Induction energy taking device and method based on leakage magnetic field of three-core wrapping cable

Abstract

The invention discloses an induction energy taking device and method based on a leakage magnetic field of a three-core wrapping cable, and belongs to the technical field of energy acquisition, the induction energy taking device comprises an electricity taking iron core, three single-phase induction coils and three zero-sequence current electricity taking induction coils, when the induction energy taking device is used, the electricity taking iron core is arranged outside the three-core cable in a sleeving mode; the electricity taking iron core comprises three iron core pieces, and the three iron core pieces are spliced in the circumferential direction. Bosses are arranged on the inner wall of the iron core piece, the three single-phase induction coils are wound on the three bosses respectively, and a first containing groove is formed between every two adjacent bosses. And the three zero-sequence current electricity-taking induction coils are wound on the iron core piece. According to the invention, energy can be efficiently and stably collected from a leakage magnetic field around the three-core cable and is used for supplying power to cable monitoring equipment, and the problems of high environmental dependence, high operation cost, low energy taking efficiency and inconvenient installation in the prior art are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy acquisition, and in particular relates to an inductive energy acquisition device and method based on the leakage magnetic field of a three-core turnkey cable. Background Art

[0002] With the acceleration of urbanization and the continuous growth of electricity demand, the scale of urban power grids has developed rapidly. As an indispensable way of power transmission in modern cities, real-time monitoring and management of the operating status of power cables has become particularly important. However, since power cables are usually laid in underground pipelines or closed tunnels, their working environment is complex and harsh. Once a failure occurs, it may cause power supply interruption and damage to surrounding environmental facilities. Therefore, building a cable operation status monitoring system has become the focus of academia and industry.

[0003] The existing energy supply problem of online monitoring equipment mainly relies on solar energy, laser energy supply and traditional current transformer energy supply, but these technologies have the disadvantages of high environmental dependence, high operating costs and low energy efficiency. How to achieve efficient and stable energy collection from three-core cables has become a technical problem that technicians need to overcome.

[0004] It is an inevitable trend for urban distribution network transformation to replace traditional overhead lines with cable lines. Power cables are laid underground in a relatively harsh operating environment. Cable failures occur from time to time, which can easily cause sudden power outages and fire hazards. Cable lines are also subject to theft and other human damage accidents, which will cause significant economic losses to enterprises. The traditional underground power cable inspection method has defects such as high labor intensity, low efficiency, and high labor costs. In addition, most of the current three-core power cables contain a shielding layer with an outer grounding. The superposition distribution of the three-phase magnetic field seriously weakens the magnetic field around the cable. If the traditional CT power extraction method is used, the energy extraction efficiency will be restricted. Therefore, a technical solution for self-energy extraction suitable for three-core cables is needed. Summary of the invention

[0005] The present invention provides an inductive energy harvesting device and method based on the leakage magnetic field of a three-core turnkey cable, which can efficiently and stably collect energy from the leakage magnetic field around the three-core cable for supplying power to cable monitoring equipment, thereby solving the problems of high environmental dependence, high operating cost, low energy harvesting efficiency and inconvenient installation in the prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: An inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable comprises a power-taking iron core, three single-phase induction coils and three zero-sequence current power-taking induction coils. When in use, the power-taking iron core is sleeved outside the three-core cable; the power-taking iron core comprises three iron core pieces, and the three iron core pieces are spliced ​​along the circumferential direction; the inner wall of the iron core piece has bosses, and the three single-phase induction coils are respectively wound on the three bosses, and a first accommodating groove is formed between two adjacent bosses; and the three zero-sequence current power-taking induction coils are wound on the iron core piece.

[0007] Furthermore, the core piece adopts a mortise and tenon structure.

[0008] Furthermore, the three core pieces are evenly distributed in the circumferential direction at an angle of 120°.

[0009] Furthermore, the three core pieces are completely identical.

[0010] Furthermore, the single-phase induction coil is in the form of a flexible PCB board.

[0011] Furthermore, the three single-phase induction coils have the same number of turns.

[0012] Furthermore, the first accommodating grooves are arranged at intervals of 120° on the inner wall of the power-taking core, and the space volumes occupied by adjacent single-phase induction coils in the first accommodating grooves are equal.

