Power System Transmission – Set 3 (Q101–Q150)

 

Power System Transmission – Set 3 (Q101–Q150)

Q101. The main cause of corona in transmission lines is:
A) Low voltage
B) High current
C) High electric field intensity
D) Low frequency
Ans: C

Q102. The unit of line charging susceptance is:
A) Siemens
B) Ohm
C) Henry
D) Farad
Ans: A

Q103. The surge impedance of a line depends on:
A) L and C per unit length
B) R and G per unit length
C) Voltage level only
D) Frequency only
Ans: A

Q104. The power transmitted over a line depends on:
A) Sending end voltage
B) Receiving end voltage
C) Line reactance
D) All of these
Ans: D

Q105. In overhead lines, the effect of wind load is to:
A) Reduce sag
B) Increase sag
C) Reduce tension
D) None
Ans: B

Q106. The dielectric strength of air under normal conditions is approximately:
A) 1 kV/cm
B) 3 kV/cm
C) 10 kV/cm
D) 30 kV/cm
Ans: B

Q107. The effect of series capacitors in transmission lines is to:
A) Increase line reactance
B) Decrease line reactance
C) Increase resistance
D) Reduce capacitance
Ans: B

Q108. The phenomenon of potential equalization in insulator string is improved by:
A) Reducing number of discs
B) Grading rings
C) Increasing string length
D) Using pin insulators
Ans: B

Q109. The reactive power flow in transmission line is proportional to:
A) V²/X
B) (EV/X) sinδ
C) (EV/X) cosδ
D) V/X
Ans: A

Q110. The propagation constant of a transmission line is:
A) √(ZY)
B) √(R/L)
C) √(L/C)
D) √(R/G)
Ans: A

Q111. For minimum corona loss, conductor surface should be:
A) Rough
B) Smooth
C) Thin
D) Sharp-edged
Ans: B

Q112. The effect of temperature on corona is:
A) Negligible
B) Increases at high temperature
C) Reduces at high temperature
D) Same at all
Ans: C

Q113. High voltage transmission lines use suspension insulators because:
A) Cheaper
B) Flexible and can be added
C) Good mechanical strength
D) All of these
Ans: D

Q114. The surge impedance loading of a line increases with:
A) Increase in surge impedance
B) Increase in voltage
C) Increase in frequency
D) Both A and B
Ans: D

Q115. In long lines, the relation between sending and receiving end quantities is given by:
A) ABCD constants
B) ZY parameters
C) Y-bus matrix
D) Load flow equations
Ans: A

Q116. In overhead lines, the ground clearance increases with:
A) Higher voltage
B) Lower voltage
C) Frequency
D) Power factor
Ans: A

Q117. String efficiency is improved by:
A) Reducing shunt capacitance
B) Using guard rings
C) Using fewer discs
D) Both A and B
Ans: D

Q118. Ferranti effect is more pronounced at:
A) Light load, long line
B) Heavy load, short line
C) Unity PF load
D) Balanced load
Ans: A

Q119. For EHV transmission, which factor dominates?
A) Line resistance
B) Line capacitance
C) Load power factor
D) Frequency
Ans: B

Q120. The major cause of transmission line losses is:
A) Corona
B) I²R loss
C) Leakage current
D) Dielectric loss
Ans: B

Q121. A lossless line means:
A) R = 0, G = 0
B) L = 0, C = 0
C) R = 0, C = 0
D) L = 0, G = 0
Ans: A

Q122. For minimum sag, the conductor tension should be:
A) Low
B) High
C) Zero
D) Moderate
Ans: B

Q123. The corona loss is least affected by:
A) Conductor surface
B) Frequency
C) Atmospheric conditions
D) Line length
Ans: D

Q124. The shunt conductance of a line accounts for:
A) Dielectric leakage
B) I²R loss
C) Corona
D) Ferranti effect
Ans: A

Q125. In a short line model, which parameters are considered?
A) R and L
B) R and C
C) L and C
D) R, L, C
Ans: A

Q126. If the length of a line is more than 250 km, it is treated as:
A) Short line
B) Medium line
C) Long line
D) None
Ans: C

Q127. Corona increases:
A) Transmission efficiency
B) Transmission loss
C) String efficiency
D) Stability
Ans: B

Q128. The wave propagation speed in a transmission line is nearly equal to:
A) Speed of sound
B) Speed of light
C) Speed of electrons
D) None
Ans: B

Q129. The surge impedance of a line is expressed in:
A) Ohms
B) Henry
C) Siemens
D) Farads
Ans: A

Q130. Bundled conductors are used in EHV lines to reduce:
A) Corona loss
B) Surge impedance
C) Line reactance
D) All of these
Ans: D

Q131. In a string of insulators, the disc nearest to the conductor has:
A) Minimum voltage
B) Maximum voltage
C) Equal voltage
D) Zero voltage
Ans: B

Q132. For economical transmission, the line voltage is increased because:
A) Current decreases
B) Losses decrease
C) Conductor size decreases
D) All of these
Ans: D

Q133. In overhead lines, earth wire is placed:
A) Below conductors
B) Above conductors
C) Side of conductors
D) Parallel at ground
Ans: B

Q134. The inductive reactance per km of a line depends on:
A) Conductor spacing and size
B) Voltage
C) Current
D) Frequency only
Ans: A

Q135. Transposition is carried out in:
A) Short lines
B) Long lines
C) Distribution lines
D) Cables
Ans: B

Q136. The characteristic impedance of a line is independent of:
A) Voltage
B) Length
C) Both A and B
D) L and C
Ans: C

Q137. The resistance of a transmission line conductor increases with:
A) Lower temperature
B) Higher temperature
C) Humidity
D) Altitude
Ans: B

Q138. Ground wires protect transmission lines from:
A) Over-voltage surges
B) Over-current
C) Corona
D) Ferranti effect
Ans: A

Q139. The reflection coefficient at a short-circuited line end is:
A) +1
B) -1
C) 0
D) ∞
Ans: B

Q140. Voltage regulation in a transmission line improves with:
A) Series capacitor
B) Shunt reactor
C) Resistance reduction
D) All of these
Ans: D

Q141. A synchronous phase modifier is used to:
A) Improve PF
B) Reduce sag
C) Control frequency
D) Eliminate corona
Ans: A

Q142. The surge impedance loading is independent of:
A) Line length
B) Voltage level
C) Surge impedance
D) None
Ans: A

Q143. For a given line, SIL is proportional to:
A) V²/Zc
B) V/Zc
C) I²R
D) (EV/X) sinδ
Ans: A

Q144. The ABCD constants of a short line are:
A = 1, D = 1, B = Z, C = 0
B = 0, C = Y, A = D = 1
C = Z, D = Y, A = 0, B = 0
None
Ans: A

Q145. For a nominal T-model, the capacitance is divided:
A) Half at each end
B) Full at middle
C) Neglected
D) Divided unequally
Ans: B

Q146. An uncompensated line at light load suffers from:
A) Voltage rise (Ferranti)
B) Voltage drop
C) Corona
D) Sag
Ans: A

Q147. For HVDC lines, corona is:
A) More severe
B) Less severe
C) Same as AC
D) Negligible
Ans: B

Q148. The surge impedance loading of 220 kV line is typically:
A) 50 MW
B) 100 MW
C) 400 MW
D) 1000 MW
Ans: C

Q149. Voltage regulation is zero when:
A) Sending voltage = Receiving voltage
B) Line is short
C) Power factor = 1
D) SIL is maximum
Ans: A

Q150. Stability of power system increases with:
A) Lower X
B) Higher V
C) Lower δ
D) All of these
Ans: D