Controlling ferroresonance oscillations in potential transformer: Part II

In this work at first ferroresonance phenomenon is introduced and then various type of ferroresonance in a potential transformer (PT) in the case of applying Metal Oxide Surge Arrester (MOSA) in parallel with PT is simulated. Finally effect of neutral earth resistance on the controlling and stabilizing these oscillations is studied. The proposed approach was implemented using MATLAB, and results are presented. It is expected that this resistance generally can cause ferroresonance `dropout´. For confirmation this aspect, Simulation is done on a one phase potential transformer rated 100VA, 275kV. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial with q=7. The simulation results reveal that considering the neutral earth resistance on the system configuration, exhibits a great controlling effect on ferroresonance over voltages. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance over voltages has been obtained and presented.