Transmission Line Performance, Efficiency, Voltage Regulation, ABCD Constant Applications, and Power Flow

 Q101. The voltage regulation of a transmission line is defined as:

A) $\frac{V_s - V_r}{V_r} \times 100$
B) $\frac{V_r - V_s}{V_s} \times 100$
C) $\frac{V_s}{V_r} \times 100$
D) $\frac{V_r}{V_s} \times 100$
Ans: A

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Q102. Voltage regulation of a line depends mainly on:
A) Load power factor
B) Line resistance
C) Line reactance
D) All of the above
Ans: D

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Q103. A line has zero voltage regulation when the load power factor is:
A) Unity
B) Leading
C) Lagging
D) Zero
Ans: B

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Q104. In a transmission line, the sending-end power factor is:
A) Always lagging
B) Always leading
C) May be leading or lagging
D) Always unity
Ans: C

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Q105. When load power factor is lagging, the voltage regulation is:
A) Positive
B) Negative
C) Zero
D) Infinite
Ans: A

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Q106. When load power factor is leading, the voltage regulation is:
A) Negative
B) Positive
C) Zero
D) Constant
Ans: A

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Q107. Efficiency of a transmission line is maximum when:
A) Copper loss = Iron loss
B) Copper loss = Dielectric loss
C) Copper loss = Constant losses
D) Copper loss = Shunt losses
Ans: C

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Q108. Line efficiency =
A) $\frac{\text{Receiving end power}}{\text{Sending end power}} \times 100$
B) $\frac{V_r}{V_s} \times 100$
C) $\frac{I_r}{I_s} \times 100$
D) None
Ans: A

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Q109. The receiving-end power factor improves with:
A) Capacitive load
B) Inductive load
C) Resistive load
D) None
Ans: A

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Q110. The Ferranti effect results in overvoltage at the:
A) Sending end
B) Receiving end
C) Midpoint
D) Neutral point
Ans: B

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Q111. For better efficiency, transmission voltage should be:
A) Low
B) High
C) Medium
D) None
Ans: B

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Q112. The sending-end power is given by:
A) $V_s I_s \cos φ_s$
B) $V_r I_r \cos φ_r$
C) Both are equal under ideal conditions
D) None
Ans: A

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Q113. Voltage regulation of a short line is mainly due to:
A) Line resistance and reactance
B) Shunt capacitance
C) Corona
D) None
Ans: A

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Q114. The maximum efficiency of a transmission line occurs when:
A) $I^2 R = \text{Constant losses}$
B) $I^2 R < \text{Constant losses}$
C) $I^2 R > \text{Constant losses}$
D) None
Ans: A

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Q115. The ABCD constants are helpful in calculating:
A) Voltage regulation
B) Transmission efficiency
C) Power flow
D) All of the above
Ans: D

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Q116. The sending-end power factor angle (φₛ) is:
A) Greater than receiving end angle for lagging load
B) Equal for unity PF
C) Less for leading load
D) All of the above
Ans: D

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Q117. The transmission efficiency increases when:
A) Voltage increases
B) Power factor increases
C) Conductor size increases
D) All of the above
Ans: D

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Q118. Voltage regulation of a transmission line can be improved by:
A) Shunt capacitors
B) Series capacitors
C) Synchronous condensers
D) All of the above
Ans: D

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Q119. The power delivered to the load is maximum when:
A) Receiving-end voltage = Sending-end voltage
B) Load impedance = Characteristic impedance
C) Current = Maximum value
D) None
Ans: B

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Q120. The voltage regulation of a transmission line operating at leading PF is:
A) Negative
B) Positive
C) Zero
D) Unchanged
Ans: A

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Q121. The power transmitted by a line is given by:
A) $\frac{V_s V_r}{Z} \sin δ$
B) $\frac{V_s V_r}{X} \sin δ$
C) $\frac{V_s^2}{Z} \sin δ$
D) $V_s I_s \sin δ$
Ans: B

