Get back to the terminal, to the Power card. The room you are mainly interested in is the "Comm. Center", but you won't be able to turn the power there (as well as in other rooms) because the generator doesn't have enough power. If you want to unlock them, you will have to turn off the power in one of the two nearby rooms - you can get into the Comm. Station by following either path, but the final result differs greatly.
The first place is the previously visited production hall. You have to get there and switch the lever on the other side of the room, which will disable power in the room, as well as inflict pain to the robot lying on the ground. However, it has an advantage - if you turn the power off in this room, you won't have to deal with the enemy, so getting to the upper floor should be a lot easier.
The second solution to this problem can be found in the tunnel, where the corpse from which you took the ID is lying. Get back to the said tunnel, run past the corpse and turn to the left, until you reach a room called "Flow Center". Directly in front of the entrance there's a switch, and right next to it a note warning you that using the switch may turn out bad. Flip the switch and prepare yourself, because as soon as the power is shut down, the enemy from the lower floor will enter the area (through the same staircase as you).