Sequence component of currents based differential protection of power transformer

Day by day reliability is more concern with electricity issues and transformer itself is most important equipment in supplying electricity. Discrimination between inrush current, CT saturation, external fault and internal fault is required for necessary operation of power transformer. Also the mal-operation of transformer protective scheme during external fault and inrush condition should be minimized for continuous operation of transformer. This paper adopts new methodology to discriminate internal fault and external fault condition using sequence component of current from both side of transformer. Magnitude and phase angle of current signals are calculated using Fast Fourier Transform (FFT) which is further used to calculate sequence component of current. A differential protection principal is carried out with calculated magnitude and phase angle of sequence component of current to identify internal and external fault condition of transformer. Various internal and external fault cases are simulated in PSCAD including magnetizing inrush, high resistance fault and CT saturation conditions. The proposed method perfectly discriminates internal and external fault condition and proved to be well efficient for protection of transformer.