telediagnose_g_05 (wind power plants)

7/31/2019 Telediagnose_g_05 (Wind Power Plants)

http://slidepdf.com/reader/full/telediagnoseg05-wind-power-plants 1/8

1

The condition monitoring magazine of PRÜFTECHNIK AG and Flender Service GmbH

No. 05 - September 2003

Condition Monitoring application:

WPP gears: broken teeth avoidedDr. Edwin Becker, Flender Service

The wind power industry has beenconfronted for some time with the so-called ‘revision clause’ of the insurancecompanies. They require that the com-plete drive train of the wind power plantis subjected to a general overhaul after40,000 operating hours or every 5 yearsat the latest – unless one of the condi-

tion monitoring systems recognized by the insurance company is installed. Thenfor example longer revision periods andclearly improved profitability of the wind power plants can be achieved.

A total of around 14,000 wind powerplants in Germany alone are affected by the revision clause.

The diagnosis of the condition of thegear trains of wind power plants (WPP)is a most difficult task. Gusts of wind cancause sudden severe load fluctuations which can significantly affect the vibra-tion behaviour. Diagnosis requires de-tailed information on the gear construc-tion, the excitation frequencies that canbe expected and a measurement tech-

nique that uses higher frequency andamplitude resolution. Also, an expert with sufficient diagnositic and serviceexperience must be available.

In fact, mobile condition monitoringtechnology can be used for WPP with afixed RPM, but it is better still to install asuitable online condition monitoringsystem right from the beginning. Thefollowing example illustrates how theuse of an unsuitable condition monitor-ing system impeded reliable condition

diagnosis and the affected drive traingear could be saved by Flender Service just before a tooth broke.

However, one thing after the other. A

wind power plant of medium power with a change-pole generator was retro-fitted with a standard condition moni-toring system of a third party by theoperating company.

In September 2002, an initial prelimi-

nary diagnosis report was provided by this supplier, whichled to a complaint tothe drive train manu-facturer in January 2003.

The diagnostic re-port was forwardedto the specialists of Flender ServiceGmbH for evaluation.This included threefrequency spectra

from April 2002 andtwo frequency spec-tra, i.e. a 10 second-long time wave formfrom August 2002.The visible pulses were very small and,unfortunately, no in-formation was givenon the measurementpoints and directionof measurement.

The cause of theexcitations was sus-pected by the Flenderspecialists to be

brinell pitmarks which particularly influ-ence the envelope spectra. Conditionanalysis using Flender diagnostic tech-nology was recommended. Mr Westhoff, After Sales Manager of Winergy AG, au-thorized Flender Service to carry out

mobile analysis of the gear condition

PRÜFTECHNIK and FLENDER SERVICE: Alliance in the wind

Condition monitoring now certifiedfor wind power plants

Continued on page 28

Special edition

In this issue:Condition monitoring now certifiedfor wind power plants

WPP gears: broken tooth avoided

WinTControl® goes offshore

No easy job: Aligning drive trains inWPPs

Measurement location selection anddiagnostics in WPPs

Basics on the measurement of fre-quency spectra

News & exhibition dates



2

The condition monitoring magazine

and, if necessary, to perform a selectivegear inspection using videoscopy.

The initial date agreed for March 2003for the on-site visit came about becauseof the lack of wind and the full calender

of the parties involved.Before the inspection cover of the gear

box was removed, measurements of thecurrent condition were carried out usinga DriveAnalysator®.

Strong acceleration excitations were visible in the envelope spectra, Cepstralanalyses and in the time signals. As aresult, an advanced local tooth damage was diagnosed on an intermediate shaftgear in the nacelle. Furthermore, theenvelope spectra showed pulses from

the output pinion gear that could beassumed to be standstill markings.Even after only a few glances two

damaged teeth and the standstill mark-ings could be seen during the gear in-spection. The corner of a tooth was eventhreatening to break off. This confirmedthe previous diagnosis made with theDriveAnalysator®.

The drive train was immediately brought to a halt in agreement with theplant manufacturer because the break-age of the corner of a tooth can lead to

the immediate actual total loss of thegear.

