GATE EE Power Systems PYQs & Answers

Questions 1–10 of 64. Imported answers require independent review unless marked reviewed.

Consider a power system with

buses, of which

are generator buses and the remaining

are load buses (where there is no generation).

Assume that there are no reactive power-limit violations at the generator buses.

What is the size of the Jacobian matrix in the Newton-Raphson load flow method?

Your answerChoose one option.

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The initial three-phase voltage phasors (

, and

) at a bus of a power network are as shown in Case-1. Due to a disturbance, the bus voltage phasors changed in phase by a small angle

, and the magnitudes remained the same as depicted in Case-2.

Diagram for Electrical Engineering question 19

Which one of the following statements is correct about the zero sequence components?

Your answerChoose one option.

The zero sequence components in Case-1 and Case-2 have the same phase angle and magnitude

The magnitude of the zero sequence component in Case-1 is greater than that in Case-2

The magnitude of the zero sequence component in Case-2 is greater than that in Case-1

The zero sequence components in Case-1 and Case-2 have the same magnitude but different phase angles

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In the circuit shown, the phase currents are

Diagram for Electrical Engineering question 39

Given that the CTs are ideal with no saturation, and the turns ratio of the Main CT is 300:5 and that of the Auxiliary Transformer (YₙΔ) is 2:1 on every phase, the value of

, rounded off to three decimal places, is:

Your answerChoose one option.

0 A

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The operating characteristic of a reactance relay is given by

, where

is the reactance calculated by the relay. Its operating characteristic in the admittance plane (G-B plane, where G and B denote conductance and susceptance, respectively, expressed in

) is given by:

Your answerChoose one option.

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A three-phase two-winding transformer has a voltage transformation ratio

, where

is the primary side voltage in p.u., and

is the secondary side voltage in p.u.

and

represent the currents injected into the primary and secondary sides of the transformer, respectively. The admittance corresponding to the leakage impedance of the transformer referred to the secondary is

p.u. Neglect the magnetizing branch.

Diagram for Electrical Engineering question 41

The Y bus representation of this transformer is:

Your answerChoose one option.

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For the balanced 3-phase transmission line shown, consider the following cases:

Case-1:

and

Case-2:

and

Diagram for Electrical Engineering question 54

Which of the following statements is/are correct about real power loss and reactive power loss in the line?

Your answerSelect all correct options. You can choose more than one.

Real power loss in Case-1 is more than that in Case-2

Real power loss in Case-2 is more than that in Case-1

Reactive power loss in Case-1 is more than that in Case-2

Reactive power loss in Case-2 is more than that in Case-1

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A system with two generators G1 and G2 (without generator limits) is shown.

Diagram for Electrical Engineering question 58

The total load on the system is 1184 MW. The expressions for the cost of generation (C₁ and C₂) and real power loss (Pₗₒₛ) are as follows:

C₁(P_G₁) = 1000 + 50P_G₁ + 0.01(P_G₁)² Rs/MWh

C₂(P_G₂) = 2000 + 50P_G₂ + 0.001(P_G₂)² Rs/MWh

Pₗₒₛ = 0.001(P_G₂ − 50)² MW

When the generators are operating at their optimal generation, meeting the total load requirement, the real power loss in the system is ______ MW (Round off to one decimal place)

Consider the Lagrange multiplier λ = 70.25 for optimal generation.

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During a power failure, a domestic household uninterruptible power supply (UPS) supplies AC power to a limited number of lights and fans in various rooms. As per a Newton-Raphson load-flow formulation, the UPS would be represented as a

Your answerChoose one option.

Slack bus

PV bus

PQ bus

PQV bus

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Consider a distribution feeder, with

ratio of 5. At the receiving end, a 350 kVA load is connected. The maximum voltage drop will occur from the sending end to the receiving end, when the power factor of the load is __________ (round off to three decimal places).

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The bus impedance matrix of a 3-bus system (in pu) is

. A symmetrical fault (through a fault impedance of

pu) occurs at bus 2. Neglecting pre-fault loading conditions, the voltage at bus 1, during the fault is ______ pu (round off to three decimal places).

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GATE EE Power Systems PYQs

How to practice Power Systems

Question 18

Question 19

Question 39

Question 40

Question 41

Question 54

Question 58

Question 24

Question 32

Question 33