{"schemaVersion":1,"slug":"55d-displacement-power-factor-supervision","name":"Displacement power-factor supervision","kind":"function","abbreviation":"55D","aliases":["displacement power factor","fundamental power factor","ANSI 55D","IEEE 55D"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"Supervises displacement power factor as defined by the relay's fundamental-frequency measurements.","description":["Supervises displacement power factor as defined by the relay's fundamental-frequency measurements.","The drafting record should connect this function to the current and voltage inputs and displacement-angle reference, then trace the displacement power-factor output or control interface. Keep the complete designation and equipment tag together so that the SLD, relay logic and terminal schedule describe the same implementation.","The cited mapping is a public manufacturer example (Eaton E-Series function mapping). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme."],"readingNotes":["Identify the current and voltage inputs and displacement-angle reference.","Trace the displacement power-factor output or control interface."],"drawingChecklist":["Label the current and voltage inputs and displacement-angle reference.","Cross-reference the displacement power-factor output or control interface.","Retain the complete suffix, selected device tag and manufacturer manual revision."],"distinction":"55D is not interchangeable with the apparent power-factor element 55A when the waveform contains harmonics.","facts":[{"label":"Function designation","value":"55D"},{"label":"Base function","value":"55 — Power factor protection"},{"label":"Published mapping","value":"Eaton E-Series function mapping"},{"label":"Suffix scope","value":"Application or manufacturer specific; check the complete drawing legend and selected device manual."}],"references":[{"sourceId":"pub-function-eaton-brochure","relevance":"Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original."},{"sourceId":"ieee-functions","relevance":"Device-number and suffix convention. This page is not a reproduction of the full licensed standard."}],"related":["55-power-factor-protection","voltage-transformer"],"artwork":"pub-function-box","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/protection-functions/55d-displacement-power-factor-supervision","illustration":{"url":"https://eloragrid.ai/library/illustrations/55d-displacement-power-factor-supervision.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-function-eaton-brochure","title":"E-Series protective relays: public family comparison brochure","publisher":"Eaton","url":"https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/protective-relays-and-predictive-devices/e-series-protective-relays-br026001en.pdf","type":"manufacturer","scope":"Public function-name and suffix mappings across feeder, motor, transformer and generator relays. Linked as documentation only; no illustrations or product drawings are copied.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original."},{"id":"ieee-functions","title":"IEEE C37.2-2022: power-system device function numbers","publisher":"IEEE","url":"https://ieeexplore.ieee.org/document/9984140","type":"standard","scope":"Device function numbers, acronyms and contact designations. The full publication may require access through IEEE.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Device-number and suffix convention. This page is not a reproduction of the full licensed standard."}]}