a typical wind turbine setup for windconwebcon.skfcmc.com/application notes/a typical wind turbine...

Created by: Theo Du Plessis

2011-09-28

A Typical SKF Wind Turbine Setup for WindCon


2011-09-28

General......................................................................................................................... 2

Templates................................................................................................................. 2

The standards and guidelines of a WindCon setup...................................................... 3

Language.................................................................................................................. 3

Measurement naming convention............................................................................ 3

Turbine and other hierarchy names ......................................................................... 3

User accounts ........................................................................................................... 4

Concept of setup, diagnoses and measurement points............................................. 4

Measurement Gating or Classes .............................................................................. 5

The measurement setup steps and structure (if you do not have a Template or need

to alter/improve a Template).................................................................................... 6

Como tips........................................................................................................... 10

Main Bearing measurement setup.......................................................................... 13

Gearbox Measurement setup ................................................................................. 17

Generator measurements........................................................................................ 21

Oil particle measurements ..................................................................................... 24

Setting up the Asset Maintenance.......................................................................... 26

Connecting and interfacing to SKF Lubrication systems ...................................... 28

Blade monitoring system measurements ............................................................... 29

Additional Measurements ...................................................................................... 29

Setting up Workspaces for integration to WebCon ............................................... 29

General good to know information:....................................................................... 31

Enveloping ......................................................................................................... 31


Last Revised: 9/22/2011 1:46:00 PM 2 (32)

General In SKF we are trying to build on knowledge. This knowledge starts with a basic

template of the setup for monitoring a wind turbine. We try for this reason to monitor

all the turbines in the world in the same manner, and according to what has become

the SKF standard for wind turbine condition monitoring. This standard allows

colleagues in SKF to help one another even across borders, cultures and languages.

This does however require us all to follow the same rules and understanding of

condition monitoring to take full advantage of such a standard. I will describe below

these standards we would like you to follow so that when needed, and if needed, we

can all help one another, understand what we have done, improve on what we have

done and harness the full potential of what we have been doing because we followed

a standard. It is easier and more likely to improve one standard than to try and

improve several ad hoc setups!

Templates

As more and more SKF collogues build more and more “good” setups, we generate

templates out of them. Templates are then again freely distributed between all wind

como people in SKF. This can only work if we all help and share improvements on

the templates on a continuous basis. Templates are powerful and help SKF to make

statistical and other advance research technology on the data of templates because

they conform to a certain standard.

Templates also contain a lot of knowledge in the form of automated Diagnoses.

These diagnoses are what make everybody’s life easy and that help every new person

to even to a good job. This is core to SKF WindCon and these diagnoses must

receive your fullest attention for both making sure they are correct for you current

application, and improving them. All improvements to templates can be sent to

[email protected]. Please remember, we need to put more knowledge into the

system and automate more diagnoses. This needs your help and must be done by

improving and adding effective diagnoses to the system.


Last Revised: 9/22/2011 1:46:00 PM 3 (32)

The standards and guidelines of a WindCon setup

Language

Because SKF consist out of many cultures and languages, it would be impossible to

help one another if we all did it in a different language. For this reason, the standard

setup requires that everything is done as far as possible, in the official SKF language,

English. This does not mean that English is a must and certainly not for end

customers, but for all other purposes, try to use a “type of English” as far as possible.

Use for example short words for measurement names and short “bullet type” list for

entering notes.

Measurement naming convention

1. Use as far as possible very short names for everything and in English. This

also lowers the risk of running out of space for names in the software.

Examples are:

• Main shaft bearing acceleration– Main Bearing Acc or MB Acc (if there

are two main bearing then MB1 and MB2)

• Main bearing axial acceleration - MB Axial Acc

• Main shaft bearing Envelope 3 measurement – MB Env3

• Gearbox Planet stage low speed shaft/side – GB LSS Acc

• Gearbox planet stage enveloper 3 – GB Planet Stage Env3 (if there are

two like on V90’s, then GB Planet Stage 1/2 )

• Gearbox axial acceleration low speed side – GB LSS Axial Acc

• Gearbox intermediate shaft/parallel shaft acceleration – GB IMS Acc

• Gearbox high speed shaft envelope 3 – GB HSS Env3

• Generator drive end bearing – Gen DE

• Generator non drive end bearing – Gen NDE

2. For a wind turbine setup, we start with the acceleration measurement first,

followed by its Envelope measurement(s).

