METHOD OF RELAY PROTECTION OF THREE-PHASE TRANSFORMER Russian patent published in 2018 - IPC H02H7/45 

FIELD: electricity.

SUBSTANCE: use in electric power engineering. Operations of the method are oriented to the most common type of power transformers with primary windings connected in the "star with zero" scheme and secondary windings connected in a triangle. Currents and voltages of the primary windings and currents at the output of the triangle of the secondary windings are monitored. Monitored values are converted into two-dimensional signals using the intact transformer model, which is divided into three sub-models – primary windings, secondary windings and magnetic circuit. In the first submodel, the primary currents and voltages are converted into magnetizing voltages. In the second submodel, the magnetizing voltages are converted together with the secondary side currents of the transformer into the currents of its secondary windings. Third submodel implements the law of total current, transforming the currents of the primary and corresponding secondary windings of each phase into magnetizing currents. Two-dimensional signals are formed from voltages and magnetizing currents. On the planes of two-dimensional signals, the characteristics of the protection blocking are set, which play a priority role in this method. Protection is triggered if two conditions are met: the first is the failure of any of the blocking organs; the second is the activation of at least one of the permissive organs.

EFFECT: expansion of the functionality of the method.

1 cl, 12 dwg