FACTS to enhance availability and stability of AC Power Transmission

Recent blackouts have focused on the critical importance of secure and reliable power supply. Traditionally, strengthening power grids has involved the construction of new transmission lines, usually at considerable cost and in the face of public objections. Power technology developments in recent years, however, are now offering new methods for stable, cost effective, bulk transfer of power over existing transmission lines. Furthermore, into focus is coming the need to provide adequate reactive power balance for various system conditions, including disturbances. Recent years´ unbundling of power generation and transmission has brought new aspects into the picture, as grid companies no longer can be certain to rely on generators to have their need for reactive power satisfied. In other words, transmission suppliers may have to provide their own vars. This brings to the agenda the question what kind of var supply devices are available, and for what uses, and at what cost. This paper will dwell on the issue, particularly highlighting state of the art devices such as SVC (Static Var Compensators) and STATCOM, as well as their application in power transmission.