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renewable
energy
should not be burdened with more
than one alarm per physical fault and
an efficient alarm filtering system
is therefore required to avoid alarm
flooding.
Alarm management how to
avoid alarm flooding
In order to filter this multitude of
alarms which can occur simultane-
ously, Brüel & Kjær Vibro has imple-
mented an alarm management sys-
tem - the Alarm Manager - in the cen-
tral diagnostic server. More than one
hundred characteristic scalar values
are monitored for each turbine. Each
of these values is stored in a power
class reflecting the running condi-
tions of the turbine when the value
was recorded. Each of the power
classes has its own alarm limits re-
sulting in 500 to 1000 alarm limits for
each turbine. The diagnostic server
closely monitors each of the recorded
values and provides an alarm each
time an alarm limit is exceeded. The
combined pattern of these alarms
indicates a progressing mechanical
fault on one or more of the turbine
components. The Alarm Manager
programme looks for high-resolution
alarm information in the diagnostic
server database, as shown in Figure
5. All incoming and previous alarms
are evaluated and transformed into a
single alarm notification for each part
of the turbine. The alarm information
is graduated into five severity levels
in order to provide Vestas' service
management with a lead-time esti-
mate on a developing fault [Table 1].
The automated severity assessment
performed by the Alarm Manager
results in a preliminary severity level
which subsequently is verified (and
possibly changed) by the diagnostic
experts in the condition monitoring
centre. The result is a final severity
level which is applied in the CMS
Alarm report dispatched to the Ves-
tas service department (see "Integra-
tion with Service departments"). The
segregation of alarms into severity
classes helps avoid alarm flooding
because new alarms are issued only
when a new severity level is reached
and a maximum of four alarm notices
will be issued during the "lifetime" of
a fault.
Integration with Service
departments
Vibration condition monitoring is a
specialist field abundant in technical
terms and complicated graphs which
are of little use to a busy service
management department. The chal-
lenge is therefore to transform the
technical information into actionable
information which immediately can
be applied by practical people.
In the Vestas implementation of
condition monitoring this has been
achieved by conveying all condition
monitoring alarms from the condi-
tion monitoring centre to the service
departments in the format of a CMS
Alarm Report [Figure 6. CMS Alarm
report]. The reports comes in a fixed
two page format with a clear split be-
tween the observation, interpretation
and the assessment of the recom-
mended maintenance needs. This
information along with the severity
classification provides the service
Figure 6. CMS Alarm report