Análise do desempenho de relés de distância sob condição de saturação dos transformadores de corrente

Abstract

Distance relays are widely used in the protection of transmission lines (TLs) and its func-tioning is characterized by measuring the impedance to the fault point. The voltage and current signals of the network are processed by the relay, which calculates the impedance from the relay installation point to the fault occurrence point. The voltage and current signal are provided by particular transformers appropriate for protection purposes. Thus, potential (PTs) and current transformers (TCs) are designed to replicate the voltage and current signals as faithfully as possible, allowing for the proper functioning of protective relays connected in their secondary winding. However, current transformers are subject to saturation of the core. This phenomenon causes distortions in the waveform of the current signals received by protective relays, which could maloperates or even ‘not operate for short-circuits inside their protection zones. This study aims to investigate the performance of distance relays processing current signals provided by saturated TCs in order to identify possible problems of under or overreach considering different levels of remanent flux core and different fault types. A system test was used to simulate a transmission line in EMTP-ATP. The voltage and current sig-nals obtained from the simulations were used in the study. The distance relays operational logics were programed in MATLAB® to determinate the distance protection performance considering different polarizations. After the verification of the possible problems, solutions are proposed to rely with the saturation phenomenon in distance protection of transmission lines.