Lightning conductor inspection device

Abstract

To provide an inspection device capable of outputting a measurement result that is useful for a user to avoid erroneous determination as to the presence or absence of disconnection even when a lightning conductor is disconnected at a tip end.SOLUTION: A lightning conductor inspection device 1 is provided, comprising: an inspection signal generation unit 10 configured to generate an inspection signal and output the inspection signal to a receptor 106 connected to the tip end portion of a lightning conductor 110; and a measurement unit 20 configured to observe a voltage or current waveform at the receptor 106 and measure a time difference Δt between an arrival time of the inspection signal and an arrival time of a reflected wave of the inspection signal.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an inspection device for lightning conductors (down conductors). [Background technology]

[0002] Patent Documents 1 and 2 describe a technique for detecting a break in a lightning conductor by injecting a step wave from the base of the lightning conductor and observing the step wave and its reflected wave. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-29351 [Patent Document 2] Patent Publication No. 2021-25859 Summary of the Invention [Problem to be solved by the invention]

[0004] In the techniques described in Patent Documents 1 and 2, when the lightning conductor is not broken, a step wave reflected from the connection with the receptor is observed, as shown in FIG. 10(A). On the other hand, when the lightning conductor is broken near its tip, a step wave reflected from the break is observed, as shown in FIG. 10(B). Because the break is close to the receptor, for example, as shown in FIG. 11, the reflected wave observed when the lightning conductor is broken a few centimeters from its tip is almost identical to the reflected wave observed when the lightning conductor is not broken, which may lead to a false determination that the lightning conductor is not broken. Furthermore, as shown in FIGS. 10(A) and 10(B), it is necessary to disconnect the connection between the lightning conductor and the ground wire and connect an inspection device between them. However, if the connection between the lightning conductor and the ground wire is deteriorated, the connection may break when disconnected, or it may be impossible to disconnect the connection.

[0005] Therefore, the problem that the present invention aims to solve is to provide an inspection device that can output useful measurement results so that the user does not erroneously determine whether or not a lightning conductor is broken, even if the lightning conductor is broken at the tip. [Means for solving the problem]

[0006] The present invention has been made to solve at least some of the above-mentioned problems, and can be realized in the following aspects or application examples.

[0007] [Application example 1] The lightning conductor inspection device according to this application example is characterized by comprising an inspection signal generating unit that generates an inspection signal and outputs the inspection signal to a receptor connected to the tip of the lightning conductor, and a measuring unit that observes the voltage waveform or current waveform of the receptor and measures the time difference between the arrival time of the inspection signal and the arrival time of the reflected wave of the inspection signal.

[0008] In the lightning conductor inspection device according to this application example, the inspection signal generator outputs an inspection signal to a receptor connected to the tip of the lightning conductor, and the measurement unit observes the response waveform to measure the time difference between the arrival time of the inspection signal and the arrival time of the reflected wave of the inspection signal. If the lightning conductor is not broken, the inspection signal is reflected at the base of the lightning conductor, and if the lightning conductor is broken, the inspection signal is reflected at the broken part of the lightning conductor and reaches the receptor. Therefore, the arrival time of the reflected wave when the lightning conductor is broken at the tip is longer than the arrival time when the lightning conductor is broken at a part other than the tip. The lightning conductor inspection device according to this application example can output useful measurement results so that the user does not erroneously determine whether the lightning conductor is broken or not, even if the lightning conductor is broken at its tip.

[0009] [Application example 2] In the lightning conductor inspection device according to the above application example, the measurement unit may use the measured time difference to determine a distance traveled by the inspection signal or a position at which the inspection signal is reflected.

[0010] The lightning conductor inspection device of this application example determines the distance traveled by the inspection signal or the position at which the inspection signal is reflected, allowing the user to determine whether or not the lightning conductor is broken and where the break is located based on that distance or that position.

[0011] [Application example 3] In the lightning conductor inspection device according to the above application example, the measurement unit may be connected to a grounding member that grounds a base portion of the lightning conductor.

