Arrangement for preventing slag from penetrating into a continuous casting mould during continuous casting

During the continuous casting process, metal melt flows from a reservoir covered with a slag layer into a tundish covered with a slag layer, and from there into a mould. In order to prevent a damage to the strand or the continuous casting plant on account of the slag entry into the mould and the jeopardization of the operating personnel, the height of the metal-melt-bath level on the one hand and the height of the slag-bath level on the other hand are continuously determined. From the relation of these values the slag amount present in the tundish is determined.