Lightning counterattack prevention system of unmanned aerial vehicle nest on power transmission line iron tower

Abstract

According to the lightning counterattack prevention system for the unmanned aerial vehicle nest on the power transmission line iron tower, the nest shell is in insulated connection with the iron tower, the voltage generated when lightning current is discharged to the nest can be directly reduced, the counterattack probability is reduced, meanwhile, a grounding terminal is arranged in a matched mode, the shell is directly connected with a down lead of an iron tower footing, and if redundant lightning current exists, the lightning counterattack probability is reduced. And the down lead is continuously released, so that the safety of the nest is ensured.

Description

Technical Field

[0001] This application relates to the technical field of power transmission, and in particular to a lightning counterattack prevention system for an unmanned aerial vehicle (UAV) nest on a transmission line tower. Background Art

[0002] It has become normal to use UAVs for line inspection on high-voltage transmission lines. However, the endurance of UAVs cannot meet the requirements of long-distance and sustainable line inspection. Therefore, it is of great significance to install a UAV supply device, that is, a UAV nest, on the transmission line tower for sustainable UAV line inspection. Research on UAV frog-style line inspection has been carried out across the country, and UAV nests have been developed and installed on towers to charge UAVs and perform on-site data analysis and processing, achieving certain results and operating experience.

[0003] UAV nests are usually mounted on the tower body or cross-arm of the tower. Since field towers are vulnerable to lightning strikes, shared tower-mounted UAV nests may be affected by direct lightning strikes, induced lightning, and lightning intrusion waves. In fact, double lightning conductors are usually installed on high-voltage transmission lines of 220 kV and above. Due to their shielding effect, whether the shared tower-mounted UAV nest is mounted on the tower head or the tower body, the possibility of lightning shielding failure to strike the nest is very small. The main lightning effects on the nest are induced lightning and lightning intrusion waves. When lightning strikes the tower top, the lightning current after being shunted by the lightning conductor flows into the ground along the tower down-conductor. Due to the existence of the grounding resistance and the distributed inductance of the tower, the potential at the mounting location of the nest rises instantaneously, forming a counterattack on the nest and breaking down the internal insulation of the nest. When lightning strikes the lightning conductor or an adjacent tower of the transmission line, the generated lightning intrusion wave enters the nest along the line, communication antenna, and other connecting wires, affecting the communication and control circuits of the nest. The transient potential rise of the grounding grid caused by lightning strikes has characteristics such as high voltage amplitude and wide frequency range. The generated transient potential is coupled to the core wire through the cable outer sheath and invades the secondary system, severely affecting the secondary equipment. Currently, faults caused by the transient ground potential rise of the grounding grid in the secondary circuit occur frequently. Therefore, it is necessary to consider the protection against lightning counterattacks, induced lightning, and lightning intrusion waves of the nest and construct an effective lightning protection structure for the nest.

[0004] The existing assembly of the nest and the tower is as follows:

[0005] 1. Shared tower-mounted UAV nests are vulnerable to lightning counterattacks, induced lightning, and lightning intrusion waves, which affect the normal operation and safety of the nests. The existing shared tower-mounted UAV nests are directly fixed on the tower, and the metal shell of the nest is directly connected to the tower. When lightning strikes the tower top, the potential of the tower and the shell of the nest at the mounting location rises instantaneously, forming a counterattack on the internal equipment of the nest.

[0006] 2. To prevent lightning from damaging the shared tower-mounted drone nest, a lightning protection and grounding device needs to be set up. In the existing drone nest, the metal shell is connected to the tower on-site. When the lightning current strikes the top of the tower and flows down along the tower, due to the existence of the impact grounding resistance and the distributed inductance of the tower, the ground potential rises, and the potential of the drone nest shell rises transiently, forming a counterattack on the internal power supply and signal weak current equipment of the drone nest, posing a safety hazard.

