{"schemaVersion":1,"slug":"ansi-loss-of-voltage-monitoring-relay","name":"ANSI/IEEE Loss-of-voltage monitoring relay form","kind":"symbol","abbreviation":"U LOSS","aliases":["HCR1F39","VCR1F39","IEEE Lack of Voltage Protection","ANSI Loss-of-voltage monitoring relay"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"IEEE-library form of loss-of-voltage monitoring relay: a loss-of-voltage relay changes its output for a documented absence-of-voltage condition.","description":["This reference locates loss-of-voltage monitoring relay in Autodesk's IEEE-oriented voltage protection relays family. 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. The public library uses HCR1F39 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.","Trace the monitored voltage independently from relay auxiliary power. Loss-of-voltage indication is not necessarily the same function as breaker undervoltage release. The linked functional counterpart explains the same operating role in its own drawing context; agreement of every detailed convention mark is not asserted."],"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":"Convention evidence","value":"Autodesk IEEE Symbol Preview: Voltage Protection Relays; published form: Lack of Voltage Protection."},{"label":"Public vendor block","value":"HCR1F39. Vendor library token, not an IEEE symbol number."},{"label":"Drawing role","value":"Monitoring element"},{"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."},{"label":"Artwork scope","value":"Original educational geometry. Exact standard graphics, product ratings and terminal pinouts are not certified."}],"references":[{"sourceId":"s28-ieee-voltage-protection-relays","relevance":"Public IEEE-oriented Voltage Protection Relays table explicitly lists HCR1F39 as Lack of Voltage Protection. This supports the vendor convention context, not reproduction of the publisher graphic."}],"related":["loss-of-voltage-monitoring-relay","current-transformer","relay-coil"],"artwork":"s28-ansi-loss-of-voltage-monitoring-relay","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","symbolVariant":{"convention":"IEEE / ANSI","form":"Lack of Voltage Protection","reference":"Autodesk IEEE Symbol Preview: Voltage Protection Relays, block HCR1F39. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier.","counterpart":"loss-of-voltage-monitoring-relay"},"plainEnglish":{"title":"What does ANSI/IEEE Loss-of-voltage monitoring relay form mean?","introduction":"This reference locates loss-of-voltage monitoring relay in Autodesk's IEEE-oriented voltage protection relays family. 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. The public library uses HCR1F39 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":"Trace the monitored voltage independently from relay auxiliary power. Loss-of-voltage indication is not necessarily the same function as breaker undervoltage release. 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":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Coil","meaning":"A wound conductor that can produce a magnetic field when energised."},{"name":"Terminal","meaning":"An identified point where a conductor connects."}],"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: Voltage Protection Relays","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5D942536-ADE3-43EA-8280-CC7907C38F15.htm"}],"detail":"IEEE-library form of loss-of-voltage monitoring relay: a loss-of-voltage relay changes its output for a documented absence-of-voltage condition. Loss-of-voltage indication is not necessarily the same function as breaker undervoltage release.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/ansi-loss-of-voltage-monitoring-relay","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/ansi-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":"s28-ieee-voltage-protection-relays","title":"Autodesk IEEE Symbol Preview: Voltage Protection Relays","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5D942536-ADE3-43EA-8280-CC7907C38F15.htm","type":"cad-reference","scope":"Public voltage 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 Voltage Protection Relays table explicitly lists HCR1F39 as Lack of Voltage Protection. This supports the vendor convention context, not reproduction of the publisher graphic."}]}