1
GATE EE 2014 Set 1
+2
-0.6
In an unbalanced three phase system phase current $${{\rm I}_a} = 1\angle \left( { - {{90}^0}} \right)\,\,pu,\,\,$$ negative sequence current $$\,{{\rm I}_{b2}} = 4\angle \left( { - {{150}^0}} \right)\,\,pu,\,\,$$ zero sequence current $$\,\,{{\rm I}_{c0}} = 3\angle {90^0}\,\,pu.\,\,\,$$ The magnitude of phase current $${{\rm I}_b}$$ in $$pu is A$$1.00$$B$$7.81$$C$$11.53$$D$$13.00$$2 GATE EE 2010 MCQ (Single Correct Answer) +2 -0.6 The zero-sequence circuit of the three phase transformer shown in the figure is A B C D 3 GATE EE 2008 MCQ (Single Correct Answer) +2 -0.6 Given that:$$\,{V_{s1}} = {V_{s2}} = 1 + j0\,\,p.u,\,\, + ve\,\,$$sequence impedance are$$\,{Z_{s1}} = {Z_{s2}} = 0.001 + j0.01\,\,p.u\,\,$$and$${Z_L} = 0.006 + j\,0.06\,\,p.u,\,\,3\phi .\,\,\,$$Base$$MVA=100,$$voltage base$$=400kV(L-L).$$Nominal system frequency$$= 50Hz.$$The reference voltage for phase$$'a'$$is defined as$$\,\,V\left( t \right) = {V_m}\,\cos \left( {\omega t} \right).\,\,\,$$A symmetrical$$3\phi $$fault occurs at centre of the line, i.e., at point$$'F'$$at time 'to' the$$+ve$$sequence impedance from source$${S_1}$$to point$$'F'$$equals$$(0.004 + j \,\,0.04)p.u.$$The wave form corresponding to phase$$'a'$$fault current from bus$$X$$reveals that decaying$$d.c.$$offset current is$$-ve$$and in magnitude at its maximum initial value. Assume that the negative sequence are equal to$$+ve$$sequence impedances and the zero sequence$$(Z)$$are$$3$$times$$+ve$$sequence$$(Z).$$The instant$$\,\left( {{t_0}} \right)\,\,$$of the fault will be A$$4.682ms$$B$$9.667ms$$C$$14.667ms$$D$$19.667ms$$4 GATE EE 2008 MCQ (Single Correct Answer) +2 -0.6 Given that:$$\,{V_{s1}} = {V_{s2}} = 1 + j0\,\,p.u,\,\, + ve\,\,$$sequence impedance are$$\,{Z_{s1}} = {Z_{s2}} = 0.001 + j0.01\,\,p.u\,\,$$and$${Z_L} = 0.006 + j\,0.06\,\,p.u,\,\,3\phi .\,\,\,$$Base$$MVA=100,$$voltage base$$=400kV(L-L).$$Nominal system frequency$$= 50Hz.$$The reference voltage for phase$$'a'$$is defined as$$\,\,V\left( t \right) = {V_m}\,\cos \left( {\omega t} \right).\,\,\,$$A symmetrical$$3\phi $$fault occurs at centre of the line, i.e., at point$$'F'$$at time 'to' the$$+ve$$sequence impedance from source$${S_1}$$to point$$'F'$$equals$$(0.004 + j \,\,0.04)p.u.$$The wave form corresponding to phase$$'a'$$fault current from bus$$X$$reveals that decaying$$d.c.$$offset current is$$-ve$$and in magnitude at its maximum initial value. Assume that the negative sequence are equal to$$+ve$$sequence impedances and the zero sequence$$(Z)$$are$$3$$times$$+ve$$sequence$$(Z).$$The$$rms$$value of the ac component of fault current$$\,\left( {{{\rm I}_x}} \right)$$will be A$$3.59kA$$B$$5.07kA$$C$$7.18kA$$D$$10.15kA
EXAM MAP
Medical
NEET