Uma metodologia para análise da coordenação e seletividade da proteção de sistemas de distribuição

Abstract

This work proposes the development of models and numerical methods for the analysis of selectivity and coordination of overcurrent protection in distribution systems. The first step is to adapt an existing program for calculation of faults in phase coordinates, incorporating new algorithms for exact and approximate calculations of fault conditions. The methodologies for fault calculations were developed using the current injections equations in rectangular coordinates. It was then developed and implemented a three-phase formulation for analysis of coordination and selectivity of protection devices, capable of detecting faults and indicating limits of coordination and selectivity in distribution systems. The mathematical models of the main protective equipment and protective functions found in distribution systems were also developed. Fuses, circuit breakers, relays, reclosers, current and potential transformers as well as the protection relay functions 50 and 51 based on the ANSI and IEC standards were modeled. The proposed methodology was developed in MatLab ® and its efficiency was validated using several test systems. The results of studies of each system are presented in the form of Time Currents Curves, tables of operation times and graphs of comparative performance times. As a complement the main philosophies and criteria used in selection and coordination of protective devices are presented.