{"schemaVersion":1,"slug":"control-power-automatic-source-selection","name":"Control-power automatic source selection","kind":"symbol","abbreviation":"CASS","aliases":["Switchgear control-power supervision","switchgear Switchgear control-power supervision","switchgear","Switchgear","Auxiliary-source health","Selected control-power source"],"category":"control-circuits","drawingTypes":["Schematic"],"referenceFamilies":["Manufacturer"],"summary":"Selects the documented auxiliary source according to its availability inputs.","description":["Selects the documented auxiliary source according to its availability inputs. Control power supplies the command, protection and indication equipment associated with a switchgear assembly. The drawing must distinguish the source, each distribution branch and the functions lost if that branch fails.","In a switchgear lineup, separate protected branches may feed trip coils, closing coils and protection electronics. Their alarm contacts help the station controller identify which operating capability is unavailable. For this reference, the drawing identifies “Auxiliary-source health” at the input and “Selected control-power source” at the output. Selection logic must not unintentionally parallel sources.","Follow the actual positive, negative or neutral returns and the protective device on each branch. A healthy voltage indication does not establish that every downstream path can deliver its required operating current. 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: Auxiliary-source health. Identify its source device or document and the state represented on the drawing.","Follow the named output: Selected control-power source. Cross-reference its destination and separate the command from confirmation that the equipment responded.","Selection logic must not unintentionally parallel sources.","Follow the actual positive, negative or neutral returns and the protective device on each branch. A healthy voltage indication does not establish that every downstream path can deliver its required operating current."],"drawingChecklist":["Label the source and connection reference for auxiliary-source health.","Identify the destination and defined state of selected control-power source.","Record the equipment or control-document revision supporting this functional block.","Check this application limit in the project design: Selection logic must not unintentionally parallel sources."],"distinction":"Selection logic must not unintentionally parallel sources. 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":"Auxiliary-source health"},{"label":"Output / connection","value":"Selected control-power source"},{"label":"Lookup label","value":"CASS is a library lookup label, not a standard device designation."}],"references":[{"sourceId":"pi26-station-power","relevance":"Public technical context for switchgear control-power supervision. Independent AC and DC sources for station auxiliary power. The application text and educational graphic are independently authored; the publisher does not certify this representation."}],"related":["relay-coil","ac-to-dc-power-supply","cabinet-control-supply-healthy-relay"],"artwork":"pi26-control-power-automatic-source-selection","publishedOn":"2026-11-03","updatedOn":"2026-11-03","provenance":"independent-public-research","representation":{"type":"functional-block","focus":"switchgear","family":"control-power","input":"Auxiliary-source health","output":"Selected control-power source"},"plainEnglish":{"title":"What this block does","introduction":"Selects the documented auxiliary source according to its availability inputs.","example":"In a switchgear lineup, separate protected branches may feed trip coils, closing coils and protection electronics. Their alarm contacts help the station controller identify which operating capability is unavailable. For this reference, the drawing identifies “Auxiliary-source health” at the input and “Selected control-power source” at the output. Selection logic must not unintentionally parallel sources.","drawings":"Start at the named input: Auxiliary-source health. Identify its source device or document and the state represented on the drawing. Follow the named output: Selected control-power source. Cross-reference its destination and separate the command from confirmation that the equipment responded.","terms":[{"name":"Input","meaning":"Auxiliary-source health"},{"name":"Output","meaning":"Selected control-power source"},{"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":["Auxiliary-source health","CASS","Selected control-power source"],"caption":"A reading guide. The entry's original illustration and input/output facts describe this application.","sources":[{"label":"SEL-RPM redundant power module","url":"https://selinc.com/products/RPM/"}],"profileId":"power-installation-control-power"},"url":"https://eloragrid.ai/symbols/control-power-automatic-source-selection","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/control-power-automatic-source-selection.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pi26-station-power","publisher":"SEL","title":"SEL-RPM redundant power module","url":"https://selinc.com/products/RPM/","scope":"Independent AC and DC sources for station auxiliary power.","type":"manufacturer","checkedOn":"2026-11-03","reuse":"link-only","relevance":"Public technical context for switchgear control-power supervision. Independent AC and DC sources for station auxiliary power. The application text and educational graphic are independently authored; the publisher does not certify this representation."}]}