EWEA 2013, Vienna, Austria, 4-7 February 2013

Extraction of blade AE signature for in-service condition monitoringD. J. Lekou, F. Mouzakis (CRES) N. Tsopelas, D. Papasalouros, A. Anastasopoulos (Mistras Group)

EWEA 2013, Vienna, Austria, 4-7 February 2013 2

Current SHM for blades

DamageCracks, erosion,

debonding, lightning, stains, etc.

Rotor imbalance

Inspection procedureVisual inspection (outside,

inside) Damage identification Damage location Off-line, periodic

Vibration Damage identification On-line, periodic

EWEA 2013, Vienna, Austria, 4-7 February 2013 3

Acoustic Emission methodDetection of transient elastic waves

High frequency (>20kHz)Due to rapid release of energy

During crack opening/propagationLocalized Source

Time

Sign

alThreshold

Amplitude

DurationRise Time

CountsCounts to peak

SourceAE wave

Load

Load

SensorAE system

EWEA 2013, Vienna, Austria, 4-7 February 2013 4

Acoustic Emission & blades

Successfully used in laboratory tests

Static & Fatigue On-line measurements

Under loadIdentification of damage

Location of damage

Overall linear location of AE sources

1 2 3 4 5 6 7 8 9 10 11

14 15 16 17 18

Failure area Small cracks

Bubbles

0

500

1000

1500

2000

2500

3000

3500

4000

0 2 4 6 8 10

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10Blade radius (m)

Even

ts

EWEA 2013, Vienna, Austria, 4-7 February 2013 5

Demonstration on CRES NM750kW

Global WT measurements WT operational

Power, rotor speed, etc.Wind inflow

Acoustic EmissionMicro-II PAC8 channels

3 PAC-R6I-AST (60kHz) 5 PAC-R15I-AST (150kHz)

EWEA 2013, Vienna, Austria, 4-7 February 2013 6

General layout

VIRTUAL DESKTOP ON REMOTE LOCATION TERMINALS

1.22 m

0.5 m

0.75 m

0.75 m

1.0 m

PAC SAMOS MICRO II

WIRELESSROUTER

CH6

CH7

CH8

STRAIN GAUGE

CH5

CH4 CH2

CH3 CH1

MaxStrainPositio

nMin

StrainPositio

n

EWEA 2013, Vienna, Austria, 4-7 February 2013 7

Indicative resultsA

E A

mpl

itude

W

T P

ower

Time

Win

d S

peed

EWEA 2013, Vienna, Austria, 4-7 February 2013 8

40 45 50 55 60 65AE Amplitude

1

10

100

1000

10000

Dur

atio

n

Footprint of healthy operation

0 200 400 600 800WT Power (kW)

-200

0

200

400

600

800

1000

Max

/min

WT

Pow

er (k

W)

0 200 400 600 800WT Power (kW)

0

20

40

60

AE

Ene

rgy

0 200 400 600 800WT Power (kW)

-0.5

0

0.5

1

1.5

2

2.5

Max

Yaw

Pow

er (k

W)

EWEA 2013, Vienna, Austria, 4-7 February 2013 9

Conclusions & Future Work

AE for on-line monitoring appliedFootprint of healthy blade capturedFurther applications necessary to capture progressing failure

Tuning with classic inspections

Healthy operation, retrofitting

Healthy operation, Embedded

Known damage, retrofitting

Capture damage, Embedded

Indicative future steps

Application

EWEA 2013, Vienna, Austria, 4-7 February 2013 10

Thank you for your attention

Questions?

AcknowledgementFor this research funding has been received from the EC FP7 under GA no 239462 (NIMO)