JP6004432B2 - Lightning striker using laser plasma - Google Patents

Description

  The present invention relates to a lightning striker device that is applied to ground equipment such as lightning rods and wind turbines for wind power generation in order to reduce damage caused by lightning strikes, and particularly to laser lightning strikers for guiding lightning strikes and reliably grounding lightning currents to the ground. The present invention relates to a lightning striker device that enables effective lightning strikes by a plasma atmosphere generated by light irradiation.

In order to prevent lightning strikes, it has been used for a long time to make lightning strikes by installing lightning rods on steel towers and high-rise buildings and grounding them to the ground.
As a technology to further develop these lightning rods and actively guide lightning, plasma lightning rods, rocket lightning devices that perform lightning strikes by driving rockets with wires into thunderclouds, lasers between thunderclouds and lightning towers A laser-induced lightning device or the like has been proposed that ionizes air to form a plasma atmosphere by ionizing air and induces lightning in the plasma atmosphere.

  A plasma lightning rod is an electrode that generates high voltage around the lightning rod and induces lightning by generating plasma. Instead of guiding a long distance like a rocket-induced lightning or laser-induced lightning, a lightning rod Plasma can be generated by discharge or the like in the vicinity of the lightning, and lightning coming to the vicinity of the lightning rod can be guided to the lightning rod.

Regarding the plasma lightning rod, the following Patent Literatures 1 and 2 are known, and further, the following Patent Literature 3 is known as a plasma lightning protection device for protecting the wind turbine blade of the wind power generator.
Patent Document 4 below describes a laser induced lightning device, Patent Document 5 below describes a discharge induction device, Patent Document 6 below describes discharge induction by a laser, and Patent Document 7 below describes discharge induction using a hybrid laser. Respectively.

JP 2007-149622 A Japanese Patent No. 4411389 Japanese Patent No. 4695482 Japanese Patent Laid-Open No. 5-67498 Japanese Patent No. 4806111 Japanese Patent No. 4587382 Japanese Patent No. 4641216

  As shown in FIG. 10, the conventional laser induced lightning is one that is ionized by irradiating a laser beam to the atmosphere, and induces lightning to the ionized portion to cause a lightning strike. Since the laser irradiation device and the induced lightning current are electrically disconnected, the laser irradiation device, etc. will not be damaged by lightning strikes. In this case, a laser transmitter that is difficult to handle must be used, which is expensive and impractical.

On the other hand, as shown in FIG. 11, the plasma lightning rod is provided with an electrode to which a high voltage is applied around the lightning rod to form a discharge gap and generate plasma to induce lightning. The device itself is inexpensive and the installation cost can be reduced.
Also, unlike laser-induced lightning, it does not induce distant lightning in a contact manner, and if a lightning stepped leader or the like is approaching nearby, lightning will surely strike a lightning rod or receptor instead of other places. The main purpose is to guide them.

For this reason, power consumption is also low, for example, it is possible to guide the lightning strike to a lightning striker attached to a windmill blade installed in a wind power plant, and to protect the windmill body from lightning strikes.
However, even if the lightning rod is designed to flow lightning current smoothly to the ground side, the electrical circuit that composes the plasma generator is connected to the lightning current at least on the ground side. It is impossible to isolate them.
In addition, since an electric circuit constituting the plasma generator must be installed in the immediate vicinity of a lightning rod through which a lightning current flows, there is a very high possibility that a lightning will cause a short circuit due to a large current and damage.

This is because even if a lightning current does not flow directly into the electric circuit constituting the plasma generator, a large electromotive force is generated in the electric circuit due to an induced electromotive force when a large current flows by the side.
For this reason, even if a lightning strike can be successfully induced once, the reliability of continuous use is low, and the second lightning strike cannot be induced, or repair or maintenance such as circuit replacement is required each time the lightning strikes.
In addition, plasma lightning rods need to ionize air by discharge, so it is necessary to generate high frequency and high voltage, and discharge reliably under conditions that are unfavorable for electrical discharge such as strong winds and rain. Is difficult and unreliable.

  Therefore, an object of the present invention is to provide a lightning strike device that can effectively and surely induce lightning strikes while taking advantage of the advantages of laser lightning strikes and plasma lightning rods, and that is low in cost and does not generate damage due to lightning strikes in principle. It is to provide.

