A análise da influência dos modos típicos de polarização do relé de distância MHO no comportamento de sua característica de operação durante condições de faltas clássicas no sistema elétrico

Abstract

This paper has the purpose of presenting to students and specialists on power system protection some effects of typical polarization methods on Mho characteristic of distance relays. The operational characteristic of the polarized Mho relay is not always static, varying according to fault location, type of fault, power system characteristics and polarization method. The need for determination the direction of fault is the main target of this work. The direction of short circuit currents regarding the protection relay, in network power systems with several sources connected, is very important for tripping the smaller portion of the system, necessary for segregate the defect. Therefore this work shows the importance of directional definition for the protective relay, the usual polarization types used by Mho distance relays and their graphic andmathematic operational characteristics. The topics addressed are merely a little introduction to the study of the Mho polarized relay. Some issues which have no impact on the behavior of the Mho relay operational characteristic are not analyzed, like pre-fault conditions, magneticcoupled transmission lines, dynamic load conditions, DC component effect, influence of the source impedance behind the relay, frequency variation effect and others. Thus there is a wide range for investigations related to Mho type distance relays, not to be forgotten that the polygonal relays are equally an open field. The comparative analysis of Mho and polygonal characteristics behavior is some extremely important and interesting, once allows assessing pros and cons of each one. These topics, besides researches on new distance relays polarization methods are fitted to advanced scopes.