AF
Arc-flash point light sensor
Light sensor in a switchgear compartment that detects the flash of an internal arc and signals an arc-flash relay.
SLD / Schematic
Symbols · AF
Arc-flash fibre loop sensor
Bare optical fibre routed through switchgear that picks up arc light anywhere along its length.
In plain English
What does Arc-flash fibre loop sensor mean?
A fibre loop sensor is an unjacketed optical fibre routed through busbar chambers or along switchgear lines. Light from an arc anywhere along its length enters the fibre and reaches the arc-flash relay, so one loop can cover a large area that would need many point sensors.
A simple example
Because the whole length is sensitive, a loop identifies the zone but not the exact compartment, and the trip zone therefore follows the routing. Loop length affects sensitivity, and the symbol does not show routing, length or the loop-check function, which should be recorded on the layout and schematic.
What the drawings help you do
Read the routing drawing to see which compartments the loop crosses. Check that the trip zone matches the loop coverage. A fibre loop covers a long area without locating the arc precisely; a point sensor watches one compartment.
This particular reference
Bare optical fibre routed through switchgear that picks up arc light anywhere along its length. A fibre loop covers a long area without locating the arc precisely; a point sensor watches one compartment.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: SEL-C804 multimode arc-flash detection fibre-optic cables
SLD / Schematic · AF
What it represents
A fibre loop sensor is an unjacketed optical fibre routed through busbar chambers or along switchgear lines. Light from an arc anywhere along its length enters the fibre and reaches the arc-flash relay, so one loop can cover a large area that would need many point sensors.
Because the whole length is sensitive, a loop identifies the zone but not the exact compartment, and the trip zone therefore follows the routing. Loop length affects sensitivity, and the symbol does not show routing, length or the loop-check function, which should be recorded on the layout and schematic.
How to read it
- Read the routing drawing to see which compartments the loop crosses.
- Check that the trip zone matches the loop coverage.
Information to show or reference
- Show loop routing
- State loop length
- Reference relay channel
A distinction that matters
A fibre loop covers a long area without locating the arc precisely; a point sensor watches one compartment.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
SEL-C804 multimode arc-flash detection fibre-optic cables
Public manufacturer page describing fibre arc-flash sensors for large areas such as bus compartments.
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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