To achieve the above object, lightning strikes apparatus of the present invention is an induced lightning device to induce lightning, and a and a laser device made of metal induced lightning portion provided in the vicinity of the opening, the condenser lens By irradiating a laser beam so as to focus on the surface of the lightning striker, the metal constituting the lightning striker is turned into plasma, and a plasma flow is ejected from the lightning striker, thereby opening the opening. A three-dimensional lightning atmosphere was ejected from the club.

  In the above lightning strike device, the surface of the lightning strike portion is irradiated with laser light from a laser transmitter provided on the ground via an optical fiber made of an insulating material.

  In the above described lightning striker, the lightning striker is attached to a lightning striker attached to a blade of a wind power generator, and laser light from the laser transmitter provided on the ground is light provided on a rotating shaft of the windmill. The lightning receiving part is irradiated with the optical fiber through a rotary connector.

  In the above-described lightning strike device, an injection device that injects gas from the laser irradiation portion of the lightning strike portion toward the opening portion is provided.

  According to the present invention, plasma can be generated efficiently even with a low-power laser by irradiating laser light so as to focus on the surface of the lightning striker via the condenser lens. Unlike a high-power laser that is used in the conventional laser-induced lightning that is guided inside, lightning can be triggered by using a commercial laser with an output of only 0.1 J.

Since there is no electrical circuit around the receptor and its surroundings unlike conventional plasma lightning strikes, there is no concern of circuit damage due to lightning strikes, and multiple lightning strikes are possible.
By using a rare gas, lightning can be induced more efficiently than a plasma lightning rod using air.

According to the present invention, the laser irradiation device can be installed in a place isolated from the lightning rod, and the output laser light is guided to the vicinity of the electrode through the optical fiber made of an insulating material. The irradiation device can be arranged in a state of being completely electrically insulated from the lightning current.
Moreover, since the plasma generation source is only an electrode piece irradiated with laser light, there is almost no risk of the laser plasma lightning striker itself being destroyed even if a current flows through the lightning rod due to a lightning strike. It is also easy to maintain and manage.

That is, the laser plasma of the present invention is not based on electric discharge, but is based on the basic principle that metal is first converted into plasma by laser light, and plasma and ultraviolet rays generated therefrom further ionize the surrounding gas. .
Plasma generated by such laser irradiation has a high temperature (electrons are 10,000 K or more), a high degree of ionization, and abundant charged particles such as electrons.
Moreover, since laser irradiation is at the nanosecond level and plasma generation is at the millisecond level, it is not easily affected by rain or wind. Even if rain, snow, ice or the like adheres to the target metal that makes up the lightning strike, it will only turn into plasma together.

Further, the laser used in the present invention need not be a high-powered and expensive laser as used in conventional laser lightning strikes.
That is, in laser induced lightning, it is necessary to ionize air in the atmosphere using a high-power laser in order to ionize air with a laser. In the present invention, laser light is irradiated to a metal (electrode) target with a lens. Therefore, if the pulse width is sufficiently short, the metal can be converted into plasma with an output of only about 1 mJ.

  If a gas such as air or helium gas, which is a highly conductive rare gas, is jetted from the laser irradiation part of the lightning striker toward the opening, the lightning atmosphere can be further expanded, By using a rare gas having a low discharge start voltage, the lightning effect can be further enhanced.

It is a figure which shows the whole structure of Example 1 applied to the lightning rod. 1 is an enlarged view of a main part of Example 1. FIG. It is a figure which shows the whole structure of Example 2 which added the gas injection apparatus. 10 is an enlarged view of a main part of Example 2. FIG. It is a figure which shows the other example of a metal cylinder part. It is a figure which shows the whole structure of Example 3 with which the windmill blade of wind power generation was mounted | worn. FIG. 10 is a diagram illustrating another example of attachment of the third embodiment. It is a figure which shows the schematic of an experimental apparatus. It is a photograph which shows the state of the discharge which generate | occur | produced with the experimental apparatus. It is a figure explaining the conventional laser induced lightning. It is a figure explaining the conventional plasma lightning rod.

[Example 1]
The lightning strike device using laser plasma according to the present invention is for a lightning strike to protect the device itself from lightning, such as a lightning rod attached to the top of a high-rise building, a steel tower, a communication antenna, etc., a windmill for wind power generation, etc. Although applicable to the whole apparatus provided with a receptor apparatus, FIG. 1 shows the whole structure of Example 1 applied to the lightning rod.

