FACTS - powerful systems for flexible power transmission

Abstract

emand for electrical energy continues to grow steadily, and is particularly strong in those countries on the threshold of industrialization. For various reasons, electricity grid upgrades, and especially the construction of new transmission lines, cannot keep pace with the growing power plant capacity and energy demand. Finding suitable right-of-ways is particularly difficult in the industrialized countries, and gaining the necessary approval is more time-consuming than ever. In addition, power line construction ties up investment capital that could be used for other projects. Due to this situation, operators are looking for ways to utilize the existing power lines more efficiently. Two areas require special attention. In the first place, there is a need to improve the transient and steady state stability of long lines. This is because some power lines cannot be loaded to anywhere near their natural load rating – let alone the thermal limit rating – due to relatively low stability limits. Action taken in support of stability during and after line faults can improve system reliability just as much as by adding one or more lines. Secondly, the load flow needs to be improved in closely intermeshed networks as the ‘natural’ load flow resulting from the load conditions and existing line impedances is not necessarily the load flow that will minimize the transmission losses. Another aspect is flexibility: a deregulated energy market requires flexible power system operation to ensure that the electricity supply contracts can be fulfilled. Flexible AC Transmission Systems (FACTS) have all the capability grid operators need to meet the challenges presented by the fast-changing energy market.