# Bus-selector disconnector pair Canonical URL: https://eloragrid.ai/symbols/bus-selector-disconnector-pair Publisher: Elora Grid Updated: 2026-11-03 Lookup label: BDP Drawing use: SLD, Schematic Reference families: Manufacturer Representation: Circuit arrangement Installation focus: switchyards Input: Two bus conductors Output: Selected bay connection Shows the two selectable isolating paths connecting a bay to its assigned buses. ## In plain English ### What this arrangement shows Shows the two selectable isolating paths connecting a bay to its assigned buses. ### A simple example In a switchyard, a single-line arrangement helps identify the bay connections, tie devices and possible alternate supply paths. Normal open points must remain separate from the equipment's physical ability to close. For this reference, the drawing identifies “Two bus conductors” at the input and “Selected bay connection” at the output. Unintended bus paralleling must be addressed by design. ### What the drawings help you do Start at the named input: Two bus conductors. Identify its source device or document and the state represented on the drawing. Follow the named output: Selected bay connection. Cross-reference its destination and separate the command from confirmation that the equipment responded. ### Terms - Input: Two bus conductors - Output: Selected bay connection - Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections. Concept diagram: Two bus conductors → BDP → Selected bay connection A reading guide. The entry's original illustration and input/output facts describe this application. - [SEL-451 protection, automation and bay control](https://selinc.com/products/451/) ## What it represents Shows the two selectable isolating paths connecting a bay to its assigned buses. A busbar arrangement defines the available paths between incoming circuits, outgoing circuits and bus sections. Its switching devices and measurement boundaries determine how a circuit can remain connected when part of the installation is unavailable. In a switchyard, a single-line arrangement helps identify the bay connections, tie devices and possible alternate supply paths. Normal open points must remain separate from the equipment's physical ability to close. For this reference, the drawing identifies “Two bus conductors” at the input and “Selected bay connection” at the output. Unintended bus paralleling must be addressed by design. Name each bus, bay and switching device. The arrangement illustrates electrical connectivity; reliability, fault levels, permitted switching and protection coordination require the actual network design. The circuit arrangement 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: Two bus conductors. Identify its source device or document and the state represented on the drawing. - Follow the named output: Selected bay connection. Cross-reference its destination and separate the command from confirmation that the equipment responded. - Unintended bus paralleling must be addressed by design. - Name each bus, bay and switching device. The arrangement illustrates electrical connectivity; reliability, fault levels, permitted switching and protection coordination require the actual network design. ## Information to show or reference - Label the source and connection reference for two bus conductors. - Identify the destination and defined state of selected bay connection. - Record the equipment or control-document revision supporting this circuit arrangement. - Check this application limit in the project design: Unintended bus paralleling must be addressed by design. ## Important distinction Unintended bus paralleling must be addressed by design. 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: Circuit arrangement - Installation focus: Switchyards - Input / boundary: Two bus conductors - Output / connection: Selected bay connection - Lookup label: BDP is a library lookup label, not a standard device designation. ## Public references - [SEL-451 protection, automation and bay control](https://selinc.com/products/451/) — SEL. Public technical context for switchyard busbar arrangements. Bus arrangements, breaker control and bay-level coordination. 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.