EP3673175A1

EP3673175A1 - Method for increasing the yield of a wind farm under icing conditions

Info

Publication number: EP3673175A1
Application number: EP18756198.0A
Authority: EP
Inventors: Peter STÄHLER
Original assignee: fos4X GmbH
Current assignee: fos4X GmbH
Priority date: 2017-08-25
Filing date: 2018-08-14
Publication date: 2020-07-01
Also published as: US20200217300A1; US11174841B2; CN111033034A; DE102017119540A1; WO2019038138A1

Abstract

The invention relates to a method for monitoring a wind farm. The method includes determining a first ice mass on a first wind turbine of the wind farm; determining at least one second ice mass on at least one second wind turbine of the wind farm; comparing a first ice mass with a second ice mass and determining a primary wind turbine, which serves as a reference, and at least one secondary wind turbine from the group of the first wind turbine and the at least one second wind turbine; switching off the at least one secondary wind turbine on the basis of a first ice mass from the primary wind turbine; and switching on the at least one secondary wind turbine on the basis of a second ice mass from the primary wind turbine.

Description

METHOD FOR INCREASING EARNINGS OF A WIND FARM UNDER

iCING CONDITIONS

TECHNICAL AREA

Embodiments of the present disclosure relate to a method for monitoring a wind farm and a device for monitoring a wind farm by a method.

STATE OF THE ART

Rotor blades of wind turbines are exposed to the weather conditions of the environment unprotected. At certain locations, ice may be deposited on the rotor blades when the ambient temperature is low and the humidity or rainfall is high enough. With increasing size of the rotor blades of wind turbines increases their surface, so that the risk of attachment of ice, d. H. the formation of an ice accumulation on the rotor blades, increases.

Ice deposits on the one hand represent a potential danger to the environment of the wind turbine, since at a drop of ice accumulation - during operation or at rest of the system - the discarded pieces of ice can endanger persons and objects in the discharge radius. On the other hand, an unbalance of the rotor of the wind turbine can result especially in uneven accumulation of ice, which can lead to damage during operation of the wind turbine. Furthermore, a prolonged Eisanlagerung can lead to the stoppage of the entire system. This is usually associated with revenue losses and economic disadvantages.

It is known to evaluate data from a wind turbine to close at the risk of an already occurred accumulation of ice. DE 10 2005 016 524 A1 discloses a method for detecting ice on a wind turbine, in which both meteorological conditions that are associated with icing conditions are monitored, and also one or more physical, characteristic ones Sizes of the wind turbine to be monitored in operation, which suggest a mass change of the rotor blades of the wind turbine.

US 2012/0226485 Al describes a method for predicting the likelihood of formation or growth of ice on rotor blades of wind turbines. The procedure makes u.a. the historical measurement of meteorological data such as wind speed, temperature and relative humidity.

In wind farms in winter there are always icing events at e.g. Rotor blades of the individual wind turbines. Often, wind turbines in wind farms then have to be stopped. This leads to yield losses at the wind farm operators due to a reduced availability of the plants.

SUMMARY OF THE INVENTION

Embodiments of the present disclosure provide a method for monitoring a wind farm. Further, embodiments of the present disclosure provide an apparatus for monitoring according to the described method 10.

According to one embodiment, a method for monitoring a wind farm is specified, with determination of a first ice mass on a first wind turbine of the wind farm; Determining at least one second ice mass on at least one second wind turbine of the wind farm; Comparing a first ice mass with a second ice mass and determining a primary wind turbine serving as a reference and at least one secondary wind power plant from the group of the first wind power plant and the at least one second wind power plant; Turning off the at least one secondary wind turbine based on a first ice mass of the primary wind turbine; and turning on the at least one secondary wind turbine based on a second ice mass of the primary wind turbine.

According to a further embodiment, an apparatus of a wind farm is specified with a controller for controlling wind turbines of the wind farm. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are illustrated in the drawings and explained in more detail in the following description. In the drawings show:

Fig. 1 shows schematically a wind farm with by way of example three wind turbines according to embodiments described herein;

Fig. 2A shows schematically a part of a wind turbine with rotor blades and sensors according to embodiments described herein;

2B schematically shows a rotor blade of a wind turbine with a sensor according to embodiments described herein; FIG. 3 is a flowchart of a method according to embodiments described herein; FIG.

FIG. 4 is a flowchart of a method according to embodiments described herein; FIG.