Unfortunately, the online system in-stalled provided no information as to thetrend of the damage and old data wereno longer available.

The gear unit was dismantled a week later by the plant manufacturer, and sentto Winergy AG in Voerde for furthertesting and repair. The diagnosis madein the nacelle was confirmed.

The repair expense could be kept

small due to the timely shutdown. Thecause of damage was not clearly identifi-able. Experience indicates that it ismostly short-time overloads duringchangeover, braking or during emergen-cy stops which lead to such tooth dam-age.

Display of the tooth damage (see photoon right) in the time signal, in the Cep-strum and in the envelope spectrum.

As the leading insurance company,‘Allianz’ has created a requirements in-dex for Condition Monitoring systemson wind power plants.

In order to be able to fulfill theserequirements, PRÜFTECHNIK andFlender service have carried out exten-sive development work over recent

8 Continued from page 1:months to adapt acceleration transduc-ers as well as the hardware and firm- ware of WinTControl® and OMNI-TREND® to the special demands of the variable speed wind power plants. Thedevelopment effort was concluded withcertification by the Allianz Zentrum für

Technik (Allianz technology center). I



3


Roland Schühle, PRÜFTECHNIK

Wind energy plants on land are much

simpler to service than plants which areinstalled off the coast in the sea (off-shore). The frequently adverse weatherconditions in the North sea and theBaltic sea can impede or prevent theservice team from travelling to the windpower plants to perform the necessary service work. However, if the installa-tions have already come to a standstill asa result of defective machine parts, then,in addition to the costs of the repair, thestandstill costs are also reflected in theprofitability calculation. Therefore, inthe case of an offshore installation, it iscrucial to detect any defects at the earli-est initial stage and to estimate theremaining running time of the machinepart. Consequently, service visits can beplanned to be cost effective - even takingthe possible ‘weather window’ into ac-count. To reach this objective, new pro-cedures which can be used to estimatethe service life of the system and tooptimize its availability must be devel-oped for the diagnosis of damage and

wear.

For this reason,

PRÜFTECHNIK Con-dition Monitoring gottogether with othersystem manufactur-ers, operators and in-stitutes to form a re-search group withinthe framework of theCONMOW* programpromoted by the ECand has fitted a windpower plant sta-tioned on land withmeasurement tech-nology. The system inZoetermeer (NL) operated by SIEMENScomplies for the most part with theplanned offshore systems and is thesystem equipped with the most exten-sive monitoring technology in the worldat the moment.

The 1.5 MW wind turbine from Gener-al Electric works with a variable RPMand, thus, presents a new challenge tothe diagnositic procedures of the online

condition monitoring systems (WinT-Control®) that areemployed. Two WinT-Control® systems areinstalled in the na-celle. The first systemcontinuously records30 characteristic val-ues and operating pa-rameters at a sam-pling rate of 30 Hz.The second system

records dynamic sig-nals at sampling ratesof up to 150 kHz which are analyzedusing new diagnosis-tic algorithms suit-able for dynamicspeed changes. Thedata from both sys-tems are corellated inorder to identify op-erating and damagepatterns.

The recorded andmonitored measure-ment variables are

listed on page 4.The acceleration transducers were

specially developed by PRÜFTECHNIK for use on wind turbines. They exhibit alinear characteristic in the frequency range of 0.1 Hz to 10 kHz. The measure-ment signal in the frequency range of 0.1 Hz to 10 Hz is also available with asensitivity of 1000 mV/g, so the smallestsignal amplitude in the low frequency

range can be seen at a high resolution.In the second WinTControl® system,

the condition monitoring and the diag-nostics are divided into three levels. Atlevel 1, the monitoring is based on mon-itoring the limits of broadband charac-teristic vibration values, at level 2 onmonitoring the limits of diagnostic char-acteristic values (frequency selective)and, at level 3, on the diagnosis of changes in condition (condition diagno-sis) on the basis of ‘ordertracked’ ampli-

tude spectra, envelope spectra and Cep-stra, as well as time analyses and specialprocedures.