[0012] In the lightning conductor inspection device according to this application example, if the lightning conductor is not broken, the grounding member creates a short-circuit state (0 Ω) between the receptor and the ground, so that at the base of the lightning conductor, voltage returns by negative reflection and current returns by specular reflection. On the other hand, if the lightning conductor is broken, the receptor and the ground create an open state (∞ Ω), so that at the break in the lightning conductor, voltage returns by specular reflection and current returns by negative reflection. Therefore, the polarity of the reflected wave differs between when the lightning conductor is not broken and when it is broken, allowing the user to determine whether the lightning conductor is broken. In particular, the arrival time of the reflected wave when the base of the lightning conductor is broken is approximately the same as the arrival time of the reflected wave when the lightning conductor is not broken, but the polarity of the reflected wave is different, so the user can determine whether the base of the lightning conductor is broken from the polarity of the reflected wave.

[0013] [Application example 4] In the lightning conductor inspection device according to the above application example, the inspection signal may be a pulse wave.

[0014] According to the lightning conductor inspection device of this application example, the inspection signal generating unit outputs an inspection signal that is a pulse wave rather than a step wave to the lightning conductor, making it easier to separate the inspection signal from its reflected wave and reducing the risk of the measuring unit making an incorrect measurement. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing the configuration of a wind turbine that is an object to be inspected by an inspection device according to an embodiment of the present invention; [Figure 2] 1 is an external view of an inspection device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a functional block diagram of the inspection device according to the present embodiment. [Figure 4] (A) is a diagram showing the measurement state when the lightning conductor is not broken, and (B) is a diagram showing the observed voltage and current waveforms. [Figure 5] (A) is a diagram showing the measurement state when the lightning conductor is broken at the tip, and (B) is a diagram showing the observed voltage and current waveforms. [Figure 6] (A) is a diagram showing the measurement state when the lightning conductor is broken at its base, and (B) is a diagram showing the observed voltage and current waveforms. [Figure 7] 1A is a diagram showing an example of a voltage waveform observed in response to an inspection signal that is a step wave, and FIG. 1B is a diagram showing an example of a voltage waveform observed in response to an inspection signal that is a pulse wave. [Figure 8] FIG. 4 is a diagram illustrating an example of information displayed on a display unit. [Figure 9] FIG. 2 is a flowchart showing a processing procedure of the inspection device according to the present embodiment. [Figure 10] (A) is a schematic diagram of the conventional measurement state when the lightning conductor is not broken, and (B) is a schematic diagram of the conventional measurement state when the lightning conductor is broken. [Figure 11] FIG. 1 is a diagram showing an example of a voltage waveform observed by a conventional measurement method. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The drawings used in this description are for the convenience of explanation. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0017] The following description will be given taking as an example an inspection device for inspecting whether or not a lightning conductor built into the blades (wind turbine blades) of a wind turbine for wind power generation is broken.

[0018] 1. Wind turbine configuration FIG. 1 shows an inspection device according to this embodiment connected to a lightning conductor built into a wind turbine blade. As shown in FIG. 1, a wind turbine 100 to be inspected includes a tower 101, a nacelle 102 connected to the tower 101, and a wind turbine rotor 103 connected to the nacelle 102. That is, the wind turbine rotor 103 is supported on the tower 101 via the nacelle 102. The wind turbine rotor 103 includes a rotor head (hub) 104 and blades 105 attached to the rotor head 104. The wind turbine rotor 103 may be provided with one blade 105 or multiple blades 105. The blade 105 includes a receptor 106, which is a lightning receiving part made of a conductor for capturing lightning, and a lightning conductor 110 built into it. The tip of the lightning conductor 110 is connected to the receptor 106. The tower 101 houses a climbing ladder 107 and a grounding wire 120. The base of the lightning conductor 110 is connected to one end of the grounding wire 120 at connection point 130. The other end of the grounding wire 120 is connected to the support of the climbing ladder 107. The climbing ladder 107 is at the same potential (0 V) as the ground G, and the grounding wire 120 is grounded via the climbing ladder 107. Therefore, during wind power generation, lightning captured by the receptor 106 is discharged to the ground G via the lightning conductor 110, the grounding wire 120, and the climbing ladder 107. In this way, the grounding wire 120 and the climbing ladder 107 are grounding members that ground the base of the lightning conductor 110. During the inspection, the inspector connects the inspection device 1 between the receptor 106 and the grounding member (grounding wire 120 or climbing ladder 107) and uses the inspection device 1 to inspect whether the lightning conductor 110 is broken.

