An operational trace records what a measurement system observed at a particular time. It can show changes in voltage, power or machine behaviour, but it does not automatically establish why those changes occurred. Context is essential.
Useful evidence includes the operating state of the turbine, the location of the measurements, time synchronisation and any related network events. Comparing those records helps separate a local machine response from a disturbance elsewhere in the system.
Historical field studies are valuable because they connect engineering models with recorded operation. Their conclusions should still be read with the assumptions and limitations stated by the authors. A measured event and a proposed explanation are different parts of the analysis.