A transformer differential relay must match the transformer vector group, CT ratios, earthing method and required backup functions. Use this matrix to structure the selection discussion before requesting a quotation.
Record rated power, voltage ratio, vector group, CT ratios and CT connection. Confirm whether zero-sequence current should be measured and whether the low-side backup protection must cover the bus. The article on setting a transformer differential relay from nameplate data explains the calculation.
The transformer protection and control panel combines differential protection, backup protection, trip circuit supervision and optional monitoring. If the transformer is critical, review the transformer monitoring unit for temperature and cooling trends.
Read the protection coordination category and the article on coordinating feeder and transformer backup protection. The transformer protection relay range lists the available differential and backup devices.
