Avaliação do desempenho de funções de proteção aplicadas em Reatores Shunt

Abstract

The increase in the length of transport lines with high voltage levels has been distributed in countries with large territorial extensions, resulting in the demand for resources destined to control these levels. One of the possible adjustments attributed to voltage regulation is the use of shunt reactors in the lines. This equipment makes voltage regulation possible because, by absorbing excess capacitive reactives in the line, they maintain voltage within acceptable ranges for operation. Therefore, given the relevance of shunt reactors for the proper functioning of transmission lines and the electrical system, it is essential to ensure the correct functioning of the protection functions applied to shunt reactors. Therefore, this work presents an investigation into the application of different types of protection functions traditionally employed by manufacturers in reactors, such as restricted earth fault protection (REF), directional protection of negative sequence (32QF and 32QR), differential protection (87) and distance protection (21), which is normally used as a backup. The logic of each specific function aims to guarantee the operation and selectivity of protection in different short circuit situations. Therefore, in order to evaluate the protections, simulations were carried out in the software Alternative Transient Program (ATP), through which a 500 kV/60 Hz transmission line 400 km long and 60% shunt compensation was modeled. In the different simulations, different scenarios of internal short circuits in the reactor were evaluated, covering both the type of turn-to-ground faults and turn faults. Furthermore, we will understand the best functioning of protection schemes, external faults were applied to the equipment. Furthermore, we will understand the best functioning of protection schemes, external faults were applied to the equipment. Furthermore, a comparative evaluation was carried out between the performance of the different protection functions investigated, varying several criteria such as the type of fault, number of coils involved in the short circuit and the values of the leakage factors. Furthermore, transient analyzes and parametric sensitivity analyzes were performed. Based on all the results obtained, and comparing different protection schemes implemented in available commercial relays, it appears that the 21 and 32Q functions stand out, as similar and better performances were highlighted in relation to the other functions evaluated. In general, the 21 and 32Q functions work for all turn-to-ground faults and turn faults, regardless of the number of turns involved and the value of the leakage factor. Comparatively, the distance function proved to be faster, with an operating time of less than one cycle. Thus, it is stated that the distance function can also be used as main protection, together with other traditionally used functions, in order to increase the performance of the reactor protection scheme.