Power Systems MCQs | Part 3 | Diploma in Electrical Engineering

This is Part 3 of 30 MCQs on Power Systems for the Diploma in Electrical Engineering. This set of 30 MCQs will test your knowledge. Each question focuses on different aspects of power systems. Use these questions to prepare for exams.

1. What is the value of the line voltage in a balanced three-phase star system with a phase voltage of 230V?

A. 230V B. 400V C. 460V D. 330V

2. Calculate the total power in a three-phase system with a line voltage of 415V and a line current of 20A, assuming a power factor of 0.8.

A. 11.52 kW B. 13.44 kW C. 19.32 kW D. 23.04 kW

3. What is the efficiency of a transformer with an input power of 500 kW and output power of 450 kW?

A. 85% B. 90% C. 92% D. 95%

4. A 3-phase, 4-pole induction motor runs at 1440 RPM. What is the slip of the motor if the supply frequency is 50 Hz?

A. 2% B. 3% C. 4% D. 6%

5. Calculate the short-circuit current for a system with a short-circuit MVA of 500 MVA and a system voltage of 220 kV.

A. 1.31 kA B. 2.27 kA C. 3.72 kA D. 4.55 kA

6. A generator supplies 200 MW at 0.9 power factor lagging. What is the reactive power supplied by the generator?

A. 97.3 MVAR B. 106.7 MVAR C. 123.5 MVAR D. 141.3 MVAR

7. What is the fault current if the fault impedance is 0.2 ohms and the system voltage is 11 kV?

A. 22.5 kA B. 27.5 kA C. 35 kA D. 55 kA

8. Calculate the synchronous speed of a 6-pole alternator connected to a 50 Hz supply.

A. 500 RPM B. 750 RPM C. 1000 RPM D. 1500 RPM

9. A transformer has a primary voltage of 10 kV and a secondary voltage of 400 V. If the primary current is 50 A, what is the secondary current assuming ideal conditions?

A. 1000 A B. 1250 A C. 1500 A D. 2000 A

10. Determine the load angle of a synchronous generator with a generated voltage of 11 kV, a terminal voltage of 10.5 kV, and a synchronous reactance of 1.5 ohms, supplying a current of 200 A.

A. 3.18 degrees B. 4.29 degrees C. 5.72 degrees D. 6.84 degrees

11. A transmission line has a resistance of 0.1 ohms and reactance of 0.2 ohms. Calculate the impedance of the line.

A. 0.22 ohms B. 0.25 ohms C. 0.28 ohms D. 0.31 ohms

12. What is the maximum power that can be transferred over a transmission line with a sending end voltage of 220 kV and a receiving end voltage of 210 kV, with a line impedance of 20 ohms?

A. 231 MW B. 242 MW C. 253 MW D. 264 MW

13. A synchronous motor operates at 0.8 power factor leading, supplying 100 kW of mechanical power. What is the reactive power supplied by the motor?

A. 60 kVAR B. 75 kVAR C. 80 kVAR D. 90 kVAR

14. Calculate the base impedance for a power system with a base power of 100 MVA and a base voltage of 220 kV.

A. 480 ohms B. 484 ohms C. 488 ohms D. 492 ohms

15. What is the critical clearing time in a power system stability analysis?

A. The maximum time to clear a fault without loss of system stability B. The minimum time to clear a fault without loss of system stability C. The average time to clear a fault with loss of system stability D. The average time to clear a fault without loss of system stability

16. What is the stability limit of a transmission line with a sending end voltage of 220 kV, a receiving end voltage of 210 kV, and a line reactance of 30 ohms?

A. 102.8 MW B. 104.3 MW C. 106.5 MW D. 108.7 MW

17. A power system operates with a base power of 200 MVA and base voltage of 400 kV. What is the base current?

A. 0.288 kA B. 0.312 kA C. 0.362 kA D. 0.413 kA

18. Calculate the reactance of a 50 MVA, 132 kV transmission line with a per-unit reactance of 0.2 pu.

A. 34.8 ohms B. 37.2 ohms C. 39.6 ohms D. 42.0 ohms

19. A power system has a fault current of 10 kA at a voltage of 11 kV. Calculate the fault MVA.

A. 110 MVA B. 120 MVA C. 130 MVA D. 140 MVA

20. Determine the admittance of a transmission line with a conductance of 0.01 S and a susceptance of 0.02 S.

A. 0.022 S B. 0.024 S C. 0.028 S D. 0.031 S

21. A synchronous motor draws 500 kW at 0.9 power factor lagging. What is the apparent power?

A. 550 kVA B. 600 kVA C. 650 kVA D. 700 kVA

22. A 3-phase motor consumes 100 kW of power with an efficiency of 90%. Calculate the input power.

A. 105 kW B. 110 kW C. 115 kW D. 120 kW

23. What is the critical clearing angle in transient stability analysis?

A. The angle at which the fault must be cleared to maintain stability B. The angle at which the system becomes unstable C. The angle at which the power system oscillates D. The angle at which the voltage collapses

24. A generator delivers 250 MW at a power factor of 0.85 lagging. What is the generator’s apparent power?

A. 280 MVA B. 294 MVA C. 312 MVA D. 325 MVA

25. Calculate the current in a 132 kV transmission line delivering 100 MW at 0.9 power factor.

A. 436.5 A B. 487.6 A C. 524.3 A D. 548.2 A

26. A power system has a generation capacity of 1500 MW and a peak load of 1200 MW. What is the reserve margin?

A. 20% B. 25% C. 30% D. 35%

27. Calculate the energy loss in a 10 km transmission line with a resistance of 0.5 ohms and current of 200 A.

A. 100 kWh B. 200 kWh C. 300 kWh D. 400 kWh

28. A transformer has a turns ratio of 20:1. What is the secondary voltage if the primary voltage is 11 kV?

A. 500 V B. 550 V C. 600 V D. 650 V

29. Determine the voltage regulation of a transformer with no-load voltage of 230 V and full-load voltage of 220 V.

A. 4.35% B. 4.55% C. 4.75% D. 4.95%

30. A power system operates with a base power of 150 MVA and a base voltage of 330 kV. What is the base impedance?

A. 720 ohms B. 725 ohms C. 730 ohms D. 735 ohms

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The Bottom Line

Thank you for going through Part 3 of MCQs on Power Systems for the Diploma in Electrical Engineering”. Review the questions regularly. Stay updated with power system concepts. Keep practicing and learning.

30 MCQs on Power Systems (Part 3) | Diploma in Electrical Engineering