Lightning current suppression device

Abstract

A lightning current suppression device 30 includes a switching unit 31 and a suppression unit 35. The switching unit 31 includes: an interruption unit 33 that interrupts the path of lightning current when lightning current that is at least a prescribed current value flows; and a switch 32 that operates due to an increase in potential according to the lightning current, and that switches the path to the suppression unit 35. The suppression unit 35 suppresses the lightning current.

Description

Lightning current suppressor

[0001] The present disclosure relates to a lightning current suppression device.

[0002] In recent years, unmanned aerial vehicles (drones) have been developing remarkably, and their use in various applications is expanding. As an example of the use of unmanned aerial vehicles, research is being conducted on a system that uses unmanned aerial vehicles to control lightning strikes (Non-Patent Document 1).

[0003] Furthermore, in such systems, unmanned aircraft are subject to direct lightning strikes, and research is also being conducted into technologies to prevent unmanned aircraft from breaking down or being damaged in such situations (Non-Patent Document 2).

[0004] Nippon Telegraph and Telephone Corporation, "Protecting people and equipment from lightning strikes while utilizing lightning energy," NTT R&D Forum 2020 Connect E03 Lightning Control and Charging Technology. Toshihisa Masuda, Toshito Arai, Masato Maruyama, Jun Kato, "Fundamental Study on Improving Drone Lightning Resistance," 2021 IEICE-Social Science University, B-4-6, pp. 179, 2021.

[0005] In order to induce lightning using an unmanned aerial vehicle (hereinafter referred to as "lightning triggering"), it is necessary to guide the lightning to the ground via the unmanned aerial vehicle. In order to make the unmanned aerial vehicle resistant to lightning, Non-Patent Document 2 uses a metal cage called a Faraday cage.

[0006] However, to withstand larger lightning strikes, the metal rods that make up the Faraday cage must be thicker to allow more lightning current to flow. However, thicker materials increase the weight of the Faraday cage, which increases the payload and shortens the flight time. On the other hand, if the Faraday cage material is not thick enough to withstand larger lightning strikes, there is a risk that the unmanned aerial vehicle will be damaged or malfunction due to lightning strikes, resulting in a crash.

[0007] The present disclosure has been made in consideration of the above circumstances, and the purpose of the present disclosure is to provide a technology that improves the lightning resistance of unmanned aerial vehicles without increasing the Faraday cage.

[0008] In order to achieve the above-mentioned objective, a lightning current suppression device according to one embodiment of the present disclosure comprises a switching unit and a suppression unit, wherein the switching unit comprises a blocking unit that blocks the path of the lightning current when a lightning current of a predetermined current value or greater flows, and a switch that operates in response to an increase in potential caused by the lightning current and switches the path to the suppression unit, and the suppression unit suppresses the lightning current.

[0009] According to the present disclosure, a technology can be provided that improves the lightning resistance of unmanned aerial vehicles without increasing the Faraday cage.

[0010] Fig. 1 is an overall configuration diagram of a lightning control system according to a first embodiment. Fig. 2 is a diagram showing an example of the configuration of a lightning current suppression device. Fig. 3 is a diagram showing the flow of lightning current in a lightning current suppression device. Fig. 4 is a diagram showing voltage waveforms and current waveforms. Fig. 5 is an overall configuration diagram of a lightning control system according to a second embodiment.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same parts are designated by the same reference numerals and the description thereof will be omitted.

[0012] 1 is a diagram showing the overall configuration of a lightning control system according to this embodiment. The lightning control system includes an unmanned aerial vehicle 20, a cage 10, and a lightning current suppression device 30.

[0013] The unmanned aerial vehicle (UAV) 20 is an air vehicle also known as a drone. The unmanned aerial vehicle 20 of this embodiment is enclosed in a metal cage 10 to provide resistance to lightning strikes.

