Ageing of Solid Insulation in Transformer and Reactor Windings

This chapter presents an overview of the design and construction of windings for liquid-immersed transformers and reactors. It then presents the different kinds of solid insulation used in the construction of transformer and reactor windings, especially paper and pressboard. Both paper and pressboard contain mostly cellulose, and so this chapter then describes the ageing of cellulose during the operational lives of transformers and reactors. This chapter presents different methods for life assessment of cellulose insulation, with special emphasis on assessment of ageing from chemical markers released into the liquid insulation.