Métodos computacionais da resposta de circuitos não lineares com excitação periódica: um estudo voltado para a análise de ferroressonância.

Abstract

Ferroresonance is a nonlinear oscillation that has been observed in electric power systems and is one of the sources of weakly damped overvoltages of harmonic or subharmonic frequencies. The analysis of ferroresonance is essentially the determination of the multiple steady-state solutions of a nonlinear circuit. Only one among the several possible solutions is the desired or normal solutions and the other solutions are abnormal in natural. It is possible that a switching operation could cause the circuit operating in the normal state to jump to an abnormal state and the ferroresonant overvoltages are likely to damage equipment such as surge arresters. The phenomenon of ferroresonance has been studied and the circumstances in which it has been observed are described. The methods of determining the steady-state response of nonlinear circuits are then described. Of these methods, the gradient and Newton-Raphson schemes convert the problem of determining the steady-state response of a nonlinear circuit into a two-point boundary value problem. These techniques have been found to be very efficient. The gradient and Newton-Raphson schemes have been adapted for the study of ferroresonance. A typical ferroresonant circuit, the equivalent of a potential transformer disconnected from the energized busbar, has been studied in detail. The ferroresonance characteristic of the circuit has been determined and the range of parameter values for which there is a risk of ferroresonance has been identified.