Asset optimisation strategies for large transformers

For a transmission company such as NGC (National Grid Company) the transformer stock represents a major capital asset. There are some 650 units with ratings 100-1000 MVA and high voltage windings of 400 and 275 kV. Their replacement value would approach £1B. Whilst much debate within the asset management area concentrates on replacement policies, the issues are much wider. This paper attempts to describe some of the technical aspects of these issues which are addressed within NGC´s Technology and Science Division (TSD)