# Breaker-and-a-half diameter arrangement

Canonical URL: https://eloragrid.ai/symbols/breaker-and-a-half-diameter-arrangement
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: BDA
Drawing use: SLD, Schematic
Reference families: Manufacturer

Representation: Circuit arrangement
Installation focus: switchyards
Input: Two circuits and three breakers
Output: Shared diameter supply paths

Connects two circuits through the documented three-breaker diameter between buses.

## In plain English

### What this arrangement shows

Connects two circuits through the documented three-breaker diameter between 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 circuits and three breakers” at the input and “Shared diameter supply paths” at the output. The middle breaker participates in two circuit paths.

### What the drawings help you do

Start at the named input: Two circuits and three breakers. Identify its source device or document and the state represented on the drawing. Follow the named output: Shared diameter supply paths. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Two circuits and three breakers
- Output: Shared diameter supply paths
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Two circuits and three breakers → BDA → Shared diameter supply paths
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

Connects two circuits through the documented three-breaker diameter between 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 circuits and three breakers” at the input and “Shared diameter supply paths” at the output. The middle breaker participates in two circuit paths.
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 circuits and three breakers. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Shared diameter supply paths. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- The middle breaker participates in two circuit paths.
- 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 circuits and three breakers.
- Identify the destination and defined state of shared diameter supply paths.
- Record the equipment or control-document revision supporting this circuit arrangement.
- Check this application limit in the project design: The middle breaker participates in two circuit paths.

## Important distinction

The middle breaker participates in two circuit paths. 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 circuits and three breakers
- Output / connection: Shared diameter supply paths
- Lookup label: BDA 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.