Field‐circuit coupling numerical calculation method of transformer remanence

Abstract

When the transformer is re-energised, the remanence in the core will cause inrush current, which will have adverse impacts on the power system. In the remanence distribution calculation, not only the hysteresis characteristics of the core, but also the characteristics of the external circuit need to be considered. In this paper, an indirect field-circuit coupling method for calculating transformer remanence distribution is presented. The residual flux density distribution at every point of the iron core, which has not been shown in previous literatures, can be obtained, and also the H-B trajectory of the iron core. In the field calculation, the pseudo-permeability method is modified in order to fit the field separation-based dynamic hysteresis model. The pseudo-permeability method and the initial value estimation method are used to speed up the iteration convergence. Furthermore, in the electric circuit topology used in the calculation, the switching process of the circuit breaker and the capacitance in the circuit are considered, and this has not been tried in the previous remanence calculation method. The remanence results are verified by comparison with the results in the literature. The remanence results can provide a basis for the impact analysis and phase control of the re-energisation.