Q021211
Mechanical interlock between devices
A mechanical interlock indication links devices whose movements are constrained by a physical relationship.
IEC
Functional block · LCI
Local-remote command interlock
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
Accepts commands only from the location selected by the documented authority mechanism.
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 “Authority selector and command” at the input and “Accepted command path” at the output. Indication and operating authority are separate signals.
What the drawings help you do
Start at the named input: Authority selector and command. Identify its source device or document and the state represented on the drawing. Follow the named output: Accepted command path. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Authority selector and command
- Output
- Accepted command path
- 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 · LCI
What it represents
Accepts commands only from the location selected by the documented authority mechanism. 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 “Authority selector and command” at the input and “Accepted command path” at the output. Indication and operating authority are separate signals.
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: Authority selector and command. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Accepted command path. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Indication and operating authority are separate signals.
- 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 authority selector and command.
- Identify the destination and defined state of accepted command path.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Indication and operating authority are separate signals.
A distinction that matters
Indication and operating authority are separate signals. 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.
Explore related references
Put the reference into a drawing workflow.
Elora Grid helps electrical teams work with drawings, specifications and equipment information. Explore the drafting workflow or join the early-access waitlist.