{"schemaVersion":1,"slug":"reverse-current-relay","name":"Reverse-current measuring relay","kind":"symbol","abbreviation":"K","aliases":["come-back current protection relay","HCR1F28","reverse current relay"],"category":"measurement-protection","drawingTypes":["Schematic","SLD"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Measuring relay that operates when current flows in the opposite direction to normal, such as back-feed into a DC source.","description":["A reverse-current relay compares the direction of current with a reference and operates when current flows the wrong way. Classic uses are DC generators and battery chargers in parallel, where a failed source would otherwise draw current from the bus, and rectifier feeders where back-feed indicates a fault.","On the schematic the relay box carries a current quantity with a direction qualifier, and its contacts are drawn elsewhere in the trip or alarm circuit. The box does not show the pick-up level or time delay, and in AC systems the equivalent requirement is usually met with a directional power function rather than a simple current-direction element."],"readingNotes":["Identify which direction is treated as normal for the source.","Find the contacts that trip or disconnect the source."],"drawingChecklist":["State normal current direction","Give pick-up and delay","Reference the trip contact"],"distinction":"A reverse-current relay responds to current direction; a maximum-current relay responds to magnitude regardless of direction.","facts":[{"label":"Measured quantity","value":"Current direction relative to normal flow"},{"label":"Publisher reference token","value":"HCR1F28 (Autodesk identifier; not an IEC database ID)"},{"label":"Preview","value":"Independent educational concept; consult the publisher and applicable standard for the exact graphic"}],"references":[{"sourceId":"pub-symbol-current-relays","relevance":"Public AutoCAD Electrical relay listing that names the Come Back Current Protection block; the illustration is independently drawn."},{"sourceId":"iec-diagrams","relevance":"IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced."}],"related":["maximum-current-monitoring-relay","32-directional-power","directional-measuring-element-qualifier"],"artwork":"s28-reverse-current-relay","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Reverse-current measuring relay mean?","introduction":"A reverse-current relay compares the direction of current with a reference and operates when current flows the wrong way. Classic uses are DC generators and battery chargers in parallel, where a failed source would otherwise draw current from the bus, and rectifier feeders where back-feed indicates a fault.","example":"On the schematic the relay box carries a current quantity with a direction additional drawing mark, and its contacts are drawn elsewhere in the trip or alarm circuit. The box does not show the pick-up level or time delay, and in AC systems the equivalent requirement is usually met with a directional power function rather than a simple current-direction element.","drawings":"Identify which direction is treated as normal for the source. Find the contacts that trip or disconnect the source. A reverse-current relay responds to current direction; a maximum-current relay responds to magnitude regardless of direction.","terms":[{"name":"DC","meaning":"Direct current: electricity flowing in one direction."},{"name":"AC","meaning":"Alternating current: electricity whose direction changes periodically."},{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"AutoCAD Electrical: Current monitoring relays","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-E0DDA638-4664-4F1E-B191-29A4C40C4A0A.htm"},{"label":"IEC graphical symbols for diagrams","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/"}],"detail":"Measuring relay that operates when current flows in the opposite direction to normal, such as back-feed into a DC source. A reverse-current relay responds to current direction; a maximum-current relay responds to magnitude regardless of direction.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/reverse-current-relay","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/reverse-current-relay.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-symbol-current-relays","title":"AutoCAD Electrical: Current monitoring relays","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-E0DDA638-4664-4F1E-B191-29A4C40C4A0A.htm","type":"cad-reference","scope":"Public vendor catalogue naming and functional variants. Vendor block names are not IEC identifiers. Linked for reference; no graphics or CAD files are redistributed.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public AutoCAD Electrical relay listing that names the Come Back Current Protection block; the illustration is independently drawn."},{"id":"iec-diagrams","title":"IEC graphical symbols for diagrams","publisher":"IEC","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/","type":"standard","scope":"IEC 60617 and related symbol-design publications. Full database access requires a subscription.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced."}]}