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Q122. The maximum power transfer occurs when δ =
A) 0°
B) 30°
C) 90°
D) 180°
Ans: C

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Q123. For a lossless line, A and D constants are equal to:
A) cosh(γl)
B) sinh(γl)
C) 1
D) Zero
Ans: A

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Q124. When δ is small, sin δ ≈
A) δ (in radians)
B) δ²
C) 0
D) 1
Ans: A

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Q125. The reactive power flow in a line depends mainly on:
A) Voltage magnitude difference
B) Power angle
C) Frequency
D) Resistance
Ans: A

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Q126. The active power flow in a line depends mainly on:
A) Power angle δ
B) Voltage difference
C) Capacitance
D) None
Ans: A

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Q127. If the line is open-circuited, current is:
A) Zero
B) Maximum
C) Minimum but non-zero
D) Infinite
Ans: A

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Q128. Power factor at the sending end is given by:
A) $\cos φ_s = \frac{P_s}{V_s I_s}$
B) $\cos φ_s = \frac{P_r}{V_r I_r}$
C) $\cos φ_s = \frac{V_r}{V_s}$
D) None
Ans: A

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Q129. If the load power factor decreases, voltage regulation:
A) Increases
B) Decreases
C) Remains same
D) Zero
Ans: A

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Q130. The power angle δ is the angle between:
A) $V_s$ and $V_r$
B) $V_s$ and $I_s$
C) $I_r$ and $V_r$
D) $I_s$ and $I_r$
Ans: A

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Q131. In a short line, voltage drop is mainly due to:
A) $IR + jIX$
B) $I^2R$
C) Capacitance effect
D) None
Ans: A

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Q132. For a medium line, capacitance is represented by:
A) Two shunt branches
B) One shunt branch
C) Series element
D) None
Ans: A

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Q133. The per-unit system is useful for:
A) Simplifying calculations
B) Reducing complexity in multi-voltage systems
C) Normalizing impedances
D) All of the above
Ans: D

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Q134. If $A = D = 1, B = jX, C = 0$, the line is:
A) Short lossless line
B) Long lossless line
C) Short line
D) None
Ans: C

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Q135. For medium line, ABCD constants are derived using:
A) Nominal-T or Nominal-π model
B) Exact distributed model
C) Simplified equations
D) None
Ans: A

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Q136. The magnitude of sending-end current is given by:
A) $I_s = C V_r + D I_r$
B) $I_s = A V_r + B I_r$
C) $I_s = C V_r + D I_r$
D) $I_s = D V_r + C I_r$
Ans: C

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Q137. The effect of series compensation is to:
A) Reduce line reactance
B) Increase power transfer capability
C) Improve stability
D) All of the above
Ans: D

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Q138. The effect of shunt compensation is to:
A) Improve voltage profile
B) Supply reactive power
C) Control power factor
D) All of the above
Ans: D

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Q139. The corona loss increases with:
A) Increase in voltage
B) Increase in frequency
C) Rough conductor surface
D) All of the above
Ans: D

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Q140. The skin effect increases with:
A) Frequency
B) Conductor diameter
C) Temperature
D) All of the above
Ans: D

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Q141. The Ferranti effect increases when:
A) Line length increases
B) Load decreases
C) Voltage increases
D) All of the above
Ans: D

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Q142. For leading load, receiving-end current leads voltage by:
A) Power factor angle
B) δ
C) π/2
D) None
Ans: A

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Q143. Line drop compensation in voltage regulators is used to:
A) Maintain constant voltage
B) Improve efficiency
C) Reduce losses
D) All
Ans: A

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Q144. The no-load charging current is due to:
A) Line capacitance
B) Line resistance
C) Inductance
D) None
Ans: A

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Q145. The reactive power at sending end is maximum when δ =
A) 0°
B) 45°
C) 90°
D) 180°
Ans: C

