Mooring type unmanned aerial vehicle robot for power cable deicing and control method

Abstract

The invention discloses a mooring type unmanned aerial vehicle robot for deicing a power cable and a control method, and aims to improve the convenience, accuracy and efficiency of deicing operation of a power transmission line. The mooring type intelligent unmanned aerial vehicle robot for power cable deicing comprises an unmanned aerial vehicle, a case and a cable connecting the case and the unmanned aerial vehicle, the case provides power for the unmanned aerial vehicle through the cable, at least one of a storage battery, a power generation device or power connection equipment is arranged in the case, a cable take-up and pay-off device is arranged in the case, and the cable take-up and pay-off device is connected with the unmanned aerial vehicle through the cable. The take-up and pay-off device is used for adjusting the length of the cable between the unmanned aerial vehicle and the case.

Description

Technical Field

[0001] The present invention relates to the field of intelligent power maintenance technology, and in particular to a tethered drone robot and a control method for deicing power cables. Background Art

[0002] The stability of transmission line operation is an important guarantee for the electricity use of residents and enterprises. Some transmission lines are installed in cold areas or in extreme weather conditions such as freezing rain, and ice will form on the surface of the transmission lines. However, when too much ice presses on the transmission lines, the lines will be crushed, affecting power supply and use. In addition, since transmission lines are generally installed at high altitudes and some lines cross between mountains, extreme weather and unchanged traffic conditions make it inconvenient to carry out traditional manual de-icing operations.

[0003] However, in extreme weather, people have extremely high requirements for stable power transmission, such as for medical treatment, heating for people's daily lives, normal operation of enterprises and communications. Therefore, in this case, it is necessary to provide a quick and efficient de-icing and liberation solution to maintain normal power supply.

[0004] In some schemes, the use of drones for de-icing operations is proposed. Drones are flexible and can quickly reach the required location even in extreme environments. The de-icing methods used in these schemes are generally machine-type de-icing and heating-melting de-icing, but the typical disadvantages of these solutions include: 1. The drone has a short battery life. It relies on its own battery to work and can usually only maintain a battery life of about 30 minutes; 2. The battery support capacity is low. Mechanical or hot-melt de-icing requires a lot of power consumption, which is difficult for the drone's own battery to bear; 3. It is difficult to connect to power lines. In extreme weather, it is difficult for drones to accurately connect cables; 4. The efficiency is low. The first reason for the low efficiency is the limited battery problem, and the second is that usually only one transmission line can be de-iced, while conventional transmission lines generally have three lines. Summary of the invention

[0005] The object of the present invention is to provide a tethered drone robot and a control method for deicing power cables, so as to improve the convenience, accuracy and efficiency of deicing operations of power transmission lines.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A tethered intelligent drone robot for deicing power cables, comprising a drone, a chassis, and a cable connecting the chassis and the drone, wherein the chassis provides power to the drone via the cable, wherein the chassis includes at least one of a battery, a power generation device, or a power connection device, and wherein a cable retracting device is provided in the chassis, wherein the retracting device is used to adjust the length of the cable between the drone and the chassis; The UAV includes a body and propellers. The propellers are at least four groups and are distributed at the outer end of the body to provide lift for the entire UAV. The body has a horizontal U-shaped groove structure. The opening of the U-shaped groove is arranged in the front end direction thereof. At least one deicing device is arranged on the UAV. A docking component is provided between the bottom of the deicing device and the U-shaped groove. The bottom of the deicing device and the bottom of the body are connected with a second cable, and the second cable is arranged through the lower end of the U-shaped structure.

[0007] Furthermore, a bottom plate is arranged at the bottom of the deicing device, and grooves are provided on both sides of the U-shaped groove, and the width of the grooves can accommodate the bottom plate.

[0008] Furthermore, side panels are provided on both sides of the bottom plate of the de-icing device, positioning grooves are provided on the side panels, and clamping mechanisms are correspondingly provided on both sides of the U-shaped groove. The clamping mechanism includes a hook plate rotatably connected to the main body, a hook plate motor is provided on one side of the hook plate, and a hook block is provided on the top of the hook plate, and the hook block can be cooperated and restricted at the positioning groove.

[0009] Furthermore, the bottom of the hook block is a beveled matching structure at the positioning groove.

