| 摘要 |
FIELD: electrical engineering. ^ SUBSTANCE: proposed device comprises 1st, 2nd and 3rd current-to-voltage converters connected to A, B, C phases of current transformers on high-voltage side of protected transformer; 1st, 2nd, and 3rd rectifiers; maximum selector, threshold device, reference voltage source, time relay, intermediate relay. In compliance with this invention, it incorporates additionally 1st, 2nd and 3rd subtractors; 4th, 5th, 6th, 7th, 8th and 9th rectifiers; 1st, 2nd, 3rd and 4th amplifiers; 1st, 2nd, and 3rd adders; minimum selector, divider, AND element, OR-NO element and power direction relay of reverse sequence. Proposed device allows detecting remote two-phase short-circuits that feature currents lower than rated currents of protected transformers. Besides it rules out breakage of transformer switching circuitry caused by short-circuits in case pain protection fails. ^ EFFECT: higher sensitivity of backup protection to two-phase short-circuits. ^ 1 dwg |
