Health Monitoring of Offshore Wind Turbine Structures: Lessons Learned. Presented by Jens Krieger Offshoretage, bis

Transcription

1 Health Monitoring of Offshore Wind Turbine Structures: Lessons Learned Presented by Jens Krieger Offshoretage, bis , Warnemünde

2 Offshore Track Record System implementation, concepts, data evaluation, structural health assessment, consultancy in the Offshore Wind Industry (Monitoring): OWF alpha ventus OWF Borkum West II OWF Nordsee 1 OSS Baltic 2 OWF Meerwind Süd/Ost OWF Butendiek OWF Baltic 2 OWF Nordsee 1 OWF Wikinger OWF Nordergründe OWF Hohe See 2

3 SHM Authority Requirements BSH Standard 2007 vs Representation of the planned inspection of the support structure by a condition inspection system (CMS) for at least 1/10 of the offshore wind turbines In order to monitor the overall behaviour of the foundation elements during the operating phase, parameters, such as shifting, deformation, component stress and frequencies, shall be measured and recorded (monitoring) in the area of the foundation elements at representative offshore wind turbine sites Source: BSH Standard Design,

4 SHM Standards VDI 4551 in progress: Strukturüberwachung und Beurteilung von Windenergieanlagen und Plattformen Vorsitz: Prof. Dr.-Ing. Werner Rücker Content (preliminary): Aims and Tasks of SHM Inspection Strategy and Life Time Prognosis Support Structures and Modelling Periodic Inspections Loads Design Verification, Condition Monitoring, Damage Assessment Measurement Concept SHM Requirements 4

5 SHM Example Concept Global Monitoring Concept Global monitoring for robust structures Ambient Vibration Monitoring (proven technology) Model Based Observer for data interpretation acceleration inclination Few sensors only Accessible positions Lower operational costs acceleration The one monitoring concept does not exist. Implementation depends on monitoring aims. 5

6 Example Data: Correlations Correlations give data plausibility and turbine behaviour Wind Inclination 6

7 Example: Turbine Comparison, Finding the Odd Behaviour Three distance sensors monitor vertical displacement in the grout connection Similar structures in a wind farm show similar behaviour 7

8 Example Data: Threshold Monitoring Generation of alarms Grout displacement Inclination 8

9 Example: Lifetime Wind farm comissioning 5 years End of warranty 20 years. End of planned lifetime Lifetime prolongation Start lifetime assessment early: - Monitoring system is in good state and working - No information about structure or measurement system is lost - Original structure designer is still available Load Cycle Matrix Accumulated Fatigue Damage Lifetime Prognosis 9

10 Example: Hidden Reserves Comparison of predicted fatigue damage profile (design) and actual fatigue damage of a TP (measured) for a period of 2 years of offshore operation. 10

11 Example: Deviations from Design Eigenfrequencies are used for design verification and damage detection 11

12 Example: Machine Behaviour Anomalies usually show in several parameters Pitch algorithm adapted 8 12

13 Example: Periodic Inspection Support Sensors can replace or supplement periodic inspection tasks Automatically measured data Data taken manually During periodic inspection 13

14 Example: Oberservation Method (EC7) Monitoring of permanent deformation within the soil Structure inclination is used as indirect parameter Data processing is used for compensation of statistical loads and environmental influences The use of a high quality inclinometer allows the monitoring of extremely small permanent deformations in the soil 0,03 Picture source: BSH Standard Design, mm 14

15 Lessons Learned: Clear Aims Necessary A focus on few aims lead to reduced sensor numbers and lower maintenance costs! Structure condition Structure integrity / safety Loadmonitoring (ULS, FLS, usability) Fullfill Authortity Requirements Reduce Periodical Inspection Effort Data for O&M / Asset Management Lifetime prolongation Hot Spot Monitoring Feedback for designer 15

16 Lessons Learned: Target Areas For maximum project benefit the focus of SHM needs to be on technical and contractual interfaces Design limits of structure Foundation-Tower is an important contractual interface Grouted connections are subject to ZiE procedure BSH requires foundation soil interaction to be monitored Application of Observation Method (EC7) Picture source: BSH Standard Design,

17 Lessons Learned: SHM Timeline Contractual interfaces define the SHM activities timeline Wind Farm Lifecycle Planning Installation O&M Wind farm commissioning End of warranty period Change of ownership Decommissioning BSH requirement, ZiE, Observation Method EC7 Lifetime Assessment Periodic Inspection suppport As built status, current status Hidden defects SHM Activities 17

18 Lessons Learned: Structural Integrity Life time prolongation is possible The structures do deviate from design 18

19 Lessons Learned: Soil-Structure Interaction With high accuracy inclinometers and compensation algorithms for statistical loads and environmental influences, it is possible to detect permanent foundation displacements of few mm. 0,03 Application: Observation Method (EC7) Fullfill BSH requirements 20mm Picture source: BSH Standard Design,

20 Lessons Learned: SHM and periodic Inspection Periodic inspection support is possible Under water inspection is expensive and dangerous. BSH allows flexible inspection concepts utilizing SHM systems. Proven concepts (e.g. risk based inspection from offshore oil and gas) can be adapted. This is still rare. Source: API RP 581,

21 Lessons Learned SHM needs to be part of Asset Management 21