# ANSI/IEEE Reverse-current measuring relay form Canonical URL: https://eloragrid.ai/symbols/ansi-reverse-current-relay Publisher: Elora Grid Updated: 2026-10-28 Lookup label: K Drawing use: Schematic, SLD Reference families: IEEE / ANSI, Manufacturer ## Symbol convention Convention: IEEE / ANSI Form: Come Back Current Protection 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. Related representation: [Reverse-current measuring relay](https://eloragrid.ai/symbols/reverse-current-relay) 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. ## In plain English ### What does ANSI/IEEE Reverse-current measuring relay form mean? 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. ### A simple 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. ### What the drawings help you do 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. ### This particular reference 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. ### Terms - DC: Direct current: electricity flowing in one direction. - AC: Alternating current: electricity whose direction changes periodically. - Normally open / normally closed: The contact state in the normal condition defined for the drawing. Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram. - [Autodesk IEEE Symbol Preview: Current Protection Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EC11EC4D-374C-4191-9534-C802D3932711.htm) - [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) ## What it represents 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. ## How to read it - Identify which direction is treated as normal for the source. - Find the contacts that trip or disconnect the source. ## Information to show or reference - State normal current direction - Give pick-up and delay - Reference the trip contact ## Important distinction A reverse-current relay responds to current direction; a maximum-current relay responds to magnitude regardless of direction. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Current Protection Relays; published form: Come Back Current Protection. - Public vendor block: HCR1F28. Vendor library token, not an IEEE symbol number. - Measured quantity: Current direction relative to normal flow - Preview: Independent educational concept; consult the publisher and applicable standard for the exact graphic - Artwork scope: Original educational geometry. Exact standard graphics, product ratings and terminal pinouts are not certified. ## Public references - [Autodesk IEEE Symbol Preview: Current Protection Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EC11EC4D-374C-4191-9534-C802D3932711.htm) — Autodesk. 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. - [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced. ## Graphic scope Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.