stability limits, corona, travelling waves, and voltage regulation

 

Q251. The steady-state power transfer equation is:
A) $P = \frac{V_s V_r}{X} \sin δ$
B) $P = V_s V_r X \sin δ$
C) $P = \frac{V_s V_r}{R} \cos δ$
D) $P = \frac{V_s^2}{X}$
Ans: A

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Q252. The maximum power transfer occurs when δ =
A) 45°
B) 60°
C) 90°
D) 120°
Ans: C

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Q253. For small δ, $\sin δ ≈$
A) δ (in radians)
B) δ²
C) 1
D) 0
Ans: A

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Q254. The stability limit of a transmission line is improved by:
A) Series compensation
B) Shunt compensation
C) Both
D) None
Ans: C

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Q255. The effect of shunt capacitors on voltage profile is:
A) Improvement
B) Reduction
C) No effect
D) Distortion
Ans: A

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Q256. Series capacitors in a transmission line:
A) Reduce net reactance
B) Increase power transfer
C) Improve stability
D) All
Ans: D

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Q257. A fully compensated line has:
A) X = 0
B) R = 0
C) G = 0
D) None
Ans: A

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Q258. The line efficiency increases with:
A) Higher voltage
B) Lower current
C) Better PF
D) All
Ans: D

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Q259. The reactive power at receiving end is given by:
A) $Q = \frac{V_s V_r}{X} \cos δ - \frac{V_r^2}{X}$
B) $Q = \frac{V_r^2}{X} \sin δ$
C) $Q = \frac{V_s V_r}{R} \sin δ$
D) None
Ans: A

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Q260. The transmission angle δ at no load is approximately:
A) Zero
B) 45°
C) 90°
D) None
Ans: A

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Q261. The power factor at sending end is usually:
A) Lower than at receiving end (for lagging load)
B) Equal
C) Higher
D) None
Ans: A

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Q262. For a lossless line, the receiving-end voltage is given by:
A) $V_r = V_s \cos βl - jI_s Z_c \sin βl$
B) $V_r = V_s \sin βl + I_s Z_c \cos βl$
C) Both are valid forms
D) None
Ans: A

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Q263. The Ferranti effect increases with:
A) Frequency
B) Line length
C) Line voltage
D) All
Ans: D

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Q264. The natural power (SIL) of a line is also called:
A) Surge impedance loading
B) Natural loading
C) Both
D) None
Ans: C

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Q265. A long line can be represented by:
A) Equivalent π or T circuit
B) Distributed parameters
C) Hyperbolic form
D) All
Ans: D

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Q266. The input impedance of an open-ended line is:
A) $jZ_c \cot βl$
B) $-jZ_c \cot βl$
C) $Z_c \tan βl$
D) $-Z_c \tan βl$
Ans: A

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Q267. The input impedance of a shorted line is:
A) $jZ_c \tan βl$
B) $-jZ_c \tan βl$
C) $Z_c \tan βl$
D) None
Ans: A

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Q268. A line length equal to λ/4 behaves as:
A) Impedance inverter
B) Open circuit
C) Short circuit
D) None
Ans: A

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Q269. The surge impedance depends only on:
A) L and C
B) R and G
C) L and R
D) All
Ans: A

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Q270. The power flow in a line is maximum when δ =
A) 90°
B) 0°
C) 45°
D) 60°
Ans: A

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Q271. The receiving-end voltage in long line equations increases if load is:
A) Leading
B) Lagging
C) Resistive
D) None
Ans: A

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Q272. The charging current of a line is:
A) Capacitive
B) Inductive
C) Resistive
D) None
Ans: A

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Q273. The “A” constant of a short line is:
A) 1
B) 0
C) Z
D) None
Ans: A

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Q274. The “C” constant of a short line is:
A) 0
B) 1/Z
C) 1/Y
D) None
Ans: A

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Q275. A two-port network has AD – BC =
A) 1
B) 0
C) –1
D) None
Ans: A

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Q276. The short-circuit receiving-end current is maximum when:
A) δ = 90°
B) δ = 0°
C) δ = 180°
D) None
Ans: B

