GB2463081A - Detecting loosening of wind turbine fastener using pressure or displacement responsive switch - Google Patents

Detecting loosening of wind turbine fastener using pressure or displacement responsive switch Download PDF

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Publication number
GB2463081A
GB2463081A GB0815973A GB0815973A GB2463081A GB 2463081 A GB2463081 A GB 2463081A GB 0815973 A GB0815973 A GB 0815973A GB 0815973 A GB0815973 A GB 0815973A GB 2463081 A GB2463081 A GB 2463081A
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United Kingdom
Prior art keywords
switch
fastener
pressure
wind turbine
displacement
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0815973A
Other versions
GB0815973D0 (en
Inventor
xiao qian Li
Ingemann Hvas Sandvad
Erik Sloth
Peter Lindholst
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vestas Wind Systems AS
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Vestas Wind Systems AS
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Publication date
Application filed by Vestas Wind Systems AS filed Critical Vestas Wind Systems AS
Priority to GB0815973A priority Critical patent/GB2463081A/en
Publication of GB0815973D0 publication Critical patent/GB0815973D0/en
Publication of GB2463081A publication Critical patent/GB2463081A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/24—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D80/00—Details, components or accessories not provided for in groups F03D1/00 - F03D17/00
    • F03D11/00—
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D17/00—Monitoring or testing of wind motors, e.g. diagnostics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
    • G01L5/24—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed
    • G01L5/243—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed using washers
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/02—Details
    • H01H13/12—Movable parts; Contacts mounted thereon
    • H01H13/14—Operating parts, e.g. push-button
    • H01H13/18—Operating parts, e.g. push-button adapted for actuation at a limit or other predetermined position in the path of a body, the relative movement of switch and body being primarily for a purpose other than the actuation of the switch, e.g. door switch, limit switch, floor-levelling switch of a lift
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H35/00—Switches operated by change of a physical condition
    • H01H35/006—Switches operated by mechanical overload condition, e.g. transmitted force or torque becoming too high
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/30—Retaining components in desired mutual position
    • F05B2260/301—Retaining bolts or nuts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/30—Control parameters, e.g. input parameters
    • F05B2270/301—Pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/50—Control logic embodiment by
    • F05B2270/502—Control logic embodiment by electrical means, e.g. relays or switches
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Wind Motors (AREA)

Abstract

A system for detecting the loosening of a wind turbine fastener 10 comprising a pressure or displacement responsive switch 16 and at least one output or signalling device. The signalling means may be wireless and the output device may comprise a light emitting device 18. The fastener preferably comprises nut 26 and bolt 22, perhaps with a washer or plate 24. The switch is mounted on the wind turbine and is connected to the fastener such that the pressure or displacement detected at the switch varies as a function of the fastener's tension. The switch is adapted to actuate when the pressure or displacement reaches a threshold value as a result of loosening of the fastener. The output device is operatively connected to the switch and is activated to provide an output signal upon actuation of the switch. The invention also relates to a method of monitoring a fastener on a wind turbine using such a system and to a like arrangement comprising a plurality of wind turbine fasteners and a plurality of pressure or displacement responsive switches with associated output devices.

Description

WIND TURBINE SENSOR SYSTEM AND METHOD
The present invention relates to a sensor system and method for monitoring one or more fasteners on a wind turbine in order to detect the loosening of any of the fasteners. In particular, the present invention relates to a sensor system and method for monitoring one or more fasteners on a wind turbine using one or more pressure or displacement responsive switches.
A large number of mechanical fasteners, typically of a nut and bolt construction, are currently used to connect the different components of a wind turbine to each other. For example, the blades and blade bearings are typically connected to the hub of the wind turbine by means of a number of nut and bolt fasteners. It is extremely important that the fasteners provide a reliable connection between the components of the wind turbine and are able to withstand the loads to which they may be subjected during use of the turbine. The loosening or failure of one or more of the fasteners is clearly highly undesirable since it could not only reduce the efficiency of the wind turbine but could also, at worst, result in the connected components becoming detached from each other.
