Power System Transmission – PYQs

 

Power System Transmission –  PYQs

Q201. For a short transmission line, the receiving end voltage is always:
A) Greater than sending end
B) Less than sending end
C) Equal
D) Unpredictable
Ans: B (PYQ – SSC JE)

Q202. Ferranti effect is more pronounced in:
A) Short lines
B) Medium lines
C) Long lightly loaded lines
D) Loaded short lines
Ans: C (PYQ – GATE)

Q203. If reflection coefficient = 0, then:
A) No reflection
B) Full reflection
C) Open circuit
D) Short circuit
Ans: A (PYQ)

Q204. Surge impedance loading is maximum for:
A) Short line
B) Medium line
C) Long line
D) Independent of length
Ans: D (PYQ – GATE)

Q205. ABCD constants of a transmission line satisfy:
A) AD – BC = 0
B) AD – BC = 1
C) AD + BC = 0
D) AD + BC = 1
Ans: B (PYQ – GATE)

Q206. For 220 kV line, typical corona starting voltage is around:
A) 50 kV
B) 120 kV
C) 180 kV
D) 220 kV
Ans: B (PYQ – SSC JE)

Q207. Shunt compensation in transmission lines is used to:
A) Increase series reactance
B) Improve voltage profile
C) Reduce SIL
D) Reduce power factor
Ans: B (PYQ – GATE)

Q208. In bundled conductors, the effective inductance is:
A) Increased
B) Reduced
C) Constant
D) Zero
Ans: B (PYQ – GATE)

Q209. Transmission line efficiency increases when:
A) Voltage increases
B) Current decreases
C) Both A and B
D) Resistance increases
Ans: C (PYQ)

Q210. Corona discharge produces:
A) Ozone
B) Radio interference
C) Power loss
D) All of these
Ans: D (PYQ)

Q211. Reflection coefficient for matched load is:
A) +1
B) -1
C) 0
D) ∞
Ans: C (PYQ – GATE)

Q212. A 400 kV line with 20 discs in suspension string, the string efficiency is:
A) < 100%
B) 100%
C) > 100%
D) Not defined
Ans: A (PYQ)

Q213. Surge impedance of an overhead line is typically:
A) 100–200 Ω
B) 200–400 Ω
C) 500–800 Ω
D) >1000 Ω
Ans: B (PYQ – SSC JE)

Q214. In transmission lines, which parameter causes charging current?
A) Resistance
B) Inductance
C) Capacitance
D) Leakage
Ans: C (PYQ)

Q215. Kelvin’s law gives:
A) Maximum efficiency condition
B) Economic conductor size
C) Voltage regulation
D) Power transfer
Ans: B (PYQ – IES)

Q216. For maximum power transfer in transmission line:
A) δ = 90°
B) δ = 0°
C) δ = 180°
D) δ = 45°
Ans: A (PYQ – GATE)

Q217. Corona loss is more at:
A) High frequency
B) Low frequency
C) Zero frequency
D) DC supply
Ans: A (PYQ)

Q218. String efficiency can be improved by:
A) Increasing number of discs
B) Guard ring
C) Reducing conductor spacing
D) Increasing voltage
Ans: B (PYQ)

Q219. A 132 kV line is classified as:
A) Low voltage
B) Medium voltage
C) High voltage
D) Extra high voltage
Ans: C (PYQ – SSC JE)

Q220. Reflection coefficient at short-circuited line is:
A) +1
B) -1
C) 0
D) ∞
Ans: B (PYQ)

Q221. Surge impedance loading (SIL) is given by:
A) V²/Zc
B) V/Zc
C) V²/R
D) V²/L
Ans: A (PYQ – GATE)

Q222. Capacitance grading of cables is done to:
A) Increase corona
B) Reduce dielectric stress
C) Reduce insulation thickness
D) Increase losses
Ans: B (PYQ – IES)

Q223. The power loss due to corona is given by:
A) Peek’s formula
B) Kelvin’s formula
C) Steinmetz formula
D) Maxwell’s law
Ans: A (PYQ)

Q224. In a short transmission line model, which is neglected?
A) R
B) L
C) C
D) X
Ans: C (PYQ)

