how to make vector group test of transformer?

To conduct a vector group test on a transformer, first, ensure the transformer is de-energized and safely isolated. Connect the primary and secondary windings to a suitable test set-up, typically using a three-phase supply. Measure the phase angles between the primary and secondary voltages using a phase angle meter. The results will indicate the vector group, which describes the phase relationship and connection type (e.g., Yd11, Dd0). Document the findings for analysis.