Reverse power trip, under certain conditions

So Thanks before hand, Alright so here is the problem. I am running 3 generator on an oil rig, Gen 1 and gen 2 are on all time, gen 3 is only used when needed. Today i was told that gen 3 was tripping, there was 2 alarms on the woodward egcp-2 screen,

alarm 1 : Gen low frequency, alarm 2 : Reverse power alarm.

Now i know the basis of reverse power, but i was at this rig today for 5 hours, gen 3 ran the whole time sync'd with gen 1 and 2. It was load sharing fine, and did not trip during normal drilling. I have been told that when they Ran the drawworks down from midsection to the drill floor gen 3 tripped, ill be getting more info once im at the rig, and rig specialists know where to start looking? And any additional info you need to know let me know thanks