{"schemaVersion":1,"slug":"loss-of-voltage-monitoring-relay","name":"Loss-of-voltage monitoring relay","kind":"symbol","abbreviation":"U LOSS","aliases":["HCR1F39","VCR1F39"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["Manufacturer"],"summary":"A loss-of-voltage relay changes its output for a documented absence-of-voltage condition.","description":["A loss-of-voltage relay changes its output for a documented absence-of-voltage condition. Schematics distinguish measurement failure, actual source loss and auxiliary-supply loss where the design requires them."],"readingNotes":["Trace the monitored voltage independently from relay auxiliary power.","The preview is an original explanation of this function. Match the actual drawing convention to its legend and the selected equipment documentation."],"drawingChecklist":["Identify monitored source","State loss criterion","Show output and supply-loss behaviour"],"distinction":"Loss-of-voltage indication is not necessarily the same function as breaker undervoltage release.","facts":[{"label":"Drawing role","value":"Monitoring element"},{"label":"Representation scope","value":"Functional concept; not an official standard graphic or a product footprint"},{"label":"Public vendor block reference","value":"HCR1F39, VCR1F39 (Autodesk identifiers; not IEC symbol numbers)"},{"label":"Identifier status","value":"The short label is a functional lookup label, not an assigned IEC or IEEE symbol number. Any separately listed Autodesk code is a verified vendor block name."}],"references":[{"sourceId":"pub-symbol-voltage-relays","relevance":"Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic."}],"related":["current-transformer","relay-coil"],"artwork":"edu-loss-of-voltage-monitoring-relay","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/symbols/loss-of-voltage-monitoring-relay","illustration":{"url":"https://eloragrid.ai/library/illustrations/loss-of-voltage-monitoring-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 documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic."}]}