Q021211
Mechanical interlock between devices
A mechanical interlock indication links devices whose movements are constrained by a physical relationship.
IEC
Functional block · IFG
Invalid-position fail-block gate
Functional block · Switchgear
An independently authored application reference. The drawing shows the named function or circuit relationship; use the project legend and selected equipment documentation for its drafting form and connections.
Browse this installation focusIn plain English
What this block does
Blocks the assigned operation when its required position inputs form an invalid combination.
A simple example
In a switchgear feeder panel, a control diagram can prevent an incompatible combination of breaker, disconnector and earthing-switch positions. The physical equipment documents determine which restrictions are mechanically enforced. For this reference, the drawing identifies “Invalid double-point status” at the input and “Operation inhibit” at the output. The fail response must be agreed for the application.
What the drawings help you do
Start at the named input: Invalid double-point status. Identify its source device or document and the state represented on the drawing. Follow the named output: Operation inhibit. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Invalid double-point status
- Output
- Operation inhibit
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: Masterclad medium-voltage switchgear: circuit-breaker section interlocks
Schematic · IFG
What it represents
Blocks the assigned operation when its required position inputs form an invalid combination. An interlocking function permits or blocks an operation according to the positions and conditions of related equipment. Electrical, mechanical and trapped-key interlocks implement different parts of a coordinated operating philosophy.
In a switchgear feeder panel, a control diagram can prevent an incompatible combination of breaker, disconnector and earthing-switch positions. The physical equipment documents determine which restrictions are mechanically enforced. For this reference, the drawing identifies “Invalid double-point status” at the input and “Operation inhibit” at the output. The fail response must be agreed for the application.
Identify each initiating position, the action being blocked and the consequence of missing feedback. An illustrative logic diagram must not be treated as an operating procedure or proof of a complete safety system. 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: Invalid double-point status. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Operation inhibit. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- The fail response must be agreed for the application.
- Identify each initiating position, the action being blocked and the consequence of missing feedback. An illustrative logic diagram must not be treated as an operating procedure or proof of a complete safety system.
Information to show or reference
- Label the source and connection reference for invalid double-point status.
- Identify the destination and defined state of operation inhibit.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: The fail response must be agreed for the application.
A distinction that matters
The fail response must be agreed for the application. 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.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Masterclad medium-voltage switchgear: circuit-breaker section interlocks
Public technical context for switchgear interlocking functions. Breaker control, mechanism, position contacts, racking interlocks and test interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation.
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.
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