MAINTENANCE CREW HAD REPLACED A 480 VOLT TRANSFORMER AND ELECTRICIAN WAS RE-ENERGIZING THE SECOND BANK OF TRANSFORMERS ON A 3 PHASE 480 V SYSTEM AT THE SAME TIME MAINTENANCE CREW LEADMAN (VICTIM) WAS TESTING THE FIRST 3 PHASE 480 V BANK OF TRANSFORMERS. TRANSFORMER BANKS WERE ISOLATED CIRCUITS. UNEXPECTED SHORT IN METER CAUSED AN ELECTRICAL ARC CAUSING BURNS TO HAND.