[Elecraft] I need some grounding-strap guidance, if'n you please

[David Woolley (E.L)]

Rich wrote:

> trouble call for low voltage we found that both sides measured 120 VAC
> unloaded at the transformer and at the entrance box. with load it dropped a
> few volts with a heavy load it dropped about 5 volts. eventfully we
> discovered that there was a hidden break in the ground wire and the house
> was getting close to proper voltage with the lousy ground at the bottom of
> the pole and the house ground rod. Go Figure!  
> 

This sort of fault condition is exactly why it is important that all 
grounds be connected together within a building in the UK.  Modern urban 
distribution systems use a system called Protective Multiple Earthing 
(PME), in which the neutral (I think it was mis-named ground, above) is 
grounded at multiple points on its path from the substation, but there 
is no dedicated ground wire back to the substation, nor is there a 
ground rod per property.

In this system, the building electrical ground is connected to the 
neutral where the cable enters the property.

When the sort of fault described above occurs, there can be a 
significant difference between the potential of the earth around the 
property and the nearest grounding rod.  It may not be enough to 
directly kill you, but even if not, the shock could precipitate a fall.


-- 
David Woolley
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