[0010] Furthermore, the deicing device includes an upper wheel group and a lower wheel group, and the upper wheel group and the lower wheel group are used to clamp the power transmission line.

[0011] Furthermore, the upper wheel group includes two upper wheels arranged front and rear, a driving motor is arranged inside the upper wheel, and the lower wheel is arranged below the two upper wheels. The lower wheel is a single-sided wheel structure, which is installed through the cooperation of a rotating shaft, a slider and a straight groove of the side plate. A servo electric cylinder is arranged between the bottom plate and the slider. The servo electric cylinder is used to adjust the height of the lower wheel at the side plate. The upper wheel and the lower wheel are both bull horn wheel structures, and their wheel surfaces have an anti-slip pattern structure.

[0012] Furthermore, a mounting plate is arranged between the two upper wheels, and a deicing mechanism is arranged on the mounting plate.

[0013] Furthermore, the de-icing mechanism includes a percussion hammer and a connecting rod, the rear end of the connecting rod is in a rotational connection with the mounting plate, a lifting component is arranged on the mounting plate, the lifting component is used to lift the connecting rod and the percussion hammer so that they can be quickly released downward, and the bottom of the percussion hammer is a serrated blade-like structure.

[0014] A control method, applied to the above-mentioned tethered intelligent drone robot for deicing power cables, comprises: Initially, multiple de-icing devices are arranged in a straight line side by side at the U-shaped groove of the drone, and the de-icing devices and the drone are stably installed through the clamping mechanism. The second cable connects the de-icing devices in series, and they are naturally hung down and passed through the U-shaped groove. The rear end of the de-icing devices is arranged at the bottom of the rear end of the U-shaped groove of the drone. The servo electric cylinder adjusts the lower wheel and puts it in the lower end position. Flight operation: The drone carrying the deicing device flies under the power line that needs to be deiced. During this process, the retractable device adjusts the length of the cable and ensures that the cable is connected in an arc structure. De-icing device placement operation: The UAV aligns the open side of the de-icing device with the power line horizontally and moves horizontally toward the power line until the power line of the de-icing device is placed between the upper wheel and the lower wheel. After that, the de-icing lower wheel at the front end performs an upward operation under the control of the corresponding servo cylinder. When the power line is clamped by the upper wheel and the lower wheel of the de-icing device, the UAV performs a backward flight, the de-icing device is detached from the UAV, and the second cable connected to the de-icing device is led out from the front end of the U-shaped groove, and the de-icing device at the rear end continues to remain on the UAV. Repeat the above operation until all de-icing devices are deployed at the corresponding transmission lines; The driving motor drives the upper wheel to rotate forward, and the lifting component of the de-icing mechanism works continuously, so that the hammer strikes the top of the transmission line, forcing the ice on the surface of the transmission line to break and separate. The UAV moves forward synchronously on the side of the transmission line until the ice on the transmission line of this line section is cleared; Perform the de-icing device arrangement operation in reverse, so that all the de-icing devices are collected on the back of the drone in sequence; Perform de-icing operations on the next route segment or return the drone to its initial state.

[0015] Furthermore, the length of the second cable between the two deicing devices is greater than the spacing distance between two adjacent power transmission lines.

[0016] Compared with the existing technology, this solution has the following advantages: This solution is used for a tethered intelligent drone robot for deicing power cables. It adopts a tethered structure, that is, the drone is connected to the chassis by a cable, and the cable can provide power support for the drone to meet the long-term working needs of the drone. The drone does not need to carry bulky batteries, so that the drone can have a greater carrying capacity. At the same time, in order to cope with operations such as mechanical deicing or hot melt deicing that require a large amount of power support, continuous power support can be achieved through the cable, thereby improving the efficiency and durability of the drone deicing operation, and being able to achieve deicing operations on multiple line sections at one time; This solution uses multiple deicing devices to work synchronously to implement deicing operations. The drone carries multiple deicing devices and releases them in sequence to perform synchronous deicing operations on multiple transmission lines in the line section, thereby improving the deicing efficiency, which is more than three times the efficiency of traditional single-machine operation. The UAV of this solution adopts a U-shaped groove structure, and the second cable of the de-icing device can be retracted and released through the opening of the U-shaped groove. Therefore, even at high altitudes, the second cable can be used smoothly, which can prevent the cable from colliding with the UAV blades and propellers, greatly improving the flight stability of the UAV; This solution is a control solution for a tethered intelligent drone robot for de-icing power cables. Through positioning and visual operation structures, the de-icing device can accurately and efficiently connect and separate transmission lines at high altitudes, thereby achieving continuous and efficient de-icing operations of multiple de-icing devices. It has the characteristics of simple, accurate, reliable operation, and high de-icing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of a preferred embodiment.

