Part6— Electrical Engineering Interview Questions & Answers (MCQs)
Q.1 What is Admittance?
(a) It is equal to the Impedance.
(b) It is the square root of Impedance
© It is the inverse of Impedance
Answer: © It is the inverse of Impedance ✔
Explanation: (Z = 1/Y)
Q.2 Which equation represents the admittance?
(a) Y=R+jX
(b) Y=G+jB
© Y=G+jX
Answer: (b) Y=G+jB ✔
Q.3 What is the inverse of resistance?
(a) Susceptance
(b) Reactance
© Conductance
Answer: © Conductance ✔
Explanation: (B=1/R=conductance)
Q.4 If we have the voltage at bus 1 is V₁ and voltage at bus 2 is V₂ and admittance between both buses is Y. what is the formula for finding current flowing between both buses?
(a) I = V₁₂ * Y
(b) I = V₁₂ / Y
© I = Y / V₁₂
Answer: (a) I = V₁₂ * Y ✔
Q.5 If the voltage at bus 1 is Vᵢ and then we have multiple paths and current will flow from all paths. What will be the formula for finding total current which is also at bus 1? (n=total no of paths)
(a) Iᵢ=∑ⁿ ⱼ₌₁ Yᵢⱼ / Vⱼ
(b) Iᵢ=∑ⁿ ⱼ₌₁Yᵢⱼ*Vⱼ
Answer: (b) Iᵢ=∑ⁿ ⱼ₌₁ Yᵢⱼ*Vⱼ ✔
Q.6 The voltage at bus 1 is Vᵢ∠δᵢ and voltage at bus 2 is Vⱼ∠δⱼ, If the total current passing from bus 1 is Iᵢ which is the summation of all current passing through bus 1. What will be the total apparent power at bus 1?
(Iᵢ=∑ⁿ ⱼ₌₁ Yᵢⱼ ∗ Vⱼ ∠𝜃ᵢⱼ+𝛿ⱼ)
- Sᵢ=∑ⁿ ⱼ₌₁ Vᵢ ∗ Yᵢⱼ ∗ Vⱼ∠δⱼ−θᵢⱼ−δᵢ
- Sᵢ=∑ⁿ ⱼ₌₁ Vᵢ ∗ Yᵢⱼ ∗ Vⱼ∠δᵢ+θᵢⱼ+δⱼ
- Sᵢ=∑ⁿ ⱼ₌₁ Vᵢ ∗ Yᵢⱼ ∗ Vⱼ∠δᵢ−θᵢⱼ−δⱼ
Answer: Sᵢ=∑ⁿ ⱼ₌₁ Vᵢ ∗ Yᵢⱼ ∗ Vⱼ∠δᵢ−θᵢⱼ−δⱼ ✔
Explanation: S = VI* = Vᵢ ∗ Iᵢ* = Vᵢ∠δᵢ∑ⁿ ⱼ₌₁ Yᵢⱼ ∗ Vⱼ∠−θᵢⱼ−δⱼ, when we have conjugate on any parameter which is due to current when we find our apparent power then the angle of that parameter is inverted.
Q.7 If the real power entering at any bus is Pɢ and power leaving from that bus is Pʟ. How we can find the net real power at that bus?
Pʙ=Net real power at that bus
(a) Pʙ = Pɢ = Pʟ
(b) Pʙ = Pɢ — Pʟ
© Pʙ = Pɢ + Pʟ
Answer: (b) Pʙ = Pɢ — Pʟ ✔
Explanation: The net power at any bus is the difference of power entering at that bus and the power leaving from that bus.
Q.8 Why do we use the Newton Raphson Method in power systems?
(a) For finding the impedance in a power system
(b) For solving power flow equations
© None of the above
Answer: (b) For solving power flow equations ✔
Q.9 Shunt admittance in transmission lines is also referred to as..?
(a) Line Charging Inductance
(b) Line Charging Conductance
© Line Charging Capacitance
Answer: © Line Charging Capacitance ✔
Q.10 If impedance between two buses is j0.05 Ω. What will be admittance between these two buses?
(a) — j20 Ω
(b) j20 S
© — j20 S
Answer: © — j20 S ✔
Explanation: Y = 1/Z = 1/j0.05 = — j20 Siemens
Q.11 In the Y Bus matrix, what is meant by Y₂₃?
(a) Impedance between Bus 2 and Bus 3
(b) Admittance between Bus 3 and Bus 2
© Admittance between Bus 2 and Bus 3
Answer: © Admittance between Bus 2 and Bus 3 ✔
Q.12 For a Y Bus Matrix, What will be the value of Y₂₃ ? (Given values are admittances)
(a) — j0.25
(b) j0.3
© — j0.3
Answer: (b) j0.3 ✔
Explanation: Y₂₃= — 1( — j0.3) = j0.3
Q.13 What admittance will we take for diagonal admittance in the Y Bus matrix?
(a) Diagonal admittance is equal to 1 for all buses
(b) Diagonal admittance is the sum of all admittances connected to that bus
© Diagonal admittance is the sum of all admittances connected through all buses
Answer: (b) Diagonal admittance is the sum of all admittances connected to that bus ✔
Q.14 For a Y Bus Matrix, What will be the value of Y₁₁? (Given values are admittances)
(a) — j0.7375
(b) j0.0125
© j0.7375
Answer: (a) — j0.7375 ✔
Explanation: (Y₁₁= — j0.5 — j0.25 + j0.0125 = — j0.7375)
