A new algorithm for three-phase power transformer differential protection considering effect of ultra-saturation phenomenon

A transient phenomenon that leads to the false trip of the power transformer differential protection during the energization of a loaded power transformer is the ultra-saturation phenomenon. in this paper, at first, a new algorithm for three-phase power transformer differential protection, considering the effect of the ultra-saturation phenomenon, is presented. to model the ultra-saturation phenomenon, the nonlinear characteristic of the transformer core and the effect of saturation of the current transformers are taken into account. it is assumed that the load of the transformer is resistive and inductive. in this algorithm, the ultra-saturation phenomenon, external and internal faults of the power transformer and magnetic inrush current are simulated, and appropriate criteria using the signal harmonic components of the differential current will be presented for the discrete fourier transform (dft) algorithm to distinguish between. in this paper, simulation is done by pscad and matlab programs.