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Q277. The reactive power loss in a line increases with:
A) Line length
B) Load current
C) Both
D) None
Ans: C

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Q278. The maximum reactive power transferable is:
A) $V_s V_r / X$
B) $V_s^2 / X$
C) $V_s V_r / 2X$
D) None
Ans: B

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Q279. In a long line, “D” constant is equal to:
A) cosh(γl)
B) sinh(γl)
C) tanh(γl)
D) None
Ans: A

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Q280. For a lossless line, A = D =
A) cos(βl)
B) sin(βl)
C) tan(βl)
D) None
Ans: A

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Q281. The open-circuit test on a line helps determine:
A) Charging capacitance
B) Inductance
C) Resistance
D) None
Ans: A

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Q282. The short-circuit test helps to determine:
A) Series impedance
B) Shunt capacitance
C) Line loss
D) None
Ans: A

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Q283. Voltage regulation is defined as:
A) $\frac{V_{NL} - V_{FL}}{V_{FL}} \times 100$
B) $\frac{V_{FL} - V_{NL}}{V_{FL}} \times 100$
C) $\frac{V_{NL}}{V_{FL}}$
D) None
Ans: A

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Q284. A negative voltage regulation indicates:
A) Leading load
B) Lagging load
C) Resistive load
D) None
Ans: A

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Q285. The per-unit system simplifies:
A) Power system calculations
B) Unit conversions
C) Transformer analysis
D) All
Ans: D

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Q286. Transmission efficiency =
A) $\frac{V_r I_r \cos φ}{V_s I_s \cos φ_s} × 100$
B) $\frac{V_r}{V_s} × 100$
C) $\frac{I_s}{I_r} × 100$
D) None
Ans: A

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Q287. The main advantage of high-voltage transmission is:
A) Reduction in line current
B) Reduction in I²R losses
C) Improved efficiency
D) All
Ans: D

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Q288. Corona discharge occurs when:
A) Voltage exceeds critical value
B) Voltage below breakdown
C) Temperature rises
D) None
Ans: A

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Q289. The critical disruptive voltage depends on:
A) Air density factor
B) Conductor size
C) Conductor spacing
D) All
Ans: D

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Q290. The corona power loss is proportional to:
A) f + 25
B) (f + 25) √r
C) fV²
D) None
Ans: A

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Q291. Increasing conductor diameter will:
A) Increase corona inception voltage
B) Reduce corona loss
C) Both
D) None
Ans: C

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Q292. The line capacitance per phase is expressed as:
A) $2π ε / \ln(D/r)$
B) $π ε / \ln(D/r)$
C) $1 / (π ε \ln(D/r))$
D) None
Ans: A

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Q293. For three-phase lines, equivalent spacing $D_m = (D_{ab} D_{bc} D_{ca})^{1/3}$:
A) True
B) False
Ans: A

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Q294. The inductance per phase for a single circuit line is:
A) $2 × 10^{-7} \ln(D_m / r')$ H/m
B) $4π × 10^{-7} / D$
C) $2π × 10^{-7} \ln(r/D_m)$
D) None
Ans: A

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Q295. The inductive reactance of a line increases with:
A) Frequency
B) Length
C) Both
D) None
Ans: C

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Q296. The capacitance between conductors increases with:
A) Decreasing distance
B) Increasing radius
C) Both
D) None
Ans: C

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Q297. The neutral current in a balanced three-phase line is:
A) Zero
B) Maximum
C) Minimum
D) None
Ans: A

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Q298. The line-to-line capacitance for a 3-φ line is equal to:
A) 3 × phase capacitance
B) ½ × phase capacitance
C) √3 × phase capacitance
D) None
Ans: C

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Q299. For a transposed line, mutual inductance between phases is:
A) Equalized
B) Unequal
C) Neglected
D) None
Ans: A

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Q300. Transposition of lines is done to:
A) Balance mutual inductance and capacitance
B) Reduce interference
C) Improve voltage regulation
D) All of the above
Ans: D