FACTS AND HVDC LIGHT FOR POWER SYSTEM INTERCONNECTIONS

Introduction The deregulation of the electricity market together with increasing constraints resulting from social opposition to the installation of new facilities puts new demands on the operators of transmission and distribution systems. These new trends enhance the need for flexibility, power quality and increased availability of transmission and distribution systems by using tools which can be implemented with limited investments, short delivery times and short planning and decision making horizons. FACTS (Flexible AC Transmission Systems) is a term denoting a whole family of concepts and devices for improved use and flexibility of power systems. Some of these devices have today reached certain maturity in their concept and application, some are as a matter of fact quite established as tools in power systems. This paper will treat benefits of FACTS devices applied in power systems such as increased power transmission capability, improved static and dynamic stability, an increase of a availability and a decrease of transmission losses. Examples will be given of FACTS devices which have reached a more or less commercial degree of applicability in power systems, salient design features of these as well as operational experience. The paper also treats HVDC Light, a new DC transmission system technology, still consisting of well-known components forming the system. HVDC Light is very suitable for DC power transmission for a number of applications, as will be highlighted in the paper.