Question 1

Protection by fuses is generally not used beyond

Accepted Answer

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

Question 2

The material used for fuse must have

Accepted Answer

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 A

Question 3

Circuit breakers usually operate under

Accepted Answer

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

Question 4

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

Accepted Answer

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

Question 5

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

Accepted Answer

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 6

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

Accepted Answer

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

Question 7

A fuse is connected

Accepted Answer

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 8

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

Accepted Answer

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 9

The fuse rating is expressed in terms of

Accepted Answer

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

Question 10

Over voltage protection is recommended for

Accepted Answer

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

Question 11

SF6 is which type of gas?

Accepted Answer

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

Question 12

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

Accepted Answer

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

Question 13

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

Accepted Answer

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 14

A fuse is never inserted in

Accepted Answer

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

Question 15

Admittance relay is _______ relay.

Accepted Answer

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

Question 16

An isolator is installed

Accepted Answer

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 17

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

Accepted Answer

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

Question 18

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

Accepted Answer

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

Question 19

Overfluxing protection is recommended for

Accepted Answer

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

Question 20

A fuse in a motor circuit provides protection against

Accepted Answer

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

Exam 4: Electrical Protection and Safety: Part A