EE IS A PLANT OPERATOR. HE WAS HAVING PROBLEMS WITH A MILL OPERATED BY A 40 HP 480V ELECTRIC MOTOR. HE ATTEMPTED TO TURN THE MOTOR OFF WITH THE SAFETY KNIFE DISCONNECT LOCATED AT THE MOTOR IN STEAD OF USING ON/OFF SWITCH IN THE CONTROL ROOM 50'AWAY. HE APPARENTLY DISENGAGED THE KNIFE SWITCH SLOWLY RESULTING IN AN ELECTRIC ARC WHICH BLEW OUT AN INSTALLED AMP METER IN THE DOOR.