AT
Lightning air termination
A rod or mesh conductor on top of a structure intended to intercept lightning strikes before they hit the structure.
GA / Schematic
Symbols · DC
Lightning protection down-conductor
The conductor carrying lightning current from air terminations on a structure down to the earth termination system.
In plain English
What does Lightning protection down-conductor mean?
Down-conductors run from the air termination network on the roof to the earth electrodes, carrying lightning current by the shortest practical path. Installation guidance describes them as part of the building protection system together with the capture device and earth leads. Elevations and roof plans show them as a distinct line style.
A simple example
The symbol does not tell you material, cross-section or separation distance from internal services. Insufficient separation can cause side flashes into wiring. Structural steel or reinforcing used as natural down-conductors may not be drawn explicitly, so check the lightning protection design notes.
What the drawings help you do
Check separation from internal wiring and services. Identify whether structural steel is used as a down path. A down-conductor carries lightning current to earth; a protective earth conductor carries fault current from the electrical installation.
This particular reference
The conductor carrying lightning current from air terminations on a structure down to the earth termination system. A down-conductor carries lightning current to earth; a protective earth conductor carries fault current from the electrical installation.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: Building protection system · AutoCAD Electrical: Earthing, sources and surge protection
GA / Schematic · DC
What it represents
Down-conductors run from the air termination network on the roof to the earth electrodes, carrying lightning current by the shortest practical path. Installation guidance describes them as part of the building protection system together with the capture device and earth leads. Elevations and roof plans show them as a distinct line style.
The symbol does not tell you material, cross-section or separation distance from internal services. Insufficient separation can cause side flashes into wiring. Structural steel or reinforcing used as natural down-conductors may not be drawn explicitly, so check the lightning protection design notes.
How to read it
- Check separation from internal wiring and services.
- Identify whether structural steel is used as a down path.
Information to show or reference
- Show each down-conductor route.
- State material and size.
- Show test joint and earth termination at the base.
A distinction that matters
A down-conductor carries lightning current to earth; a protective earth conductor carries fault current from the electrical installation.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Building protection system
Public installation-guide description of building lightning protection with down-conductors.
AutoCAD Electrical: Earthing, sources and surge protection
Public IEC-oriented earth forms.
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. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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