[0013] Furthermore, a groove group is provided between adjacent first grooves, and the groove group includes two second grooves arranged opposite to each other, and each groove group includes a second groove located on the inner wall of the boss; the groove group is used to accommodate the zero-sequence current power extraction induction coil.

[0014] Furthermore, the material of the core piece is silicon steel.

[0015] An inductive energy harvesting method based on the leakage magnetic field of a three-core turnkey cable, comprising: S1. Install the induction energy harvesting device based on the leakage magnetic field of the three-core turnkey cable as described in claim 1 outside the three-core turnkey cable; S2. Make the center line of each single-phase induction coil coincide with the center symmetry line of two adjacent conductors in the three-core turnkey cable. During the operation of the three-core turnkey cable, a radial rotating leakage magnetic field is superimposed around it. Each single-phase induction coil captures the spatial magnetic field energy around the three-core turnkey cable, generates an induced potential, and extracts energy. At the same time, the three-phase zero-sequence current induction coil obtains electrical energy through the principle of electromagnetic induction.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: In the actual operation of the three-core cable, each phase of the cable does not overlap, so a radial rotating leakage magnetic field will be superimposed around it. The energy harvesting device based on the leakage magnetic field of the three-core cable uses this rotating magnetic field to collect magnetic field energy, realizing the self-energy harvesting of the underground three-core cable monitoring device. With the appropriate combination of auxiliary batteries, the monitoring device can be powered in real time and achieve a stable supply of energy. This self-energy harvesting method liberates manpower and eliminates the environmental hazards that may exist when inspecting underground pipelines; the application method saves resources and is clean and environmentally friendly; the maintenance method is relatively simple, and there is no safety problem due to electrical isolation from the power grid. Such an energy collector based on the leakage electric field of the three-core cable can provide energy for monitoring equipment, which is conducive to the increase in the scale of smart grids and promotes the development of smart grids.

[0017] The three-core turnkey cable leakage magnetic field induction energy harvesting system provided by the present invention can fully utilize the spatial magnetic field energy around the three-core cable through the unique energy harvesting iron core and three-phase induction coil structure design, improve the induced potential of the induction coil, and achieve high energy harvesting efficiency. The power harvesting iron core includes three iron core pieces spliced ​​with mortise and tenon structures, and each part is evenly distributed in a circumferential direction of 120°. The three-phase unidirectional induction coils are respectively installed on the three iron core pieces, and the three coils on the three iron core pieces are independent of each other, which is convenient for unified processing and on-site installation. At the same time, each coil of this structure can independently obtain energy from the leakage magnetic field of the cable while maintaining three-phase symmetry to ensure the stability of the energy harvesting system.

[0018] Furthermore, the energy extraction device also includes a zero-sequence current power extraction coil, which can play a role in supplementing energy extraction when the zero-sequence current is large, thereby further improving the power extraction efficiency.

[0019] Furthermore, the three core pieces are completely identical, which can simplify the manufacturing process, make the assembly process simpler and faster, and reduce the possibility of assembly errors.

[0020] Furthermore, the single-phase induction coil is in the form of a flexible PCB board, which has excellent elasticity and bending ability. In the bent state, it can still maintain stable electrical performance to ensure the normal operation of the single-phase induction coil; at the same time, the flexible PCB board eliminates the need to route wires to solder points and connectors, reduces the number of components required, and further reduces assembly costs.

[0021] Furthermore, the number of turns of the three single-phase induction coils is equal, the design and manufacturing process can be more unified and simplified, and the production cost is reduced; the induced voltages generated by the three single-phase induction coils are also equal, which is conducive to maintaining the balance of the three-phase voltage.

[0022] The energy acquisition device of the present invention has a simple structure, is easy to install, does not require additional energy supply, reduces operating costs, and improves system reliability and practicality.

[0023] The energy extraction device of the present invention can be widely used in monitoring systems of various three-core cables, providing a stable energy supply for online monitoring of the cables, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the installation of an embodiment of a three-core turnkey cable energy extraction device of the present application; Figure 2 This is a schematic diagram of the planar structure of the electric core; Figure 3 It is a three-dimensional schematic diagram of the electric core structure; Figure 4 It is a structural schematic diagram of a single-phase PCB flexible coil; Figure 5 It is a schematic diagram of the installation method of the three-phase induction coil in the power-taking iron core; Figure 6 This is the magnetic field line distribution diagram of the Maxwell2D model; Figure 7 It is the waveform diagram of the induced voltage in one cycle of the single-phase induction coil; Figure 8 The internal resistance and self-inductance of the single-phase induction coil obtained by finite element simulation; Fig. 9 This is the simulated waveform of the induced voltage of the three-phase induction coil under the traditional CT power supply mode; Fig.10 This is a simulation waveform diagram of the induced voltage of the three-phase induction coil when using this embodiment; Fig.11 is a schematic diagram of three end covers surrounding the split core; Fig.12 Take the power schematic for CT; Fig.13 This is a curve showing the relationship between the primary current and the maximum power that the amorphous material core can achieve.

