The impulse potential distribution in actual power transformer winding（due to possessing no tap pin）can not directly be measured. Using similar electric property and tapped transformer model instead of the original model to research the measuring impulse voltage distribution has important engineering practical value. To research all kinds of physical constants and electric field intensity under the same conditions between reduced-scaled and original models

according to the relationship between physical quantities

we established a simplified shrinkage ratio criterion. Secondly

according to the actual power transformer original model and shrinkage ratio criterion

we designed a similar ratio 1/20

typed 10 k VA-220 V/2 400 V tapped transformer reduced-scaled model. Then

using the finite element simulation software COMSOL Multiphysics

we simulated the reduced-scaled and original models of the electric field

magnetic field

and electromagnetic field. Finally

we established a test platform to measure the winding impulse voltage distribution of transformer reduced-scaled model under ns pulse voltage. The comprehensive and comparative analyses of the simulation verify the correctness of the rule of shrinkage ratio. It is found that the impulse voltage distribution of transformer winding is uneven and high-voltage side withstanding voltage is higher.