"All Pole Disconnection Device with a 3mm contact gap&q

[bernardgreen]

If you ever get stateside monkeh check out some of the scary electrical practices they use and the wobbly plugs.

Not to mention the rickety wooden poles along the streets with tin can transformers hung precariously on the poles, each can feeding 3 or 6 houses. The cans are fed by something like 11Kv strung along the poles. And in some places there is an even higher voltage strung above that with big cans feeding the 11Kv every few hundred yards.

Under that there are main telephone cables with junction boxes hanging in mid air. A really untidy mess which hangs over tidy well kept front lawns in nice residential areas.

 

[ban-all-sheds]

higher amperage means a bigger gap so you don't get arcing..

Higher voltage, surely? i.e. it's the voltage which determines if an arc can jump a gap?

3mm?

Sometimes 3' isn't enough....

http://www.capturedlightning.com/frames/mpg/500kV_Switch.mpg

 

[ColJack]

yes, but I'm not on about that kind of arcing where the air itself becomes a conductor ( plasma isn't it then? ).
I'm on about breaking currents and the sparks and arcs you get then..

 

[MountainMan]

There is a suggestion that permanently fixed heating appliances over 2kW should be fed from its own dedicated circuit.

So is this "suggestion" a requirement or not. If it is, it's a "requirement".
I was just wondering, as I would have thought a suggestion is meaningless to the point in question.

 

[Master of None]

I think you need high voltage to initiate an arc but you can strike an arc with ELV and maintain it with high current (think electrode arc welding). So when the switch diconnects under load it is the same.

 

[bernardgreen]

The 3mm gap is considered wide enough to cope with any damage that might be caused by frequent arcing of the contacts when they are opened while on load.