Structural health monitoring of wind turbines:

Monitoring systems for rotor blades,

towers and foundations

Strukturüberwachung an Rotorblättern,

Türmen und Gründungen

von Windenergieanlagen

Presented by

Dr.-Ing. André Schäfer

HBM Hottinger Baldwin Messtechnik

HBM: public

At „Offshoretage 2016“, Berlin

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OFFSHORE DAYS 2016, 17/18.03.2016 in Berlin

„SHM at Rotor blades, towers and foundations of wind turbines“-> Oral presentation by Dr.-Ing. André Schäfer

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Long history of HBM in wind energy applications

2Torque transducer T30FN Amplifier KWS Plot

did first contributions to wind energy:

Already on the famous "Growian” wind

turbine in Marne; Germany, HBM strain

gauges, sensors & instruments were used.

Source: NDR, Germany

as early as 1978

HBM: public

Hottinger Messtechnik -founded in 1950-

later Hottinger Baldwin Messtechnik (HBM)

Our activities in wind covering the whole wind turbine life cycle

Covering topics such as prolonging service life, reducing downtime and increasing

reliability: Structural monitoring of towers, foundations & blades is an important

part of it.

Source: Wikipedia

HBM: public

Design

and Optimize

Test and Verify

Operate,

Monitor

Manufacture,

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Wide scope of solutions

• Structural monitoring of towers, foundations & blades

• Total measurement solution for large scale test stands

• Torque measurement with traceability in the MegaNewtonmeter range

• Electrical measurement of voltage and current

• Specific Onshore, Offshore solutions

Measure and Predict with Confidence

© shutterstock

© shutterstock

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Encouraging progress in component tests

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• Membership in task 35 of “IEA Wind”

“Ground Based Testing for Wind

Turbines and their Components”

(Large scale test stands & blade load

assessment)

• Collaborator EU metrology project

EMPIR i26 " Torque measurement in

the MN • m range"

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Genesis High Speed acquisition system enables testing of electrical components like

generators and inverters including the generators‘ overall power and efficiency in

combination with HBM torque transducers. It also allows certification of the inverters

output according to EN61400-21: 2008 Wind turbines – Part 21

Component Test: Generator Test

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• We are conducting wind projects since the

beginning and conducted more than 20

larger projects since then.

• It started in the time that FINO and RAVE

(Research in >>Alpha Ventus<<) paved the

way for Germany’s first offshore wind park..

• With specifically covered electrical strain

gages, as well as FBG 's

(FibreBraggGratings) can be realized and

in all required water depths.

HBM Offshore time line

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HBM experience: offshore wind energy projects

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Year Project

2003 Fino1

2008 OGOWIN

2009 RAVE; Hywind

2010 Walney 1

2011 London Array; ECO1XX onshore / offshore

2012 Forwind; Anholt; Baltic I; Borkum West (Trianel)

2013 Global Tech 1; Doggerbank; ALSTOM onshore /

offshore; Gwynt y mor; WoDS

2014 Borkum; Westermost rough; Universal foundation

2015 Veja mate

Pic. Source: Meerwind Süd / Ost

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Requirements of condition monitoring in offshore environment

• 2007 the Federal Maritime and Hydrographic Authority

(BSH ) has provided in his standard “Design of

Offshore Wind Turbines” that 10 % of the WT of each

wind farm will be equipped with CMS for structure and

foundation

• 2010 German Lloyd Renewables now goes on the

offensive and calls for an expansion of the CMS via

the drive train out : towers and foundations are at the

focus.

• Difficulty compared to the condition monitoring of the

power train is the stochastic and multidimensional

stress and accordingly complicated analysis of the

structure response, which is very difficult to assign a

defined stress condition.

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Together we are working for an extensions of existing minimal CMS only on drive trains

GL Renewables (GL RC) wanted to extent drive train CMS to Blades, Towers and

Foundations for long:

Steingröver , K.; at al. " Condition Monitoring Systems for Wind Turbines : Current status

and outlook on future developments from the perspective of certification " ; VDI report on

“Vibrations in wind turbines", Bremen, 2010

Steingröver , K.; at al. “CMS für Windenergieanlagen aus Sicht der Zertifizierer” Journal

„ECONOMIC ENGINEERING“, issue 5/2012, Göller Publishing house, Baden-Baden

minimal CMS Task Ideas

Extension of CMS to whole structure : Requirement for long

GL wants a clear definition

of the interfaces too

Pic. Source for all 3 pictures: GL Renewables (GL RC); see above mentioned references

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nCode DesignLife is a software tool for fatigue

analysis. The system provides fatigue life

prediction from finite element analysis to

durability and certification analysis - before

production of a prototype-

Strength:

• Many components can be investigated,

even blades

• Predict fatigue damage in the design of

key components of the nacelle such as

gearboxes. Understand the structural

loading envelope.

• Monitor operational performance and

identify statistical trends.

