EHV AC & DC TRANSMISSION MCQ Unit - 4

 

Unit-4 (EHV DC Transmission – I)

1. Which of the following are pros of HVDC over AC:

1.     Absence of Capacitance

2.     Absence of inductance

3.     Absence of phase displacement

4.     All of these

Ans . All of these

2. VSC Converters use:

1.     Thyristors

2.     Mercury arc valves

3.     Transistors

4.     All of these

Ans. Transistors

3. Generally the Converter transformers used in VSC HVDC systems are _ as compare to LCC HVDC systems:

1.     Complex

2.     Simple

3.     Identical

Ans . Simple

4.     Symmetrical monopole converters are earthed with impedance:

1.     Zero

2.     Low

3.     Medium

4.     High

Ans. Low

 

5.  In HVDC transmission system, rectifier firing angle a is kept near

(a) 0°

(b) 15°

(c) 30⁰

(d) 90⁰ 

Ans:-C

6.  If firing angle in an SCR circuit is increased, the output …………

a)     Remains the same

b)     Is increased

c)     Is decreased

d)     None of the above

Answer : c

 

7.  A single-phase two pulse converter feeds RL load with a sufficient smoothing such that the load current does not fall to zero. If the resistance of the load circuit is increased then the

a)  ripple content is not affected

b)  ripple content of current increases

c)  ripple content of current decreases

d)  load current may fall to zero 

Answer: b

 

8.  In case of controlled rectifiers, the nature of the load current (continues or discontinuous) depends upon the

a)  type of load and firing angle

b)  only on the type of load

c)  only on the firing angle

d)  it is independent of all the parameters 

Answer: a

 

9.  In a single phase full converter, for discontinuous load current and extinction angle β > π, each SCR conducts for

     a)  α

b)  β

c)  β-α

d)  β+α Answer: c