The wiring in the trailer doesn't change when you plug into your own generator instead of the utility company's generators (which may be many miles away somewhere on the grid). The only negative with a surge protector may be that it detects the unbonded ground and neutral on the generator as an open ground and complains about that, if it's a decent EMS unit. The solution to that is pretty simple: either bypass the EMS, if it has a bypass switch, or plug a bonding plug into one of the outlets on the generator. A quick search of the forum will show what a bonding plug is and how to make one; it just connects the neutral to the ground on the generator.
