Aimed at transformer damage caused by large short-circuit current

this paper presents three kinds of design scheme improving medium-low winding short circuit impedance based on a 220 kV three-phase three wind-ing load transformer product;First of all

through splitting the middle voltage winding

placing the regulating winding in the middle and the high voltage winding inside to increase the leakage magnetic gap between the low and middle windings

thus realizing the design of three kinds of high impedance transformer with different winding structure;Then

based on the field-circuit coupled finite element method and the flux leakage method

the short-circuit impedance of different design schemes are analyzed and calculated

and the results show that: the scheme of placing the high voltage winding inside is the most obvious improvement of short circuit impedance

which is im-proved by 124.56%. Meanwhile

the calculation results are verified by comparing the results of the two methods. Fi-nally

the eddy current loss and loss density distribution of oil tank and clip caused by various schemes are calcu-lated

and the effect of the loss of structure in the process of high impedance transformer is studied. This paper pro-vides some ideas for the design of high impedance transformer.