Research On Transient Of Large Power Transformer Winding Under Very Fast Transient Over-voltage

With the increasing of voltage levels,the gas-insulated substations(GIS)are widely used in the development of power systems.A very fast transient over-voltage(VFTO)will be generated during the isolation switch closing operation.The rise time of VFTO reach up to ns,with frequency up to MHz.Once VFTO invades the transformer directly connected to it through the conductor tube,it will cause damage to the winding insulation.At present,there is no conditions for conducting physical experiments on UHV large-scale power transformers directly.Therefore,it is of great theoretical significance and engineering value to carry out the research of the over-voltage distribution of large power transformer winding under VFTO.In this paper,it involves the following study about the over-voltage of the large power transformer winding under VFTO in the paper:First of all,the large power transformer winding can be equivalent to transmission lines,and it is derived each voltage transfer function model based on a multi-conductor transmission line admittance parameter.The vector matching method based on Artificial Fish Swarm and Frog Leaping Algorithm improves calculation accuracy,which is used to realize the rational approximation of transfer functions decreased maximum of fitting error by 10.1%.Secondly,the parameters of 500 kV transformer provided by BAODING TIANWEI ELECTRIC Co.,LTD,which is utilized to establish physical model.The simulation calculate the time/frequency domain over-voltage distribution of each winding under VFTO.A High Frequency Circuit Model was built by network synthesis technology,and it is verified by the international universal electromagnetic transient software ATP-EMTP.Finally,the electric transient software ATP-EMTP is applied to construct equivalent circuit of 1100 kV UHV substation test circuit,which is utilized to analyse the effect of different dis-connector arc models,different branch bus lengths and residual charges on VFTO.And this paper compares and analyse different measure used to suppress VFTO.The research work in this paper can provide theoretical support for preventing thedamage caused by transformer insulation under VFTO and improving the insulation design.At the same time,selecting corresponding equipment for GIS substations and providing fault analysis reference suppression.