(SEM V) THEORY EXAMINATION 2022-23 POWER SYSTEM-I

Course: B.Tech (Semester V)

Subject: Power System – I

Subject Code: KEE-501

Duration: 3 Hours

Total Marks: 100

Instructions: Attempt all sections. Assume missing data suitably.

Section A – Short Answer Questions (2 × 10 = 20 Marks)

Answer all questions briefly:
 

List key features of primary and secondary distribution systems in a power system.

Explain diversity factor in power systems.

What will be the effect of line capacitance for lagging load in a medium transmission line?

Why is the line capacitance neglected in short transmission lines?

Explain the effect on sag of a transmission line if the tower height increases.

Explain the factors affecting sag of an overhead transmission line.

Classify various types of supports used in power transmission lines.

Describe uses and advantages of bundled conductors.

Why is a metallic sheath provided in underground cables?

List the different types of insulating materials used in underground cables.

Section B – Descriptive Questions (10 × 3 = 30 Marks)

Attempt any three:

A plant has daily energy production and plant factor of 1296 MWh and 50%, respectively. Calculate the maximum rating of the power plant.

Write short notes on the factors affecting Corona losses.

Show that string efficiency of a string of suspension insulators depends on the number of discs in the string.

Show mathematically that the inductance of a bundled conductor line is less than that of a line with one conductor per phase.

Compare overhead lines and underground cables.

Section C – Long Answer / Analytical Questions (10 × 5 = 50 Marks)

Q3.
(a) Explain the nuclear reaction theory and working principle of a nuclear power station with plant layout.
or
(b) A hydroelectric power station has a reservoir area of 2.4 km² and capacity 5×10⁶ m³. The effective head is 100 m; efficiencies of penstock, turbine, and generator are 95%, 90%, and 85%.

(i) Calculate the total electrical energy that can be generated.

(ii) If a load of 15,000 kW has been supplied for 3 hours, find the fall in reservoir level.

Q4.
(a) An overhead transmission line operates at 220 kV between phases at 50 Hz, with conductors arranged in a 5 m delta formation. Find the maximum conductor diameter for no corona loss under fair weather (air density factor = 0.95, irregularity factor = 0.85, critical voltage = 230 kV). Also, find power loss under stormy weather.
or
(b) Derive expressions for voltage regulation and efficiency for a short transmission line.

Q5.
(a) Explain the calculation procedure of maximum sag of a transmission line at equal supports, including wind pressure loading.
or
(b) An overhead line has:                                                    Span length = 160 m

Conductor diameter = 0.95 cm                                          Weight per unit length = 0.65 kg/m

Ultimate stress = 4250 kg/cm²                                           Wind pressure = 40 kg/m² of projected area

Factor of safety = 5                                                             Calculate the sag.

Q6.
(a) Derive the capacitance per unit length of a 3-phase line completely transposed.
or
(b) Describe the inductance calculation for a three-phase double-circuit line with symmetrical (hexagonal) spacing.

Q7.
(a) Explain the grading method of underground cables with mathematical expressions.
or
(b) Explain, with a neat sketch, the construction of a 3-core belted-type cable.