Management of Losses for Transformers in Service

This chapter describes the origin of transformer losses; outlines different methods for specifying transformer losses and efficiency; outlines some of the methods used to control transformer losses at the design stage; and describes how transformer losses are measured during acceptance testing. Losses on transformers in service are essentially fixed, unless the transformer is rebuilt for some reason. However, two different methods for managing transformer losses in service have been developed in recent years. One method which is applicable mainly to larger transformers is use of the cooling system to manage transformer temperature and hence load losses. Another method is automatic switch-out of transformers operating in parallel at low loads. Each method is described in detail in the remainder of this chapter.