Probabilistic analysis of gear flank micro-pitting risk in wind turbine gearbox using supervisory control and data acquisition data

This study investigates the probabilistic risk of gear tooth flank micro-pitting in wind turbine (WT) gearboxes and shows how relatively slow rate of supervisory control and data acquisition (SCADA) data, recorded during operation, can be used to analyse the onset of gear surface damage. Field measured time series of SCADA signals, including wind speed, generator power and rotational speed, were used to obtain the statistical variation of gear shaft torque and rotational speed. From the SCADA data obtained over a 2.2 year period random number datasets of smaller sizes were selected. Based on these random number datasets the effect of gear shaft torque and rotational speed variations on the probabilistic risk of gear micro-pitting was investigated. Determinations of the gear tooth flank contact stress and lubricant film thickness were based on the technical report of gear micro-pitting, ISO/TR 15144-1 (2010). The study has shown that the considered pinion gear is subjected to high load conditions resulting in high contact stresses. The variation of rotational speed causes greater sliding between the gear teeth. The results of specific lubricant film thicknesses have shown that there is considerable risk of gear micro-pitting under the operational conditions recorded from the SCADA field data.