Question 1

Which of the following circuit breakers has high reliability and minimum maintenance ?
A)Air blast circuit breakers
B)Circuit breaker with SF6 gas
C)Vacuum circuit breakers
D)Oil circuit breakers

Accepted Answer

B

Question 2

Arc in a circuit breaker is interrupted at
A)zero current
B)maximum current
C)minimum voltage
D)maximum voltage

Accepted Answer

Arc in a circuit breaker is interrupted at zero current because it is the point where the electrical power is minimal, making it easier to extinguish the arc.

Question 3

transmission line has reflection coefficient as one.
A)Open circuit
B)Short-circuit
C)Long
D)None of the above

Accepted Answer

An open circuit at the end of a transmission line results in a reflection coefficient of one because the incident wave is fully reflected back without any energy being transferred to a load.

Question 4

What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ?
A)Zero
B)Unity
C)Infinity
D)None of the above

Accepted Answer

The reflection coefficient ($\Gamma$) is given by $\Gamma = \frac{Z_L - Z_0}{Z_L + Z_0}$, where $Z_L$ is the load impedance and $Z_0$ is the characteristic impedance (or surge impedance) of the line. If $Z_L = Z_0$, then $\Gamma = 0$, indicating no reflection.

Question 5

The inverse definite mean time relays are used for over current and earth fault protection of transformer against
A)heavy loads
B)internal short-circuits
C)external short-circuits
D)all of the above

Accepted Answer

The answer of The inverse definite mean time relays are...

Question 6

Over voltage protection is recommended for
A)hydro-electric generators
B)steam turbine generators
C)gas turbine generators
D)all of the above

Accepted Answer

Over voltage protection is recommended for all types of generators, including hydro-electric, steam turbine, and gas turbine generators, to prevent damage to the equipment and ensure safe operation.

Question 7

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

Accepted Answer

Air blast circuit breakers for a 400 kV power system are designed to operate in the range of milliseconds, typically around 50 milliseconds, to effectively interrupt high voltage circuits and ensure safety and reliability in power distribution.

Question 8

Overfluxing protection is recommended for
A)distribution transformer
B)generator transformer of the power plant
C)auto-transformer of the power plant
D)station tr

Accepted Answer

Overfluxing protection is recommended for distribution transformers to protect them from damage due to excessive magnetic flux.

Question 9

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

Accepted Answer

Series capacitors are used to compensate for line inductive reactance, which helps in improving the power transfer capability of long transmission lines by reducing the effective reactance of the line.

Question 10

Admittance relay is _______ relay.
A)impedance
B)directional
C)non-directional
D)none of the above

Accepted Answer

Admittance relay is a type of directional relay. It is designed to operate in a specific direction of power flow, which makes it suitable for applications requiring direction sensitivity, such as in protection schemes for power systems.

Question 11

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

Accepted Answer

The material used for a fuse must have a low melting point and high specific resistance. This ensures that the fuse will melt quickly to interrupt the circuit when excessive current flows, protecting the circuit components from damage. High specific resistance helps in generating heat quickly due to higher resistance to current flow.

Question 12

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

Accepted Answer

When a fault occurs near an impedance relay, the impedance seen by the relay is lower, resulting in a higher current flow for the same voltage. This leads to a lower Voltage to Current (V/I) ratio compared to when a fault occurs further away from the relay.

Question 13

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

Accepted Answer

The answer of The torque produced in induction type relay...

Question 14

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

Accepted Answer

Connecting lines in parallel increases the overall capacity to carry more current, effectively reducing the impedance of the path. This can enhance the power transfer capability of the system, thereby improving steady state stability.

Question 15

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

Accepted Answer

Transposition of both power and communication lines helps in minimizing inductive interference by averaging out the effects of electromagnetic fields over the length of the lines, thus reducing the net inductive coupling between them.

Question 16

The power loss is an important factor for the design of
A)transmission line
B)motor
C)generator
D)feeder

Accepted Answer

Power loss is an important factor in the design of transmission lines because it affects the efficiency of the system. The power loss is caused by the resistance of the conductors and the inductance of the line. The resistance of the conductors causes the current to flow through the line to be reduced, which in turn reduces the power that is transmitted. The inductance of the line causes the current to lag behind the voltage, which also reduces the power that is transmitted.

Question 17

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

Accepted Answer

A fuse is connected in series with the circuit to ensure that the entire current flowing through the circuit passes through the fuse. This allows the fuse to blow and open the circuit if the current exceeds a safe level.

Question 18

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

Accepted Answer

H.R.C. (High Rupturing Capacity) fuses have no ageing effect, operate at high speeds, and have a high rupturing capacity, making all of the provided options correct.

Question 19

The fuse rating is expressed in terms of
A)current
B)voltage
C)VAR
D)kVA

Accepted Answer

The fuse rating is expressed in terms of current, indicating the maximum current the fuse can safely carry before blowing or breaking the circuit.

Question 20

The fuse blows off by
A)burning
B)arcing
C)melting
D)none of the above

Accepted Answer

Fuses are designed to protect electrical circuits by melting when they experience an overload or short circuit, breaking the circuit and stopping the flow of electricity to prevent damage or fire.

Quiz 4: Electrical Protection and Circuit Breakers

Which of the following circuit breakers has high reliability and minimum maintenance ?

Arc in a circuit breaker is interrupted at

transmission line has reflection coefficient as one.

What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ?

The inverse definite mean time relays are used for over current and earth fault protection of transformer against

Over voltage protection is recommended for

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

Overfluxing protection is recommended for

Series capacitors are used to

Admittance relay is _______ relay.

The material used for fuse must have

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

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

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

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

The power loss is an important factor for the design of

A fuse is connected

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

The fuse rating is expressed in terms of

The fuse blows off by