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সুইচ গিয়ার এন্ড প্রটেকশন MCQ
101. A thermal protection switch can protect against-
Short-circuit
Overload
Temperature
Over voltage
102. An ideal location for the substation would be at ---the of load.
Centre of gravity
Load centre
Nearer to consumer
None of the above
ব্যাখ্যা: Ideal location for an electrical substation for a grang building will be at the electrical load center.
103. In sheet metal blanking, shear is provided on punches and dies so that--
press load is reduced
good cut edge in obtained
warping of sheet is minimized
cut blanks are straight
104. Factors on which soil resistance depends/RPCI--
depth of the electrode
moisture
Nacl
all the above
105. Where severe synchronising swing occur, the relay employed is
Impedance relay
Mho relay
Reactance relay
Induction relay
ব্যাখ্যা: Mhe relay can protect from power swing better than impedance relay and has the directional property which 1 is essential in transmission lines.
106. The relay used for phase fault protection of short transmission lines is-
Reactance relay
Mho relay
Impedance relay
IDMT relay
107. The over-voltage surge in power systems may be caused by-
Lightning
Resonance
Switching
All of the above
ব্যাখ্যা: The main cause of these voltage surges in power system are due to lighting impulses and switching impulses of the system.
108. In aluminium conductors, steel core is provided to-
compensate for skin effect
neutralise proximity effect
reduce line inductance
increases the tensile strength
ব্যাখ্যা: Aluminium is light in weight and is having good conductivity. But it is having very low tensile strengst To make it suitable to be used as a conductor for the transmission line, we need to increase its tensile strength. To increase the tensile strength steel is used as a core of conductor.
109. Surge absorbers are used for protection against-
High-voltage low-frequency oscillations
High-voltage high-frequency oscillations
Low-voltage high-frequency oscillations
Low-voltage low-frequency oscillations
ব‍্যাখ্যা: Surge observers are used for protection against low- voltage high frequency oscillations.
110. Average resistance of human body is-
500 ohms
1000 ohms
1500 ohms
2000 ohms
111. The voltage of a particular bus is regulated by controlling the --
Active power of the bus
Reactive power of the bus
Phase angle
Phase angle and reactive power
ব্যাখ্যা: The voltage of a particular bus can be controlled by controlling the active power of the bus
112. For the protection of lines against faults Involving variable fault resistance, the preferred relaying scheme is a-
Plain impedance relay
Directional over-current relay
Mho relay
Reactance relay
ব্যাখ্যা: Reactance type relay is very suitable as a ground relay for ground fault because its reach is not affected by Jault impedance.
113. The main function of a fuse is to-
Protect the line
Open the circuit
Prevent excessive currents
None of the above
ব্যাখ্যা: The main function of the fuse is to provide over curren protection of either the load of source circuit and prevent excessive currents.
114. The relay used for feeder protection --
Under voltage relay
Translay relay
Thermal relay
Buchholz relay
ব্যাখ্যা: The armingement is similar to over current relay, but the secondary winding is not closed on nelf. These types of relays are ward in the feeder protection and the scheme is called the Translay relay
115. Which of the following equipment is used to limit short circuit current level in a sub-station?
Isolator
Lightning switch
Coupling capacitor
Series reactor
ব‍্যাখ্যা: Series reactors are mosily sard to limit short circuit current level in a substation.
116. The bus-bar zone, the purpose of protection includes-and-
Bus-bars, isolating switches, circuit breakers
Transformers, relays, circuit breakers
Transformers, conductors and relays
None of the above
ব্যাখ্যা: The busbar zone, for the purpose of protection, includes not only the busbars themselves but also the isolating switches, circuit breakers and the associated connections.
117. Admittance relay-
Non-directional relay
Directional relay
Differential relay
None of the above
ব্যাখ্যা: A mo relay is a high-speed relay and is also known as the infmittance relay. In this relay operating torque is obtained by the voli-amperes element and the controlling element is developed due to the voltage element. It means a mho relay is a sobage controlled directional relics.
118. In the case of transmission line protection, over current relay is used-
Only up to 110kV
Only up to 220kV
Only up to 50k V
Only up to 1100k V
119. Outdoor sub-station requires-space.
Less
More
Medium
Any of the above
ব্যাখ্যা: More space is required for the outdoor, subutatione Protection devices are required to be installed for the protection against lighting surges.
120. For ground fault we prefer-
Plain impedance relay
Directional over current relay
Mho relay
Reactance relay