[RE-wrenches] Fwd: Grounding on a glacier??

[Hugh]

At 15:33 -0700 24/7/09, toddcory at finestplanet.com wrote:
>Hmmm, I wonder how the birds can sit on those same HV wires and do 
>just fine? If a wire is not referenced to the ground you are 
>standing on, touching it would not give you a shock unless you were 
>also in contact with the other conductor it is referenced to.

It's a safety issue only when there is a fault.  In the event of a 
fault that connects a hot wire to the battery system then the battery 
system will become hot.  Making sure that neither pole of the battery 
is grounded will not prevent this in fact it will make it possible. 
If the HV system has a grounded conductor then the other one will be 
hot and any associated wiring systems need to be grounded for safety 
in case of contact.

At 15:48 -0700 24/7/09, toddcory at finestplanet.com wrote:
>  A single pole switch will stop the current regardless of whether 
>one of the conductors is referenced to ground or not.

If one pole is neutral and the other is switched off then the circuit 
is safe.  But if the system is 'floating' and you only turn off one 
pole then the circuit is still live.  You have stopped the current 
but you have not necessarily made it safe to work on.  If neither 
pole is grounded then both must be treated as potentially hot. 
That's why it's actually more expensive to have 'ungrounded' systems. 
You will still need to have grounding conductors for safety and you 
will need to double the number of fuses, breakers and switch contacts.
-- 
Hugh Piggott

Scoraig Wind Electric
Scotland
http://www.scoraigwind.co.uk
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