Efficient method for discrimination between inrush current and internal faults in power transformers based on the non-saturation zone

There are many different techniques for discrimination between inrush current and internal faults. However, due to their inherent limitations, the methods have not reached a practical level yet, and the conventional methods are still widely employed in practice despite of their well-known shortcomings. Current transformer saturation and large inrush currents are the most reported cause of the discrimination algorithms mal-operation. This paper deals with an efficient approach to discriminate internal faults from switching conditions in the power transformers which can solve these problems. The proposed method is based on utilising the feature of the non-saturation zone. The performance of the proposed method is tested using the simulations data besides to data collected from a prototype laboratory three-phase power transformer. Also, the proposed method is evaluated and compared with some well-known discrimination schemes including conventional and some new presented schemes by the same simulation and experimental data sets. The results validate the consistency and accuracy of the proposed method.