[0019] 2. Configuration and functions of the inspection device FIG. 2 is an external view of the inspection device 1, and FIG. 3 is a functional block diagram of the inspection device 1. As shown in FIG. 2, the inspection device 1 includes a rectangular parallelepiped housing 2. A connection terminal 3 is provided on the top surface of the housing 2. An operation unit 30 including a power button 31 and an application button 32, and a display unit 40 are provided on the front surface of the housing 2. The connection terminal 3 is, for example, a coaxial connector. For example, the inspector couples a coaxial cable (not shown) to the connection terminal 3, separates the coaxial cable into a signal cable 201 and a ground cable 202 shown in FIG. 1 using a conversion adapter, connects the signal cable 201 to the receptor 106, and connects the ground cable 202 to the ground wire 120 or the climbing ladder 107. The inspector then operates the power button 31 to set the inspection device 1 to a state where it can inspect the lightning conductor 110, and operates the application button 32 to apply an inspection signal to the receptor 106 to perform the inspection.

[0020] As shown in FIG. 3, the inspection device 1 includes an inspection signal generating unit 10, a measuring unit 20, and an operation unit 30. , a display unit 40, a recording unit 50, and a battery 60. The inspection signal generating unit 10, the measuring unit 20, the recording unit 50, and the battery 60 are housed in a housing 2 shown in FIG. 2. The inspection signal generating unit 10 and the measuring unit 20 are connected to the receptor 106 by a signal cable 201. The measuring unit 20 is connected to a ground member (ground wire 120 or climbing ladder 107) by a ground cable 202.

[0021] The test signal generating unit 10 generates a predetermined test signal based on the ground potential (0 V) and outputs the test signal to the receptor 106. For example, the test signal generating unit 10 includes a boost circuit 12, a capacitor 13, a semiconductor switch 14, a matching resistor 15, and a control circuit 16. A DC voltage is supplied to the boost circuit 12 from a battery 60. The DC voltage output from the battery 60 is also used as a power supply voltage for operating the measuring unit 20.

[0022] The DC voltage output from battery 60 is boosted to several tens to several hundreds of volts by boost circuit 12, and a charge corresponding to the output voltage of boost circuit 12 is accumulated in capacitor 13. The charge accumulated in capacitor 13 is output to receptor 106 via matching resistor 15 when semiconductor switch 14 is on. The on / off of semiconductor switch 14 is controlled by control circuit 16, and a step wave rises when semiconductor switch 14 is turned on. Alternatively, a pulse wave rises when semiconductor switch 14 is turned on, and then the pulse wave falls when semiconductor switch 14 is turned off. In this way, an inspection signal that is a step wave or pulse wave is output to receptor 106.

[0023] The measuring unit 20 is connected to the receptor 106 and the grounding member (grounding wire 120 or climbing ladder 107), observes the voltage or current waveform of the receptor 106 with respect to the ground potential (0 V), and measures the time difference Δt between the arrival time of the test signal and the arrival time of the reflected wave of the test signal. This time difference Δt varies depending on the position at which the test signal is reflected. FIG. 4(A) is a diagram showing the measurement state when the lightning conductor 110 is not broken, and FIG. 4(B) is a diagram showing the voltage and current waveforms observed by the measuring unit 20 in this case. When the lightning conductor 110 is not broken, as shown in FIG. 4(A), the test signal output from the test signal generating unit 10 to the receptor 106 is reflected at the connection point 130 between the lightning conductor 110 and the grounding wire 120, becoming a reflected wave. Because the lightning conductor 110 is not broken, there is a short circuit (0 Ω) between the receptor 106 and the ground G, and as shown in Figure 4(B), the voltage returns by negative reflection and the current returns by positive reflection. In this case, the measuring unit 20 measures the time Δt1 as the time difference Δt between the arrival time of the inspection signal and the arrival time of the reflected wave at the receptor 106.

