Deck 3: Electrical Substation Equipment and Protection Systems

Question 1

The line insulation is the insulation level of the station equipment.

A)less than
B)same as
C)more than
D)not directly related with

Answer 1

not directly related with

Question 2

The interaction between a transmission line and communication line is minimized by

A)transposing transmission as well as communication lines
B)increasing the height of the trans-mission line tower
C)increasing the distance between the two lines
D)all of the above

Answer 2

all of the above

Question 3

When a wave propagates on a transmission line, it suffers reflection several times at

A)tapping
B)load end
C)sending end
D)sending and other end

Answer 3

sending and other end

Question 4

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

Question 5

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

Question 6

Induction cup relay is operated due to changes in

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

Question 7

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 8

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 reactance

Question 9

Short-circuit currents are due to

A)single phase to ground faults
B)phase to phase faults
C)two phase to ground faults
D)any of these

Question 10

To reduce short circuit fault currents are used.

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

Question 11

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 12

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

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

Question 13

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 14

relays are used for phase faults on long line.

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

Question 15

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

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

Question 16

relay is preferred for phase fault on short transmission line.

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

Question 17

Distance relays are generally

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

Question 18

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 19

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

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

Question 20

The under voltage relay can be used for

A)generators
B)busbars
C)transformers
D)all of the above

Question 21

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 22

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 23

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 24

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

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

Question 25

Series reactors should have

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