[0014] The cage 10 is a metal shield that receives lightning current from above instead of the unmanned aerial vehicle 20, and is also called a Faraday cage. The cage 10 is disposed around (outside) the unmanned aerial vehicle 20, surrounding the unmanned aerial vehicle 20 at a distance that does not interfere with the flight of the unmanned aerial vehicle 20 located inside. The cage 10 may have, for example, a lattice-like shape using a conductor such as wire. The overall shape of the cage 10 may be any shape, such as an ellipse, a sphere, or a polyhedron. The Faraday cage effect created by surrounding the unmanned aerial vehicle 20 with the cage 10 ensures a predetermined level of lightning resistance for the unmanned aerial vehicle 20.

[0015] The cage 10 is provided with a conductive cable 11 (grounding wire) for conducting a lightning current that has struck the cage 10 to a lightning current suppression device 30 arranged on the ground.

[0016] The cage 10 has an attachment portion 12 for attaching and fixing the cage 10 to the unmanned aerial vehicle 20, and is connected to the unmanned aerial vehicle 20 via the attachment portion 12. The attachment portion 12 is, for example, an insulating rod member, and is connected between one point (part) of the cage 10 and one point (part) of the unmanned aerial vehicle 20. The attachment portion 12 may be made of multiple rod members connected to multiple points on the unmanned aerial vehicle 20.

[0017] The lightning current suppression device 30 is connected to the cage 10 via the conductive cable 11 and is a device for suppressing lightning current that strikes the cage 10. The lightning current suppression device 30 of this embodiment is placed on the ground. This improves the lightning resistance of the cage 10 and the unmanned aerial vehicle 20 while maintaining the cage 10 in a lightweight state, thereby reducing the risk of the unmanned aerial vehicle 20 crashing due to a lightning strike. In other words, by increasing the impedance of the path through which the lightning current flows, the current flowing to the cage 10 is suppressed, and the lightning resistance of the unmanned aerial vehicle 20 is improved while remaining lightweight, thereby reducing the risk of failure.

[0018] 2 is a diagram showing an example of the configuration of the lightning current suppression device 30. The illustrated lightning current suppression device 30 includes a switching unit 31 and a suppression unit 35.

[0019] The switching unit 31 is connected to the cage 10 that surrounds the unmanned aerial vehicle 20 via a conductive cable 11. The illustrated switching unit 31 includes a switch 32 and a circuit breaker 33. When a lightning current of a predetermined current value or greater flows, the circuit breaker 33 cuts off the path of the lightning current. That is, when a lightning current of a certain value or greater flows, the circuit breaker 33 opens the circuit. When the lightning current is less than the predetermined current value, the circuit breaker 33 functions as a conductor and grounds the lightning current to the ground. The circuit breaker 33 can be, for example, a fuse.

[0020] The switch 32 is activated by a rise in potential due to the lightning current, and switches the lightning current path to the suppression unit 35. In this embodiment, the switch 32 switches the lightning current path to the suppression unit 35 when a voltage equal to or greater than a predetermined voltage value is applied. Specifically, when a lightning current equal to or greater than a predetermined current value flows through the interruption unit 33, the lightning current path is interrupted and the potential due to the lightning current rises. This activates the switch 32 to turn on, and switches the lightning current path from the switching unit 31 to the suppression unit 35. This operation of the switch 32 causes the lightning current to flow to the suppression unit 35. The switch 32 can be formed using an element such as a GDT (Gas Discharge Tube).

[0021] The suppression unit 35 suppresses the lightning current. Specifically, the suppression unit 35 includes an impedance circuit 36. That is, the suppression unit 35 is a circuit with high impedance. The suppression unit 35 suppresses (attenuates) the lightning current flowing through the switch 32 using the impedance circuit 36, and grounds the suppressed lightning current. The impedance circuit 36 ​​is designed taking into account the frequency of the lightning surge (about several MHz). The impedance circuit 36 ​​can be a filter circuit, a resistor, or the like.

[0022] FIG. 3 is a diagram showing the flow of lightning current in the lightning current suppression device 30.

[0023] When lightning strikes cage 10 or unmanned aerial vehicle 20, lightning current flows through path A immediately after the strike, and when a certain level of lightning current flows through path A, interrupter 33 interrupts path A (S1). This causes the voltage applied to switch 32 to rise, causing switch 32 to operate and switch the lightning current path from path A to path B of suppression unit 35 (S2). Suppression unit 35 suppresses the lightning current flowing through path B (S3).

