Análise de alternativas de proteção anti-ilhamento de geradores síncronos distribuídos

Abstract

In this dissertation, we present a detailed study of techniques for islanding detection of distribution systems in the presence of distributed generators in various forms of access and connection. The aim is to set up protection system solutions capable of ensuring the detection of the islanding based on local passive techniques, which have lower costs with respect to remote techniques, for example, the transfer trip. The objective of this work is to achieve through the association of several islanding detection techniques in order to achieve adequate reliability of distributed synchronous generators protection system. Among the existing techniques, the protection functions studied were the overfrequency and underfrequency (ANSI 81 o/u), rate of change of frequency (ROCOF or ANSI 81 df/dt), vector jump (ANSI 78) and directional reactive power (ANSI 32Q). It was found that the 32Q function for loads with inductive power factor less than one complements the functions based on frequency precisely in the range where these are insensitive to islanding, wherein the threshold for operation of this relay depends on the equivalent load power consumed locally. For cases of islanding caused the intentional opening of the distribution feeder, the islanding detection for loads with a inductive power factor can be guaranteed with the use of passive local techniques without the need to burden the installation of synchronous generators protection systems distributed. Although in practice it is very unlikely a distribution circuit has a unity power factor, the association of these protective functions arises as a good solution for the detection of islanding of distributed synchronous generators.