[0025] In the attached drawings: 1. power supply core; 2. three-core turnkey cable; 3. first receiving groove; 4. single-phase induction coil; 5. second receiving groove; 6. zero-sequence current power supply induction coil; 7. end cover; 11. core member; 12. boss. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be another element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be another element centered thereon at the same time. The terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc. used herein indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0030] The present invention provides an inductive energy acquisition device and method based on the leakage magnetic field of a three-core turnkey cable, which can acquire energy from the leakage magnetic field around the cable through the principle of electromagnetic induction and be used to supply power to cable monitoring equipment.

[0031] Example 1 A three-core turnkey cable leakage magnetic field induction energy harvesting device includes a power harvesting iron core 1, a three-phase induction coil and a three-phase zero-sequence current power harvesting induction coil. The three-phase induction coil includes three single-phase induction coils 4, and the three-phase zero-sequence current power harvesting induction coil includes three zero-sequence current power harvesting induction coils 6.

[0032] Finite element simulation software was used to obtain the best power-taking effect when the energy-taking winding in the accommodating slot was distributed at 180° in the iron core, and the best when it was distributed at 120°. However, both methods brought great difficulties to on-site installation. Therefore, the power-taking iron core was designed as three 120° completely consistent mortise and tenon structures, which were evenly distributed along the circumference to facilitate unified processing and on-site installation. Each single-phase induction coil 4 in the three-phase induction coils A, B, and C was placed in the three first accommodating slots 3 respectively; compared with the existing current transformer energy-taking (CT) method, a completely different energy-taking principle was adopted, which can fully capture the spatial magnetic field energy around the three-core cable, enhance the induced potential of the induction coil, ensure stable energy output, and have high energy-taking efficiency and be independent of the environment.

[0033] like Figure 1 As shown, the two-phase current is drawn from the power frequency current booster and connected to the experimental cable (three-core turnkey cable 2) using a three-phase three-wire connection method. The currents of phases A and B of the cable are adjusted to be equal, with a phase difference of 120°. At this time, no zero-sequence current is generated inside the experimental cable. By adjusting different input currents, the induced voltage across the load resistor on the power coil is measured with a multimeter, and the total load power is calculated as shown in Table 1.

[0034]

[0035] Therefore, the energy harvesting device based on the leakage magnetic field of the three-core cable can obtain energy from the cable through the principle of electromagnetic induction.

[0036] Table 2 shows the simulation results of the relationship between the coil induced voltage and the air gap thickness. Using finite element simulation software, under the same conditions, the coil induced voltage is 4.68V when the power-taking core does not have an air gap. It can be seen that when the air gap thickness is small enough (0.1 mm -0.5 mm), it has little effect on the energy efficiency of the energy-taking device.

[0037] Table 2

[0038] Reference Fig.12 For the current transformer (CT) energy harvesting technology currently in common use, since overhead lines generally adopt a single-core cable design and the surrounding magnetic field distribution is relatively uniform, the current transformer energy harvesting technology has been widely used in this field and can effectively obtain energy through the principle of electromagnetic induction.

[0039] The basic formula for CT power supply is as follows: The maximum unsaturated primary current of the core is ,like , the core is not saturated when it obtains the maximum power, which is ( ).

[0040] In the formula, is the maximum unsaturated magnetic flux density of the core, is the equivalent magnetic circuit length, is the equivalent magnetic permeability of the iron core, A is the cross-sectional area of ​​the core, is the secondary side magnetizing reactance, is the copper resistance of the secondary coil, is the current of the primary transmission line, is the angular frequency.

