DESIGN, IMPLEMENTATION AND TESTING OF A MICROPROCESSOR-BASED HIGH-SPEED RELAY FOR DETECTING TRANSFORMER WINDING FAULTS

This paper presents the design, implementation and testing of a microprocessor-based high-speed relay that correctly detects transformer winding faults. Instead of relying on the presence of harmonics to identify magnetizing inrush, it uses a non-linear model of the transformer to determine the state of its health. One version of the relay is suitable for protecting single-phase transformers, whereas another version is for protecting three-phase transformers. A three-phase delta-wye 15 kVA transformer was used to test the relay for a variety of operating conditions. The results show that the relay performs well.