A novel image-based approach for discrimination between internal faults and magnetizing inrush currents in power transformers

This paper presents a novel, simple but efficient, technique for power transformer protection. This technique is based on image analysis for identification of magnetizing inrush and internal fault condition in power transformers. Also, it can discriminate between faults on the primary winding or in the secondary winding. The technique depends on building up the locus of the current at the supply side with the difference between the voltage signals at the primary and the secondary sides for power transformer. Usage of the voltages minimizes the effect of current transformer saturation. The discrimination is achieved by comparing the length of locus boundary of interest with the length of locus boundary of normal condition. The proposed technique is evaluated via an extensive simulation study for a 132/11-KV power transformer using alternative transient program (ATP). The obtained results verify accurate and fast operation for discriminating between internal and magnetizing inrush currents as well as identifying the faulty winding.