Neutral Protection

Three-Pole Circuit Breakers

Protection of the neutral is possible on a three-pole circuit breaker by connecting an external sensor.

For more information about the setting procedure, refer to Setting Neutral Protection.

MicroLogic trip unit	5.0 P, 6.0 P and 7.0 P
Setting	OFF (factory setting)	N/2	N	1.6xN

Protection setting	Description
OFF: Neutral unprotected	The distribution system does not require protection of the neutral conductor.
N/2: Half neutral protection	The cross-sectional area of the neutral conductor is half that of the phase conductors. The long-time current setting Ir for the neutral is equal to half the setting value. The short-time pick-up Isd for the neutral is equal to half the setting value. The instantaneous pick-up Ii for the neutral is equal to the setting value. For ground-fault protection (MicroLogic 6.0 P), pickup Ig for the neutral is equal to the setting value.
N: Full neutral protection	The cross-sectional area of the neutral conductor is equal to that of the phase conductors. The long-time current setting Ir for the neutral is equal to the setting value. The short-time pick-up Isd for the neutral is equal to the setting value. The instantaneous pick-up Ii for the neutral is equal to the setting value. For ground-fault protection (MicroLogic 6.0 P), pickup Ig for the neutral is equal to the setting value.
1.6xN: Oversized neutral protection	In installations with a high level of third-order harmonic currents (or multiples thereof), the current in the neutral conductor may exceed that of the phase currents under steady-state conditions The long-time current setting Ir for the neutral is 1.6 times that of the setting value. The short-time pick-up Isd for the neutral is 1.6 times that of the setting value, but may not exceed 10 In to limit transients and self-protect the installation. The instantaneous pick-up Ii for the neutral is equal to the setting value. For ground-fault protection (MicroLogic 6.0 P), pickup Ig for the neutral is equal to the setting value.

Four-Pole Circuit Breakers

For more information about the setting procedure, refer to Setting Neutral Protection.

MicroLogic trip unit	5.0 P, 6.0 P and 7.0 P
Setting	OFF	N/2 (factory setting)	N

Protection setting

Description

OFF: Neutral unprotected

The distribution system does not require protection of the neutral conductor.

N/2: Half neutral protection

The cross-sectional area of the neutral conductor is half that of the phase conductors.

The long-time current setting Ir for the neutral is equal to half the setting value.
The short-time pick-up Isd for the neutral is equal to half the setting value.
The instantaneous pick-up Ii for the neutral is equal to the setting value.

N: Full neutral protection

The cross-sectional area of the neutral conductor is equal to that of the phase conductors.

The long-time current setting Ir for the neutral is equal to the setting value.
The short-time pick-up Isd for the neutral is equal to the setting value.
The instantaneous pick-up Ii for the neutral is equal to the setting value.