What is a good value of (I2)^2t (K-Factor) for protection of induction motors? There is not much literature for this out there and I have seen number vary anywhere from 20-120. Anyone has more insights into this?
The reason they are a bit vague is that there is no "one size fits all" solution. The best approach is the smallest your application will permit. Since this is normally used to trip on no start or slow start, the least motor heating while avoiding nuisance trips, the better. And that almost entirely depends on the application. Is that vague enough?
If the "Motor" is a Critical Asset to your operation then use of a Neg-Seq relay is warranted as the simplest approach.
Setting the relay will be identical to that of a generator app. The trick is to get an IsqT "value" from the motor manufacturer. If the manufacturer is uncooperative, then contact me off-forum for the procedure.