EMPLYEE HEARD ON PLANT RADIO THAT THE PLANT AIR COMPRESSOR WENT DOWN AFTER STARTING #1 FINISH MILL SYSTEM. HE WENT DIRECTLY TO THE COMPRESSOR STARTER. SHIFT UTILITY MAN TRIED STARTING THE COMPRESSOR. AN ELECTRICAL EXPLOSION OCCURRED IN THE STARTER BREAKER PANEL RESULTING IN FLASH BURNS TO EMPLOYEE'S LEFT SIDE, 1 DEGREE TO LEFT SIDE, 2ND AND 3RD DEGREE TO ARM.