Piecewise Linear Modeling for Inrush Safety Regions Detection and Its Validation Through a Preisach Model and Experimental Data

Abstract

An alternative modeling approach to detect the occurrence of Inrush currents in power transformers, is discussed. The inrush current phenomenon is affected by the core <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">residual</i> magnetizazion <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_r</i> and voltage source <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">initial phase</i> , θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , through which a region in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_r</i> – θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> plane where inrush currents doesn’t occur (named Inrush Safety Region - ISR) is defined. The approach is founded on the awareness that a fairly accurate description of the inrush process does not require a detailed description of core magnetization process, leading to the employment of a Piecewise linear magnetization model, able to detect in a straightforward way the ISR. The main advantage of the approach is to set up a fast algorithm for ISR detection, suitable for a real-time control. An accurate model of the transformer, based on a Preisach model magnetization algorithm has been exploited, along with a suitable set of experimental results allow to confirm the validity of the proposed identification approach.