Various methods and apparatus for tightening fasteners are known, which measure the tension in a fastener in order to ensure that the fastener is tightened to the correct level of tension or torque. For example, EP-A-1 764 596 describes a system and method for measuring the pre-tension in a screw connection, which is suitable for use in the assembly of wind turbines. However, even with effective measures in place to ensure the correct initial level of tightening of the fasteners on a wind turbine, there is a risk that one or more of the fasteners will self-loosen during operation of the wind turbine. This loosening may occur for a number of reasons, but common causes of failure in the nut and bolt fasteners used in wind turbine blades are the breakage of the bolt due to its elongation and the self-rotation of the nut relative to the bolt as a result of load, or the vibration of the wind turbine components during operation.
In view of the large number of fasteners used in each wind turbine and the fact that the fasteners may not necessarily be visible during use of the turbine, it may be very difficult to detect the presence of any loosened fasteners. A number of different systems for continuously monitoring the tension in a fastener have been proposed; however, the construction and functioning of the known systems are such that they are unsuitable for use on wind turbines.
It would be desirable to provide a simple, cost-effective and reliable system for monitoring the fasteners on a wind turbine, so any loosened fasteners can be immediately and easily detected and subsequently or simultaneously located. It would also be desirable to provide a system that enables a large number of fasteners on a wind turbine to be monitored concurrently but which does not interfere with the normal functioning of the turbine. It would be particularly desirable if such a system could be used in conjunction with nut and bolt fasteners of a conventional construction. It would further be desirable to provide a method for monitoring the fasteners on a wind turbine blade using such a system.
According to a first aspect of the present invention there is provided a wind turbine sensor system for detecting the loosening of a fastener on a wind turbine, the system comprising: a pressure responsive switch operatively mounted on the wind turbine and connected to the fastener such that the pressure at the switch varies as a function of the tension of the fastener, wherein the switch is adapted to actuate when the pressure reaches a threshold value as a result of the loosening of the fastener; and at least one output device for providing an output signal when the fastener is loosened, wherein the at least one output device is operatively connected to the pressure responsive switch such that it is activated to provide the output signal upon actuation of the switch.
According to a first aspect of the present invention there is also provided a wind turbine sensor system for detecting the loosening of a fastener on a wind turbine, the system comprising: a displacement responsive switch operatively mounted on the wind turbine and connected to the fastener such that a displacement detected at the switch varies as a function of the tension of the fastener, wherein the switch is adapted to actuate when the displacement reaches a threshold value as a result of the loosening of the fastener; and at least one output device for providing an output signal when the fastener is loosened, wherein the at least one output device is operatively connected to the displacement responsive switch such that it is activated to provide the output signal upon actuation of the switch.
The present invention provides a simple, yet robust and reliable system for detecting the loosening of a fastener, which can be used to monitor one or more fasteners at any location on the wind turbine without significantly affecting the overall function and efficiency of the turbine.
The sensor system of the present invention can be constructed with simple, relatively low cost components, such that the cost of incorporating the system into a wind turbine is very low in comparison to the overall cost of the turbine, even where it is required to monitor a large number of fasteners. Furthermore, the size and weight of the sensor system may advantageously be very low in comparison to the overall weight of the wind turbine components.
Unlike the systems of the prior art, which are designed to continuously monitor the tension of a fastener and detect changes in the tension, the sensor system of the present invention is only activated when a loosened bolt is detected. Advantageously, the power consumption of the sensor system of the present invention is therefore negligible for the majority of the time that it is in use and the system therefore offers a cost-effective way of monitoring a large number of fasteners over the lifetime of the turbine, which could be a considerable number of years.
Advantageously, the sensor system of the present invention is suitable for use with conventional wind turbine fasteners, including the nut and bolt type fasteners commonly used in the construction of wind turbines. This means that the sensor system of the present invention can conveniently be incorporated into a wind turbine with little, if any, modification to the design of the wind turbine, the fasteners, or the systems and methods for the assembly of the wind turbine.
Furthermore, in view of the large numbers of fasteners typically required for each wind turbine, it is preferable to use conventional nut and bolt fasteners rather than specialist fasteners which will almost certainly be more expensive and may also be heavier and require specialist skills and/or apparatus for installation purposes. In addition, if the sensor system of the present invention is used with conventional fasteners, the sensor system can be incorporated without the need for additional certification, since no structural modification to the fasteners or the wind turbine structure is necessary.
