High voltage direct current (HVDC) and High voltage engineering(HVE) MCQs Part-5

HVDC/HVE 

1. The break-even distance is the distance beyond which__________.

a. DC transmission is economical

b. AC transmission is economical

c.cost of both systems are the same

d.both (b) & (c)

 

2. In a bipolar system_______.

a. both conductors are positive

b.both conductors are negative

c.one conductor is positive & the other negative

d.one conductor is positive or negative & other is at ground potential

 

3. In a monopolar system, usually the pole is_____.

a. positive

b.negative

c. positive & negative

d. alternately positive & negative

 

4. Modern HVDC systems are all_____.

a. 3-pulse converters

b. 6-pulse converters

c. 12-pulse converters

d. 24-pulse converters

 

5. Short circuit ratio of an HVDC grid is_________.

a. DC power flow/kVA

b. ACMVA/DCMW

c. voltage/current at the short circuit point

d. short circuit MVA at converter bus rated DC power MW

 

6. The first HVDC scheme in INDIA is__________.

a. Vidhyachal back-to-back system

b. Chandrapur-Padghe scheme

c. Delhi-Rihand 500kV system

d. Sileru-Barsoor system

 

7. HVDC-VSC scheme employs_______.

a. IGBT valves

b. light or optically triggered thyristor valves

c. mercury arc valves

d. mosfETs & GTO valves

 

8. The main advantage of HVDC-VSC scheme is_______.

a. both active & reactive powers can be controlled

b. does not require DC filters

c. can be used for very high power, more than 1500MW

d.all the above

 

9. A thyristor valve conducts when_______.

a. anode is positive

b. anode is negative

c. anode is positive with positive gate pulse

d.anode is positive with negative gate pulse

 

10. A thyristor valve is fabricating using_______.

a. SCRs connected in series (all)

b. SCRs connected in parallel (all)

c. SCRs connected in series & parallel as modules

d. all the above

 

11. A 12-pulse converter are used in modern converters because of_______.

a. reduced current

b. reduced ripple

c. increased voltage & reduced harmonics

d.both (b) & (c)

 

12. A 12-pulse connection, transformers are connected_______.

a. Delta/Delta (both)

b. Star/star (both)

c. star/Delta (both)

d. one star/star & other star/Delta

 

13. IGBT converters operate on the principle of_______.

a. voltage source converter

b. current source converter

c. power source converter

d. either (a) or (b)

 

14. IGBT requires_________.

a. large current for triggering

b.large voltage pulse for triggering

c. sine wave voltage for triggering

d. anyone (a), (b) or (c)

 

15. Compared to SCRs, IGBT have_______.

a. more turn-on, turn-off time

b. less turn-on, turn-off time

c. both have some characteristics

d. turn-on, turn-off times can be more or less depending on the circuit

 

16. A pack in an IGBT valve comprises______.

a. triggering gate pulse circuit

b. parallel connect IGBTs

c. series & parallel connected IGNT's with projection

d.none of the above

 

15. Coolant used in thyristor/IGBT valves is_______.

a. Air

b.SF

c. Freon

d. Oxygen

 

16. A 12-pulse converter consists of_______.

a. two 6-pulse converters in series

b. two 6-pulse converters in parallel

c. (a) or (b)

d. (a) & (b) 

 

17. Power transfer through AC systems depends on_________.

a. sending & receiving end voltages

b. phase angle difference between sending end & receiving end voltages

c. reactance of the line

d. all the above

 

18. Power transfer through DC line depends on_______.

a. sending & receiving end voltages

b.number of pulses in the rectifier

c. line resistance

d.none of the above

 

19. Advantage of DC link for power transfer is_________.

a. easy controllability of power

b. more economical

c. it is an asynchronous tie

d. less insulation requirement

 

20. Control of DC power in a DC link is done by_______.

a. control

b. Y control

c. transformer tap changing

d. all the above