Fig. 5 shows schematically a light guide with a fiber Bragg grating for use in sensors according to embodiments described herein;

Fig. 6 shows schematically a measurement setup for a fiber optic sensor according to embodiments described herein or for methods of monitoring according to embodiments described herein.

In the drawings, like reference characters designate like or functionally identical components or steps.

WAYS FOR CARRYING OUT THE INVENTION

[0019] In the following, more detailed reference will be made to various embodiments of the invention, one or more examples of which are illustrated in the drawings. The present invention finds application for increasing the availability of individual wind turbines of a wind farm and to minimize yield losses for the entire wind farm in the event of icing.

Fig. 1 shows a wind farm 10 exemplarily consisting of three wind turbines 200. The wind turbines 200 are, as shown in Fig. 1 by dashed lines, interconnected. The networking enables communication, for example real-time communication, between the individual wind turbines. The networking also allows common monitoring, control and / or regulation of wind turbines. In addition, the wind turbines can also be individually monitored, controlled and / or regulated. According to embodiments described herein, a wind farm may include two or more wind turbines, in particular five or more wind turbines, such as ten or more wind turbines.

The wind turbines 200, for example, the wind turbines of Fig. 1, in their entirety form the wind farm 10. The wind farm consists of at least two wind turbines. The close proximity of the wind turbines also allows the validation of similar environmental influences on wind turbines of the wind farm. Thus, the assumption can be made that similar effects on the wind farm's wind farms have a similar impact. The wind farm 10 may consist of a first wind turbine and at least a second wind turbine according to one embodiment. From the group of the first wind turbine and the at least one second wind turbine, a primary wind turbine can be determined. Plants from this group that are not designated as primary are secondary wind turbines. Fig. 2A shows by way of example a wind turbine 200 of a wind farm, to which the method described herein can be used. The wind turbine 200 includes a tower 40 and a nacelle 42. On the nacelle 42, the rotor is mounted. The rotor includes a hub 44 to which the rotor blades 100 are attached. According to typical embodiments, the rotor has at least 2 rotor blades, in particular 3 rotor blades. During operation of the wind turbine rotates the rotor, ie the Hub with the rotor blades around an axis. In this case, a generator is driven to generate electricity. As shown in FIG. 2A, at least one sensor 110 is provided in a rotor blade 100. The sensor is connected to a signal line with an evaluation unit 114. The evaluation unit 114 supplies a signal to a control and / or regulation 50 of the wind turbine 200.

In the region of the rotor blade tip of the rotor blades 100, an ice extension 1 is shown schematically. In the rotor blade, by means of the sensor 110, e.g. Detects vibrations or accelerations, which can be configured according to described embodiments, as a vibration sensor or acceleration sensor. The sensor 110 may be e.g. to act electrical and / or fiber optic sensors. The sensors may be configured to measure a first ice mass and at least one second ice mass.

Fig. 2B shows a rotor blade 100 of a wind turbine. The rotor blade 100 has an axis 101 along its longitudinal extent. The length 105 of the rotor blade extends from the blade flange 102 to the blade tip 104. According to embodiments described herein, a sensor 110 is located in an axial or radial region, that is, a region along the axis 101.

It is often desirable to allow direct monitoring of the wind farm so that icing of the rotor blades of one or more wind turbines can be reacted without delay. Furthermore, autonomous monitoring and control is advantageous.

According to one embodiment, plants may be a primary wind turbine or secondary wind turbines. A primary wind turbine is a reference plant. In the event of icing, ice u.a. attach to the rotor blades 100. In plants, the addition of ice or the ice batch can be measured. The amount or volume of ice attached may vary between installations, within the limits set by proximity.

Ice accumulation, as used herein, refers to an increase in ice mass on a rotor blade over time. Furthermore, a Decrease in ice is present. An increase of an ice mass may be an accumulation or increase of an ice mass, so be positive, or may be a decrease of an ice mass, so be negative. A icing case, as used herein, refers to the occurrence of ice accumulation on at least one wind turbine of a wind farm. In the event of icing, the ice mass, which attaches to the rotor blades of wind turbines in a period of time, can be determined. A determination of an ice mass presupposes the measurement of a suitable measured quantity. The measurement is carried out with the aid of sensors 110. The measured variable can be converted by transformation into a system variable S. The system size S is determined indirectly. For example, a natural vibration of a rotor blade can be measured

The system size S is also related to the mass of the rotor blade. Alternatively or additionally, the system size S is related to the mass of an ice accumulation on the rotor blade. Typically, the system size S is obtained from measurement data of vibration or acceleration measurements in or on one or more rotor blades. In embodiments, the measured quantity is measured over the course of a detection period, preferably by measuring vibrations or accelerations over the course of the detection period T. The measurement takes place on or in the rotor blade.

