The £1300 AFDD consumer unit

That is the point Graham. You are assuming that because one conductor of a transmission line is "Grounded" the rules of induction change. This is not correct, the same current is induced into both conductors, whether one or the other is connected at some point to some other thing, even the Earth. There are other phenomena that happen at the point where the line becomes less balanced or the connection to Earth, such as signal reflection which is asymmetric, but at the cable lengths we are discussing at a very low frequency, the effects are unlikely to be huge voltages particularly as the field strength is not very high.


Mikes point is also very important, induction into a screened cable (SWA, Wavecon, PILC etc) , is greatly reduced by the screening efficiency of the covering, although it may be induced into the screen material. This is a potential problem with PME, where N & Earth potentials at the intake could be some way above Ground without a ground connection, thus the reference to foundation Earthing I made above.

That is the point Graham. You are assuming that because one conductor of a transmission line is "Grounded" the rules of induction change. This is not correct, the same current is induced into both conductors, whether one or the other is connected at some point to some other thing, even the Earth. There are other phenomena that happen at the point where the line becomes less balanced or the connection to Earth, such as signal reflection which is asymmetric, but at the cable lengths we are discussing at a very low frequency, the effects are unlikely to be huge voltages particularly as the field strength is not very high.


Mikes point is also very important, induction into a screened cable (SWA, Wavecon, PILC etc) , is greatly reduced by the screening efficiency of the covering, although it may be induced into the screen material. This is a potential problem with PME, where N & Earth potentials at the intake could be some way above Ground without a ground connection, thus the reference to foundation Earthing I made above.