Solutions for Inspecting Wind Turbines with Sensors

Wind turbines have to be monitored 24/7 due to safety and cost reasons. Lightning, defective rotor blades or tower movements because of localized storms can have critical consequences until the wind turbine finally collapses. Precision sensor technology from Micro-Epsilon is already in use during production as well as in the instantaneous monitoring of active plants. The sensors enable the plant operator to intervene early during production or to switch off the operating wind turbine early enough to avoid damage or danger. Targeted monitoring using advanced sensor technology lowers the costs of maintenance and servicing.

Due to safety and cost reasons wind turbines require 24/7 monitoring. Precision sensor technology from Micro-Epsilon is already used during production as well as in the real-time monitoring of active plants.

Due to safety and cost reasons wind turbines require 24/7 monitoring. Precision sensor technology from Micro-Epsilon is already used during production as well as in the real-time monitoring of active plants.

Predictive Maintenance

Harnessing wind power has been used for several years, for instance, to power sailing ships and windmills. Currently, generating power is the most vital use of wind energy. Wind turbines are used offshore and onshore for power generation. The rotor towers of these huge plants weigh dozens of tons and are extremely tall. Their average rotor diameter is approximately 110 m and the average hub height is approximately 130 m.

If such equipment fails a high financial cost will be incurred. Cranes and other machines are usually unavailable at short notice. Above all, offshore farms are not easily accessible at any time of night or day. Because of wear and the complexity of plants, besides environmental influences, there are also many possible problems such as gear faults, temperature differences, gear wheel wear, shaft issues, imbalance, material fatigue, lubrication faults and bearing clearances, which do not only obstruct smooth operation but might also involve other ensuing or secondary damage.

Predictive Maintenance plays a vital role here. Proactive monitoring based on precision sensor technology has already started to be applied in the production process and continues in test benches and real-time monitoring during turbine operation. Wear of parts or deviations in production should be predicted before catastrophic damage happens.

Thus, it is possible to take precautions long before the tools start to wear out or the parts fail. Not only can present states be documented, but variations and trends in measurement data can be examined and evaluated. Maintenance becomes predictable and unexpected failure or downtime of these large plants is decreased to a minimum. This is how productivity can be raised while efficiently saving money and using resources.

New and innovative sensor solutions from Micro-Epsilon enable reliable measurements and targeted assessment of a significant amount of critical data. In a wind turbine, gap measurement of the plain bearing, the offset of the coupling ring, temperature monitoring of the generator and air gap monitoring in the generator are, amongst other things, vital factors.

In a wind turbine, the offset of the coupling ring, gap measurement of the plain bearing, temperature monitoring of the generator and air gap monitoring in the generator are, amongst other things, critical factors.

In a wind turbine, the offset of the coupling ring, gap measurement of the plain bearing, temperature monitoring of the generator and air gap monitoring in the generator are, amongst other things, critical factors.

Offset Measurement of the Coupling Ring

Above 100 m, huge wind loads act on the rotor blades, tower and housing, and so gearbox and generator have an elastic bearing. Therefore couplings in wind turbines must balance the relative movement of the generator and gearbox. When measuring the offset of the coupling ring, eddy current sensors establish the distance, while measuring onto the metallic coupling ring. This leads to the determination of the load profile. Monitoring the measured values is required so as to avoid pointless wear of bearings, couplings, and shaft seals or, in extreme cases, critical damage to the wind turbine.

When measuring the offset of the coupling ring, eddy current sensors determine the distance, while measuring onto the metallic coupling ring.

When measuring the offset of the coupling ring, eddy current sensors determine the distance, while measuring onto the metallic coupling ring.

The measurement is done in various directions – in the radial, axial and tangential axes. The eddyNCDT 3001 and 3005 eddy current sensors are temperature-compensated and thus offer high stability, even in extremely fluctuating ambient temperatures. They are factory-calibrated for ferromagnetic and nonferromagnetic materials, which eliminates the need for field calibration of the sensor.

Because of factory calibration, eddyNCDT 3001 and 3005 sensors offer temperature stability and high accuracy, making them mainly ideal for nonstop operation in industrial environments. The sensors can be quickly exchanged due to, amongst others, their M12 housing. They are sturdy, protected to IP67 and their compact design allows them to be fitted into the smallest of installation spaces.

The sensors are thus ideal for predictive wear and condition monitoring tasks. Compared to inductive switches and sensors, these models offer a higher bandwidth and so are appropriate for precise detection of high speed movements.

