VOLTAGE BETWEEN THE GENERAL MASS OF EARTH AND A PME NEUTRAL/EARTH

sorry to hear you have blown one - in normal use the resistance of the ground around the electrode (Ze) would limit the peak current, so a dead short L-E fault on a TT system (the common use case for these trips) would normally be current limited and the trip coil would have  survived. I suspect your Variac near the 100% setting is far lower impedance, approaching that of the mains L-N loop, and the fault current too high, and the opening time too long to save the coil. (As like an MCB the mechanism won't speed up with increasing current beyond a certain point.)


It is an interesting failure mode to have, as it is very much fault to danger, as if this was in a real installation it would now have lost all earth reference to terra-firma, as well as all ADS.


I think the great unclear quantity in normal use would have been the source impedences of the fault (mains wiring plus a rather nebulous weather dependent earth path)  and maybe the impedance of the  ELCB coil - together these are forming a voltage divider of the permissible touch voltage.  If for example the assumed electrode impedance was 100 ohms, and if we assume the trip coil reactance similar, then for a 50 V touch voltage the coil would need to go nearer to  25volts.


Have you a feel for the operating current as well as the voltages of the ones you have ? I'd be assuming a significant impedance in the trip, to intercept enough V * I to operate it, or it would need a very good low resistance electrode  to operate properly,  but this  may be my intuition misguided , they have been  a thing of the past all my life pretty much, and therefore not given much time, other than perhaps the time to unscrew them.

From discussion with aged relatives, tripping when there was a thunderstorm was not uncommon. Equally, given casual mention of shocks from sinks and taps when a neighbour first got an electric kettle, there may have been other issues at that time.

sorry to hear you have blown one - in normal use the resistance of the ground around the electrode (Ze) would limit the peak current, so a dead short L-E fault on a TT system (the common use case for these trips) would normally be current limited and the trip coil would have  survived. I suspect your Variac near the 100% setting is far lower impedance, approaching that of the mains L-N loop, and the fault current too high, and the opening time too long to save the coil. (As like an MCB the mechanism won't speed up with increasing current beyond a certain point.)


It is an interesting failure mode to have, as it is very much fault to danger, as if this was in a real installation it would now have lost all earth reference to terra-firma, as well as all ADS.


I think the great unclear quantity in normal use would have been the source impedences of the fault (mains wiring plus a rather nebulous weather dependent earth path)  and maybe the impedance of the  ELCB coil - together these are forming a voltage divider of the permissible touch voltage.  If for example the assumed electrode impedance was 100 ohms, and if we assume the trip coil reactance similar, then for a 50 V touch voltage the coil would need to go nearer to  25volts.


Have you a feel for the operating current as well as the voltages of the ones you have ? I'd be assuming a significant impedance in the trip, to intercept enough V * I to operate it, or it would need a very good low resistance electrode  to operate properly,  but this  may be my intuition misguided , they have been  a thing of the past all my life pretty much, and therefore not given much time, other than perhaps the time to unscrew them.

From discussion with aged relatives, tripping when there was a thunderstorm was not uncommon. Equally, given casual mention of shocks from sinks and taps when a neighbour first got an electric kettle, there may have been other issues at that time.