Chapter G

Sizing and protection of conductors

Breaking of the neutral conductor

From Electrical Installation Guide


(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[1]

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.


  1. ^ In some coutries the rules applied for TN-S are the same as the rules for TN-C