Power System Transmission – PYQs

 

Power System Transmission –  PYQs

Q151. The accuracy of digital voltmeters is usually:
A) ±0.01%
B) ±0.1%
C) ±1%
D) ±5%
Ans: B (PYQ)

Q152. The power transmitted through a transmission line is proportional to:
A) sinδ
B) cosδ
C) tanδ
D) δ
Ans: A (PYQ – GATE)

Q153. In a string of suspension insulators, the voltage across the top disc is:
A) Maximum
B) Minimum
C) Same as others
D) Zero
Ans: B (PYQ)

Q154. Surge impedance loading (SIL) of a line depends on:
A) Conductor length
B) Surge impedance and voltage
C) Power factor
D) Load current
Ans: B (PYQ – GATE)

Q155. Ferranti effect is observed when:
A) Receiving end voltage > Sending end voltage
B) Sending end voltage > Receiving end voltage
C) Both equal
D) Voltage = 0
Ans: A (PYQ)

Q156. For 400 kV EHV lines, bundle conductors are used to:
A) Increase corona
B) Reduce corona
C) Reduce sag
D) Increase losses
Ans: B (PYQ)

Q157. String efficiency of suspension insulators is:
A) Less than 100%
B) Always 100%
C) More than 100%
D) Not defined
Ans: A (PYQ)

Q158. Surge impedance of a line is √(L/C). Its unit is:
A) Ohm
B) Henry
C) Siemens
D) None
Ans: A (PYQ – SSC-JE)

Q159. In overhead transmission lines, ground wires are used for:
A) Neutral return
B) Lightning protection
C) Reducing corona
D) Voltage control
Ans: B (PYQ)

Q160. The dominant line parameter in long EHV lines is:
A) R
B) L
C) C
D) G
Ans: C (PYQ)

Q161. Corona effect increases with:
A) Smooth conductors
B) Rain and dust
C) Lower voltage
D) Lower frequency
Ans: B (PYQ)

Q162. Power transfer capability of a transmission line increases with:
A) Increase in X
B) Increase in V
C) Increase in δ
D) Both B and C
Ans: D (PYQ – GATE)

Q163. Kelvin’s law is used to determine:
A) Transmission line insulation
B) Transmission line conductor size
C) Tower height
D) Line voltage
Ans: B (PYQ)

Q164. For a short transmission line, which parameter is neglected?
A) Resistance
B) Inductance
C) Capacitance
D) Reactance
Ans: C (PYQ)

Q165. The corona loss is proportional to:
A) V²
B) (V − Vc)²
C) I²
D) f²
Ans: B (PYQ)

Q166. Which insulator is used for high-voltage transmission lines?
A) Shackle
B) Pin
C) Suspension
D) Strain
Ans: C (PYQ)

Q167. Transmission line inductance per phase depends mainly on:
A) Conductor radius and spacing
B) Voltage level
C) Load current
D) Frequency
Ans: A (PYQ – GATE)

Q168. The reflection coefficient at an open-ended line is:
A) +1
B) -1
C) 0
D) ∞
Ans: A (PYQ)

Q169. In HVDC transmission, corona loss is:
A) More severe
B) Less severe than AC
C) Same as AC
D) None
Ans: B (PYQ)

Q170. Ferranti effect is mainly due to:
A) Inductance
B) Capacitance
C) Resistance
D) Frequency
Ans: B (PYQ)

Q171. A 400 kV line requires approx. how many suspension discs?
A) 3–4
B) 8–10
C) 20–25
D) 30–35
Ans: C (PYQ)

Q172. Power factor at no-load in a transmission line is:
A) Lagging
B) Leading
C) Unity
D) Zero
Ans: B (PYQ)

Q173. Transmission efficiency is maximum when:
A) Line resistance is zero
B) Constant loss = Copper loss
C) Corona loss = I²R loss
D) Load PF = 1
Ans: B (PYQ)

Q174. Surge impedance loading of 765 kV line is about:
A) 100 MW
B) 400 MW
C) 1000 MW
D) 2000 MW
Ans: D (PYQ)

Q175. Transposition of lines is done to:
A) Reduce corona
B) Equalize mutual inductance and capacitance
C) Improve PF
D) Increase SIL
Ans: B (PYQ)