Turbine and other hierarchy names

Try also here to use the shortest possible name. Use a number convention as far as

possible for example: your customer has 30x Vestas V66 turbines spread over two

parks called “NakBull” and “Trak”. Example setup of this:


Last Revised: 9/22/2011 1:46:00 PM 4 (32)

• NakBull

o V66-1 (better would be T1)

o V66-2 (…T2)

o V66-3 (…T3)

o ….

• Trak

o V66-1 (better would be T1)

o V66-2 (…T2)

o V66-3 (…T3)

o ….

This can easily work in Observer because Observer always uses the full hierarchy

path to reconstruct the graphs title. So you will always have a unique path to each

graph and measurement. A path name in this case would look like this: Trak\V66-

1\Spectra or NakBull\V66-28\Time Wave, or the better preference: Trak\T1\Spectra.

User accounts

Each user that needs access to the system needs to have his own account. This does

not matter if he is working for SKF or not. Do not share accounts because this is bad

practice. Having an account for every user setup also means that you have actively

though about this persons roll in this whole program and it help everybody to

understand what has happened in the system and why. Actions performed in the

system are tracked against each users account. Alarm acknowledgment is also logged

on your account.

Concept of setup, diagnoses and measurement points

Use your measurement for what and where they were place/installed. By this I mean

do not use the generator sensors to sample data you think you can use to detect

gearbox failures with. Maybe possible on some designs of turbines, but still, there are

several probes on the gearbox that can better detect this. A few bullet rules to try and

remember:

• Look for/do bearing diagnoses only on Envelope measurements

• Look for/do imbalance and gear failure diagnoses mainly on normal vibration

measurements

• Do not attach all diagnoses to all measurements, this is a waist of your own

time.

• Setup measurement point to not include all frequency ranges, but to focus on

frequencies that might be close to where the probe is mounted.

• Keep in mind that even though a wind turbine is a low speed machine, we in

SKF use a setup that will take 90% of the data when the turbine is at a high

speed.


Last Revised: 9/22/2011 1:46:00 PM 5 (32)

• The higher the speed is at which you can take the data, the higher the load is

(probably), the easier it is to separate individual frequencies from one another

like gear mesh and side bands.

• Gears and bearing do not fail in one day….they take weeks…months.

• High resolution measurements needs more time…and more time on a wind

turbine means more speed changes, which again means more smearing in the

FFT. Be careful and use small “delta/speed variation”. One good

measurement per week is better that 4 bad measurements/day.

Measurement Gating or Classes

(See page 7 also further down in the document how to determine these classes)

We use as a standard at least two (2) measurement classes for wind turbines.

Exception: If your turbine spends enough time at full load, meaning there is

always enough wind for it to get to full power at least 4x a week, then one high

class only will do. Four good FFT’s/Time waves at full load per week is the

minimum for good analyses on a wind turbine.

Each class uses speed and load gating to control when data must be taken. Speed and

Load must therefore also be a simultaneous measurement on/for all measurements.

This is very important, not only to get data at the right moment in time, but to get

repetitive measurements, stable measurement that can be effectively alarmed on and

be effectively used for advance and automated diagnoses. Load and speed at the

moment of measurement is of the utmost importance to interpret the data.

Only after you have selected the simultaneous measurements are they available to be

used for gating.

A typical High Class setup:

A typical Low Class setup

This forces you to have actually a duplicate setup of all the measurements. You will

have a setup with all the measurements for the High Class and a copy of all these

measurements for the Low Class (this is also a simple way to practically do it, copy-


Last Revised: 9/22/2011 1:46:00 PM 6 (32)

and-past in Observer hierarchy). This will also allow you to get measurement even if

the turbine doesn’t get to full load for a long time (data will be gather for the Lower

Class probably). Take precaution, because some setting might have to be fine turned

in each class because you might need higher resolution in the Lower Class to

separate the harmonics and sidebands in the FFT. Study the speed vs. load graph of

you turbine to fine tune these settings. See page 10, Como Tips for more on this.

The measurement setup steps and structure (if you do not have a Template or

need to alter/improve a Template)

1. Start by setting up the speed measurement first (it will also be then the first

measurement on your machine in the hierarchy)

Remember:

“….The Tacho installation for WindCon can be tricky at times and is a tedious

problem to get fixed because you have to stop and re-climb the turbine again to set the tacho to a new position in the hope of getting it working correctly. A trick here would be to by default always t-off the tacho to one of the free analogue channels also. So, you install the tacho the normal way onto tacho1 or 2, and then t-off the signal also to (for example) channel 14 (set to not power the signal). Now when back at the office you can always take a look at the time signal on channel 14 (the tacho pulse) to see why the WindCon might not trigger correct/have the correct and stable speed…..”

