Unit-4: EHV DC Transmission – I
1. Which of the following are advantages of HVDC over AC?
- Absence of capacitance
- Absence of inductance
- Absence of phase displacement
- All of these
Answer: All of these
2. VSC Converters use:
- Thyristors
- Mercury arc valves
- Transistors
- All of these
Answer: Transistors
3. Generally, the converter transformers used in VSC HVDC systems are ______ as compared to LCC HVDC systems:
- Complex
- Simple
- Identical
Answer: Simple
4. Symmetrical monopole converters are earthed with impedance:
- Zero
- Low
- Medium
- High
Answer: Low
5. In HVDC transmission systems, the rectifier firing angle (α) is kept near:
- a) 0°
- b) 15°
- c) 30°
- d) 90°
Answer: c) 30°
6. If the firing angle in an SCR circuit is increased, the output:
- a) Remains the same
- b) Increases
- c) Decreases
- d) None of the above
Answer: c) Decreases
7. A single-phase two-pulse converter feeds an RL load with sufficient smoothing such that the load current does not fall to zero. If the resistance of the load circuit is increased, then:
- 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) Ripple content of current increases
8. In controlled rectifiers, the nature of the load current (continuous or discontinuous) depends on:
- a) Type of load and firing angle
- b) Only on the type of load
- c) Only on the firing angle
- d) Independent of all parameters
Answer: a) Type of load and firing angle
