In short. After a trip, the relay’s records tell the story: what tripped, in what order, and what the currents and voltages looked like. Good records need synchronised clocks, sensible alarm design and a habit of retrieving data before it is overwritten.
Types of record
| Record | Contents | Use |
|---|---|---|
| Alarms | Conditions needing operator attention | Early warning, status |
| Sequence of events (SOE) | Time-stamped state changes, such as pickups, trips, breaker positions | Order of events across devices |
| Disturbance (fault) records | Waveforms of currents and voltages before, during and after a fault | Fault type, magnitude, clearing time, CT behaviour |
| Fault reports | Summary of fault current and location estimates | Quick triage |
| Trend data | Slow values such as load and temperature | Condition monitoring |
Time synchronisation
Records from different relays are only comparable if their clocks agree. Use a common time source and check drift. Without it, the order of events across devices can be unclear.
Alarm design
- Classify alarms by priority so operators see what matters first.
- Avoid alarm floods: group related alarms and suppress repeats.
- Include clear text, not only codes.
- Test alarm paths from relay to display.
Post-trip analysis
- Secure the records: download event logs and waveforms before they are overwritten.
- Establish the sequence: which relay picked up first, which tripped, which breaker opened.
- Read the waveforms: fault type, magnitude, duration, presence of CT saturation or DC offset.
- Compare with settings and coordination: did the right device trip in the right time?
- Inspect equipment before re-energising.
- Record findings and corrective actions.
Storage and access
Define how long records are kept, who can retrieve them, and how they are backed up. Waveform memory is limited, and new events can overwrite old ones.
Illustrative example
A generator trips during a motor start. The event log shows an undervoltage pickup, followed by a trip after a delay. The waveform shows voltage falling to a level for longer than the delay setting. The team lengthens the delay and starts the motor with a soft starter, and the next start passes without a trip.
Why records matter
After a trip, the question is what happened first. Time-stamped event logs and waveform records answer it, and shorten both the outage and the repeat risk.
Types of record
| Record | Content | Use |
|---|---|---|
| Event log (SOE) | Time-stamped alarms, trips, breaker operations | Reconstruct sequence |
| Disturbance record | Waveforms of currents and voltages before, during and after | Diagnose fault type and relay behaviour |
| Fault report | Summary of fault type, magnitude, location estimate | Quick diagnosis |
| Trend data | Slow-changing values | Spot degradation |
Setting up records
- Synchronise all relay clocks to a common time source so events line up.
- Choose trigger conditions: protection start, trip, breaker status change.
- Allow sufficient pre-fault and post-fault time.
- Name signals clearly.
Alarm management
Too many alarms hide the important ones. Classify alarms by priority and action, remove nuisance alarms and define who responds. A short list with clear actions works better than a long list nobody reads.
After an event
- Download records before they are overwritten.
- Review sequence and relay response against the intended design.
- Write up cause and corrective action.
See remote monitoring.
Common mistakes
- Resetting relays before downloading records.
- Clocks not synchronised.
- Alarm floods that hide the cause.
What to send us
Send relay models and a trip description. Send your application details. See also remote monitoring.
Questions engineers ask
What is a disturbance record?
A waveform capture of currents and voltages around a fault event.
Why does time sync matter?
So events from different devices can be placed in the right order.
How long are records kept?
Only until memory fills. Download them promptly.
Can records prove a relay worked correctly?
Yes, by comparing pickup and trip times with the settings.
This guide gives general principles. Retrieval details depend on the relay model.