Power System Engineering-II SPPU Endsem Question Paper Nov 2025

Questions

1. Q1

   1. a)

      i) The load impedance is (20+j30) Ohm. If the base power is 100MVA and voltage base 11kV. What is the per unit load impedance. ii) The per unit impedance of a 100MVA, 220kV/132kV transformer is (0.1 + j 0.2) Pu referred to primary. What is the per unit impedance referred to secondary? [2] iii) The per unit reactance of a 50MVA, 10kV alternator is 10%. What is the per unit reactance of the alternator on 100MVA, 20kV Base. [2] iv) A transmission has resistance and reactance of 0.1 Ohm/km and 0.5 Ohm/km respectively. The length of line is 100km. What is the per unit impedance of the line to the base of 100MVA, 20kV. [2]

      [2]
   2. b)

      Give the details classification of buses with known and unknown variables. Also explain the significance of each type of bus.

      [8]
   OR

2. Q2

   1. a)

      This part has equations that don’t show as text. Open the PDF to read it.

      [8]
   2. b)

      What do you mean by per units system in power system? How the per unit values are calculated in power system? What are the advantages and disadvantages of per unit system?

      [8]

3. Q3

   1. Let all phases of an alternator is short circuited at its terminal :

      Also asked:May 2025

   2. a)

      Draw the waveform of fault current showing sub transient, transient and steady state period.

      Also asked:May 2025

      [3]
   3. b)

      From above diagram comment on time period sub transient, transient and steady state period.

      Also asked:May 2025

      [3]
   4. c)

      Draw the reactance diagram and write its formula for sub transient, transient and steady state period.

      Also asked:May 2025

      [6]
   5. d)

      If the damper winding reactance is j0.1 pu, field winding reactance is j0.2 pu, armature reactance is j0.3pu and leakage reactance is j0.5pu. Calculate sub- transient, transient and steady state reactance.

      Also asked:May 2025

      [3]
   6. e)

      Justify that the fault current under sub transient period is more that transient and steady state period.

      Also asked:May 2025

      [3]
   OR

4. Q4

   1. a)

      What is the use of current limiting reactor? What are its types based on location and based on construction? Explain any one type with diagram merits and de-merits.

      [8]
   2. b)

      This part has equations that don’t show as text. Open the PDF to read it.

      [10]

5. Q5

   1. a)

      Derive the equation of fault current in case of LG fault.

      Also asked:May 2025 ·Nov 2024 ·May 2024 ·May 2023

      [9]
   2. b)

      This part has equations that don’t show as text. Open the PDF to read it.

      [3]
   OR

6. Q6

   1. a)

      Draw the zero sequence impedance diagram for following connections of transformer i) Delta-Star ii) Delta-Star with solid ground [3] iii) Delta-star with neutral impedance [3]

      Also asked:May 2025 ·Nov 2023 ·May 2023

      [3]
   2. b)

      This part has equations that don’t show as text. Open the PDF to read it.

      [4]

7. Q7

   1. a)

      Draw the single line diagram of a HVDC system showing all components with proper labels. Explain the working of following components. i) Smoothing reactor ii) AC side HP filter iii) Converter transformer

      [9]
   2. b)

      Explain the control characteristic of HVDC system with proper characteristic diagram.

      [9]
   OR

8. Q8

   1. Write short note on any three of the following in details :

      [18]
   2. a)

      Monopolar HVDC

   3. b)

      Back to back HVDC

   4. c)

      Multi terminal HVDC

      Also asked:May 2025

   5. d)

      This part has equations that don’t show as text. Open the PDF to read it.