{"schemaVersion":1,"slug":"earth-fault-voltage-relay","name":"Earth-fault voltage relay","kind":"symbol","abbreviation":"K","aliases":["ground failure voltage protection","frame leakage voltage relay","HCR1F31"],"category":"measurement-protection","drawingTypes":["Schematic","SLD"],"referenceFamilies":["IEC","Manufacturer"],"summary":"Relay form that operates on a voltage appearing because of an earth fault, such as between a frame and earth.","description":["This relay measures a voltage that appears only when there is an earth fault, for example between exposed metalwork and a reference earth, or across a neutral earthing impedance. It is useful where earth-fault current is limited and a voltage is easier to detect than a current.","The symbol does not say where the voltage is measured. A relay across a neutral earthing resistor and one connected between frame and auxiliary earth electrode have very different settings, so the measurement points must be drawn and labelled."],"readingNotes":["Trace both measurement connections of the relay.","Check the reference earth used by the relay."],"drawingChecklist":["Show measurement points","State threshold and delay","Reference earthing arrangement"],"distinction":"An earth-fault voltage relay measures fault-related voltage; a residual voltage relay measures zero-sequence voltage from VT windings.","facts":[{"label":"Measured quantity","value":"Voltage caused by an earth fault"},{"label":"Publisher reference token","value":"HCR1F31 (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-voltage-relays","relevance":"Public AutoCAD Electrical relay listing that names the Ground Failure Voltage Protection block; the illustration is independently drawn."},{"sourceId":"pub-symbol-earth-fault","relevance":"Public context for neutral-earthing and earth-fault protection."}],"related":["residual-voltage-monitoring-relay","earth-fault-current-relay","64-ground-detector-protection"],"artwork":"s28-earth-fault-voltage-relay","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Earth-fault voltage relay mean?","introduction":"This relay measures a voltage that appears only when there is an earth fault, for example between exposed metalwork and a reference earth, or across a neutral earthing impedance. It is useful where earth-fault current is limited and a voltage is easier to detect than a current.","example":"The symbol does not say where the voltage is measured. A relay across a neutral earthing resistor and one connected between frame and auxiliary earth electrode have very different settings, so the measurement points must be drawn and labelled.","drawings":"Trace both measurement connections of the relay. Check the reference earth used by the relay. An earth-fault voltage relay measures fault-related voltage; a residual voltage relay measures zero-sequence voltage from VT windings.","terms":[{"name":"Coil","meaning":"A wound conductor that can produce a magnetic field when energised."},{"name":"Rating","meaning":"A value stating the conditions for which equipment is specified."},{"name":"Schematic","meaning":"A drawing showing function and connections rather than physical appearance."}],"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: Voltage monitoring relays","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5296749E-9336-4B07-9956-160963D6C848.htm"},{"label":"Residual current and neutral-earthing protection context","url":"https://new.abb.com/medium-voltage/digital-substations/campaigns/earth-fault-protection-portfolio/earth-fault-offering"}],"detail":"Relay form that operates on a voltage appearing because of an earth fault, such as between a frame and earth. An earth-fault voltage relay measures fault-related voltage; a residual voltage relay measures zero-sequence voltage from VT windings.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/earth-fault-voltage-relay","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/earth-fault-voltage-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-voltage-relays","title":"AutoCAD Electrical: Voltage monitoring relays","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5296749E-9336-4B07-9956-160963D6C848.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 Ground Failure Voltage Protection block; the illustration is independently drawn."},{"id":"pub-symbol-earth-fault","title":"Residual current and neutral-earthing protection context","publisher":"ABB","url":"https://new.abb.com/medium-voltage/digital-substations/campaigns/earth-fault-protection-portfolio/earth-fault-offering","type":"manufacturer","scope":"Public manufacturer explanation of the equipment function and selection context.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public context for neutral-earthing and earth-fault protection."}]}