Patent ID: 7873496

Claim:
A method for fault detection in an n-winding, three-phase power transformer, the method comprising: for each winding (Wi, where i=1, . . . , n): measuring the three phase currents (I L1 — Wi ; I L2 — Wi ; I L3 — Wi ), deciding if a zero sequence current (I 0 — Wi ) reduction is to be performed depending on at least one user setting (k Wi ) and if so, deducting the zero sequence current (I 0 — Wi ) from each of the three phase currents (I L1 — Wi ; I L2 — Wi ; I L3 — Wi ), generating normalized currents by performing a magnitude compensation and a phase angle shift compensation on the results of the previous step, followed by for each phase (Lx, where x=1, 2, 3): comparing the normalized current of a single winding with the normalized currents of all other windings, and generating a fault signal, if a difference between the single winding and all other windings exceeds a predefined level.