If this was done, you can check your tacho signal’s time wave on the T-off

channel to verify it working correctly. This is temporary measurement and

can be deleted or disabled once the tacho has been verified.


Last Revised: 9/22/2011 1:46:00 PM 7 (32)

2. Setup the load or derived load measurement next

To setup a derived load measurement, meaning that the system must derive

load from another measurement like the Roglowski Coil load probe (sold

together with WindCon packages as an option), you must first setup the

normal measurement from which the load must be derived. In this case, load

will be derived by the system from an FFT done on the Roglowski Coil

channel. Load is based in this case on summing the first 3 harmonics of the

current frequency which is either 50 or 60 Hz and there respective 3

harmonics (see the installation manual also for details).

Setup the initial measurement as follow (called in this example: Roglowski

Coil):


Last Revised: 9/22/2011 1:46:00 PM 8 (32)


Last Revised: 9/22/2011 1:46:00 PM 9 (32)

Now you can setup the Load that will be derived from this measurement:

Setup an IMx Derive Measurement called Load.

Setup under “parameters” the following by using the “Add” button:

Select the original measurement on the Roglowski Coil the 50Hz band that

you’ve setup in the previous step. Load will now be derived from this band.


Last Revised: 9/22/2011 1:46:00 PM 10 (32)

3. Next you should setup the complete Machine Parts. Make sure that all

bearing and gear detail are correct and that the parts are complete. Make sure

your planet stage is setup correct (Observer 8.3 and onwards only needs one

planet stage to do the calculation for the machine parts, and not two linked

like in this example. The same goes for couplings).

Como tips

• With the speed and load you can already do some condition monitoring. By

plotting speed vs. load (scattered plot), you can analyze “character” of the

turbine. This plot will help you to determine the classes needed for

measurements. It will show where the turbine likes to operate and where it

spends most of its time (different for each turbine because of location and

micro climate). Example plot of speed vs. Load


Last Revised: 9/22/2011 1:46:00 PM 11 (32)

In this example you can see the two usable classes quite easy. There is a class

with speed range 1550 – 1700 rpm and with corresponding load between

2000 – 2600 MW (high class), and a class with speed range 1200 – 1400 rpm

with load between 400 – 700 KW range (low class). Ideal classes are classes

where the speed has very little to no change and only small load changes. Try

to make your speed spread/range as small as possible with 30 -120 rpm delta

only (for high speed shaft tachos).

• When wind speed is also monitored, you can also do a speed vs. wind speed

scattered plot (like above). In this case, you can then monitor how the turbine

controller is controlling the turbine. Changes in this behavior will point to

calibration errors/problems in or with the wind speed meter, inaccurate baled

pitching (when this graph is compared to those of similar turbines in the same

park) and jaw problems (inaccurate or not calibrated wind direction meters).

4. We only store FFT and Time Wave data.

This saves space in the database. Phase data is not needed because we do not

have triggered measurement on a wind turbine and we also have no

displacement sensors. If balancing is to be performed (in special case studies

or conditions or in other applications), you need to save the phase data also

for the points that will be used for balancing. All measurements must then be

triggered by the tacho for phase calculations.

5. Trend data are stored to the database every 30 or 60 minutes and FFT/Time

wave data 1 or 2 times per day (when alarm are triggered, the system will

automatically store more data)


Last Revised: 9/22/2011 1:46:00 PM 12 (32)

6. We setup one or two “Gear Inspector” measurement point on the

machines/gearbox. See Gearbox Measurement Setup topic for detail.

7. We use 50% averaging and Acc -RMS on the trends. This smoothes the trend

a bit and you can also use the “spike filter” to remove spikes if your

installation is troubled by this.

8. Set your overall to start at the 2nd

line in the FFT and to end at the last line in

the FFT (max frequency). This makes your trends easier to interpret and to

analyze because they are from the same data you will see in the FFT. This

limits confusion and is a good standard.

9. Try to avoid attaching all diagnoses to all measurements. Look at the

calculation that will be used by the diagnoses, and check if the frequencies

that will be used can actually be seen by yourself in a sample FFT. If not,

reconsider the effectiveness and possible adaptation of your approach.

