Three‐Phase Models of Transformers and Conductors

The chapter describes three‐phase models of two‐winding three‐phase transformers and conductors. A three‐phase two‐winding transformers, total of six windings can be considered a 12‐terminal coupled network, consisting of three primary windings and three secondary windings mutually coupled through the transformer core. Symmetrical component models can be arrived at by using symmetrical component transformations. Each winding has some coupling with all the other windings. The primitive admittances are considered on per unit basis, and both primary and secondary voltages are 1 per unit. No zero sequence currents can occur between wye and delta side of a balanced wye‐delta transformer. A three‐phase transformer winding connection of delta primary and grounded‐wye secondary is commonly used. A three‐phase conductor with mutual coupling between phases and ground wires has an equivalent representation. The currents and voltages with capital subscripts relate to primary and those with lower case subscripts relate to secondary.