Q176. A tuned power line is one in which:
A) Receiving end voltage = Sending end voltage
B) Receiving end power = Sending end power
C) No charging current
D) No losses
Ans: A (PYQ)

Q177. Reflection coefficient at short-circuited end of a line is:
A) +1
B) -1
C) 0
D) None
Ans: B (PYQ)

Q178. Surge impedance loading is independent of:
A) Line length
B) Surge impedance
C) Voltage
D) None
Ans: A (PYQ)

Q179. String efficiency increases with:
A) More discs
B) Guard rings
C) Less shunt capacitance
D) Both B and C
Ans: D (PYQ)

Q180. Corona results in:
A) Power loss
B) Radio interference
C) Ozone formation
D) All of these
Ans: D (PYQ)

Q181. The percentage resistance of a transmission line is typically:
A) 1–2%
B) 5–10%
C) 15–20%
D) >20%
Ans: A (PYQ)

Q182. Long lines are analyzed using:
A) Equivalent circuit
B) Hyperbolic functions
C) Short line model
D) Only ABCD constants
Ans: B (PYQ – GATE)

Q183. In which weather condition is corona more severe?
A) Winter
B) Summer
C) Foggy / Rainy
D) Clear weather
Ans: C (PYQ)

Q184. Shunt reactors are used in long EHV lines for:
A) Voltage rise
B) Reactive power absorption
C) Stability
D) Improving PF
Ans: B (PYQ)

Q185. If surge impedance of a line is 400 Ω and voltage is 220 kV, the SIL is:
A) 200 MW
B) 120 MW
C) 400 MW
D) 121 MW
Ans: D (PYQ – GATE)

Q186. ACSR conductors are used because:
A) More strength
B) Less sag
C) Economical
D) All of these
Ans: D (PYQ)

Q187. Which of the following gives leading reactive power?
A) Capacitor
B) Reactor
C) Inductor
D) Resistor
Ans: A (PYQ)

Q188. For economical transmission, the most important factor is:
A) Low current
B) High voltage
C) Both A and B
D) None
Ans: C (PYQ)

Q189. String insulator voltage distribution is:
A) Uniform
B) Non-uniform
C) Always equal
D) Random
Ans: B (PYQ)

Q190. The reflection coefficient is defined as:
A) Reflected / Incident wave
B) Incident / Reflected wave
C) Transmitted / Reflected wave
D) None
Ans: A (PYQ)

Q191. The charging current is directly proportional to:
A) Voltage
B) Voltage²
C) Current
D) Resistance
Ans: A (PYQ)

Q192. The wave velocity in a transmission line is approximately:
A) 3 × 10⁸ m/s
B) 3 × 10⁶ m/s
C) 3 × 10⁵ m/s
D) None
Ans: A (PYQ)

Q193. Stability of power system is increased by:
A) Series capacitor
B) Shunt reactor
C) Reduced X
D) Both A and C
Ans: D (PYQ)

Q194. Reflection coefficient at matched load is:
A) 0
B) 1
C) -1
D) ∞
Ans: A (PYQ)

Q195. SIL of 132 kV line is about:
A) 10 MW
B) 30 MW
C) 100 MW
D) 300 MW
Ans: C (PYQ)

Q196. For maximum power transfer, the condition is:
A) Zs = Zr*
B) Zs = Zr
C) Zs = 0
D) Zs = ∞
Ans: A (PYQ)

Q197. The capacitance of a single-phase line increases when:
A) Distance between conductors decreases
B) Conductor diameter decreases
C) Both A and B
D) None
Ans: A (PYQ)

Q198. If frequency increases, skin effect:
A) Decreases
B) Increases
C) Remains same
D) Zero
Ans: B (PYQ)

Q199. Ground clearance of EHV lines is governed mainly by:
A) Safety requirements
B) Voltage level
C) Tower design
D) All of these
Ans: D (PYQ)

Q200. The maximum power in a line is given by:
A) (EV/X) sinδ
B) (EV/X) cosδ
C) (EV/X) tanδ
D) (EV/X) δ
Ans: A (PYQ – GATE)