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6LE007331A
Neutral protection is available as standard on 4P circuit breakers and as an option with the
addition of the accessory ENCT external neutral current sensor on 3P versions. It is particularly
useful when the cross section of the N conductor is adapted in relation to the phase
conductors.
It uses similar tripping curve characteristics as the long time delay, short time delay and
instantaneous protection parameters.
Neutral protection curve
I (A)
t (s)
tsd
N=100% N=50%
lr li lsd
Neutral protection
Adjusting the neutral protection
N coefficient adjustment range (%) Parameters impacted
OFF - 50 - 100 - 200
The coefficient is applied to the adjustment
value of the Ir and Isd thresholds for the
phases.
For a setting at 200%, the maximum value of the neutral protection cannot exceed the
maximum rating of the circuit breaker.
E.g. for a 1600 A circuit breaker with a rating plug of 1000 A, the neutral current protection will
be limited to 1600 A.
The Ii (Instantaneous protection) remains identical to that of the phases.
The N coefficient is adjusted using the N adjustment dial.
On a 3-pole product and in the absence of an ENCT external neutral current sensor:
- it is advised to keep the setting of the N encoder dial to OFF (factory setting by default),
- if the N encoder dial is set to 50 %, 100 % or 200%, the protection will remain inactive.
Neutral protection time delay
The time delays for neutral protection remain identical to the phase time delay adjustment
values.
The types of protection device
3.6 Neutral protection