SHOVEL OPERATOR REPORTED LOUD NOISE IN SHOVEL HOUSE & HAD MAIN TRANSFORMER FAULT. HE THEN SAW SMOKE COMING OUT OF THE HOUSE & GOT OFF SHOVEL. POWER WAS KILLED. 2 EMERG. RESPONSE PERSONS -FIRE WATCH 1 HR. INVESTIGATION DET. A BROKEN STRUCTURE IN 1ST STEP RCP CABINET, EXCESSIVE MOVEMENT OF REACTORS CAUSED SHUNT INSULATION TO WEAR THROUGH, CAUSING SHORT CIRCUIT.