A measuring system and method for conductive lines in wind turbine blades

Abstract

The present invention discloses a measuring system and method for conductive wires in a wind turbine blade. The system is installed in a wind turbine. The system uses a discharge gap to measure the charge flow of the down conductor passing through each blade of the wind turbine and compares the measured values ​​of all blades of the wind turbine to monitor the connection status of the down conductor in the wind turbine blade in the entire blade. If a blade has a relatively small charge flow in normal operation, an alarm is generated to indicate a faulty down conductor. The solution provided by the present invention does not require changes or additions to the wiring in the blade itself, and the solution is simple in structure, low in cost, and easy to implement; that is, it is suitable for the production and manufacturing of blades, and can also be used as a solution for the modification of blades.

Description

Technical Field

[0001] The invention relates to wind power generation technology, in particular to a system installed in a wind power generator to monitor the state of a lightning protection down conductor in each blade. Background Art

[0002] Compared to the surrounding environment, wind turbine blades are very vulnerable to lightning strikes due to their high position. In order to control the discharge path of lightning strikes, lightning receptors are installed on the surface of most blades. The lightning receptors are connected to the down conductor inside the blade, which is connected to the nacelle and from there to the ground through the tower.

[0003] It is well known that mechanical or other environmental stresses can cause defects in the downconductor inside the blade, resulting in the downconductor cable separating between one or more lightning receptors along the length of the wind turbine blade. This can lead to an uncontrolled discharge path and severely increase the risk of blade damage in the event of a lightning strike.

[0004] Therefore, a detection scheme is needed to detect whether there is a breakpoint at any position of the lightning protection down conductor relative to the blade tip lightning arrester. Ideally, such a detection scheme should support online monitoring, that is, the measurement equipment used in the detection scheme should be fixedly installed on a single blade.

[0005] There are various methods in the prior art to measure whether a conductor (ie, a down conductor) is broken along its expected path.

[0006] (1) Typical solutions are simple resistance measurement and high-frequency (pulse) wave instrumentation, wherein the former requires the establishment of a conductive loop (such as can be seen in the patent application with publication number CN 105545615 A), while the latter requires complex equipment and the equipment cost is relatively high compared to the present invention.

[0007] (2) Detecting and measuring lightning discharges by measuring the charge of the air. For example, US Patent No. US 6061216 discloses a "lightning detection device and method"; this technology uses an antenna and amplifier configuration to receive electrostatic discharges generated by lightning and electrical noise to output an analog electrical signal representing the discharge. The analog signal is applied to a threshold detection circuit, which activates its output when the input signal rises above a predetermined level. Based on this, a computer or similar device checks the output to determine whether an event window is open. The pulses within the event window have event-related characteristics that can be used for comparison; if the characteristics of the pulse signal are related to a lightning event, an alarm signal is generated.

[0008] For example, US Pat. No. US9450392B2 discloses a method for detecting electric charge originating from lightning. The invention describes the measurement of electric charge from lightning passing through a down conductor system. The invention specifically relates to a detection device for a wind turbine, wherein the wind turbine comprises a down conductor system for conducting current induced by lightning, wherein the detection device comprises a charge measurement device for establishing a charge representation, wherein the charge representation represents the electric charge induced in the down conductor system by lightning, and wherein the detection device further comprises an estimator for estimating the degradation of one or more components in the wind turbine due to lightning based on the charge representation.

[0009] (3) Measuring the electric field in the air, such as Korean patent No. KR101813851B1, which describes a non-rotating electric field sensor based on an electronic circuit.

[0010] Regarding the patent application with publication number CN 105545615 A, the solution disclosed in the patent application realizes direct measurement of resistance value at the root of the wind turbine blade by using a conductive closed loop. This solution can effectively solve one of the main problems when creating a conductive loop, that is, due to the extremely high current during a lightning strike, the induced voltage will produce a significant risk of arcing between the loop conductors. In response to this problem, the solution disclosed in the patent application with publication number CN105545615A describes a solution for controlling the arc by using a spark gap distributed downward between the conductors of the conductive ring inside the blade.

[0011] Therefore, the solution disclosed in the patent application with publication number CN 105545615 A ​​has the following problems in practical application:

[0012] (1) This solution requires changes to the wiring in the blade itself, so it can only be used as an option for wind turbine blade production and is usually not considered as a modification solution for wind turbine blades.

