Protection and Control

Question 1

A relay is used to

Answer 1

Sense the fault and direct to trip the circuit breaker.

Question 2

More faults occur in generators, underground cables, transformers, or overhead lines?

Answer 2

Overhead lines.

Question 3

A relay gets its operating energy from

Answer 3

Current transformer (CT), Voltage transformer (aka potential transformer, PT)

Question 4

A good relay should possess

Answer 4

Speed, reliability, aped, sensitivity, adequateness, selectivity.

Question 5

Relays for transmission line protection are in: 3 zones, 2 zones, independent of zone, non of the above?

Answer 5

3 zones.

Question 6

Protective relays are devices which detect abnormal conditions in electrical circuit by measuring

Answer 6

Constantly the electrical quantities which differ during normal and abnormal conditions

Question 7

Buchholz relay is used for the protection of

Answer 7

Transformers

Question 8

In a three-step distance protection the reach of the three zones of the relay at the beginning of the first line typically extends into

Answer 8

80% of the first line, 50% of the second lines and 20% of the third line.

Question 9

Power loss is an important factor in the design of: transmission lines, generators, motor, feeder?

Answer 9

Transmission lines

Question 10

What do protective relays provide? a) provide additional safety to the circuit breaker in its operation. b) Close the contacts when the actuating quantity attains a certain predetermined value. c) Limit the arcing current during the circuit breaker operation. d) Earth or ground any stray voltage.

Answer 10

Close the contacts when the actuating quantity attains a certain predetermined value.