The SIPROTEC 7UT63 and 7UT635 differential protection relays are used for fast and selective fault clearing of short-circuits in transformers of all voltage levels and also in rotating electric machines like motors and generators, for short lines and busbars. The protection relay can be parameterized for use with threephase and single-phase transformers. The specific application can be chosen by parameterization. In this way an optimal adaptation of the relay to the protected object can be achieved.