[0018] Figure 2 Schematic diagram of the structure layout of the UAV and de-icing device.

[0019] Figure 3 This is a schematic diagram of the structure of the drone in an empty state.

[0020] Figure 4 This is a schematic diagram of the de-icing device structure.

[0021] Figure 5 This is a schematic diagram of the working status of the de-icing device.

[0022] Figure 6 This is a schematic diagram of another working state of the de-icing device.

[0023] Figure 7 Arrange a schematic diagram of the operating status of the de-icing device.

[0024] Figure 8 This is a schematic diagram of the overall synchronous working status of the de-icing device. DETAILED DESCRIPTION

[0025] The original intention of this scheme is to provide a tethered UAV, and use the tethered UAV to carry multiple de-icing mechanisms to implement efficient de-icing operations on transmission lines. Through the tethered UAV, the operator can perform operations without going under the transmission line or tower. Through the support of the tethered structure and chassis power, long-term and efficient transmission line de-icing operations can be achieved.

[0026] refer to Figures 1 to 3The tethered intelligent drone robot for deicing power cables includes a drone 1, a chassis 2, and a cable 20 connecting the chassis 1 and the drone 2. The chassis 1 provides power to the drone 1 through the cable 20. The chassis 1 includes at least one of a battery, a power generation device, or a power connection device for providing power for a long time. In some embodiments, the chassis 1 can be a vehicle-mounted structure or a part of a vehicle, and can rely on the power generation function of the vehicle to achieve long-term power supply.

[0027] A cable retracting device 21 is provided in the chassis 1. The cable retracting device 21 has a controllable cable reel and a winding mechanism, and can retract or release the cable 20 according to the actual position and height of the drone 1. The cable 20 adopts a flexible and lightweight structure. However, in actual use, the cable 20 needs to control an arc-shaped structure to reduce the pulling on the drone 1 during flight and prevent the cable 20 from being interfered with by foreign objects such as tree branches as much as possible.

[0028] The drone 1 includes a body 11 and propellers 12. The propellers 12 can be four, six or eight groups arranged in a central array. There is an open structure in front of the propellers. The propellers are distributed at the outer end of the body 11 through arms to provide lift for the entire drone 1. The body 1 has a horizontal U-shaped groove 13 structure. The opening of the U-shaped groove 13 is arranged in front of the body 11. Three de-icing devices 3 are arranged on the drone 1. A docking component 4 is provided between the bottom of the de-icing device 3 and the U-shaped groove. The bottom of the de-icing device 3 and the bottom of the body 11 are connected with a second cable 22. The second cable 22 is suspended at the lower end of the U-shaped groove 13.

[0029] The drone 1 has built-in structures such as a sensor system, a flight control system, an imaging system and a positioning system. It can achieve stable flight and flight control according to its internal controller, execute the coordination instructions of the body controller, and send the real-time video captured by the camera to the operator's control terminal to achieve corresponding precise operations.

[0030] refer to Figures 4 to 6 A bottom plate 31 is arranged at the bottom of the de-icing device 3, and grooves 14 are provided on both sides of the U-shaped groove 13. The horizontal width of the groove 14 can just accommodate the bottom plate 31, and the bottom plate 31 can be aligned and flatly mounted on the groove 14. The second cable 22 is connected to the bottom of the bottom plate 31, and the second cable 22 is freely suspended through the U-shaped groove 13.

[0031] Side panels are provided on both sides of the bottom plate 31 of the de-icing device 3, which are a left side panel 32 and a right side panel 33. The height of the right side panel 33 is lower than that of the left side panel 32. Positioning grooves 34 are arranged at the same height above the bottom plate 31 on the left side panel 32 and the right side panel 33. A clamping mechanism is provided on both sides of the U-shaped groove 13. The clamping mechanism includes a hook plate 15 rotatably connected to the main body 11. A hook plate motor 16 is provided on one side of the hook plate 15. A hook block 17 is provided on the top of the hook plate 15. The hook block 17 can be cooperated and restricted in the positioning groove 34. Through the hook blocks 17 and the grooves 14 on the left and right sides, the side panels, the bottom plate 31 and the entire de-icing device 3 are firmly arranged on the fuselage 11.

