Flexible AC transmission system

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"FACTS" redirects here. For the Swiss weekly magazine, see FACTS (newspaper).

Flexible Alternating Current Transmission System (FACTS) is a static equipment used for the AC transmission of electrical energy. It is meant to enhance controllability and increase power transfer capability. It is generally a power electronics-based device.

FACTS is defined by the IEEE as "a power electronic based system and other static equipment that provide control of one or more AC transmission system parameters to enhance controllability and increase power transfer capability."

1 FACTS technology
- 1.1 Series compensation
- 1.2 Shunt compensation
2 Examples of FACTS for series compensation
3 Examples of FACTS for shunt compensation
4 External links

[edit] FACTS technology

FACTS could be connected:

in series with the power system (series compensation)
in shunt with the power system (shunt compensation)
both in series and in shunt with the power system

[edit] Series compensation

In series compensation, FACTS is connected in series with the power system. It works as a controllable voltage source.

In series compensation generally inductors are connected in series with the transmission line that is because in case of long transmission line due to series inductance when a large current flows through it causes a large voltage drop.Now to compensate that large voltage drop due to inductance series capacitance are connected.

[edit] Shunt compensation

In shunt compensation, power system is connected in shunt with the FACTS. It works as a controllable current source.

Shunt compensation is of two type

1. Shunt capacitive compensation

2. Shunt inductive compensation

Shunt capacitive compensation

This method is used improve the power factor. Whenever an inductive load is connected to the transmission line power factor lags because of lagging load current. Now to compensate that shunt capacitance are connected which draws current leading the source voltage. The net result is improvement in power factor.

Shunt inductive compensation

In this method of compensation inductance are connected across the transmission line. This method is used either charging of transmission line or when there is very low load at the receiving end of the transmission line. Due to very low load or no load very low current or very low charging current flows in the transmission line. Now presence of shunt capacitance in the transmission line causes voltage amplification(Ferranti Effect). Sometime the receiving end voltage may become double the sending end voltage( generally in case of very long transmission line). Now to improve that shunt inductane are connected to the transmission line.

[edit] Examples of FACTS for series compensation

Static Synchronous Series Compensator (SSSC)
Thyristor Controlled Series Capacitor (TCSC) or Thyristor Controlled Series Reactor (TCSR)
Thyristor Switched Series Capacitor (TSSC) or Thyristor Switched Series Reactor (TSSR)

[edit] Examples of FACTS for shunt compensation

Static Synchronous Compensator (STATCOM) previously known as a Static Condenser (STATCON)
Static VAr compensator (SVC)
- Thyristor Controlled Reactor (TCR)
- Thyristor Switched Reactor (TSR)
- Thyristor Switched Capacitor (TSC)
- Mechanically Switched Capacitor (MSC)