| One northwest central electrical station is a 35kV transformer& distribution station which is reformed and expanded on railway line. Since the substation was operated on the July 27,2006,1# main transformer occurred cable head breakdown phenomenon on August 8,2006.From then on, the cable head breakdown and abnormal discharge in cabinet were frequently taken place, this directly affects the safe operation of power supply.Against that background, the paper studied over-voltage causes, by means of researching and analyzing the existing equipment and operating methods and theoretical analysis, the paper preliminary concluded that the over-voltage was resonance over-voltage which is caused by submerged arc furnace's harmonic wave which is feed backed to bus. To analyze the specific type and the mechanism of over-voltage, this paper built the substation model with PSCAD/EMTDC simulation software, and emulated out the generating process of substation over-voltage by injecting harmonic wave on the power inlet.In quick succession, by simulation results data and theory, the paper came to the decision that the substation's over-voltage type was linear resonance. For the inhibition of linear resonance over-voltage, combining theory this paper analyzed and compared the means, finally the paper used the way of paralleling capacitor on the power inlet to change the system parameters. And then the paper selects the appropriate size of the mode of parallel capacitors by simulation comparation, the results show that the method is effective.To verify the correctness of this analysis, we developed a set of voltage control and suppression equipment, the equipment and harmonic suppression capacitors was linked to network operation at the same time, the equipment can effectively monitor system voltage, and cut off excessive over-voltage in time. By running of this device, it verified the correctness of this article, and provided a realistic basis for solving the over-voltage of the substation.
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