The SIPROTEC 7UT612 differential protection relay is 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 three-phase and single-phase transformers.The specific application can be chosen by parameterization. In this way, an optimal adaption of the relay to the protected object can be achieved.In addition to the differential function, a backup overcurrent protection for 1 winding/star point is integrated into the relay. Optionally, a low or high-impedance restricted earth fault protection, a negative sequence protection, and a breaker failure protection can be used. With external temperature monitoring boxes (thermo-boxes) temperatures can be measured and monitored in the relay.Therefore, complete thermal monitoring of a transformer is possible, e.g. hot-spot calculation of the oil temperature. The relays provide easy-to-use local control and automation functions. The integrated programmable logic (CFC) allows the users to implement their own functions, e.g. for the automation of switchgear (interlocking). User-defined messages can be generated as well.The flexible communication interfaces are open for modem communication architectures with the control system. The protection relay can be parameterized for use with three-phase and single-phase transformers. In addition to this, a thermal replica is integrated for the supervision of the ohmic losses in the plant.