The system size S is derived from the measurement data, preferably by natural frequency analysis from the measurement data of the vibration or acceleration measurements. The system size S is indicative of the mass of the respective rotor blade or of the respective rotor blades and / or the ice-mass of the respective rotor blade or of the respective rotor blades. The documentation of the measured data and its transformation can be recorded in an ice mass diagram or in an ice mass curve. In embodiments, the system size S is proportional to the total mass of the rotor blade and / or proportional to an additional mass coating of the rotor blade. An additional mass coating of the rotor blade is such a mass coating, which is added to the net mass of the rotor blade. Typically, the system size is proportional to the ice mass. The measurement of the ice accumulation on a rotor blade takes place in the detection period T by sensors 110. The measurement data can be recorded continuously or in suitable sampling intervals at the wind turbine during a period of several days and / or hours, the detection period T such a period can correspond.

From a diagram as described above, several information on the system size S can be read. Thus, for example, the ice mass can be detected at a specific time of the detection period T. Alternatively, between two times ti and t _{2 of} the detection period T, a rise of an ice mass in a diagram can be determined.

An increase in ice mass, as used herein, may take on positive and negative values. An increase of an ice mass gives information about the change of the amount of ice accumulation at a certain time t _x or in a certain detection period T. Obtained values can enable the comparison of data of different wind turbines in a wind farm.

According to embodiments described herein, which may be combined with other embodiments, the course of the ice mass curves may be monitored in the park. A plant can experience a relevant increase in ice mass (control over increase in ice mass curves). For example, the plant with the largest increase can be defined as the primary wind turbine. Additionally or alternatively, the plant with the largest ice mass can be defined as the primary wind turbine. The primary wind turbine can serve as a reference. In the event of icing, the system can be monitored for the parameter "Increase in the ice mass in running systems." Alternatively or additionally, the system can be monitored in the event of icing on the parameter "Maximum / highest point of icing". Other installations in the wind farm, eg the secondary wind turbines, can be switched off preventively if a threshold value of the primary wind turbine is exceeded. The disconnected systems can remain in this state until released. After reaching a plateau of the ice mass curve of, for example, the primary system, the remaining systems can be re-enabled for normal operation. Due to the early stop, the shutdown systems typically developed less ice buildup. Most plants of the wind farm can be available again for energy generation well in front of the primary plant where an ice mass plateau is determined.

3 shows a flow diagram of a method 1000 according to embodiments described here for monitoring the wind farm 10. In a step 1100 of the method, a first ice mass is determined at a first wind power plant of the wind farm. In addition, at least one second ice mass is determined on at least one second wind turbine of the wind farm. It can determine the ice masses of the group of wind turbines of a wind farm. Alternatively, the slopes of ice sheets of the group of wind turbines can be determined. Actual ice masses may be detected in accordance with embodiments described herein. Ice masses can be determined from measurement data measured on or in the rotor blade. This can e.g. done with the aid of an ice mass curve or an ice mass diagram. The information from the group of wind turbines describes, as described above, a behavior of the ice mass over a period in which the measured values are recorded.

In a step 1200 of the method, a first ice mass of the first wind turbine is compared with a second ice mass of the at least one second wind turbine. It can be compared ice sheets of wind turbines of a wind farm. Alternatively, increases in an ice mass of wind turbines in a wind farm can be compared. The wind turbine, which records the largest ice mass, for example at a comparison time t _v , is determined to be the primary wind turbine. Alternatively, the wind turbine that registers the largest increase in ice masses, for example, at a comparison time ty, is determined to be the primary wind turbine. Facilities that are not designated as the primary facility become secondary wind turbines. [0040] The comparison of the time t _v, as used herein, a point in time can be, for example shortly after the first occurrence of icing case of a wind turbine of a wind park. The comparison time ty can be set appropriately for a wind farm. In a step 1300 of the method, the at least one secondary wind turbine is shut down based on a first ice mass of the primary wind turbine. For example, the ice mass of the primary plant may reach a first threshold, eg, a threshold S _A. The primary system undergoes a first ice alert. For example, an ice mass of the primary plant will not exceed an upper threshold, So, which would cause the primary plant to shut down. The primary wind turbine remains in operation and continues to serve as a reference. Secondary wind turbines may be shut down based on the primary wind turbine, for example when the primary plant reaches the threshold S _A. Wind turbines that are not determined to be the reference installation can be additionally or alternatively individually switched off. An ice alarm, ie a first ice alarm, for switching off secondary systems can be generated when a first switch-off threshold in the gradient of ice formation, eg in the ice formation of the primary system, is exceeded. The first ice alarm can be generated by exceeding a first ice mass threshold, in particular at the primary plant. A second ice alert on the primary system may be a "normal" ice alert that also stops the installation of the normal ice alert itself.

