Breaker-and-a-half middle-bay interface

What it represents

Identifies the shared middle-breaker connections within the assigned diameter. 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 “Two diameter circuits” at the input and “Middle-breaker interface” at the output. Shared breaker failure affects both associated circuits.

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: Two diameter circuits. Identify its source device or document and the state represented on the drawing.
• Follow the named output: Middle-breaker interface. Cross-reference its destination and separate the command from confirmation that the equipment responded.
• Shared breaker failure affects both associated circuits.
• 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 two diameter circuits.
• Identify the destination and defined state of middle-breaker interface.
• Record the equipment or control-document revision supporting this functional block.
• Check this application limit in the project design: Shared breaker failure affects both associated circuits.

Sources you can follow

These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.

About this graphic

This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.

SVG and DXF downloads contain this original artwork. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.