[0032] In some embodiments, the bottom of the hook block 17 is a sloped structure, and the positioning groove 34 is also a sloped matching structure, so the hook blocks 17 on both sides form an inward embracing structure, realizing a self-locking function in a fixed state, which greatly improves the stability of the de-icing device 3 in the fuselage 11, and can maintain the stability of both even under certain wind conditions.

[0033] The de-icing device 3 comprises an upper wheel group 36 and a lower wheel group 35, and the upper wheel group 36 and the lower wheel group 35 are used to clamp the power line and realize the arrangement and movement operation of the de-icing device 3 at the power line.

[0034] The upper wheel group 36 includes two upper wheels 361 arranged front and back, and a driving motor similar to a hub motor structure is arranged inside the upper wheel 361, which is used to drive the upper wheel 361 to rotate, thereby realizing walking operation at the transmission line. The lower wheel group 35 includes a lower wheel 351, which is arranged below the two upper wheels 361. The lower wheel 351 is a single-sided wheel structure, and a slide groove 352 is arranged at the left side plate 32. The lower wheel 351 is installed with the left side plate 32 through a rotating shaft and a slider 353. A servo electric cylinder 354 is arranged between the bottom plate 31 and the slider 353. The servo electric cylinder 354 is used to adjust the height of the lower wheel 351 at the left side plate 32. The upper wheel 361 and the lower wheel 351 are lightweight wheel structures, and are both ox-horn wheel structures, with a concave cross-section and an anti-skid pattern structure on the wheel surface, which is used to improve the stability of the walking structure on power lines and frozen power lines.

[0035] In some embodiments, a mounting plate 37 is arranged between the two upper wheels 361, and the de-icing mechanism 4 is arranged on the mounting plate 37. The de-icing mechanism 4 includes a knocking hammer 41 and a connecting rod 42. The rear end of the connecting rod 42 is in a rotational connection with the mounting plate 37. A lifting component is arranged on the mounting plate 37. The lifting component is used to lift the connecting rod 42 and the knocking hammer 41 and realize their rapid downward release. The bottom of the knocking hammer 41 is a serrated blade-like structure.

[0036] In some embodiments, the lifting component includes an eccentric wheel, which is connected to a one-way transmission component and an eccentric wheel motor. When the eccentric wheel drives the eccentric wheel through the one-way transmission component and acts on the inner side of the connecting rod 42, the lifting operation of the connecting rod 42 and the knocking hammer 41 is realized. When the eccentric wheel rotates past its high point, the knocking hammer 41 quickly descends under the action of gravity, and drives the eccentric wheel to rotate downward at a speed much greater than that of the eccentric wheel motor, thereby realizing the knocking operation on the ice at its front end. Thereafter, the eccentric wheel motor drives the eccentric wheel to rotate again, realizing repeated lifting operations of the knocking hammer 41. Therefore, such operation can realize continuous ice processing, and under the action of the upper wheel 361 and its drive motor, the de-icing operation of the entire transmission line is realized.

