Power transformer differential protection using S-transform and Support Vector Machine

This paper proposes a power transformer differential protection scheme combined with S-transform and Support Vector Machine (SVM) that distinguishes internal faults and non-internal faults/disturbances such as different kinds of inrushes, over-excitation condition and external fault. In the proposed scheme, feature vectors, generated by performing S-transform of differential currents of a power transformer, are used as an input to SVM to classify internal faults with the non-internal faults. The proposed scheme is validated by generating more than 12000 simulation cases containing internal faults, external faults and other disturbances by modeling 3-phase power transformer of Gujarat Energy Transmission Corporation Limited (GETCO), Gujarat, India with the help of PSCAD/EMTDC software. The scheme is implemented using MATLAB and the simulation results indicate that the proposed scheme is capable to discriminate different internal faults with the other non-internal faults effectively with an accuracy of more than 97%. Further, a relative assessment of the current scheme is performed with an another digital scheme based on Probabilistic Neural Network (PNN) and the results are found to be superior to the existing scheme.