# Transformer high-voltage bushing reference

Canonical URL: https://eloragrid.ai/symbols/transformer-high-voltage-bushing-reference
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: THBR
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: switchyards
Input: Transformer winding connection
Output: External high-voltage terminal

Identifies the insulated conductor passage between the transformer winding system and its external terminal.

## In plain English

### What this block does

Identifies the insulated conductor passage between the transformer winding system and its external terminal.

### A simple example

In a switchyard equipment diagram, the primary reference identifies the electrical role of an installed component while the linked equipment schedule and manufacturer drawing supply its exact construction and dimensions. For this reference, the drawing identifies “Transformer winding connection” at the input and “External high-voltage terminal” at the output. A bushing is not a separate switching device.

### What the drawings help you do

Start at the named input: Transformer winding connection. Identify its source device or document and the state represented on the drawing. Follow the named output: External high-voltage terminal. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Transformer winding connection
- Output: External high-voltage terminal
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Transformer winding connection → THBR → External high-voltage terminal
A reading guide. The entry's original illustration and input/output facts describe this application.

- [Gas-insulated switchgear](https://www.hitachienergy.com/products-and-solutions/high-voltage-switchgear-and-breakers/gas-insulated-switchgear)


## What it represents

Identifies the insulated conductor passage between the transformer winding system and its external terminal. High-voltage primary equipment carries, interrupts, measures or conditions the main power circuit. Its function, insulation arrangement and equipment boundaries need to be distinguished from the secondary signals used to control it.
In a switchyard equipment diagram, the primary reference identifies the electrical role of an installed component while the linked equipment schedule and manufacturer drawing supply its exact construction and dimensions. For this reference, the drawing identifies “Transformer winding connection” at the input and “External high-voltage terminal” at the output. A bushing is not a separate switching device.
Read the connected power path before interpreting a secondary output or alarm. These original educational component references provide no product dimensions, dielectric rating, installation clearance or construction approval. 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: Transformer winding connection. Identify its source device or document and the state represented on the drawing.
- Follow the named output: External high-voltage terminal. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- A bushing is not a separate switching device.
- Read the connected power path before interpreting a secondary output or alarm. These original educational component references provide no product dimensions, dielectric rating, installation clearance or construction approval.

## Information to show or reference

- Label the source and connection reference for transformer winding connection.
- Identify the destination and defined state of external high-voltage terminal.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: A bushing is not a separate switching device.

## Important distinction

A bushing is not a separate switching device. 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: Transformer winding connection
- Output / connection: External high-voltage terminal
- Lookup label: THBR is a library lookup label, not a standard device designation.

## Public references

- [Gas-insulated switchgear](https://www.hitachienergy.com/products-and-solutions/high-voltage-switchgear-and-breakers/gas-insulated-switchgear) — Hitachi Energy. Public technical context for high-voltage primary equipment references. Primary switching equipment and instrument-transformer 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.