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Seq. Imp. of balanced Y-load: Vag = ZYIa + Zn In = ZYIa+ Zn(Ia + Ib + Ic) Vag =(Zy+Zn)Ia + ZnIb +ZnIc Similarly, Vbg =ZnIa + (Zy+Zn)Ib +ZnIc Vcg =ZnIa + ZnIb +(Zy+Zn)Ic. In matrix form, V ph = Z ph I ph In terms of sym components,.
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Seq. Imp. of balanced Y-load: Vag = ZYIa + Zn In = ZYIa+ Zn(Ia + Ib + Ic) Vag =(Zy+Zn)Ia + ZnIb +ZnIc Similarly, Vbg =ZnIa + (Zy+Zn)Ib +ZnIc Vcg =ZnIa + ZnIb +(Zy+Zn)Ic
In matrix form, Vph = Zph Iph In terms of sym components,
Vph = Zph Iph A Vs = Zph A Is Vs = A-1 Zph A Is Vs = Zs Is where Zs = A-1 Zph A
Simplifying; A-1 Zph A or where Z0 = ZY+3Zn Z1 = ZY Z2 = ZY
If neutral is grounded through Zn Z0 = ZY + 3 Zn If neutral is solidly grounded, i.e., Zn = 0Z0 = ZY If neutral is not grounded, i.e., Zn = ∞Z0 = ZY+ ∞ = ∞ i.e., open circuit Thus zero-sequence currents cannot flow if neutral to ground connection is absent
Sequence Impedance of balanced Δ-load Convert Δto Y: ZY = ZΔ/3 The delta connected load is converted into non grounded Y connected load Therefore, Zn = ∞ Z0 = ZΔ/3+3Zn Z0 = ∞ Z1 = ZY = ZΔ/3 Z2 = ZY = ZΔ/3