How to test or simulate preferential trip onboard ship?

Easy, get the cook to turn on all the hotplates, then get the boatdriver to veer out a couple of shackles of anchor cable. That will overload your switchboard

Used to be easy on Old Time ships but there is usually a much bigger reserve of power available from generators now.
You might have to get an Electrician in with Current Injection Kit, to test the trip just like you do for testing main Breakers.

BP