Setting Phase shift Action
Yy6 180 lag Invert currents
Yd7 150 lead Yd1 and Invert
Yy8 120 lead
Ia = IC
Ib = IA
Ic = IB
Yd9 90 lead Yd3 and Invert
Yy10 60 lead
Ia = -IB
Ib = -IC
Ic = -IA
Yd11 30 lead
Ia = (IA - IB) / √3
Ib = (IB - IC) / √3
Ic = (IC - IA) / √3
Ydy0 0
Ia = IA - (IA + IB + IC) / 3
Ib = IB - (IA + IB + IC) / 3
Ic = IC - (IA + IB + IC) / 3
Ydy6 180 lag Ydy0 and Invert
Where Ia, Ib, Ic are the uncorrected values and IA, IB, IC are the corrected values.
Note:
You must set Compensation to Transformer before the Vectorial Comp setting becomes visible.
10.2
ZERO SEQUENCE FILTERING
In addition to compensating for the phase shift of the protected transformer, it is also necessary to mimic the
distribution of primary zero sequence current in the protection scheme. The figure below shows the need for zero
sequence current filtering for differential protection across a transformer. The power transformer delta winding
acts as a ‘trap’ to zero sequence current. This current is only seen on the star connection side of the transformer
and therefore as differential current.
P543i/P545i Chapter 6 - Current Differential Protection
P54x1i-TM-EN-1 115
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