Comparação entre o plano alfa e o diferencial percentual aplicados à proteção de transformadores de potência

Abstract

The alpha plane is a geometric representation of the ratio of the currents entering and leaving a protection zone in a complex plane. The relay manufacturer Schweitzer Engineering Laboratories uses this plane in their line differential relays, but not for application in power transformers. In view of this, this work presents a comparison between the alpha plane and the percentage differential applied to power transformers, in order to verify the possibility of greater effectiveness in detecting and removing certain types of faults, such as inter-turn faults and turn-to-ground faults. For this purpose, the alpha plane was implemented in a SEL-451 relay through programming. The use of the differential element through the alpha plane resulted in a significant reduction in the protection actuation time. With this reduction in the operating time, it is expected to significantly decrease the electrical and mechanical damage caused to the transformer during faults, considering the reduction in the time the equipment is exposed to faults.