The sensor system of the present invention employs a "responsive switch" which may be either a pressure responsive switch, or a displacement responsive switch, which is also commonly referred to as a displacement switch.
The term "pressure responsive switch" is used to refer to a switching arrangement that senses changes in pressure and responds to such changes by making or breaking an electrical connection.
The pressure responsive switch of the system of the present invention is a set-point pressure switch that actuates when a specified pressure is reached. The switch is adapted to be mounted on the wind turbine in direct or indirect connection with the fastener so that the pressure at the switch varies in a predictable way as the tension in the fastener decreases. The pressure being sensed by the switch during use of the system of the present invention will typically be a mechanical pressure exerted by a part of the fastener, either directly or indirectly, but could also be air pressure.
As the fastener becomes loosened, the tension of the fastener decreases, resulting in a corresponding change in the pressure at the pressure responsive switch. Depending on the arrangement of the sensor system and the type of pressure responsive switch employed, the pressure at the switch may increase or decrease as the fastener becomes loosened.
The term displacement responsive switch" is used to refer to a switching arrangement that senses the displacement of a component and responds to such displacement by making or breaking an electrical connection.
The displacement responsive switch actuates when a specified displacement of the monitored component is reached. In the system of the present invention, the displacement switch is adapted to be mounted on the wind turbine in direct or indirect connection with the fastener so that it detects the displacement of a component of the fastener, or a connected component, as a result of the loosening of the fastener. The displacement detected at the switch varies in a predictable way as the tension in the fastener decreases. As the component is displaced, it will typically exert a mechanical pressure on the switch until eventually at a certain displacement, the switch will be caused to close.
The pressure or displacement responsive switch of the sensor system of the present invention may consist of a single component in an electrical circuit. For example, the responsive switch may be a tactile switch which responds directly to the pressure exerted on it, or the displacement of a component of the fastener. Alternatively, the responsive switch may consist of two or more components including a means for sensing pressure or displacement and an associated switch to be actuated when the pressure or displacement reaches the threshold value. For example, a suitable pressure responsive switch may include a pressure sensor such as a thin film pressure sensor, which has electrical properties that vary with the pressure detected by the sensor. A pressure sensor of this type could be connected to a switching circuit in such a way that a switch is actuated to close the circuit when the pressure detected at the sensor falls reaches a predetermined threshold value. Suitable circuits for achieving this will be known to the person skilled in the art.
The threshold value of pressure or displacement beyond which the responsive switch actuates and an output signal is generated should be predetermined at a value which corresponds to the loosening of the fastener beyond an acceptable level. For a pressure responsive switch, the threshold value of pressure may be above the pressure level expected at the switch when the fastener is tightened to the required degree, in the case that the loosening of the fastener brings about an increase in the pressure at the switch. Conversely, the threshold value may be below the pressure level expected for the correct level of tension in the fastener, in the case that the loosening of the fastener brings about a decrease in the pressure at the switch.
A certain degree of loosening will be likely in the majority of the fasteners during the normal use of a wind turbine and it would be undesirable for the system to be activated in response to small degrees of loosening which do not pose a risk. For a pressure responsive switch, the threshold value should preferably therefore be selected at above a nominal or averaged level sufficiently removed from the pressure expected when the fastener is at correct tension, so that the output signal is only generated to indicate a fastener that has been loosened to the point where it needs to be re-tightened. Similarly, for a displacement responsive switch, the threshold value should preferably be selected such that only displacements of a certain size will cause the switch to actuate. The specific threshold value for any given system is likely to depend upon the type of fastener and/or the position of the fastener on the wind turbine blade.
By "output device" is meant any device that can provide an output signal upon actuation of the responsive switch to act as a warning signal or alarm, which alerts a controller, whether it be a person or a machine, to the presence of the loosened fastener. This enables the fastener to be re-tightened or replaced before it loosens any further and before it poses any risk. The output device is arranged in electrical connection with the responsive switch so that it is activated when the switch is actuated and the circuit containing the switch and the output device is closed.
The output signal provided by the output device may be any type of signal which can be detected by the controller. Preferably, the output device is a device for providing an electromagnetic output signal or an electrical output signal.