A condition for turning off the wind turbines by an amount of ice attached to the operation can be set by threshold values. Ice masses of wind farm facilities can reach an upper threshold. An ice mass of a primary wind turbine may also reach a threshold S _A.

For example, a defined upper limit to the amount of ice attached, e.g. As the mass and / or the volume of ice attached, beyond which safe operation of the wind turbine is no longer permitted or no longer possible. An upper threshold value Thus, for example, can be determined empirically, or it can be predetermined by provisions regarding the reliability of the wind turbine. At the threshold So an ice alarm is triggered. Measurements on or in the rotor blade can also be made on equipment that is not in operation. Furthermore, additionally or alternatively, threshold values for the rise of ice masses can also be used. [0044] In accordance with embodiments described herein, threshold values are referred to. In general, signals for switching off or switching on can be determined from the measured data at the wind power plants, in particular the primary wind power plant. Thresholds can be set for different parameters. For example, thresholds for meteorological data such as temperature combined with humidity may be present. Thresholds for ice detection may also result from performance curves of a wind turbine. However, threshold values for rotor blade loads which are measured, for example, at a blade root, for example with strain sensors, may also exist, for example. Furthermore, a further condition for shutting down the wind turbines may be determined by an amount of ice attached to the operation by a threshold S _A suitable for the system size S. The threshold S _A is, for example, a defined limit for an amount of ice attached, e.g. As the mass and / or the volume of attached ice, which is exceeded by switching off the affected wind turbines with high yield losses of the wind farm is to be expected. The threshold value S _A is less than the threshold value So. The threshold value S _A can be determined empirically, for example.

Upon reaching the upper threshold So the plants can experience a second ice alarm. Upon reaching the threshold value S _A , the primary system may experience a first ice alarm. Upon reaching the first threshold value S _A , the primary system can cause a signal for switching off the at least one secondary wind turbine.

An ice alarm, as used herein, may be created by exceeding a threshold at a primary or secondary wind turbine of the wind farm. An ice alarm can be triggered if one of the So or S _A thresholds or both is exceeded in a plant. A first ice alarm can be triggered if the threshold S _{A is} exceeded. A second ice alarm, triggered by exceeding the So threshold, shuts down the system where the ice alarm was triggered. A first ice alarm, triggered by the exceeding of the threshold value S _A , triggers a signal to switch off another system, at which no ice alarm is triggered at the same time. Measurements of the ice mass, the Eisanasatzes or Eisanlagerung can be performed with the system off.

Turning off or stopping a plant as used herein is primarily to be understood as stopping the rotor blades. The measurements on or in the rotor blades can continue despite stationary rotor blades.

In a step 1400 of the method, the at least one secondary wind turbine is switched on based on a second ice mass or increase in ice mass (e.g., ice mass plateau, d-h rise = 0) of the primary wind turbine. A second ice mass of a primary wind turbine can reach a plateau phase. In a plateau phase or a plateau, the ice mass on the rotor blade does not rise. The ice mass on a rotor blade is constant. Alternatively, the second ice mass at the primary plant may decrease or the increase in ice mass at a primary plant may be negative. If a plateau of the ice mass is reached or if the increase in the ice mass is negative, wind turbines can be switched on. For example, the secondary wind turbines can be turned on.