The system calculates vibration levelsfrom broadband vibration measure-ments on the drive train. The gear meshfrequencies of individual gear stages, therolling bearing frequencies of the mainbearing and the generator bearings arecalculated and monitored as diagnosticcharacteristic values (level 2). The re-cording of level 3 measurement data isprogrammed so that measurements are

carried out under comparable condi-tions and the diagnoses are carried outautomatically and independently as

*CONMOW = Condition Monitoring of Offshore Wind Turbines

PRÜFTECHNIK takes over the role of technology leader

WinTControl® goes offshore



4


4

Glossary of technicaltermsDid you know?

Telephone modemTelephone modems are used for the transfer ofdata over an analog telephone line. They canbe connected in parallel to a voice telephonevia the same telephone line, whereby only oneof the two devices can use the line at the sametime. The number of ring tones before themodem answers can be selected. Telephonemodems are connected directly to the RS232interface.

ISDN (Integrated Services Digital Network)

ISDN modems divide the copper wires of aconventional telephone into two digital trans-mission channels. The second transmissionchannel can be used for either a voice tele-phone or for doubling the transmission rate.Most exisiting telephone connections can beconverted to ISDN operation. ISDN modems areconnected directly to the RS232 interface.

ADSL (Asymmetric Digital Subscriber Line)ADSL modems divide the copper wires of aconventional telephone into three digitaltransmission channels. Two channels are usedfor data exchange with the Internet and onechannel is used for telephoning. The Internetconnection has a slower “upstream” channelfor dealing with requests to servers and a“downstream” channel for receiving data fromthe Internet. ADSL is marketed in Germany asTDSL. ADSL modems are connected directly tothe Ethernet interface.

WLAN (Wireless Local Area Network)WLAN is a radio network technology for datatransmission. The transmission stations must beconnected by line of sight. Basic modules withintegrated antennae bridge distances of up to400 m. Distances of several kilometers arepossible with additional antennas. Obstaclescan also be bridged by the installation of relaystations. As well as point-to-point connections,networks can be realized with WLAN. No costsarise from the data transmission and there areno registration formalities. WLAN is ideallysuited to bridge the last mile of a telephone

line and an online system.

GSM(Global System for Mobile Communicatons)GSM is today’s basic technology for mobiletelephones and for mobile data transmission.GSM modems are connected directly to theRS232 interface.

HSCSD (High Speed Circuit Switched Data)HSCSD modems increase the maximum amountof data to be transmitted per GSM channel. Inorder to reach a higher data transfer rate,HSCSD is bundled with up to four radio chan-nels. Frequently this system is also known asHSMD (High Speed Mobile Data). HSCSD mo-dems are directly connected to the RS232 inter-face.

soon as a characteristic value is exceeded. The

dependency of the vi-brations on the prevail-ing operating conditionsis taken into account onthe basis of comparativemeasurements.

The current measure-ment values are com-pared with warning andalarm limits and, if a violation occurs, a warn-ing message is automati-cally sent by eMail orSMS to selected persons.In addition, the special-ist can establish a con-nection to the system,analyze previous trendsand/or perform specialanalyses.

Both WinTControl®

systems are connected with one another in thenacelle via Ethernet andconnected to the Internet via ADSL mo-

dem. As a result, the data can be access-ed by all project participants at any timeusing an Internet browser. This providesoperators, manufacturers and also insur-ers with the opportunity to simply gainan overview of the running and operat-ing behavior of the wind power plant.

This installation puts PRÜFTECHNIK Condition Monitoring at the forefront toalso develop important basics for condi-tion diagnosis and availability optimiza-tion of offshore wind power plants and

to offer reliable online Condition Moni-toring systems. Because, with respect tothe revision clauses of the insurer thathave recently come into effect (see arti-cle page 1), many operators must nowequip their offshore systems with themost modern monitoring technology inorder to obtain insurance protection. I

Sensor components of the test systemWinTControl® no. 130 channels, 30 Hz sampling rate, continuous

•Temperature & currents of pitch motors• Actual value & nominal angular setting of

the rotor blades•Blade moments in the X & Y direction•Rotor RPM• Azimuth angle•Nacelle vibration in the X & Y direction•Incorrect yaw angle•Electrical performance•Mechanical performance•Wind speed•Gear unit temperature• Air temperature• Air pressure

