This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “GCSC, TSSC and TCSC”.
1. TCSC is an acronym for ________
a) Thermistor Controlled Series Capacitor
b) Thyristor Controlled Shunt Capacitor
c) Thyristor Controlled Series Capacitor
d) Thevenin Controlled Series Capacitor
View Answer
Explanation: TCSC is an acronym for Thyristor Controlled Series Capacitor. Its modes of operation are Bypassed thyristor mode, Blocked thyristor mode, Partially conducting thyristor (capacitive-Vernier or inductive-Vernier) mode. As the operation of a thyristor is controlled by its triggering, functionally it should be connected in series to the capacitor bank to achieve the smooth switching of the later.
2. TSSC is an acronym for ________
a) Thermistor Switched Series Capacitor
b) Thyristor Switched Shunt Capacitor
c) Thyristor Switched Series Capacitor
d) Thevenin Switched Series Capacitor
View Answer
Explanation: TSSC is an acronym for Thyristor Switched Series Capacitor. It consists of a number of capacitors in series. Here each capacitor is individually shunted by an appropriately rated bypass valve which comprises of a string of reverse parallel connected thyristors.
3. GCSC is the abbreviation of ________
a) GTO-Thyristor Controlled Series Capacitor
b) General Thyristor Controlled Series Capacitor
c) Gibbs Thyristor-Controlled Series Capacitor
d) Giant Thyristor-Controlled Series Capacitor
View Answer
Explanation: GCSC is the abbreviation of GTO-Thyristor Controlled Series Capacitor. This device has the flexibility to use the thyristor in its different modes of operation to control the series capacitor. Therefore, GCSC exhibits smart series compensation when connected to a transmission line.
4. Which is not the mode of operation of a Thyristor Controlled Series Capacitor (TCSC)?
a) Bypassed thyristor mode
b) Unblocked thyristor mode
c) Partially conducting thyristor (capacitive-Vernier) mode
d) Partially conducting thyristor (inductive-Vernier) mode
View Answer
Explanation: There are four different modes of operation of a Thyristor Controlled Series Capacitor (TCSC), namely bypassed thyristor mode, blocked thyristor mode, partially conducting thyristor (capacitive-Vernier) mode and partially conducting thyristor(inductive-Vernier) mode. In blocked thyristor mode of operation, the thyristor is not triggered and the TCSC operates in blocking mode. In this case TCSC performs simply as a fixed series capacitor.
5. While analyzing a Thyristor Controlled Series Capacitor (TCSC), which of the following is not a technique of its modeling?
a) Transient stability model
b) Long term stability model
c) Variable reactance model
d) Modeling for asynchronous resonance SSR studies
View Answer
Explanation: There are four models of Thyristor Controlled Series Capacitor (TCSC), namely transient stability model, long term stability model, variable reactance model and modeling for sub-synchronous resonance SSR studies. SSR refers to the condition where one or more of the resonant frequencies of the turbine generator shaft in thermal power units coincides with that of the series capacitor resulting in torsional oscillations and torque deforming the shaft. Unlike the fixed series capacitor this TCSC model compensates with the damping or removal of SSR Torque.
6. TCSC is an example of VSC FACTS controller.
a) True
b) False
View Answer
Explanation: Thyristor controlled series compensator is an example of variable impedance type FACTS controller. It is not a voltage source FACTS controller. As the name suggests, TCSC is basically a series-connected controller and not a shunt-connected one.
7. TCSC is exactly similar to GCSC.
a) True
b) False
View Answer
Explanation: The circuitry of TCSC may seem similar to the circuit structure of the GCSC from the appearance of the circuits. But their operational functionalities are different. GCSC is sequentially operated and the operation of TCSC is different from it due to the imposed switching restrictions of the conventional thyristor valve employed in it.
8. Which of the following FACTS device has the capability to turn on and off upon command?
a) Neither GCSC nor TCSC
b) Either GCSC or TCSC
c) GCSC
d) TCSC
View Answer
Explanation: Among the given FACTS devices, GCSC has the capability to turn on and off upon command. This is because GTOs are incorporated in GCSC while conventional thyristors are employed in TCSC. By its inherent property, GTO gives the flexibility of switching on or off the required capacitor by turning on or off its gate as per the command.
9. TCR is the ________ of GCSC.
a) dual
b) inverse
c) equal
d) reverse
View Answer
Explanation: TCR is the dual of GCSC. The wave shape followed by the current of the thyristor-controlled reactor is identical to that for the voltage GTO thyristor-controlled series capacitor. This confirms the duality between the TCR and the GCSC.
10. Choose the right option among the alternatives – The GCSC is controlled by a turn-on/turn-off delay with respect to the peak of the applied voltage/line current.
a) Turn-on, applied voltage
b) Turn-on, line current
c) Turn-off, applied voltage
d) Turn-off, line current
View Answer
Explanation: The GCSC is controlled by a turn-off delay with respect to the peak of the line current. The GCSC controls the voltage generated by a constant current source across a fixed capacitor. Therefore, GCSC presents variable reactive impedance to this source.
11. A turn-off delay with respect to the peak of the line current applied to the GCSC manifests the ________ interval/condition of the switch in the FACT controller.
a) blocking
b) conduction
c) by-passing
d) short-circuiting
View Answer
Explanation: The GCSC is, in fact, a switch in shunt with a capacitor. A turn-off delay with respect to the peak of the line current applied to the GCSC manifests the blocking interval/condition of the switch in the FACT controller. The GCSC is designed to close at zero voltage.
12. A transmission line acts as a ________ to the GCSC incorporated.
a) current source
b) voltage source
c) no-load source
d) full-load source
View Answer
Explanation: A transmission line acts as a current source to the GCSC incorporated. This is so because GCSC is fed from the transmission line current. The GCSC controls the voltage developed by a constant current source across a fixed capacitor.
13. A transmission line sees a GCSC connected to it as ________ to it.
a) variable reactive impedance
b) variable reactive admittance
c) constant reactive impedance
d) constant reactive admittance
View Answer
Explanation: A transmission line sees a GCSC connected to it as variable reactive impedance to it. It cannot be of a constant value because the GCSC switch is sequentially controlled and is turned off and on as per the command. The resultant is that it is poses reactive impedance which varies accordingly with the switching on and off the GTOs.
14. A TSSC may cause sub-synchronous resonance.
a) True
b) False
View Answer
Explanation: By virtue of its inherent property, a TSSC does control the degree of series compensation by either inserting or by-passing series capacitors in operation. But it is dictated by the natural characteristic of the capacitor. This follows that a sufficiently high degree of TSSC compensation can cause sub-synchronous resonance just like an ordinary capacitor.
15. The TSSC ________ made to counteract sub-synchronous oscillations effectively by modulating its switching.
a) can be
b) cannot be
c) is always
d) may or may not be
View Answer
Explanation: Theoretically it may seem that the TSSC switching can be modulated to counteract sub-synchronous oscillations. But practically, except for the very low end of the sub-synchronous frequency band, this is not possible because of the relatively long switching delays encountered, which is likely to make the modulation ineffective. Therefore, the ‘pure TSSC scheme’ should not be implemented in critical applications where a high degree of compensation is required and the danger of sub-synchronous resonance is present.
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.
If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]