Wind turbines that are not determined to reference plant can be turned on. Wind turbines that are not determined to be the reference system can alternatively be switched on individually. The group of switched-on wind turbines can be operated in normal mode. A plant as used herein is in normal or normal operation when the parameters for operating the plant are in accordance with the usual parameters. It is possible to operate wind turbines that are not specified for the reference system in normal mode. The primary wind turbine can be switched off. Regeneration of the primary plant can be done until the primary plant is re-enabled. Regenerating the primary plant can be assisted, e.g. by actively removing an ice batch which in turn is e.g. can be done by a sheet heating or a mechanical "shaking off" of the ice.Through the support of the regeneration this can be accelerated.

It can be deduced from historical parking data that the icing event at a wind power plant lasts the longer the longer the plant is at the beginning of the wind turbine Icing case was in operation. The sooner the systems can be switched off in case of icing, the lower the overall failure, as an earlier restart can be guaranteed.

An early switch on after icing of a wind farm can significantly increase the total energy yield of the wind farm under icing conditions. The negative result is the downtime of systems until the reference system is switched off. The additional yield results from the earlier start-up of plants with the exception of the reference plant.

Already formed ice mass can act in combination with the wind and temperature conditions of the plant during operation as a nucleus for the formation of further ice formation. Standing plants are also affected by icing, due to the lower ice accumulation, the icing event ends earlier. Since the secondary wind turbines have developed less ice accumulation due to the early stop, the majority of the secondary turbines are again available for energy generation well in front of the reference turbines.

FIG. 4 shows a flow chart of a method 1100 according to embodiments described herein.

In a step 1110 of the method, a first ice mass is determined at a first wind turbine of the wind farm. In addition, at least one second ice mass is determined on at least one second wind turbine of the wind farm. At the beginning of an icing in the wind farm, the ice mass curves of the systems in the park rise until one of the thresholds So or S _A or both is reached. With the aid of the measurements made by the sensor on or in the rotor blade, ice masses can be determined, for example as ice mass curves or ice mass diagrams. Alternatively or additionally, further sensors and / or data can be used to determine the ice mass. From the measurements, the ice masses and / or an increase of the ice masses between different plants can be compared at different comparison times ty and ty '. The data can also be compared over a whole detection period T. In a step 1210 of the method, a primary plant is determined. The wind turbines, which do not become the primary plant, become secondary wind turbines. The system with the steepest rise in the ice mass curve remains in normal mode and serves as a reference. When the threshold value S _A is reached, a first ice alarm is triggered on the primary system. Upon reaching the first ice alarm, for example, based on a threshold, for example, the threshold S _A, the primary system can cause a signal to shut down the at least one secondary wind turbine.

At the primary wind turbine, a second ice alarm can be triggered when exceeding a threshold So. The primary wind turbine can be switched off. The measurement of the ice mass can continue to take place at the primary wind turbine at wind speeds of more than 2-3 m / s. The measurement of the ice mass can take place over the entire duration of an icing. The measurement may be performed at intervals, e.g. at intervals during which wind speeds of at least 2-3 m / s prevail.

In a step 1310 of the method, the at least one secondary wind turbine is shut down based on a first ice mass of the primary wind turbine. The systems from the group of the first wind turbine and at least one second system are switched off. The secondary wind turbines can be switched off. The shutdown can be done, for example, when the ice mass of the primary system has reached the threshold value S _A , or if the primary system detects a first ice alarm. The shutdown can be done when a primary ice mass is determined at the primary wind turbine. A first ice mass can be determined at a time t _v . At time t _v , the threshold value S _{A of} a first ice mass on the primary wind turbine can be reached. Typically, a first ice mass at time ty and a rise of a first ice mass at threshold S _A , are positive. The primary wind turbine remains in normal mode. Typically, less ice builds up on switched off systems.

In a step 1410 of the method, the primary wind turbine is monitored. In addition, and the at least one secondary wind turbine can be monitored. It can be monitored an ice mass. It may be an increase in Ice mass to be monitored. The maximum or the peak of icing can be deduced. The ice mass or the rise of an ice mass can be monitored at the primary wind turbine. The ice mass or the rise of an ice mass may be monitored at different times and / or over a period of time. The ice mass or the rise of the ice mass may have a plateau. Alternatively, the ice batch may be negative. If the rise of an ice mass of the primary wind turbine remains constant over a certain period of time, the icing event on the primary wind turbine can be regarded as finished.

In a step 1510 of the method, the at least one secondary wind turbine is switched on based on an ice mass of the primary wind turbine. The switching on of the at least one secondary wind turbine can take place, for example, as soon as the second ice mass of the primary wind turbine or an increase in a second ice mass of the primary wind turbine reaches a plateau or becomes negative. If there is no further ice accumulation, secondary wind farm systems can be re-enabled for normal operation. An automatic change of the stopped plants into a normal operating mode can take place. The reference system is regenerated. The time to stop the reference system is typically only a few hours.

