Simulation of ferroresonance with hysteresis model of transformer at no-load measured in laboratory

Abstract

Ferro-resonance is a nonlinear dynamic electrical phenomenon in a power system. It may occur in ungrounded three-phase lines at transformer banks on no-load due to malfunctioning of switching devices (one pole closing at first). A hysteresis model is developed with core-type transformers and power capacitors simulating line transformers and capacitance respectively to investigate ferroresonance. For any operating voltage applied to series combination of capacitance and transformer windings at no-load, the critical value of capacitance to cause ferroresonance jump is determined using Rudenbergpsilas graphical method. The resulting ferroresonance over-voltages across circuit components are simulated at various line conditions using the data obtained from an experimental B-H loop of the no-load transformer. The results show the ferroresonance overvoltages reaching dangerously high peak of fundamental frequency across the circuit elements.