• Assess the reliability and structural

integrity of systems for long-term

operation.

Durability & lifetime prediction by HBM nCode DesignLife

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Overview of our Scope

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© H

BM

Monitoring Service Provider

Life data (web log)

Remaining Lifetime Reports

0

5

10

15

20

25

1 3 5 7 9 11 13

Service Provider

Extension of CMS: Structural Health Monitoring (SHM)

Inclination, acceleration

Wave, Scour (Kolk), Grouting

Operator Expert

FE design

modelServer

Strain,

underwater

Install sensors and collect operational data over years

- synchronized

- centralized

- organized

- qualified

nCode Software

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… over

damage at each

location on the

Nacelle …

… and

list of data files

for

the chosen

location…

…to

detailed Reports for

the critical day /

period.

Extensions of CMS: New position of HBM SHM

Visualize life data

(web based)

Monitor limits

Generate reports

Key arguments for HBM Monitoring Solutions :

• Monitoring increases safety generating additional information

• Monitoring data allow improvement of structures

• Monitoring can reduce maintenance work

• Monitoring data help increasing lifetime

Possibilty to offer “Standard” Packages

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© H

BM

• Weighing of wind turbine structures (Tripod) according to international guideline DIN EN ISO19901-5, measure load and balance point, example Bremerhaven

• Measurement of vibration on wind turbine structures (Tripod) already in compliance with the expected

guideline VDI 4551

• Traceability of tightening torque on wind turbine structures according to guideline DKD R3-7, example Vestas DK

Some other tasks standards/guidelines are important

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Important for SHM: HBM FiberSensing optical range

Relevant optical standards for wind energy:

VDI/VDE-Guideline 2660 „Experimental stress

analysis – Optical strain sensor based on fibre

bragg grating Fundamentals, characteristics

and sensor testing”, 2010

Currently : HBM contributes to FA 2.17 of VDI,

working out the VDI/VDE-guideline for FBG-

Temperature sensors, standard expected for

2016/2017 via TU Ilmenau

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Structural Health Monitoring:

BAM and University of Technology

Berlin drive work in committee toward

VDI 4551 (guideline defining SHM

systems for “offshore structures)

BSH Germany published a new

guideline “Design of offshore wind

turbines” by 2015.

BSH drives the European

standardization.

© H

BM

2014 - Hottinger Baldwin Messtechnik GmbH (HBM) announced the

acquisition of

FiberSensing –

Sistemas Avancados de Monitorizacao S.A. (FiberSensing),

In Porto, Portugal

a leading provider of Fiber Bragg Grating (FBG) based measurement

and monitoring systems for critical physical assets with Wind energy

as one of the main targets.

HBM FiberSensing

HBM: public

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Phase 1: Wind Blades Design / R&D Phase 2 & 3 : Monitoring solution

Blade Monitoring Strengthening all phases of wind turbine life cycle

Design validation consisting of:

1: Embedding of bare fiber array and

surface gluing of composite sensors

2: Load test

Is a reliable monitoring

solution specifically designed to monitor

wind generator blades.

WindMETER can be integrated into:

• Pitch control

• Condition monitoring

• Load assessment

• Blade design validation

• Vibration monitoring

• Ice Detection

WindMETER - Optical Wind Blade Monitoring

HBM: public

• Electromagnetic Immunity

• Large distances, low damping

• Easy installation

• Withstand high pressures (tested up to 400bar)

• Water resistant

• Not much cabling (Daisy chain)

• No electric supply voltage (ATEX)

• Low mass (and thus low mass moment)

• High number of load cycles

• Withstands aggressive media

Advantages of optical solutions, especially for wind energy

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• FS Line: FBG Strain sensors FS62

• OP Line: FBG Sensors for High strain applications

OL, OL-LT, OR, OL-W, OR-W (OTC)

About HBM optical range of products (I)

• ± 1500 μm/m,

± 2500 μm/m,

± 5000 μm/m

• -20 bis 80 ºC

Linear Low

Temperature

Rosette Weldable

Linear

Weldable

Rosette

Temperature

Compensation

Polymide Athermal Composite Weldable Embedded Surface

• ± 5000, ± 10000, ± 20000 μm/m

• -10 to 80 ºC, -40 to 80ºC, -40 to 100 ºC

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FS64 FS65

• -20 bis 80 ºC

• (20 bis 150 ºC)

• FS Line: FBG Temperature sensors

FS63

•

• FS Line: FBG Accelaeration- and Tilt sensors

About HBM FiberSensing optical range of products (II)

Accelerometer

Weldable Composite Embedded High Temperature

• ± 10 g

• 0 bis 50 Hz

• -20 bis 80 ºC

Tilt

• 10 deg (±5 deg)

• Push-pull Konfiguration

• -20 to 80 ºC

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• OP Line: Strain-Arrays

Optimet-OMF, Optimet-PKF, PKF OTC

About HBM FiberSensing optical range of products (III)