Typically, the earlier switching on the stopped systems takes half a day to several days before switching on the reference system after Regenration.

The described method can immediately restart insofar further icing in the wind farm take place. The wind turbine, which was determined in a previous icing to reference plant or primary wind turbine can be involved in a new process. For example, this can happen after regeneration is complete. Alternatively, the process can proceed based on the previous secondary plants, in particular if the previous primary plant still has a residue of ice accumulation. The method can also be nested. This is necessary if a new icing takes place during the decay of a first icing in the wind farm. The described method is then reapplied on the plants that were not designated for the reference plant in the previous process. Steps of the process can be fully automated. Another aspect of wind turbine monitoring that may be combined with other embodiments and aspects described herein, but that is also provided independently of other embodiments, aspects, and details, is a wind farm monitoring apparatus as described above Embodiments of the method, wherein the device comprises a controller. A controller can serve for networking of a first wind turbine of the wind farm with at least one second wind turbine of the wind farm for all wind turbines. The controller can be used for simultaneous and / or individual control of the wind turbines. The controller can also allow the fully automatic control and regulation of plants in a wind farm. The controller may be connected to one of the evaluation unit of a wind turbine. For example, the controller may perform the steps of one of the methods described herein by software and / or hardware.

Fig. 5 shows schematically an optical fiber with a fiber Bragg grating for use in sensors according to embodiments described herein.

FIG. 5 shows a sensor or fiber-optic sensor 510 integrated in an optical waveguide, which has a fiber Bragg grating 506. Although only a single fiber Bragg grating 506 is shown in FIG. 5, it should be understood that the present invention is not limited to data acquisition from a single fiber Bragg grating 506 but that along an optical fiber 212, a transmission fiber , a sensor fiber or an optical fiber, a plurality of fiber Bragg gratings 506 may be arranged.

Thus, Fig. 5 shows only a portion of an optical waveguide formed as a sensor fiber, optical fiber or light guide 212, which sensor fiber is sensitive to fiber elongation (see arrow 508). It should be noted that the term "optical" or "light" is intended to indicate a wavelength range in the electromagnetic spectrum, which may extend from the ultraviolet spectral range over the visible spectral range to the infrared spectral range. A center wavelength of the fiber Bragg grating 506, that is, a so-called Bragg wavelength λΒ, is obtained by the following equation. λΒ = 2 · nk · Λ.

Here, nk is the effective refractive index of the fundamental mode of the core of the optical fiber and Λ the spatial grating period (modulation period) of the fiber Bragg grating 506. A spectral width given by a half-width of the reflection response depends on the extension of the fiber Bragg grating 506 along the sensor fiber. The propagation of light within the sensor fiber or light guide 212 is thus dependent, for example, on forces, moments and mechanical stresses and temperatures at which the sensor fiber, i. E., By the action of the fiber Bragg grating 506. the optical fiber and in particular the fiber Bragg grating 506 are loaded within the sensor fiber.

As shown in FIG. 5, electromagnetic radiation 14 or primary light enters the optical fiber or light guide 212 from the left, wherein a portion of the electromagnetic radiation 14 is changed as a transmitted light 16 with an electromagnetic radiation 14 compared to the electromagnetic radiation 14 Wavelength profile emerges. Further, it is possible to receive reflected light 15 at the input end of the fiber (i.e., at the end where the electromagnetic radiation 14 is also irradiated), the reflected light 15 also having a modified wavelength distribution. The optical signal used for detection and evaluation may, according to the embodiments described herein, be provided by the reflected light, by the transmitted light, as well as a combination of the two.

