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1. REPRINT
PRÜFTECHNIK Condition Monitoring GmbH • 85737 Ismaning • eMail: info@pruftechnik.com • www.pruftechnik.com
A member of the PRÜFTECHNIK Group
A translation
from
Erneuerbare Energien
Edition 6/2006
Reprint
Condition Monitoring on
'small' systems up to 1500 kW

2. The demand for Condition Moni-
toring Systems (CMS) in the wind
industry was triggered by the re-
view clause adopted by all German
wind turbine insurers in 2002. It
stipulates that all roller bearings in
gearboxes and generators must be
changed after 40,000 operating
hours or 5 years, whichever comes
first. Excepted from this rule are
wind turbines equipped with a
'suitable' certified CMS. By now,
the revision clause is anchored in
almost all insurance contracts. Op-
erators of small wind turbines are
right in asking why only the expen-
sive certified systems may be used,
and why the CMS must transmit
such a large volume of measure-
ment data. They wish for a more
cost-effective CMS package with
on-site condition diagnosis.
Condition Monitoring
methods on wind turbines
Condition Monitoring is the mea-
surement-based recording of the
current vibration condition of drive
train components and its compari-
son with reference measurements.
Gearboxes, generators, toothing,
roller bearings, rotors and electrical
components have typical vibration
patterns and significant damage
characteristics that are particularly
observable in the frequency spectra.
A discussion of what aspects are
important for Condition Monitoring
on wind turbines follows.
VIBNODE®
Wind CMS for
fixed speed wind turbines
VIBNODE®
Wind is essentially
the same as the certified VIBRO-
WEB®
XP except that is does not
feature additional functions only
needed for variable speed wind
turbines. Instead, it offers the con-
tinuous recording of the machine's
operating, condition-related and
vibration behavior, and thereby ex-
ceeds the capabilities of the certi-
fied systems.
VIBNODE®
Wind is the smallest
and most cost-effective CMS for
wind turbines at this time. It oper-
ates autonomously, can be net-
worked and is equipped with 12
analog inputs, 2 pulse inputs, 2
digital inputs and 3 digital outputs.
The robust housing encloses the
measurement computer, FFT ana-
lyzer, Web server and a long-term
memory. It employs HTTP to send
eMails and measurement data and
does not require FTP components.
VIBNODE®
is accepted by leading
insurers for wind turbines up to
1500 kW and has already been de-
ployed in many systems around the
world.
VIBNODE®
Wind has the follow-
ing special features:
• Its hardware is optimally de-
signed for fixed speed turbines
• Its database software is straight-
forward and user-friendly
• It continuously records vibra-
tion, condition-related and diag-
nosis values over the entire oper-
ating range
• In-depth analysis and prelimi-
nary evaluations takes place au-
tonomously
• Automatic warnings and data
transmission do not require FTP
• It works together with a central
diagnostic center that offers data
storage and provision
Optimal hardware design
VIBNODE®
Wind is installed in
the control booth and connected to
the sensors attached to the drive
train. It requires a 24 VDC power
supply and a standard network
connection for communication.
Both connections can be laid by
any electrician. Optionally, a power
pack can be installed and the TCP/
IP communication can take place
via a telephone modem. The router
functionality is already integrated
in VIBNODE®
.
VIBNODE®
monitors the condi-
tion-related, operating and natural
vibration behavior of fixed speed
drive trains, in particular as they
relate to the toothing and roller
bearings. For this purpose, a num-
ber of accelerometers and displace-
ment transducers are mounted at
typical measurement locations
(Fig. 2). Particle counters can also
be connected if required.
Displacement transducers are
used because in the slow running
range of the drive train, vibration
diagnosis comes up against its lim-
its. This phenomenon can be com-
pared to the effects of a damaged
car wheel: An imbalance in the
wheel only becomes perceptible in
the steering wheel above a certain
driving speed. In the VIBNODE®
package, therefore, at least one
displacement sensor is mounted in
the drive area to be able to quickly
and reliably identify increases in
play and changes in the displace-
ment and in axial vibrations. In
addition, radial displacement sen-
sors can optionally be installed off-
set by 90 degrees in the area of the
main bearing.
Database software –
straightforward
and user-friendly
VIBNODE®
uses a database-
powered PC software for eval-
uating, archiving and docu-
menting the measurement
data and for programming
the CMS. Measurement tasks
and locations, operator name,
wind farm number, wind tur-
bine number and the drive
train component are arranged
in a directory tree and clearly
described. These data are re-
corded together with the
Fig. 1: VIBNODE®
system concept
Dr. Edwin Becker
Roland Schühle
Condition Monitoring is now of interest for fixed speed wind turbines with up to 1,500 kilowatts.
An article by Dr. Edwin Becker and Roland Schühle, PRÜFTECHNIK Condition Monitoring GmbH
Measurement over more than two power ranges
Operation
• Alarm handling
Maintenance Department
• Trend analysis
CMS partner
• Telediagnosis

