It may be a separately derived system, it depends on if the inverter is a line interactive or island type unit. The inverter interfacing from a wind turbine to a household electrical system is essentially the same as PV inverter interfacing.
Line interactive inverters are available that will determine if 60 Hz power at the proper voltage is present on the line side terminals. If there is power present they will turn on the inverter circuitry and feed power from the turbine/panels into the household electrical system. If there is not an external voltage applied to the line terminals then a line interactive inverter will not operate. This is a safety requirement so the inverter will not backfeed the grid if the grid is down. I believe line interactive PV units are listed to UL 1749 to ensure they will drop out if grid power goes down.
Island type inverters have the capability to feed power to the house when the grid is down. Different manufacturers structure their systems differently in this case. I used SMA Sunny Island inverters to charge and invert from the battery bank and also provide the required grid isolation. I had separate line interactive PV inverters to get power from the PV panels to the house and battery bank. In this case the Sunny Island would generate 240V power from the battery bank, and the line interactive units would interpret this as grid power and turn on.
You would have a separately derived system with the island type inverter, not if you only used a line interactive inverter.