[0007] The existing lightning protection measures for drone nests only include measures such as installing lightning rods to prevent direct lightning strikes. This is a common technical means in this field and is also a generally recognized and effective solution. Summary of the Invention

[0008] This application proposes a lightning counterattack prevention system for a drone nest on a transmission line tower, which can at least solve one of the technical problems existing in the background technology.

[0009] To achieve the above object, this application adopts the following technical solutions: [[ID=1--3]]

[0010] This application provides a lightning counterattack prevention system for a drone nest on a transmission line tower. The lightning counterattack prevention system includes:

[0011] An insulating component that realizes the insulating assembly between the drone nest and the tower; and

[0012] A grounding terminal provided on the outer shell of the drone nest, and the grounding terminal is connected to the grounding lead at the tower base of the tower through an insulating copper wire.

[0013] Based on the above technical solutions, the insulating connection between the drone nest shell and the tower can directly reduce the voltage when the lightning current flows down to the position of the drone nest, reducing the probability of counterattack. At the same time, with the cooperation of the grounding terminal, the shell is directly connected to the grounding lead of the tower base. If there is excess lightning current, it will continue to be released through the lead to ensure the safety of the drone nest.

[0014] Optionally, the insulating component is a steel structure support frame equipped with ceramic insulators and assembled with the tower, and the ceramic insulators are assembled with the drone nest.

[0015] Optionally, the diameter of the insulating copper wire is 6 mm, the height of the ceramic insulator is 20 cm, and the creepage distance is 30 cm.

[0016] Optionally, the lightning counterattack prevention system further includes:

[0017] A surge protector SPD component provided at the power inlet and / or data communication interface of the drone nest.

[0018] Optionally, the drone nest is powered by a wind turbine, and the lightning counterattack prevention system further includes:

[0019] An SPD component is provided at the incoming line end of the wind turbine or at the high voltage side of the transformer.

[0020] Optionally, the SPD component is an SPD component with at least two stages of SPDs connected in parallel.

[0021] Optionally, a decoupler is provided between two adjacent stages of SPDs.

[0022] Optionally, the SPD properties, decoupler properties, and intrusion wave speed-up conditions meet the following conditions:

[0023] The forward voltage of the primary SPD is greater than that of the secondary SPD;

[0024] The decoupler isolation inductance, the intrusion wave speed, the on-state voltage of the secondary SPD, and the on-state voltage of the primary SPD satisfy a first preset condition;

[0025] The limiting voltage after the primary SPD is turned on, the isolation inductance value of the decoupler, the speed of sound of the intrusion wave, and the turn-on voltage of the secondary SPD meet the second preset condition; and

[0026] The decoupler isolation inductance, the maximum breakdown voltage of the gas gap, the second SPD residual voltage, and the intrusion wave speed meet a third preset condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the placement of the engine nest, wind turbine and tower provided in an embodiment of the present application;

[0028] Figure 2 This is a schematic diagram of the machine nest placement method provided in an embodiment of the present application;

[0029] Figure 3 This is a schematic diagram of a steel structure support frame with ceramic insulators provided in an embodiment of the present application;

[0030] Figure 4 This is a schematic diagram of the primary SPD protection provided by an embodiment of the present application;

[0031] Figure 5 This is a schematic diagram of the secondary SPD protection provided by an embodiment of the present application;

[0032] Figure 6 This is a schematic diagram of the secondary SPD protection plus decoupling elements provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0034] It should be noted that:

[0035] In the description of this application, it is understood that, unless otherwise specified or limited, the terms "installed," "connected," "connected," and "connected" should be understood broadly. For example, "connected" can be a detachable or non-detachable connection; a direct connection or an indirect connection through an intermediate medium; an electrical connection or a mechanical connection. "Fixed connection" refers to being connected to each other and maintaining a constant relative position after connection. Furthermore, two components forming an integrated structure through an integral molding process means that, during the formation of one of the two components, the component is connected to the other component without requiring further processing (such as bonding, welding, snap-fit connection, or screw connection) to connect the two components. Component A and component B can be arranged relative to each other so that component A is projected along a target direction to obtain projection C, and component B is projected along the target direction to obtain projection D, and projections C and D can at least substantially overlap. In some embodiments, the substantial overlap can be any of the following: projection C is completely within projection D. Alternatively, projection D is completely within projection C. Alternatively, projection C and projection D intersect with each other, and the intersection area of projection C and projection D accounts for more than 50% of projection C or projection D.

