# Disconnector-closed breaker interlock Canonical URL: https://eloragrid.ai/symbols/disconnector-closed-breaker-interlock Publisher: Elora Grid Updated: 2026-11-03 Lookup label: DBI Drawing use: Schematic Reference families: Manufacturer Representation: Functional block Installation focus: switchgear Input: Disconnector closed proof Output: Breaker close permission Requires the selected disconnector to occupy its defined closed position before breaker closing. ## In plain English ### What this block does Requires the selected disconnector to occupy its defined closed position before breaker closing. ### A simple example In a switchgear feeder panel, a control diagram can prevent an incompatible combination of breaker, disconnector and earthing-switch positions. The physical equipment documents determine which restrictions are mechanically enforced. For this reference, the drawing identifies “Disconnector closed proof” at the input and “Breaker close permission” at the output. A permissive is valid only for its assigned path. ### What the drawings help you do Start at the named input: Disconnector closed proof. Identify its source device or document and the state represented on the drawing. Follow the named output: Breaker close permission. Cross-reference its destination and separate the command from confirmation that the equipment responded. ### Terms - Input: Disconnector closed proof - Output: Breaker close permission - Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections. Concept diagram: Disconnector closed proof → DBI → Breaker close permission A reading guide. The entry's original illustration and input/output facts describe this application. - [Masterclad medium-voltage switchgear: circuit-breaker section interlocks](https://productinfo.se.com/masterclad_mv_switchgear_ib/6055-30-masterclad-15kv-mv-switchgear-ib/English/6055-30%20Masterclad%20MV%20Switchgear%20Indoor%20%28bookmap%29_DD00646805.xml/%24/Section6-CircuitBreakerSectionInter-58DD6EC7) ## What it represents Requires the selected disconnector to occupy its defined closed position before breaker closing. An interlocking function permits or blocks an operation according to the positions and conditions of related equipment. Electrical, mechanical and trapped-key interlocks implement different parts of a coordinated operating philosophy. In a switchgear feeder panel, a control diagram can prevent an incompatible combination of breaker, disconnector and earthing-switch positions. The physical equipment documents determine which restrictions are mechanically enforced. For this reference, the drawing identifies “Disconnector closed proof” at the input and “Breaker close permission” at the output. A permissive is valid only for its assigned path. Identify each initiating position, the action being blocked and the consequence of missing feedback. An illustrative logic diagram must not be treated as an operating procedure or proof of a complete safety system. 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. ## How to read it - Start at the named input: Disconnector closed proof. Identify its source device or document and the state represented on the drawing. - Follow the named output: Breaker close permission. Cross-reference its destination and separate the command from confirmation that the equipment responded. - A permissive is valid only for its assigned path. - Identify each initiating position, the action being blocked and the consequence of missing feedback. An illustrative logic diagram must not be treated as an operating procedure or proof of a complete safety system. ## Information to show or reference - Label the source and connection reference for disconnector closed proof. - Identify the destination and defined state of breaker close permission. - Record the equipment or control-document revision supporting this functional block. - Check this application limit in the project design: A permissive is valid only for its assigned path. ## Important distinction A permissive is valid only for its assigned path. 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 - Representation: Functional block - Installation focus: Switchgear - Input / boundary: Disconnector closed proof - Output / connection: Breaker close permission - Lookup label: DBI is a library lookup label, not a standard device designation. ## Public references - [Masterclad medium-voltage switchgear: circuit-breaker section interlocks](https://productinfo.se.com/masterclad_mv_switchgear_ib/6055-30-masterclad-15kv-mv-switchgear-ib/English/6055-30%20Masterclad%20MV%20Switchgear%20Indoor%20%28bookmap%29_DD00646805.xml/%24/Section6-CircuitBreakerSectionInter-58DD6EC7) — Schneider Electric. Public technical context for switchgear interlocking functions. Breaker control, mechanism, position contacts, racking interlocks and test interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation. ## Graphic scope Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.