1.Wiring Method Of Transformer：

There are two types of common transformer windings, namely "triangle wiring" and "star wiring"; In the connection group of the transformer, "D" is represented by a triangle, "Yn" is a star with a neutral wire, Y is a star, and n is a neutral wire. 

The combination of the two windings of the transformer forms four types of wiring groups: "Y,y,"D,y", "Y,d" and "D,d". In China, only "Y,y" and "Y,d" are used. Since there are two kinds of Y connections, with and without neutral lines, without neutral lines, no symbols are added, and with neutral lines, the letters Y are added after the letter N. n indicates that the neutral point has a pinout.

2. Representation of the connection group of the transformer

The uppercase letter indicates the wiring mode of the primary side (or primary side), and the lowercase letter indicates the wiring mode of the secondary side (or secondary side). Y (or y) is the star wire, and D (or d) is the triangle wire. The number
adopts the clock notation method, which is used to represent the phase relationship of the primary and secondary side voltages, the primary side voltage phasor is used as the minute hand, the fixed finger is at the position of 12 o'clock in the clock, and the line voltage phasor of the secondary side is used as the hour hand.

In “Dyn11”, 11 indicates that the line voltage Uab on the secondary side of the transformer lags behind the primary side voltage UAB by 330 degrees (or 30 degrees ahead).