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Free online COMTRADE viewer (IEEE C37.111)

SagSwell opens the records that protection relays, digital fault recorders and power-quality meters write in the COMTRADE format, and analyses them in your browser. Drop a .cfg and .dat, a .cff or a .zip on the page and the record is on screen in seconds, with nothing to install.

Open a record No account needed. Demo records included.

What you see, free

  • Waveforms: every analog and status channel on one time axis, with zoom and the value of each trace at the cursor.
  • RMS and disturbances: a one-cycle RMS trend with every sag, swell and interruption found against the IEEE 1159 thresholds, its duration in milliseconds and cycles, and the phases involved.
  • ITIC curve: every event on the ITIC (CBEMA) envelope, with SEMI F47 as an overlay.
  • Harmonics: the spectrum and THD of every channel, only as far up as the recorder’s sampling rate allows.
  • Phasors: fundamental phasors and symmetrical components at any instant of the record.
  • File check: what the reader found in the .cfg and .dat, and anything it had to assume.

With Pro

  • Diagnosis — fault type, direction and the criteria behind it
  • Event replay on a one-line diagram, with the sequence of events
  • PQ timeline — many recorders, one incident
  • Report with waveforms, RMS trends and ITIC
  • Share folders with colleagues by email

See pricing. Pro is $39 a month and the free plan needs no card.

How it works

  1. Add the record. Drag the files onto sagswell.com, or choose them. Files are paired by name.
  2. Read it. The record opens on the waveform; the tabs above hold RMS, ITIC, harmonics and phasors.
  3. Keep it, if you want. Sign in and the files you add are kept in folders in your account, on any computer.

Who it is for

Protection engineers checking how a relay saw a fault, power-quality engineers answering a customer’s complaint about a sag, commissioning and maintenance teams looking at a recorder’s trigger, and anyone who has been sent a COMTRADE file without the vendor software to open it.

Questions

Is SagSwell free?
Yes. Opening records and every measurement — waveforms, RMS with IEEE 1159 sags, swells and interruptions, harmonics, phasors and the ITIC curve — are free on as many records as you like. Pro adds the diagnosis, event replay with the sequence of events, the PQ timeline across several recorders, reports and shared folders.
Do I need to install anything?
No. SagSwell runs in a web browser on Windows, macOS or Linux. Drag the .cfg and .dat onto the page and the record opens.
Are my COMTRADE files uploaded?
Records are read and analysed in your browser. Without an account nothing is kept or uploaded: the files are gone when you close or refresh the page. If you sign in, the files you add are kept in your account, in folders, so they open on any computer until you delete them.
Which COMTRADE versions and files does it open?
Records written to IEEE C37.111 (IEC 60255-24) in the 1991, 1999 and 2013 revisions: a .cfg with its .dat in ASCII, BINARY, BINARY32 or FLOAT32, single .cff files, and .zip archives of either.
Which relays and recorders does it work with?
Any device that writes standard COMTRADE: protection relays, digital fault recorders and power-quality meters. Records that bend the standard, such as dates written mm/dd/yyyy, are read where the intent is unambiguous, and the file check says what was assumed. If a record will not open, you can send it to us so the reader can be fixed.
Is the analysis a substitute for an engineer’s judgement?
No. SagSwell measures and plots what is in the record and shows how each figure was obtained. Conclusions about what happened on the network, and any decision based on them, remain with the engineer who reviews the record.

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