Análise do desempenho de relé de distância para proteção de linhas de transmissão em alta tensão

Abstract

The complexity and criticality of electrical systems make electrical protection a vital aspect for the safety and reliability of the system. Among the protection devices, distance relays are crucial in locating and eliminating faults, preventing damage to the system and equipment, and minimizing power supply interruptions. However, the performance of the distance relay can be compromised in situations of faults close to the relay’s installation location, where voltage values become extremely low, hindering the functioning of the device’s phase comparators and causing false trips. This scenario challenges the effectiveness of distance relays, particularly the admittance-type distance relay. Within this context, the objective of this work is to analyze the performance of the admittance relay using MATLAB-SIMULINK under different fault conditions, focused on enhancing its protective capability in challenging scenarios. The following methodological approach is employed for this development: (i) collection of data from the transmission line defined for study; (ii) dimensioning of potential transformers; (iii) determination of the settings for relay 21 protection zones; (iv) implementation of the parameterized data in MATLAB-SIMULINK; and (v) presentation of the performance evaluation results of the relay. The simulations provide a detailed analysis of impedance behavior based on voltage and current measurements during different types of short circuits, as well as an evaluation of the R-X diagram, essential for verifying the protection zone coverage and impedance trajectory during faults. The results show that memory voltage polarization offers an alternative solution to traditional polarization, especially in three-phase faults, where voltage values can be very close to zero. However, the study also points out that in single-phase faults, the application of memory voltage can result in improper relay actions on components unaffected by the fault. In conclusion, the study reinforces the importance of memory voltage polarization in short-line protection systems. Still, it highlights the need for a careful balance between sensitivity and accuracy, especially when dealing with different types of faults.