FAULT IDENTIFICATION SYSTEM FOR USE IN PROTECTIVE RELAYS FOR POWER TRANSMISSION LINES

摘要

The angle between the negative sequence andzero sequence currents for a power signal on atransmission lute is measured and compared against aplurality of successive angle ranges from 0° to 360°.If the angle is 0° ~ 30°, an AG fault is indicated anda first section output is produced blocking groundelements BG and CG and phase-to-phase elements AB andCA. Art angle of 120° ~ 30° indicates a BG fault,resulting in a second output blocking ground elements AGand CG and phase-to-phase elements AB and CG, while aphase angle of 240° ~ 30° indicates, a CG fault,resulting in a third output blocking ground elements AGand BG and phase-to-phase elements BC and CA. If thephase angle is not covered by the above three primaryranges, then a second stage of comparisons arc made,including determining the magnitudes of the phase-to-phasedistance elements, and then comparing the phase-to-phaseresistance of the lowest of those with theapparent resistance of the one ground element, i.e, AG,BG or CG, associated with the non-primary (secondary)range of angles which includes the measured phase angle.If selected criteria are met, then an output is assertedto block the ground and phase-to-phase elements notedabove associated with that ground element.