Kevin Alewine: 2013 Sandia National Laboratoies Wind Plant Reliability Workshop

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Understanding Wind Turbine Generator Failures
Modes and Occurrences- 2013 Update

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Kevin Alewine: 2013 Sandia National Laboratoies Wind Plant Reliability Workshop

  1. 1. Understanding Wind Turbine Generator Failures Modes and Occurrences – 2013 Update Kevin Alewine Director of Renewable Energy Services
  2. 2. 2 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Introduction and Credits  Review of generator failure types and root causes  Statistical review of failure occurrences  Some suggestions  Conclusions
  3. 3. 3 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Introduction and Credits Thanks to: William Chen, TECO-Westinghouse Motor Company VonRoll Applications Engineering Group Chuck Wilson, Insulation Integrity Inc. Dr. Peter Tavner, University of Durham, ret. References: Root Cause Failure Analysis, Electrical Apparatus Service Association, 2002-2004 Design Challenges of Wind Turbine Generators , George Gao and William Chen, IEEE EIC - 2009 A Survey of Faults on Induction Motors… , O.V. Thorsen and M. Dalva - IEEE Trans. on Industrial Applications – 1995 Wind Turbine Failure Modes Analysis and Occurrence, Kevin Alewine and William Chen, AWEA Windpower - 2010 Establishing an In-House Wind Maintenance Program, American Public Power Association, 2008 A Review of Electrical Winding Failures in Wind Turbine Generators, Kevin Alewine and William Chen, IEEE DEIS Electrical Insulation Conference - 2011 Magnetic Wedge Failures in Wind Turbine Generators, Kevin Alewine and Chuck Wilson, IEEE DEIS Electrical Insulation Conference - 2013
  4. 4. 4 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Wind turbine generator failure basics  >60GW of wind generators in USA as of 2012  ~45GW of that total has been installed since 2007 utilizing mostly > 1.5MW turbines  In vulnerable designs, generator failures are often occurring in first 3 years of life – obviously well short of expectations  Poor bearing life is the most common cause of generator failure across all sizes and manufacturers. In generators above 1.5MW, the most common electrical failure modes are caused directly by the loss of magnetic wedges  This review covers >2000 failed generators representing over 3.3GW repaired or scrapped from 2005 through June 2013, updated from ~1200 machines surveyed in 2010.
  5. 5. 5 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Generator Failure Root Causes  Design issues – materials and processing, rarely basic mechanical design  Operations issues - alignment, vibration, voltage irregularities, improper grounding, over-speed, transit damage, etc.  Maintenance practices – collector systems, lubrication procedures, etc.  Environmental conditions – weather extremes, lightning strikes, etc.
  6. 6. 6 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Design and Manufacturing Issues  Electrical insulation inadequate for application – normally mechanical rather than electrical weakness  Loose components – wedges, banding  Poorly designed/crimped lead connections  Inadequate collector ring/brush performance  Transient shaft voltages  Rotor lead failures  Sometimes turbine OEMs add components that might complicate service – electronics, lubrication devices, etc.
  7. 7. 7 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Operations Issues  Improper Installation  Voltage irregularities  Traditional sources  Convertor failure or miss-match  Improper grounding  Over-speed conditions  Transit damage  Excessive production cycling
  8. 8. 8 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Maintenance Practices  Cooling system failures leading to heat related failures  Collector ring contamination  Bearing mechanical failure  Bearing electrical failure  Rotor lead failures  Poor alignment  Excessive vibration  Often initiated by heat from failing bearing
  9. 9. 9 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Environmental Conditions  Thermal cycling  Moisture  Contamination  Electrical Storms
  10. 10. 10 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Failure Modes and Occurrences  Rotor insulation damage (strand/turn/ground)  Stator insulation damage (strand/turn/ground)  Bearing failures  Rotor lead failures  Shorts in collector rings  Magnetic wedge failures  Cooling system failures  Other mechanical damage Indicated in the following charts are the occurrences actually recorded, as well as the significance of the mode expressed as a percentage of the total failures studied. The modes collected were:
  11. 11. 11 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Failure Occurrences in Machines <1MW Earlier designed, smaller machines show a high number of failures in rotor insulation. These are due to both electrical and mechanical failure of the conductors and the failure of the banding as designed. Many stator winding failures were actually due to contamination and issues with under-designed bracing. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 25 50 75 100 125 150 175 200 225 250 275 300 Rotor Stator Bearings Other Rotor Leads Collector Rings Cooling System Stator Wedge Percentage Occurrence Generators <1MW (450 total in study) Occurrence % of failures Cumulative %
  12. 12. 12 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Failure Occurrences in Machines 1-2MW The increase in bearing failures among generators between 1 and 2 MW is dramatic. These generators are generally more robust than their antecedents, but proper installation and good maintenance practices are critical to good reliability. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 50 100 150 200 250 300 350 400 450 500 550 Percentage Occurrence Generators 1-2MW (939 total in study) Occurrence % of Failures Cumulative %
  13. 13. 13 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Failure Occurrences in Machines >2MW Again, in the current class of generators greater than 2MW, many of the failures are from bearings, but there is a dramatic rise in stator failures resulting primarily from the loss of magnetic wedges utilized to improve the size/output functionality of the generator design. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 25 50 75 100 125 150 175 200 225 250 275 300 325 Stator Wedge Bearings Stator Rotor Leads Rotor Collector Rings Other Cooling System Percentage Occurrence Generators >2MW (679 total in study) Occurrence % of Failures Cumulative %
  14. 14. 14 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Comparison to General Industry Based on new, unpublished data compiled by Dr. Peter Tavner and his team at Durham University, there is actually little variation in types of major failures, only in specific machine design areas of vulnerability. 0 5 10 15 20 25 30 35 40 45 50 Bearings Windings Other Industrial Wind
  15. 15. 15 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Suggestions  Understanding the failure modes helps us set the priorities for testing protocols  Thermal condition monitoring can be improved  Inspection and cleanliness of the rotor leads and collector systems are also important in DFIG designs  Assure proper materials and processes are utilized to minimize the loss of magnetic wedges after remanufacturing  Bearings and lubrication are critical elements
  16. 16. 16 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Suggestions  Condition Based Maintenance  Should the wind industry move towards CBM?  Many suppliers are focused on this solution  A financial decision – pay now or pay more later  Most other industries have embraced this solution  Requires solid planning, professional implementation and management support  Many resources are available  Excellent study from Sandia National Laboratories on advanced maintenance strategies for wind energy installations “CMMS in the Wind Industry” available on their website  Society of Maintenance and Reliability Professionals (SMRP)
  17. 17. 17 of 1714 August 20132013 Wind Plant Reliability Workshop Alewine Wind Turbine Generator Failures – 2013 Update Conclusions  Bigger is not always more reliable  Maintenance is THE critical factor  Choose your suppliers carefully  OEMs, replacement components and repair – all have key influences on reliability and longevity  An estimated 15% of the entire 60 GW installed fleet has already failed, some of them within 2 years of being placed in service  A very high percentage of these are due to bearing failures, lubrication and other normally preventable issues  Proper maintenance has been shown in other industries to drastically reduce unplanned outages and improve profitability – why not wind?
  18. 18. Questions? Kevin Alewine

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