Deck 4: Electrical Protection and Safety: Part A

Question 1

Over voltage protection is recommended for

A)hydro-electric generators
B)steam turbine generators
C)gas turbine generators
D)all of the above

Answer 1

all of the above

Question 2

Air blast circuit breakers for 400 kV power system are designed to operate in

A)100 microsecond
B)50 millisecond
C)0.5 sec
D)0.1 sec

Answer 2

50 millisecond

Question 3

Overfluxing protection is recommended for

A)distribution transformer
B)generator transformer of the power plant
C)auto-transformer of the power plant
D)station transformer of the power plant

Answer 3

generator transformer of the power plant

Question 4

Series capacitors are used to

A)compensate for line inductive reactance
B)compensate for line capacitive reactance
C)improve line voltage
D)none of the above

Question 5

Admittance relay is _______ relay.

A)impedance
B)directional
C)non-directional
D)none of the above

Question 6

The material used for fuse must have

A)low melting point and high specific resistance
B)low melting point and -low specific resistance
C)high melting point and low specific resistance
D)low melting point and any specific resistance

Question 7

If the fault occurs near the impedance relay, the VII ratio will be

A)constant for all distances
B)lower than that of if fault occurs away from the relay
C)higher than that of if fault occurs away from the relay
D)none of the above

Question 8

The torque produced in induction type relay (shaded pole structure) is

A)inversely proportional to the current
B)inversely proportional to the square of the current
C)proportional to the current
D)proportional to square of the current

Question 9

The steady state stability of the power system can be increased by

A)connecting lines in parallel
B)connecting lines in series
C)using machines of high impedance
D)reducing the excitation of machines

Question 10

The inductive interference between power and communication line can be minimized by

A)transposition of the power line
B)transposition of the communication line
C)both (A) and (B)
D)increasing the distance between the conductors

Question 11

The power loss is an important factor for the design of

A)transmission line
B)motor
C)generator
D)feeder

Question 12

A fuse is connected

A)in series with circuit
B)in parallel with circuit
C)either in series or in parallel with circuit
D)none of the above

Question 13

H.R.C. fuse, as compared to a rewirable fuse, has

A)no ageing effect
B)high speed of operation
C)high rupturing capacity
D)all of the above

Question 14

The fuse rating is expressed in terms of

A)current
B)voltage
C)VAR
D)kVA

Question 15

The fuse blows off by

A)burning
B)arcing
C)melting
D)none of the above

Question 16

On which of the following effects of electric current a fuse operates ?

A)Photoelectric effect
B)Electrostatic effect
C)Heating effect
D)Magnetic effect

Question 17

An isolator is installed

A)to operate the relay of circuit breaker
B)as a substitute for circuit breaker
C)always independent of the position of circuit breaker
D)generally on both sides of a circuit breaker

Question 18

A fuse in a motor circuit provides protection against

A)overload
B)short-circuit and overload
C)open circuit, short-circuit and overload
D)none of the above

Question 19

Protection by fuses is generally not used beyond

A)20 A
B)50 A
C)100 A
D)200 A

Question 20

A fuse is never inserted in

A)neutral wire
B)negative of D.C. circuit
C)positive of
D)C. circuit

Question 21

Which of the following circuit breakers is used for the railway electrification?

A)Air blast circuit breaker
B)SF6 circuit breaker
C)Bulk oil circuit breaker
D)Minimum oil circuit breaker

Question 22

The stability of arc in vacuum depends on _________.

A)The contact material only.
B)The circuit parameters only.
C)The contact materials and its vapour pressure.
D)Both (b) and (c)

Question 23

SF6 is which type of gas?

A)Electro positive
B)Electro negative
C)Both (a) and (b)
D)None of these

Question 24

What is the average rate of rise of restriking voltage upto the first peak?

A)525 * 103kV / sec
B)453 * 103kV / sec
C)582 * 103 kV / sec
D)467 * 103 kV / sec

Question 25

Circuit breakers usually operate under

A)Steady short circuit current
B)Sub transient state of short circuit current
C)Transient state of short circuit current
D)None of these