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Background and Objectives: The occurrence of ferro resonance is a very complex phenomenon in power systems. In circuits including inductors and capacitors, if the value of zc = zl becomes, an intensification or resonance state is created in the circuit. In circuits and networks that have saturated inductors, nonlinear resonance or ferro resonance is created, Ferro resonance is a nonlinear resonance phenomenon that occurs between the network capacitor and the nonlinear inductance of the transformer during saturation. Ferro resonance at the main frequency and higher frequencies cause insulation problems and at low frequencies causes thermal problems. In the event of this phenomenon, the voltage range increases to a considerable extent and may also be distorted, which due to the structure of the winding connections in transformers can cause damage to electrical installations. Methods: In this paper, we study and simulate the phenomenon of ferro resonance and provide solutions such as using high resistance on the primary side of the transformer and the combination of resistors and inductors on the secondary side of the transformer to damp the ferro resonance in MATLAB software. Furthermore, the utilization of surge arresters is discussed in detail. Results: It is illuminated that utilization of suggested approaches has an acceptable reduction rate on the damping of ferro resonance fluctuations. Especially when using resistor and inductor simultaneously the fluctuations reduce and ferro resonance is damped immediately. Conclusion: It is important to pay attention to the transformer and the amount of capacitors in transmission lines, especially cable lines. Furthermore, asymmetric switching is another important factor. High resistance can reduce fluctuations but causes power losses in the circuit but using Resistance and inductor structure are able to create acceptable damping and reduce fluctuations without loss problems. The presence of a surge arrester can also reduce the overvoltage caused by ferro resonance to an appropriate level.

Corona discharge is of great interest from the physical point of view and due to its numerous practical applications in industry and especially one of the most important sources of loss in the high voltage transmission lines. This paper provides guidelines for the amount of electric loss caused by corona phenomenon occurred around a DC high voltage wire placed between two flat plates and influence of wind speed rate on the amount of corona loss using COMSOL Multiphysics. So electric potential distribution patterns and charge density diffusion around the wire are studied in this article.

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