TITLE:
Alternative Approaches for Distinguishing between Faults and Inrush Current in Power Transformers
AUTHORS:
Ahmed M. A. Alomar, Bakr E. M. Shamseldin
KEYWORDS:
Power Transformer, Inrush Current, Differential Relay
JOURNAL NAME:
Energy and Power Engineering,
Vol.6 No.7,
July
8,
2014
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.