ABB RET670 1MRK004816-CB Transformer Protection RelayDescription The ABB RET670 (1MRK004816 CB) is a high end transformer protection and control relay from the Relion series. It is engineered for complex high voltage applications requiring differential protection, breaker control, and advanced monitoring. Specifications Product Type: Transformer Protection Relay Part Number: 1MRK004816 CB Series: Relion RET670 Protection Scope: 3 winding transformer with single breaker configuration Communication