Earthing neutral

mapj1:

It might - consider this rather simplified illustration - you will have to imagine the blackboard and the chalk...


Imagine you are holding the bare PE, but your feet are in good contact with terra-firm earth, but outside the near field of the electrodes .

Consider what happens when the TX faults HV phase to frame. The HV phase voltage goes down, and at the same time the HV and LV earth voltages at the fault

both come up to meet it part way.

The area of a circle a rod length or two around the electrode goes up a bit of course, but only the earth really near the electrode(s) rises to full fault voltage, then the volts slope off to almost nothing by 2 rod lengths radius. It is better with a large area mesh electrode of course.

Let us assume the bit of ground you are standing on remains at or near 0V

Ouch.


Now repeat that thought experiment, but now with your hand on a similar PE with a mm or 2 of green and yellow stripy plastic between you and it. Not so much Ouch.

The surge is still bad for kit further along the LV network of course, but the PE = CPC on the LV side is usually multiply earthed on the load side of things as it is bonded to water pipes and so on, so while the end near the transformer may rise to a few hundred V, the bit near the kitchen taps might only rise by a fraction of that.


There is also a cultural/ historical aspect, as around here bare earth wires more generally are pre1966 , and is seen by many rather like cotton or rubber insulation, asbestos wadding, leadwork and various other things as indicating a "state of the ark"  installation, folk just do not expect to see bare wires for any function.

mapj1:

It might - consider this rather simplified illustration - you will have to imagine the blackboard and the chalk...


Imagine you are holding the bare PE, but your feet are in good contact with terra-firm earth, but outside the near field of the electrodes .

Consider what happens when the TX faults HV phase to frame. The HV phase voltage goes down, and at the same time the HV and LV earth voltages at the fault

both come up to meet it part way.

The area of a circle a rod length or two around the electrode goes up a bit of course, but only the earth really near the electrode(s) rises to full fault voltage, then the volts slope off to almost nothing by 2 rod lengths radius. It is better with a large area mesh electrode of course.

Let us assume the bit of ground you are standing on remains at or near 0V

Ouch.


Now repeat that thought experiment, but now with your hand on a similar PE with a mm or 2 of green and yellow stripy plastic between you and it. Not so much Ouch.

The surge is still bad for kit further along the LV network of course, but the PE = CPC on the LV side is usually multiply earthed on the load side of things as it is bonded to water pipes and so on, so while the end near the transformer may rise to a few hundred V, the bit near the kitchen taps might only rise by a fraction of that.


There is also a cultural/ historical aspect, as around here bare earth wires more generally are pre1966 , and is seen by many rather like cotton or rubber insulation, asbestos wadding, leadwork and various other things as indicating a "state of the ark"  installation, folk just do not expect to see bare wires for any function.