Laboratory investigation for power transformer protection technique based on positive sequence admittance approach

This paper presents a new digital technique for transformer protection. The technique uses the accumulated positive sequence admittances at the two sides of the power transformer. The instantaneous measurements of phase voltage and line current signals at the transformer terminals are used to calculate the accumulated positive sequence admittances. A 500/230-kV Y/Y transformer connected to a 230-kV power system is simulated using MATLAB/SIMIULINK tool. The method depends on stand alone decision at the two terminals of power transformer. A real-time investigation for power transformer in normal and abnormal conditions based on experimental setup is given. The experimental setup uses a transformer of (5 kVA, 220/110V) for testing purposes. The simulated and experimental results indicated that the proposed technique is stable, reliable, and fast during the discrimination between internal and external faults, magnetizing inrush currents, and switching on internal faults. Copyright (C) 2011 John Wiley & Sons, Ltd.