A lightning arrester 2 is provided at the uppermost end of the lightning rod 1, and laser light oscillated from the laser transmitter 3 is introduced through the optical fiber 4. The laser transmitter 3 is controlled by a control device 6 such as a PC to which a detection signal from the lightning discharge detection device 5 is input.
A lightning strike does not occur suddenly, but before that, a discharge called a stepped leader has already begun in the atmosphere. Since these are discharge phenomena, electromagnetic waves are generated and propagated. Therefore, the electromagnetic waves are received by the lightning discharge detection device 5 to inform the control device 6 that a lightning strike may occur soon. When the laser transmitter 3 is activated in response to a command from the control device 5, the laser light is irradiated inside the lightning arrester 2.

  In this way, by connecting the commercially available lightning discharge detection device 5 to the control device 6 and operating the laser transmitter 2 only when the possibility of a lightning strike is high, power consumption can be suppressed to the minimum necessary. .

In FIG. 2, the principal part enlarged view of the lightning arrester 2 of a present Example installed in the uppermost end of the lightning rod 1 is shown.
The lightning striker 2 includes a cylindrical portion 7 made of metal, and is provided with a central opening 7a and an inclined surface 7b as a lightning striker so that the inner diameter of the opening 7a expands downward inside. . When the possibility of a lightning strike is detected by the lightning discharge detection device 5 and the laser transmitter 3 is activated by a command from the control device 5, the laser light passing through the central opening 7 a of the lightning strike device 2 is transmitted by the condenser lens 8. The light is condensed and irradiated so as to focus on the surface of the inclined surface 7b.
When the laser beam condensed by the condenser lens 8 is irradiated onto the inclined surface 7b formed of metal, the metal of the inclined surface 7b is turned into plasma, and simultaneously the surrounding air (oxygen or nitrogen) is turned into plasma, Heat generation and a flow of charged particles (electrons and ions) are generated, and a plasma flow is emitted to the outside from the opening 7a.

As described above, since the plasma flow is blown out from the tip of the opening 7a, an induced lightning atmosphere having a large surface area is formed, and it easily conducts with the stepped leader coming down from the thundercloud to the ground. Can effectively induce lightning strikes.
The inclined surface 7b of the metal cylindrical portion 7 is cut little by little by the laser light emitted from the laser transmitter 3 through the optical fiber 4, and the focal position becomes out of alignment. The focal point can be easily adjusted by moving the position of this unit as an integrated unit.
Further, since the optical fiber 4 is generally formed of an insulating material, the portion surrounded by the dotted line in FIG. 1 is electrically isolated from the lightning rod 1. There is no direct lightning strike, and repeated lightning strikes are possible except for replacement of the worn cylindrical portion 7.

[Example 2]
In the present embodiment, a rare gas having good conductivity is generated from the inside of the metal cylindrical portion 7, and a more powerful plasma flow can be generated.
Therefore, in the second embodiment, as shown in FIG. 3, conductive helium is supplied from the gas supply device 9 such as a pressure tank or a compression pump toward the upper end opening 7 a of the lightning arrester 2 using a pipe 10 or the like. A rare gas such as a gas or a gas such as air is injected and supplied.
This injection supply amount is controlled by a command from the control device 6 as in the case of the laser transmitter 3. When the gas supply device 9 is a rare gas tank such as helium gas, the electromagnetic valve regulator 11 and the gas supply device 9 are used. If is a compression pump, the electric pump is controlled.

  Since the gas supply pipe 10 is also formed of a highly insulating material, the portion surrounded by the dotted line in FIG. 3 is electrically isolated from the lightning rod 1. The gas supply device 9 and the solenoid valve regulator 11 are not directly hit by a lightning strike, and it is possible to repeat lightning strikes except for replacement of the worn cylindrical portion 7.

FIG. 4 shows an enlarged view of the main part of the second embodiment.
The difference from the first embodiment is that a gas supply pipe 10 is installed. A nozzle 10a is attached to the tip of the gas supply pipe 10, and the laser beam on the inclined surface 7b is directed toward the focal point. Erupt. Thereby, the plasma flow discharged | emitted outside from the opening part 7a is further spread | diffused, and it can expand a lightning strike atmosphere. From the nozzle 10a, air may be injected by a compression pump. However, as in the present embodiment, a rare gas with a low discharge start voltage is ejected from a rare gas tank such as helium gas, thereby achieving a higher lightning effect. Can be obtained.