[0013] (2) The safe application of this solution will require the use of multiple discharge gaps throughout the blade structure, which is complex and costly.

[0014] It can be seen that due to mechanical stress and poor connection, the internal down conductors in the wind turbine blades sometimes break. There is a need in the art for a practical detection scheme that can effectively identify those damaged conductors.

[0015] Among them, detecting damaged conductors by resistance measurement requires the establishment of a conductive loop on the wind turbine blade. This is actually very costly, especially for a retrofit solution, because additional wires need to be attached to the blade for measurement, and the wires may need to be attached to the outside of the blade. The application of fixed loop wires also brings a significant risk of electrical flashover or arcing due to the presence of induced voltage during a lightning strike, which can lead to both an increased risk of damage to the wind turbine blades and a high risk of the loop itself being broken due to lightning discharges. Therefore, adding loop wires is not a preferred solution.

[0016] However, although the high frequency (pulse) wave measurement system does not require a return conductor, this system is complex and therefore expensive. Therefore, this solution is not a preferred solution.

[0017] At the same time, online monitoring solutions are preferred for wind turbine operators to enable targeted preventive maintenance and repairs.

[0018] Therefore, there is a need in the art for a low-cost, safe and simple solution to determine whether a down conductor in a wind turbine blade is broken. Summary of the invention

[0019] The existing scheme for measuring whether the conductor (i.e., down conductor) in the wind turbine blade is broken along its expected path has the problems of high safety risk and complex scheme. The purpose of the present invention is to provide a system for measuring the relative length of the conductive wire in the wind turbine blade. The system scheme is low-cost, safe and simple, and can effectively determine the broken state of the down conductor in the wind turbine blade.

[0020] In order to achieve the above object, the present invention provides a measuring system for conductive lines in a wind turbine blade, comprising:

[0021] A plurality of lightning receptors, which are connected to each other by conductive wires and installed inside each wind turbine blade for receiving lightning strikes;

[0022] A discharge gap device, one end of which is connected to the end of the conductive wire and the other end of which is connected to the ground terminal of each wind turbine blade;

[0023] A measuring unit, the measuring unit is used to measure the ground potential of the internal conductive wires of a plurality of wind turbine blades in an atmospheric environment;

[0024] A determination unit is provided, wherein the determination unit determines the damage state of the conductive wire in each branch blade by comparing the conductive wire-to-ground potential of the wind turbine blade measured by the measuring unit.

[0025] Further, the measurement system measures the potential difference continuously or discontinuously to allow measurement of the full potential accumulated since the last discrete measurement.

[0026] Furthermore, the evaluation of the potential difference is based on a statistical analysis of the time series of recorded data.

[0027] In order to achieve the above-mentioned purpose, the present invention provides a method for measuring conductive wires in wind turbine blades. The method detects the broken state of the down conductors in all blades by measuring the potential difference of the down conductors passing through each blade of the wind turbine and comparing the measured values ​​of all blades of the wind turbine.

[0028] Further, the measurement method measures the potential difference continuously or discontinuously to allow measurement of the full potential accumulated since the last discrete measurement.

[0029] Furthermore, the evaluation of the potential difference in the measuring method is based on a statistical analysis of the recorded data in time series.

[0030] The present invention provides a measurement system whereby relative measurements of charge flow through a wind turbine blade (when facing skyward) can be used to determine if a down conductor is broken in the blade.

[0031] Different from the prior art which focuses the measurement on lightning discharge events, the measurement system provided by the present invention innovatively measures the difference between the conductive wires by measuring the voltage potential. If the potential between the wind turbine blades is different during normal operation (when the blades rotate), it indicates that the conductive wire is damaged.

[0032] The solution provided by the present invention does not require changes or additions to the wiring in the blade itself, and the solution is simple in structure, low in cost, and easy to implement; that is, it is suitable for the production and manufacturing of blades, and can also be used as a solution for the modification of blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0034] Figure 1 This is an example diagram of the arrangement of the measurement system on the blades of a wind turbine in an example of the present invention;

[0035] Figure 2 This is an example diagram of the arrangement of the discharge gap in an example of the present invention;

[0036] Figure 3 This is a diagram showing an example of the composition of a measuring unit in an example of the present invention;

[0037] Figure 4 This is a diagram showing an example of the composition of a measuring unit in an example of the present invention. DETAILED DESCRIPTION

[0038] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0039] In view of the fact that the internal down conductor (i.e., the conductive wire) in the wind turbine blade is sometimes broken, the present invention provides a measurement system which is installed in the wind turbine and is used to monitor whether the down conductor in the wind turbine blade is completely connected throughout the blade.

