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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Kun Marhadi Brüel & Kjær Vibro A/S, Denmark
Kun Marhadi (1) F Alexandros Skrimpas (1)
(1) Brüel & Kjær Vibro A/S, Nærum, Denmark

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Kun Marhadi is a development engineer in the Remote Monitoring Group at Brüel & Kjær Vibro. He joined Brüel & Kjær Vibro in 2012. Previously, he worked as a postdoctoral fellow in the Department of Mathematics at the Technical University of Denmark (DTU). He received his PhD in computational science in 2010 from San Diego State University and Claremont Graduate University. He has M.S. and B.S. in aerospace engineering from Texas A&M University. Dr. Marhadi's expertise is in structural vibration and analyses, probabilistic methods, and design optimization.


Poster Download poster (7.35 MB)


Uncommon Faults Detected by Wind Turbine Condition Monitoring System


Condition monitoring system (CMS) has become an important part of wind turbines operation and maintenance. Its installation helps plan maintenance in case a machine component fault occurs and to maximize up-time. CMS is mainly installed to detect problems related to the main bearing(s), gearbox components, and generator bearings. Common faults detected by vibration based CMS are broken tooth/teeth of the gears, bearing related problems such as inner race or outer race defect, looseness, and unbalance problem of the generator. With additional accelerometers installed to monitor tower vibration, faults related to the blades such as blade unbalance can also be detected. The present study shows that CMS is also capable of detecting other faults with potentially similar costly downtime, such as problems with pitch and yaw systems.


Accelerometers are installed on wind turbine components where potential faults may be detected by CMS. For typical Brüel & Kjær Vibro wind turbine CMS application, an accelerometer is installed on each main bearing, at least one accelerometer on each gearbox stage, and one accelerometer on each generator bearing. Accelerometers are also installed to monitor tower vibration in downwind and lateral directions. From each accelerometer, different vibration measurements in different frequency ranges are taken and trended overtime. When one (or more) of the measurements increases and crosses a predetermined limit, it would indicate a certain failure mode and trigger an alarm. Diagnostic engineers in a remote location would evaluate the alarm, perform detailed diagnosis, and verify the potential fault. Uncommon faults would exhibit certain increase of the measurement(s) that is not normally associated with common/known faults.

Main body of abstract

CMS is installed to have early detection of potential faults at main bearing(s), gears and support bearings of the gearbox, and generator bearings. However, there are also faults that can cause costly downtime such as problems with the pitch system, yaw system, and loose slip ring unit. Excessive vibration due to incorrect blade pitch calibration cannot be undermined either. These faults can be detected by common CMS although their vibration characteristics are less well-known. This study focuses on how the aforementioned faults can be detected by common vibration based CMS. Loose slip ring unit can be easily detected using accelerometers installed on generator bearings. Pitch assembly issues can be detected by accelerometer installed on main bearing closed to the hub. While incorrect blade pitch calibration and problems with the yaw system can be detected and verified by having accelerometers that monitor tower vibration. Each fault exhibits certain increase in the vibration measurements, and time waveforms from the sensors show certain characteristics that need to be evaluated and verified by the diagnostic engineers. Findings from field technicians help engineers correlate vibration signatures with the actual faults found.


Vibration based CMS can detect faults other than faults it is normally designed to detect. These uncommon faults can potentially cause costly downtime. With the help of experience engineers and good feedback from technicians in the fields, identifying those uncommon faults is possible. Thus potential secondary damages and/or costly downtime can be avoided.

Learning objectives
This work aims to show that CMS in wind turbines can also detect faults that CMS are not normally designed to detect. The study shows the importance of having experienced engineers who can evaluate the potential faults and field technicians who feedback the engineers of the actual finding in the turbine. Thus certain faults that are not known previously can be correlated with certain vibration characteristics evaluated by the engineers. The last objective is to show the importance of monitoring tower vibration because it can help detect some of the uncommon faults.