Gap Measurements in Plain Bearings

Hydrostatic bearings are used in large plant and machinery such as telescopic installations, stone mills and also wind turbines. The task is to monitor the gap size between the shaft and the bearing surface. In the lubricating gap is an oil film which prevents direct contact between the shaft and the bearing surface. In the case of a breakdown in the hydraulics, the oil pressure can rise and, in extreme cases, the gap will close. This would lead to damage of the bearing and in turn to a probable plant failure. Thus, the sensor is mounted horizontally to the bearing shoe. It measures through the oil film and the plant bearing directly onto the shaft.

In the case of a malfunction in the hydraulics, the oil pressure can rise and, in extreme cases, the gap will close. The sensor measures through the oil film and the plant bearing directly onto the shaft.

In the case of a malfunction in the hydraulics, the oil pressure can rise and, in extreme cases, the gap will close. The sensor measures through the oil film and the plant bearing directly onto the shaft.

In this case, eddyNCDT 3001 and 3005 non-contact eddy current displacement sensors are used. They are perfect as they possess a robust, compact design with integral controller. Eddy current sensors from Micro-Epsilon are regularly used in applications where challenging ambient conditions are present and where highest precision is required. Immunity to lubricants, pressure and extreme temperature are unique features of eddy current sensors. Other requirements with respect to the sensor technology are the possibility to retrofit to existing plant and fast commissioning. Due to the global use of these plants, the sensor should be easy to replace.

Air Gap Monitoring in the Generator

With very large generators and electric motors, it is crucial to determine the radial run out of the rotor within the motor compared to the stator. Because of imbalances during operation which could be due to wear caused by high wind and weather conditions, the rotor might touch the stator. This could result in catastrophic failure. This is why capacitive and optical sensors are used to measure the distance between the rotor and stator and to monitor the rotor gap at the same time as the motor is in operation. The sensor technology is centered on capacitive sensors with a measuring range of 0 to 8 mm.

Capacitive sensors from Micro-Epsilon are engineered for non-contact measurement of displacement, position and distance. They stand out thanks to reliability, long-term stability and temperature stability. During air gap monitoring in a generator, the average temperature is approximately 120 °C. However, advanced and innovative MicroEpsilon sensor technology enables very precise measurements under challenging conditions. The sensors used are specially adapted to measurements in a generator. They possess vibration resistance and are protected by a special housing.

Their unique, triaxial design enables flush installation into electrically conductive materials as the guard ring electrode and grounding are also situated on the front edge of the sensor in conjunction with the measurement electrode.

Capacitive sensors from Micro-Epsilon are unique because of their high electromagnetic compatibility. Exchanging the sensors does not require any new recalibration whereas conventional systems were subject to difficult calibration and linearization procedures.

Capacitive sensors from Micro-Epsilon are designed for non-contact measurement of displacement, distance and position. They stand out due to long-term stability, reliability and temperature stability.

Capacitive sensors from Micro-Epsilon are designed for non-contact measurement of displacement, distance and position. They stand out due to long-term stability, reliability and temperature stability.

Not only in wind turbines but in nearly any application in various industries, innovative sensor technology prevents repairs, minimizes failures, helps to predict maintenance cycles and lowers costs. Compared to manual inspection where differences can rely on the person’s tiredness and changing mood, sensors offer high precision, reliable and repeatable measurement results. Micro-Epsilon is recognized for high precision measurement technology. The product range comprises of inductive, confocal chromatic and capacitive sensors, along with eddy current, laser, draw-wire and temperature sensors, including inspection and measurement systems, for example for advanced 3D surface inspection.

Inductive sensors from Micro-Epsilon based on the eddy current principle are often used in applications where harsh ambient conditions are present and where high precision is required.

Inductive sensors from Micro-Epsilon based on the eddy current principle are often used in applications where harsh ambient conditions are present and where high precision is required.

Conclusion

The sensor solutions, which are customer-specific in a majority of cases, are from a single source. The sensor manufacturer develops, produces and distributes the technology. More precision, miniaturization and easy integration into machines as well as data transmission via sophisticated interfaces are main factors. With 25 subsidiaries at home and abroad, the company combines long-term knowledge of high precision metrology and offers a global unique product range of cutting-edge technologies for future industry requirements.

Micro Epsilon

This information has been sourced, reviewed and adapted from materials provided by Micro Epsilon.

For more information on this source, please visit Micro Epsilon.

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