In particularly preferred embodiments of the present invention, the sensor system includes a light emitting output device, such as a light emitting diode (LED), which is in electrical connection with the responsive switch. The light emitting device is activated, or switched on when the switch is actuated and lights up to indicate that the associated fastener has become loose.
Preferably, the light emitting device is mounted on the wind turbine proximate the fastener. This enables the location of the loosened fastener on the wind turbine to be readily identified so that the fastener can be efficiently found and replaced or re-tightened to the correct tension. This is particularly helpful in view of the large number of fasteners used in a wind turbine and will increase the efficiency of the tightening process.
In addition or as an alternative to the provision of a light emitting device for providing a visual warning signal of the loosened fastener, the sensor system may include an output device for transmitting an electrical or electromagnetic output signal to a monitoring unit upon actuation of the responsive switch. Preferably, the sensor system according to the present invention includes a suitable monitoring unit, which may be mounted on, within, or proximate the wind turbine, or at a remote location. Upon receiving the output signal, the monitoring unit will generate an alarm record, to warn of the presence of a loosened or broken fastener on the wind turbine, so that the necessary actions can be taken accordingly.
A suitable output device for transmitting an electrical output signal may simply be electrical wiring or cabling connecting a circuit including the responsive switch to a monitoring unit within the turbine, or proximate the turbine. Upon actuation, the responsive switch will close the circuit and the resultant electrical current will be transmitted around the circuit and along the wiring or cabling to the monitoring unit. This type of device is particularly suitable for monitoring the fasteners on the stationary components of the wind turbine, such as the tower.
A suitable output device for transmitting an electromagnetic output signal may be, for example, a radio transmitter. Since this type of transmitter is able to transmit the output signal wirelessly, it is particularly suitable for monitoring the fasteners on the moving components of the wind turbine, such as the fasteners on the wind turbine blades, or the fasteners for connecting the blades to the hub. Furthermore, the use of a wireless transmitter allows the use of a remote monitoring unit, which is located in a different place to the wind turbine.
The system may include two or more output devices which may provide output signals of a different type to each other. For example, it may be advantageous for the system to include both a light emitting device and a device for providing an electrical or electromagnetic output signal, since this provides both an alarm record and a visual indicator of the position of the loosened fastener.
The responsive switch and output device may be coupled together in a single sensor component in order to facilitate the mounting and handling of the sensor system components.
For example, a combined tactile switch and light emitting diode may be employed.
The responsive switch and output device may be mounted on the surface of the wind turbine by any suitable means known to the skilled person. The sensor system is preferably mounted so that there is minimum interference with the normal functioning of the wind turbine and in particular, so that the presence of the sensor system does not negatively impact the efficiency of the wind turbine.
In the sensor system of the present invention, the responsive switch and output device are in connection with a voltage source which provides the necessary voltage to activate the output device upon actuation of the switch. Any suitable voltage source may be employed, for example, a battery. The voltage source may be an alternating current (AC) source or a direct current (DC) source. The responsive switch and output device are connected to the voltage source by means of connections such as wiring or cables.
The sensor system according to the present invention is suitable for monitoring fasteners of many different types. In one particular embodiment of the present invention, a sensor system is provided for use in association with a nut and bolt fastener. Conventionally, the fasteners used on wind turbines are nut and bolt fasteners, comprising a bolt with a threaded shaft having a head at one end, and a nut which in use is screwed onto the threaded shaft in order to tighten the bolt. Typically, a washer will also be provided between the nut and the surface of the wind turbine. The nut and bolt fastener is tightened through the application of torque to the nut, as is well known. As the applied torque increases and the nut tightens on the bolt, the tension in the bolt increases. In this embodiment, the responsive switch is operatively connected to the nut such that the pressure or displacement detected at the switch varies as a function of the tension in the bolt and therefore also as a function of the tightness of the nut on the bolt.
The responsive switch may be arranged such that the pressure or displacement detected at the switch increases or decreases as the nut loosens. This will depend upon the connection between the responsive switch and the nut.
