# ANSI/IEEE Differential-current measuring relay form Canonical URL: https://eloragrid.ai/symbols/ansi-differential-current-measuring-relay Publisher: Elora Grid Updated: 2026-10-28 Lookup label: I DIFF Drawing use: SLD, Schematic Reference families: IEEE / ANSI, Manufacturer ## Symbol convention Convention: IEEE / ANSI Form: Differential Current Protection Autodesk IEEE Symbol Preview: Current Protection Relays, block HCR1F29. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier. Related representation: [Differential-current measuring relay](https://eloragrid.ai/symbols/differential-current-measuring-relay) IEEE-library form of differential-current measuring relay: a differential-current relay responds to the relationship between specified current inputs. ## In plain English ### What does ANSI/IEEE Differential-current measuring relay form mean? This reference locates differential-current measuring relay in Autodesk's IEEE-oriented current protection relays family. A differential-current relay responds to the relationship between specified current inputs. The schematic must identify input directions, ratio matching and the protected or monitored zone. The public library uses HCR1F29 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 Follow polarity and reference directions on all compared current circuits. Differential measurement is not simply a single high-current threshold. 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 differential-current measuring relay: a differential-current relay responds to the relationship between specified current inputs. Differential measurement is not simply a single high-current threshold. ### 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: Current Protection Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EC11EC4D-374C-4191-9534-C802D3932711.htm) ## What it represents This reference locates differential-current measuring relay in Autodesk's IEEE-oriented current protection relays family. A differential-current relay responds to the relationship between specified current inputs. The schematic must identify input directions, ratio matching and the protected or monitored zone. The public library uses HCR1F29 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. Follow polarity and reference directions on all compared current circuits. Differential measurement is not simply a single high-current threshold. 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 - Follow polarity and reference directions on all compared current circuits. - 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 compared inputs - Show polarity references - Link setting and zone documentation ## Important distinction Differential measurement is not simply a single high-current threshold. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Current Protection Relays; published form: Differential Current Protection. - Public vendor block: HCR1F29. 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: Current Protection Relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-EC11EC4D-374C-4191-9534-C802D3932711.htm) — Autodesk. Public IEEE-oriented Current Protection Relays table explicitly lists HCR1F29 as Differential Current 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.