FIELD: relay protection; line backup protective gear.
SUBSTANCE: proposed protective gear depends for its operation on detection of maximal and minimal phase currents, evaluation of difference between maximal and minimal values, and comparison of this difference with double value of minimal current. To this end protective gear has three current-to-voltage converters for phases A, B, C made in the form of transformer-reactor with first and second secondary windings, electrical quantity comparison unit, time relay, and subtracter. Newly introduced in protective gear are maximum selector, minimum selector, and reference value generator.
EFFECT: enhanced sensitivity of backup protective gear.
1 cl, 1 dwg
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