or connection to any other active phase.

It also depends on the V.
With high voltage all sorts of crazy stuff can happen and you may think you have no electrical connection but suddenly what is high resistance at 240V breaks down and can pass enough current to be deadly.

Most folks don't realise they can be killed by lightning striking the ground near them. The million+ V lightning strike sets up brief areas of potential difference (voltages) on the ground around the strike. If one of your legs is in the 100,000V area and the other is in the 10,000V area, then you have 90,000V between your legs :oo:

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Originally Posted by BobL

Or connection to any other active phase.

It also depends on the V.
With high voltage all sorts of crazy stuff can happen and you may think you have no electrical connection but suddenly what is high resistance at 240V breaks down and can pass enough current to be deadly.

Most folks don't realise they can be killed by lightning striking the ground near them. The million+ V lightning strike sets up brief areas of potential difference (voltages) on the ground around the strike. If one of your legs is in the 100,000V area and the other is in the 10,000V area, then you have 90,000V between your legs :oo:

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So true.

Not many get to play with HV stuff. I was lucky, after my trade I went off to uni. In my early days of engineering I was tasked to work with static and high voltage transients. Taught me a lot about how insulators become conductors!

Its interesting your point about lighting. I worked with a dutch engineer back when I was an apprentice, and he told me about an issue like that that occurred with grounding at a power station They shut a whole area off to public both on land and at sea due to electrocutions from difference in soil and water conductivity.