METHOD OF EXTRACTION OF EMERGENCY COMPONENT OF SHORT-CIRCUIT CURRENT Russian patent published in 1995 - IPC

FIELD: relay protection. SUBSTANCE: method includes only simple operations realized by microprocessor equipment. Current is converted into digital signal, then into orthogonal components. Frequency of digitization of the latter is decreased in order to suppress oscillation of double grequency in them. After this they are let through nonrecursive filter meeting some special conditions. Its senior scaling multiplier should be equal to one, it should suppress continuous signal. Out of reading fed into it only the latter should be refered to emergency condition and all the rest - to preceding condition. That is why frequency of digitization of orthogonal signals reduces twofold prior to formation of each new reading of emergency component. It is proposed to record orthogonal components of preceding condition at moment closest to moment of short-circuit to avoid unauthenticity of first reading of emergency current. EFFECT: enhanced reliability of relay protection. 3 cl, 3 dwg