IT earthing system
Behaviour on the 1st fault:
As the neutral is unearthed, the fault current ld does not flow. As voltage is not hazardous, the installation can be kept in operation.
Since the PIM (Permanent Insulation Monitor) has reported this 1st fault, it must be located and eliminated before a 2nd fault occurs
Behaviour on the 2nd fault:
If the fault concerns the same live conductor, nothing happens and operation can continue. However, when the fault concerns two different live conductors (double fault), a short-circuit occurs (as in TN). Breaking is achieved by the overcurrent limiting devices.
As in TN earthing system, the calculation of the short circuit current must be done to ensure the protective devices opening the fault circuit.
