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GATE 2023 Power Systems Quiz 39

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Question 1

The Primary and Secondary impedance of a 50 MVA, 22/11 KV Transformer  is 0.019+0.0275j p.u. each. What is the Primary and Secondary impedances of the transformer respectively(in ohms)?

Question 2

Two alternators each rated for 11 KV, 100 MVA are connected in parallel with each having 0.2 p.u. impedance. These two alternators are replaced by a single alternator with rating of 300 MVA, 11kV. What will be the new p.u. impedance____________ (Upto two decimal)

Question 3

Which of the following is the standard followed by American National Standards Institute(ANSI) for manufacture of transformers?

Question 4

A power system is represented by a single line diagram which is shown below

The Ratings of the system is as follows
Generator rating
 = 40 MVA, 25 KV, XG = 0.2 p.u

Transformer T1 Rating = 33/220 KV.

What will be the p.u reactance of generator near to transformer 1 to a base of 100 MVA, 33KV ?

Question 5

A 3-phase, 4-wire Balanced system (ABC sequence) supplies power to a Balanced star-connected load. The magnitude of the current in each phase is 15 A. What will be the  current in the neutral wire?

Question 6

A Single phase a.c system supplies a load of 400 KW and if this system is converted to 3-phase, 3-wire a.c system by running a third similar conductor . What will be the three phase load that can now be supplied if the voltage between the conductors is the  same ?

(Assume the power factor and transmission efficiency is to be same in two cases)

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