Elimination of Chaotic Ferroresonance in power transformers including Nonlinear Core Losses applying of Neutral Resistance

This paper studies the effect of neutral resistance on the onset of chaotic ferroresonance and chaotic transient in a power transformer including nonlinear core losses. It is expected that this resistance cause ferroresonance ‘dropout'. Time-domain study has been carried out to study this effect. Simulation has been done on a three phase power transformer rated 50 MVA, 635.1 kV with one open phase. The magnetization characteristic of the transformer is modeled by a single-value two-terms polynomial. The core loss is modeled by third order power series in terms of voltage includes nonlinearities in core model.The simulation results reveal that connecting the neutral resistance to the transformer, exhibits a great mitigating effect on voltage ferroresonance. Phase plane along with bifurcation diagrams are also derived. Having Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance voltages has been obtained and presented. Key word: Chaos, Bifurcation diagram ,Ferroresonance ,Power transformer ,Neutral Resistance