The transformer's vector group is a combination of letters and numbers that represents the winding configuration of the transformer. These letters and numbers indicate the number of primary and secondary winding phases, the winding connections, and the phase displacement between the primary and secondary windings. The vector group is typically expressed in letters, such as Yyn{{0}}, Dyn11, or Z1y0.

Represented by number(0 to 11), each indicating a 30-degree phase shift, between primary and secondary windings. 

The IEC 60076-1 international standard defines vector group notation, testing procedures, and allowable phase displacements for power transformers worldwide. Wuhan Huayi electric power technology is making the transformer turn ratio tester(TTR meter), it can test transformer Vector group automatically.