RET670 – Reliable Protection and Control for All Types of Power Transformers and Reactors

RET670 – Reliable Protection and Control for All Types of Power Transformers and Reactors 

The extremely fast differential protection of the RET670 is the ideal solution even for the most demanding applications.The differential protection of the RET670/650 with adaptive compensation of the transformer taps significantly increases the sensitivity of the device. The RET670/650 covers transformer turn-to-turn faults, including minor internal faults, and the unique fault criterion for faults in and out of negative sequence current zones is more sensitive than conventional steady-state transformer differential protection, thus providing extremely sensitive protection against transforming internal faults, and tripping severe faults that can cause serious equipment damage before they occur. The RET670/650 has very low requirements for the main CT and does not require an auxiliary CT.

The low impedance limiting earthing protection provides extremely stable protection against external faults for all windings earthed directly or via a small resistance. The additional directional zero-sequence current criterion of this function further increases safety.

The directional or non-directional overcurrent protection enables the necessary back-up protection and, in combination with the fast and sensitive limiting low-impedance earthing protection (sensitivity up to 1% of the winding turns), provides comprehensive protection for power transformers. Thermal overload protection prevents transformer damage due to overload. Circuit breaker failure protection enables fast back-up tripping of adjacent circuit breakers and retriggering of the present breaker, e.g. to prevent misoperation during testing.