This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “FACTS Controllers – Set 3”.
1. MOSFET has no switching loss while BJT has.
a) True
b) False
View Answer
Explanation: Both MOSFET and BJT have individual switching losses as they are practical switches. As referred to BJT, MOSFET has higher switching losses. Conversely we can say that as referred to MOSFET, BJT has lower switching losses.
2. MOSFET has no conduction loss while BJT has.
a) True
b) False
View Answer
Explanation: Both MOSFET and BJT have individual conduction losses as they are practical switches. As referred to MOSFET, BJT has higher conduction losses. While conducting MOSFET exhibits less power loss than BJT.
3. Both MOSFET and BJT have same controlling mechanism.
a) True
b) False
View Answer
Explanation: MOSFET and BJT DO NOT have same controlling mechanism. For BJT the control is done with a voltage pulse at the base terminal. For MOSFET, the control is done with current pulse at the gate terminal.
4. Both MOSFET and BJT have same temperature coefficient of resistance.
a) True
b) False
View Answer
Explanation: MOSFET and BJT DO NOT have same temperature coefficient. MOSFET has negative temperature coefficient of resistance. BJT has positive temperature coefficient of resistance.
5. In electrical system, FACTS is a power-electronics based system.
a) True
b) False
View Answer
Explanation: It is true that in electrical system, FACTS is a power-electronics based system. The underlying reason behind this statement is that unlike large rotating machines being used as synchronous condensers or switched capacitor banks to compensate for reactive power; FACTS employs static equipment, AR compensators controlled by power electronic devices like thyristors for making up or taking away reactive power. This results in smooth control of reactive power and ultimate maintenance of a good voltage profile in the power system.
6. All the HVDC schemes are based on thyristors but with no gate tum-off capability.
a) True
b) False
View Answer
Explanation: Practically speaking, all the HVDC schemes are basically based on thyristors with no gate turn-off capability. Fundamentally they employ 12-pulse converters, which can function either as a voltage-controlled rectifier (ac to dc) or as inverter (dc to ac). The voltage control can be achieved from maximum positive to maximum negative, keeping the current flowing in the same direction. Thus reversal of power flow can be achieved with reversal of voltage only keeping unidirectional current. Such converters are termed current-sourced converters and are more economical for large HVDC schemes but are also useful in FACTS technology.
7. The most vital function to suppress SSR is removal of the dc bias of the series capacitor.
a) True
b) False
View Answer
Explanation: The most vital function to suppress SSR is removal of the dc bias of the series capacitor. This is because this dc charge provides the energy for feeding the sub-synchronous oscillations in the system. It may also result in high over-voltages across the series capacitor.
8. The circuit configuration of TCSC is similar to that of breaker-switched capacitors, reactors and mechanical tap-changing transformers.
a) True
b) False
View Answer
Explanation: The circuit configuration of TCSC is similar to that of breaker-switched capacitors, reactors and mechanical tap-changing transformers. It appears so because the TCSC employs reactive impedances and conventional thyristor valves (switches) as controlled elements. However, the TCSC exhibits much faster response and sophisticated operation controls than the later.
9. A FACTS Controller never has high power ac switches in its assembly.
a) True
b) False
View Answer
Explanation: “A FACTS Controller never has high power ac switches in its assembly” – is a false statement. Structurally, FACTS Controllers constitute an assembly with required combination of ac-to-dc converters, dc-to-ac converters and even high power ac switches. FACTS applications exhibit a three-phase power rating ranging from tens to hundreds of megawatts.
10. The ac switches employed in FACTS controllers are assemblies of ________
a) back-to-back connected power devices
b) loosely connected power devices
c) unconnected power devices
d) decoupled power devices
View Answer
Explanation: The ac switches employed in FACTS controllers are assemblies of back-to-back connected power devices. Along with them are present the requisite snubber circuits for the power devices and essential gate drive circuits, as designed. The turning-on and turning-off capabilities of the chosen gate drives play a vital role in the functioning of the FACTS controllers.
11. A FACTS Converter is a single-element device.
a) True
b) False
View Answer
Explanation: A FACTS Converter is NEVER a single-element device. A converter structure may be considered as an assembly of valves connected with other equipments. Again each valve consists of a group of assembled power devices. These power devices, in turn, require snubber circuits and drive circuits for their proper functioning.
12. The core of the technology of FACTS is power semiconductor devices.
a) True
b) False
View Answer
Explanation: The core of the technology of FACTS is power semiconductor devices. This is because high-power electronic devices (unlike signal semiconductor devices of low power rating) with a variety of switching characteristics are employed for faster FACTS Controller response. These faster switching capabilities help to exhibit less snubber elements, minimal gate-drive circuits, lower power losses and fewer harmonics as designed.
13. FACTS controllers do not require diodes for their operation.
a) True
b) False
View Answer
Explanation: FACTS controllers do require diodes for their proper functioning. This is because the FACTS devices may be controlled to turn on and turn off the current flow in their forward-conducting direction by means of gate control but some power devices are designed without the capability to block in reverse direction. In the later case those deices are connected with another reverse blocking device in series (which is a diode) or they may be bypassed in the reverse direction by another parallel device (which is also a diode). The diode is thus an indispensible component for several FACTS Controllers.
14. Generally transistors exhibit ________ switching performance than thyristors.
a) superior
b) inferior
c) same
d) different
View Answer
Explanation: Generally transistors exhibit superior switching performance than thyristors. Transistors demonstrate faster switching characteristics than thyristors. Transistors also pose lower switching losses than thyristors.
15. Thyristors have ________ as compared with transistors.
a) lower on-state conduction losses
b) lower off-state conduction losses
c) higher on-state conduction losses
d) higher off-state conduction losses
View Answer
Explanation: Thyristors have lower on-state conduction losses as compared with transistors. Also thyristors reveal higher power handling capability than transistors. Power devices with low on-state conduction losses and switching losses and with increased power handling capability are always desirable and so fetched for relevant applications.
Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).
To practice all areas of Flexible AC Transmission System (FACTS), here is complete set of 1000+ Multiple Choice Questions and Answers.
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