[0024] Specifically, until the lightning current reaches a predetermined value, the cutoff unit 33 functions as a conductor, and the lightning current flows through path A and is grounded to the ground. Then, when the lightning current reaches or exceeds the predetermined value, the cutoff unit 33 cuts off path A. The reason for using the cutoff unit 33 to cut off path A is that if low-impedance path A remains when switching to path B, lightning current will also flow through path A, making it impossible to efficiently suppress the lightning current. In other words, this reduces the lightning current suppression effect. In this embodiment, by using the cutoff unit 33 to cut off path A of the switching unit 31, lightning current flows only through the suppression unit 35.

[0025] When the interrupter 33 interrupts the circuit of path A, the potential due to the lightning current rises, causing the switch 32 to operate and the circuit of the suppression unit 35 to be connected. Specifically, the switch 32 operates (the switch is turned on) when a voltage equal to or greater than a predetermined value is applied. Therefore, when the voltage applied to the switch 32 reaches a predetermined value, the switch 32 operates and the circuit switches to the suppression unit 35. As a result, the lightning current flows through path B and is suppressed by the suppression unit 35.

[0026] The reason for providing switch 32 is that before a lightning strike, a low impedance makes it easier for lightning to strike cage 10 or unmanned aerial vehicle 20, and after a lightning strike, it is desirable to connect to a high impedance suppression unit 35 to suppress the current.

[0027] 4 shows a voltage waveform 41 and a current waveform 42 in this embodiment, and a comparative current waveform 43. The comparative current waveform 43 is a current waveform of a lightning current when the lightning current suppression device 30 is not provided.

[0028] Voltage waveform 41 is an image of the waveform of the voltage applied to switch 32 of lightning current suppression device 30. In voltage waveform 41, the vertical axis represents the voltage applied to switch 32 (e.g., the voltage across the GDT), and the horizontal axis represents time. Voltage waveform 41 shows that after lightning strikes cage 10, etc. at time t0, the voltage gradually increases slightly due to the resistance of interrupter 33, and then the voltage suddenly rises as interrupter 33 interrupts the circuit, reaching a predetermined voltage at time t1, at which point switch 32 operates and the voltage drops.

[0029] Current waveform 42 is a waveform image of the lightning current flowing through cage 10 and unmanned aerial vehicle 20 (hereinafter, "cage 10, etc."), with the vertical axis representing current and the horizontal axis representing time. Current waveform 42 shows that the lightning current rises after lightning strike at time t0, and then is suppressed by suppression unit 35 at timing t1 when switch 32 is activated, thereby suppressing the lightning current flowing through cage 10, etc. In this way, the increase in impedance prevents the lightning current flowing through cage 10, etc. from exceeding a certain current value. Note that interrupter 33 interrupts the circuit when the lightning current reaches a predetermined current value (just before t1). In this embodiment, interruption of the circuit by interrupter 33 switches the lightning current path to suppression unit 35, and the increase in impedance improves the lightning resistance of cage 10.

[0030] In the current waveform 43 of the comparative example, the lightning current flowing through the cage 10, etc. is not suppressed because the lightning current suppression device 30 is not provided. Therefore, in the current waveform 43 of the comparative example, the lightning current is not suppressed even when it reaches the predetermined current value I1, and rises until it reaches its peak. This increases the risk of damage, malfunction, or crash of the unmanned aerial vehicle 20 due to lightning strikes.

[0031] The lightning current suppression device 30 of this embodiment described above comprises a switching unit 31 and a suppression unit 35. The switching unit 31 comprises a cut-off unit 33 that cuts off the path of the lightning current when a lightning current greater than a predetermined current value flows, and a switch 32 that operates in response to an increase in potential due to the lightning current and switches the path to the suppression unit 35, and the suppression unit 35 suppresses the lightning current.

