{"schemaVersion":1,"slug":"line-distance-zone-selection-interface","name":"Line distance zone-selection interface","kind":"symbol","abbreviation":"LDZI","aliases":["Substation protection scheme interfaces","substations Substation protection scheme interfaces","substations","Substations","Impedance measurements","Selected distance-zone operation"],"category":"measurement-protection","drawingTypes":["Schematic"],"referenceFamilies":["Manufacturer"],"summary":"Associates the selected distance element with its documented reach zone and decision output.","description":["Associates the selected distance element with its documented reach zone and decision output. A protection scheme combines measurements, decision elements and communication or trip outputs to protect a defined part of the network. A function number names a job; the scheme interface shows how that job connects to other equipment.","In a substation feeder bay, local current and voltage measurements may combine with a remote-end signal before the protection issues the assigned trip request. Backup actions use their own defined initiations and supervision. For this reference, the drawing identifies “Impedance measurements” at the input and “Selected distance-zone operation” at the output. Reach settings follow the line protection study.","Keep each protected zone, initiating quantity, blocking signal and trip destination distinct. Settings, communication performance and coordination require the approved protection study and selected relay documentation. 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: Impedance measurements. Identify its source device or document and the state represented on the drawing.","Follow the named output: Selected distance-zone operation. Cross-reference its destination and separate the command from confirmation that the equipment responded.","Reach settings follow the line protection study.","Keep each protected zone, initiating quantity, blocking signal and trip destination distinct. Settings, communication performance and coordination require the approved protection study and selected relay documentation."],"drawingChecklist":["Label the source and connection reference for impedance measurements.","Identify the destination and defined state of selected distance-zone operation.","Record the equipment or control-document revision supporting this functional block.","Check this application limit in the project design: Reach settings follow the line protection study."],"distinction":"Reach settings follow the line protection study. 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":"Impedance measurements"},{"label":"Output / connection","value":"Selected distance-zone operation"},{"label":"Lookup label","value":"LDZI is a library lookup label, not a standard device designation."}],"references":[{"sourceId":"pub-function-sel-line","relevance":"Public technical context for substation protection scheme interfaces. Line protection, breaker failure, communications and protection coordination. The application text and educational graphic are independently authored; the publisher does not certify this representation."}],"related":["50bf-circuit-breaker-failure-protection","87b-busbar-differential-protection","auto-reclose-initiation-selection"],"artwork":"pi26-line-distance-zone-selection-interface","publishedOn":"2026-11-03","updatedOn":"2026-11-03","provenance":"independent-public-research","representation":{"type":"functional-block","focus":"substations","family":"protection-schemes","input":"Impedance measurements","output":"Selected distance-zone operation"},"plainEnglish":{"title":"What this block does","introduction":"Associates the selected distance element with its documented reach zone and decision output.","example":"In a substation feeder bay, local current and voltage measurements may combine with a remote-end signal before the protection issues the assigned trip request. Backup actions use their own defined initiations and supervision. For this reference, the drawing identifies “Impedance measurements” at the input and “Selected distance-zone operation” at the output. Reach settings follow the line protection study.","drawings":"Start at the named input: Impedance measurements. Identify its source device or document and the state represented on the drawing. Follow the named output: Selected distance-zone operation. Cross-reference its destination and separate the command from confirmation that the equipment responded.","terms":[{"name":"Input","meaning":"Impedance measurements"},{"name":"Output","meaning":"Selected distance-zone operation"},{"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":["Impedance measurements","LDZI","Selected distance-zone operation"],"caption":"A reading guide. The entry's original illustration and input/output facts describe this application.","sources":[{"label":"SEL-411L line differential protection overview","url":"https://selinc.com/products/411l/"}],"profileId":"power-installation-protection-schemes"},"url":"https://eloragrid.ai/symbols/line-distance-zone-selection-interface","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/line-distance-zone-selection-interface.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-line","title":"SEL-411L line differential protection overview","publisher":"Schweitzer Engineering Laboratories","url":"https://selinc.com/products/411l/","type":"manufacturer","scope":"Public explanation of communication-assisted line current differential protection and the associated terminal measurements. Product diagrams and technical papers remain on the publisher site.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public technical context for substation protection scheme interfaces. Line protection, breaker failure, communications and protection coordination. The application text and educational graphic are independently authored; the publisher does not certify this representation."}]}