# ANSI/IEEE Loss-of-voltage monitoring relay form Canonical URL: https://eloragrid.ai/symbols/ansi-loss-of-voltage-monitoring-relay Publisher: Elora Grid Updated: 2026-10-28 Lookup label: U LOSS Drawing use: SLD, Schematic Reference families: IEEE / ANSI, Manufacturer ## Symbol convention Convention: IEEE / ANSI Form: Lack of Voltage Protection 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. Related representation: [Loss-of-voltage monitoring relay](https://eloragrid.ai/symbols/loss-of-voltage-monitoring-relay) IEEE-library form of loss-of-voltage monitoring relay: a loss-of-voltage relay changes its output for a documented absence-of-voltage condition. ## In plain English ### What does ANSI/IEEE Loss-of-voltage monitoring relay form mean? 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. ### 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 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. ### This particular reference 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. ### 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. - Terminal: An identified point where a conductor connects. 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: Voltage Protection Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5D942536-ADE3-43EA-8280-CC7907C38F15.htm) ## What it represents 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. ## How to read it - 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. ## Information to show or reference - Identify monitored source - State loss criterion - Show output and supply-loss behaviour ## Important distinction Loss-of-voltage indication is not necessarily the same function as breaker undervoltage release. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Voltage Protection Relays; published form: Lack of Voltage Protection. - Public vendor block: HCR1F39. Vendor library token, not an IEEE symbol number. - Drawing role: Monitoring element - Identifier status: 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. - Artwork scope: Original educational geometry. Exact standard graphics, product ratings and terminal pinouts are not certified. ## Public references - [Autodesk IEEE Symbol Preview: Voltage Protection Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5D942536-ADE3-43EA-8280-CC7907C38F15.htm) — Autodesk. 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. ## 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.