📘 Power Systems – Mega Mixed Test (Page 12)
🔹 Section A: MCQ (Concept + Numerical)
Q1. Base impedance at 11 kV, 100 MVA is:A) 1.21 Ω
B) 12.1 Ω
C) 0.121 Ω
D) 121 Ω
Answer: A) 1.21 Ω
Q2. Ferranti effect is due to:A) Resistance
B) Inductance
C) Capacitance
D) Frequency
Answer: C) Capacitance
Q3. Fault current increases when:A) Impedance increases
B) Voltage decreases
C) Impedance decreases
D) Frequency decreases
Answer: C) Impedance decreases
Q4. For SLG fault, sequence networks connected in:A) Parallel
B) Series
C) Only positive
D) Only zero
Answer: B) Series
Q5. Maximum power transfer occurs at:A) 60°
B) 45°
C) 90°
D) 120°
Answer: C) 90°
🔹 Section B: Numerical Problems
Q6. A 132 kV system has short circuit current 15 kA. Find fault MVA.Fault MVA = √3 × V × I = 1.732 × 132 × 15 = 3429 MVA (approx)
Q7. Two generators have incremental costs: dC1/dP1 = 0.04P1 + 5 dC2/dP2 = 0.06P2 + 4 Total load = 200 MW. Find economic load sharing.
Set equal: 0.04P1 + 5 = 0.06P2 + 4 P1 + P2 = 200 Solve: 0.04P1 - 0.06P2 = -1 Multiply by 100: 4P1 - 6P2 = -100 Substitute P1 = 200 - P2: 4(200 - P2) - 6P2 = -100 800 - 4P2 - 6P2 = -100 800 - 10P2 = -100 10P2 = 900 P2 = 90 MW P1 = 110 MW
Q8. Generator reactance = 0.25 pu. Find 3-phase fault current.
I = 1 / 0.25 = 4 pu
Q9. HVDC line ±400 kV carries 1500 A. Find transmitted power.
P = V × I = 400,000 × 1500 = 600 MW
Q10. If system frequency drops from 50 Hz to 49.8 Hz, find % frequency deviation.
Deviation = (0.2 / 50) × 100 = 0.4%
🔹 Section C: Quick Revision Checklist
- Per Unit System basics
- Transmission line effects
- Symmetrical & Unsymmetrical faults
- Stability power angle
- Economic dispatch
- LFC & AVR
- HVDC & FACTS
- Protection coordination
Power Systems Question Bank Series Completed (Page 1–12)
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