Research On The Lumped Parameter Modeling Of Transformer Windings Based On Fractional Calculus

Switching operations in gas insulated substation (GIS) may generate very fastovervoltage (VFTO) which is dangerous for the insulation of the transformer. Theexperience shows that VFTO has a very short rise time and its main oscillating frequencywhich depends on the length of GIS is between1MHz to40MHz. When VFTO invadesinto the transformer, an unbalance of voltage distribution in transformer windings can becaused. Therefore, the study of the voltage distribution in transformer windings underVFTO is of essential interested for insulation design.The thesis proposes a fractional lumped parameter model (FLP) of transformerwindings containing fractional lumped parameter components. Based on the MTL model,the multiple port model admittance parameters of MTL system with frequency dependentparameter is abstracted, approximating the MTL system using approach method. Afterforming the network’s time-domain state equations and solve these equations with theapproach which is derived from the discretness of fractional derivative, the time-domainresponse of network is obtained. Fractional lumped parameter modeling and simulationare accomplished against transformer windings of different voltage levels, andcomparison is carried out among the fractional lumped parameter model and practicalmeasured data based on the simulation results. As the analysis shows, the fractionallumped parameter model is able to preciously calculus the voltage distribution intransformer windings under VFTO.