AbstractThe possibility for pre-grading of logs throughout the year has been evaluated based on dynamic modulus of elasticity (MOEdynor simplifiedEdyn) by means of frequency-based nondestructive testing (NDTfreq). The challenge is thatEdynis variable in the frozen, partly frozen, and unfrozen states of logs (state of matter). In the unfrozen state, NDTfreqis reliable if the moisture content does not fall below fiber saturation. The state of the matter was tested via temperature measurements of air and log by means of an infrared technique and sensors, and information was evaluated from NDTfreq. The temperature measurements proved to be inefficient for industrial application because of unreliable data and long measurement times, whereas the NDTfreqmeasurements allowed the determination of meaningful damping factors. A sufficient level of predictability for more than 60% of the measurements was found. The log measurements in the partly frozen state are inconclusive becauseEdyndata fluctuate in the presence of both liquid and frozen water. For the completely frozen logs, a correction is introduced as a precaution that avoids an overestimation ofEdynin the unfrozen state.
Frequency Response Quality Index for Assessing the Mechanical Condition of Transformer Windings
