To eliminate the error of voltage coefficient measurement caused by shielding leakage and adjacent interference in the transformer series voltage summation

a measurement method for the voltage coefficient of two-stage transformers in series based on three-port network is proposed. Firstly

the types and sources of additional errors in series voltage summation of transformers are analyzed. The passive linear three-port network voltage proportional-value model in which additional errors are taken into consideration is established based on the series voltage summation of two-stage transformers. The output response of the three-port network model is proved to possess linear superposition by circuit theory. Then

in the

process of solving voltage coefficient

the new three-step recursive measurement method and iterative algorithm are proposed based on the traditional series summation. Derivation proves that this method can be adopted to eliminate the influences of shielding leakage and adjacent interference. Finally

for the same 110/

1/2

3 kV voltage transformer

the two-stage transformer series method proposed in this paper is compared with the German physikalisch-technische bundesanstalt（PTB）. And for the same 220/

1/2

3 kV voltage transformer

the method in this paper is compared with the traditional series summation. The results show that the deviation of the international comparison is less than the ratio error of 2×10

–6

and the phase error of 2 μrad

and the two-stage transformer series method proposed in this paper is better than traditional summation method. This research can provide support for improving the accuracy of traceability of power frequency voltage ratio standard system in China.