Flash Overs

[JohnW2]

I am autided every month by 2 different people, one from my company and another from the company we sub to. They watch you do 1 job and carry out 2 post completes on previous jobs. The new bloke from the sub company has a little habit of arriving early (all our appointmeents are timed) and parking a ways down the road, he will watch you enter the property and wait 15 minutes and then go in after you and see if you have the PPE with you and the relervent test instruments are being used.

Do you know when these audits are going to happen? If so, presumably only a fool (in more ways than putting his/her own life and limb at risk) would get 'caught out'. It's presomably when there's is not anyone looking over one's shoulder that sloppiness or dangerous practices may creep in.

Kind Regards, John

 

[Wontdothatagain]

the only time i know that i am getting audited is when the MOCOPA man comes out and that is like an audit on steroids

 

[Wontdothatagain]

There was a flashover in the Liverpool area last year, a DNO op was re-inserting a fuse and created a L to N fault. He had sever burns to his hands and arm, i heard that he lost the arm but i have not had confirmation of that yet.

No PPE was worn

 

[mattylad]

Do you not turn the power off before pulling these?

 

[Wontdothatagain]

No, the next point of isolation is the DNO,s substation.

This is the whole point of wearing the correct PPE, if you do wear it and a fault acurs, you are protected as in the pictures at the beging of the thread.

 

[RF Lighting]

You're not thinking of the jointer who hacked through a live feeder at the new Gateacre school site in Liverpool are you? It would have been around July 2011.

He was not inducted onto the site, was not wearing PPE, and was hospitalised as a result.

 

[Wontdothatagain]

No this was a open circuit on a servise fuse in a pub late one evening, he pulled the fuse replaced it but when he put the carrier back in, flashover.

 

[Spark123]

I'm not surprised, given what I have found stuffed in fuse holders in pubs.

 

[Porque223]

I'm thinking that the energy will be a lot greater on the supply side of the 100A fuse and that will depend on external factors such as supply impedance, fuses, transformer size and so on. A fault on the downstream side will be less owing to the 100A fuse let through.

Switching off a 240v/20A wall oven had the 240.0 v measured at the panel increase to 240.4v which means the impedance looking upstream into the power grid was 4/20 = .02 ohms.
240/.02 = 12,000A short circuit current but the transformer is right outside my house.

 

[Spark123]

I take it they do that a lot over the pond, having lots of little transformers local to the houses.
Do they not have proper test instruments for this over there? My loop tester does PSCC and PEFC giving a direct readout.

 

[JohnW2]

I take it they do that a lot over the pond, having lots of little transformers local to the houses.

If they do, and if their cable sizes are roughly comparable with ours, then they would have to be very 'local' to getthe sort of figures we're hearing about. 0.02Ω would only allow one about 7 metres total in 16mm²; that wouldn't even get from my front door to the road! Maybe the houses are also built on 'compact' plots, with walls very close to the boundary!

Kind Regards, John

 

[Wontdothatagain]

It is very common in the states for each house or two to have there own tranney

 

[JohnW2]

It is very common in the states for each house or two to have there own tranney

Interesting. Is that because they tend to be widely separated and/or because of the currents required with 110/120V supplies? Otherwise, it doesn't sound as if it would be very cost-efficient.

Kind Regards, John

 

[Wontdothatagain]

I think is is more to do with their voltage/current but i cant say for sure.

 

[JohnW2]

I think is is more to do with their voltage/current but i cant say for sure.

In comparison with here, a combination of the higher currents needed (at 110/120V) and possibly larger distances between properties would, I suppose, argue in favour of keeping LV wiring to a minimim.

Kind Regards, John