{"schemaVersion":1,"slug":"ansi-reverse-current-relay","name":"ANSI/IEEE Reverse-current measuring relay form","kind":"symbol","abbreviation":"K","aliases":["HCR1F28","VCR1F28","IEEE Come Back Current Protection","ANSI Reverse-current measuring relay"],"category":"measurement-protection","drawingTypes":["Schematic","SLD"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"IEEE-library form of reverse-current measuring relay: measuring relay that operates when current flows in the opposite direction to normal, such as back-feed into a DC source.","description":["This reference locates reverse-current measuring relay in Autodesk's IEEE-oriented current protection relays family. 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. The public library uses HCR1F28 for its horizontal representation; this is a vendor block name, not an IEEE standards symbol number.","Trace the measured quantity or initiating control signal separately from the output contacts. The device tag links the sensing or operating element to the controlled circuit; settings, reset behaviour and the actual terminal arrangement belong in the selected equipment documentation.","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. Identify which direction is treated as normal for the source. A reverse-current relay responds to current direction; a maximum-current relay responds to magnitude regardless of direction. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted."],"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":"Convention evidence","value":"Autodesk IEEE Symbol Preview: Current Protection Relays; published form: Come Back Current Protection."},{"label":"Public vendor block","value":"HCR1F28. Vendor library token, not an IEEE symbol number."},{"label":"Measured quantity","value":"Current direction relative to normal flow"},{"label":"Preview","value":"Independent educational concept; consult the publisher and applicable standard for the exact graphic"},{"label":"Artwork scope","value":"Original educational geometry. Exact standard graphics, product ratings and terminal pinouts are not certified."}],"references":[{"sourceId":"s28-ieee-current-protection-relays","relevance":"Public IEEE-oriented Current Protection Relays table explicitly lists HCR1F28 as Come Back Current Protection. This supports the vendor convention context, not reproduction of the publisher graphic."},{"sourceId":"iec-diagrams","relevance":"IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced."}],"related":["reverse-current-relay","maximum-current-monitoring-relay","32-directional-power","directional-measuring-element-qualifier"],"artwork":"s28-ansi-reverse-current-relay","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEEE / ANSI","form":"Come Back Current Protection","reference":"Autodesk IEEE Symbol Preview: Current Protection Relays, block HCR1F28. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier.","counterpart":"reverse-current-relay"},"plainEnglish":{"title":"What does ANSI/IEEE Reverse-current measuring relay form mean?","introduction":"This reference locates reverse-current measuring relay in Autodesk's IEEE-oriented current protection relays family. 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. The public library uses HCR1F28 for its horizontal representation; this is a vendor block name, not an IEEE standards symbol number.","example":"Trace the measured quantity or initiating control signal separately from the output contacts. The device tag links the sensing or operating element to the controlled circuit; settings, reset behaviour and the actual terminal arrangement belong in the selected equipment documentation.","drawings":"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. Identify which direction is treated as normal for the source. A reverse-current relay responds to current direction; a maximum-current relay responds to magnitude regardless of direction. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted.","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":"Autodesk IEEE Symbol Preview: Current Protection Relays","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EC11EC4D-374C-4191-9534-C802D3932711.htm"},{"label":"IEC graphical symbols for diagrams","url":"https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/"}],"detail":"IEEE-library form of reverse-current measuring relay: 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/ansi-reverse-current-relay","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/ansi-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":"s28-ieee-current-protection-relays","title":"Autodesk IEEE Symbol Preview: Current Protection Relays","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EC11EC4D-374C-4191-9534-C802D3932711.htm","type":"cad-reference","scope":"Public current protection relays family names and vendor block tokens. Horizontal, vertical and rotated placements are not separate engineering functions. Exact standard geometry is not reproduced.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Public IEEE-oriented Current Protection Relays table explicitly lists HCR1F28 as Come Back Current Protection. This supports the vendor convention context, not reproduction of the publisher graphic."},{"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."}]}