01/09 ·
uptime
m
e
gazine
renewable
energy
B. Bearing fault detected
in generator bearing
Severity assessment by
trending in Active Power
Bins
Wind turbines operate in widely vary-
ing conditions, and consequently the
vibration response of the machine
components also varies with the ex-
ternal loading. In order to facilitate a
meaningful comparison of vibration
levels recorded at different times and
conditions the measurement data
must be classified according to the
turbine's active power level at the
time of recording. A group of active
power bins and their corresponding
alarm limits were defined by Brüel &
Kjær Vibro and Vestas so that data
can be stored in the diagnostic server
and monitored in their correspond-
ing power bins. Figure 3 provides an
illustration of this concept. Here the
yellow lines indicate an alert level
adapted to the individual turbine and
the red lines indicate a turbine type
specific danger level. This data cap-
ture strategy allows faults to be auto-
matically detected in any power class
and the severity of the detected fault
can be assessed from the relative
strength of the vibration level. Also
Figure 4. Examples
of mechanical faults
detected using trend-
ing of fault symp-
toms.
A. Inner ring fault detected
in gearbox intermediate
shaft bearing
the rate of change of the meas-
ured levels provides an estimate of
the remaining useful lifetime of the
affected component.
Examples of Fault detection
by historical trending of
Fault Symptoms
Figure 4 shows real life examples of
faults detected in wind turbines using
the above described trending of fault
symptoms.
ExampleA. is a detected inner ring
fault in a gearbox intermediate shaft
bearing. The RMS level departed from
the reference level in early July, and
in October the bearing was replaced
as the vibration level approached the
danger mark. Had this bearing run
to complete failure, the entire gear-
box should have been replaced due
consequential damage. This example
thus illustrates the achievable lead
time to maintenance and the potential
repair savings which can be realised
by the application of vibration condi-
tion monitoring.
ExampleB. is a detected inner ring
fault in a drive-end generator bearing.
Again the usage of condition monitor-
ing made it possible for the service
department to plan the replacement
of the component before catastrophic
breakdown occurred.
Finally,exampleC. illustrates that
shaft misalignment can be detected
by monitoring of the RMS 1st order
magnitude. In this case the alignment
was caused by a slowly developing
coupling fault.
It will be noted that in all three exam-
ples the vibration levels drop back to
the reference levels after component
replacement.
C Coupling fault