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Somewhere along the line I picked up a suggestion from a forum posting or two that the DNO does not like you to connect an earthing rod to his "earth" - even though it is effectively just creating yet another, local to your installation, earthing point for the multiple ones already assumed to exist as a part of his PME installation.
But why?
What possible issue could it cause?
On the contrary, surely it is safer as it ensures that a person adjacent to the local installation will at least be offered a measure of protection against the dreaded, much discussed but in reality extremely rare "broken neutral" problem? Granted, if enough fault current is flowing in from outside of your location as a result of the JCB mediated cable breach in the street it could potentially (sorry!), depending upon the local ground conditions, pull the voltage on your local earth up, but even so it is surely still safer than not having a local earth reference at all?
The topic tends to come up in the context of "exporting" a PME earth along with discussion about the pros and cons of connecting outbuildings using a TT configuration and the point is generally and validly made when it does that the user of the installation must be protected from touching both the earth coming in on the run of SWA down the garden and the local earth provided by the earth spike as there is the potential (sorry again!) for the unconnected "earths" to be at different voltages.
But the scenario I am seeking to explore (purely for the purposes of further enlightenment, no actual or proposed project is involved here) is emphatically not a TT installation because the local earth rod would be connected to the earth coming in from the street.
By now I expect you are mostly wondering what possible reason one might have for wanting to construct such a "bizarre" system. Well, it is admittedly a bit of a minority sport, but one reason is that, if you are a radio amateur (and we are not talking the 2 metre band or handheld VHF transceivers here) it is very common to want to install a good solid local (& low impedance at frequencies > 50Hz) earth for your transmitter. A chap I know is such a person (weird I know, but somebody has to be
) and he has just had installed an EV charge point for his Smart car electric runabout. We got to talking about earthing and safety in the context of a broken neutral what with a tin car on a charger being very much the same scenario as a caravan and, as we all know, anything but TT on a caravan is verboten. He then offered up the information that it was alright because he has an earth spike for his transmitter which is also connected to the incoming earth from the DNO in the house.
That's the context, now let's have the opinions, personal abuse for my obvious misunderstandings, seasoned informed advice, and, of course not forgetting the usual off-topic banter which we all know and love so much.
But why?
What possible issue could it cause?
On the contrary, surely it is safer as it ensures that a person adjacent to the local installation will at least be offered a measure of protection against the dreaded, much discussed but in reality extremely rare "broken neutral" problem? Granted, if enough fault current is flowing in from outside of your location as a result of the JCB mediated cable breach in the street it could potentially (sorry!), depending upon the local ground conditions, pull the voltage on your local earth up, but even so it is surely still safer than not having a local earth reference at all?
The topic tends to come up in the context of "exporting" a PME earth along with discussion about the pros and cons of connecting outbuildings using a TT configuration and the point is generally and validly made when it does that the user of the installation must be protected from touching both the earth coming in on the run of SWA down the garden and the local earth provided by the earth spike as there is the potential (sorry again!) for the unconnected "earths" to be at different voltages.
But the scenario I am seeking to explore (purely for the purposes of further enlightenment, no actual or proposed project is involved here) is emphatically not a TT installation because the local earth rod would be connected to the earth coming in from the street.
By now I expect you are mostly wondering what possible reason one might have for wanting to construct such a "bizarre" system. Well, it is admittedly a bit of a minority sport, but one reason is that, if you are a radio amateur (and we are not talking the 2 metre band or handheld VHF transceivers here) it is very common to want to install a good solid local (& low impedance at frequencies > 50Hz) earth for your transmitter. A chap I know is such a person (weird I know, but somebody has to be
) and he has just had installed an EV charge point for his Smart car electric runabout. We got to talking about earthing and safety in the context of a broken neutral what with a tin car on a charger being very much the same scenario as a caravan and, as we all know, anything but TT on a caravan is verboten. He then offered up the information that it was alright because he has an earth spike for his transmitter which is also connected to the incoming earth from the DNO in the house.That's the context, now let's have the opinions, personal abuse for my obvious misunderstandings, seasoned informed advice, and, of course not forgetting the usual off-topic banter which we all know and love so much.
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