Trains at Sofia Central Station started running again at 5.35pm after power was restored to the overhead line, state railway company NRIC said.
Services stopped at 11.55am. A pantograph on a Passenger Transport locomotive broke after burning out, and the overhead line lost power.
NRIC set up a temporary system. Diesel shunting locomotives towed trains to nearby stations.
Four suburban trains were cancelled: No. 50283 and No. 50280 on the Sofia–Pernik line and back, and No. 10221 and No. 10224 on the Sofia–Kostenets line and back.