Switchgear and protection. Part – 4

31. The normal current in power line is 100A. If a short-circuit fault occurs on the line, then one can expect the short-circuit current to be

A. 200 A       

B. 300 A

C. More than 1000 A

D. 100 A

32. A short circuit between one line and ground, very often caused by physical contact is known as

A. Single line-to-ground fault

B. Line-to-line fault

C. Double line-to-ground fault

D. None of the above

33. Merz-price circulating current principles is more suitable for

A. Generators                 

B. Transformers

C. Both a and b

D. None of the above

34. In the following bus active and reactive powers are not specified

A. Load bus

B. Generator bus

C. Slack bus

D. None of the above

35. If the fault current is 2000A, the relay setting 50% and C.T. Ratio is 400/5, the plug setting multiplier will be

A. 15

B. 10

C. 25

D. 50

36. A low oil circuit breaker has the following advantage over a bulk oil circuit breaker

A. It requires a small space

B. The degree of carbonization is increased

C. Maintenance problems are increased

D. None of the above

37. If the percentage reactance of the system up to the fault point is 20% and base KVA is 10000, then short-circuit KVA is

A. 10000KVA

B. 50000KVA

C. 500KVA

D. 30000KVA

38. The time-current graph of a fuse

A. Has linear characteristic

B. Is a circle

C. Has inverse characteristic

D. None of the above

39. The medium used for arc extinction in ABCB is

A. Oil

B. Air

C. SF₆

D. Vacuum

40. Which of the following relays is used on long transmission lines?

A. Impedance relay

B. Mho’s relay

C. Reactance relay

D. None of the above 

Switchgear and protection. Part – 3

21. An isolator is designed to open a circuit under

A. Full-load

B. Normal condition

C. No-load

D. None of the above

22. The operating time of a fuse is about

A. 0.002 sec

B. 1 sec

C. 0.8 sec

D. 1.5 sec

23. The transient stability limit of a power system can be appreciably increased by introducing

A. Series inductance

B. Shunt inductance

C. Series capacitance

D. Shunt capacitance

24. In a bulk oil circuit breaker, the oil actually used for arc extinction is about

A. 60% of total

B. 40% of total

C. 90% of total

D. 10% of total

25. When a line-to-ground fault occurs, the current in the faulted phase is 100A. The zero sequence current in this case is

A. 33.3 A

B. Zero

C. 66.6 A

D. 100 A

26. Under dry conditions, the resistance offered by the human body may be as high as

A. 200 Ω

B. 100 Ω

C. 100000 Ω

D. 250 Ω

27. An over current relay having current setting of 125% is connected to a supply circuit through a current transformer of 400/5A. The pick-up current is

A. 6.25A

B. 12.55A

C. 3.125A

D. 25A

28. The arc voltage in a circuit breaker

A. Is in phase with arc current

B. Lags arc current by 90⁰

C. Leads arc current by 90⁰

D. Lags arc current by 180⁰

29. A circuit breaker is a

A. Current controlling device

B. Circuit interrupting device

C. Current limiting device

D. None of the above

30. The following contact is largely used for low-voltage oil circuit breaker

A. Tulip type contacts

B. Finger and wedge contacts

C. Butt contact

D. None of the above 

Switchgear and protection. Part – 2

11. What type of back up protection is used for alternators?

A. IDMT relay

B. Buchholz relay

C. Mho relay

D. Impedance relay

12. Current chopping mainly occurs in

A. Air blast circuit breaker

B. Vacuum circuit breaker

C. SF₆ circuit breaker

D. Oil circuit breaker

13. Peterson coil is used in case of transmission line for

A. Reduce ferranti effect

B. Compensating of arcing grounds

C. Improve power factor

D. Increase the voltage level

14. In routine tests, the cable is tested by applying an ac voltage of

A. 2 times the rated value

B. 2.5 times the rated value

C. 3 times the rated value

D. 3.5 times the rated value

15. What is the actuating quantity for the relays?

A. Magnitude

B. Frequency                     

C. Phase angle

D. All of these

16. Plug setting of a relay can be altered by varying

A. Air gap of magnetic path

B. No. Of ampere-turns

C. Adjustable back up stop

D. None of these

17. For load flow studies, what are the quantities specified at load bus are

A. P and V

B. P and Q

C. V and δ

D. δ and Q

18. The unit protection scheme provides

A. Simultaneous protection

B. Back up protection

C. Remote protection

D. Primary protection

19. For a fault at the terminals of a synchronous generator, the fault current is maximum for

A. Line to line fault

B. Line to ground fault

C. 3 phase to ground fault

D. 3 phase fault

20. A circuit breaker, under normal conditions, should be inspected

A. every day

B. every week

C. every month

D. once in 6 months or 12 months

Switchgear and protection. Part – 1

1. Material suitable for manufacturing of fuse wire is

A. Copper

B. Silver

C. Zinc         

D. Aluminum 

2. For protection of parallel feeder fed from one end, the relay required are

A. Non directional relay source end, directional relay at load end

B. Non directional relay at both end

C. Directional relay at source end, non directional relay at load end

D. Directional relay at both end

3. Merz price protection is employed for protection at

A. Alternators

B. Transformer

C. transmission line

D. both A and B

4. The rating of fuse wire is always expressed in

A. Volts

B. Ampere

C. Ampere volt

D. Ampere hour

5. The most efficient torque producing actuating for induction type relay is

A. Shaded pole structure

B. Watt hour meter structure

C. Induction cup structure

D. Single induction loop structure

6. Zero-sequence fault current is absent when fault is

A. Single line to ground

B. Line to line to ground

C. Line to line fault

D. Line to line to line to ground

7. The circuit breaker is widely used for __

A. Make and break the circuit

B. To make circuit

C. To break circuit

D. To provide protection against lightning surge

8. For internal faults in generator the primary protection is provided by

A. Earth fault relay

B. Differential relay

C. Induction type inverse definite minimum time relay

D. Definite minimum time relay

9. For a normal wire, the approximate value of fusing current is given by

A. 1 = K(d)^3/2

B. 1 = K(d)³

C. 1 = K(d)^3/4

D. 1 = (Kd)^3/2

10. The rate of rise of restricting voltage (RRRV) depends upon the

A. Inductance and capacitance of the system

B. Capacitance of system

C. Inductance of system

D. Type of CB