Ormocer Coated PEEK Embedded Temp. Compensation

• über±5000 μm/m (> 107 Zyklen))

• -269 bis 200 ºC, -40 bis 140 ºC

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HBM optical interrogators (I)

19” (2U)Standard

FS22 SI & FS22 DI

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Static Dynamic

Range 100 nm ( [1500; 1600] nm )

Sampling Rate

(Limitations)

1 S/s

(Not Applicable)

501, 1002, 2003 und 5004 S/s

1 (127 Sensors/K. in total of 800)2 (127 Sensors/K. in total of 400)3 (127 Sensors/K. in total of 200)

4 (63 Sensors/K. in total of 80)

No. of channels 1, 4 or 8

Sensors per channel25 (typ. )

(same pitch, max. measuring range ±2 nm pro Sensor)

Res. 2 pm 10 pm

OSA Trace

(1/s)20k points 7k points

Working temp. range [10; 40] ºC

Interface Ethernet (TCP/IP)

Sleep Mode Yes No

Local Data Logging Yes No

HBM optical interrogators (II)

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Monitoring system for wind generators

Structural health monitoring

− Blades (transport, operation)

− Tower

− Foundations (on-shore, off-shore)

Suitable for integration on systems for

− Operation control: IPC (Individual Pitch Control)

and ice detection

− CMS (Condition Monitoring)

WindMETER System

HBM: public

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Interrogator

WindMETER System

Range 80 nm (1510 to 1590)

Resolution 1.0 pm

Absolute accuracy 10 pm

Sensors per channel 8 (typical)

Optical channels 3 (typical)

Sample rate 100 S/s

Interface Ethernet (TCP/IP)

Commands SCPI (ASCII textual strings)

Communication Protocol CANopen, Profibus or other upon request

Operation temperature -20 to 60 ºC

Power Consumption 15 W

HBM: public

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Sensors

WindMETER System

Strain Temperature

Range 5000 μɛ -20 to 80 ºC

Sensitivity (typical) 1.2 pm/ μɛ 10 pm/ºC

Resolution 1 μɛ 0.1 ºC

Absolute accuracy 8 μɛ 1 ºC

Sensors per channel 4 4

Sensor

Code

Central

Wavelength

Strain - WMSG1 1517.5 nm

Temp. - WMTS1 1527.5 nm

Strain - WMSG2 1537.5 nm

Temp. - WMTS2 1547.5 nm

Strain – WMSG3 1557.5 nm

Temp. – WMTS3 1567.5 nm

Strain – WMSG4 1577.5 nm

Temp. - WMTS4 1587.5 nm

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Typical configuration in a daisy chain

WindMETER System

Power24VDC

Ethernet

optical fiber

Profibus

Blade 1

WMSG1 WMSG2 WMST2

Blade 2

Blade 3

WMST1 WMSG3 WMST3 WMSG4 WMST4

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• Communication between HUB and NACELLE

WindMETER System

Via SLIP RINGS

OPTION ASlip Rings

OPTION BWi-Fi

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Competitive advantages:

WindMETER System

Vs. Conventional technology

Vs. Other optical technologies

Passive sensors – immunity to lightning

Internal spectral reference – long term accuracy

Fatigue resistant Auto adjustment every 10 ms - no need for recalibration

Multiplexing – different parameters using the same interrogator

80 nm range – large sensor count

Less cabling – several sensors in the same line

Immunity to polarization effects – signal stability

High strain High reflectivity sensors (>70%) – no limitation in distances

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To be continued…

At a glance: vision of a completely optical SHM solution

Monitoring Live data (web log)

Reports

0

5

10

15

20

25

1 3 5 7 9 11 13

Tilt, Acceleration

FE Design

ModellServer

Operator Expert/ Certifier

SCADA

Row

data

4 times each 90°

ɛ T

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• www.hbm.com/windenergy

More detailed information

http://windfair.net/hbm

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White papers

Posters at EWEA

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• It is far not enough to only monitor the drive train. Towers, foundations and even blades

must be monitored as well. Thus extensions as SHM or Blade Monitoring are especially

interesting because of the possibility of life time extensions for wind turbines .

• VDI 4551 guideline is an important progress for SHM. Content of the guideline will give

detailed requirements, as numbers of sensors types of sensors such as acceleration,

inclination, strain as well as specs for electronics (time sync, bus requirements, etc.).

Finally the guideline will hopefully be applied by the wind turbine manufacturers.

• Optical solutions are an advanced technology: not only for the blades, but also for SHM

on towers and foundations

Conclusion:

HBM: public

Source: Shutterstock

measure and predict with confidence

www.hbm.com

Dr. Ing. André Schäfer

Application Manager

wind energy applications

HBM Test and Measurement

Darmstadt

Phone: +49 6151 / 803 224

Email: andre.schaefer@hbm.com