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MCQ
81. The ring main system is used in power distribution because it--
is reliable for continuity of supply
gives better voltages regulation
results in less feeder losses
all of the above
ব্যাখ্যা: There are less voltage fluctuations at consumer terminals. The system is very reliable as each distributor is fed via two feeders. In the event of fault on any section of the feeder, the continuity of supply is maintained
82. the minimum phase -neutral voltage at which corona occurs, is called-
critical disruptive voltage
visual critical voltage
fieash over voltage
none of the above
83. For a single circuit 3 phase line the inductance per phase per km is of the order of--
1mH
0.2mH
10 mH
0.1 mH
84. Corona is affected by-
condition of atmosphere
line voltage
size & spacing of conductor
all of the above
85. The common fault is overhead distribution system is-
phase to phase fault
one phase to earth fault
all phase short circuited
none of the above
ব্যাখ্যা: About 50-55% fault in overhead distribution system is one phase to earth fault and 12-15% fault is phase in phase fault
86. The surge impedance for over head line is taken as-
10-202 Ω
100-200 Ω
50-600 Ω
1000-2000Ω
87. At distribution substation voltage is stepped down to-
66kV
132kV
11kV
415/230 Volts
88. When the load factor of a power station increases, the units (kwh) generated-
are increased
remain the same
are decreased
none of these
89. The highest point on the daily load curve represents-
average load
load factor
maximum load
none of the above
90. Modern high-voltage lines are designed with a safety factor of about --
1.5
2
3
4
91. TStability of a system is not affected by-
Reactance of line
Losses
Reactance of generator
Output torque
ব্যাখ্যা: Stability of power system is affected by- -Reactance of transmission line -Reactance of generator -Excitation of generator -Input output torque.
92. Capacitance of a transmission line is the result of-
Potential diference between the conductors
Current flow in both conductors
Current flow in either conductors
Charge per unit current
ব্যাখ্যা: Capacitance of a transmission line is the results due to the potential difference between the conductors. The conductors get charged in the same way as the parallel plates of a capacitor, capacitance between two parallel conductors depends on the size and the spacing between the conductors
93. The line voltage on the LT side of a distribution transformer is--
400V
230V
11KV
33kV
ব্যাখ্যাঃA LT (Low Tension) line is a low voltage line and ITT (High Tension) line is a high voltage line. In LT supply is of 400 volt for three-phase connection and 230 volt for single-phase connection. High tensione HT supply is applicable for bulk purchase who need 11 kilo-volt (kV).
94. The most severe unsymmetrical fault is-
single line-to-ground fault
line-to-line fault
double line-to-ground fault
none of the above
ব্যাখ্যা: Symmetrical three phase fault is the most severe kind at the transmission lines, while for faults occurring very close to the generating station or synchronous generator, single line to ground fault is the most severe.
95. Potential difference to any equal charge is measured in,
coulomb
Ampere
joule
volt
ব্যাখ্যা: The unit of potential difference between any two equal charges is volt.
96. Which of the following is not the distribution system, normally used-
3 phase 4 wire
Single phase-3 wire
Single phase -4 wire
3 phase-3 wire
ব্যাখ্যা 2 AC distribution system can be classified as- -Single phase-2 wire system -Sinele phase-3 wire system -Two phase-3 wire system -Two phase-4 wire system -Three phase-3 wire system -Three phase-4 wire system
97. In de transmission, the skin effect is-
large
zero
small
depends on voltage
98. For a distortionless transmission line --
R/L = G/C
RG=LC
RL= GC
RLGC-0
99. The distribution transformer is generally connected in--
Delta/Delta
Star/Delta
Star/Star
Delta/Star
ব্যাখ্যা: The distribution transformer is generally connected in deta/star. In secondary side, star connection is required which has neutral point. From this star connection. Voltage is used by consumers.
100. A line which connects distributor to substation is called--
service mains
distributor
feeder
infinity