(SEM V) THEORY EXAMINATION 2024-25 POWER SYSTEM-I

Subject Code: BEE501

Subject Name: Power System–I

Exam Type: Theory

Semester: V (B.Tech)

Maximum Marks: 70

Time: 3 Hours

Exam Year: 2024–25

Sections: A, B, and C
 

SECTION A – Short Answer Questions (2 × 7 = 14 Marks)

Attempt all questions in brief.

Describe renewable and non-renewable energy resources.

Define:
(i) Demand Factor          (ii) Diversity Factor.

Explain the single line diagram in a power system.

Define per unit system and explain its significance.

Describe factors affecting sag in overhead transmission lines.

What do you mean by self GMD and mutual GMD?

Explain insulation and list types of insulating materials.
 

SECTION B – Medium-Length Questions (7 × 3 = 21 Marks)

Attempt any three of the following:

Explain the basic structure of a smart grid and the importance of IT in power systems.

What are corona effects? Explain factors affecting corona loss and how it can be reduced.

A 3-phase overhead line has 4 suspension insulators per string; given voltages across the second and third units are 14.2 kV and 20 kV.
→ Find total voltage across the string and its string efficiency.

Derive the capacitance of a symmetrical three-phase line.

Draw and explain the layout of oil-filled cables.
 

SECTION C – Long / Analytical Questions (7 × 5 = 35 Marks)

Attempt one part from each question.

Q3. Power Plant Performance

a. For a plant with max load = 500 MW, min load = 400 MW, and capacity = 750 MW, find:

Plant capacity factor                            Load factor                      Utilization factor

Reserve capacity.
b. Draw and explain the block diagram of a thermal power plant.

Q4. Transmission Systems

a. Compare the volume of conductor material required for a DC 3-wire system and 3-phase, 3-wire system assuming equal potential difference.
b. Sketch and explain the T and π models of a medium transmission line, with parameters.

Q5. Sag and Insulation

a. Explain methods to calculate sag and tension in overhead transmission lines over uneven ground levels.
b. What are insulators? Describe types and applications with neat diagrams.

Q6. Inductance of Transmission Lines

a. A 3-phase, 50 Hz line has conductor diameter = 21 mm, spacing A-B = 3 m, B-C = 5 m, and C-A = 3.6 m.
→ Find inductance and inductive reactance per phase per km.
b. Derive the expression for inductance of a symmetrical 3-phase line, explain equivalent spacing and its significance.

Q7. Underground Cables

a. Explain in detail the grading of overhead cables.
b. Determine the overall and most economical diameter of a single-core 3-phase, 275 kV cable, if max permissible stress = 15 kV/mm.
 

Key Topics to Focus On

Power system layout and components                              Smart grid and IT integration

Corona loss: causes, reduction, and effects                       Transmission line parameters (R, L, C)

Per-unit system and single-line diagrams                          Inductance, capacitance, and sag calculations

Types and functions of insulators                                       Underground and oil-filled cables

Power plant performance factors (capacity, load, utilization)

Preparation Tips

Understand core concepts: per unit system, GMD, GMR, and transmission parameters.

Practice numericals: sag, inductance, and efficiency-based questions.

Draw clear diagrams: single-line diagrams, T and π models, thermal plant layout.

Memorize formulas for capacitance, inductance, and performance ratios.

Revise real-world applications — smart grids, corona effects, cable design.