[0024] On the other hand, FIG. 5(A) is a schematic diagram of the measurement state when the lightning conductor 110 is broken at its tip, and FIG. 5(B) is a schematic diagram of the voltage waveform and current waveform observed by the measurement unit 20 in this case. When the lightning conductor 110 is broken at its tip, as shown in FIG. 5(A), the test signal output from the test signal generator 10 to the receptor 106 is reflected at the broken point at the tip of the lightning conductor 110, becoming a reflected wave. Because the lightning conductor 110 is broken, the state between the receptor 106 and the ground G is open (∞Ω), and as shown in FIG. 5(B), the voltage returns by positive reflection and the current returns by negative reflection. In this case, the measurement unit 20 measures the time difference Δt between the arrival time of the test signal and the arrival time of the reflected wave at the receptor 106 as Δt2, which is shorter than Δt1.

[0025] 6(A) is a diagram showing a measurement state when the lightning conductor 110 is broken at its base, and FIG. 6(B) is a diagram showing a voltage waveform and a current waveform observed by the measurement unit 20 in this case. When the lightning conductor 110 is broken at its base, as shown in FIG. 6(A), the inspection signal output from the inspection signal generating unit 10 to the receptor 106 is reflected at the broken point at the base of the lightning conductor 110, becoming a reflected wave. Since the lightning conductor 110 is broken, the connection between the receptor 106 and the ground G is in an open state (∞Ω), and as shown in FIG. 6(B), As shown in Fig. 4B and Fig. 6B, voltage returns by positive reflection, and current returns by negative reflection. In this case, the measuring unit 20 measures the time difference Δt between the arrival time of the inspection signal and the arrival time of the reflected wave at the receptor 106 as Δt3, which is longer than Δt2 and slightly shorter than Δt1. Here, there is almost no difference between the times Δt1 and Δt3, but as shown in Fig. 4B and Fig. 6B, the measured voltage waveform or current waveform is different, so the measuring unit 20 can determine whether the lightning conductor 110 is broken.

[0026] As shown in FIG. 3, for example, the measurement unit 20 includes a voltage-dividing circuit 21, a comparison circuit 22, a CPU (Central Processing Unit) 23, and a memory 24. The voltage-dividing circuit 21 is connected to the receptor 106 and a ground member (ground wire 120 or climbing ladder 107), and divides the voltage between the receptor 106 and the ground member to several volts (e.g., 3.3 V). For example, the voltage-dividing circuit 21 may include multiple resistors connected in series between the receptor 106 and the ground G, and output a voltage generated by a current flowing through the multiple resistors. The output voltage of the voltage-dividing circuit 21 is compared with a desired threshold voltage VT by a comparison circuit 22, and converted into a binary signal.

[0027] The CPU 23 performs measurement processing in accordance with a program stored in the memory 24. In this embodiment, when the tester presses the application button 32 (see FIG. 2 ) included in the operation unit 30, the CPU 23 receives a signal generated by this pressing operation and outputs a control signal to the control circuit 16 of the test signal generating unit 10 for turning on the semiconductor switch 14 for a predetermined time. In other words, when the tester presses the application button 32, the semiconductor switch 14 is turned on for only the predetermined time regardless of the pressing time, and a test signal is output from the test signal generating unit 10.

[0028] Immediately after turning on the semiconductor switch 14 via the control circuit 16, the CPU 23 measures the time difference Δt between the arrival time of the inspection signal and the arrival time of the reflected wave of the inspection signal at the receptor 106, based on the binary signal output from the comparison circuit 22. If the lightning conductor 110 is broken, the time difference Δt will change depending on the location of the break.

[0029] The waveforms in FIGS. 4B, 5B, and 6B are theoretical waveforms. In contrast, FIGS. 7A and 7B show voltage waveforms actually observed. FIGS. 7A and 7B show voltage waveforms when the lightning conductor 110 is not broken and when it is broken. In FIG. 7A, the test signal is a step wave, while in FIG. 7B, the test signal is a pulse wave. In both FIGS. 7A and 7B, the time difference Δt between the arrival time of the test signal and the arrival time of the reflected wave of the test signal when there is a break in the lightning conductor 110 is shorter than the time difference Δt when there is no break in the lightning conductor 110. When the test signal is a step wave, the measurement unit 20 measures the time difference Δt, for example, from the rising edge of the step wave to the rising edge of the reflected wave of the test signal. Furthermore, when the test signal is a pulse wave, the measurement unit 20 measures the time difference Δt, for example, from the peak of the pulse wave of the test signal to the peak of the reflected wave. Because the timing of the peak of a pulse wave is clearer than the timing of the rise of a step wave, the measurement accuracy of the time difference Δt is higher when the test signal is a pulse wave.

