{"schemaVersion":1,"slug":"bus-section-protection-boundary-interface","name":"Bus-section protection-boundary interface","kind":"symbol","abbreviation":"BPI","aliases":["Switchboard source and bus interfaces","switchgear Switchboard source and bus interfaces","switchgear","Switchgear","Section connection and CT locations","Protection boundary"],"category":"control-circuits","drawingTypes":["Schematic"],"referenceFamilies":["Manufacturer"],"summary":"Shows where the defined protection zone changes between adjacent bus sections.","description":["Shows where the defined protection zone changes between adjacent bus sections. A source and bus arrangement shows how incoming supplies and outgoing circuits can be connected. Breaker and tie positions determine which sections are energized and whether sources can become electrically paralleled.","In a switchgear lineup with two incomers and a bus tie, the single-line arrangement helps the engineer identify normal supply paths and which loads change source during a transfer. For this reference, the drawing identifies “Section connection and CT locations” at the input and “Protection boundary” at the output. A physical bus joint is not automatically a protection boundary.","Keep normal positions, transfer limits, source independence and protection-zone boundaries visible. An arrangement drawing explains connectivity; the permitted switching sequence needs a separate approved scheme. 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: Section connection and CT locations. Identify its source device or document and the state represented on the drawing.","Follow the named output: Protection boundary. Cross-reference its destination and separate the command from confirmation that the equipment responded.","A physical bus joint is not automatically a protection boundary.","Keep normal positions, transfer limits, source independence and protection-zone boundaries visible. An arrangement drawing explains connectivity; the permitted switching sequence needs a separate approved scheme."],"drawingChecklist":["Label the source and connection reference for section connection and ct locations.","Identify the destination and defined state of protection boundary.","Record the equipment or control-document revision supporting this functional block.","Check this application limit in the project design: A physical bus joint is not automatically a protection boundary."],"distinction":"A physical bus joint is not automatically a protection boundary. 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":"Switchgear"},{"label":"Input / boundary","value":"Section connection and CT locations"},{"label":"Output / connection","value":"Protection boundary"},{"label":"Lookup label","value":"BPI is a library lookup label, not a standard device designation."}],"references":[{"sourceId":"pi26-bus-schemes","relevance":"Public technical context for switchboard source and bus interfaces. Bus arrangements, breaker control and bay-level coordination. The application text and educational graphic are independently authored; the publisher does not certify this representation."}],"related":["busbar","automatic-transfer-switch","tie-breaker-maintenance-isolation-interface"],"artwork":"pi26-bus-section-protection-boundary-interface","publishedOn":"2026-11-03","updatedOn":"2026-11-03","provenance":"independent-public-research","representation":{"type":"functional-block","focus":"switchgear","family":"supply-arrangements","input":"Section connection and CT locations","output":"Protection boundary"},"plainEnglish":{"title":"What this block does","introduction":"Shows where the defined protection zone changes between adjacent bus sections.","example":"In a switchgear lineup with two incomers and a bus tie, the single-line arrangement helps the engineer identify normal supply paths and which loads change source during a transfer. For this reference, the drawing identifies “Section connection and CT locations” at the input and “Protection boundary” at the output. A physical bus joint is not automatically a protection boundary.","drawings":"Start at the named input: Section connection and CT locations. Identify its source device or document and the state represented on the drawing. Follow the named output: Protection boundary. Cross-reference its destination and separate the command from confirmation that the equipment responded.","terms":[{"name":"Input","meaning":"Section connection and CT locations"},{"name":"Output","meaning":"Protection boundary"},{"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":["Section connection and CT locations","BPI","Protection boundary"],"caption":"A reading guide. The entry's original illustration and input/output facts describe this application.","sources":[{"label":"SEL-451 protection, automation and bay control","url":"https://selinc.com/products/451/"}],"profileId":"power-installation-supply-arrangements"},"url":"https://eloragrid.ai/symbols/bus-section-protection-boundary-interface","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/bus-section-protection-boundary-interface.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pi26-bus-schemes","publisher":"SEL","title":"SEL-451 protection, automation and bay control","url":"https://selinc.com/products/451/","scope":"Bus arrangements, breaker control and bay-level coordination.","type":"manufacturer","checkedOn":"2026-11-03","reuse":"link-only","relevance":"Public technical context for switchboard source and bus interfaces. Bus arrangements, breaker control and bay-level coordination. The application text and educational graphic are independently authored; the publisher does not certify this representation."}]}