Patent ID: 11887774
Assignee: nan
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A method for differential protection of a transformer under geomagnetically induced current (GIC), the method comprising:
receiving differential currents associated with the transformer;
outputting a high GIC signal where second harmonic phasors of the differential currents are in a negative-sequence format and at least one magnitude of the second harmonic phasors is greater than a magnitude threshold, or waveforms of three phases of the differential currents are all asymmetrical in a positive or negative direction, otherwise outputting a low GIC signal;
determining derivatives of the differential currents of three phases of the transformer;
outputting a high supplementary signal where at least one of the derivatives of the differential currents is greater than a supplementary threshold, otherwise outputting a low supplementary signal;
combining the GIC signal with the supplementary signal using NAND logic to determine a supplemented GIC signal;
combining the supplemented GIC signal with a second harmonic blocking signal using AND logic to determine a supplemented second harmonic blocking signal; and
outputting a trip signal for electrically tripping the transformer based on the supplemented second harmonic blocking signal.