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Q146. For a lossless line, the reactive power flow is proportional to:
A) $V^2/X$
B) $V^2/R$
C) $V^2L$
D) $1/X$
Ans: A

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Q147. The receiving-end power factor is lagging if current:
A) Lags voltage
B) Leads voltage
C) In phase with voltage
D) None
Ans: A

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Q148. The line loadability can be increased by:
A) Increasing voltage
B) Decreasing reactance
C) Compensation
D) All of the above
Ans: D

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Q149. The voltage regulation is improved when:
A) Leading PF load
B) Lagging PF load
C) Inductive load
D) None
Ans: A

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Q150. The losses in a transmission line vary as:
A) I²
B) V²
C) f²
D) 1/I²
Ans: A

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Q151. Corona effect causes:
A) Power loss
B) Radio interference
C) Audible noise
D) All of the above
Ans: D

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Q152. The maximum power transfer is limited by:
A) Thermal limit
B) Voltage limit
C) Stability limit
D) All of the above
Ans: D

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Q153. The surge impedance loading increases with:
A) Square of voltage
B) Line length
C) Frequency
D) None
Ans: A

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Q154. The ABCD constants are complex for:
A) Long lines
B) Short lines
C) Both
D) None
Ans: A

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Q155. For small δ, the transmitted power is proportional to:
A) δ
B) δ²
C) sin δ
D) cos δ
Ans: A

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Q156. The magnitude of ABCD constants satisfies:
A) AD – BC = 1
B) AB – CD = 1
C) AC – BD = 0
D) AD + BC = 0
Ans: A

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Q157. When a line is heavily loaded, voltage drop:
A) Increases
B) Decreases
C) Constant
D) None
Ans: A

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Q158. In a transmission line, lagging current causes:
A) Lagging PF
B) Voltage drop
C) Increased losses
D) All
Ans: D

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Q159. For a resistive load, power factor =
A) 1
B) 0
C) lagging
D) leading
Ans: A

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Q160. The total reactive power in a long line depends on:
A) Shunt capacitance
B) Series inductance
C) Both A and B
D) None
Ans: C

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Q161. The Ferranti effect is negligible for:
A) Short lines
B) Medium lines
C) Long lines
D) High-voltage lines
Ans: A

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Q162. ABCD parameters are also known as:
A) Transmission matrix
B) Chain matrix
C) Two-port network matrix
D) All
Ans: D

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Q163. The surge impedance of a cable is:
A) 30–60 Ω
B) 400 Ω
C) 600 Ω
D) 300 Ω
Ans: A

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Q164. Voltage regulation is zero at:
A) Unity PF
B) Leading PF
C) Lagging PF
D) No load
Ans: B

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Q165. A line with zero resistance is called:
A) Lossless line
B) Ideal line
C) Infinite line
D) None
Ans: A

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Q166. For long EHV lines, voltage control is mainly by:
A) Shunt compensation
B) Series compensation
C) Tap changers
D) All
Ans: D

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Q167. The voltage regulation can be negative when:
A) Load PF is leading
B) Load PF is lagging
C) Load is unity
D) None
Ans: A

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Q168. Surge impedance loading (SIL) is used to express:
A) Natural loading of line
B) Maximum power transfer
C) Surge voltage
D) Surge current
Ans: A

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Q169. For a 220 kV line, SIL ≈
A) 150 MW
B) 250 MW
C) 300 MW
D) 400 MW
Ans: C

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Q170. The voltage drop per phase of a short line =
A) $I(R + jX)$
B) $I(R – jX)$
C) $I^2R$
D) $IR$
Ans: A

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Q171. The Ferranti effect increases with:
A) Frequency
B) Capacitance
C) Line length
D) All of the above
Ans: D

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Q172. The inductive reactance per km of a line depends on:
A) Conductor spacing
B) Conductor radius
C) Both
D) None
Ans: C

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Q173. Voltage regulation at leading PF is:
A) Negative
B) Positive
C) Zero
D) Infinite
Ans: A

