DFR
Disturbance recorder
Recorder that captures analogue waveforms and binary signals before and after a trigger for fault analysis.
SLD / Schematic
Symbols · SOE
Sequence-of-events recorder
Recorder that timestamps changes of state on many binary inputs so the order of operations can be reconstructed.
In plain English
What does Sequence-of-events recorder mean?
A sequence-of-events recorder monitors breaker auxiliary contacts, protection trip outputs, alarms and other binary signals, and stores each change with an accurate timestamp. After an incident the list shows which device operated first, which is often impossible to tell from alarms alone.
A simple example
Timestamp resolution and time synchronisation are what make the record useful. The symbol does not show the time source, such as a GPS clock, or the debounce settings on each input, and without synchronisation records from different devices cannot be merged reliably.
What the drawings help you do
Identify the time synchronisation source. Check which contacts are wired as inputs. An SOE recorder logs binary changes in time order; a disturbance recorder captures analogue waveforms.
This particular reference
Recorder that timestamps changes of state on many binary inputs so the order of operations can be reconstructed. An SOE recorder logs binary changes in time order; a disturbance recorder captures analogue waveforms.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: SEL 2022 Product and Solution Guide: published protection function tables
Schematic · SOE
What it represents
A sequence-of-events recorder monitors breaker auxiliary contacts, protection trip outputs, alarms and other binary signals, and stores each change with an accurate timestamp. After an incident the list shows which device operated first, which is often impossible to tell from alarms alone.
Timestamp resolution and time synchronisation are what make the record useful. The symbol does not show the time source, such as a GPS clock, or the debounce settings on each input, and without synchronisation records from different devices cannot be merged reliably.
How to read it
- Identify the time synchronisation source.
- Check which contacts are wired as inputs.
Information to show or reference
- List monitored inputs
- Show time source
- State resolution and debounce
A distinction that matters
An SOE recorder logs binary changes in time order; a disturbance recorder captures analogue waveforms.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
SEL 2022 Product and Solution Guide: published protection function tables
Public product and function guide including event recording and time synchronisation.
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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