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MCQ
781. The operating speed of a relay depends upon the-
Rate of flux built up
Armature core air gap
Spring tension
All of these
782. 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.
783. 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
784. IDMT relays are used to protect the power transformers against-
External short-circuit
Overloads
Internal short-circuits
Both (a) and (b)
785. 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.
786. 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.
787. 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.
788. Average resistance of human body is-
500 ohms
1000 ohms
1500 ohms
2000 ohms
789. Factors on which soil resistance depends/RPCI--
depth of the electrode
moisture
Nacl
all the above
790. 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.
791. The most severe fault on the power system is-
there phase short circuit
line to line fault
double line to ground fault
single line to ground fault
792. A circuit breaker is essentially-
an automatic switch
a manual switch
a high-lightning arrester
none of the above
ব্যাখ্যা: A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit.
793. A fuse is a--
protective device
current limiting device
current controling device
none of the above
ব্যাখ্যাঃ in electronic and electrical engineering, a fuse is an electrical safety or protective device, that operates provide overcurrent protection of an electrical circuit
794. 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
795. 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.
796. 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.
797. Inverse time current relays are used for the protection of-
Feeders
Transformers
Alternators
Both A and B
ব্যাখ্যা: Inverse time current relays, operating time is inversely changed with current So, hich current will operate over current relay faster than lower ones. It is used feeders and transformers
798. In SF6 circuit breakers, the SF, gas-
has insulating properties
is non-inflammable
is non-poisonous
all of the above
799. A thermal protection switch can protect against-
Short-circuit
Overload
Temperature
Over voltage
800. For ground fault we prefer-
Plain impedance relay
Directional over current relay
Mho relay
Reactance relay