Answer / omar aziz

Mostly standards (IEEE , ANSI) recommend 5% however, in
practical situations where a sound judgment can be made you
can strech it upto 10 - 15% at the load bus depending on
your min. voltage allowed by the motors/ other equipment.

Motors can usually start at around 80% rated voltage ,
however other electronic equipment such as UPSs are very
sensitive to voltage variations.

Consider the load before selecting this threshold otherwise
stick to 5%

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