The responsive switch may be in direct connection with the nut such that the nut directly exerts a mechanical pressure on the switch. For example, a pressure responsive switch may be arranged above the nut such that as the nut loosens, the force exerted by the nut on the switch increases. Once the force, or pressure, at the pressure responsive switch increases above the threshold value, the switch will actuate and an output signal will be generated. In another example, a displacement responsive switch may be arranged above the nut such that the displacement of the nut as it loosens causes a mechanical pressure to be exerted on the switch. Once the displacement reaches the threshold level, the switch will actuate and the output signal will be generated.
Alternatively, the responsive switch may be in indirect connection with the nut via an intermediate component. With a pressure responsive switch, the loosening of the nut causes a change in the force or pressure exerted on the switch by the intermediate component, rather than the nut itself. With a displacement responsive switch, the loosening of the nut causes a displacement of the intermediate component. For example, in one preferred example of the present invention, the sensor system further comprises a plate mounted between the nut and the surface of the wind turbine, or between the nut and the washer, if a washer is present. With this arrangement, the responsive switch may be mounted between the plate and the wind turbine surface, adjacent or proximate the fastener.
The plate may be spring mounted, or connected in some other way to the nut such that the pressure exerted by the plate on the switch, or its displacement, varies as a function of the tension in the bolt, and therefore the tightness of the nut. For example, the plate and a pressure responsive switch may be mounted such that as the nut loosens and moves away from the plate and the wind turbine surface the plate in turn lifts away from the switch and the pressure exerted on the switch by the plate decreases. Once the pressure decreases below a threshold value, the switch will be actuated and an output signal generated by the at least one output device.
According to a second aspect of the present invention there is provided a wind turbine sensor system for monitoring a plurality of fasteners on a wind turbine in order to detect the loosening of one or more of the fasteners, the system comprising: a plurality of pressure responsive switches, each switch being operatively mounted on the wind turbine and operatively connected to one of the fasteners such that the pressure at the switch varies as a function of the tension of the corresponding fastener, wherein the switch is adapted to actuate when the pressure reaches a threshold value as a result of the loosening of the corresponding fastener; and at least one output device for providing an output signal when one or more of the fasteners is loosened, wherein the at least one output device is operatively connected to the plurality of pressure responsive switches such that it is activated to provide an output signal upon actuation of one or more of the switches.
According to a second aspect of the present invention there is also provided a wind turbine sensor system for monitoring a plurality of fasteners on a wind turbine in order to detect the loosening of one or more of the fasteners, the system comprising: a plurality of displacement responsive switches, each switch being operatively mounted on the wind turbine and operatively connected to one of the fasteners such that a displacement detected at the switch varies as a function of the tension of the corresponding fastener, wherein the switch is adapted to actuate when the displacement reaches a threshold value as a result of the loosening of the corresponding fastener; and at least one output device for providing an output signal when one or more of the fasteners is loosened, wherein the at least one output device is operatively connected to the plurality of displacement responsive switches such that it is activated to provide an output signal upon actuation of one or more of the switches.
In addition to providing all of the same advantages provided by the first aspect of the present invention, as described above, the sensor system of the second aspect of the invention provides for the first time a single system for concurrently monitoring all of the fasteners in a particular region of the wind turbine, for example, all of the fasteners connecting one of the blades to the hub. The system requires relatively simple circuitry and can readily be adapted to monitor any number of fasteners in a given group, in any given configuration. Installation and use of the system according to the invention requires little, if any, specialist skills or equipment.
Each of the individual responsive switches and output devices of the sensor system of the second aspect of the invention may be of the same form and construction as the switches and output devices of the sensor system of the first aspect of the present invention, described above. The sensor system of the second invention may be connected to a monitoring unit as described above and will function in substantially the same way.
Preferably, the plurality of responsive switches are electrically connected to each other in parallel, such that they can be connected in a single circuit with a single voltage source.
When connected in this way, the individual responsive switches and their associated output devices can function substantially independently of one another, since each switch is effectively within its own electrical circuit.
Preferably, the at least one output device includes a plurality of light emitting devices, each light emitting device being operatively connected to one of the plurality of fasteners and mounted on the wind turbine proximate that fastener, as described above in relation to the first aspect of the invention. Particularly preferably, a light emitting device is incorporated into each of the responsive switches and the combined pairs of switches and light emitting devices are connected in parallel with each other. This enables each of the pairs of switches and light emitting devices to function independently from each other.
