Under normal circumstances the neutral in a three phase system takes away any current caused by imbalances in three phase systems and preserves the voltage between the neutral and Earth GME)
If the neutral is broken then the voltage between what was the neutral star point will wander around with respect to Earth. With perfectly balanced loads after such a break the difference in potential between the star point and GME will be zero, but as the 3 phases become more and more out of balance with each other the difference will increase between 0V and 400V
With the blue CNE slider set to healthy and dragging the arrowheads of the three vectors in the left hand circle to alter the loads per phase from 0 to 230A it can be seen that the voltages between phases and between phase to neutral are preserved.
After creating an imbalance try slidng the blue CNE slider to Broken to see how the voltage between phases to GME changes due to the neutralfloating towards the phase/phases with most loadon them.
If the voltage between this floating neutral (FN) and GME differs too much then installations can suffer from undervoltage or overvoltage. The monitoring of voltages between Earth and this FN is one method used to detect PEN faults on EVSE.
This is easier to implement on 3 phase systems where a theoretical star points voltage can be calculated and compared with earth potential. In single phase sytems a reference electrode can be installed to compare against the installations earth potential or the potential constantly monitored between line to neutral and causing the outgoing circuit to disconnect all live conductors (inc neutral) and the CPC of the circuit.