[0040] Specifically, the measurement system utilizes the discharge gap to detect the fracture state of the down conductors in all blades by measuring the charge flow of the down conductor passing through each blade of the wind turbine and comparing the measured values ​​of all blades of the wind turbine.

[0041] Furthermore, the measurement system uses the natural charge and voltage potential differences in the atmosphere around the wind turbine during normal operation (i.e. when the blades are rotating) to complete the detection. If a blade has a relatively small charge flow in normal operation, it indicates that the down conductor in the blade is damaged. Depending on the setting, an alarm can be generated to indicate the faulty down conductor.

[0042] Different from the existing solutions, the solution of the present invention does not focus on lightning discharge events, but measures voltage potential. At the same time, the measured voltage potential is not used to determine the potential in free air or the conductivity of the wire loop as conventionally, but innovatively measures the difference between the wires through the measured voltage potential, thereby achieving low cost and forming a simple wind turbine blade internal down conductor fracture state detection.

[0043] See also Figure 1 , which shows an application example of the measurement system provided by the present invention based on the above principle.

[0044] As shown in the figure, the measurement system provided in this example mainly includes a plurality of lightning rods 10 , a discharge gap device 20 , a measurement unit 30 and a determination unit 40 .

[0045] In this example, a plurality of lightning receptors 40 are interconnected by down conductors 50 and installed inside each wind turbine blade for receiving lightning strikes.

[0046] As an example, in a specific implementation, this example installs a plurality of lightning receptors 10 on the blade surface 100 starting from the top 110 and moving downward along the length of the blade toward the root 120. At the same time, the lightning receptors 10 are interconnected in series through the down conductor 50.

[0047] On this basis, at the root 120 of the blade, the down conductor 50 is connected to the hub for further connecting the tower and the ground (or sea surface). The measuring unit 30 of each blade is located at the root of the blade.

[0048] The discharge gap 20 of this embodiment, which is placed in series with the down conductor 50 in the blade, ensures a path for current conduction through the discharge gap and serves as isolation for measurement during normal operation.

[0049] See also Figure 2 , which shows an example of setting the discharge gap 20 in the measurement system given in this example.

[0050] As shown in the figure, in the specific implementation, this example connects one end of the discharge gap 20 to the end of the down conductor 50 in the blade, and the other end is connected to the grounding end of each wind turbine blade; at the same time, a measurement line 21 is bridged across the discharge gap 20 as an interface for connecting to the measurement unit 30 in this measurement system.

[0051] The measuring unit 30 in this example cooperates with the discharge gap 20 to measure the potential of the conductive wires inside the blades of a plurality of wind turbines to the ground in the atmospheric environment.

[0052] See also Figure 3 , which shows an example of the structure of the measuring unit 30 in the measuring system given in this example.

[0053] As shown in the figure, in a specific implementation, the measuring unit 30 in this example is mainly composed of a protection circuit 31 and a signal adjustment circuit 32.

[0054] The protection circuit 31 forms an input terminal 33 for connecting the input of the discharge gap 20. The specific structure of the protection circuit 31 can be determined according to actual needs and is not limited here.

[0055] In coordination therewith, the signal conditioning circuit 32 is connected to the protection circuit 31 and forms an output terminal 34 for connecting to the measuring unit 40 .

[0056] The specific structure of the signal conditioning circuit 32 can be determined according to actual needs and is not limited here.

[0057] The measuring unit 30 configured in this way can ensure that the lightning receptor 10 remains close to the ground potential and measure the state of the charge carried by the blade down conductor 50 .

[0058] The determination unit 40 in this example is connected and cooperated with the measurement unit 30, and can determine whether the conductive wire of a blade is damaged by comparing the measured potential of the conductive wire of the wind turbine blade to the ground, thereby generating a corresponding evaluation result.

[0059] See also Figure 4 , which shows an example of the structure of the measuring unit 40 in the measurement system given in this example.

