Power Transformer Differential Protection Through Gradient of the Differential Current

This paper presents a new methodology for identifying internal faults and inrush currents in power transformers based on the gradient of the differential current. The technique is to calculate the angle of the gradient vector along the curve of the differential current in the data window and through waveforms recognition techniques to identify the type of occurrence. The gradient vector of a function corresponds to a vector tangent to the curve at the point under consideration. The gradient vector, tomove along the curve of the differential current, changes its angle to the horizontal reference. The behavior of the gradient vector angle, through statistical calculations will be used to identify the occurrence of internal faults or the presence of inrush currents. The method was tested by simulating various types of internal and external faults and also several cases of inrush currents in a power transformer which is modeled by the EMTP/ATP software and also by implementing the algorithm in MATLAB (R), presenting highly satisfactory results.