The sensor systems of the first and second aspects of the present invention are specifically adapted for use on wind turbines and are preferably mounted on a wind turbine and arranged to monitor one or more of the fasteners connecting two components of the wind turbine together.
According to a third aspect of the present invention there is provided a wind turbine comprising a sensor system according to the first or second aspect of the invention, as described above.
According to a fourth aspect of the present invention there is provided a method for monitoring a fastener on a wind turbine in order to detect the loosening of the fastener, the method comprising: (a) mounting a pressure or displacement responsive switch on a wind turbine and connecting the switch to the fastener such that the pressure at the switch or a displacement detected at the switch varies as a function of the tension of the fastener, wherein the switch is adapted to actuate when the pressure or displacement reaches a threshold value as a result of the loosening of the fastener; and (b) connecting the pressure or displacement responsive switch to at least one output device such that the at least one output device is activated to provide an output signal upon actuation of the switch.
The method according to the invention employs a sensor system as described above.
Preferably, the step (b) of the method according to the invention includes the step of connecting the responsive switch to a light emitting device proximate the fastener, wherein the light emitting device is activated to emit light upon actuation of the switch such that the position of the loosened fastener can be identified.
Alternatively or in addition, step (b) includes the step of connecting the responsive switch is connected to a means for emitting an electrical or electromagnetic output signal upon actuation of the switch and the method further comprises the step of connecting the means for emitting an electrical or electromagnetic output signal to a monitoring unit. Suitable means for these purposes are described above.
According to a fifth aspect of the present invention there is provided use of a pressure or displacement responsive switch for monitoring a fastener on a wind turbine in order to detect the loosening of the fastener. This use has been described in detail above.
The invention will now be further described by means of example only with reference to the following drawings in which: Figure 1 shows a wind turbine with three blades; Figure 2 is an electrical circuit diagram of the sensor system incorporated in the wind turbine of Figure 1; and Figure 3 is a schematic diagram of a fastener from the wind turbine of Figure 1 and a part of the sensor system according to the present invention for monitoring the fastener.
Figure 1 illustrates a wind turbine 1 comprising a wind turbine tower 2 on which a wind turbine nacelle 3 is mounted. A wind turbine rotor 4 comprising at least one wind turbine blade is mounted on a hub 6. The hub 6 is connected to the nacelle 3 through a low speed shaft (not shown) extending from the nacelle front. The wind turbine illustrated in Figure 1 may be a small model intended for domestic or light utility usage, or may be a large model, such as those that are suitable for use in large scale electricity generation on a wind farm, for example. In the latter case, the diameter of the blades could be as large as 100 metres or greater.
Each of the blades 5 of the wind turbine 1 shown in Figure 1 is connected to the hub 6 by means of a group of nut and bolt fasteners 10 extending in a line, or loop around the blade 5.
The fasteners 10 are all of a conventional nut and bolt construction. Each blade 5 incorporates a sensor system 12 according to the invention for concurrently monitoring the loop of nut and bolt fasteners 10 connecting the blade to the hub in order to detect the loosening of any of the individual fasteners 10.
A simplified circuit diagram of the sensor system 12 is shown in Figure 2. The sensor system 12 comprises an electrical circuit including a plurality of pressure sensors 14, each comprising a pressure responsive switch 16 coupled to a light emitting diode (LED) 18. The pressure sensors 14 are connected together in parallel, with a single voltage supply 20. The total number of pressure sensors 14 in the sensor system is less than or equal to the total number of fasteners in the loop being monitored by the system arid each sensor 14 is associated with one of the fasteners 10 to detect the loosening of that particular fastener.
The sensor system 12 additionally includes a radio transmitter (not shown) in electrical connection with all of the switches 16 so that the transmitter is activated to transmit an output radio signal to a remote monitoring unit when one of the switches is actuated. Upon receiving the output signal, the monitoring unit will generate an alarm record to indicate the presence of a loosened fastener, so that a maintenance unit can be sent to replace or re-tighten the fastener.
