Deck 3: Power System Protection and Equipment

Question 1

Which of the following statements is incorrect?

A)Station batteries are used to operate relay only
B)The lightning arresters are basically surge diverters
C)An impedance relay has maximum fault current when fault occurs near the relay
D)A high speed relay has an operation of 1 to 2 cycles

Answer 1

Station batteries are used to operate relay only

Question 2

Discrimination between main and back up protection is provided by the use of relays which are

A)fact
B)sensitive
C)slow
D)none of the above

Answer 2

slow

Question 3

Induction cup relay is operated due to changes in

A)current
B)voltage
C)impedance
D)all of the above

Answer 3

all of the above

Question 4

A.C. network analyser is used to solve problems of

A)load flow
B)load flow and short-circuit
C)load flow and stability
D)load flow, short-circuit and stability

Question 5

Which of the following statements is incorrect ?

A)Lightning arrestors are used before the switchgear
B)Shunt reactors are used as compensation reactors
C)The peak short current is (1.8 xV2) times the A.C. component
D)The MVA at fault is equal to base MVA divided by per unit equivalent fault

Question 6

To reduce short circuit fault currents are used.

A)reactors
B)resistors
C)capacitors
D)none of the above

Question 7

Bus coupler is very essential in arrangement

A)single bus
B)double bus, double breaker
C)main and transfer bus
D)all of the above

Question 8

For cost and safety, the outdoor substations are installed for voltages above

A)11 kV
B)33 kV
C)60kV
D)110kV

Question 9

The short circuit in any winding of the transformer is the result of

A)mechanical vibration
B)insulation failure
C)loose connection
D)impulse voltage

Question 10

relays are used for phase faults on long line.

A)Impedance
B)Reactance
C)Either of the above
D)None of the above

Question 11

For which of the following protection from negative sequence currents is provided ?

A)Generators
B)Motors
C)Transmission line
D)Transformers

Question 12

relay is preferred for phase fault on short transmission line.

A)Induction type
B)Reactance
C)Impedance
D)None of the above

Question 13

Distance relays are generally

A)split-phase relays
B)reactance relays
C)impedance relays
D)none of the above

Question 14

For which of the following ratings of the transformer differential protection is recommended ?

A)above 30 kVA.
B)equal to and above 5 MVA
C)equal to and above 25 MVA
D)none of the above

Question 15

A _______ is used to measure the stator % winding temperature of the generator.

A)thermocouple
B)pyrometer
C)resistance thermometer
D)thermometer

Question 16

The relay with inverse time characteristic will operate within

A)1.5 sec
B)5 to 10 sec
C)5 to 20 sec
D)20 to 30 sec

Question 17

The single phasing relays are used for the protection of

A)single phase motors only
B)two phase motors only
C)two single phase motors running in parallel
D)three phase motors

Question 18

Which of the following devices will receive voltage surge first travelling on the transmission line ?

A)Lightning arresters
B)Relays
C)Step-down transformer
D)Switchgear

Question 19

Which of the following parameter can be neglected for a short line ?

A)Inductance
B)Capacitance
C)Resistance
D)Reactance

Question 20

Series reactors should have

A)low resistance
B)high resistance
C)low impedance
D)high impedance

Question 21

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

Question 22

Arc in a circuit breaker is interrupted at

A)zero current
B)maximum current
C)minimum voltage
D)maximum voltage

Question 23

transmission line has reflection coefficient as one.

A)Open circuit
B)Short-circuit
C)Long
D)None of the above

Question 24

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

Question 25

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