FERRORESONANCE IN ELECTROMAGNETIC VOLTAGE TRANSFORMERS - A STUDY BASED ON NONLINEAR DYNAMICS

Ferroresonance in electromagnetic voltage transformers, fed through ci rcuit breaker grading capacitance, is studied using nonlinear dynamics methods. The magnetising characteristic of a typical 100 VA voltage t ransformer is represented by a single-valued two-term polynomial of th e order seven. The system exhibits three types of ferroresonance: fund amental frequency ferroresonance, subharmonic ferroresonance and chaot ic ferroresonance, similar to high capacity power transformers fed thr ough capacitive coupling from neighbouring lines or phases. Results al so show that while fundamental frequency and subharmonic ferroresonanc e can occur under commonplace operating conditions, chaotic states are unlikely in practice.