TFR (Transient Fault Recorder)
Also known as: DFR, Digital Fault Recorder
A device that captures high-resolution voltage and current waveforms during grid disturbances such as faults, voltage dips, and switching events. Grid codes often require a TFR (or its modern equivalent, the digital fault recorder) at the point of connection, with recordings stored in IEEE C37.111 COMTRADE format for post-event analysis.
In energy storage
TSOs may request TFR recordings after any grid event to verify that the BESS responded in accordance with its grid code obligations — for example, confirming that the plant rode through a voltage dip rather than tripping. Recordings are typically stored in COMTRADE format and must be retrievable within a defined timeframe (often 24–48 hours) after a request from the grid operator.