[0060] As shown in the figure, in a specific implementation, the determination unit 40 in this example can be formed by a logic chip, but is not limited thereto.

[0061] The determination unit 40 configured in this way can compare the charged states of the down conductors on each blade in the wind turbine measured by the measurement unit 30 with each other and with the relevant data of other blades, and determine the connection state of the down conductor in each blade according to the comparison result.

[0062] If a down conductor in a certain blade is determined to be damaged (eg broken), maintenance is required to ensure the correct connection of the down conductor system, and a corresponding alarm may be generated to indicate the faulty down conductor.

[0063] There is no limitation on the alarm mode, which may be one or more of optical, relay driven or digital communication modes. If it is a digital communication mode, a wired or wireless communication mode may be used.

[0064] The following is a specific application example to illustrate the process of using the measurement system provided by the present invention to measure the fracture state of the internal down conductor (ie, the conductive wire) in the fan blade.

[0065] Here, a typical three-blade wind turbine is taken as an example. For each blade in the wind turbine, a plurality of lightning receptors 10 are installed on the surface of the blade 100 starting from the top 110 and extending downward along the length of the blade toward the root. The plurality of lightning receptors are interconnected in series through down conductors 50 (e.g., Figure 1 ). At the root of the blade, the down conductor is connected to the hub for further connection between the tower and the ground (or sea surface).

[0066] like Figure 2 As shown, for each blade, the connection terminal at the connection point of the blade root toward the blade tip is removed, and a discharge gap 20 is connected in series. A measurement line 21 is bridged across the discharge gap as an interface to connect to the measurement unit in the measurement system.

[0067] A measuring unit 300 is respectively configured for each blade, and the measuring unit 300 on each blade is preferably arranged at the root of the blade.

[0068] like Figure 3 As shown, the measuring unit 300 is mainly composed of a protection circuit 31 and a signal conditioning circuit 32.

[0069] On this basis, a measuring unit 40 is configured for the wind turbine. Figure 4 As shown, the determination unit 40 is a corresponding detection logic unit having three input ports B1 , B2 , B3 , three direct output ports A1 , A2 , A3 and one communication port C.

[0070] The three input ports B1, B2, and B3 are respectively connected to the output of the measurement unit 300 configured on each blade of the wind turbine.

[0071] The three direct output ports A1, A2, A3 can be used as alarm output ports corresponding to the three input ports B1, B2, B3, and connected to alarm devices, thereby realizing independent alarm for each blade on the wind turbine.

[0072] One communication port C can be used for external communication data transmission.

[0073] Therefore, the measuring unit 40 can receive the output signal from the measuring unit connected to each blade through the three input ports B1, B2, and B3, and process it in the unit itself. It can directly output an alarm for each blade through the three direct output ports A1, A2, and A3; at the same time, communication data is transmitted to the outside through the communication port C.

[0074] Under this setting scheme, the relative measurement value of the downconductor length of the designed blades of the three-blade wind turbine can be achieved to measure whether the downconductor interconnecting the lightning arresters in each blade is disconnected.

[0075] Here, the amount of charge carried by the corresponding blades on the wind turbine is measured, and the relative physical length of the conductor is calculated from this.

[0076] Thus, if it is assumed that under a fault condition, at least one down conductor has a different electrical connection length from the other down conductors, and the wind turbine is in a normal operating state (ie, the blades of the wind turbine are rotating).

[0077] According to the above configuration, when a wind turbine equipped with the measurement system provided by the present invention is in normal operating state (i.e., the wind turbine blades are rotating), each measurement unit in the measurement system measures the charge flow generated by the voltage potential difference between the down conductor of the blade and the nacelle, thereby measuring the potential difference.

[0078] In this case, assuming that the nacelle is well grounded, the comparison of the voltage potential measurement results of the blades during one rotation by the measuring unit in the measurement system will reveal whether one or more blades have a low voltage potential difference. For blades with a low voltage potential difference, it is determined that the down conductor in the blade is damaged and may need repair. At this time, an alarm can be output through the alarm device corresponding to the blade.

[0079] In actual application, when measuring based on this measurement system, it depends on the existence of a certain level of electric field in the air around the wind turbine and the wind turbine is rotating, so it is impossible to guarantee the instant reading of the health status of the down conductor.

