The independent regulation structure（main transformer and adjustable transformer） is generally adopted in extra high voltage（EHV）

thus

there are several disadvantages

e.g.

covers large area

installation

debugging and maintenance complex

for the mentioned transformer. Therefore

we put forward a novel body structure which has doublebody with one tank

namely

the main transformer and the regulating transformer are designed in the same tank.The structure has advantages which greatly reduce the cover area

and reduce the difficulty of installation

debugging

and maintenance. The 3-D finite element analysis（FEA） combined with the magnetic circuit characteristics of EHV double body transformer is used to compute the leakage magnetic field for the mentioned transformer

and the ‘magnetic field-circuit’ coupled mathematical model is established to compute and analyze the magnetic flux density and loss in structure parts. At the same time

we investigate the short-circuit impedance of the transformer by the energy method

and finally analyze the short-circuit impedance affected by the new structure through experimental quantitative analysis. The results show that the magnetic density amplitude of oil tank reduces by 0.01 T

the magnetic density amplitude of clamp reduces by 4.16%

the losses of clamp reduces by 8.1%

and the short-circuit impedance increases slightly and the maximum amplitude is 2.56% after adding voltage variation transformer. The calculation error is less than 2%

which is verified by the comparison with experimental data. The computation and analysis show that the characteristics between the novel structure and the original one hardly change

and the novel structure conforms to the requirements of the production technology.