WinTControl® no. 217 channels, sampling rate max. 150 kHz,triggered

• Vibration at the main bearing• Vibration at the intermediate shafts• Vibration at the planetary stage• Vibration at the generator•RPM•Phase position•Generator performance

•Wind speed•Main bearing temperature•Gear unit temperature•Generator temperature



5


The use of laser optical systems for thealignment of shafts in coupled machines

and machine trains in industry has be-come state-of the-art over the last fewyears. They are also already in use in theshipping industry.

In applications with a concrete foun-dation –with few exceptions– it can always be assumed that the alignmentcondition will not change or changes very little. There are applications where

thermal expansion must also be consid-ered and alignment guidelines, eitheraccording to manufacturer data or as aresult of experience and measurements,must also be taken into account. Inaddition, standard alignment tolerances

are available for different RPMs.In the case of ships, there are other

aspects to consider and the expression:“alignment only in the early morningsun!” holds true. The background to thisis the warming up of the hull and the

elastic foundation of the main dieselengine. This results in relatively large

displacements so that highly flexiblecouplings or relatively long shafts haveto be used.

The displacements are in the millime-ter range. Alignment target offsets areprovided by diesel and gear manufactur-ers so that alignment can be carried outfor operation ‘at the zero position’. As aresult, the working range of the coupling

is fully exploited.The alignment of the gear and genera-

tor of a WPP presents a comparablesituation whereby there are also otheradditional problems to solve and diffi-cult boundary conditions that have to be

taken into account:• Mounting the sensor components is

difficult because the space is restrict-ed by the brake.

• In cases of more severe misalignment,the laser beam can leave the mea-

No easy job:Aligning drive trains in wind power plants

surement area of the alignment sys-tem. With InfiniRange® severe mis-

alignments and large distances arenot a problem.

• Wind power must be used to rotatethe shaft. This makes it difficult tomove to defined 90° measurementlocations. The patented EZ-sweep®

mode measurement records data while the shaft is rotating and just 60°of rotation is possible.

Our experience – dependent on the dif-ferent types of WPP:• The deformation of the nacelle plays a

role in the alignment. Any change inthe wind direction and wind strengthcan influence the alignment results.

• Depending on the operating mode,the generator and gear may be atdifferent positions to one anotherduring operation.

• The generator may sink over time dueto aging of the vibration damper sothat manufacturer data are requiredfor corrections.

With a little experience, it is quitepossible to carry out alignment of thegenerator and gear while they are at astandstill. However, the question thenarises as to whether this is also optimumfor longer time periods or for differentoperating states. The optimum condition

for alignment is obtained when the min-imum reset forces of the coupling arereached during the normal operatingstate. Alignment data can be obtainedeither from the manufacturer of theWPP or as the result of measurements.

WinTControl® allows the optionalconnection of sensor components for thecontinuous monitoring of the alignmentcondition (PERMALIGN®). This makes itpossible to record the alignment condi-tion depending on the operating state

and the vibration behavior of the WPP.These measurements can be used toprovide alignment target offsets for opti-mization of the shaft alignment. I

RPM Tolerance [mm]Parallel displacement Acceptable Excellent

1500 0.09 0.06

3000 0.06 0.03

Angular displacement(angular gap) 3000 0.06 0.03Gap width referred to

coupling diameter 100 mm 1500 0.07 0.05

Recommended alignment tolerances

Application

Johann Lösl, Ole Holstein, PRÜFTECHNIK



6


6

scher Lloyd. The figure shown aboveillustrates how WinTControl® is used.The diagnostic algorithms used also ap-pear in the picture. The rolling bearingsof generators, gears and main bearings,the toothing of the planetary stage(s)and helical gear stage(s) and the gondo-la, tower and special machine vibrationsare monitored.

