Mitigation of Magnetizing Inrush Current for Unloaded Three Phase Electrically Coupled Power Transformers involving Remanence Effect using Distributed Asymmetrical Winding Configuration

Abstract

This paper demonstrates a novel approach to mitigate the magnetizing inrush current of a coupled unloaded transformer to a considerable extent having had the residual magnetism present in its core  with the aid of a modern distributed asymmetrical winding configuration alike from the conventional methods. The proposed method has been analyzed on Power transformer with different configuration of winding, core design arrangement while feeding from the mains to star and delta side of transformer individually. The instant of plugging with circuit breakers affecting the performance characteristics of transformer has also been elaborated. The proposed method is verified by the simulation in PSCAD environment on a practical transformer of 30 MVA, 27/ 132 kV, three units of single phase transformer connected in star and delta configuration. The simulated results show a good agreement in mitigation of magnetizing inrush current to small percentage of rated full load current.  So, the above said method can be applied in practical field as the magnitudes of magnetizing inrush currents can be estimated before manufacturing of transformer.

Keywords: Distributed winding, magnetizing inrush current, inrush analogous inductance, air core reactance