10. If you have a lot of measurements, multiple sub components, external

systems and data all in one big explorer view, consider to split them up by

using “Sub Machines” under your main machine to group them for example:

When following this method, do still follow the logic of labeling your sub

machines groups by starting from the blades and moving down to the

generator.


Last Revised: 9/22/2011 1:46:00 PM 13 (32)

Main Bearing measurement setup

• Setup main bearing measurements to focus only on the vibration of the main

shaft, the main bearing(s) and the blades.

• Typical setup is 50Hz, 1600 lines.

• Make sure your trended alarm bands don’t start at 0 cpm, but at the 2nd

or 3rd

line of the FFT (in this case it would be 0.3 cpm as a minimum, but because

this measurement will only be taken in one of two speed/load classes, the

lowest frequency the turbine will generate for monitoring is probably around

0.1Hz = 6cpm).

• Diagnoses that can be performed on this measurement:

• If the measurement is axial, you can setup a diagnose for the force on blades

(3x main shaft speed if you have 3 blades) and if it is radial, you could setup

a diagnose for the imbalance vector of the blades/main shaft. Examples:


Last Revised: 9/22/2011 1:46:00 PM 14 (32)

Imbalanced caused by snow on the blades after a long turbine stop

Diagnoses for imbalance (detected rotor imbalance on one blade. Blades was rebalanced by

OEM)

• We also setup here what we call an “open” measurement. Open

measurements have no speed nor load classes coupled to them, and can hence

take data at any speed or load. Precaution must be taken to prevent smearing

in the FFT, so a small Delta variation of the speed is still needed.


Last Revised: 9/22/2011 1:46:00 PM 15 (32)

Measurements can be taken at 1/day intervals (for both FFT and trends), and

over time, you can use the typology plot in Observer to find and track

resonance frequencies. Because measurements have been taken all at

different speeds, the only fixed frequencies in the typology plot will be those

belonging to structural fixed resonance frequencies. Use 50Hz, 800 lines and

a delta of 60 cpm.

• Typology example (resonances at ± 21 Hz, 25 Hz, 33 Hz…):

• Typical final main bearing setup example:

• Alarm levels: because this is on the low speed side of the turbine and we have

very strong and ridged bearing holding it all down, do not expect to see high

vibration. For Env measurement you can go with 0.02gE for warning and

0.03 alarm. For normal vibration, it is hard to say…start with 0.1g warning

after evaluating the vibration levels you measured.

• Como Tip This measurement can easily, in most cases on most turbine models, also

pickup gear failures such as crown gear teeth problems from the first

planetary stage. Because the alarms on this measurement are very low, this

could easily cause high measurements on this point. This is something you


Last Revised: 9/22/2011 1:46:00 PM 16 (32)

should recognize when you come across it. This is also why we try to setup

this point to only focus on vibration that can come from the main bearing and

shaft. If you make the sampling frequency too high, you will not have any

good monitoring on the main shaft because the alarms levels will be useless.


Last Revised: 9/22/2011 1:46:00 PM 17 (32)

Gearbox Measurement setup

• Same rules still applies for these measurements. Try to use the sensor/probe

for where the they are mounted and set the sampling frequencies and

resolution carefully (for example, use the probes near the planet to look for

planet problems). Keep in mind that a 1 Hz change on the low speed side of a

wind turbine gearbox can easily mean a 100 Hz change on the high speed

side (ratio 1:100 is common on these gearboxes)

• Pick 3 probes, spread over the gearbox and also setup on them Time

Waveform Analysis measurements (Crest, True P-P and Kurtosis). For probes

on the low speed side of the gearbox use a frequency of at least 500 Hz, and

for the high speed side use > 1 KHz (always on the gearbox as high as

possible sampling frequency. Make sure you cover at least 1 cycle of the

components in question).

Setup these components to be tracked:

Alarm levels is very hard to standardizes on here and you must set them

yourself after some stable data has been acquired. Set the warning to 2x the

average and the alarm to 3x the average.

• Como Tip

This type of measurement tracks shape changes in the raw time wave. It is

very good for detecting spikes in a time wave caused by gear issues. A Crest

value > 1,5 is already an indication that spikes are present in the time wave. If

these values/trends become very jumpy or inconsistent, you must consider

analyzing them for possible gear problems.


