This location is tied to one of the tasks in the main quest “Cleansing the Land”. Once you obtained the Wind Farm kill switch code, you can go to this location and power down the wind farm which in turn will bring down Far Harbor's defenses. This will obviously result to the town's destruction.
The security door doesn't have power so you have to find four industrial-grade fuses scattered in the room. Place all of them in the fuse box to restore power. Open the door and prepare to take out the area defenses. There are three turbine control rooms. The middle is Turbine #2. The doorways have the numbers marked which turbine rooms they lead to. Each turbine room has at least two ceiling-mounted turrets. The entire shed has two assaultron dominators that protect it as well.
The terminal you need to use to turn off the wind farm is located in Turbine #3. There's a steamer trunk behind the terminal as well.