In USA industrial plants the 3 phase busses have incadescent lamps tied 
to the phases, a lit lamp indicates a ground fault. Sounds like the 
isolation transformer might be more dangerous than without, in that 
there is a unknown.

John La Rooy wrote:
> On 1/23/07, Carl Denk <cdenk@alltel.net> wrote:
>   
>> Would not an isolating transformer still be a risk? Thinking the learned
>> ages ago, when working on electric, keep one hand behind you so the
>> current won't go from one hand to the other via arms and the heart. The
>> isolation transformer will eliminate the ground problem, but the issue
>> of wire to wire with 120 volts or so still exists.
>> :)
>>     
>
>
> Or 230 volts, depending where you are. In the long term, a ground fault
> could develop and then you aren't isolated anymore, but you don't know
> about it until someone gets zapped.
>   
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