In a case in which the electromagnetic radiation 14 or the primary light is irradiated in a wide spectral range, results in the transmitted light 16 at the location of the Bragg wavelength, a transmission minimum. In the reflected light arises at this point a reflection maximum. A detection and evaluation of the intensities of the transmission minimum or the reflection maximum, or of intensities in corresponding wavelength ranges generates a signal which can be evaluated with regard to the change in length of the optical fiber or the light guide 212 and thus provides information on forces or vibrations. FIG. 6 shows a typical measuring system for the evaluation of fiber optic and acceleration sensors. The system includes an electromagnetic radiation source 602, for example, a primary light source. The source serves to provide optical radiation with which at least one fiber-optic sensor element of a sensor, for example an acceleration sensor, can be irradiated. For this purpose, an optical transmission fiber or fiber 603 is provided between the primary light source 602 and a first fiber coupler 604. The fiber coupler couples the primary light into the optical fiber or light guide 212. The source 602 may include, for example, a broadband light source, a laser, a light emitting diode (LED), an SLD (superluminescent diode), an ASE (amplified spontaneous emission) light source. Light source) or an SOA (Semiconductor Optical Amplifier). For embodiments described herein, multiple sources of the same or different types (see above) may also be used.

The fiber optic sensor element 610, such as a fiber Bragg grating (FBG) or an optical resonator, is integrated into a sensor fiber or optically coupled to the sensor fiber. The reflected light from the fiber optic sensor elements is in turn passed through the fiber coupler 604, which directs the light via the transmission fiber 605, a beam splitter 606. The beam splitter 606 divides the reflected light for detection by means of a first detector 607 and a second detector 608. In this case, the signal detected on the second detector 608 is first filtered with an optical edge filter 609.

By the edge filter 609, a shift of the Bragg wavelength at the FBG or a wavelength change can be detected by the optical resonator. In general, a measuring system as shown in FIG. 6 may be provided without the beam splitter 606 and the detector 607, respectively. However, the detector 607 allows normalization of the acceleration sensor measurement signal with respect to other intensity fluctuations, such as source intensity variations 602, reflections at interfaces between individual fibers, or other intensity variations. This standardization improves the measuring accuracy and reduces the dependence of measuring systems on the length of the optical fibers provided between the evaluation unit and the fiber-optic sensor. In particular, when using multiple FBGs additional optical filter devices (not shown) for the filtering of the optical signal or secondary light can be used. An optical filter device 609 or additional optical filter devices may comprise an optical filter which is selected from the group consisting of a thin-film filter, a fiber Bragg grating, an LPG, an Arrayed Waveguide Grating (AWG), an echelle Grid, a grid array, a prism, an interferometer, and any combination thereof.

Although the present invention has been described above with reference to typical embodiments, it is not limited thereto, but modifiable in many ways. Also, the invention is not limited to the applications mentioned. It should also be noted at this point that the aspects and embodiments described herein may be reasonably combined, and that individual aspects may be omitted where appropriate and possible within the skill of the art. Modifications and additions to the aspects described herein will be apparent to those skilled in the art.

Claims

A method of monitoring a wind farm, comprising:

Determining a first ice mass at a first wind turbine of the wind farm;

Determining at least one second ice mass on at least one second wind turbine of the wind farm;

Comparing a first slope of the first ice mass with a second slope of the second ice mass and determining a primary wind turbine serving as a reference and at least one secondary wind turbine from the group of the first wind turbine and the at least one second wind turbine;

Turning off the at least one secondary wind turbine based on a measurement of the primary wind turbine; and

Turning on the at least one secondary wind turbine based on a measurement of the primary wind turbine.

2. The method of claim 1, wherein for determining the primary wind turbine, the primary wind turbine has a larger increase in an ice mass or a larger ice mass than the at least one secondary wind turbine.

3. The method according to any one of the preceding claims, wherein at the primary

Wind turbine a first ice alert is triggered. The method of claim 3, wherein the first ice alarm of the primary wind turbine causes a signal to shut down the at least one secondary wind turbine.

A method according to claim 4, wherein a second ice alarm is triggered, which causes a shutdown of the system, at which the second ice alarm is triggered.

Method according to one of the preceding claims, wherein the ice mass of the primary wind turbine is measured over the entire duration of an icing on the primary wind turbine.

Method according to one of claims 1 to 6, wherein the turning on the at least one secondary wind turbine takes place as soon as an ice mass of the primary wind turbine reaches a plateau or an increase in the ice mass of the primary wind turbine is negative.

Method according to one of claims 1 to 7, wherein the method restarts when another icing occurs, in particular wherein the reference system of the previous icing case is included insofar as the reference system is regenerated.

Method according to one of the preceding claims, wherein electrical and / or fiber optic sensors are used for a measurement of the first ice mass and at least the second ice mass. Apparatus for monitoring a wind farm, comprising: a controller for controlling wind turbines of the wind farm, performing steps according to any one of the methods of claims 1 to 9.