I don't understand. Why no service panel? That is important, correct? Perhaps I am just getting it wrong. By service panel, do you mean that box with fuses inside? Then you have a handle that you move up or down to switch on and off?
Sorry you misunderstood, the barn had no service panel (breakers or fuses) inside just wires, outlets, switches and sockets. Kenny pointed out that the breaker inside the house service panel would be the overcurrent/short protection. Another convenience of a service panel inside an outbuilding is you can shut off the power to that location without going back indoors...as I was adding to the circuits inside the barn it was really easy to work in the newly lighted areas, then temporarily shut off all current to make the final hookup to energize the new wiring. The farm I live on originally had (get this) 60 amp service in the house (900 sf) and one circuit went outdoors to a light pole, that pole had a sub panel that had underground wires running to a well, two large barns, and the smaller barn I have been working on...FOUR buildings running off 60 amps but I almost never blew any fuses.
To all, I have been working with electrical wiring for 25 years, have done major work but only got zapped once, and it wasn't my fault. I moved here in '89, the former tenant of the house was a long term renter, the range ran on a sub panel with cartridge fuses, one time a range fuse blew and not having a spare, HE WRAPPED THE BLOWN FUSE IN HEAVY ALUMINUM FOIL AND PUT IT BACK IN !!! When he moved out after I purchased the place, he left me a note saying the range fuse needed replacing...I got new ones, put a board on the concrete basement floor (smart move) stood on that and tried to pull the block of range fuses...the renter had overlapped the foil and it made the sub panel live, even the handles of the block....
Scared the living bleep out of me, getting the zap...but every since then, when I get tired, or am tempted to take a shortcut or hurry while doing electrical work, I think back to that feeling
and I stop work, or pay attention, or use special care. Heckuva way to learn to be careful, but maybe it's good it happened the way it did.