Direct calculation of the stability domains of three-phase ferroresonance in isolated neutral networks with grounded neutral voltage transformers

Stability domains of ferroresonant oscillations must be computed and, if needed, countermeasures must be taken in order to avoid serious damage to the power networksʹ equipment. In this paper, Clarke components are used to write the equations of a representative three-phase circuit under a canonical form and give a simple physical interpretation of the three-phase ferroresonance phenomenon. A method is proposed to approximate the quasi-periodic oscillations by periodic ones. The solutions and their domains of stability are computed by the harmonic balance method. An application to a field case is presented.