This paper handles two main areas of significant interest concerning the use of SVCs in transmission systems:• The operational benefits of SVC support during network contingencies• The reliability of SVCs in general and at contingency events in particular At transmission level SVCs are installed to act as insurance, supporting the system during recovery from severe contingencies. It is therefore important to address issues concerning the requirements of actual contingency var support and required reliability of an SVC unit to be able to support the network at contingency situations. Despite the fact that SVCs have been in use since the mid 1970's there still seem to be uncertainty regarding these fundamental parameters decisive to utilities when considering the FACTS alternative for major investments. This paper aims to shed some light on these issues by looking at SVC's in utility applications, addressing the reliability issue by looking at experiences from operating and maintenance of a number of SVCs in Australia, Canada and the USA.

STATCOM technology has experienced a significant degree of market diffusion over the last years. This is largely due to the technological advancement of the modular multilevel converter topology. This paper presents the basic aspects of this topology and provides three case studies for existing multilevel STATCOM references that underline the advantages of this technology -namely: modularity, low interaction with the network through low generation of harmonics and less primary equipment resulting in a small footprint.