FIELD: electrical engineering; overcurrent and short-circuit relay protective gear. SUBSTANCE: electromagnetic current relay incorporating saturable current transformer functions to shape current whose magnitude and direction characterize kind of fault and line where mentioned fault occurred. Faulty line is detected by means of intervening potential transformer and two power direction relays whose windings carry currents characterizing magnitude and direction of sum of phase voltages across substation buses and sum of differential phase currents of lines. Proposed method provides for recording all kinds of faults in parallel lines using only one electromagnetic current relay and two power direction relays. Signal indicating resultant sum of phase voltages used to inform about voltage across substation buses is produced by means of intervening potential transformer wherein voltage dead zone is eliminated by changing number of winding turns and resonance-tuned circuits. EFFECT: simplified design, reduced power requirement, improved sensitivity throughout entire length of line under protection. 6 cl, 3 dwg
