Presented by:
V.RAMESH

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ABSTRACT
The philosophy of FACTS (Flexible AC Transmission Systems) is to use power electronic controlled devices to control power flow in transmission network to utilize to its full capacity.
FACTS are one of the best ways to reduce the need for construction of new over head transmission lines is to increase power flow over existing lines.
Due to high capital cost of erection of new transmission line we have improved this technology called FACTS. By using this technology we can improve the power transfer capability of the transmission line and these devices have high switching capacity even at high frequencies as these devices have no moving parts we can achieve high sensitivity and better control. There are many types of FACTS controller devices out of them TCSC (Thyristor Control Series Capacitor) has more advantages than other types
INTRODUCTION:
Without electricity, modern society would cease to function. As the volume of power transmitted and distributed increases, so do the requirements for a high quality and reliable supply. At the same time, rising costs and growing environmental concerns make the process of building new power transmission and distribution lines increasingly complicated and time-consuming. Making exciting lines as well as new ones more efficient and economical then become a compelling alternative. The purpose of the transmission network is to pool power plants and load centers in order to minimize the total power generation capacity and fuel cost. The power systems of today, by and large, are mechanically controlled. There is a wide spread use of microelectronics, computers and high-speed communications for control and protection of present transmission systems; however, when operating signals are sent to the power circuits, where the final power control action is taken, the switching devices are mechanical and there is little high-speed control. Another problem with mechanical devices is that control cannot be initiated frequently, because these mechanical devices tend to wear out very quickly compared to static devices. In India, for example there has been a fourfold increase in the value of wholesale transactions during the last decade. At the same time, however, addition of new transmission capacity to handle this growth has become increasingly difficult. Fortunately, a new generation of technologies promises to solve the growth-capacity dilemma by offering unconventional ways to increase transmission capacity with much less need for building new overhead lines. Today, one such technological area that has the potential to revolutionize utility transmission system is FLEXIBLE AC TRANSMISSION.FACTS devices are static equipment used for effective transmission. It means to enhance controllability and increase power transfer capability. It was introduced by Dr N.G.Hingorani in 1988 from the Electric Power Research Institute (EPRI) in the USA.
DEFINITION:
FACTS is defined by ‘IEEE’ as power electronic based system and other static equipment that provide control of one or more AC transmission system parameters to enhance controllability and power transfer capability.
Facts Portfolio
BASICS OF FACTS:
The main idea of FACTS can be explained by the basic equation of power transmission is shown in the below figure.Power transmitted between two nodes of the system depends on voltages at both ends of the interconnection. Different FAC TS devices can actively influence one or more of these parameters for power flow control and improvement of voltage stability at node of interconnection.Depending on the system configuration, the tasks of FACTS can be summarized as follows:
• Meshed systems & bulk power transmission can cause power flow control.
• Radial systems &parallel lines can cause impedance control.
• Weak systems can cause voltage control.
GENARATIONS OF CONTROLLERS:
FIRST GENERATION:This uses a simple logic of capacitance of manually based upon a roughly pre-manipulated data
SECOND GENERATION: The electronics makes its doubt here, forming a more smooth operation using relays and semi-conductor switches. This even did not eradicate the demerit of manual presence.
THIRD GENERATION: This uses FACTS devices to control the flow of power in the transmission line, and also increase the stability in transient conditions.
FACTS CONTROLLERS:
The power that can be transmitted over a line depends on three factors
1. Series reactance of the line
2. Bus voltages
3. Transmission angle 
 Voltage along the line can be controlled by reactance shunt compensation.
 Series line inductance can be controlled by series capacitive compensation.
 Transmission angle can be varied by phase shifting.
FACTS can be connected
1. In series with the power system.
2. In shunt with the power system.
3. Both in series and shunt with the power system.
SERIES COMPENSATION:
In series compensation FACTS are connected in series with power system. It works as a controllable voltage source
METHODS OF SERIES COMPENSATION:
• Static synchronous series compensator (SSSC)
• Thyristor controlled series capacitor (TCSC)
• Thyristor switched series capacitor (TSSC)
Static synchronous series compensator (SSSC)
As mentioned, Static Synchronous Series Compensator (SSSC) is placed in the group of series connected FACTS devices. SSSC consists of a voltage source inverter connected in series through a coupling transformer to the transmission line.
A source of energy is required for providing and maintaining the DC voltage across the DC capacitor and compensation of SSSC losses. Fig. 2 shows the model of SSSC which consists of a series connected voltage source in series with an impedance. This impedance represents the impedance of coupling transformer.
THYRISTOR CONTROLLED SERIES CAPACITOR TCSC)
The basic thyristor controlled series capacitor scheme proposed in 1986 by Vithayathil with others as a method of rapid adjustment of network impedance is shown in fig.It consists of the series compensating capacitor shunted by a thyristor-controlled reactor. In a practical TCSC implementation several such basic compensators may be connected in series to obtain the desired voltage rating and operating characteristic
TCSC is a capacitive reactance compensator which consists of a series capacitive bank shunted by a thyristor controlled reactor inorder to provide smoothly variable capacitive reactance.