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3 Phase + Neutral 400/230V unbalance:

Nick Parker

I came across a circuit drawing for lighting distribution panel 3P+N (400/230V) .

There are 3 phase and 1 phase (Phase to Neutral) loads connected to this Distribution panel. Apparently, there would be unbalance current between the phases due to the single phase loads as it is not connected evenly across all the phases.

Do the breaker trips for the unbalance current due to the current flowing in the neutral? Do I need to increase the earth fault setting? Typically what is the earth fault setting for this configuration? Do I have to care of any other issues associated with it?

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    On a standard three phase four wire system as described in the O/P some unbalance is normal and almost impossible to avoid. Even if the loads are perfectly balanced, there is no way to ensure that all lights will be used at the same time.

    A three pole circuit breaker wont trip on this unbalance, neither will a three phase and neutral circuit breaker. A true 4 pole circuit breaker MIGHT trip, but only if the neutral current exceeds the rating of the device, this is most unlikely with a full sized neutral conductor and circuit breaker to suit.

    Presuming that the earth and the neutral are entirely separate, as they should be, then the correct setting of any earth fault protection is not influenced by neutral current.

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  • 0

    On a standard three phase four wire system as described in the O/P some unbalance is normal and almost impossible to avoid. Even if the loads are perfectly balanced, there is no way to ensure that all lights will be used at the same time.

    A three pole circuit breaker wont trip on this unbalance, neither will a three phase and neutral circuit breaker. A true 4 pole circuit breaker MIGHT trip, but only if the neutral current exceeds the rating of the device, this is most unlikely with a full sized neutral conductor and circuit breaker to suit.

    Presuming that the earth and the neutral are entirely separate, as they should be, then the correct setting of any earth fault protection is not influenced by neutral current.

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