{"schemaVersion":1,"slug":"78vs-voltage-vector-shift-protection","name":"Voltage vector-shift protection","kind":"function","abbreviation":"78VS","aliases":["vector shift","vector surge","78V","ANSI 78VS","IEEE 78VS"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"Supervises an abrupt change in the measured voltage phase angle using the selected relay's vector-shift method.","description":["Supervises an abrupt change in the measured voltage phase angle using the selected relay's vector-shift method.","The drafting record should connect this function to the measured voltage inputs and interconnection point, then trace the vector-shift operating output and interconnection protection logic. 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 (SEL generator protection feature table). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme."],"readingNotes":["Identify the measured voltage inputs and interconnection point.","Trace the vector-shift operating output and interconnection protection logic."],"drawingChecklist":["Label the measured voltage inputs and interconnection point.","Cross-reference the vector-shift operating output and interconnection protection logic.","Retain the complete suffix, selected device tag and manufacturer manual revision."],"distinction":"Vector shift 78VS/78V is a product-mapped function and differs from the complete out-of-step or pole-slip application of base 78.","facts":[{"label":"Function designation","value":"78VS"},{"label":"Base function","value":"78 — Phase-angle or out-of-step protection"},{"label":"Published mapping","value":"SEL generator protection feature table"},{"label":"Suffix scope","value":"Application or manufacturer specific; check the complete drawing legend and selected device manual."}],"references":[{"sourceId":"pub-function-sel-generator","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":["78-phase-angle-or-out-of-step-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/78vs-voltage-vector-shift-protection","illustration":{"url":"https://eloragrid.ai/library/illustrations/78vs-voltage-vector-shift-protection.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-sel-generator","title":"Generator protection feature and function comparison","publisher":"Schweitzer Engineering Laboratories","url":"https://selinc.com/products/comparisons/generator-protection/","type":"manufacturer","scope":"Public mappings for generator functions, including phase distance, field/stator ground, thermal RTD, sequence-current and vector-shift applications. Product availability depends on model/options; no settings are provided here.","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."}]}