[0030] In this embodiment, the CPU 23 further uses the measured time difference Δt to determine the distance L traveled by the inspection signal output from the inspection signal generating unit 10 or the position P at which the inspection signal is reflected. Specifically, the CPU 23 can calculate the distance L traveled by the inspection signal using the propagation speed v of the inspection signal traveling through the lightning conductor 110 and the time difference Δt, as shown in equation (1). The position P at which the inspection signal is reflected is calculated as ½ of the distance L.

number

[0031] Generally, the propagation velocity v is slower than the speed of light c. The CPU 23 calculates the relative dielectric constant ε of the cable insulator of the lightning conductor 110 using the formula (2). S , relative permeability μ S It is also possible to calculate the propagation velocity v from

number

[0032] However, the relative permittivity ε S , relative permeability μ S Since it is difficult to accurately calculate this, the easiest method is to use the product of the speed of light c and an appropriate correction coefficient a as the propagation velocity v, as in equation (3). The correction coefficient a is calculated as the ratio of the distance L, which is calculated using equation (1) using the time difference Δt measured when the lightning conductor 110 is not broken, assuming that the propagation velocity v is equal to the speed of light c, to the length of the lightning conductor 110. For example, if the length of the lightning conductor 110 is 24 m and the distance L is 25 m, the appropriate correction coefficient a is 24 / 25 = 0.96.

number

[0033] Before starting measurement, the tester operates the power button 31 and the application button 32 (see FIG. 2 ) included in the operation unit 30 to switch the test device 1 to a setting mode, and then operates the application button 32 in the setting mode to adjust the value of the correction coefficient a. When the tester operates the application button 32, the CPU 23 receives a signal generated by this operation and sets the adjusted value to the correction coefficient a. When the tester presses the application button 32, the CPU 23 measures the time difference Δt, calculates the distance L using equations (3) and (1), and displays the calculated distance L on the display unit 40. The CPU 23 may calculate the position P and display the position P on the display unit 40, or may calculate the distance L and the position P and display the distance L and the position P on the display unit 40. The CPU 23 may also display the reflection time t=Δt and the correction coefficient a on the display unit 40. FIG. 8 shows an example of information displayed on the display unit 40. In the example of FIG. 8, the value of the correction coefficient a is 0.67, the reflection time t is 249 ns, and the distance L is 25 m.

[0034] The CPU 23 also outputs a signal to the recording unit 50 instructing it to record the measurement results together with the measurement results on a recording medium. Upon receiving this signal, the recording unit 50 records the measurement results on the recording medium. The recording medium is, for example, an SD card. The measurement results include at least one of the distance L and the position P calculated by the measurement unit 20, and may also include a time difference Δt.

[0035] 3. Inspection equipment processing procedures Finally, a flowchart showing the processing procedure of the inspection device 1 described above is shown in Fig. 9. For example, the inspection device 1 is started up when the power button 31 is pressed, and the CPU 23 executes a program stored in the memory 24, thereby performing the processing shown in Fig. 9. As shown in Fig. 9, if the application button 32 is pressed (Y in step S10) at the time of start-up (when the power button 31 is pressed), the inspection device 1 transitions to a setting mode and performs correction. The positive coefficient a is set to an initial value (step S20). The initial value is the maximum value within the range of possible values ​​for the correction coefficient a, for example, 1. Next, if the application button 32 is pressed (Y in step S30), the inspection device 1 subtracts a predetermined amount from the value of the correction coefficient a (step S40). The predetermined amount is, for example, 0.01. If the application button 32 is not pressed (N in step S30), the inspection device 1 does not perform the process of step S40. Next, if any operation is performed within a certain time period (N in step S50), the inspection device 1 performs the processes of steps S30 and S40 again. If no operation is performed within the certain time period (Y in step S50), the inspection device 1 saves the value of the correction coefficient a (step S60) and ends the process.

