Ferroresonant oscillations in capacitor voltage transformers

Ferroresonant oscillations are unpredictable and their occurrence is of serious concern, predominantly because of possible damage to equipment such as transformers. It is known that by energising the transformer at different points on the voltage wave, ferroresonant oscillations of different types can be induced. A methodical approach for determining these initial conditions, given a system, is therefore required. Among the available methods, bifurcation analysis appears the most suitable. However, for that purpose, the system equations have to be transformed to their normal form by a mathematically tedious process. Alternatively, as shown in the paper, the integral form of system equations is obtained by assuming a periodic solution. From the transformed equation, the fixed points of the original system equations are determined. The different types of ferroresonant oscillations which occur when these fixed points are used as initial conditions can be studied by numerically solving the original set of equations. Information regarding the periodicity of ferroresonant oscillations can be obtained by plotting the Poincare map of the temporal evolution of the state variables