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Condition Monitoring
for Wind Power Stations
Introduction of Condition Monitoring
In modern industrial enterprises the condition of manufacturing assets is a critical success factor to their business. An unforeseeable breakdown of one or more machines can cause logistical problems as well as losses of money, business partners or customers. Conditional monitoring is a
modern approach for maintenance of machines and allows through frequent or permanent recording and analyse of physical factors like vibrations or oil temperature to diagnose the actual condition of monitored machines. The main targets of conditional monitoring are e.g. early identification of
damages, safety of machines and people, efficiency of machines and avoidance of unforeseeable breakdowns [1]. The development of a modern Conditional Monitoring System (CMS) demands knowledge of mechatronic (mechanic, electrical and electronic engineering, measurement
technology and informatics) and advanced statistic (with growing importance).
Characteristics of Wind Power Stations
Wind Power Stations (WPS) are in most cases remote-controlled and often build in uninhabited areas. Inspections of plants are most only restricted possible. An unforeseeable breakdown of the power train can cause the operator the loose of earnings of several days or even weeks.
Conventional CMS are not suited for the use in WPS caused by the unsteady operating behaviour.
Research and Development
The research group of Measurement and Actuator Technology research and develop CMS for the special use in WPS. Our main targets are to develop and improve our CMS that offers reliable information about the condition of WPS and the reduction of the daily monitoring workload.
SPECTIVE
The developed System consists of hardware and Software for Powerful Envelope analysis and Calculation of Traces for Immediate Visualisation of Emergencies (SPECTIVE, analysing measurement data and viewing of results). The hardware primary consists of several acceleration sensors for
the measurement of the vibrations of the machine (standard configuration: eight), one sensor to measure the rotation speed, a programmable modular Controller (CompactRIO, National Instruments) for processing the data and an industrial PC for the storage of data and communication with the
server, see Figure 1. The software for data analysing is installed on a server. It offers state-of-the-art analysing features (e.g. Fast Fourier Transformation (FFT), Crest Factor, Kurtosis, RMS and Peak Level) and furthermore additional tools specially designed for WPS Condition Monitoring (e.g.
Frequency Lupe Spectrum, Cladding Curve Analyse, Cepstrum and Bearing Condition Indicator Value), see Figure 2. Figure 3 shows a spectrum of a WPS analysed with an industrial CMS. Figure 4 and 5 show the same data analysed with SPECTIVE. The pictures show that SPECTIVE is more
detailed and more precise than the state-of-the-art industrial one. The maximum amplitude at 602 Hz is more than four times higher than compared to the other one. The CMS SPECTIVE has been developed in cooperation with an industrial partner [2]. The hardware was installed in one of our
partners WPS and works reliable since two years without problems. The installed CMS software package is in daily use and helps to early identify potential defects on 46 WPS.
GetriebeStudio
Parallel to this analyse software the program GetriebeStudio was developed. It enables modelling of power trains and management of model data, see Figure 6. The program calculates important information e.g. meshing frequencies, which SPECTIVE use to assign frequency lines in a FFT to
specific components of the power train, see Figure 2.
SPECTIVExpert
The newest CMS-product is the program SPECTIVExpert, which is a Condition Monitoring Expert System (CMES). It uses multivariate statistics to determine the condition of each component of the power train based on the SPECTIVE output data. The condition of WPS is showed in
multiple views; see Figure 7 to 9.
Test stand
For future development and evaluation of our CMS a new test stand was build, see Figure 10. The key aspect of the test stand is a new developed gearbox, which enables switching between two possible configurations. The first one is a planet gear configuration, the second a spur gear one, see
Figure 11, 12 and 13. Both are commonly found in wind power trains. The gearbox design focus on the fast exchange of components (gear wheels and bearings see Figure 14). This enables to verify the efficiency of our CMS detecting on purpose damaged gearbox components.
SPECTIVE - Post analysis of known damage cases
1. Bearing damage: Figure 15 shows an endoscopy picture of a heavy damaged bearing. The used industrial CMS was not able to detect it. A post analysis of the stored data with SPECTIVE shows that the damage occurred three and a half years before the endoscopy (16. May 2013), see
Figure 16.
2. Broken tooth of a gear-wheel: Figure 17 shows an endoscopy picture of a broken tooth of a gear-wheel. The missing piece is one third of the length of the whole tooth. The used industrial CMS was again not able to detect the damage. A post analysis with SPECTIVE shows that the
damage occurred approximately five month before the endoscopy (15. May 2013), see Figure 18.
Publication
[1] Josef Kolerus, Johann Wassermann, German, „Zustandsüberwachung von Maschinen“, 4th edition, expertverlag
[2] Erwin Quintus, dissertation, German, 2014, „Entwicklung eines hochsensitiven Zustandsüberwachungssystems für Antriebsstrang von Windkraftanlagen“
Contact
Figure 1: Hardware
Figure 2: SPECTIVE - User Interface
Figure 6: GetriebeStudio - Model of a WPS power train
Figure 3: Spectrum - industrial provider
Figure 4: Spectrum - SPECTIVE
Figure 7: SPECTIVExpert - overview
Figure 8: SPECTIVExpert - detail view - table
Figure 5: Spectrum as shown in picture 3
and 4 with higher frequency
resolution – SPECTIVE
Figure 9: SPECTIVExpert - detail view - with geometry of
the analysed power train
Figure 10: Test stand
Figure 11: Cassettes used in spur gear configuration with
different bearings and with/without damaged components
Figure 12: Gear box - Spur gearbox configuration
Figure 13: Gear box - planet gearbox configuration
Figure 14: Gearbox components
Figure 15: Endoscopy -
Bearing damage
Figure 16: Post analysis with SPECTIVE - Trend of the amplitude of the overroll frequency
Figure 17: Endoscopy of a tooth
break on a gear-wheel
(recorded on 15.5.2013)
Figure 18: SPECTIVE post analysis - Trend of the amplitude of the third lower side band in the
frequency spectrum
Institute of Mechanics
and Mechatronics
Research group of Measurement
and Actuator Technology
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