The permissible touch voltages specified in EN 50 122-1 also apply to power supply installations, where faults with earth contact within the three-phase medium- and low-voltage systems must be taken into account. For this, the potential increase of the earthing system is to be treated in the same manner as the rail potential.
The values for the permissible touch voltages and rail potential in the short-circuit case shown in Table 12.12 take account of the fault disconnection duration of modern protection devices, which are less than 100 ms.