[0036] The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inner", "outer", etc., are only used to refer to the directions in the drawings. Therefore, the directional terms used are for better and clearer description and understanding of the embodiments of the present application, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the embodiments of the present application. For those skilled in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0037] This application will present various aspects, embodiments, or features in the context of systems including multiple components, units, modules, etc. It should be understood and appreciated that each system may include additional components, units, modules, etc., and / or may not include all of the components, units, modules, etc. discussed in conjunction with the figures. Furthermore, combinations of these aspects may also be used.

[0038] Additionally, in the examples of this application, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary" in this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplarily" is intended to present concepts in a concrete manner.

[0039] In the embodiments of the present application, (multiple words) can sometimes be used interchangeably. It should be noted that when the difference is not emphasized, their intended meanings are the same. "(of)", "corresponding", and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference is not emphasized, their intended meanings are the same.

[0040] Exemplarily, as Figure 1-6 shown, the embodiments of the present application provide a lightning counterattack prevention system for an unmanned aerial vehicle nest on a shared transmission line tower. The specific solution is as follows:

[0041] 1. Voltage at the installation location of the nest when the tower top is struck by lightning

[0042] Taking the cup-shaped tower of a 220KV line carrying the nest as an example, the nest 200 is directly connected to the tower 100 and installed at a height of h meters from the ground, as Figure 1 shown. When the top of the tower is struck by lightning, the potential U of the nest carried on the tower jc is calculated according to the following formula:

[0043] U jc = βI L (R ch + hL gt / 2.6)

[0044] In the formula, I L is the lightning current amplitude in kA, β is the lightning protection wire shunt coefficient, taking 0.9; R ch is the impulse grounding resistance of the tower in Ω, L gt is the equivalent inductance of the tower, taking 0.5 μH / m, and h is the position height in (m).

[0045] If the lightning current is taken as 52 kA, the impulse grounding resistance is taken as 4 Ω, and h is taken as 20 meters, then when the lightning current discharges downward, the potential of the metal shell of the nest reaches 367.2 kV. Obviously, this transient high voltage will cause a counterattack to the electronic equipment in the nest, causing the equipment to have an overvoltage and insulation breakdown.

[0046] The lightning protection measures are as follows:

[0047] (1) Strengthen the internal insulation level of the nest so that it will not be broken down by overvoltage when the lightning current discharges downward and the shell potential rises;

[0048] (2) Adopt a 1:1 isolation transformer on the power supply incoming line to isolate the counterattack voltage, and similar measures can also be taken for the signal line;

[0049] (3) Install a surge protector to shunt and limit the amplitude to protect the internal equipment of the nest.

[0050] 2. Lightning counterattack prevention plan for the nest

[0051] To reduce the probability of lightning counterattack of the nest, an insulating connection is made between the outer shell of the nest and the iron tower. A grounding terminal is set on the outer shell of the nest and directly connected to the downlead at the base of the iron tower. Among them, the insulating connection between the outer shell of the nest and the iron tower is the most important, which can directly reduce the voltage when the lightning current discharges to the position of the nest, thus reducing the probability of counterattack. At the same time, in cooperation with the setting of the grounding terminal, the outer shell is directly connected to the downlead at the base of the iron tower. If there is excess lightning current, it will continue to be discharged through the downlead to ensure the safety of the nest.

[0052] (1) Insulating connection between the nest and the iron tower

[0053] The steel structure support frame is used to fix the nest on the iron tower. It consists of two horizontal crossbeams, two vertical rods and diagonal rods to form a triangular structure, as Figure 2 shown. One side of the horizontal crossbeam and the vertical rod are used to connect and fix with the iron tower; the other side of the horizontal crossbeam and the vertical rod are used to fix the nest.

