{"schemaVersion":1,"slug":"single-tuned-harmonic-filter","name":"Single-tuned harmonic filter","kind":"symbol","abbreviation":"HF","aliases":["tuned passive filter","notch harmonic filter","series LC filter"],"category":"microgrid-systems","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEC","IEEE / ANSI"],"summary":"A shunt series-LC branch tuned near one harmonic order to sink that harmonic current from the network.","description":["A single-tuned filter is a capacitor and reactor in series, connected in shunt and tuned to resonate near one harmonic frequency, often slightly below the 5th, 7th or 11th. At that frequency it presents a low impedance and draws harmonic current away from the network, while at fundamental frequency it supplies capacitive reactive power.","Drawings show a capacitor and reactor in series on a shunt branch, labelled with the tuned order, and often several such branches for different orders. Unbalance protection for the capacitor bank and a dedicated breaker are normally shown.","A tuned filter creates a parallel resonance with the network at a frequency just below its tuning, which can amplify other harmonics. The symbol does not show the network impedance scan or detuning tolerance, so the harmonic study must accompany it."],"readingNotes":["Read the harmonic order label on each branch.","The filter also supplies fundamental reactive power."],"drawingChecklist":["State tuned order, Mvar and quality factor.","Show breaker and unbalance protection.","Reference harmonic study."],"distinction":"A single-tuned filter targets one harmonic order; a damped high-pass filter attenuates a broad band above its corner frequency.","facts":[{"label":"Elements","value":"Series capacitor and reactor"},{"label":"Behaviour at tuning","value":"Low impedance sink"},{"label":"Fundamental output","value":"Capacitive Mvar"},{"label":"Preview","value":"Independent educational illustration; consult the applicable standard and project legend for the exact graphic"}],"references":[{"sourceId":"s28-hitachi-capacitors-filters","relevance":"Public passive and harmonic filter product context."},{"sourceId":"pub-symbol-reactors","relevance":"Public reactor symbol family context."}],"related":["damped-high-pass-harmonic-filter","detuned-capacitor-bank","active-harmonic-filter","static-var-compensator"],"artwork":"s28-single-tuned-harmonic-filter","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Single-tuned harmonic filter mean?","introduction":"A single-tuned filter is a capacitor and reactor in series, connected in shunt and tuned to resonate near one harmonic frequency, often slightly below the 5th, 7th or 11th. At that frequency it presents a low impedance and draws harmonic current away from the network, while at fundamental frequency it supplies capacitive reactive power.","example":"Drawings show a capacitor and reactor in series on a shunt branch, labelled with the tuned order, and often several such branches for different orders. Unbalance protection for the capacitor bank and a dedicated breaker are normally shown.","drawings":"A tuned filter creates a parallel resonance with the network at a frequency just below its tuning, which can amplify other harmonics. The symbol does not show the network impedance scan or detuning tolerance, so the harmonic study must accompany it.","terms":[{"name":"Rating","meaning":"A value stating the conditions for which equipment is specified."},{"name":"Schematic","meaning":"A drawing showing function and connections rather than physical appearance."}],"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":"Capacitor and filter product offerings","url":"https://www.hitachienergy.com/products-and-solutions/capacitors-and-filters"},{"label":"AutoCAD Electrical: Reactors and inductors","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-BAD50DBF-0951-44A0-BB4C-A57B4A4ED895.htm"}],"detail":"A shunt series-LC branch tuned near one harmonic order to sink that harmonic current from the network. A single-tuned filter targets one harmonic order; a damped high-pass filter attenuates a broad band above its corner frequency.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/single-tuned-harmonic-filter","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/single-tuned-harmonic-filter.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"s28-hitachi-capacitors-filters","title":"Capacitor and filter product offerings","publisher":"Hitachi Energy","url":"https://www.hitachienergy.com/products-and-solutions/capacitors-and-filters","type":"manufacturer","scope":"Public overview of passive and harmonic filters and shunt compensation banks with and without reactors.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Public passive and harmonic filter product context."},{"id":"pub-symbol-reactors","title":"AutoCAD Electrical: Reactors and inductors","publisher":"Autodesk","url":"https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-BAD50DBF-0951-44A0-BB4C-A57B4A4ED895.htm","type":"cad-reference","scope":"Public vendor catalogue naming and functional variants. Vendor block names are not IEC identifiers. Linked for reference; no graphics or CAD files are redistributed.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public reactor symbol family context."}]}