  In this manner, plasma, air, and a rare gas such as helium gas having a low discharge start voltage are blown out from the upper end opening of the metal cylindrical portion 7 of the lightning striker 2. An atmosphere is formed, and it is easy to communicate with the stepped leader that descends from the thundercloud to near the ground, and lightning that occurs after that can be effectively induced.

  In addition, as shown in FIG. 5, without forming the inclined part 7b in the metal cylindrical part 7, it is cylindrical to the end part, the cover 12 is attached to the upper end opening part, and the laser beam is focused on the back surface. By connecting, the plasma flow may be diffused from the openings 7 c arranged in the circumferential direction near the upper end of the metal cylindrical portion 7.

[Example 3]
Conventionally, for wind turbines such as wind power generation, as a lightning strike countermeasure, a method of attaching a lightning-receiving portion (receptor) to each blade end and flowing it to the ground via a rotating shaft and a tower that supports the windmill is the mainstream.
However, the conventional lightning receiving part has low lightning resistance, and depending on the position of the blade at the time of lightning strike, it does not necessarily fall to the lightning receiving part, not only the windmill but also the rotating shaft, tower, and generator. May cause damage. Therefore, in this embodiment, the lightning strike device of the present invention is attached to the light receiving portion at the tip of the blade, and the induced lightning atmosphere formed by blowing out the plasma flow is also obtained by utilizing the rotation of the blade itself. By forming on the circumference along the trajectory, the lightning resistance is further enhanced.

FIG. 6 shows an example of attachment of the wind turbine to the blade. A receptor 14 that receives lightning discharge is attached to the tip of the blade 13. The receptor 14 is made of a conductive metal, and passes a current during a lightning strike to the ground via the conductor 15, the rotating shaft, and the tower. In this embodiment, the receptor 14 is used as a lightning striker.
Laser light from the laser transmitter 2 installed in the tower that supports the windmill is a commercially available optical rotary connector (for example, an optical rotary connector D-90R manufactured by Mitsubishi Cable Industries, Ltd.) attached to the rotating shaft of the windmill. Then, the light is distributed to each blade 13 and guided to the optical fiber 4, condensed by the condenser lens 8, and irradiated so as to focus on the surface of the receptor 14.

As a result, the metal of the receptor 14 and the surrounding air are ionized to form plasma, which is discharged outwardly from the gap between the tip of the blade 13 and the receptor 14 by the upward flow due to heat generation and the centrifugal force of the blade 13. A lightning strike atmosphere can be formed circumferentially at the tip of the lightning, and lightning can be reliably induced.
The point that the lightning discharge detection device 5 is connected to the control device 6 to detect the stepped leader coming down from the thundercloud to the ground and activate the laser transmitter 2 is the same as in the first embodiment. In this embodiment, no rare gas such as helium gas or air is ejected, but a rotary valve for gas is attached to the rotating shaft of the windmill, or a small capacity helium gas tank is installed inside the blade 13. In the same manner as in the second embodiment, the pipe 10 and the electromagnetic valve regulator 11 may be ejected by the control device 6 in conjunction with the operation of the laser transmitter 2.

  In this embodiment as well, the optical fiber 4 and the like are made of a highly insulating material and are electrically isolated, so that not only the windmill but also the rotating shaft, tower, and generator generate direct lightning strikes. It is not received, and it is possible to lightning repeatedly except for replacement of the worn receptor 14.

  FIG. 6 shows an example in which the receptor 14 is installed at the tip of the blade 13, but it may be attached to the side surface of the blade 13 below the tip as shown in FIG. Other configurations are the same as those in the case of being attached to the tip of the blade 13.

FIG. 8 shows a schematic diagram of an experimental apparatus for verifying the effect of each embodiment.
The output side of the high-voltage power supply 56 is connected to the anode 55, and the two cathodes 53 and 54 are arranged at the same distance with respect to the anode 55, that is, arranged in an isosceles triangle with the anode 55 as a vertex. To do.
Here, only the surface of the cathode 53 is irradiated with the laser from the laser transmitter 51 via the condenser lens 52 so as to be focused by the condenser lens 52, and the anode 55 is supplied from the high voltage power source 56. A voltage of 1 kV was applied and the state of discharge was examined. In addition, helium was used as the atmospheric gas, and the pressure was reduced to 0.2 atm so as to facilitate discharge, and was set to be similar even at an applied voltage of 1 kV in relation to the voltage at the time of lightning strike under atmospheric pressure.

