The ABB RET670 is a highly advanced and versatile protection relay, designed as an integral part of ABB’s Relion® protection and control product family. Its primary function is to safeguard transformers and other critical power system equipment from an array of faults and abnormal operating conditions.

This relay offers comprehensive protection for transformers in various power system applications. It can be used for two – winding transformers (both single and multi – breaker arrangements), three – winding transformers (similarly in single and multi – breaker setups), autotransformers, shunt reactors, and generator – transformer units.

The RET670 is equipped with a range of sophisticated protection functions. Its differential protection feature is highly sensitive to low – level internal faults. To prevent false tripping during magnetizing inrush and overexcitation scenarios, it incorporates 2nd and 5th harmonic restraint. Earth – fault protection is also a key function, offering both low and high impedance protection against winding earth faults. Distance protection serves as backup protection for phase – to – phase and phase – to – earth faults. Additionally, it has configurable overcurrent and thermal overload protection with multiple time constants, which can be adjusted according to the specific requirements of the transformer and the power system. Breaker failure protection ensures a quick response in case of breaker failure, rapidly tripping the surrounding breakers to isolate the