Chapter G

Sizing and protection of conductors

Breaking of the neutral conductor

From Electrical Installation Guide
Home > Sizing and protection of conductors > The neutral conductor > 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[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