How do you find angular displacement of transformer?

Angular displacement (sometimes called phase displacement) applies to three-phase Transformers, whether a single three-phase transformer, or three single-phase transformers connected as three phase transformer bank. It is, to a three-phase transformer what additive/subtractive polarities are to a single-phase transformer.

Angular displacement is one of a number of conditions that must be the same before two three-phase transformers (or transformer banks) are paralleled.

'Angular displacement' is the angle by which the secondary line-to-line voltage lags the primary line-to-line voltage.

Angular displacements for common connections are as follows:

• delta/delta transformers have an angular displacement of 0o or 180o
• wye/wye transformers have an angular displacement of 0o or 180o
• delta/wye transformers have an angular displacement of 30o or 210o
• wye/delta transformers have an angular displacement of 30o or 210o

So, for example, it is impossible to parallel a delta/delta or wye/wye transformer with a delta/wye or wye/delta transformer, as their angular displacements are different.

Determining the angular displacement of a particular transformer configuration (wye-delta, etc.) can be done by drawing the phasor diagram for the complete transformer as follows:

1. draw the primary phase voltages
2. draw the primary line voltages
3. draw the secondary phase voltages
4. draw the secondary line voltages
5. measure the (angular displacement) between a secondary line voltage and its corresponding primary line voltage