Research On Fractional Model Of Transformer Winding Under VFTO

With the rapid development of our country electric power system, gasinsulated substation (GIS) because of its small size, compact structure andconvenient operation and maintenance has been widely used. But the opening orclosing operation in the substation lightning invasion may cause Very Fast TransientOvervoltage (VFTO) which wave front is very steep, very high frequency on thetransformer winding. This may cause insulation aging and even breakdown of thetransformer windings. So under the action of VFTO, research of the transformerwinding model has the vital significance for analysis of the voltage distribution onthe winding.In this paper, based on the original multi-conductor transmission line model oftransformer winding, and full consideration of skin effect on the winding,introduced the most advanced mathematical modeling tools, fractional ordercalculus, fractional order model of transformer windings under VFTO is established.The model in time domain intuitive expressed parameters, avoiding the complexityof time-frequency domain transform. Paper also discussed the solution to thecorresponding transmission line fractional differential equations. Through thediscrete space, the fractional order differential item of approximation to replace,etc., the transmission line fractional differential equations into ordinary differentialequations. Further by precise integration and recursive convolution method,improve the operation efficiency, shorten the calculation time. Finally, thesimulation results in this paper, through two practical transformer winding, verifiedthe fractional order model and its algorithm. It expanded the modeling method oftransformer winding under high-frequency. For the protection of transformerwinding insulation and enhances the stability of power system operation is of greatimportance.