Abstract
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.
Highlights
Reliability of wind turbines (WTs) has improved considerably in the past decades; WT gearbox bearing and gear failures are still frequent, hindering the optimal operation of multi-megawatt WTs, increasing the cost of wind energy
The simulations considered all the fatigue load cases defined in the International Standard IEC 61400-1 (2005) [16], with wind simulations of strong gusts and 3D turbulent wind conditions chosen according to the appropriate WT design standard of IEC 61400-1 (2005) [16] and the Guideline for the certification of WTs by Germanischer Lloyd (2003) [31]
This study presents a probability analysis of gear tooth flank micro-pitting risk by using recorded supervisory control and data acquisition (SCADA) data of WTs in field operation
Summary
Reliability of wind turbines (WTs) has improved considerably in the past decades; WT gearbox bearing and gear failures are still frequent, hindering the optimal operation of multi-megawatt WTs, increasing the cost of wind energy. Operational factors, resulting from the variable load and speed conditions [6, 7], cause high contact stress, high and negative tooth surface sliding, high surface temperature, insufficient lubrication or disrupted lubrication conditions [8,9,10] These contribute significantly to the occurrence of gear micro-pitting. Considering the importance of the stochastic nature of WT operation and unavailability of fast rate measurement of loading data to cover all seasonal effects, this study investigates probabilistic characteristics of the micro-pitting risk of an HSS pinion gear using SCADA data of 10-minute averaged values. The effects of the shaft torque and rotational speed variation on potential risk of micro-pitting were assessed by investigating probabilistic characteristics of the gear contact stress and lubricant film thickness
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