As can be seen in Figure 3, each fastener 10 comprises a threaded bolt 22 which has been inserted in a hole drilled through the blade 5 and hub 6 at the position of connection, such that the end of the bolt 22 extends above the surface of the wind turbine blade 5. A washer 24 and nut 26 are threaded onto the bolt in a conventional manner. Figure 2 shows the nut 26 in its tightened position, against the surface of the wind turbine blade 5.
A spring mounted plate 28 is arranged between the nut 26 and the washer 24 and extends outwardly from the fastener 10 in at least one direction to create a space between the plate 28 and the wind turbine blade surface, adjacent the fastener 10. The pressure sensor 14 for monitoring the fastener 10 is mounted on the blade surface in this space underneath the plate 28, so that the plate 28 is in contact with the pressure sensor 14 when the nut 26 is fully tightened. The LED 18 is positioned slightly away from the plate 28 so that it is not obscured by the plate 28 or the fastener 10 and is therefore clearly visible when lit.
During use of the turbine 1, if the nut 26 moves away from the jointed surface as a result of self-loosening or elongation of the bolt, the pressure exerted by the plate 28 on the pressure sensor 14 will decrease. The pressure responsive switch 16 is adapted to have a threshold pressure value below the expected value of pressure or displacement at the switch 16 when the nut 26 is fully tightened. If the nut 26 continues to move away from the surface and the pressure exerted by the plate 28 on the switch 16 falls below the threshold value, the switch 16 will actuate and close the electrical circuit containing the switch 16, the LED 18 and the voltage supply 20. As a result, the LED 18 will be turned on to indicate the position of the loosened fastener 10 and a radio signal will be sent from the transmitter to the remote monitoring unit to issue a warning signal that the fastener requires tightening.
It will be appreciated that although the system shown in the figures and described above employs a plurality of pressure sensors, it could alternatively or in addition employ one or more displacement sensors, which detect the displacement of the plate or the nut. It will also be appreciated that although in the system shown in the figures and described above the responsive sensors are mounted underneath a plate, in other embodiments, the responsive sensors could be mounted in other positions relative to the fastener, for example, above the nut so that the nut acts directly on the sensor.

Claims (19)

  1. CLAIMS1. A sensor system for detecting the loosening of a fastener on a wind turbine, the system comprising: a pressure or displacement responsive switch operatively mounted on the wind turbine and connected to the fastener such that the pressure at the switch or a displacement detected at the switch varies as a function of the tension of the fastener, wherein the responsive switch is adapted to actuate when the pressure or displacement reaches a threshold value as a result of the loosening of the fastener; and at least one output device for providing an output signal when the fastener is loosened, wherein the at least one output device is operatively connected to the pressure or displacement responsive switch such that it is activated to provide the output signal upon actuation of the switch.
  2. 2. A sensor system according to claim 1 wherein the at least one output device comprises a light emitting device operatively coupled to the responsive switch such that it is activated to emit light upon actuation of the switch.
  3. 3. A sensor system according to claim 2 wherein the light emitting device is mounted on the wind turbine proximate the fastener.
  4. 4. A sensor system according to any preceding claim for detecting the loosening of a nut and bolt fastener, wherein the responsive switch is operatively connected to the nut such that the pressure or displacement detected at the switch varies as a function of the tension in the bolt.
  5. 5. A sensor system according to claim 4 further comprising a plate operatively mounted between the nut and the surface of the wind turbine, wherein the responsive switch is operatively mounted beneath the plate and wherein the plate exerts a mechanical pressure or displacement on the switch which varies as a function of the tension in the bolt.
  6. 6. A sensor system according to any preceding claim wherein the responsive switch comprises a thin film pressure sensor or miniature displacement sensor.
  7. 7. A sensor system for monitoring a plurality of fasteners on a wind turbine blade in order to detect the loosening of any of the fasteners, the system comprising: a plurality of pressure or displacement responsive switches, each responsive switch being operatively mounted on the wind turbine and operatively connected to one of the fasteners such that the pressure at the switch or a displacement detected at the switch varies as a function of the tension of the corresponding fastener, wherein the switch is adapted to actuate when the pressure or displacement passes a threshold value as a result of the loosening of the corresponding fastener; and at least one output device for providing an output signal when one or more of the fasteners is loosened, wherein the at least one output device is operatively connected to the plurality of responsive switches such that it is activated to provide an output signal upon actuation of one or more of the switches.
