On the Correctness of Error Approximation in Calibration of Instrument Transformer

International standards for instrument transformers in interpreting definitions of ratio error and phase displacement allows simplification in vector analysis. This paper is devoted to finding the limits of the correctness of applying approximations when estimating errors of instrument transformers. The dependence of the difference between the obtained results of the error determination is considered on the example of current transformers, both without the use of approximation and with its application. In particular, the case, where the proposed approximation leads to a significant discrepancy between the simulated measurement results, is outlined.