  As a result, the laser beam 57 is focused by the lens only on the right cathode, and the plasma 44 in which metal and gas are ionized is generated on the side surface of the cathode 53. As shown in FIG. 9, even in an experiment of more than a dozen times, discharge is generated only in the cathode 53, and the lightning strike is effective by the plasma generated in the cathode 53 formed of a conductive metal by laser irradiation. I was able to confirm that it was done.

As the laser transmitter 51, a YAG laser having an output of about 100 mJ, a wavelength of 532 nm, and a pulse width of about 8 nse was used. Electrons generated from the plasma are accelerated to the anode, so that a discharge path is formed and discharge starts. In this experiment, laser irradiation is only one pulse, but it is necessary to irradiate continuously in the field.
In any of the first and second embodiments, the laser transmitter to be used can be of any type as long as the conditions of the output and the pulse width are satisfied. The reason is that the laser is focused on the metal of the target and plasma is generated, so the energy of the laser is concentrated on the target, so it is efficient and only the laser output and wavelength width are questioned, and the wavelength is not questioned. It is.

On the other hand, in the conventional laser induced lightning, there is no target on which the laser beam is focused in order to ionize the air, and a high-power laser is required to turn the air into plasma, so the types of lasers are also limited. For example, in experiments so far, a TEA carbon dioxide laser and a high-power laser transmitter with an output energy of about 50 J are used, and the maximum is about 4.5 m in a room, CO ₂ laser, and an output of 100 J. An example of successful 10m discharge induction has been reported.
Further, in an example where the induction was actually successful outdoors, a TEA carbon dioxide laser was used, and the output was 1 kJ. According to trial calculations, 2kJ is required to guide lightning 100m.
On the other hand, according to the present invention, it is possible to reduce the output of the laser transmitter used in the conventional laser lightning by 4 digits.

In the experiment, brass was used as the cathodes 53 and 54. However, the metal cylindrical portion 7 and the receptor 14 used as the lightning strike target to be the target of laser irradiation are not limited to brass, and various metals are used. A metal that is thermally weak is optimal. A size of about 1 cm ² is sufficient for the lightning strike. For example, it may be mounted by screwing as a part of the metal cylindrical portion 7 or the receptor 14.

DESCRIPTION OF SYMBOLS 1 .... Lightning core 2 .... Lightning strike device 3 .... Laser transmitter 4 .... Optical fiber 5 .... Lightning discharge detection device 6 .... Control device 7 .... · Metal cylindrical part 8 · · · Condensing lens 9 · · · Gas supply device 10 · · · Pipe for gas supply 11 · · · Solenoid valve regulator 12 · · · Cover 13 · · · Windmill blade 14 · · · ..Receptor (experimental equipment)
44 ... Generated plasma 51 ... Laser device 52 ... Condensing lens 53 ... Cathode that irradiates laser light 54 ... Cathode that does not irradiate laser light 55 ... Anode 56 ... High Voltage power supply 57 ... Laser light

Claims (4)

A lightning strike device that induces lightning strikes,
And a and a laser device made of metal induced lightning portion provided in the vicinity of the opening,
By irradiating laser light so as to focus on the surface of the lightning striker through a condenser lens, the metal constituting the lightning striker is turned into plasma, and a plasma flow is ejected from the lightning striker, thereby A lightning strike device characterized by ejecting a three-dimensional lightning atmosphere from an opening.   The lightning striker device according to claim 1, wherein a laser beam is emitted from a laser transmitter provided on the ground to the surface of the lightning striker via an optical fiber made of an insulating material.   The lightning striker is attached to a lightning striker attached to a blade of a wind power generator, and laser light from the laser transmitter provided on the ground is passed through an optical rotary connector provided on the rotating shaft of the windmill. The lightning strike device according to claim 2, wherein the lightning striker attached to the lightning striker is irradiated with an optical fiber.   The lightning strike device according to any one of claims 1 to 3, further comprising an injection device that injects a gas from the laser irradiation portion of the lightning strike portion toward the opening.

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