In the case of variable speed systems,

order spectra are used as standard. Moredetails can be obtained under www.wintcontrol.com.I

Measurement locations and diagnostics in WPPsCondition Monitoring basics

Classically, the choice of measure-

ment locations assumes that the vibra-tion conditions are measured at bearingpositions in the main directions, verti-cal, horizontal and axial. This procedureis required by some standards. However,in the wind power branch, this wouldmean that at least 18 acceleration trans-ducers would have to be mounted in thecase of simple gear trains with maintransmission gears. For cost reasons,WPP operators are not prepared to in-stall so many sensors and measurement

locations.The mounting of the transducer at thecorrect measurement point is essentialfor the reliability of the diagnosis. Thisis illustrated by some FEM calculationresults (Finite Element Method) for atypical gear unit in a wind power plantshown in the three figures that appearbelow. Depending on the transmissionproperties of the housing, discrete exci-tation frequencies at different measure-ment points vary distinctly. The redrange corresponds to the housing mea-

surement points with the highest inten-sity (vibration speed in mm/s). There-fore, the choice of the correct measure-ment locations always represents a tech-nical compromise and may require agreat deal of experience.

For the selection of measurement lo-cations, Flender Service uses their expe-rience in FEM calculations, test benchmeasurements and countless mobilemeasurement deployments on windpower plants.

Meanwhile, the minimum number of sensors was specified by the Allianzinsurance company and by Germani-

Dr. Edwin Becker, Flender Service

Fig.: Minimum number of sensors anddiagnositic algorithms used

Fig.: FEM calculation results which displaydifferent housing structure vibrations atthree sample frequencies

• Amplitude spectra, envelope spectra withvariable parameterization and Cepstren witha higher resolution

• Time wave forms / resonance frequencies• Characteristic diagnostic values (v, a, env, cep)• Characteristic vibration values (v, a, env, cep)

• Amplitude spectra• Intrinsic frequencies• Characteristic diagnositic

values• Vibration characteristic

values



7


Part 5: Calculating the excita-

tion frequencies of planetarymeshingLike all elements of a drive train, gear

units also have a tendency to vibrate. Vibrations excited by toothing arecaused by changes to the load parame-ters on the teeth over the gear meshingdistance. These periodical, strongly load-dependent and speed dependent vibration excitations also occur in per-fect gear units. A comparison of thefrequency excitations to be expectedduring an optimum run with the spectrameasured on running gears allows thesafe evaluation of the gear mesh condi-tion.

While the calculation of excitation fre-quencies in helical gears from gear- andspeed information is still relatively sim-ple, the calculation of kinematic fre-quency excitations of complex planetary

gears proves to be considerably more

time consuming. The adjacent info boxlists the underlying calculation formulasfor planetary gears with a fixed internalgear ring. Planetary gear units can alsobe operated in such a way that theplanet carrier stands still, the sun gearstands still or even all gears turn (3-shaftoperation). The current trend in geartrains is for two planetary stages to bearranged one after the other with a fixedinternal gear.

According to type and prominence,toothing faults can cause an amplitude

modulation and/or phase modulation of the gear mesh frequency. Usually, thisleads to an increase of the higher har-

Condition Monitoring basics

monics of the gear meshing in the fre-quency spectrum and pass frequenciesand also to sidebands at a multiple of the damage frequency. In the diagnosisof planetary damage, the situation isaggravated by the fact that the specialkinematics also causes a modulation ef-fect even when the teeth are not dam-aged because the intermeshing planetscyclically approach the accelerationtransducer fixed on the gear unit andmove away again. Also, the pass fre-

quencies are mostly very low frequen-cies which requires correspondingly long measurement times and suitablefrequency analysis techniques.

The resulting damage can be particu-larly well detected using envelope analy-sis although permanent online analysis with trend monitoring is recommendedin order to record changes in conditionthat are already slight. I

Dr. Jörg Deckers, Flender Service

Fig.: Vibration velocity spectrumof a planetary transmission withmany harmonics from internalgear damage

Fig. Typical drive train gear

PreviewOur next issue focuses on conveyor

technology:

CM applications: Problem analysis ona bucket wheel excavator in the Ama-zon

Technology: Experience with the ap-plication of wireless LAN in the teledi-agnosis of conveyor systems.

