Trainee asking for an explanation on something I found today (arcing cable)

[Silly Sausage]

You bet!

Try getting 12KV up your arm.

I was knocked unconscious when I hit the wall but walked away.

Like coming home from pub

 

[Knobhead]

I'm used to it.

 

[GMES]

You bet!

Try getting 12KV up your arm.

I was knocked unconscious when I hit the wall but walked away.

What about the poor wall.

 

[Darkwood]

Not the same but I got 1million volt static discharge through me when I was in a textile mill, the machines had grounding rods that you discharged the materials with before walking beyond a point, thing is I was carrying a ladder and negotiating the machines when it lept a few feet to my ladders....... took me down like a lead weight - I tell you now, you know when you been hit by that static charge.... only a few lads there had received it and they say you never get complacent ever again.

 

[Silly Sausage]

I'm used to it.

Me and you both!

 

[PEG]

Was it a all male school then?

It certainly was...but for a handful of lady teachers...only one being the content of a young pottery students dreams.

Sadly,her interest in my hormone filled teenage shell,was limited to derision of my glaze application...:icon12:

 

[Mighty Chum]

My sparks asked me to watch the sign whilst he got the manager, having stood watching it for a few moments and taking the photos of my own accord I decided to turn it off of my own volition. Having read this thread I am realising what a silly thing that may have ended up being. I'm 28 years old so do most of the work we are offered, not to the same speed as my sparks but to a high enough quality he's willing to cert it once tested. I think that may have created a bit of hubris. Did not realise the transformer would kick out such a high voltage. To think I was a bit worried about changing lights in an 11lkv room I feel a bit silly just walking over and turning the isolater with no one around.

Chalk that up to experience.

 

[Marvo]

Yeah as Darkwood pointed out earlier in the thread when arcing faults occur at that voltage there's a high likelyhood that anything in the area could give you an unwelcome whack and even if the supply is from an RCD it won't protect you. Your mentor should really have been aware of the unusual hazards of such an installation but at least there was no incident or injury and hopefully you'll recognise the dangers immediately yourself in similar circumstances future.

 

[UKMeterman]

Another thing to learn is that if you hear anything HV start hissing, leg it.. Corona discharge is when the insulation is starting to fail in a big way, and if it is a HV supply you don't want to be near it when it fails!

 

[Engineer54]

The installation is very shoddy and these things are a notorious fire hazard at the best of times. 9 times out of 10 any arcing fault will be on the secondary side that supplies the neon tube, not on the supply side. They can produce up to 20 KV or thereabouts which makes the secondary wiring very prone to arcing. If you get a whack off the secondary wiring it will be a defining moment in your life that you won't forget (assuming you live to tell the tale). Where I am it's law that this type of transformer is supplied by a firemans switch on the 230v supply. The switch has to be mounted in a visible location and easily accessible/operated with a 2 meter pole.

View attachment 28110

That used to be the case in the UK, but found to my amazement on the last UK project i worked on, that the fire chief can negate that regulation. This happened on a large shopping complex (over 400 shopping outlets) where i am convinced the local fire chief took a back hander by allowing banks of these firemans switches covering several shopping outlets, be positioned in unmarked cupboards located in a service corridors. I tried everything to get that decision revoked/reversed, but all to no avail. I did make an official protest copied to all parties concerned, but it seemed that aesthetics means far more than the safety of firemen, shopworkers and the general public as a whole... That project opened my eyes in several other areas as well, just how much standards had fallen overall in the 20 odd years since i had last worked in the UK!!

 

[UKMeterman]

To get an idea of what I mean get some thin card, toblerone box has worked in the past, and put two pieces of cooking foil, on top of each other with one layer of card in between. Set the megger to 1KV and test between the foils, taking care not to go ouch yourself!!