Q225. The shunt admittance of a transmission line is mainly due to:
A) Line resistance
B) Ground capacitance
C) Inductance
D) None
Ans: B (PYQ)

Q226. Surge impedance is:
A) √(L/C)
B) √(R/L)
C) √(L/R)
D) √(R/C)
Ans: A (PYQ – SSC JE)

Q227. Power transfer capability of a line depends on:
A) Voltage
B) Reactance
C) Load angle
D) All of these
Ans: D (PYQ – GATE)

Q228. Transposition of transmission line conductors is done to:
A) Reduce corona
B) Reduce interference with nearby lines
C) Equalize inductance and capacitance
D) Reduce resistance
Ans: C (PYQ)

Q229. Shunt reactors in EHV lines are mainly for:
A) Reactive power absorption
B) Reactive power generation
C) Voltage drop
D) Reduce resistance
Ans: A (PYQ – GATE)

Q230. Reflection coefficient magnitude is always:
A) ≤ 1
B) ≥ 1
C) = 0
D) = ∞
Ans: A (PYQ)

Q231. ACSR conductors are preferred because:
A) High strength
B) Less sag
C) Economical
D) All of these
Ans: D (PYQ – SSC JE)

Q232. Ferranti effect is absent in:
A) Short lines
B) Medium lines
C) Long lines
D) EHV lines
Ans: A (PYQ)

Q233. Which insulator is preferred for 400 kV lines?
A) Pin
B) Shackle
C) Suspension
D) Post
Ans: C (PYQ)

Q234. The surge impedance loading of a line increases with:
A) Voltage
B) Length
C) Resistance
D) Frequency
Ans: A (PYQ)

Q235. Radio interference due to corona is minimized by:
A) Bundle conductors
B) Ground wires
C) High resistance
D) Shunt reactors
Ans: A (PYQ)

Q236. The typical range of string efficiency is:
A) 40–50%
B) 60–70%
C) 70–80%
D) 90–100%
Ans: C (PYQ – SSC JE)

Q237. The Ferranti effect occurs because of:
A) Series resistance
B) Series inductance and shunt capacitance
C) Shunt conductance
D) None
Ans: B (PYQ – GATE)

Q238. In high-voltage transmission, the most significant line parameter is:
A) R
B) L
C) C
D) G
Ans: C (PYQ)

Q239. A tuned power line is one where:
A) Receiving end voltage = Sending end voltage
B) Power factor is unity
C) No reactive power
D) Line loss = 0
Ans: A (PYQ – GATE)

Q240. The corona inception voltage increases with:
A) Decrease in conductor diameter
B) Increase in conductor spacing
C) Increase in air density
D) Both B and C
Ans: D (PYQ)

Q241. For economical transmission, higher voltage is chosen to:
A) Reduce current
B) Reduce losses
C) Reduce conductor size
D) All of these
Ans: D (PYQ)

Q242. In cables, dielectric loss is proportional to:
A) f
B) f²
C) 1/f
D) √f
Ans: A (PYQ – IES)

Q243. When a transmission line is terminated in its surge impedance:
A) No reflection
B) Full reflection
C) Maximum reflection
D) Zero transmission
Ans: A (PYQ)

Q244. Which tower is used for angle location in transmission lines?
A) Suspension tower
B) Tension tower
C) Guyed tower
D) None
Ans: B (PYQ)

Q245. Skin effect in conductors increases with:
A) Decreasing frequency
B) Increasing frequency
C) Decreasing diameter
D) None
Ans: B (PYQ)

Q246. In a cable, the maximum stress occurs at:
A) Conductor surface
B) Outer sheath
C) Mid-point of dielectric
D) Neutral point
Ans: A (PYQ)

Q247. String insulator units are connected in:
A) Series
B) Parallel
C) Both series & parallel
D) Star
Ans: A (PYQ)

Q248. For overhead lines, the most economical conductor shape is:
A) Square
B) Hollow
C) Circular
D) Hexagonal
Ans: C (PYQ)

Q249. When transmission line length increases, Ferranti effect:
A) Decreases
B) Increases
C) Remains constant
D) Zero
Ans: B (PYQ)

Q250. In AC transmission, efficiency increases by:
A) Increasing voltage
B) Reducing losses
C) Power factor correction
D) All of these
Ans: D (PYQ – GATE)