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Q174. The receiving-end voltage is greater than the sending-end voltage due to:
A) Ferranti effect
B) Corona
C) Resistance
D) None
Ans: A

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Q175. For a 400 kV, 300 km line, most suitable model is:
A) Long line
B) Medium line
C) Short line
D) Nominal-π
Ans: A

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Q176. The power factor at sending end is lower than receiving end for:
A) Lagging load
B) Leading load
C) Unity load
D) None
Ans: A

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Q177. The reactive power absorbed by the line inductance is called:
A) Lagging vars
B) Leading vars
C) Capacitive vars
D) None
Ans: A

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Q178. The capacitive charging current leads voltage by:
A) 90°
B) 45°
C) 60°
D) 180°
Ans: A

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Q179. The active power loss in a line is due to:
A) Resistance
B) Reactance
C) Capacitance
D) Conductance
Ans: A

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Q180. The angle δ between $V_s$ and $V_r$ is known as:
A) Power angle
B) Load angle
C) Torque angle
D) All
Ans: D

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Q181. The surge impedance is purely:
A) Resistive
B) Reactive
C) Complex
D) None
Ans: A

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Q182. For a lossless line, A = D =
A) cos βl
B) sin βl
C) tan βl
D) cot βl
Ans: A

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Q183. The power factor of a purely capacitive circuit is:
A) Leading
B) Lagging
C) Unity
D) Zero
Ans: A

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Q184. The surge impedance loading is proportional to:
A) V²
B) V
C) 1/V
D) V³
Ans: A

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Q185. The Ferranti effect is mainly due to:
A) Charging current
B) Corona
C) Resistance drop
D) Inductive reactance
Ans: A

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Q186. The ratio of transmission line voltage to current under surge condition is called:
A) Surge impedance
B) Characteristic impedance
C) Both
D) None
Ans: C

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Q187. The receiving-end voltage increases with decrease in:
A) Load
B) Frequency
C) Capacitance
D) None
Ans: A

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Q188. For minimum losses, the transmission voltage should be:
A) High
B) Low
C) Medium
D) None
Ans: A

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Q189. The distributed nature of parameters becomes significant for lines longer than:
A) 200 km
B) 150 km
C) 250 km
D) 300 km
Ans: C

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Q190. In long line equations, γ =
A) √(ZY)
B) ZY
C) Z/Y
D) Y/Z
Ans: A

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Q191. Surge impedance of overhead line ≈
A) 400 Ω
B) 300 Ω
C) 200 Ω
D) 100 Ω
Ans: A

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Q192. The effect of shunt capacitance is to:
A) Improve voltage
B) Improve PF
C) Reduce losses
D) All
Ans: D

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Q193. The medium line can be approximated by:
A) Nominal-π
B) Nominal-T
C) Either
D) None
Ans: C

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Q194. The transmission line acts as a two-port network because:
A) It relates sending and receiving quantities
B) It has two ends
C) Both
D) None
Ans: C

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Q195. A long line with negligible losses is called:
A) Lossless line
B) Ideal line
C) Infinite line
D) None
Ans: A

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Q196. The load angle δ is small for:
A) Light loads
B) Heavy loads
C) Leading loads
D) Lagging loads
Ans: A

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Q197. The voltage regulation depends on:
A) Load current and PF
B) Line impedance
C) Both
D) None
Ans: C

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Q198. For high-voltage transmission, the main aim is to:
A) Reduce current
B) Reduce losses
C) Reduce voltage drop
D) All
Ans: D

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Q199. The ratio $\frac{V_r}{V_s}$ represents:
A) Voltage regulation factor
B) Transmission efficiency
C) Per-unit voltage ratio
D) None
Ans: A

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Q200. In transmission lines, the power factor at sending end is always:
A) Lower than receiving end (for lagging load)
B) Higher (for leading load)
C) Equal (for unity PF)
D) All of the above
Ans: D