# Three-breaker two-source transfer interface

Canonical URL: https://eloragrid.ai/symbols/three-breaker-two-source-transfer-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: TTTI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: switchgear
Input: Three breaker positions
Output: Transfer arrangement

Relates the two incoming breakers and one bus tie in a defined source-transfer system.

## In plain English

### What this block does

Relates the two incoming breakers and one bus tie in a defined source-transfer system.

### A simple example

In a switchgear lineup with two incomers and a bus tie, the single-line arrangement helps the engineer identify normal supply paths and which loads change source during a transfer. For this reference, the drawing identifies “Three breaker positions” at the input and “Transfer arrangement” at the output. The interlock matrix determines allowed combinations.

### What the drawings help you do

Start at the named input: Three breaker positions. Identify its source device or document and the state represented on the drawing. Follow the named output: Transfer arrangement. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Three breaker positions
- Output: Transfer arrangement
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Three breaker positions → TTTI → Transfer arrangement
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

Relates the two incoming breakers and one bus tie in a defined source-transfer system. A source and bus arrangement shows how incoming supplies and outgoing circuits can be connected. Breaker and tie positions determine which sections are energized and whether sources can become electrically paralleled.
In a switchgear lineup with two incomers and a bus tie, the single-line arrangement helps the engineer identify normal supply paths and which loads change source during a transfer. For this reference, the drawing identifies “Three breaker positions” at the input and “Transfer arrangement” at the output. The interlock matrix determines allowed combinations.
Keep normal positions, transfer limits, source independence and protection-zone boundaries visible. An arrangement drawing explains connectivity; the permitted switching sequence needs a separate approved scheme. 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: Three breaker positions. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Transfer arrangement. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- The interlock matrix determines allowed combinations.
- Keep normal positions, transfer limits, source independence and protection-zone boundaries visible. An arrangement drawing explains connectivity; the permitted switching sequence needs a separate approved scheme.

## Information to show or reference

- Label the source and connection reference for three breaker positions.
- Identify the destination and defined state of transfer arrangement.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: The interlock matrix determines allowed combinations.

## Important distinction

The interlock matrix determines allowed combinations. 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: Three breaker positions
- Output / connection: Transfer arrangement
- Lookup label: TTTI 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 switchboard source and bus interfaces. 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.