Transformer nameplates carry a vector group reference such at Yy0, Yd1, Dyn11 etc. This relatively simple nomenclature provides important information about the way in which three phase windings are connected and any phase displacement that occurs.
Digit 0 means that the LV
phasor is in phase with the HV phasor
All references are taken from phase-to-neutral and assume a counter-clockwise phase rotation. The neutral point may be real (as in a star connection) or imaginary (as in a delta connection)
When transformers are operated in parallel it is important that any phase shift is the same through each. Paralleling typically occurs when transformers are located at one site and connected to a common busbar (banked) or located at different sites with the secondary terminals connected via distribution or transmission circuits consisting of cables and overhead lines
When 3 coils are used in a 3 phase transformer winding a number of options exist. The coil voltages can be in phase or displaced as above with the coils connected in star or delta and, in the case of a star winding, have the star point (neutral) brought out to an external terminal or not.
Example - Dyn11
We hope you found this tutorial useful, your comments are welcome. Contact Us