Vector algebraic analysis method for inductive current transformers error
MU Xiaoxing1,2
(1.Jiangsu Electrical Power Company Research Institute, Nanjing 210019, China；2.State Grid Key Laboratory of Electrical Power Metering, Nanjing 210019, China)
 

Abstract: Aiming at the proldem of illogical theory, vague conclusion, and unclear expression in an electromagnetic CT error model based on vector geometry error modeling reported in literature, an complex error mathematic model for transformer was developed based on vector algebra analytic method by utilizing transformer CT equivalent circuit model and the theory on circuit & measurement error. Based on different algebra expressions for complex error, formula for the ratio difference and the angular difference of the transformer were rationally derived, the error characteristics and the influencing factors of the CT transformer, the error effect of the transformer operating state, and the additional error to the electric energy measurement were analyzed systematically and quantitatively. The results show that the vector algebra modeling and analytic method is a simple, rigorous, and logical method for transformer error analysis, and can be applied to voltage drop of the VT secondary circuit too. The proposed method, therefore, can enhance the error theory of electromagnetic transformer, and establish a theoretical basis for the indirect measuring method of calibrating high voltage transformers with low measuring voltage for computer simulations.
Key words: current transformer error; error model; CT; ratio difference; angular difference; impedance phase angle; vector algebraic analysis