Shocking (!) demo of the danger of arc flash

[AlanBeckett]

Get a Permit, Lock it OFF, Check that it's DEAD, start work.
Alan

[glowinganode]

This is the procedure I follow;
Risk Assessment
Method Statement
Permit To Work
Isolate
Lock Off / Tag Off
Complete Isolation Register
Prove Isolation
Carry out works
Tool check
Visual check
Megger test
Re-energise circuit
Sign off PTW / lock-off register.
This only helps when you can isolate the circuit.
Probably the biggest hazards are Live working / testing and switching operations.
Rob.

[beam me up schottky]

Thats pretty thorough Rob, is that standard working procedure in the industry ?

[glowinganode]

Yes, certainly on the LV (less than 1000V) side of things, and other safety critical sites such as quarries and refineries
When working on HV, there are additional procedures such as earthing down of conductors, cable spiking, issuing of certificate of isolation, Authorised Persons and clearly defined safe zones.
Really the first two are the most important, Risk Assessment and Method Statement.
These demonstrate you have identified the risks and have a clear objective and a planned and safe method of working.
Each risk or hazard is ranked on a scale of 1-5 on likelihood and consequence, generally speaking if the product of the two is greater than ten, additional measures need putting in place.
It is quite a long winded procedure, but has become much more commonplace nowdays, and is no longer as frustrating as once was now people are used to it.
Rob.

[dennishoy]

I've done a lot of work restoring heritage DC traction on the Southern Region electrified railway.
Here is a bit of video of one scrap-condition locomotive (the light blue one) I got working again a couple of years ago taking a mere 1000-1200 Amp in the snow at Eastleigh Works.

The supply voltage has recently been raised from 750V to 850V and the yard breaker is set for 12,500 Amp.

The layer of ice on the live rail stands no chance and melts in seconds.

http://www.youtube.com/watch?v=CYAaJbAsFG0

[Mark Hennessy]

Each exchange had a battery room. The batteries were made up of lots of large concrete cells, cast in-situ, lead acid type. Each was about the size of an under-counter fridge, from memory. The idea was to keep the exchange runing for up to an hour, in case the standby generator had starting problems! No smoking in the battery room or bang!

Interesting - I've only seen the types with conventional batteries. I thought that concrete was sensitive to acid attack - was it a special mix or lined with something?

Cheers,

Mark

[Yorkie]

Interesting video Dennis - the 'fireworks' on the frozen lines is impressive! Thanks for 're-energising' a thread that had gone to sleep.

'It's Volts that jolts, and Mils that kills'. A live chassis radio via an isolating transformer is as close to dicing with death as I want to get. I'm too young to die, and too old for nasty shocks!! :omg: