TRANSFORMER BACKUP CURRENT PROTECTION DEVICE WITH HIGHER SENSITIVITY TO TWO-PHASE SHORT-CIRCUITS Russian patent published in 2010 - IPC H02H7/04 

FIELD: electrical engineering.

SUBSTANCE: proposed device comprises 1^st, 2^nd and 3^rd current-to-voltage converters connected to A, B, C phases of current transformers on high-voltage side of protected transformer; 1^st, 2^nd, and 3^rd rectifiers; maximum selector, threshold device, reference voltage source, time relay, intermediate relay. In compliance with this invention, it incorporates additionally 1^st, 2^nd and 3^rd subtractors; 4^th, 5^th, 6^th, 7^th, 8^th and 9^th rectifiers; 1^st, 2^nd, 3^rd and 4^th amplifiers; 1^st, 2^nd, and 3^rd 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