Last Revised: 9/22/2011 1:46:00 PM 18 (32)

Example of the Time Wave Analysis measurements on gearbox with planet problems.

• Setup Order analysis points on the probes near the planet stage. Keep in mind

that you want track the planets for failure. They spin relatively fast inside the

planet at order 2x-4x that of the main shaft (planet carrier). The planet gear

mesh (used for analyzing planet gear problems) could easily be at order 90x-

110x that of the main shaft speed. Make sure you get at least 2 revolution of

the problem you want to diagnose.

• Use Order Tracking Envelope measurements for the planet bearing detection.

Use Env 3 because again it is here not about the individual frequency of the

bearing but its repetitive frequency.

• Setup a Gear Inspector measurement point. You can setup two Gear Inspector

measurement points if you prefer, but you need to include at least one cycle

of each shaft into the sampling duration. This means a setup of at least 1

KHz, 6400 lines. Measurement must be load and speed coupled.


Last Revised: 9/22/2011 1:46:00 PM 19 (32)

Include all channels/sensors on the gearbox, or if you are using two Gear

Inspector points, include at all the sensors needed for the low speed side of

the gearbox on the one point, and all needed for the high speed side on the

other.

Try to capture this measurement at the highest possible speed and load

condition possible.

Trend ands with alarms can also be setup on this advance combined

measurements results such as:


Last Revised: 9/22/2011 1:46:00 PM 20 (32)


Last Revised: 9/22/2011 1:46:00 PM 21 (32)

Generator measurements

• Setup one normal acceleration measurement and one Envelope 3

measurement for each bearing


Last Revised: 9/22/2011 1:46:00 PM 22 (32)

• You can also setup a band here to trend the rotor bar pass frequency

Envelop 3 measurement settings:


Last Revised: 9/22/2011 1:46:00 PM 23 (32)


Last Revised: 9/22/2011 1:46:00 PM 24 (32)

Oil particle measurements

All sensors that interface by either ModBus and/or CanBus can be directly connected

to WindCon. All such sensors must be however separately powered and working

before connecting them to the WindCon. WindCon can include there data in several

ways into the Observer database. For this Observer provides two measurement

points: Counter and Count Rate. See for detail of setting up these points the

WindCon installation manual.

Ideally we would setup Count Rate points because they count the number of particles

per hour for example and you can hence setup an alarm level easily on these values.

A good start for an alarm/warning level is 20 particles/hour. Below are examples of

such setups:

• For sensors giving as output only a digital pulse simply create two

measurements in the hierarchy for them:

• For sensors that output multiple parameter measurements over ModBus

and/or CanBus we setup a Sub Machine and add all the measurement to that

Sub Machine. This allows Observer to use the Multi Trend graph for display

of this data.

Example of the Multi Trend plot for use with multi parameter sensors:


Last Revised: 9/22/2011 1:46:00 PM 25 (32)


Last Revised: 9/22/2011 1:46:00 PM 26 (32)

Setting up the Asset Maintenance

As of Observer 8.3, big new functionality was implemented, called Asset

Maintenance. This is a planner, tracker, scheduler and MTBF calculator all in one for

all assets monitored and not monitored by WindCon. Assets tracking can be done

based on time only, running hours (coupled then to WindCon’s running hour

calculation) or a combination of both. In the case of running hours coupled, a

Running Hours measurement point is setup on WindCon which will track the

running hours it measures. This calculation can also be automatically compensated

for by load and speed (meaning that 1 hour at 50% load = 0.5 MTBF hours). Assets

can then be setup so that when they get replaced, WindCon will use this Running

Hour calculation to recalculate an accurate custom MTBF for that individual

component. Warning and alarm levels can also be setup so that Observer will warn

you when you have reached an asset’s calculated MTBF. Because this is based on

your individual turbine’s real conditions and your own situation, it is a very powerful

maintenance tool.

The Maintenance planner can also be used to do all routine check lists or Inspection

lists. Simply enter the needed inspection points and couple them all to their

individual inspection time plan. The Maintenance planner will alarm/warn you when

they need to be checked again.

• Setting up a Running Hours point

Select the speed point of your machine and select under simultaneous

measurements the load measurement point if you would like the calculation

to compensate for load changes.


Last Revised: 9/22/2011 1:46:00 PM 27 (32)

• Under trend detail you must type in the nominal speed that your machine has

been measured at. You must look and analyze the speed vs. load trend of this

machines and enter here the maximum speed this individual machine has

been measure at when producing the full load measurement you will type in

at “nominal load”. This allows for accurate compensation.


