AC RELAY Russian patent published in 1997 - IPC

FIELD: electrical engineering relay protection and automatic control of power systems. SUBSTANCE: relay incorporating input current changer, setting signal shaper, two amplitude detectors, subtracter, and majority element has its mentioned shaper built up of controlled square-pulse generator and two delay elements, the latter of them being connected to parallel-interconnected pulse rise and fall time shapers, respectively, its both detectors are of positive polarity, and introduced in addition are dual-channel analog switch with direct and inverted inputs and outputs for each channel with separate setting inputs, as well as second majority element with inverted first and second inputs and feedback for third input. Setting-signal unit functions to control detectors (output of pulse shapers) and switch (outputs of generator and first delay element). Switch inputs are connected to detector outputs, and relatively offset signals proportional to input current amplitude are built up across its first and second outputs (combined outputs of channels). Difference of these signals across subtracter output is proportional to rate of change of mentioned amplitude. Relay has logic outputs according to relay functions and rate of change of its amplitude as well as according to outputs of majority elements and also it has analog outputs (switch and subtracter outputs). EFFECT: improved sensitivity and enlarged functional capabilities of relay. 2 dwg