[0036] On the other hand, if the application button 32 is not pressed at startup (N in step S10), the inspection device 1 transitions to measurement mode and sets the correction coefficient a to the value saved in step S60 (step S70). If the inspection device 1 has not previously performed step S60, it simply sets the correction coefficient a to its initial value. Next, the inspection device 1 waits until the application button 32 is pressed (N in step S80). When the application button 32 is pressed (Y in step S80), the inspection device 1 generates an inspection signal and outputs it to the receptor 106 (step S90). The inspection device 1 then acquires the voltage of the receptor 106 (step S100) until a predetermined time has elapsed (N in step S110). This predetermined time is set to be longer than the time it takes for a reflected wave to be observed after an inspection signal is generated if the root of the lightning conductor 110 (the portion connected to the ground wire 120 at the connection point 130) is disconnected.

[0037] Next, after a predetermined time has elapsed (Y in step S110), if a reflected wave is observed in the time series of voltages acquired in step S100 (Y in step S120), the inspection device 1 calculates the time difference Δt between the arrival time of the inspection signal and the arrival time of the reflected wave at the receptor 106 (step S130). Next, the inspection device 1 calculates at least one of the propagation distance L of the inspection signal and the reflection position P from the time difference Δt calculated in step S130 and the value of the correction coefficient a (step S140). Next, the inspection device 1 displays the calculation result of step S140 and the reflection time t (= Δt) on the display unit 40 (step S150). On the other hand, if a reflected wave is not observed in the time series of voltages acquired in step S100 (N in step S120), the inspection device 1 displays an error on the display unit 40 (step S160). A case in which a reflected wave is not observed may be when the inspection device 1 and the receptor 106 are not properly connected. Then, the inspection device 1 repeats the processes of steps S70 to S160 until the inspection is completed (N in step S170).

[0038] 4. Effects As described above, in the inspection device 1 according to this embodiment, the inspection signal generating unit 10 does not output an inspection signal to the base of the lightning conductor 110 as in the techniques described in Patent Documents 1 and 2, but outputs the inspection signal to the receptor 106 connected to the tip of the lightning conductor 110. Therefore, if the lightning conductor 110 is not broken, the inspection signal is reflected at the base of the lightning conductor 110, and if the lightning conductor 110 is broken, the inspection signal is reflected at the break in the lightning conductor 110 and reaches the receptor 106. Therefore, with the inspection device 1 according to this embodiment, the inspector can accurately determine whether the lightning conductor 110 is broken or not based on the time difference Δt measured by the measuring unit 20. In particular, if the lightning conductor 110 is broken at its tip, the reflected wave immediately reaches the receptor 106, and the arrival time of the reflected wave is shorter than the arrival time of the reflected wave when the lightning conductor 110 is broken at a location other than the tip, or the arrival time of the reflected wave when the lightning conductor 110 is not broken. Therefore, the person conducting the inspection can determine whether the lightning conductor 110 is broken at its tip based on the time difference Δt measured by the measurement unit 20, thereby reducing the risk of erroneously determining that the lightning conductor 110 is not broken even when it is broken at its tip. Furthermore, if the inspection signal generating unit 10 outputs an inspection signal that is a pulse wave rather than a step wave to the lightning conductor 110, the inspection signal and its reflected wave are easily separated, further reducing the risk of the measurement unit 20 making an erroneous measurement. Note that if the lightning conductor 110 is broken at a location other than the tip, the inspection can be performed more efficiently. In order to reduce the impact on the measurement results if the cable is broken, it is preferable that the signal cable 201 connecting the test device 1 and the receptor 106 be as short as possible. Also, it is preferable that the test signal has a waveform with a sufficiently fast rise time.

