Classificação das perdas de excitação em geradores síncronos: uma abordagem considerando a diferenciação em relação aos curtos-circuitos e às oscilações estáveis de potência

Abstract

The synchronous generator is a machine widely used in electrical power systems (EPS), which operates with constant frequency. Its fuctioning mainly depends on the continuous use of excitation systems that are susceptible to problems such as short-circuits, which can cause its partial or total inactivity, as well as the incorrectly operation of the machine and irreversible damage to its structure and also to the electrical system to which it is connected. The study of the operation of these equipment is essential to ensure the dynamic balance of operation of the electrical system. Thus, studies aimed at mitigating failures in these systems are frequent and necessary. The failures that occur in control systems can take to unbalanced conditions, affecting the life of the machine and the equipment around it. The main characteristics seen in the electrical properties during the loss of the excitation system are: the reduction of the voltage, the increase of the current in the terminals of the machine, the decrease of the generated active power and the operation as inductive machine, where it consumes reactive power. Several techniques have been proposed to detect the loss of excitation, among which the Mason and Berdy methods stand out, being widely used. Although, classical techniques present selectivity problems in some situations, providing to the creation of new techniques that are proposed to improve their performance. This work proposes a new methodology for detecting loss of excitation (LOE) in synchronous generators, based on the analysis of the envelopes of voltage and current waveforms. The proposed technique was tested in different operating conditions of the system, simulated via ATPDraw software, presenting robustness and great precision in the classification of LOE, showing as a tool capable of increasing the reliability of the protection of synchronous generators. Key-words: synchronous generator, loss of excitation, voltage and speed governing systems, protection systems, Signal processing.