(FACTS) meaning Flexible Alternating Current Transmission System or Flexible AC Transmission is a system. This system is composed of static equipment. It is utilized for electrical energy’s transmission AC. It is supposed for enhancing power transfer capabilities and increasing controllability of network. It is power electronic based system generally. FACTS as defined by IEEE are that it is system based on power electronics and different static equipment. It has provision of controlling one or more than one system parameters of AC transmission. It does enhancement of controllability and increasing maximization of power transfer capabilities. FACTS as stated and defined by Siemens are that FACTS increases AC grid’s reliability. This reduces cost of power delivery. This improves power transmission efficiency and quality of transmission. This is by supplying reactive or inductive powers to grids.
Technology: Series compensation: In this series compensation, FACTS are connected with power system in series. It works as voltage controllable source. Inductance series exist in all transmission AC lines. In long lines, when large current flows, then that causes large voltage drops. Capacitors in series are connected for compensation. This decreases inductance effects. By connection of series capacitors being in series with lines, inductive reactance in between sending end and receiving end is reduced. By this system’s power factor is improved. But effects on power factor are too much little as compared with shunt capacitor. Shunt compensation: In this shunt compensation, FACTS are connected with power system in shunt (parallel). This works as controllable sources of current. There are 2 types of shunt compensation: Shunt capacitive compensation: This way has been used for improving power factors. Whenever inductive loads are connected to transmission lines, there is lagging of power factor due to lags in load currents. For compensating this, shunt capacitors are connected. It draws currents being led by source voltages. Net result is power factor improvement. Shunt inductive compensation: This way is either used when transmission line is charged or when low loads are there at receiving end. Since, there is no load or very low load, so very less current flow through transmission lines. Shunt capacitance in transmission lines cause amplification of voltage. This is called Ferranti Effect. Receiving end voltages becomes double of sending end voltage. This is case generally in too much long transmission lines. For compensating this, shunt inductors have been connected through transmission lines. Power transfer capabilities are increased thereby whilst depending on power equations.
Series compensation examples: There is (SSSC) Static synchronous series compensator. There has to be (TCSC) Thyristor-controlled series capacitor: This is where series capacitor banks are shunted by thyristor-controlled reactors. There has to be (TCSR) Thyristor-controlled series reactor: This is where series reactor banks are shunted by thyristor-controlled reactors. There has to be (TCSC) Thyristor-controlled series capacitor: This is where series capacitor banks are shunted by thyristor-controlled reactors. There has to be (TSSC) Thyristor-switched series capacitor: This is where series capacitor banks are shunted by thyristor-switched reactor. There has to be (TSSR) Thyristor-switched series reactor: This is where series reactor banks are shunted by thyristor-switched reactor. Shunt compensation examples: There is (STATCOM) Static synchronous compensator. This was called previously static condenser (STATCON). There has to be (SVC) Static VAR compensator. Common SVC is: (TCR) Thyristor-controlled reactor: This is reactor in series connected with thyristor bidirectional valve. Thyristor valve is controlled by phases. Reactance equivalent is continuously varied. (TSR) Thyristor-switched reactor: It is similar to TCR. But thyristor is in full or zero conduction. Reactance equivalent is in stepwise way varied.
(TSC) Thyristor-switched capacitor: This is capacitor in series connected with thyristor bidirectional valve. But thyristor is in full or zero conduction. Reactance equivalent is in stepwise way varied.