FERRORESONANT OSCILLATIONS IN CAPACITOR VOLTAGE TRANSFORMERS

Ferroresonant oscillations are unpredictable and their occurrence is o f serious concern, predominantly because of possible damage to equipme nt such as transformers. It is known that by energising the transforme r at different points on the voltage wave, ferroresonant oscillations of different types can be induced. A methodical approach for determini ng these initial conditions, given a system, is therefore required. Am ong the available methods, bifurcation analysis appears the most suita ble. However, for that purpose, the system equations have to be transf ormed to their normal form by a mathematically tedious process. Altern atively, as shown in the paper, the integral form of system equations is obtained by assuming a periodic solution. From the transformed equa tion, the fixed points of the original system equations are determined . The different types of ferroresonant oscillations which occur when t hese fixed points are used as initial conditions can be studied by num erically solving the original set of equations. Information regarding the periodicity of ferroresonant oscillations can be obtained by plott ing the Poincare map of the temporal evolution of the state variables.