  8. 8. A system according to claim 7 wherein the plurality of responsive switches are electrically connected to each other in parallel.
  9. 9. A system according to claim 7 or 8 wherein the at least one output device includes a plurality of light emitting devices, each light emitting device being operatively connected to one of the plurality of fasteners and mounted on the wind turbine proximate that fastener.
  10. 10. A sensor system according to any preceding claim further comprising a monitoring unit for detecting the presence of a loosened fastener, wherein the monitoring unit is operatively connected to the at least one output device for receiving the output signal therefrom.
  11. 11. A sensor system according to claim 10 wherein the at least one output device comprises means for transmitting an electrical or electromagnetic output signal to the monitoring unit upon actuation of the switch connected to the output device.
  12. 12. A sensor system according to claim 11 wherein the means for transmitting an electrical output signal comprises a wireless transmitter for transmitting the output signal to the monitoring unit.
  13. 13. A sensor system according to claim 12 wherein the wireless transmitter is a radio transmitter.
  14. 14. A wind turbine comprising a sensor system according to any preceding claim for detecting the loosening of one or more fasteners connecting two components of the wind turbine to each other.
  15. 15. A method for monitoring a fastener on a wind turbine in order to detect the loosening of the fastener, the method comprising: (a) mounting a pressure or displacement responsive switch on a wind turbine and connecting the switch to the fastener such that the pressure or displacement detected at the switch varies as a function of the tension of the fastener, wherein the switch is adapted to actuate when the pressure decreases below a threshold value as a result of the loosening of the fastener; and (b) connecting the responsive switch to at least one output device such that the at least one output device is activated to provide an output signal upon actuation of the switch.
  16. 16. A method according to claim 15 wherein step (b) includes the step of connecting the responsive switch to a light emitting device proximate the fastener, wherein the light emitting device is activated to emit light upon actuation of the switch such that the position of the loosened fastener can be identified.
  17. 17. A method according to claim 15 or 16 wherein step (b) includes the step of connecting the responsive switch to a means for emitting an electrical or electromagnetic output signal upon actuation of the switch and wherein the method further comprises the step of connecting the means for emithng an electrical or electromagnetic output signal to a monitoring unit for receiving the output signal.
  18. 18. Use of a pressure or displacement responsive switch for monitoring a fastener on a wind turbine in order to detect the loosening of the fastener.
  19. 19. Use according to claim 18 wherein the responsive switch is operatively mounted on the wind turbine and connected to the fastener such that the pressure or displacement detected at the switch varies as a function of the tension of the fastener, wherein the switch is adapted to actuate when the pressure or displacement goes beyond a threshold value as a result of the loosening of the fastener and wherein the switch is operatively connected to at least one output device for providing an output signal when the fastener is loosened, wherein the at least one output device is activated to provide the output signal upon actuation of the switch.
GB0815973A 2008-09-02 2008-09-02 Detecting loosening of wind turbine fastener using pressure or displacement responsive switch Withdrawn GB2463081A (en)

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CN111828264A (en) * 2020-08-04 2020-10-27 广州发展新能源股份有限公司 Bolt looseness monitoring device
CN114541733B (en) * 2022-02-28 2023-07-14 重庆建工集团股份有限公司 Pre-assembled operating platform
CN115331398B (en) * 2022-07-05 2023-05-16 中国长江电力股份有限公司 Intelligent monitoring device and method for volute inlet bolt of hydroelectric generating set

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CN104142229A (en) * 2013-05-10 2014-11-12 中科风电(北京)有限公司 Online wind turbine generator system flange bolt monitoring and failure diagnosis system
WO2016042513A1 (en) * 2014-09-18 2016-03-24 Maxion Wheels Germany Holding Gmbh Nut, in particular wheel or axle nut, washer, control device for wheel or axle nuts in vehicles and vehicle provided therewith
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CN105986963B (en) * 2015-02-11 2019-08-20 赤峰华源新力科技有限公司 The connection bolt looseness of Wind turbines monitors system
EP3467303A1 (en) * 2017-09-20 2019-04-10 Senvion GmbH Method and system for monitoring a flange connection of a wind energy plant
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