[0054] Support insulators are installed between the nest and the steel support frame. The air gap between the outer shell of the nest and the support frame is taken as 20 cm, and the air gap from the iron tower is greater than 20 cm. The support insulators adopt ceramic insulators, which have high mechanical strength, taking 100 - 200 kN, meeting the requirements of supporting and fixing the nest. The creepage distance of the insulator is greater than 30 cm, and the flashover voltage is greater than 200 kV.

[0055] (2) Setting of the grounding wire of the nest

[0056] A grounding terminal is set on the outer shell of the nest and directly connected to the grounding downlead of the iron tower base with an insulated copper wire with a diameter of not less than 6 mm; the grounding resistance of the pole tower should be less than 4 Ω.

[0057] (3) If the nest has an external power supply, a surge protector is installed at the power inlet of the nest, and at the same time a surge protector is installed at the data communication interface of the nest, so that the counterattack voltage can be quickly bypassed to protect the internal equipment of the nest.

[0058] Adopting the above installation method of the nest, if the hanging height of the nest is 15 meters, the impulse grounding resistance of the pole tower is 4 Ω, when lightning strikes the top of the tower, the lightning current is set as 50 kA, the potential of the pole tower at the installation position of the nest is:

[0059] U t =βI L (R ch +hL gt / 2.6)=0.9×50×(4 + 15×0.5 / 2.6)=309.8 kV

[0060] And the potential of the nest is the ground potential: U jc =βI L R ch =0.9×50×4=180 kV

[0061] Adopting an insulated connection, when the lightning current discharges downward, the voltage rise of the nacelle housing is only 180 kV, greatly reducing the probability of back-strike and the requirement for the internal insulation level of the nacelle. At the same time, the voltage between the nacelle housing and the iron tower is only 129.8 kV, far less than the insulation strength between the nacelle and the iron tower, and there will be no air breakdown and insulator flashover between the nacelle housing and the iron tower.

[0062] 3. Design of the nacelle insulation structure

[0063] Design a steel structure support frame with ceramic insulators to fix the nacelle on the iron tower. Its shape and dimensions are as Figure 3 ; The nacelle is insulated from the iron tower through the support frame. The air gap between the iron tower and the nacelle housing is greater than 20 cm. During the downward discharge of the lightning current, the air insulation between the iron tower and the nacelle housing will not break down, and the support insulators will not flash over.

[0064] The nacelle is provided with a grounding terminal and connected to the grounding lead at the base of the iron tower with insulated copper wire. When the lightning current discharges downward, due to the absence of the voltage caused by the distributed inductance of the iron tower, the potential rise of the nacelle housing is greatly reduced, reducing the probability of back-strike of the weak-current equipment inside the nacelle due to the rise of the ground potential and the requirement for the internal insulation strength of the nacelle.

[0065] The insulator uses a ceramic post insulator, 20 cm high and with a creepage distance of 30 cm, to fix the unmanned aerial vehicle nacelle.

[0066] The steel structure support frame adopts a triangular structure, and the length of the cross beam can be increased or shortened according to the structure of the iron tower. Both the cross beam and the vertical rod are fixed to the iron tower with screws.

[0067] The grounding wire of the nacelle housing uses insulated copper wire and is connected to the grounding lead at the base of the iron tower.

[0068] 4. Lightning protection and back-strike prevention plan for the wind turbine

[0069] After a lightning strike, the lightning electromagnetic pulse invades the power system through various channels, thus causing overvoltage and damaging electronic equipment. In the analysis of the second part, if the suspension height is 15 m, the tower potential at the installation position of the transmission tower nacelle reaches 309.8 kV, which will surely have a significant impact on the wind turbine 300 that supplies power to the unmanned aerial vehicle nacelle, as Figure 1 shown. The main measure for internal lightning protection of the wind turbine is to install surge protectors (SPDs) at key positions such as the incoming line end of the generator. When lightning or overvoltage occurs, the SPD will quickly act, clamp the voltage within a safe range, and discharge the lightning energy to the ground to prevent equipment damage.

