The Research Of High Impedance Transformer Using Built-in Series Reactor

Transformer,as an important equipment in power system,is widely distributed in every corner of the power grid.With the increasing capacity of power system,short-circuit current surges.In order to reduce the harm of short-circuit current to transformers and other equipment in the power grid,more and more high-impedance transformers are applied in the power grid.However,the existing high-impedance transformer adopts the traditional built-in structure of high-voltage winding,which has problems such as high cost,excessive excitation inrush current when switching on,high loss,and difficult insulation treatment,etc.Therefore,the development of an economical and maintainable high-impedance transformer has important theoretical significance and engineering practical value.This paper presents a new engineering design method for 220 kV three-winding load voltage regulating high-impedance transformer.This method can be divided into the same parts as the conventional transformer and the reactor parts.The inductance of high and low winding is increased by using the reactor,so as to increase its impedance and meet the performance requirements of high impedance transformer.In this paper,the engineering calculation method of the impedance of the built-in series reactor is derived in detail.Considering the particularity of this product,EMTP calculation method is adopted to calculate the potential distribution of the low-voltage winding,and semi-finished products are tested after the manufacture of the transformer body is completed,so as to verify the calculation accuracy of EMTP and provide an important guarantee for the insulation design of the transformer.In terms of structural design,the connection mode of reactor is verified,special design is carried out for special parts,and finally product manufacturing and test are carried out.The final test results show that the design method proposed in this paper completely meets the requirements of specified parameters and achieves the expected purpose: the error between design and test is less than 1%.Compared with the conventional high-impedance transformer,this method is 150,000 yuan cheaper,and it is a economical and ideal design method for high-impedance transformer.