{"schemaVersion":1,"slug":"vt-voltage-selection-discrepancy-alarm","name":"VT voltage-selection discrepancy alarm","kind":"symbol","abbreviation":"VVDA","aliases":["Voltage-transformer secondary arrangements","substations Voltage-transformer secondary arrangements","substations","Substations","Selection command and feedback","Voltage selection fault"],"category":"measurement-protection","drawingTypes":["Schematic"],"referenceFamilies":["Manufacturer"],"summary":"Reports disagreement between the requested voltage reference and its selection feedback.","description":["Reports disagreement between the requested voltage reference and its selection feedback. A voltage-transformer secondary arrangement connects a defined primary voltage measurement to protection, metering or control inputs. Winding identity, fuse protection and the voltage reference must remain visible across the drawing.","In a substation bay, one voltage circuit can feed protection while a separately identified winding supplies metering. A voltage-selection circuit must make clear which bus or line measurement is being used. For this reference, the drawing identifies “Selection command and feedback” at the input and “Voltage selection fault” at the output. The affected protection and control functions need identification.","Show the primary measurement point, secondary connection, protective devices and relay reference. A missing measurement can resemble a real system disturbance unless the voltage-circuit health is supervised appropriately. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation."],"readingNotes":["Start at the named input: Selection command and feedback. Identify its source device or document and the state represented on the drawing.","Follow the named output: Voltage selection fault. Cross-reference its destination and separate the command from confirmation that the equipment responded.","The affected protection and control functions need identification.","Show the primary measurement point, secondary connection, protective devices and relay reference. A missing measurement can resemble a real system disturbance unless the voltage-circuit health is supervised appropriately."],"drawingChecklist":["Label the source and connection reference for selection command and feedback.","Identify the destination and defined state of voltage selection fault.","Record the equipment or control-document revision supporting this functional block.","Check this application limit in the project design: The affected protection and control functions need identification."],"distinction":"The affected protection and control functions need identification. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.","facts":[{"label":"Representation","value":"Functional block"},{"label":"Installation focus","value":"Substations"},{"label":"Input / boundary","value":"Selection command and feedback"},{"label":"Output / connection","value":"Voltage selection fault"},{"label":"Lookup label","value":"VVDA is a library lookup label, not a standard device designation."}],"references":[{"sourceId":"instrument-transformers","relevance":"Public technical context for voltage-transformer secondary arrangements. Current and voltage measurement transformers and their secondary interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation."}],"related":["voltage-transformer","potential-test-switch","protection-winding-vt-secondary-circuit"],"artwork":"pi26-vt-voltage-selection-discrepancy-alarm","publishedOn":"2026-11-03","updatedOn":"2026-11-03","provenance":"independent-public-research","representation":{"type":"functional-block","focus":"substations","family":"vt-secondary","input":"Selection command and feedback","output":"Voltage selection fault"},"plainEnglish":{"title":"What this block does","introduction":"Reports disagreement between the requested voltage reference and its selection feedback.","example":"In a substation bay, one voltage circuit can feed protection while a separately identified winding supplies metering. A voltage-selection circuit must make clear which bus or line measurement is being used. For this reference, the drawing identifies “Selection command and feedback” at the input and “Voltage selection fault” at the output. The affected protection and control functions need identification.","drawings":"Start at the named input: Selection command and feedback. Identify its source device or document and the state represented on the drawing. Follow the named output: Voltage selection fault. Cross-reference its destination and separate the command from confirmation that the equipment responded.","terms":[{"name":"Input","meaning":"Selection command and feedback"},{"name":"Output","meaning":"Voltage selection fault"},{"name":"Application reference","meaning":"An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections."}],"diagram":"flow","steps":["Selection command and feedback","VVDA","Voltage selection fault"],"caption":"A reading guide. The entry's original illustration and input/output facts describe this application.","sources":[{"label":"Indoor current and voltage transformers","url":"https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers"}],"profileId":"power-installation-vt-secondary"},"url":"https://eloragrid.ai/symbols/vt-voltage-selection-discrepancy-alarm","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/vt-voltage-selection-discrepancy-alarm.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"instrument-transformers","title":"Indoor current and voltage transformers","publisher":"ABB","url":"https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers","type":"manufacturer","scope":"Public current- and voltage-transformer product families. Ratings, terminals and dimensions depend on the model.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public technical context for voltage-transformer secondary arrangements. Current and voltage measurement transformers and their secondary interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation."}]}