Bertelsen 2016 08-31 sandia lab-glps_final

1. Lightning Protection: Securing Higher
Reliability and Meeting the New Standards
Sandia National Laboratories – 2016 Wind Turbine Blade Workshop
EMPOWERING YOU TO TAKE CHARGE Kim Bertelsen – Global Lightning Protection Services A/S

2. OUTLINE
1. Introduction
2. News on IEC 61400-24
3. Lightning Damage Analysis
4. Explanations on failure mechanisms
5. Robustness in design
6. Lightning Monitoring
7. Conclusions

3. We are a full service provider in Lightning
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6. EMPOWERING YOU TO TAKE CHARGE
Lightning is predictable, controllable
and the risk is preventable.

7. IEC 61400-24
Wind turbines – Part 24 Lightning Protection
The 1st edition was published in 2010, 2nd version will be issued as a Committee Draft
(CD) in October 2016 following the next meeting in Lisbon, Portugal
• Test is becoming mandatory including High-voltage test and High-current physical
damage testing – not only for blades but for the entire wind turbine application.
• Description of similarity parameters between blade types, where the same LP system
can be used across a blade family without requiring retesting
• The standard includes blade exposure definitions, based on published field data
• Blade zoning/Environmental definitions is required
• Definition of lifetime is required
• Recognition of numerical simulation, but requirements for modelling verification
• Improved risk assessment guidelines including winter lightning and upward initiated
strikes.
• Requirements for Lightning Monitoring – if included
News on IEC 61400-24

8. Lightning Damages
Analysis
508 wind turbines (total power 997 MW) during 5
years operation in central USA
Blade length: 35 – 45 m; 304 damages
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Total damages
Distance from the tip [m]
Fiberglass blades
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Total damages
Distance from the tip [m]
Fiberglass/CFC blades
Source: Anna Candela Garolera et al, IEEE paper

9. Lightning Damages
Analysis
§ Minor surface erosion on receptor
§ should be recorded as successful strikes.
§ This type of impact is not regarded as a damage,
but as wear and tear
§ The receptor itself needs to be replaced in time
§ Shells will need to be restored
§ Receptor durability and replaceability can be an
issue on severe sites with high lightning activity

10. Lightning Damages
Analysis
§ Damage in front of the tip receptor
§ Caused by insufficient insulation of
tip receptor parts inside the tip
§ Easy to repair, but difficult to
improve to avoid repetition.

11. Lightning Damages
Analysis
§ Most common damage close to the tip
§ Caused by insufficient insulation of
conductor system
§ Relatively easy to repair
§ Often the lightning system is left as it
was – resulting in same damage again

12. Lightning Damages
Analysis
§ Attachment through shell to lightning
cable - Shell delamination
§ Caused by insufficient insulation of
conductor system
§ Relatively easy to repair
§ Often the lightning system is left as it
was – resulting in same damage again

13. Lightning Damages
Analysis
§ More severe damage with broken
carbon structure
§ Caused by flash-over from lightning
cable to carbon structure – due to
missing coordination between the two
systems
§ Shells are detached requiring
significant repair work – eventually the
blade needs to be replaced
§ Difficult to improve system during
repair for avoiding repetition

14. Lightning Damages
Analysis
§ Strike to lightning cable through blade
shell resulting in trailing edge
delamination due to high pressure
inside the blade.
§ Caused by insufficient insulation of
conductor system
§ Significant repair
§ Difficult to improve system during
repair for avoiding repetition

15. Lightning Damages
Analysis
§ The analysis shows the distribution of
the lightning damages according to the
damage types described above.
§ It is observed that the most common
type of lightning damage is
delamination, followed by debonding
of the shells.
§ The shell- and tip detachment
occurred only in 2.8% of the cases.

16. Lightning Damages
Analysis
§ The analysis shows the distribution of
the lightning damages according to the
damage types described above.
§ It is observed that the most common
type of lightning damage is
delamination, followed by debonding
of the shells.
§ The shell- and tip detachment
occurred only in 2.8% of the cases.

17. Explanations on failure
mechanisms
§ The lightning event is divided into different stages:
§ Leader Inception – where the turbine develops
leaders due to high electric fields – and send
out leaders toward the incoming lightning.
§ Leaders Interception – where an incepted
leader connects with an cloud leader
§ Current conduction Phase
§ First Return Stroke
§ Subsequent Return strokes
§ Long Duration Stroke

18. Explanations on failure
mechanisms
Downward initiated strikes
Charging Inception Current conduction

19. Explanations on failure
mechanisms
Upward initiated strikes

20. Explanations on failure
mechanisms
§ Likelihood of upward lightning
increases with turbine effective
height
§ Often triggered by intra cloud
discharges
§ Will not appear on public
lightning detection and is
therefore not included in i.e.
§ NLDN from Vaisala

21. Explanations on failure
mechanisms
§ The root cause of most lightning damages are
lightning leader initiation from internal parts –
and not only from intended receptors
Down condutorWeb/spar
Tip receptor base Tip receptor
Initial leader
Cable overlamination

