Ferroresonance an electrical phenomenon may cause overvoltages in the electrical power system. In this paper, an overview of available papers is provided, at rst ferroresonance is introduced and then various type of ferroresonance in a voltage transformer (VT) is simulated. Then eect of new model of circuit breaker (CB) on damping ferroresonance oscillation is examined. Finally eect of earth resistance on the stabilizing these oscillations in the case of nonlinear core loss has been studied. Core loss is modelled by third order power series in terms of voltage and includes nonlinearities in core loss. For conrmation, the simulation is done on a one phase voltage transformer rated 100VA, 275kV. The simulation results reveal that novel modeling of circuit breaker exhibits  great controlling eect on ferrores- onance overvoltages.