3. measurement date in the mea-
surement diagram. In the event of
an alarm, the colored symbols in
the OMNITREND®
tree guide the
user to the relevant diagnostic pa-
rameter.
This clear structure makes it
possible to compare results for
different machines and to take
advantage of database functions.
Using the optional WebReport
module, operators can download
the measurement data directly
from the CMS on their wind tur-
bine.
Continuous measurement
of vibration & diagnosis
parameters
Experience with certified sys-
tems such as VIBROWEB®
XP and
WinTControl®
has shown that for
every wind turbine and power
range, 1 to 2 MB of measurement
data are accumulated per day. Cer-
tification requires that the mea-
surement results for two power
ranges be completely transmitted
to the diagnosis center for diagno-
sis. For a typical drive train with a
planetary/spur gear, this would
mean that diagnosis specialists
would have to monitor about 200
diagnosis parameters. In light of
this, the following questions arise:
Can't this type of routine task be
performed directly in the CMS?
And why limit the measurements
to two power ranges?
In VIBNODE®
, frequency analy-
ses can be performed on a continu-
ous basis. Up to 25 diagnosis pa-
rameters can be monitored per fre-
quency analysis and measurement
location over the entire load range
(based on signal peaks or signal
power). Fixed speed and variable
speed frequency bands may be su-
perimposed since these bands are
clearly distinguished. The follow-
ing example illustrates why it is
useful to measure over the entire
operating range.
Figure 3a shows the “Roller bear-
ing vibration” diagnosis parameter
of a spherical roller bearing. This
particular continuous measure-
ment shows time ranges with am-
plitudes over 1 m/s² and areas
with significantly lower ampli-
tudes. These fluctuations in excita-
tion amplitude are due to one-
sided race damage on the inner
race of the spherical roller bearing,
marked in red in the gear illustra-
tion (Figure 3b). When loads act-
ing on the gearbox cause an axial
displacement, there is less damage
excitation and measurements are
lower. If measuring is mobile, or if
the power ranges were unfavor-
ably selected, it will not be possible
to clearly identify the damage.
Autonomous in-depth
analyses and pre-evaluation
The volume of raw data to be
processed by Condition Monitoring
Systems is enormous. Most (certi-
fied) CMS reduce data flow by
calculating the frequency spectra
from the measured time signals
and then saving and sending them
as smaller data packets. These can
be the vibration velocity, accelera-
tion or envelope spectra.
With VIBNODE®
, employees
with administrator rights can de-
fine how frequency spectra should
be handled. The following three
scenarios are possible and can be
combined:
• All measured frequency spectra
are sent and saved. PRÜFTECH-
NIK uses this method, for exam-
ple, during the startup service of
newly installed CMS.
• Frequency spectra are sent three
times a day. This procedure is
currently necessary if the moni-
toring is to conform with insur-
ance requirements.
• Frequency spectra are only sent
when an alarm is violated. VIB-
NODE®
autonomously evaluates
changes in the parameters and
automatically provides the Diag-
nosis Center with the associated
frequency spectra as soon as one
or more threshold values are ex-
ceeded.
Automatic alarm
and data communication
Communication between VIBN-
ODE®
on the wind turbine and the
Diagnostic Center takes place auto-
matically via eMail with an attach-
ment. The following scenarios are
possible:
• Daily, time-controlled sending of
operating messages from the
CMS via eMail
• Daily sending of operating, vi-
bration and diagnosis parame-
ters
• Time-controlled and results-de-
pendent sending of frequency
spectra
• Immediate sending of warning
and alarm messages
• Immediate sending of frequency
spectra when a fault occurs
The eMail is identified in the
OMNITREND®
eMail server by its
subject line. Since VIBNODE®
is
Ethernet-compatible, the CMS can
be integrated into existing network
infrastructures and data lines with
high bandwidths can be used (e.g.
DSL, Fig. 4). If a network is not
available, a telephone modem will
be used for communication, which
can be retrofitted in the VIBNODE®
switch cabinet.
Central Diagnostic Center
with data storage & provision
A suitable (certified) Condition
Monitoring hardware alone is not a
guarantee of dependable fault di-
agnosis. To achieve reliable results,
it is essential that the CMS be
correctly installed, parameterized
and maintained, and that diagnosis
Fig. 2: Typical measurement locations on a drive train

4. specialists and maintenance per-
sonnel respond rapidly and cor-
rectly to reported condition chang-
es. Since not every wind farm oper-
ator has the necessary diagnosis
know-how or qualified service per-
sonnel, PRÜFTECHNIK offers these
services at its Diagnostic Center.
For operators who use the Condi-
tion Monitoring system themselves
and wish to build up their own
Diagnostic Center, PRÜFTECHNIK
saves the measurement data and
makes the results accessible on the
Internet ('data hosting'). Via a
password-protected access point,
registered users can download the
measurement results and edit them
interactively.
If PRÜFTECHNIK is also con-
tracted to evaluate the measure-
ment data, the staff at the Diagnos-
tic Center ensures that the parame-
terization and threshold settings of
the CMS are correct, routinely
checks the incoming measurement
data, prepares machine condition
reports and responds appropriately
to incoming alarm
and warning mes-
sages. After a dam-
age diagnosis, the
Diagnostic Center
works closely with
the customer to
develop corrective
measures.
Fig. 4: VIBNODE®
system concept – data transmission via DSL and eMail
Ethernet
LAN
Internet
DSL
Firewall
SMTP server
eMail eMail
Wind farm operator Telediagnosis partner
Fig. 3b: One-sided race damage on
the spherical roller bearing of the
spacer shaft
Fig. 3a: Damage generates variations in the amplitude of the characteristic
values of the envelope spectra.
Contact
PRÜFTECHNIK Condition Monitoring
Tel.: +49 89 99616-0
eMail:info@pruftechnik.com
www.pruftechnik.com