{"schemaVersion":1,"slug":"lightning-test-joint","name":"Lightning protection test joint","kind":"symbol","abbreviation":"TJ","aliases":["down-conductor test clamp","LPS test link","testing joint"],"category":"connections-wiring","drawingTypes":["GA","Schematic"],"referenceFamilies":["IEC","IEEE / ANSI"],"summary":"A disconnectable joint near the base of a down-conductor that allows the earth termination to be tested separately.","description":["Each down-conductor usually has a test joint at a convenient height above ground. Opening it separates the above-ground lightning conductor from the earth electrode, so electrode resistance and conductor continuity can be measured. Elevations show it as a small box or clamp mark on the down-conductor.","The test joint is not an isolating device for electrical work; it is only opened for inspection with no storm risk. The symbol does not specify clamp type or whether it is housed in a box. Missing or painted-over test joints are a common inspection finding."],"readingNotes":["Locate the test joint on each down-conductor.","Confirm it is reachable for inspection."],"drawingChecklist":["Show a test joint on every down-conductor.","State mounting height.","Number joints to match inspection records."],"distinction":"A lightning test joint separates the down-conductor from its electrode; an earth test link separates the installation MET from its electrode.","facts":[{"label":"Graphic cue","value":"Small box or clamp mark near the base of a down-conductor"},{"label":"Use","value":"Electrode and continuity testing"},{"label":"Preview","value":"Original educational illustration; consult the publisher and applicable standard for the exact graphic"}],"references":[{"sourceId":"s28-eig-building-lightning-protection","relevance":"Public installation-guide description of lightning protection earth leads and down-conductors."},{"sourceId":"s28-eig-earthing-connections","relevance":"Public installation-guide earthing elements."}],"related":["lightning-down-conductor","iec-removable-earth-test-link","iec-earth-electrode"],"artwork":"s28-lightning-test-joint","publishedOn":"2026-10-28","updatedOn":"2026-10-28","provenance":"independent-public-research","plainEnglish":{"title":"What does Lightning protection test joint mean?","introduction":"Each down-conductor usually has a test joint at a convenient height above ground. Opening it separates the above-ground lightning conductor from the earth electrode, so electrode resistance and conductor continuity can be measured. Elevations show it as a small box or clamp mark on the down-conductor.","example":"The test joint is not an isolating device for electrical work; it is only opened for inspection with no storm risk. The symbol does not specify clamp type or whether it is housed in a box. Missing or painted-over test joints are a common inspection finding.","drawings":"Locate the test joint on each down-conductor. Confirm it is reachable for inspection. A lightning test joint separates the down-conductor from its electrode; an earth test link separates the installation MET from its electrode.","terms":[{"name":"Normally open / normally closed","meaning":"The contact state in the normal condition defined for the drawing."},{"name":"Schematic","meaning":"A drawing showing function and connections rather than physical appearance."}],"diagram":"flow","steps":["Identify the device and form","Read the connections and state","Check the equipment reference"],"caption":"A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.","sources":[{"label":"Building protection system","url":"https://www.electrical-installation.org/enwiki/Building_protection_system"},{"label":"Earthing connections","url":"https://www.electrical-installation.org/enwiki/Earthing_connections"}],"detail":"A disconnectable joint near the base of a down-conductor that allows the earth termination to be tested separately. A lightning test joint separates the down-conductor from its electrode; an earth test link separates the installation MET from its electrode.","profileId":"reviewed-symbol-20261028"},"url":"https://eloragrid.ai/symbols/lightning-test-joint","illustration":{"url":"https://eloragrid.ai/tools/electrical-library/illustrations/lightning-test-joint.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"s28-eig-building-lightning-protection","title":"Building protection system","publisher":"Schneider Electric, Electrical Installation Guide","url":"https://www.electrical-installation.org/enwiki/Building_protection_system","type":"manufacturer","scope":"Lightning capture devices, down-conductors, earth leads and equipotential bonding of a building protection system.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Public installation-guide description of lightning protection earth leads and down-conductors."},{"id":"s28-eig-earthing-connections","title":"Earthing connections","publisher":"Schneider Electric, Electrical Installation Guide","url":"https://www.electrical-installation.org/enwiki/Earthing_connections","type":"manufacturer","scope":"Definitions of earth electrode, main earthing terminal, removable test link and bonding conductors in an installation earthing arrangement.","checkedOn":"2026-10-28","reuse":"link-only","relevance":"Public installation-guide earthing elements."}]}