Using outlet box with power and 3 neutrals(tied together/insulated) I want to use for adding a light fixture. Separated wires and found voltage on one of the neutral wires (measured ground wire to N). Any condition where power on the neutral lead is OK?

How or what did you use to test for the power on the neutral? And are you sure it a neutral wire from the start?

First off, you separated these wires with the power ON??
If so that almost precludes you from doing any further electrical work. :rolleyes:
This was not a smart thing to do.

Yes, there are times you will find "power" on an actual neutral wire. One is a back feed from a load on the circuit

Used a VOM, measured from ground wire to the 3 white leads, tied together with wingnut.
One of them measured, range from 38 to as high as 90vac.

That voltage gets backfed by filters and such in electronic devices. (By itself, it's no cause for alarm. A steady voltage or ~60 V would be worth investigating. With no appriciable current being drawn by the VOM, the voltage will be all over the map.