Abstract—This Paper studies the effect of a parallel Metal Oxide Varistor (MOV) on the ferroresonance oscillations of the transformer including nonlinear core losses. It is expected that the arresters generally cause ferroresonance ‘dropout'. Time-domain simulation has been carried out using MATLAB SIMULINK to study this effect. Simulation has been done on a three phase unloaded transformer with one open phase. Effect of varying input voltage has been studied. The simulation results reveal that connecting the arrester to the transformer poles, exhibits a great mitigating effect on ferroresonant overvoltages. Phase plan along with bifurcation diagrams are also presented. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos and magnitude of ferroresonant voltages has been obtained, showed and tabulated.

Index Terms—Power transformer, nonlinear core losseseffect, chaos, ferroresonance, Metal Oxide Varistor (MOV).

Hamid Radmanesh is with Electrical Engineering Department, Shahab Danesh Institute of Higher Education, ghom, Iran(e-mail: Hamid.radmanesh@aut.ac.ir).
Matin Nademi and M. Nademi are with Department of Electrical Engineering, Islamic Azad University, Takestan Branch, Takestan, Iran(e-mail: hrbscstudent@gmail.com; mam.nademi@gmail.com). 

Cite: Hamid Radmanesh, Matin Nademi, and Maryam Nademi "Ferroresonance Phenomena in Unloaded Transformers Applying MOV," International Journal of Computer and Electrical Engineering vol. 4, no. 5, pp. 753-757, 2012.