# ANSI/IEEE Minimum-impedance measuring relay form Canonical URL: https://eloragrid.ai/symbols/ansi-minimum-impedance-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: Minimum Impedance Relay Autodesk IEEE Symbol Preview: Miscellaneous Relays, block HCR1F41. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier. Related representation: [Minimum-impedance measuring relay](https://eloragrid.ai/symbols/minimum-impedance-relay) IEEE-library form of minimum-impedance measuring relay: measuring relay that compares voltage with current and operates when the apparent impedance falls below a set value. ## In plain English ### What does ANSI/IEEE Minimum-impedance measuring relay form mean? This reference locates minimum-impedance measuring relay in Autodesk's IEEE-oriented miscellaneous relays family. A minimum-impedance relay divides measured voltage by measured current and operates when the result falls below its setting, indicating a fault close enough to fall inside its reach. It is used as generator and transformer backup protection and is the basic idea behind distance protection. The public library uses HCR1F41 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 needs both CT and VT inputs, so the symbol should always be read with both connections. It does not show the characteristic shape on the impedance plane, any directional element, or the loss-of-voltage blocking needed to avoid operation when the VT supply fails. Confirm both voltage and current inputs are shown. A minimum-impedance relay uses voltage and current together; an overcurrent relay uses current alone. 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 minimum-impedance measuring relay: measuring relay that compares voltage with current and operates when the apparent impedance falls below a set value. A minimum-impedance relay uses voltage and current together; an overcurrent relay uses current alone. ### Terms - Winding: A coil of conductor inside an electrical machine or transformer. - 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. 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: Miscellaneous Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-DA549E3E-4ABB-426E-9331-0226EF55EAA7.htm) - [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) ## What it represents This reference locates minimum-impedance measuring relay in Autodesk's IEEE-oriented miscellaneous relays family. A minimum-impedance relay divides measured voltage by measured current and operates when the result falls below its setting, indicating a fault close enough to fall inside its reach. It is used as generator and transformer backup protection and is the basic idea behind distance protection. The public library uses HCR1F41 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 needs both CT and VT inputs, so the symbol should always be read with both connections. It does not show the characteristic shape on the impedance plane, any directional element, or the loss-of-voltage blocking needed to avoid operation when the VT supply fails. Confirm both voltage and current inputs are shown. A minimum-impedance relay uses voltage and current together; an overcurrent relay uses current alone. 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 - Confirm both voltage and current inputs are shown. - Check for VT fuse-failure blocking. ## Information to show or reference - Show CT and VT inputs - State reach and delay - Reference blocking logic ## Important distinction A minimum-impedance relay uses voltage and current together; an overcurrent relay uses current alone. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Miscellaneous Relays; published form: Minimum Impedance Relay. - Public vendor block: HCR1F41. Vendor library token, not an IEEE symbol number. - Measured quantity: Apparent impedance from voltage and 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: Miscellaneous Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-DA549E3E-4ABB-426E-9331-0226EF55EAA7.htm) — Autodesk. Public IEEE-oriented Miscellaneous Relays table explicitly lists HCR1F41 as Minimum Impedance Relay. This supports the vendor convention context, not reproduction of the publisher graphic. - [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced. ## 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.