User Manual

Description

2.3 Protection system

3WA Air Circuit Breakers

Equipment Manual, 05/2021, 92310000002-03

2.3.5.5 Neutral protection N

The neutral conductor can be protected against overload and short-circuit with the electronic

trip unit. The neutral protection consists of a separate overload protection and a common

short-circuit protection for the three phases and the neutral conductor.

The overload protection has the setting I

N. The delay, the overload characteristic, and the

thermal memory correspond to the settings of the overload protection of the three phases.

For four-pole circuit breakers, the setting I

N of the overload protection is limited by the

maximum rated current I

n max of the circuit breaker.

For the short-circuit protection of the N-conductor, the settings of the short time ST and the

instantaneous short-circuit protection INST are adopted.

Note

For a 3-pole circuit breaker, an external current sensor (N-CT) is required to protect the

neutral conductor, see Chapter External current sensor for neutral pole (Page 313).

Characteristic