A protective relay stores three kinds of record: the time-stamped event list (SOE, or SER in SEL relays), the fault record with the trip quantities, and the oscillography, which is the waveform of currents, voltages and binary signals. They are downloaded with each manufacturer's software and, to analyze them with any tool, exported in COMTRADE format. After a trip, they must be downloaded before resetting or changing settings.
What a relay keeps after a trip
A numerical relay records what it saw around each pickup or trip. Although each manufacturer uses different names, the records are of three kinds:
| Record | What it contains | What it is for |
|---|---|---|
| Events or SOE (SER in SEL) | Chronological list of status changes: pickups, trips, binary inputs, breaker position, alarms | Rebuilding the order of what happened |
| Fault record (event summary) | Date and time, faulted phases, fault currents, function that tripped, estimated distance to the fault | A quick first reading of the trip |
| Oscillography or disturbance record | Samples of currents and voltages and digital signals, from before the fault until after clearing | Analyzing the cause: fault type, direction, saturation, times |
All three are stored in the relay’s non-volatile memory, which has limited capacity. When the memory fills up, new records replace old ones according to each device’s logic; that is why a trip that is not downloaded in time can be lost after a series of recloses or switching operations.
What gets recorded depends on how the recorder was configured when the relay was placed in service: which signals trigger it (a trip, a protection pickup, a binary input), how many pre-fault and post-fault cycles it keeps, which analog and digital channels it includes and at what sampling rate. A badly configured recorder delivers short oscillography, without the signals that matter or without the clearing instant. Reviewing that configuration is part of relay commissioning, not of the later analysis.
What each brand downloads
- SEL: the relay stores event reports and the sequential events recorder (SER). The report can be downloaded in SEL ASCII format (EVE), in compressed format (CEV), which includes the state of all relay bits, or in COMTRADE on the models that support it. They are retrieved with AcSELerator QuickSet and analyzed with SEL Synchrowave Event, which reads CEV, EVE, SER and COMTRADE and exports to COMTRADE.
- Siemens SIPROTEC: fault records and event logs read with DIGSI; the analysis is done with SIGRA, which shows the records in several views, calculates quantities such as impedance and reads COMTRADE.
- ABB and Hitachi Energy Relion: the disturbance recorder keeps the records in non-volatile memory to be downloaded with PCM600, which delivers them in COMTRADE.
- Schneider MiCOM and Easergy: fault, event and disturbance records, downloaded with Easergy Studio or Easergy Pro.
- GE Vernova Multilin: events and oscillography in COMTRADE with EnerVista.
To download them you connect to the relay with its brand’s software, as explained in how to connect to a protective relay. When the substation has an engineering network, these records can be collected automatically on a server; we explain it in automatic collection of oscillography and events.
COMTRADE: the common format
The COMTRADE format, defined by the dual-logo standard IEC/IEEE 60255-24:2013 (IEEE C37.111), is what lets you open a record from any brand in any analysis tool and play it back with an injection test set. A record has a configuration file (.cfg) and a data file (.dat), with two optional ones (.hdr and .inf), or all four together in a .cff file. We cover it in detail in COMTRADE files.
You can open the record in your browser with our free COMTRADE viewer: the file is not uploaded to any server.
What to keep after a trip
The order matters. Before resetting targets, reclosing or touching settings:
- 01TargetsNote LEDs, display messages, 86 flags and SCADA alarms
- 02EventsDownload events and SOE from every relay involved
- 03OscillographyDownload fault records and oscillography, in native format and in COMTRADE
- 04SettingsSave the current settings of each relay
- 05Other recordsGather those of the remote end and of the fault recorder, if any
- 06ResetReset only after everything is saved
Some reasons:
- The time. If the relays are not synchronized, the records of two devices cannot be compared. Note the relay time against a reliable reference; see sequence of events and event reports.
- The native format. The manufacturer’s format usually carries more internal signals than the exported COMTRADE, such as the state of the logic bits. Keep both.
- The settings. An analysis without the settings in force at the moment of the trip is incomplete; if someone changes them afterwards, nobody will know which settings the relay acted with.
- The other end. On lines, the record from the remote end and from the teleprotection shows what a single relay cannot see.
- Erasure. Some maintenance actions, such as clearing memories or loading a new configuration, delete records. In numerical relays, resetting targets and clearing records are usually separate commands, but confirm it in your model’s manual before resetting. If a lockout relay 86 operated, its reset also waits until collection is finished. The full order is in resetting a relay after a trip.
What to look for in the records
With the records in hand, the general questions are:
- What fault occurred: faulted phases, ground involvement, magnitude and duration.
- Who saw it and who tripped: which function picked up, which tripped and with what time.
- Whether the operation was correct: whether the protection that should trip did, in the expected time, and whether there were trips that should not have happened.
- Whether the breaker responded: time between the trip command and current interruption in each pole.
- Whether there was a reclose and how it ended.
The step-by-step reading of the waveform is in how to read a fault oscillography.
We analyze your trip
If the records show a trip with no clear explanation or an operation that should not have happened, at Tiza Group we review the relay settings and logic remotely with our remote relay configuration. For a formal analysis of the event, send us the events, the oscillography and the settings and we will quote a relay trip analysis: what happened, whether the protection operated correctly and what to change.
Related guides
- How to read a fault oscillography step by step
- COMTRADE files: .cfg, .dat, .hdr and .inf
- Sequence of events (SOE/SER) and event reports
- Automatic collection of oscillography and events
- Digital fault recorder (DFR) and PMU: COMTRADE and synchrophasors
- SEL AcSELerator QuickSet, Architect and Grid software
- Siemens DIGSI 4 and DIGSI 5 software
- Relay access levels and passwords
References
- IEC/IEEE 60255-24:2013 (IEEE C37.111-2013), Common format for transient data exchange (COMTRADE) for power systems.
- SEL, Synchrowave Event (SEL-5601-2), supported formats: COMTRADE, CEV, EVE and SER. https://selinc.com/products/5601-2/
- Siemens, SIGRA and DIGSI documentation.
- ABB, 615 series technical manuals (disturbance recorder).
- IEEE C37.233-2023, Guide for Power System Protection Testing.
Frequently asked questions
What is the difference between the event report and the oscillography?
The event report or SOE is a list of status changes with their time: pickups, trips, breaker position and alarms. The oscillography is the sampled waveform of currents and voltages, with the binary signals, for a few cycles before and after the trip. The first tells you what happened and in what order; the second tells you why.
Why doesn't the oscillography I downloaded contain the trip?
The record may have been overwritten by later events, the trip may not have been among the configured recorder triggers, the pre-fault and post-fault duration may be short, or the relay that tripped may be a different one. Check the time as well: a relay without time synchronization can store the record with a different date.
Can I open a file from an SEL relay with another brand's software?
Each brand's native format, such as SEL's compressed CEV event report, opens with its own software. To use another tool, export it to COMTRADE, the common format of IEC/IEEE 60255-24 (IEEE C37.111), which analysis programs and test sets read.