Last Revised: 9/22/2011 1:46:00 PM 28 (32)

Use the Maintenance Planer to create the assets you would like to monitor and set

them up to be either liked to you running hour point or time based.

You and your customer must now agree on whose responsibility it will be to keep

this information up to data and to enter on time when a component/asset has been

replaced. If this isn’t done with dedication, the Asset Maintenance Planner is

useless. On time entry of actions and maintenance intervals will help to generate

accurate and useful warnings on failures not only based on vibration but also

based on MTBF. A warning telling you that a component is very close to it’s

MTBF is a powerful analyses tool and will help you focus your analyzing efforts

on those components and can therefore significantly contribute to your

monitoring effectiveness.

An account can be setup that will allow that user only access to the maintenance

planner. This is mandatory for when the customer is responsible to enter the

information.

Connecting and interfacing to SKF Lubrication systems

WindCon can interface to the Vogel and other SKF lubrication systems. Again, they

all interface either over ModBus or CanBus to the WindCon. In some cases,

WindCon can also pass through alarms from the oil lubrication system such as “Low

oil level” etc.

Setup follows the same principle as for oils sensors. Create a sub machine and add all

measurements to that sub machine.


Last Revised: 9/22/2011 1:46:00 PM 29 (32)

Blade monitoring system measurements

WindCon can interface, like with oil sensors, also to the Moog (Insensys) blade

monitoring system. This does require the blade monitoring system to be fully

operation before connecting it to the WindCon. Setting up the measurements follows

the same structure and procedure as for oil sensors. Create a Sub Machine, and add

all the needed measurements to that sub machine.

Additional Measurements

Feel free to be an Engineer and experiment with additional measurements. It is not at

thjis point of writing clear whether any of these additional measurements adds value

to the condition monitoring program. In most cases they are for learning, testing new

grounds and research in the hope of finding something useful. Sensors that has either

4-20mA, voltage, ModBus, CanBus or pulse outputs can all be connected tom the

WindCon. Examples of some ideas and experiments:

• Tower sway (using a tilt sensor – just an idea, I have no detail)

• Tower resonance (using a capacitive sensor – I have no detail)

• Gearbox oil and other bearing temperatures (connected straight to a WindCon

from the controller. You soon run out of channels…)

• Yaw angle (using a magnetic sensor that output an offset from magnetically

north – Idea only. I have no detail…but please feel free to be the first to make

it work)

Setting up Workspaces for integration to WebCon

When you want your data to be accessible through WebCon, you will first need to

make your database reachable and accessible to the internet. Well…not completely.

However, your database must be on a fixed permanent connection to the internet.

Access from the WebCon server in Lulea must be granted to you server database by

means of clearing the fix IP of the Lulea WebCon server on your firewall. Once this

is done, the WebCon server in Lulea can now access your database.

For WebCon to create displays from your data, it uses the Workspaces. You must

create your views in the workspaces in Observer and there related process views.

Create them as you would like them to be visible in WebCon and arrange for a user

account and the linking in of your database. You can always change the process view

and a few seconds later is will automatically be changed in WebCon also. You can

therefore administrate the look and feel, and the data that is available to your

customer yourself.


Last Revised: 9/22/2011 1:46:00 PM 30 (32)


Last Revised: 9/22/2011 1:46:00 PM 31 (32)

General good to know information:

Enveloping

For the IMx platform (and MicroLog), the sampling frequency when you select the Enveloper is automatically set to Max filter * 2. So for Env 3, it will be 10KHz * 2 = 20KHz sampling frequency (this is automatically done).

The "frequency range" in Observer refers to a down sampling technique and comes down to the window range you want to analyze in. What is then now important for optimal Envelope use is the SAMPLING DURATION. Sampling duration (as stated by Observer in the screen above as Meas. time) needs to be as long as possible. Resolution is still not the main priority. A golden rule here is to try and get at least 10-15 cycles of the bearing. So, if the bearing spins at 60 rpm, then a sampling duration of 10-20 seconds will do. Longer is better but for wind turbines keep in mind that not too much speed changes should be allowed and the longer the sampling time, the bigger this risk gets.

a typical wind turbine setup for windconwebcon.skfcmc.com/application notes/a typical wind turbine...

Documents