2 EMPLOYEES RECEIVED BURN INJURIES TO THEIR PERSONS WHEN A SUBSTATION EXPLODED. THE CONTRIBUTING FACTORS WERE THE ELECTRICIAN FORGOT TO REMOVE THE GROUND STRAPS FROM AN AIR SWITCH & A PHASE CONDITION OCCURRED WHEN THE OIL CIRCUIT BREAKER WAS CLOSED. THE OCB OPENED BUT FAILED TO EXTINGUSH THE ARC ON TWO PHASES WHICH CAUSED AN EXPLOSION.