Flexible AC transmission system

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."

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

Series compensation

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

Shunt compensation

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

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)

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)

External links

Siemens AG - FACTS website.

Electricity distribution | Electrical engineering