6
uptime
m
e
gazine · 01/09
Condition
monitoring
onwindturbines
Continuous remote condition moni-
toring on wind turbines requires a
permanently installed measurement
system for data acquisition and -
processing of the required physical
parameters. This so-called condition
monitoring system (CMS) consists of
a dedicated electronic data acquisi-
tion board and - in the case of vibra-
tion condition monitoring - a number
of accelerometers mounted on the
turbine drive train, generator and
main bed frame [Figure 2].
The primary functions of the data
acquisition unit are:
n
Automaticmonitoring Vibra-
tion, operating parameters and
time waveforms are automatically
recorded and monitored at fixed
intervals and sent to a diagnostic
server in the condition monitoring
centre.
n
Userrequestedtimewaveforms
Upon a user request the data
acquisition units can record time
waveforms used for detailed fre-
quency and time series analysis.
n
Automaticeventrecorder - Time
waveform data is automatically
stored before and after a user-
defined event, thus allowing the
condition monitoring centre to do
advanced vibration post-analysis
to identify developing faults.
A wired internet connection (DSL)
with adequate bandwidth is used to
transmit scalar data and time series
over a web-server to the condition
monitoring centre. The time series,
sampled at 25.6 kHz, are not continu-
ously transmitted over the internet,
but recordings of 10-40 seconds
length are transferred at regular in-
tervals (typically every week or every
month depending on the line quality).
The scalar data are processed values
extracted from the measured time
waveforms. In each turbine more
than 100 parameters (scalar values)
are monitored, including overall RMS,
bandpass values, speed depend-
ent parameters such as vibration at
tooth mesh frequencies and their
harmonics and vibration at one and
two times shaft running speed. The
analysis of these parameters and the
underlying time waveforms allows
the diagnostic experts to identify me-
chanical failure modes such as
n
Bearing Faults
n
Coupling Faults
n
Misalignment Faults
n
Gear Faults
n
Unbalance
n
Support Structure Faults
Figure 2: Schematic representation
of a vibration condition monitoring
system comprised by a data acquisi-
tion unit and accelerometers (yellow
circles) mounted on the drive train
and generator. The purple circle
indicates a proximity switch which
measures the revolution speed of the
generator shaft.
Figure 3. The measured vibration
signals vary with the active power
and must be separated into active
power bins to facilitate trending.