[0032] According to this embodiment, the lightning resistance of the unmanned aerial vehicle 20 can be improved without strengthening the cage 10. Specifically, in this embodiment, a lightning current suppression device 30 is installed on the ground to suppress lightning current. Therefore, in this embodiment, there is no need to strengthen the cage 10 by thickening the material (frame) or otherwise to improve lightning resistance, and the cage 10 can be made smaller and lighter. Therefore, in this embodiment, it is possible to conserve battery power more than when the cage 10 is strengthened, and the flight time of the unmanned aerial vehicle 20 can be extended.

[0033] In addition, in this embodiment, the impedance can be kept low until lightning strikes the cage 10, etc., and therefore it is possible to prevent a decrease in the probability of successful lightning attraction. Furthermore, in this embodiment, by improving lightning resistance, it is possible to reduce the risk of the unmanned aerial vehicle 20 being damaged or crashing due to a lightning strike.

[0034] <Second embodiment> Figure 5 is an overall configuration diagram of a lightning control system according to the second embodiment. The lightning control system of this embodiment has an unmanned aerial vehicle 20, a cage 10, and a lightning current suppression device 30A disposed within the cage 10. This embodiment differs from the first embodiment in that the lightning current suppression device 30A is disposed within the cage 10 that surrounds the unmanned aerial vehicle 20, but is otherwise similar to the first embodiment.

[0035] Similar to the lightning current suppression device 30 of the first embodiment, the lightning current suppression device 30A of this embodiment includes a switching unit 31 including a switch 32 and a breaker 33, and a suppression unit 35 including an impedance circuit 36. The switching unit 31 is connected to the cage 10 via a conductive cable 13 (conductive wire). The lightning current suppression device 30A of this embodiment also includes a conductive cable 11 (ground wire) for conducting lightning current to the ground (ground structures, ground ground, etc.).

[0036] In this embodiment, as in the first embodiment, the lightning resistance of the unmanned aerial vehicle 20 can be improved without strengthening the cage 10. Specifically, the lightning current suppression device 30A is a device with a simple configuration as shown in Figure 5, and is a device that can be made smaller and lighter. Therefore, even if such a lightning current suppression device 30A is placed inside the cage 10 together with the unmanned aerial vehicle 20, it is possible to conserve the battery of the unmanned aerial vehicle 20 more than if the cage 10 were strengthened, and the flight time of the unmanned aerial vehicle 20 can be extended.

[0037] In addition, in this embodiment, the impedance can be kept low until lightning strikes the cage 10, etc., and therefore it is possible to prevent a decrease in the probability of successful lightning attraction. Furthermore, in this embodiment, by improving lightning resistance, it is possible to reduce the risk of the unmanned aerial vehicle 20 being damaged or crashing due to a lightning strike.

[0038] The present disclosure is not limited to the above-described embodiment and modified examples, and various modifications are possible within the scope of the gist thereof.

[0039] 10: Cage (Faraday cage) 11, 13: Conductive cable 12: Mounting part 20: Unmanned aerial vehicle (drone) 30, 30A: Lightning current suppression device 31: Switching part 32: Switch 33: Breaker part 35: Suppression part 36: Impedance circuit

Claims

1. A lightning current suppression device comprising a switching unit and a suppression unit, wherein the switching unit comprises: a cut-off unit that cuts off the path of the lightning current when a lightning current of a predetermined current value or more flows; and a switch that operates in response to a rise in potential caused by the lightning current and switches the path to the suppression unit, and the suppression unit suppresses the lightning current.

2. The lightning current suppression device according to claim 1, wherein the switch switches the path to the suppression unit when a voltage equal to or greater than a predetermined voltage value is applied.

3. The lightning current suppression device according to claim 1, wherein the suppression unit comprises an impedance circuit.

4. The lightning current suppression device according to claim 1, wherein the switching unit is connected to a cage surrounding the unmanned aerial vehicle via a conductive cable.

5. The lightning current suppression device according to claim 1, wherein the lightning current suppression device is placed on the ground, and the switching unit is connected to a cage that surrounds the unmanned aerial vehicle via a conductive cable.

6. The lightning current suppression device according to claim 1, wherein the lightning current suppression device is disposed in a cage surrounding the unmanned aerial vehicle, and the switching unit is connected to the cage via a conductive cable.

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