FACTS Controllers Questions and Answers – Set 2

This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “FACTS Controllers – Set 2”.

1. What are the parameters of the AC transmission system that a FACTS controller can control?
a) Voltage
b) Power
c) Impedance
d) Impedance, Voltage, Current, Power and Phase angle

Explanation: FACTS controllers provide control of one or more AC transmission parameters like Impedance, Voltage, Current, Power and Phase angle. FACTS controllers can be classified into four types. They are Series connected controllers, Shunt connected controllers, Combined series-series controllers and Combined shunt-series controllers.

2. FACTS controllers can inject ________
a) only current
b) only voltage
c) current or voltage
d) inertia

Explanation: FACTS controllers can inject current or voltage as per their characteristic features. The FACTS controller named static synchronous compensator (STATCOM) injects current. The FACTS controller named static series synchronous compensator (SSSC) injects voltage.

3. The output of Power Electronic devices can be ________
a) only variable ac voltage
b) only variable dc voltage
c) variable ac voltage or dc voltage
d) constant dc voltage

Explanation: The output of Power Electronic devices can be variable ac voltage or dc voltage. The output of Power Electronic devices may even be variable voltage and variable frequency. The Power devices with the desired characteristics as required are employed in FACTS.

4. The three transmission line operating parameters used to determine the transmitted power are voltage, impedance and angle.
a) True
b) False

Explanation: The three transmission line operating parameters used to determine the transmitted power are voltage, impedance and angle. FACTS controllers accordingly act on one or more of these parameters to achieve targeted transmission system compensation and mitigate control problems. The most noteworthy dissimilarity between the approaches availed by the FACTS controllers lies in the capability to generate reactive power and exchange real power.

5. The rating of a series FACT controller is ________ the throughput rating of a transmission line.
a) a multiple of
b) a major proportion of
c) a small fraction of
d) is equal to

Explanation: The rating of a series FACT controller is generally, a small fraction of the throughput rating of a transmission line to which it is connected. The underlying fact is that for variable series compensation, the nominal value is computed taking into consideration, about one-fourth of the throughput line rating or parameters and it results in a low power rating (say 5%) of the series FACT controller with respect to that of the throughput rating of the line. Thus the low rated series FACT controller can make a high control of power flow of the transmission network by simply controlling current flow by dint of controlling EL, X and ∂ of the transmission

6. TCSC can provide reactive compensation.
a) True
b) False

Explanation: TCSC can provide reactive compensation. This is because it is able to generate reactive power. However, TCSC cannot exchange real power (other than its own losses) when connected with the ac power system.

7. Fuses are used to protect FACTS controllers.
a) True
b) False

Explanation: Fuses are absolutely undesirable and NOT used to protect FACTS controllers. This is because FACTS controllers are associated with high-voltage applications. Accordingly the device selection must be done for FACTS considering all possible faults and providing protection upto permissible voltage/current limits.

8. Semiconductor devices for high power are generally fabricated using single crystal germanium wafers.
a) True
b) False

Explanation: Semiconductor devices for high power are NOT fabricated using single crystal germanium wafers. Generally single crystal silicon wafers are used to fabricate semiconductor devices for high. Silicon is readily available in the form of sand, unlike germanium.

9. On-state conduction losses in the power electronic devices may represent a high manufacturing cost.
a) True
b) False

Explanation: On-state conduction losses in the power electronic devices may represent a high manufacturing cost. This is because during full conducting state usually in the forward direction, forward-voltage drop occurs giving rise to consequent on-state losses. Losses in the form of heat are required to be rapidly removed from the silicon wafer. Ultimately the cooling medium removes that heat in lieu of an increased cost.

10. Corresponding high dv/dt during/after transition from a fully conducting to a fully non-conducting state is an important parameter to be looked into in FACTS devices.
a) True
b) False

Explanation: Corresponding high dv/dt during/after transition from a fully conducting to a fully non-conducting state is an important parameter to be looked into in FACTS devices. Accordingly snubber circuits requirement to soften high dv/dt during turning-off is dictated. This in turn, dictates the size, cost, losses, etc. of the FACTS devices.

11. While turning-on FACTS devices from a fully non-conducting state to a fully conducting state, corresponding high di/dt during this transition is an important parameter to be taken care of.
a) True
b) False

Explanation: While turning-on FACTS devices from a fully non-conducting state to a fully conducting state, corresponding high di/dt during this transition is an important parameter to be taken care of. Accordingly snubber circuits requirement to soften high di/dt during transistion is dictated. This in turn, dictates the useable device current and voltage rating of the FACTS devices.

12. The switching losses can contribute significantly to the total losses in converters.
a) True
b) False

Explanation: The switching losses can contribute significantly to the total losses in converters. Generally Power electronics employed in converters operate in cycles. Being repetitively switched on and switched off, they can contribute to switching losses which may contribute a significant part to the total losses in converters.

13. During turning-on or off of converters, the current and voltage do not change.
a) True
b) False

Explanation: During turning-on or off of converters, the current and voltage do change. Actually while turning-on, the forward current goes up before the forward voltage goes down. Again while turning-off the turn-off device the forward voltage rises before the current falls. These resulting existences of high voltage and current simultaneously in the converter contribute to power losses.

14. The gate-driver circuit contributes significantly to the total losses in converters.
a) True
b) False

Explanation: The gate-driver circuit contributes significantly to the total losses in converters. Actually converters may require gate-driver circuits to control their turning-on and/or turning-off. The gate-driver circuit may use large and long current/voltage pulses to achieve such goals with energy requirement contributing to the total losses in converters.

15. The gate-driver circuit contributes significantly to the total equipment cost of converters.
a) True
b) False

Explanation: The gate-driver circuit contributes significantly to the total equipment cost of converters. Actually the gate-driver circuits requiring large and long current/voltage pulses to control the turning-on and/or turning-off of converters demands sufficient energy requirement. The cost of the gate-driver circuit and its associated power supply contribute significantly to the total equipment cost of converters.

Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).

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