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MCQ
2361. For ground fault we prefer-
Plain impedance relay
Directional over current relay
Mho relay
Reactance relay
2362. 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.
2363. Factors on which soil resistance depends/RPCI--
depth of the electrode
moisture
Nacl
all the above
2364. 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
2365. 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
2366. 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.
2367. 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.
2368. The relay used for phase fault protection of short transmission lines is-
Reactance relay
Mho relay
Impedance relay
IDMT relay
2369. 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.
2370. 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.
2371. 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.
2372. The under voltage relay can be used for--
Generators
Bus bars
Transformers
All of the above
ব্যাখ্যা: Under voltage relay used for protection against voltage drops, to detect short-circuit fault, also used motor, alternators and in busbars.
2373. The relay with inverse time characteristic will operate within--
1.5 sec
5 to 20 sec
5 to 10 sec
20 to 30 sec
2374. 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.
2375. 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.
2376. 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.
2377. The single phasing relays are used for the protection of-
Single phase motors only
Two phase motors only
Two single phase motors running in parallel
Three phase motors
2378. 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.
2379. Average resistance of human body is-
500 ohms
1000 ohms
1500 ohms
2000 ohms
2380. 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