Avaliação da proteção de distância em linhas de transmissão de circuito duplo com estudo de caso

Abstract

Approximately 20% of the transmission lines of the Brazilian national interconnected system are double circuit, being the most used configuration type after single circuit transmission lines. For this reason, the importance of studying double circuit transmission lines is highlighted. When two transmission lines are close, such as a double circuit transmission line, a mutual zero sequence coupling is observed between them. This mutual zero sequence coupling interferes in the impedance calculated by the distance protection, in the case of short circuits involving the ground, due to the zero sequence current in the healthy parallel line and the presence of zero sequence mutual impedance. Considering the distance protection applied to double circuit transmission lines, this dissertation presents a comparative assessment between traditional and compensated distance protections, which considers the influence of the operating condition of the parallel circuit on the protected line. In addition, the distance protections are assessed using phase comparators, such that in the results the impedance units operation is analyzed. For this purpose, a 138 kV real transmission system is modeled in the Alternative Transient Program (ATP) software and subjected to single phase-to-ground fault, varying the fault resistance value, the system loading, the power of the sources, the fault line and the fault location in each line. From the results obtained, it is verified that the correction of the mutual zero sequence coupling can improve or worsen the performance of the distance protection in relation to the function 21 traditional, which depends on power of the sources and the fault location. Thus, it is emphasized that for the cases analysed the correction of the mutual zero sequence coupling does not significantly improved the performance of the distance protection.