[0070] 5. SPD protection plan design

[0071] AsFigure 4 As shown, using a single SPD (a primary SPD) can provide basic lightning protection, but installation should be performed at the most critical point, either at the wind turbine generator line input or on the high-voltage side of the transformer. However, a single primary SPD alone cannot completely eliminate lightning energy; some surges may enter equipment and affect the electrical system. Furthermore, the high clamping voltage of a single SPD can lead to significant residual voltage, potentially damaging delicate equipment. Wind turbines on shared towers face a high lightning risk, so a multi-stage SPD solution should be considered to improve system safety.

[0072] The lightning protection effectiveness of multi-stage surge protectors (SPDs) is affected by many factors. Protecting against lightning surges is a crucial component of the overall lightning protection project. The GB50057-2010 standard specifies the installation of SPDs on low-voltage distribution lines in various types of lightning protection structures and provides installation requirements for each SPD level. However, the standard does not provide an operational method for inter-stage coordination of multi-stage SPDs suitable for equipment mounted on shared towers. This example proposes a preferred method for selecting and installing multi-stage SPDs for wind turbines on transmission towers.

[0073] According to traveling wave theory, the speed of wave propagation in the line is:

[0074]

[0075] Where L0 represents the inductance per meter of the conductor with the ground as the loop, C0 represents the capacitance per meter of the conductor to the ground, and v represents the propagation velocity.

[0076] In the multi-level lightning protection scheme of low-voltage distribution systems, a hierarchical coordinated protection strategy is usually adopted. The first-level protection generally uses a voltage-switching SPD, which is used to quickly discharge the large-scale surge current generated by lightning strikes; the secondary protection is configured with a voltage-limiting SPD (such as a metal oxide varistor MOV), which achieves voltage clamping through nonlinear impedance characteristics, thereby ensuring that the terminal voltage of the protected equipment is within the safety threshold range, such as Figure 5 shown.

[0077] The MOV reaction time is about 25ns, but the discharge gap time is about 100ns. In order to ensure that the first-level protection is activated before the second-level protection, the discharge gap should be activated before the surge reaches the MOV. Taking a common power cable as an example, the propagation speed of the lightning shock wave is v = 1.75×108m / , and the time difference between the first-level SPD and the secondary SPD reaction action is T = (100-25)ns. During this time, the propagation distance of the lightning shock wave is s = vt = 1.75×10 8 ×75=13.13m.

[0078] According to the above analysis, to ensure the correct operation of multi - stage SPD protection, the distance between devices should be at least 13.13 m. Obviously, the distance between the wind turbine mounted near the nacelle and it cannot be more than 15 m. The coiled wire can be used to reduce the space and achieve the distance for multi - stage protection operation. However, after coiling into loops, the insulation problem between loops under impulse voltage is greatly increased. Obviously, this method is not applicable on shared iron towers. Therefore, special requirements need to be put forward for the design of multi - stage SPD. This patent uses a decoupler to achieve the purpose of stage - to - stage coordination.

[0079] The installation of a decoupler for two - stage SPD coordination is as Figure 6 shown. If the breakdown voltages of the two SPDs are U n1 and U n2 respectively, it is necessary to ensure that U n1 > U n2 to meet the multi - stage coordination principle. After installing the decoupling element, the conduction sequence of multi - stage SPD depends on the following factors:

[0080] (1) Incoming wave rise rate — di / dt;

[0081] (2) The nature (resistance Rs or inductance Ls) of the decoupling element isolation impedance Zn, and their magnitudes.

