Generator protection: Differential and split phase for machines with three windings per phase

In Brazil, about 80% of electricity generation is accomplished through hydroelectric sources. In this vast universe, usage of generators with more than one winding per phase is very uncommon. This type of machine, however, may have specific protection for detecting faults between windings of the same phase in a scheme known as “Split Phase Protection.” An adaptation of the differential protection scheme generator, for the purpose of optimizing the number of current transformers, is also possible with this approach. This paper aims to present the study in a recent project for Furnas (one of the biggest federal government utilities in Brazil), who has machines with these designs. The technical solution presented complies with the requirements for protection for this type of generator winding design.