GERMANO, A. D.; http://lattes.cnpq.br/5861671113603396; GERMANO, André Dantas.
Resumo:
The continuous electric energy supply depends on the proper operation of several systems and
equipments, such as transformers and protection systems. The protection of electrical systems is
done by relay controlled schemes. Transformers require relays that are dependable (no missing
operations), fast and secure (no false tripping), and the differential relays are the ones that best
suit these requirements. This work presents the several types of protection available for
transformers, focusing on differential protection. Basic functional aspects of the three
generations of relays (electromechanical, static and digital) are discussed, along with the
advantages of each one over their predecessors. Both differential and overcurrent relays are
described, besides the disturbances to which they are subjected. The available techniques to
guarantee that differential relays do not operate inappropriately are presented. The work is
concluded with a detailed analysis of digital relays, where their basic architecture and a fault
detection algorithm are discussed.