# ANSI/IEEE Neutral-unbalance relay between two polyphase systems form Canonical URL: https://eloragrid.ai/symbols/ansi-neutral-unbalance-relay-between-two-systems 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: In Neutral between 2 Multi-Phase Systems Autodesk IEEE Symbol Preview: Current Protection Relays, block HCR1F33. Matching functional counterpart linked separately. Independently drawn educational geometry; not a certified IEEE glyph or database identifier. Related representation: [Neutral-unbalance relay between two polyphase systems](https://eloragrid.ai/symbols/neutral-unbalance-relay-between-two-systems) IEEE-library reference for neutral-unbalance relay between two polyphase systems, with its operating meaning, connection notes and public vendor block identity. ## In plain English ### What does ANSI/IEEE Neutral-unbalance relay between two polyphase systems form mean? This reference locates neutral-unbalance relay between two polyphase systems in Autodesk's IEEE-oriented current protection relays family. This form shows a current relay in the conductor that joins the neutral points of two star-connected polyphase systems. A familiar application is the double-star capacitor bank, where a CT in the link between the two star points detects unbalance caused by failed capacitor units. The public library uses HCR1F33 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 In a healthy balanced arrangement the link carries little current, so the relay setting is a small fraction of phase current and must allow for natural unbalance. The symbol does not tell you the alarm and trip stages or the compensation for inherent unbalance; those are in the bank protection settings. Identify the two star points joined by the measured link. This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply. 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 reference for neutral-unbalance relay between two polyphase systems, with its operating meaning, connection notes and public vendor block identity. This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply. ### 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. - Phase: One of the related AC waveforms in a power system. 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) - [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) ## What it represents This reference locates neutral-unbalance relay between two polyphase systems in Autodesk's IEEE-oriented current protection relays family. This form shows a current relay in the conductor that joins the neutral points of two star-connected polyphase systems. A familiar application is the double-star capacitor bank, where a CT in the link between the two star points detects unbalance caused by failed capacitor units. The public library uses HCR1F33 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. In a healthy balanced arrangement the link carries little current, so the relay setting is a small fraction of phase current and must allow for natural unbalance. The symbol does not tell you the alarm and trip stages or the compensation for inherent unbalance; those are in the bank protection settings. Identify the two star points joined by the measured link. This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply. 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 - Identify the two star points joined by the measured link. - Look for separate alarm and trip stages. ## Information to show or reference - Show the interconnecting link and CT - State alarm and trip settings - Note inherent unbalance compensation ## Important distinction This relay measures the link between two star points; a neutral-current relay measures one neutral path to earth or to the supply. ## Facts - Convention evidence: Autodesk IEEE Symbol Preview: Current Protection Relays; published form: In Neutral between 2 Multi-Phase Systems. - Public vendor block: HCR1F33. Vendor library token, not an IEEE symbol number. - Measured quantity: Current in a neutral interconnection between two systems - 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: 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 HCR1F33 as In Neutral between 2 Multi-Phase Systems. 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.