[0041] If the core material is selected as amorphous material, the length is 30cm, according to the equivalent magnetic permeability of amorphous material: =0.0217H / m, saturation magnetic flux density (T) = 0.85T 16.62A. When the CT power supply method is used, the relationship curve between the primary current within a certain range and the maximum power that the amorphous material core can obtain is given as follows: Fig.13 shown.

[0042] like Figure 2 , Figure 3 and Figure 5 As shown, the power core 1 is in the shape of a hollow cylinder. When in use, it is sleeved on the outer wall of the three-core turnkey cable 2. Three first accommodating grooves 3 are provided on the inner wall of the power core 1. The first accommodating grooves 3 extend axially, and the three first accommodating grooves 3 are evenly distributed along the circumference of the power core 1. Each single-phase induction coil in the three-phase induction coil is placed in the three first accommodating grooves 3 respectively. The power core 1 includes three core pieces 11. The three core pieces 11 adopt a mortise and tenon structure. Each part is evenly distributed circumferentially at 120° and spliced ​​into an integral structure of the power core, which is convenient for unified processing and on-site installation. The air gap between the three core pieces 11 is 0.1 mm -0.5 mm.

[0043] The core member 11 has a boss 12 in the middle, and a first receiving groove 3 is formed between the bosses 12 of two adjacent core members 11. Two second receiving grooves 5 are provided on the outer wall and the inner wall of the core member 11, and the second receiving groove 5 provided on the inner wall of the core member 11 is located in the middle of the boss 12. Each single-phase induction coil 4 is placed in the three first receiving grooves 3, respectively. Figure 4 In the flexible PCB board form shown, the number of turns of the three-phase induction coils is equal, which reduces the production cost; the zero-sequence current power supply coil 6 is wound between the two second accommodating grooves 5 opposite to the iron core, which can play a role in supplementing energy supply when the zero-sequence current is large, thereby further improving the power supply efficiency.

[0044] Furthermore, the three-phase induction coil is divided into three independent single-phase energy extraction coils 4 , and the number of turns of the three single-phase energy extraction coils 4 is equal.

[0045] The size and shape of the power-collecting iron core 1 are designed to maximize the contact area with the three-core cable, so as to fully capture the spatial magnetic field energy around the three-core cable. The inner diameter and outer diameter of the iron core are adapted according to the size of the cable to ensure that the iron core can be tightly mounted on the outer wall of the cable.

[0046] The core 11 is made of stacked silicon steel sheets, which have high magnetic permeability and can effectively gather magnetic fields while reducing hysteresis losses. These properties of silicon steel materials enable the core to respond quickly when the magnetic field changes, thereby improving energy extraction efficiency.

[0047] The coil is divided into three independent energy-taking coils, each of which is placed in the first accommodating groove 3. This design enables each coil to independently obtain energy from the leakage magnetic field of the three-core turnkey cable 2 while maintaining three-phase symmetry to ensure the stability of the energy-taking system.

[0048] After the power core 1 is installed, Fig.11 The three end covers 7 shown are sleeved on the outer surface of the iron core, and the adjacent end covers 7 are fastened with bolts so that the power-taking iron core 1 can surround the outer surface of the three-core package cable, which has good constraints and can make the energy-taking winding and the cable have better symmetry.

[0049] The finite element software is used to establish the model of the power supply core and the three-core cable and perform simulation. The parameters set are as follows: the relative magnetic permeability of the core 8000, inner diameter 110mm, outer diameter 160mm, core length 30cm, coil turns N= 300, peak value of primary current of three-core cable I= 100A. According to the finite element software analysis, the magnetic field lines on the surface of the three-core cable are distributed as follows: Figure 6 As shown, the induced voltage of the single-phase induction coil is Figure 7 The maximum is 1.5V. The internal impedance of the single-phase induction coil is as follows: Figure 8 =(7.18+j14.34)Ω, so when the load resistance is Ω, the maximum power can be obtained in the model .

[0050] This proves that the three-core all-in-one cable leakage magnetic field induction energy harvesting device of the present invention can effectively obtain energy from the leakage magnetic field around the three-core cable, provide a stable energy supply for the cable monitoring equipment, and Fig. 9 and Fig.10 The simulation results show that the efficiency of using leakage magnetic field to obtain power is greater than that of traditional CT power supply method, which has important practical value and broad market application prospects.

