Definition: Arc Tangent of Voltage Unbalance factor (Ratio between Negative Sequence Voltage and Positive Sequence Voltage) Estimation of TAU 1. Using Two Voltages and Phase Angle Differences Let the two voltages are Vab, Vbc and Phase angle between these two voltages in Positive Sequence direction δ, Then the voltage unbalance factor will be determined as follows. 2. Using Phase Angle Differences Let the three phase angle differences are δ 1 , δ 2 and δ 3 3. Using three Voltage magnitudes Let the Three Line voltages are Vab, Vbc and Vca Then we determine, Where, the factor β is referred as Voltage Biquadrate (VBR) In section 3, the magnitudes are always positive and angle independent, so the value of TAU is obtained from 0 0 to 45 0 .
Professor/EEE, GCE, Bargur, TamilNadu, India