PHASE DISPLACEMENT CONCEPT OF TRANSFORMER

Phase displacement is the angular difference between the vectors representing the voltages induced between the higher voltage and lower voltage terminals having the same making letter, and the corresponding respective neutral points(real or imaginary).
       A convention adopted internationally to indicate phase displacement is to use a figure which represents the hour indicated by a clock when the minutes hand takes the place of line to neutral voltage vector for the higher voltage winding and is set at 12 O'Clock and when the four hand represents line to neutral voltage vector for the lower voltage winding.

LONG HAND-MINUTE HAND
               Referance Voltage Vector-HV Handle

SHORT HAND-HOUR HAND
                Represents -LV vector

1.Phase displacement -30 degree (1 O'Clock position)
2.Phase displacement +30 degree (11 O'Clock Position)
3.phase displacement 0 degree (12  O'Clock Position)
4.phase displacement +180 , -180 degree (6 O ' Clock position)

NOTE: If follows that the clock hour number (except for zero displacement) is obtained by dividing the phase displacement angle in degrees by 30.