[0051] Example 2 This embodiment provides an inductive energy harvesting method based on the leakage magnetic field of a three-core turnkey cable, based on the inductive energy harvesting device provided in Embodiment 1, including the following steps: S1. Install the inductive energy harvesting device described in Example 1 outside the three-core turnkey cable 2; S2. Make the center line of each single-phase induction coil 4 coincide with the center symmetry line of two adjacent conductors in the three-core turnkey cable. During the operation of the three-core cable, a radial rotating leakage magnetic field will be superimposed around it. Each single-phase induction coil 4 captures the spatial magnetic field energy around the three-core turnkey cable, generates an induced potential, and obtains energy; at the same time, the three-phase zero-sequence current power induction coil 6 obtains energy through the principle of electromagnetic induction and generates an induced potential.

[0052] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0053] The term "consisting of" describing a combination shall include the identified elements, ingredients, parts or steps and other elements, ingredients, parts or steps that do not substantially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe a combination of elements, ingredients, parts or steps herein also contemplates embodiments that consist essentially of these elements, ingredients, parts or steps. By using the term "may", it is intended to illustrate that any of the attributes described that "may" be included are optional.

[0054] Multiple elements, ingredients, parts or steps can be provided by a single integrated element, ingredient, part or step. Alternatively, a single integrated element, ingredient, part or step can be divided into separate multiple elements, ingredients, parts or steps. The disclosure "one" or "an" used to describe an element, ingredient, part or step is not intended to exclude other elements, ingredients, parts or steps.

[0055] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the foregoing claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. An inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable, characterized in that: The invention comprises a power-taking iron core (1), three single-phase induction coils (4) and three zero-sequence current power-taking induction coils (6). When in use, the power-taking iron core (1) is sleeved outside a three-core cable (2); the power-taking iron core (1) comprises three iron core pieces (11), and the three iron core pieces (11) are spliced ​​in a circumferential direction; the inner wall of the iron core piece (11) has a boss (12), the three single-phase induction coils (4) are respectively wound on the three bosses (12), and a first accommodating groove (3) is formed between two adjacent bosses (12); and the three zero-sequence current power-taking induction coils (6) are wound on the iron core piece (11).

2. According to claim 1, an inductive energy harvesting device based on leakage magnetic field of a three-core turnkey cable is characterized in that: The iron core piece (11) adopts a mortise and tenon structure.

3. An inductive energy harvesting device based on leakage magnetic field of a three-core turnkey cable according to claim 1 or 2, characterized in that: The three core pieces (11) are evenly distributed in the circumferential direction at an angle of 120°.

4. The inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable according to claim 3 is characterized in that: The three core pieces (11) are completely identical.

5. The inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable according to claim 1 is characterized in that: The single-phase induction coil (4) is in the form of a flexible PCB board.

6. The inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable according to claim 1 or 5, characterized in that: The three single-phase induction coils (4) have the same number of turns.

7. The inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable according to claim 1 is characterized in that: The first accommodating grooves (3) are arranged at intervals of 120° on the inner wall of the power-taking iron core (1), and the space occupied by adjacent single-phase induction coils (4) in the first accommodating grooves (3) has the same volume.

8. The inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable according to claim 1 is characterized in that: An accommodating groove group is provided between adjacent first accommodating grooves (3), the accommodating groove group comprising two second accommodating grooves (5) arranged opposite to each other, one second accommodating groove (5) in each accommodating groove group being located on the inner wall of the boss (12); the accommodating groove group is used for accommodating a zero-sequence current extraction induction coil (6).

9. The inductive energy harvesting device based on the leakage magnetic field of a three-core turnkey cable according to claim 1 is characterized in that: The material of the iron core piece (11) is silicon steel.

10. An inductive energy harvesting method based on the leakage magnetic field of a three-core turnkey cable, characterized in that: include: S1. Install the induction energy harvesting device based on the leakage magnetic field of the three-core package cable as described in claim 1 outside the three-core package cable (2); S2, making the center line of each single-phase induction coil (4) coincide with the center symmetry line of two adjacent conductors in the three-core turnkey cable, so that during operation, the three-core turnkey cable generates a radial rotating leakage magnetic field in the surrounding area, and each single-phase induction coil (4) captures the spatial magnetic field energy around the three-core turnkey cable, generates an induced potential, and extracts energy; At the same time, the three-phase zero-sequence current induction coil (6) obtains electrical energy through the principle of electromagnetic induction.

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