SHORT-CIRCUIT PROTECTIVE DEVICE FOR PARALLEL AC POWER TRANSMISSION LINES Russian patent published in 2004 - IPC

FIELD: relay protection for cable and overhead ac power transmission lines with common circuit breaker per phase. SUBSTANCE: protective device has one differential current transformer per phase of power transmission line that incorporates two primary windings. Each phase is connected in series with one of two parallel power transmission lines being protected. Secondary winding of current transformer is connected to responding element of protective relay. Transformer primary windings are multiturn cross-over windings having equal turn number; they are differentially interconnected and wound on transformer magnetic core so that their turns in layer are alternating. EFFECT: enhanced sensitivity and reduced length of dead zone. 1 cl, 2 dwg