📘 Power Systems – Question Bank (Page 1)
🔹 Section A: Conceptual Questions
Q1. Why is power transmitted at high voltage?To reduce current and hence minimize I²R losses in transmission lines.
Q2. Define power factor.Power factor = cosφ = Real Power / Apparent Power.
Q3. What is load factor?Load Factor = Average Load / Maximum Load.
Q4. What is diversity factor?Diversity Factor = Sum of individual maximum demands / Maximum demand of system.
Q5. Why is per-unit system used?To simplify calculations and avoid large numerical variations.
🔹 Section B: MCQs
Q6. Increasing transmission voltage will:A) Increase losses
B) Decrease losses
C) Not affect losses
D) Increase current
Answer: B) Decrease losses
Q7. Load factor is always:A) > 1
B) = 1
C) < 1
D) Zero
Answer: C) < 1
Q8. Corona loss increases with:A) Decrease in voltage
B) Increase in conductor diameter
C) Increase in voltage
D) Increase in spacing
Answer: C) Increase in voltage
Q9. Base impedance in per-unit system is:A) Vbase × Ibase
B) Vbase / Ibase
C) Ibase / Vbase
D) Vbase² × Sbase
Answer: B) Vbase / Ibase
Q10. Ferranti effect occurs in:A) Short line
B) Medium line
C) Long line
D) DC line
Answer: C) Long line
🔹 Section C: Numerical Problems
Q11. A 3-phase system delivers 10 MW at 0.8 power factor. Find apparent power.S = P / cosφ = 10 / 0.8 = 12.5 MVA
Q12. A load has maximum demand of 100 MW and average load 60 MW. Find load factor.Load Factor = 60 / 100 = 0.6 (or 60%)
Q13. Transmission line resistance = 5 Ω. Current = 200 A. Find copper loss.Loss = I²R = (200)² × 5 = 200000 W = 200 kW
Q14. Base voltage = 11 kV, Base power = 100 MVA. Find base impedance.Zbase = V² / S = (11000)² / (100 × 10⁶) = 1.21 Ω
Q15. A 220 kV line carries 500 A. Find 3-phase power at unity PF.P = √3 × V × I = 1.732 × 220000 × 500 = 190.5 MW (approx)
Page 1 Completed – Power System Basics
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