# ANSI/IEEE Earth-fault current relay form Canonical URL: https://eloragrid.ai/symbols/ansi-earth-fault-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: Ground Failure Current Protection Autodesk IEEE Symbol Preview: Current Protection Relays, block HCR1F37. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier. Related representation: [Earth-fault current relay](https://eloragrid.ai/symbols/earth-fault-current-relay) IEEE-library form of earth-fault current relay: measuring relay form that operates on current flowing to earth, fed from a residual connection or core-balance CT. ## In plain English ### What does ANSI/IEEE Earth-fault current relay form mean? This reference locates earth-fault current relay in Autodesk's IEEE-oriented current protection relays family. The earth-fault current relay form identifies a relay whose operating quantity is current flowing to earth. It may be fed from a core-balance CT around all live conductors, from the residual connection of three phase CTs, or from a CT in the star-point earth lead, and the source changes its achievable sensitivity. The public library uses HCR1F37 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 The relay box shows the quantity with an earth additional drawing mark but not the setting, characteristic or whether it is directional. In resistance-earthed and isolated networks earth-fault current is small and often needs a sensitive or directional element that must be stated separately. Identify the CT arrangement that supplies the residual current. An earth-fault current relay measures current to earth; an earth-fault voltage relay measures neutral displacement voltage. 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 earth-fault current relay: measuring relay form that operates on current flowing to earth, fed from a residual connection or core-balance CT. An earth-fault current relay measures current to earth; an earth-fault voltage relay measures neutral displacement voltage. ### Terms - Normally open / normally closed: The contact state in the normal condition defined for the drawing. - Coil: A wound conductor that can produce a magnetic field when energised. - Phase: One of the related AC waveforms in a power system. 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) ## What it represents This reference locates earth-fault current relay in Autodesk's IEEE-oriented current protection relays family. The earth-fault current relay form identifies a relay whose operating quantity is current flowing to earth. It may be fed from a core-balance CT around all live conductors, from the residual connection of three phase CTs, or from a CT in the star-point earth lead, and the source changes its achievable sensitivity. The public library uses HCR1F37 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. The relay box shows the quantity with an earth qualifier but not the setting, characteristic or whether it is directional. In resistance-earthed and isolated networks earth-fault current is small and often needs a sensitive or directional element that must be stated separately. Identify the CT arrangement that supplies the residual current. An earth-fault current relay measures current to earth; an earth-fault voltage relay measures neutral displacement voltage. 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 the CT arrangement that supplies the residual current. - Check whether the element is directional or sensitive. ## Information to show or reference - Show residual CT source - State setting and characteristic - Reference system earthing method ## Important distinction An earth-fault current relay measures current to earth; an earth-fault voltage relay measures neutral displacement voltage. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Current Protection Relays; published form: Ground Failure Current Protection. - Public vendor block: HCR1F37. Vendor library token, not an IEEE symbol number. - Measured quantity: Residual or earth-fault current - 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 HCR1F37 as Ground Failure Current Protection. This supports the vendor convention context, not reproduction of the publisher graphic. ## 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.