(Solved) GATE 2006 A generator is connected through a 20 MVA, 13.8/138 kV step down transformer, to transmission line. At the receiving end of the line a load is supplied through a step-down transformer of 10 MVA, 138/69 kV rating. A 0.72 pu load, evaluated on load side transformer ratings as base values, is supplied from the above system. For system base values of 10 MVA and 69 kV in load circuit, the value of the load (in per unit) in generator circuit will be

 Question :

A generator is connected through a 20 MVA, 13.8/138 kV step down transformer, to transmission line. At the receiving end of the line a load is supplied through a step-down transformer of 10 MVA, 138/69 kV rating. A 0.72 pu load, evaluated on load side transformer ratings as base values, is supplied from the above system. For system base values of 10 MVA and 69 kV in load circuit, the value of the load (in per unit) in generator circuit will be 

(a) 36 (b) 1.44 (c) 0.72 (d) 0.18 

[GATE E.E. 2006]

Answer :

Load = 0.72 pu at load side base of 10 MVA and 69 kv.

We have to find load in generating circuit.

So it is required to convert 0.72 pu to new generating side base of 20 MVA, 13.8 kV.

Z(new) = Z(old) * (KVA(new)/KVA(old)) * (kV(old)/kV(new))²

Z(new) = 0.72 * (20/10) * (69/13.8)²

Z(new) = 36 pu

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