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MCQ
4541. The charging reactance of 50km transmission line is 1500Ω. What is the charging reactance for 100km length of line?
1500 Ω
750 Ω
300 Ω
1000 Ω
4542. The skin effect of conductor will increase when-
diameter decrease
resistivity decrease
frequency decrease
all of the above
4543. Which of the following statement is true?
At higher voltage, cost of transmission is reduced
At higher voltage, cost transmission is increased
efficiency decreased
all of the above
4544. Advantages of higher trans mission voltage is/are--
Power transfer capability of the transmission line is increased
Transmission line losses are reduced
Area of cross section and volume of the conductor is reduced
all of the above
4545. Proximity effect is more in case of-
power cables
same in both cases
overhead lines
none of the above
ব‍্যাখ্যা: Proximity effect is more in case of power cables. because the distance between the conductor is small.
4546. The presence of earth in case of overhead lines-
increase inductance
increase capacitance
decrease inducatance
decrease capacitance
ব‍্যাখ্যা: As the earth is considered to be an infinite source of electrons, the presence of overhead lines causes charge currier to be separated by a dielectric (air), causing an increase in capacitance.
4547. When power is to be transmitted over a distance of 250km, the transmission voltage should be-
66kV
132kV
33kV
11kV
Transmission lines are three types-Short transmission line (A length less than 80 km (50 miles) and voltage level less than 69kV) Medium Transmission line (A length more than 80km (50 miles) but less than 250km (150 miles) and voltage level is from 69kV to 132kV) Long transmission line (A length more than 250 km (150 miles) and voltage level is above 132kV)
4548. The main objectives of electrical power transmission is/are-
Transmission system must be more efficient with minimum line losses
Voltage regulation of the transmission line must be zero or minimum
both 1 and 2
neither I nor 2
4549. Four identical alternators each are rated for 20 MVA, 11KV having a subtransient reactance of 16% are working in parallel. The short circuit level at the busbar is-
500 MVA
400 MVA
125 MVA
100 MVA
4550. ACSR means-
Aluminium core steel reinforced
Aluminium conductor steel reinforced
Aluminium copper steel reinforced
reinforced all conductor steel
ব‍্যাখ্যা: ACSR = Aluminium conductor steel reinforced.
4551. If the fault current is 2000A, the relay setting is 50% and CT ratio is 400: 5, then plug setting multiplier will be-
10
25
15
50
4552. Which of the following rotor is used in thermal power plants?
cylindrical rotor
salient pole rotor
squirrel cage rotor
either of these
ব্যাখ্যা: Cylindrical rotor is also called as round rotor or smooth rotor. This rotor is mechanically very strong It's used in thermal power plants.
4553. Plog setting of a relay can be altered by varying-
air gap of magnetic path
adjustable back up stop
no. of ampere-turns
none of these
4554. The skin effect shows that-
the distribution of AC current is uniform through the cross section of the conductor
current density is more at the centre of the condutor
current density is lower at the surface of the condutor
current density is more at the surface of the condutor
ব‍্যাখ্যা: The skin effect depends on the surface area of the conductor. The skin effect in the solid conductor is more than the stranded conductor because the solid conductor has more surface area.
4555. Galvanised steel is generally used as--
stray wire
earth wire
structural components
all of the above
4556. Find the number of strands of ACSR conductor for 4 layer transmission line.
1
67
37
2
4557. Suspension insulators are used when transmission voltage is-
high
low
fluctuating
steady
ব্যাখ্যা: When transmission voltage is greater than 33kV, thes suspension insulator is used. It is consist of a number of glass or porcelain dises connected in series by metal links in the form of a string.
4558. Surge impedance loading of a 3-phase, 400k Y transmission line is 4002. The surge impedance loading is-
400MW
1600MW
800MW
200MW
4559. If the frequency is increased, then skin effect will—
increases
decreases
remains unaffected
any of the above
ব‍্যাখ্যা: The skin effect increases with the increase frequency
4560. India's largest thermal power station is located at--
Madhya Pradesh
Neyveli
Kota
Chandrapur