How do you overload the fuse box in the gladiator pit?

You have to use the remote baterang to go through a gap in the door and guide it to the left where the fuse box is

U don't use the electric thing look up in the middle shoot your remote batarang up there and turn left down the stairs hit the switch

There are two places you can shoot your remote control batrang through, there's a little gap above the door on the left side of the room, or you can shoot it through the middle doorway, where Penguin was standing, then go left. Either way, aim for the red button. If you can't do it, then right after you shoot the batrang let go of the triggers THEN hold down the left one and that will slow down the batrang.

U don't use the electric thing look up in the middle shoot your remote batarang up there and turn left down the stairs hit the switch

Through the electric field, up the stairs, out through where Penguin was standing into the main pit, in through the one open door, then through one of two small windows down the hallway to hit the fuse box.

There are three gates in a row under the balcony where the Penguin was standing. The first one you can slide under. The other two are locked. If you have previously turned off the electricity you'll have to go back up and turn it on again to create an electrical field over one of the fence doors. Guide your Batarang through the electrical field, then guide it under the first gate (the one you can slide under.) Guide it to the right, around the corner. You'll see an opening in the window. Steer through the window to hit the fuse box.