METHOD OF FORMATION AND ADJUSTMENT OF TRANSFORMER AND AUTOTRANSFORMER DIFFERENTIAL CURRENT PROTECTION Russian patent published in 2008 - IPC H02H7/04 

FIELD: electricity.

SUBSTANCE: individual differential current protections are formed for every electrically connected double-ended or multi-ended winding of each phase and modified common differential current protection of transformer (autotransformer). It provides individual differential current protections to be tuned out of magnetisation current rush by differential-circuit way as of through current. It considerably improves their sensitivity without taking any actions reducing natural operation speed of differential principle and provides required high-speed (practically instant) short circuit clearing in windings of protected transformer (autotransformer). Higher sensitivity is stipulated as well due to the fact that formation of individual differential current protections is accompanied with application of single-type current sensors and current slowing-down of current sensors, switched-in coil ends of power transformers and autotransformers. Nonresponsiveness of individual differential current protections of windings to inter-winding short-circuits causes necessity of conservation of overall applied common differential current protection of transformers and autotransformers with all attributes of sensitivity increase: flattening of circulation circuit leg currents, slowing-down of specified leg currents, difference control of magnetisation current rush, as consequence, protection delay. However this disadvantage of common differential current protection in offered method is benign, as this protection channel is designed for uncommon inter-winding short-circuits with distinctly less currents compared to short circuit currents in windings. To reduce magnetisation current rush and increase sensitivity, formation of common differential current protection is based on single-type current sensors connected in cut current circulation circuit leg of individual differential current protections.

EFFECT: higher speed and sensitivity of differential current protection of transformers and autotransformers at short circuits in windings.

1 dwg