Abstract: An arc electrode assembly comprises a water-cooled metal shaft and a consumable active portion, being interconnected by means of a screw nipple. The metal shaft is surrounded below its clamping area by a protective jacket being detachably arranged about the metal shaft. Between the jacket and the metal shaft a layer of electrically insulating refractory material is arranged which is cooled by the cooling system of the jacket. The protective jacket comprises at least one steel tube which is provided for the passage of a cooling medium. The steel pipe(s) may additionally be surrounded by refractory or slag material or may directly be embedded into such material.