ATTENUATION OF TRANSFORMER INRUSH CURRENT USING CONTROLLED SWITCHING SYSTEM ON DELTA-STAR TRANSFORMER

Abstract

Reduction and methods of control of switching transients have become important concerns to the power industry. Power transformers are vital components in electric power system. This thesis presents a technique for attenuation of transformer inrush current. The proposed technique is applied to 66/11.5 kV, 25 MVA power transformer with delta connected winding using ATP-EMTP software. The main idea of the proposed technique is using controlled transformer energization preceded by controlled de-energization to achieve a defined and repeatable residual flux with its lowest possible level for individual phases, and then determine the optimal instant of energization considering the core residual flux.