The Research On Ferroresonance Elimination Device Of Grounded Low Current In Power Systems

Electricity is one of the important strategies of the economic and social development in our country. It's quite essential to modernize the electric industry. Once anything wrong happens in power system, the loss will be greater than itself, sometimes it would tragedy.The power supply and the underground way in our country is divided the neutral isolated distribution. In the neutral grounding, each voltage focus in the power system is fixed, so the neutral transferring the voltage won't usually happen. However, once the sigle phase is grounded it could trip out. This phenomenon would offect the power supply reliability, so the sigle phase grounding seldom is used in generally. In the neutral ungrounded system, generatrix of the transformer substation usually connects starlike electromagnetic potential transformer. Then when something unexpected often happen, e.g. single phase of grounding fault will arouse high-voltages with the cooperation of different parameters, high harmonic, subharmonic or harmonic ferroresonance many happen.First, the essay introduces the generation process and the features of the Ferromagnetic resonance through the example of single resonance, and takes them as the guidance for the elementary course of circuit. Them, it introduces Three Phase Ferromagnetic resonance circuit thoroughly and makes a further analysis of its generation of high harmonic, harmonic ferroresonance and the mathematical model of subharmonic. The essay based on the model of the three phase ferromagnetic resonance, according to a group of worked out numbers, takes the example of the single phase grounded fault, uses Simulink to stimulate the whole regular process of the ferromagnetic resonance in power system: operate steadily --> single phase grounded --> remove grounded --> produce resonance That can embody the generation and disappearance of the ferromagnetic resonance clearly.Finally, this essay advance a design approach of the device Ferroresonance Elimination in Low Current Systems is control by IGBT as will as introduce the motional principle of the device. It introduces the designation of hard wire and soft wire of the device. The device can eliminate high harmonic, harmonic ferroresonance, 1/2 subharmonic and 1/3 subharmonic, it have eliminate Ferroresonance speedy characteristic.