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

Series inductance occurs in long transmission lines, and when a large current flow causes a large voltage drop. To compensate, series capacitors are connected.


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

Shunt compensation is of two types:

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. To compensate, a shunt capacitor is connected which draws current leading the source voltage. The net result is improvement in power factor.

Shunt inductive compensation

This method is used either when charging the transmission line, or, when there is very low load at the receiving end. Due to very low, or no load -- very low current flows through the transmission line. Shunt capacitance in the transmission line causes voltage amplification (Ferranti Effect). The receiving end voltage may become double the sending end voltage (generally in case of very long transmission lines). To compensate, shunt inductors are connected across the transmission line.