[0037] refer to Figure 7 Figure 8 , a control method, applied to the above-mentioned tethered intelligent drone robot for deicing power cables, comprising: Initially, a plurality of de-icing devices 3 are arranged in a straight line side by side at the U-shaped groove 13 of the drone 1, and the de-icing devices 3 and the drone 1 are stably installed by a clamping mechanism. The second cable 22 connects the de-icing devices 3 in series, and the de-icing devices 3 are naturally hung and passed through the U-shaped groove 13, and the rear end thereof is arranged at the bottom of the rear end of the U-shaped groove 13 of the drone. The servo electric cylinder 364 adjusts the lower wheel 351 and places it in the lower end position; In the flight operation, the UAV 1 carrying the deicing device 3 flies to the bottom of the power transmission line that needs to be deiced. During this process, the retracting device 21 adjusts the length of the cable 20 and ensures that the cable 20 is connected in an arc structure; De-icing device arrangement operation, UAV 1 aligns the right side opening of de-icing device 1 with the power transmission line horizontally, and translates it toward the power transmission line until the power transmission line is arranged between the upper wheel 361 and the lower wheel 351, after which the lower wheel 351 of the de-icing device 3 at the front end performs an upward operation under the control of the corresponding servo cylinder 354, and when the power transmission line is clamped by the upper wheel 361 and the lower wheel 351 of the de-icing device, the hook plate 15 rotates outward under the action of the hook plate motor 16 to separate the hook block 17 from the positioning groove 34, and then the upper wheel 361 can rotate forward to separate the de-icing device 3 from the UAV 1, or the UAV 1 can fly backward to separate the de-icing device 3 from the UAV 1, and the second cable 22 connecting the de-icing device 3 is led out from the front end of the U-shaped groove 13, and the de-icing device 3 at the rear end continues to remain on the UAV 1; Repeat the above operation until all de-icing devices 3 are deployed at the corresponding transmission lines; The driving motor drives the upper wheel 361 to rotate forward, and the lifting component of the de-icing mechanism 4 works continuously, so that the hammer 41 strikes the top of the transmission line, forcing the ice on the surface of the transmission line to break and separate, and the drone 1 moves synchronously along the side of the transmission line until the ice on the transmission line of the line section is cleared; The de-icing device arrangement operation is performed in reverse, so that all the de-icing devices 3 are collected on the back of the drone 1 in sequence; Perform de-icing operations on the next route segment or return the drone to its initial state.

[0038] In actual implementation, based on the spacing between adjacent distances between transmission lines, the length of a single section of the second cable 22 is set to be greater than the spacing distance of the transmission lines, and an appropriate arc-shaped arrangement structure is implemented to reduce the interference of the second cable 22 on the operation of the drone 1 and the de-icing device 3.

[0039] In summary, the tethered intelligent drone robot for deicing power cables in this solution adopts a tethered structure, that is, the drone is connected to the chassis by a cable, and the cable can provide power support for the drone to meet the long-term working requirements of the drone, and the drone does not need to carry bulky batteries by itself, so that the drone can have a greater carrying capacity. At the same time, in order to cope with operations that require a large amount of power support such as mechanical deicing or hot melt deicing, continuous power support can be achieved through the cable, thereby improving the efficiency and durability of the drone deicing operation, and being able to achieve deicing operations of multiple line sections at one time; This solution uses multiple deicing devices to work synchronously to implement deicing operations. The drone carries multiple deicing devices and releases them in sequence to perform synchronous deicing operations on multiple transmission lines in the line section, thereby improving the deicing efficiency, which is more than three times the efficiency of traditional single-machine operation. The UAV of this solution adopts a U-shaped groove structure, and the second cable of the de-icing device can be retracted and released through the opening of the U-shaped groove. Therefore, even at high altitudes, the second cable can be used smoothly, which can prevent the cable from colliding with the UAV blades and propellers, greatly improving the flight stability of the UAV; This solution is a control solution for a tethered intelligent drone robot for de-icing power cables. Through positioning and visual operation structures, the de-icing device can accurately and efficiently connect and separate transmission lines at high altitudes, thereby achieving continuous and efficient de-icing operations of multiple de-icing devices. It has the characteristics of simple, accurate, reliable operation, and high de-icing efficiency.

Claims

1. A tethered intelligent drone robot for deicing power cables, characterized by: The invention comprises a drone, a chassis and a cable connecting the chassis and the drone, wherein the chassis provides power to the drone through the cable, wherein the chassis comprises at least one of a storage battery, a power generation device or a power connection device, and wherein a cable retracting device is arranged in the chassis, and wherein the retracting device is used to adjust the length of the cable between the drone and the chassis; The UAV includes a body and propellers. The propellers are at least four groups and are distributed at the outer end of the body to provide lift for the entire UAV. The body has a horizontal U-shaped groove structure. The opening of the U-shaped groove is arranged in the front end direction thereof. At least one deicing device is arranged on the UAV. A docking component is provided between the bottom of the deicing device and the U-shaped groove. The bottom of the deicing device and the bottom of the body are connected with a second cable, and the second cable is arranged through the lower end of the U-shaped structure.