22. Explanations on failure
mechanisms
§ In testing the same
phenomenon is seem
like this

23. Explanations on failure
mechanisms
§ Or like this……
§ In this area there is no
receptors at all

24. Robustness in design
What is robustness?
§ Step 1:
§ We need to implement a LP system where the internal conductive part cannot
incept streamers – which requires careful insulation coordination
§ Only receptors can incept streamers – if the system should work.
§ The LP system needs to pass all high-voltage strike attachment tests and High-
current physical damage tests – to show a strong tip receptor design – as well as
a strong down conductor/interconnector system.
§ Step 2:
§ Robust LP systems need to be well tested to the limits - and beyond to define
design margins.
§ Lifetime tests must be carried out to document that no degradation is taking place
on non-replaceable parts – and to document wear and tear
§ The LP system needs to be maintained regularly based on life time definitions –
and based on accumulated impacts to the specific blade.

25. Robustness in design
Blade Zoning
§ GLPS has suggested a blade zoning concept to focus the efforts to the
near-tip area.

26. Robustness in design
GLPS solutions are inherently robust – and are designed and tested to be
electrically independent on the blade structure.
§ Fully tested, meeting the requirements in the future IEC standards:
§ 200 kA
§ 10 MJ/Ω
§ 3.500 C
§ On request a GLPS solution can meet extended requirements for longer life
time or i.e. winter lightning conditions
§ +200 kA
§ 20 MJ/Ω
§ 25.000 C
§ GLPS solutions comes with a component certificate and should always be
certified together with the specific blade type – new or existing.

27. Carbon- and Complex blades
§ Carbon blades and complex blade including sensors, deicing systems etc.
needs special attention.
§ No other electrical systems in the blade can be kept floating, but needs to be
carefully integrated into the lightning system.

28. Robustness in design
§ The tip solution should ideally be a premanufactured component, that utilizes
all the insulation and conductions capabilities need to demonstrate
robustness in test and real life operation.

29. Robustness in design
§ GLPS tip

30. Robustness in design
§ GLPS side receptor

31. Robustness in
design
§ The tip LP system tested
as a naked system without
blade shells.
§ The same test program as
for a final verification test
needs to be followed and
passed.
§ Here attachment to the
tip receptor

32. Robustness in
design
§ And here attachment to
the side receptor

33. Robustness in design
§ LP system implemented in a blade tip

34. Robustness in design
§ Glue is applied….

35. Robustness in design
§ Retrofit job almost done….

36. Robustness in design
§ Final verification test

37. Lightning Monitoring
Lightning Key Data® System
§ Avoid unnecessary inspections and
expensive downtime
§ Lightning Key Data® System measures
the lightning key figures when it strikes
and provides you with valuable data for
making the best decisions.
§ Peak current [kA]
§ Specific Energy [MJ/Ω]
§ Charge content [C]
§ Maximum rise time [kA/μs]

38. Lightning Monitoring
GPS Antenna Power Supply
SPDs
Power supply entry
Heavy EMC box
Comm. output
Recorder PCB
Sensor cables entry
Amplifiers Sensor shielding clamps

39. Lightning Monitoring
§ Measurement characteristics
§ Current amplitude: +/- 240kA
§ Frequency range (-3dB range): 30mHz - 1MHz
§ Sampling frequency: 10MHz
§ Time frame recorded: 1.5s
§ Length of recorded waveform: 15M samples
§ Trigger level: Adjustable
§ Pre trigger: 100ms
§ Measurement resolution: 16bit
§ Time stamp accuracy: GPS/1ms
§ Backup of data to internal industrial grade SD card
§ Four characteristic parameters calculated from the full waveform
§ Full data set available after each measurement
§ Continuous measurement in full resolution of two subsequent events
§ Recording of all three channels simultaneously

40. Lightning Monitoring
§ The control unit is supposed to be
installed in the hub – or in one of the
blade roots.
§ The sensors can be installed in
different positions depending on the
LP systems configuration
§ Inside blade root on down
conductor
§ On transfer system
§ Around blade

41. Lightning Monitoring
§ Final verification test

42. Lightning Monitoring
§ Parameter output

43. Lightning Monitoring
§ Parameter plots

44. Conclusions
§ Lightning is predictable, controllable and the risk is preventable.
§ A new version of the lightning standard IEC 61400-24 will be released soon.
§ Damages most often occurs to the outermost 1m of the blade, why this should be the
focus. The rest of the blade should not be forgotten – but protection is not so demanding.
§ Robustness in LP systems can be achieved in a good combination between design and
verification.
§ Blade with carbon fiber and complex blades with sensors and deicing systems needs
special attention
§ Online lightning monitoring is available

45. EMPOWERING YOU TO TAKE CHARGEThank you!

46. EMPOWERING YOU TO TAKE CHARGE

48. Contact us
Global Lightning
Protection Services A/S
HI-Park 445
DK-7400 Herning
Denmark
contact@global-lightning.com
+45 70 26 02 11
global-lightning.com