Adaptive Numerical Differential Protection for Transformer Considering CT Saturation and HIF

The transformer is one of a power system's most crucial and pricey components. In this research paper, differential protection is worked out considering CT saturation & different fault conditions like internal, external, and high impedance (HIF) faults on Y-Y configured transformer. The dual-slope differential relay characteristic is tested with the operational quantity derived from the Fast Fourier Transform (FFT) technology. The system is designed with the selection of proper parameters like CT ratio, line current, line voltage, transformer rating, voltage ratio of the transformer, impedance parameter, input source, infinite bus, types of faults, breakers, relay parameter, FFT analyzer, etc. A model is built-in the PSCAD software with the biased differential mechanism of the transformer protection. The transformer differential protection technique that has been presented only works for internal faults, such as phase and ground faults. The proposed system does not function in the presence of any transformer outside faults or under typical load conditions. A protection scheme must be activated in case of a High Impedance Zone Fault (HIF) and it remains uninterrupted during CT saturation for external fault. The CT saturation is detected based on the zero crossing time of current waveforms. The adopted relay characteristic automatically changes in case of CT saturation detection. The outcome of this work demonstrates the effectiveness of the presented biased differential protection scheme.