# Cable-transition bay interface

Canonical URL: https://eloragrid.ai/symbols/cable-transition-bay-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: CBI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: switchyards
Input: Overhead-line circuit
Output: Cable circuit interface

Marks the electrical transition between the assigned overhead and cable circuit sections.

## In plain English

### What this block does

Marks the electrical transition between the assigned overhead and cable circuit sections.

### A simple example

In a switchyard single-line drawing, the bay arrangement helps the reader follow the circuit from its bus connection to the external line, transformer or compensation equipment and identify the measurement boundaries along the path. For this reference, the drawing identifies “Overhead-line circuit” at the input and “Cable circuit interface” at the output. Termination and sheath details are separate drawings.

### What the drawings help you do

Start at the named input: Overhead-line circuit. Identify its source device or document and the state represented on the drawing. Follow the named output: Cable circuit interface. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Overhead-line circuit
- Output: Cable circuit interface
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Overhead-line circuit → CBI → Cable circuit interface
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

Marks the electrical transition between the assigned overhead and cable circuit sections. A bay circuit arrangement groups the switching, measuring and protection interfaces associated with a specific network circuit. A line bay, transformer bay and reactor bay share some devices but connect different kinds of primary equipment.
In a switchyard single-line drawing, the bay arrangement helps the reader follow the circuit from its bus connection to the external line, transformer or compensation equipment and identify the measurement boundaries along the path. For this reference, the drawing identifies “Overhead-line circuit” at the input and “Cable circuit interface” at the output. Termination and sheath details are separate drawings.
Preserve the actual order of primary connections, isolation points and CT locations. These conceptual arrangements do not establish equipment clearances, terminal layouts or an approved switching sequence. 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: Overhead-line circuit. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Cable circuit interface. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Termination and sheath details are separate drawings.
- Preserve the actual order of primary connections, isolation points and CT locations. These conceptual arrangements do not establish equipment clearances, terminal layouts or an approved switching sequence.

## Information to show or reference

- Label the source and connection reference for overhead-line circuit.
- Identify the destination and defined state of cable circuit interface.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Termination and sheath details are separate drawings.

## Important distinction

Termination and sheath details are separate drawings. 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: Switchyards
- Input / boundary: Overhead-line circuit
- Output / connection: Cable circuit interface
- Lookup label: CBI 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 bay circuit arrangements. Bay arrangements and coordinated breaker controls. 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.