METHOD OF DIFFERENTIAL PROTECTION OF POWER TRANSFORMER FROM TURN FAULTS Russian patent published in 2018 - IPC H02H7/04 

FIELD: electrical engineering.

SUBSTANCE: according to a method, the formation of a control action on the trip is made in the event of exceeding the differential current of the pickup setting, wherein the value of this set point increases (decreases) with the growth (decrease) in the given range of the brake signal proportional to the sum of the currents of the differential protection arms, and the absence in the differential current of a second harmonic component above a predetermined threshold value, determining the percentage of the second harmonic component to a fundamental harmonic. In the case of a significant increase in the brake signal with a relatively small increase in the differential current, a prohibition is imposed on the formation of a control action on the disconnection for a time sufficient to eliminate damage outside the protection zone. Emergency mode is also determined, when in the rectified differential current, the absence during a given time of dead times having a duration greater than the set point is recorded, provided that a power transformer is idling, and the value of the set point according to the time duration of the dead time is set based on the current frequency of overexcitation taking into account the integrity of the measuring voltage circuits.

EFFECT: increase in the sensitivity of the differential protection of the power transformer to turn faults in overexcitation mode.

1 cl, 1 dwg