[0039] Furthermore, according to the inspection device 1 of this embodiment, the measuring unit 20 calculates the distance L over which the inspection signal has propagated or the position P at which the inspection signal has been reflected, allowing the inspector to determine whether or not the lightning conductor 110 is broken and the location of the break based on the distance L or the position P. Furthermore, according to the inspection device 1 of this embodiment, if the lightning conductor 110 is not broken, the grounding member (the grounding wire 120 and the climbing ladder 107) creates a short-circuit state (0 Ω) between the receptor 106 and the ground G, so that at the base of the lightning conductor 110, voltage returns by negative reflection and current returns by specular reflection. On the other hand, if the lightning conductor 110 is broken, the state between the receptor 106 and the ground G is open (∞ Ω), so that at the location of the break in the lightning conductor 110, voltage returns by specular reflection and current returns by negative reflection. Therefore, the polarity of the reflected wave differs between when the lightning conductor 110 is not broken and when it is, allowing the inspector to determine whether or not the lightning conductor 110 is broken. In particular, the arrival time of the reflected wave when the base of the lightning conductor 110 is broken is approximately the same as the arrival time of the reflected wave when the lightning conductor 110 is not broken, but the polarity of the reflected wave is different, allowing the inspector to determine from the polarity of the reflected wave that the base of the lightning conductor 110 is broken. Furthermore, because the grounding member (grounding wire 120 and climbing ladder 107) is sufficiently longer than the lightning conductor 110, reflection from the grounding member is unlikely to adversely affect the measurement of the time difference Δt.

[0040] Furthermore, with the inspection device 1 according to this embodiment, an inspector can inspect the lightning conductor 110 without disconnecting the connection between the lightning conductor 110 and the ground wire 120 at the connection point 130, which makes it less likely that the connection point 130 will be damaged and extends the life of the lightning protection equipment. Furthermore, since the measurement is performed on the entire grounding system of the wind turbine 100, including the receptor 106, the lightning conductor 110, the connection point 130, and the ground wire 120, it is possible to confirm not only the soundness of the lightning conductor 110 but also the soundness of the entire grounding system of the wind turbine 100. Meanwhile, because the connection between the lightning conductor 110 and the ground wire 120 at the connection point 130 is not disconnected, reflected waves are also observed from the bases of the lightning conductors 110 built into blades 105 other than the blade 105 being inspected. However, these reflected waves propagate a distance at least twice the length of the blade 105 and therefore do not affect the measurement. Even if there is a break in the lightning conductor 110 built into a blade 105 other than the blade 105 being inspected, the reflection at the break propagates a distance longer than the length of the blade 105, so the impact on the measurement is minor.

[0041] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations with the same function, method, and result, or configurations with the same purpose and effect). The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments. [Explanation of symbols]

[0042] 1...inspection device, 2...casing, 3...connection terminal, 10...inspection signal generator, 12...booster circuit, 13...capacitor, 14...semiconductor switch, 15...matching resistor, 16...control circuit, 20...measuring unit, 21...voltage divider circuit, 22...comparison circuit, 23...CPU, 24...memory, 30...operation unit, 31...power button, 32...apply button, 40...display unit, 50...recording unit, 60...battery, 100...wind turbine, 101...tower, 102...nacelle, 103...wind turbine rotor, 104...rotor head, 105...blade, 106...receptor, 107...climbing ladder, 110...lightning conductor, 120...grounding wire, 130...connection point, 201...signal cable, 202...grounding cable L

Claims

1. an inspection signal generating unit that generates an inspection signal and outputs the inspection signal to a receptor connected to the tip of the lightning conductor; a measurement unit that observes the voltage waveform or current waveform of the receptor and measures the time difference between the arrival time of the inspection signal and the arrival time of the reflected wave of the inspection signal.

2. The lightning conductor inspection device according to claim 1, The lightning conductor inspection device according to claim 1, wherein the measurement unit uses the measured time difference to determine the distance traveled by the inspection signal or the position at which the inspection signal is reflected.

3. 3. The lightning conductor inspection device according to claim 1, A lightning conductor inspection device characterized in that the measuring unit is connected to a grounding member that grounds the root portion of the lightning conductor.

4. 3. The lightning conductor inspection device according to claim 1, 10. The lightning conductor inspection device according to claim 9, wherein the inspection signal is a pulse wave.

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