Optimal location of shunt FACTS devices in long transmission lines

FACTS devices are now recognised as a viable solution for controlling transmission voltage, power flow, dynamic response, etc., and represent a new era for transmission systems. It has been proved that the centre or midpoint of a transmission line is the optimal location for shunt FACTS devices or reactive power support and the proof is based on the simplified line model. The validity of the above optimal location of shunt FACTS devices is investigated, when the actual model of the line is considered. It is found that the FACTS device needs to be placed slightly off-centre to get the highest possible benefit. Both the power transfer capability and stability of the system can further be improved if the shunt FACTS device is placed at the new optimal point instead of at the midpoint of a line having some resistance. This finding contradicts the previous results found for the simplified line model