What does "Neutral Protection of 50%, or 100%, of the phase setting" in ABB MCCBs mean?

[Haroon Baloch]

In all 4-pole ABB MCCBs, above a certain range, it is mentioned that that there is an option to choose 50% or 100% Neutral protection. Specifically, it says "The four-pole circuit-breakers are always supplied with the neutral protected by the trip unit and with protection of the neutral at 100% of the phase setting for settings up to 100 A. For higher settings, the protection of the neutral is at 50% of the phase setting unless the protection of the neutral at 100% of the phase setting is required."

What does it mean to have Neutral protection at 100%, or 50%, of the phase setting? If there is any manual where I can read about this type of protection, then please give reference to it.

 

[RRaghunath]

50% and 100% refer to the amount of unbalanced loading that is allowed in the phases. If it is 100%, the amount of current that flows in neutral conductor will be equal to that in phase conductor and if it is 50%, the current in neutral conductor can be 50% (max) of that in phase conductor.
The protection unit in MCCB monitors the current magnitude in the neutral and provides protection against excessive unbalanced load that can cause overheating of neutral conductor/connections, based on 50% or 100% selected.
For literature, you can google with 'ABB MCCB protection release'

 

[Haroon Baloch]

Thanks RRagunath. This makes sense. Thanks for the clarification.