Breaking of the neutral conductor
(see Fig. G68)
The need to break or not the neutral conductor is related to the protection against indirect contact (fault protection).
In TN-C scheme
The neutral conductor must not be open-circuited under any circumstances since it constitutes a PE as well as a neutral conductor.
In TT, TN-S and IT schemes
In the event of a fault, the circuit-breaker will open all poles, including the neutral pole, i.e. the circuit-breaker is omnipolar.
The action can only be achieved with fuses in an indirect way, in which the operation of one or more fuses triggers a mechanical trip-out of all poles of an associated series-connected load-break switch.
- In some coutries the rules applied for TN-S are the same as the rules for TN-C