Alternative Approaches for Distinguishing between Faults and Inrush Current in Power Transformers

Ahmed M. A. Alomar, Bakr E. M. Shamseldin

Electrical Networks Department, Public Authority for Applied Education and Training, Adailiyah, Kuwait.

DOI: 10.4236/epe.2014.67014                

Abstract

In this study, we will cover the basic methods used to distinguish between inrush current and fault current in power transformers. First, the nature of inrush current is presented compared to the fault current. Then the nature of the magnetizing current due to energizing a power transformer at no-load is explained. The first generation of methods used to disable the protective relay system during inrush current, namely the Desensitizing and Tripping Suppressor, is introduced. The second generation, the harmonic restraint method and the waveform-based restraint method with their different versions, is explained. Then we will explore thoroughly the fictitious equivalent resistance method as an example of the third generation of model type restraining or blocking methods. Finally, a comparison between these methods and conclusion is carried out.

Keywords

Power Transformer, Inrush Current, Differential Relay

Conflicts of Interest

The authors declare no conflicts of interest.

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