The Effect of Winding Potentials on Voltage Transformer Errors

A method is presented for determining the effect of winding potentials on voltage transformer errors. The transformer is represented as a 5-terminal network and equations are developed which give the variation of error in terms of easily measured coefficients. Measurements on actual transformers are described which indicate that the method yields the error variation to an accuracy of about 10%. Examples are given of the magnitude of error variation which may be expected when a transformer is used for line-to-line voltage measurement in a 3-phase system.