This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “Controllable Parameters of AC Transmission System – 1”.
1. Which power system has the improved power transfer capability?
a) Flexible AC Transmission System
b) Conventional AC Transmission System
c) Inflexible AC Transmission System
d) Unconventional AC Transmission System
View Answer
Explanation: In Electrical Engineering, Flexible AC Transmission System or Flexible Alternating Current Transmission System [FACTS] exhibits improved power transfer capability as compared with Conventional AC Transmission System. This is because Conventional AC Transmission System is characterized by various static and dynamic limits such as transient stability, voltage stability, thermal limits and others; leading to the inefficient utilization of existing power transmission resources. On the other hand FACTS incorporates the power electronic devices to manage the active and reactive power more smartly and efficiently, thereby, improving power transfer capability of the power transmission system.
2. SSR is the abbreviation of ________
a) Sub Synchronous Resonance
b) Sub Synchronous Reactor
c) Sub Synchronous Resistance
d) Sub Synchronous Resistor
View Answer
Explanation: SSR is the abbreviation of Sub Synchronous Resonance. The high-speed, high-power FACTS controllers are potentially able to enhance or degrade this phenomenon of sub-synchronous resonance. Hence SSR is a topic of great importance in the application of FACTS.
3. The parameter/parameters that affect the operation of a transmission system is/are________
a) only series impedance
b) only shunt impedance
c) only phase angle
d) series impedance, shunt impedance, phase angle, etc.
View Answer
Explanation: The transmission systems is characterized by its interrelated parameters like series impedance, shunt impedance, current, voltage, phase angle, the damping of oscillations at various frequencies below the rated frequency, etc. These parameters do affect the operation of a transmission system. For both dynamic and steady-state operation, the parameters of the transmission system should be controlled.
4. A transmission system is a lumped network.
a) True
b) False
View Answer
Explanation: An electrical power transmission system is basically a distributed system of network and NOT a lumped one. This is because the inductance and capacitance of transmission lines are distributed throughout their lengths. The inductance or capacitance of the whole transmission line cannot be assumed to be lumped at a particular point in them, due to transit time effect. Hence, they cannot be considered as a lumped network.
5. Kirchoff’s laws can be applied to transmission system as a whole.
a) True
b) False
View Answer
Explanation: Kirchoff’s laws CANNOT be applied to a transmission system as a whole. This is because Kirchoff’s laws, by its own limit, can only be applied to lumped networks. An electrical power transmission system, as a whole, is a distributed one and hence their inductance and capacitance cannot be assumed to be of lumped nature due to transit time effect.
6. Match the following.
| Parameters of Transmission Line | Measuring Units |
|---|---|
| 1] Capacitance | A] mho/meter |
| 2] Inductance | B] henry/meter |
| 3] Conductance | C] ohm/meter |
| 4] Resistance | D] farad/meter |
a) 1-A
b) 2-B, 3-A
c) 2-B
d) 3-C, 4-C
View Answer
Explanation: In transmission system, the parameters are distributed due to transit time effect and are measured in per unit length.
| Parameters of Transmission Line | Measuring Units |
|---|---|
| Capacitance | farad/meter |
| Inductance | henry/meter |
| Conductance (leakage) | mho/meter |
| Resistance | ohm/meter |
7. In the following figure, what are the parameters that can be controlled to enhance power flow through the transmission system?
a) Only V
b) Only δ
c) Only X
d) V, δ, X
View Answer
Explanation: To enhance the power flow through the transmission system given in the figure, the parameters that can be controlled include voltage V, impedance X and load angle δ. It is important to note that enhancing power flow encircles both active and reactive power of the system. Thus FACTS devices by utilizing their inherent property can enhance the controllability and improve the power flow or transfer capability of a transmission system.
8. The stability problem that a power transmission system may face, is/are ________
a) transient stability only
b) dynamic stability only
c) steady-state stability only
d) transient stability, dynamic stability and steady-state stability
View Answer
Explanation: The stability problem that a power transmission system may face, are transient stability, dynamic stability and steady-state stability. Accordingly a FACTS device can be chosen to mitigate the issues related to various stabilities and increase effectively the stability of the system as required. So series, shunt and other types of compensations are employed through FACTS.
9. Which of the following disturbances are faced by a power transmission system?
a) Frequency collapse only
b) Voltage collapse only
c) Sub synchronous reactance only
d) Frequency collapse, voltage collapse and SSR
View Answer
Explanation: Frequency collapse, voltage collapse and sub synchronous reactance are the disturbances that may be faced by a power transmission system. The FACTS devices incorporated in a power transmission system can mitigate the issues effectively. Accordingly FACTS delivering series compensation, shunt compensation or others are of huge importance in enhancing the power transfer capability of a power transmission system.
10. What does SPST switch mean?
a) Single Pole Single Throw
b) Single Pole Single Thyristor
c) Single Pole Single Thermostat
d) Single Pole Single Transistor
View Answer
Explanation: SPST switch means Single Pole Single Throw switch. A semiconductor power device can behave in the configuration of SPST. It exhibits defined polarities of voltages and currents in its diagram.
11. Electronic switches exhibited by semiconductor switches can operate in______
a) single quadrant
b) single, double, triple or four quadrants
c) single, double or four quadrants
d) four quadrant
View Answer
Explanation: Electronic switches exhibited by semiconductor switches can operate in single, double or four quadrants. It depends upon the requirement of the circuit and the components considered for switching. Accordingly we can choose diode, MOSFET, thyristor and other devices for configuring the required switches.
12. Electronic switches are all active switches.
a) True
b) False
View Answer
Explanation: All electronic switches are NOT active switches. These semiconductor switches can also be semi-active depending upon its mode of operation. Likewise the turning-off or turning-on of transition of a power electronic device can manipulate the same device to act as an active switch at one mode while a passive one in another mode.
13. Mechanical switches are all active switches.
a) True
b) False
View Answer
Explanation: Mechanical switches are NOT active switches. Mechanical switches are passive switches. This is because Mechanical switches are controlled by the voltage, current or both applied at their terminals. They are slow in operation with respect to electronic ones.
14. Silicon controlled rectifier is a passive switch.
a) True
b) False
View Answer
Explanation: Silicon controlled rectifier is a special type of switch. It acts as an active switch at one mode of operation while as a passive one in another mode. The modes of operation are, respectively, turning-on transition and turning-off transition of SCR.
15. Single-quadrant electronic switches are bipolar.
a) True
b) False
View Answer
Explanation: Single-quadrant electronic switches are NOT bipolar. They exhibit only two states, viz. on-state and off-state. They are unipolar for they can conduct current in one direction without damaging themselves, e.g. diodes, transistors, etc.
Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).
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