Application: Condition monitoring of Polish giant strip mining equipmentusing modern Internet technology.

Counting teeth, RPM(example: stationary internalgear)

Sun gear: z1; nS [min-1

]Planetary gears: z2; n

P[min-1]

Internal gear: z3;Planetary carrier: nT [min-1]Number of planets: k Translation: i=z1 /(z1+z3)

Excitation frequencies

Rotational frequencies

Sun gear

Planetary gears

Carrier

Gear meshing frequency

Overrun frequencies

Sun gear

Planetary gears

Internal gear

Sun gearPlanetarycarrier

Planet

Basic rules for the measurement of frequency spectra



8


Imprint

PRÜFTECHNIK AGPostfach 12 6385730 Ismaningwww.pruftechnik.comTel: 089-99616-0Fax: 089-99616-200eMail: [email protected]

Flender Service GmbHSüdstrasse 11144623 Hernewww.flender-service.comTel: 02323-940-220Fax: 02323-940-229e-Mail: [email protected]

Dates

News

PRÜFTECHNIK AG and Flender Service:Visit us at the following interna-tional trade shows and exhibi-tions:

Windmesse Husum23. - 27. 09. 2003, Hall 2, Stand B230

7th. AZT expert day 2003

10. - 11. 11. 2003 in Ismaning

The latest dates are given on our Inter-net website.

Mobile DriveAnalysator®

now for variable RPM WPPOur new DriveAnalysator® has mas-

tered its first application for RPM-vari-able WPPs in Norway. It is especially suitable for troubleshooting or for WPP with sufficient wind and an instant on-site evaluation by diagnostic specialists.The DriveAnalysator® is configured as a6-channel analyzer and determines or-der spectra. I

Analyzing oil qualityFlender Service is offering a new ser-

vice –the analysis of oil quality. Especial-ly the addition of EP and AW (Extreme-Pressure, A ntiWear) additives has beentested in the case of high performancegear oils. This uses a new innovativemeasurement method which will shortly be released onto the market. Throughthe analysis of the ‘smell’ alone, the typeof oil which is used can be recognized,to indicate whether an inadmissible mix-ture is present or whether further addi-tion is still OK. On the basis of ouranalysis, the operator of a WPP must beadvised to dispose of his replacement

oil, as a separation of the lubricant inthe tank took place – probably throughthe effects of the cold.Interested? Then contact us today!I

Major orderfor Flender Serviceand PRÜFTECHNIK

Nordex AG decided on WinTControl®

after extensive tests and system compar-isons and called for the first onlinesystem. Crucial for this decision was the

special serviceknow-how andthe possibilitiesof WinTCon-trol®, also moni-toring of RPM-

variable drive trains. An outline agree-ment was made between Flender Serviceand PRÜFTECHNIK Condition Monitor-ing regarding the delivery of 300 WinT-Control® systems ready for installation.I

smartSCANNER™ –

the practical

3-in-1 solution

for vibration analysis

for balancing and

for shaft alignment

Now all togetherin one handy device!

WinTControl®

goes OMNITREND®

The WinTControl® System is fully

compatible with the OMNITREND

®

PCsoftware: Besides the display and storingof the measurement data and statusinformation in an Access or Oracle data-base, OMNITREND® also enables theprogramming of WinTControl® system.However, a permanent connection withOMNITREND® is not required, becauseWinTControl® as its own intelligent sys-tem buffers the results as well as thealarm evaluation and can carry out allresulting actions independently. I

New ‘wind’ sensorwith a linear characteristic

above 0.1 HzPRÜFTECHNIK AG has

developed a new acceler-ation transducer especial-ly for use in wind powerplants, which has a linearcharacteristic in the fre-quency range of 0.1 Hz to10 kHz. This providesmeasurement signals for

rotor blade diagnosis which, for example, provide comparableamplitudes over the complete RPMrange and can be processed with a singlesensor type. Also, all demands of theinsurer (Allianz) can be fulfilled using asingle type of sensor.I

The frequency pattern of the new ‘wind’transducer is linear above 0.1 Hz

telediagnose_g_05 (wind power plants)

Documents