[0080] However, in most practical situations, fans meet both measurement conditions on a daily or at least weekly basis.

[0081] In this case, in the measurement system, the effective time of relative measurement of the wind turbine blades can be classified by the determination unit, and then it can be checked whether there are statistical differences in the relative measurement values ​​measured on the down conductors of each wind turbine blade during these effective time periods.

[0082] In actual application, when lightning strikes the lightning arrester and down conductor, the system can establish a conduction path through the series-connected discharge gap. This can be achieved by using a safe, reliable and clearly specified discharge gap (for example, 2kV breakdown voltage) and designing corresponding measurement units and determination units to enable them to withstand such voltage levels (including a reasonable safety margin).

[0083] In this way, all the expected functions of the lightning receptor and the down conductor can be realized, and at the same time, the measuring electronic equipment (such as the measuring unit, the determining unit) of the present invention can withstand the lightning strike and continue to detect whether the down conductor is disconnected.

[0084] In practical applications, in order to be able to measure the charge accumulated in the blades, the blades need to be almost isolated from the ground potential, i.e. the impedance presents a high resistivity (in the megohm range). Therefore, the potential difference between the blades and the ground potential can actually be measured.

[0085] In actual application, when the blade is separated from the strong ground connection (i.e., the blade down conductor is separated from the grounding system), it needs a surge current release path, such as discharge when lightning occurs, which is achieved by using a discharge gap in the measurement system solution provided by the present invention. At the same time, the measurement electronic equipment (such as the measurement unit, the determination unit) in the measurement system solution provided by the present invention ensures that the potential difference does not exceed the breakdown voltage of the discharge gap during normal operation; this will also ensure that the lightning receptor continues to present a potential that can attract lightning discharge.

[0086] The measurement scheme provided by the present invention can be used to determine if a down conductor is broken in a blade by making relative measurements of the charge flow of the wind turbine blades (when facing the sky). The electric field between the sky and the ground can change significantly over time, especially during thunderstorms. Often there are no direct lightning strikes when a storm passes, but an increase in potential can still be clearly detected; but if this potential is different between the wind turbine blades during normal operation (when the blades are rotating), it indicates that the down conductor in the corresponding blade is broken.

[0087] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A measurement system for conductive lines in wind turbine blades, comprising: A plurality of lightning receptors, which are connected to each other by conductive wires and installed inside each wind turbine blade for receiving lightning strikes; Characterized in that the measurement system also includes: A discharge gap device, one end of which is connected to the end of the conductive wire, and the other end is connected to the grounding terminal of each wind turbine blade; at the same time, a measuring line is connected across the discharge gap as an interface for connecting to the measuring unit in the measuring system; A measuring unit, the measuring unit is connected and cooperated with the discharge gap device, and is used to measure the ground potential of the internal conductive wires of multiple wind turbine blades in an atmospheric environment; the measuring unit can also ensure that the lightning receptor remains close to the ground potential and measure the state of the electric charge carried by the blade conductive wire; A determination unit is connected and cooperated with the measuring unit to determine the damage state of the conductive wire in each branch blade by comparing the conductive wire-to-ground potential of the wind turbine blade measured by the measuring unit.

2. The measuring system for conductive lines in wind turbine blades according to claim 1, characterized in that: The measurement system measures the potential difference continuously or discontinuously to allow measurement of the full potential accumulated since the last discrete measurement.

3. The measuring system for conductive lines in wind turbine blades according to claim 2, characterized in that: The evaluation of the potential difference is based on a statistical analysis of the time series of recorded data.

4. A method for measuring conductive lines in wind turbine blades, characterized in that: The measuring method is based on the measuring system described in any one of claims 1 to 3. Without changing or adding wiring in the blades themselves, the measuring method utilizes the discharge gap to measure the potential difference of the conductive wires passing through each blade of the wind turbine and compares the measured values ​​of all blades of the wind turbine to detect the broken state of the conductive wires in all blades.

5. The method for measuring conductive lines in a wind turbine blade according to claim 4, characterized in that: The measurement method measures the potential difference continuously or discontinuously, allowing measurement of the full potential accumulated since the last discrete measurement.

6. The method for measuring conductive lines in a wind turbine blade according to claim 4, characterized in that: The evaluation of the potential difference in the measuring method is based on a statistical analysis of the recorded data in time series.

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