Rice 2016 sandia blade workshop presentation ben rice

1. Lightning Detection – Strategies for Monitoring
& Integrating Into a Blade Maintenance Program
Ben Rice
Sandia 2016 Wind Turbine Blade Workshop
August, 2016

2. Pattern Energy Introduction
Current Operating Capacity: 3,300 MW
Number of Turbines: 1,550
Turbine Manufacturers in Fleet: Siemens (65%), Mitsubishi (10%), GE (25%)

3. Agenda
§ Starting Early: The In-Warranty Force Majeure Paradox
§ Budgeting for Lightning
§ Lightning Monitoring Strategy
§ Proactive Targeted Inspections
§ Periodic Sampling Inspections
§ Damage Categorization & Tracking

4. The In-Warranty Force Majeure Paradox
Warranty Period à Lower Risk to the owner

5. The In-Warranty Force Majeure Paradox
Warranty Period à Lower Risk to the owner
AND…
Lower Risk à More hands-off approach with little to no self-perform
maintenance strategy

6. The In-Warranty Force Majeure Paradox
Warranty Period à Lower Risk to the owner
AND…
Lower Risk à More hands-off approach with little to no self-perform
maintenance strategy
BUT…
A Force Majeure event is not a warranty claim and is a risk ONLY to the owner

7. The In-Warranty Force Majeure Paradox
Warranty Period à Lower Risk to the owner
AND…
Lower Risk à More hands-off approach with little to no self-perform
maintenance strategy
BUT…
A Force Majeure event is not a warranty claim and is a risk ONLY to the owner
SO…
The owner must have a maintenance strategy to identify and mitigate the effects
of force majeure events as well as be able to differentiate force majeure from
turbine deficiencies and manufacturing defects

8. Force Majeure à Lightning Damage

9. Force Majeure à Lightning Damage
Lightning Damage Events
In most regions of the U.S., lightning is an inevitability, with high
probability of strikes to turbines.
Lightning Protection Systems are designed to capture the
majority of lightning events and pass to ground, with the threshold
for testing at 98%.
For manufacturers, lightning damage that occurs to a blade is a
force majeure claim automatically, since the LPS is expected to
safely pass to ground any strikes within design specifications.

10. Force Majeure à Lightning Damage
Lightning Damage Events
In most regions of the U.S., lightning is an inevitability, with high
probability of strikes to turbines.
Lightning Protection Systems are designed to capture the
majority of lightning events and pass to ground, with the threshold
for testing at 98%.
For manufacturers, lightning damage that occurs to a blade is a
force majeure claim automatically, since the LPS is expected to
safely pass to ground any strikes within design specifications.
Particularly for older turbines, there is no remote indication of a
strike occurring, and the manufacturer has little incentive to
monitor for damage that is outside the scope of the warranty
So…the owner is placed in the position of monitoring for damage
at an early stage before it moves from a lower cost repair
situation, to a full replacement requirement.

11. Budgeting for Lightning Spending
One month of lightning in West Texas!

12. Budgeting for Lightning Spending
Before building a project, it is useful to do a lightning risk profile making basic
assumptions about:
§ Estimated strikes per turbine per year
§ Number of inspections required
§ Cost per inspection
§ LPS effectiveness rate (and therefore number of expected damages)
§ Cost per repair and replacement

13. Budgeting for Lightning Spending
Example (all numbers are hypothetical):
§ Number of turbines = 100
§ Estimated strikes per turbine per year = 5
§ Number of inspections required = 20
§ Cost per inspection = $500
§ LPS effectiveness rate = 99%
§ Cost per repair and replacement = $10,000 (repair) / $150,000 (replace)
Total annual budget for lightning & inspections = ~$60,000 – $150,000

14. Retrieving Lightning Data
Lightning Data available through Vaisala’s National Lightning Detection
Network (NLDN)
§ Accessible via Vaisala directly or third party applications
§ Allows for historical lightning data with recorded metrics:
– Lat/Long coordinates of strike
– Confidence of strike location accuracy
– Max amplitude of the strike’s current (kAmps)
§ Metrics needed but missing:
– Total energy transferred by the lightning strike (Joules)
– The rise time (in seconds) from zero to peak current

15. Lightning Monitoring Strategy
Options Available
§ Proactive Targeted Turbine Inspections
– Identify high risk turbines for one-off inspections after major storms and
weather events
– Too resource intensive to check all turbines!
§ Annual/Periodic Sample Inspections
– Intended for those turbines missed by proactive inspections
– Internal or contracted 3rd party
– Goal is to inspect a subset of the turbine population each cycle so that
the full fleet is covered by the Nth cycle

16. Proactive Targeted Inspections
WTG 1 WTG 3
WTG 2
Strike 1
Strike 2
99% Confidence Ellipse
150m

17. Proactive Targeted Inspections

18. Proactive Targeted Inspections
HighestLowest
Likelihood of Damage

19. Lightning Monitoring Strategy
Options Available
§ Proactive Targeted Turbine Inspections
– Identify high risk turbines for one-off inspections after major storms and
weather events
– Too resource intensive to check all turbines!
§ Annual/Periodic Sample Inspections
– Intended for those turbines missed by proactive inspections
– Internal or contracted 3rd party
– Ground-based, on ropes/platform, or drone
– Goal is to inspect a subset of the turbine population each cycle so that
the full fleet is covered by the Nth cycle

20. Periodic Sampling Inspections
Periodic Inspections
Year 1 – 33% Sample Inspection (WTGs 2 & 6) --- Fleet 33% Complete
2
6

21. Periodic Sampling Inspections
Periodic Inspections
Year 2 – 33% Sample Inspection (WTGs 1 & 4) --- Fleet 66% Complete
1
4

22. Periodic Sampling Inspections
Periodic Inspections
Year 3 – 33% Sample Inspection (WTGs 3 & 5) --- Fleet 100% Complete
3
5

23. Damage Categorization & Tracking
Sample Damage Scale Categorization
Ultimately, the goal is to catch damages while they are still cost-effectively
repairable, and to compile a list of turbines that need to be monitored and
revisited to ensure that damage has not progressed. Both a periodic and a
proactive maintenance strategy aim to achieve this goal.
No Damage
Identified
WTG Taken Offline for
Repair/Replacement
1 5Decreasing intervals of re-inspection for damage progression
Re-inspect in 6
months
Re-inspect in 3
months
Re-inspect in 1
month

24. Damage Categorization & Tracking
Periodic & Targeted Inspections
Historical Inspection Database – Tracking Results and Follow-Up Requirements
OK
OK
OK
Re-inspect
6-months
Re-inspect
3-months Repair
Blade A

25. Summary
§ Lightning typically qualifies as a non-warrantable damage condition, so
vigilance is important to avoid full replacement situations
§ Lightning data is available for quantifying lightning risk profiles and storm-
specific analyses
§ With large turbine populations, full site inspections are impractical, so a
combination of targeted proactive and sampling periodic inspections is
useful in capturing damages and avoiding larger repair/replacement costs
§ Damage categorization is important in standardizing and executing re-
inspection and repair work scheduling

26. Thank You…Questions?
xkcd.com