We have (3) outdoor gas turbine generators (480v/3ph, 1MW each)
power a 480v/3ph parallel switchgear also sits outside.

The switchgear is then feeds a step up 480v:5KV transformer,
the output of xfmr connect to an existing underground 5KV feeder
at one end, the other end of this 5KV feeder is powered from utility
as backup source via a MV switch (note: this 5KV feeder feeds
several buildings in the area)

Question: Does nec require to ground the parallel switchgear
above? i.e bond neutral to equipment ground bus
and then connnect to the ground rod, maybe?

All turbine generarors were grounded via a ground wire connect all
generarors and binddto a triad ground rods.