[0082] When the following conditions are met simultaneously, the correct operation of multi - stage SPD protection can be ensured. Among them, Ures is the limiting voltage after the first - stage SPD conducts, Uf is the maximum breakdown voltage of the gas gap, U2 is the residual voltage of the second - stage voltage - limiting SPD; the incoming wave rise rate di / dt can take 0.1 kA / μs; Ls is the isolation inductance value.

[0083] L s (d i / d t ) + U u2 ≥U n1 (1)

[0084] U res ≥L s (d i / d t ) + U n2 (2)

[0085]

[0086] If the above - mentioned condition (1) is met, the first - stage SPD conducts. If the above - mentioned condition (2) is met, the second - stage SPD conducts. At the same time, the decoupling inductance needs to meet the above - mentioned condition (3).

[0087] The protection mode of multi-level SPD coordination was determined. At the same time, the problem of short distance between drone nest and wind turbine was solved by adding decoupling elements, and a verification method of decoupling elements was provided.

[0088] This embodiment effectively prevents transient high voltages from the tower from hitting the generator nest, caused by rising ground potential during lightning current discharge. It also protects weak current equipment within the generator nest through surge absorption and grounding. It also employs multi-level SPD protection for wind turbines and provides a method for verifying decoupling inductance.

[0089] It can be understood that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other, and any combination of features in different embodiments is also within the scope of protection of the present application. That is to say, the multiple embodiments described above can also be arbitrarily combined according to actual needs.

[0090] It is understood that all the above drawings are illustrative illustrations of this application and do not represent the actual size of the product. The dimensional ratio relationship between the components in the drawings does not serve as a limitation on the actual product of this application. The above are only some of the embodiments and implementation methods of this application. The scope of protection of this application is not limited to this. Any person skilled in the art who is familiar with the technical scope disclosed in this application can easily think of changes or replacements, which should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A lightning counterattack prevention system for a drone nest on a transmission line tower, characterized in that, The lightning counterattack prevention system includes: an insulation component for realizing the insulated assembly between the nacelle and the iron tower; and a grounding terminal provided on the outer shell of the nacelle, and the grounding terminal is connected to the grounding lead at the base of the iron tower through an insulated copper wire.

2. The lightning protection and counterattack system according to claim 1, characterized in that, The insulation component is a steel structure support frame equipped with ceramic insulators and assembled with the iron tower, and the ceramic insulators are assembled with the nacelle.

3. The lightning counterattack prevention system according to claim 2, characterized in that, The diameter of the insulated copper wire is 6 mm, the height of the ceramic insulator is 20 cm, and the creepage distance is 30 cm.

4. The lightning protection and counterattack system according to claim 1, characterized in that The lightning counterattack prevention system further includes: a surge protector SPD component provided at the power inlet and / or data communication interface of the nacelle.

5. The lightning protection and counterattack system according to claim 1, characterized in that The nacelle is powered by a wind turbine, and the lightning counterattack prevention system further includes: an SPD component provided at the incoming line end of the wind turbine or the high-voltage side of the transformer.

6. The lightning protection and counterattack system according to claim 4 or 5, characterized in that, The SPD component is an SPD component with at least two stages of SPDs connected in parallel.

7. The lightning protection and counterattack system according to claim 6, characterized in that, A decoupler is provided between two adjacent stages of SPDs.

8. The lightning protection and counterattack system according to claim 7, characterized in that, The SPD attributes, decoupler attributes, and the rising speed of the incident wave satisfy the following conditions: The conduction voltage of the first-stage SPD is greater than the conduction voltage of the second-stage SPD; The isolation inductance value of the decoupler, the sound speed of the incident wave, the conduction voltage of the second-stage SPD, and the conduction voltage of the first-stage SPD satisfy a first preset condition; The clamping voltage after the first-stage SPD conducts, the isolation inductance value of the decoupler, the sound speed of the incident wave, and the conduction voltage of the second-stage SPD satisfy a second preset condition; and The isolation inductance value of the decoupler, the maximum breakdown voltage of the gas gap, the residual voltage of the second SPD, and the sound speed of the incident wave satisfy a third preset condition.

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