PROJECT TITLE :

Enhanced Analytical Method for the Calculation of the Maximum Inrush Currents of Single-Phase Power Transformers

ABSTRACT:

During this paper, an correct analytical method is proposed to compute the utmost inrush currents for single-part transformers. The worst case eventualities for inrush currents caused by switching at the voltage zero crossing with the best doable residual flux are investigated. Hysteresis is modeled with piece-wise linear approximations. Hence, it is assumed that the transformer is always operating on linear sections of the magnetizing curve. The utmost inrush current is computed with simple steps from the solution of the linear governing differential equations. The tactic is simple and, therefore, suitable to be included in the transformer design program (or perhaps employing a calculator). Comprehensive studies are applied to evaluate the proposed method versus laboratory measurements and Electromagnetic Transients Program simulations. The results indicate a significant improvement from published formulae in the literature. The principal advantages of the technique are its accuracy and simplicity. A step-by-step numerical example illustrates how straightforward it's to estimate the most inrush currents.