[time-nuts] GPS shielding by power lines?

David Ackrill dave.g0dja at tiscali.co.uk
Sun Aug 10 08:01:48 EDT 2008

Alan Melia wrote:
> Hi Tom Brilliant I hadnt thought of the fields actually affecting the
> operation of the electronics! that is certainly something that might be
> interesting to check. I note there lines have three "phase" feeds but no
> neutral wire so they must use ground as the return path to any unbalance
> currents.(?)

On the UK 11kV overhead network the phases are all distributed without a 

At the 11kV/415V transformer the HV side is delta wound and the LV is 
star wound, so the neutral/earth for the supply is taken from that 
point, not from the HV side.  So, you are correct, the connection to 
"the general mass of earth" at the transformers is used as the return 
path.  Which is why there are regulations about the acceptable earthing 
impedances at HV/LV transformers on an overhead supply.  Tales of 
Linesmen watering earth rods to get away without having to drive in more 
earth rods and connect up to the transformers, and so avoid having to 
drive rods into hard ground, are legion in the ESI...

In fact, if you look at most of the overhead high voltage distribution 
systems, they are all phase only, no neutral...

Dave (G0DJA)

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