Steve Smith wrote:
> I can tell you that the safety distance on 400kV is 4 Meters....
> Still a little close for me...
>   
Probably OK to touch if you are NOT touching anything else. Maybe your 
hair stands out :0

Anode of CRT is about 25kV. 1/16th

4m  sounds reasonable. :-)   But I'm not going that close in case the 
cable moves or I slip.

-48V from a charger/battery set could be 65V to 70V  from charger or a 
little more if battery connection is loose?

110V AC is actually about 140V peak. Building sites here have to use 
centre tapped earth 110V AC via certified transformer for safety, which 
would be 70V peak to ground. (Household electric here is all 220V to 
230V AC 50Hz).

So someone decided that the the safe limit is over 70V (assuming a 
margin) and using 12V batteries (or 6x 2V cells in one case) they 
decided a nominal -48V is probably worst case 65V to 70V (56V normal 
full charge. Adding another 12V (nominal 60V instead of 48)  would be 
70V at full charge and about 85V if battery fault and charger running.

You don't want to stand in a wet trench with maybe 85V :(

I'd always been told in College and BBC that the nominal -48V was 
highest nominal system volts for safety (bearing in mind it's not 
actually -48V or -50V historically, but from 24 x Lead Acid cells or 4 x 
lead acid Truck/car batteries). Which obviously would be a lower voltage 
than the generally regarded safe voltage.


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