2. The tethered intelligent drone robot for deicing power cables according to claim 1, characterized in that: A bottom plate is arranged at the bottom of the deicing device, and grooves are provided on both sides of the U-shaped groove, and the width of the grooves can accommodate the bottom plate.

3. The tethered intelligent drone robot for deicing power cables according to claim 2 is characterized in that: Side plates are provided on both sides of the bottom plate of the de-icing device, and positioning grooves are provided on the side plates. A clamping mechanism is correspondingly provided on both sides of the U-shaped groove. The clamping mechanism includes a hook plate rotatably connected to the main body, a hook plate motor is provided on one side of the hook plate, and a hook block is provided on the top of the hook plate, and the hook block can be cooperated and restricted at the positioning groove.

4. The tethered intelligent drone robot for deicing power cables according to claim 3 is characterized in that: The bottom of the hook block is a bevel matching structure at the positioning groove.

5. The tethered intelligent drone robot for deicing power cables according to claim 1, characterized in that: The deicing device comprises an upper wheel group and a lower wheel group, and the upper wheel group and the lower wheel group are used to clamp the power transmission line.

6. The tethered intelligent drone robot for deicing power cables according to claim 1, characterized in that: The upper wheel group includes two upper wheels arranged front and back, a driving motor is arranged inside the upper wheel, and the lower wheel is arranged below the two upper wheels. The lower wheel is a single-sided wheel structure, which is installed through the straight groove of the rotating shaft, the slider and the side plate. A servo electric cylinder is arranged between the bottom plate and the slider. The servo electric cylinder is used to adjust the height of the lower wheel at the side plate. The upper wheel and the lower wheel are both bull horn wheel structures, and their wheel surfaces have an anti-slip pattern structure.

7. The tethered intelligent drone robot for deicing power cables according to claim 1, characterized in that: A mounting plate is arranged between the two upper wheels, and a deicing mechanism is arranged on the mounting plate.

8. The tethered intelligent drone robot for deicing power cables according to claim 1, characterized in that: The de-icing mechanism includes a striking hammer and a connecting rod. The rear end of the connecting rod is rotatably connected to the mounting plate. A lifting component is arranged on the mounting plate. The lifting component is used to lift the connecting rod and the striking hammer so that they can be quickly released downward. The bottom of the striking hammer is a serrated blade-like structure.

9. A control method, applied to the above-mentioned tethered intelligent drone robot for deicing power cables, characterized in that: include: Initially, multiple de-icing devices are arranged in a straight line side by side at the U-shaped groove of the drone, and the de-icing devices and the drone are stably installed through the clamping mechanism. The second cable connects the de-icing devices in series, and they are naturally hung down and passed through the U-shaped groove. The rear end of the de-icing devices is arranged at the bottom of the rear end of the U-shaped groove of the drone. The servo electric cylinder adjusts the lower wheel and puts it in the lower end position. Flight operation: The drone carrying the deicing device flies under the power line that needs to be deiced. During this process, the retractable device adjusts the length of the cable and ensures that the cable is connected in an arc structure. De-icing device placement operation: The UAV aligns the open side of the de-icing device with the power line horizontally and moves horizontally toward the power line until the power line of the de-icing device is placed between the upper wheel and the lower wheel. After that, the de-icing lower wheel at the front end performs an upward operation under the control of the corresponding servo cylinder. When the power line is clamped by the upper wheel and the lower wheel of the de-icing device, the UAV performs a backward flight, the de-icing device is detached from the UAV, and the second cable connected to the de-icing device is led out from the front end of the U-shaped groove, and the de-icing device at the rear end continues to remain on the UAV. Repeat the above operation until all de-icing devices are deployed at the corresponding transmission lines; The driving motor drives the upper wheel to rotate forward, and the lifting component of the de-icing mechanism works continuously, so that the hammer strikes the top of the transmission line, forcing the ice on the surface of the transmission line to break and separate. The UAV moves forward synchronously on the side of the transmission line until the ice on the transmission line of this line section is cleared; Perform the de-icing device arrangement operation in reverse, so that all the de-icing devices are collected on the back of the drone in sequence; Perform de-icing operations on the next route segment or return the drone to its initial state.

10. According to the control method described in claim 9, the length of the second cable between the two de-icing devices is greater than the spacing distance between two adjacent power transmission lines.

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