Overhead ground wire magnetic induction energy taking device based on capacitance compensation

Abstract

The invention discloses an overhead ground wire magnetic induction energy taking device based on capacitance compensation, which is used for taking electricity of overhead line on-line monitoring equipment, an overhead line comprises a common ground wire and an OPGW ground wire, and the wiring mode of the overhead line is that the common ground wire is subjected to sectional insulation and single-point grounding, and the OPGW ground wire is grounded tower by tower; the energy taking device takes electricity from a parallel gap of a ground wire insulator and comprises a decoupling inductor, a piezoresistor and a rectifying and voltage stabilizing module, and the decoupling inductor and the piezoresistor are connected in series to form an overvoltage protection module and are connected in parallel with the parallel gap; the circuit also comprises a compensation capacitor, the compensation capacitor is connected in series with the rectification voltage stabilization module and then is connected in parallel with the piezoresistor, and the compensation capacitor is used for improving the theoretical maximum power of energy taking. The compensation capacitor is introduced into the ground wire energy-taking device to reduce or even eliminate the influence of inductance on energy-taking power, so that the energy-taking power is improved.

Description

Technical Field

[0001] The present invention relates to a method for obtaining energy from an overhead ground wire by magnetic induction, so as to meet the power demand of an online monitoring device for an overhead line installed on a pole tower and facilitate the construction of a digital transmission line. Background Art

[0002] Online monitoring technology is an important means to ensure the safe and stable operation of overhead lines. However, the existing online power supply technology for overhead lines cannot meet the actual power demand of monitoring equipment, which limits the development of online monitoring technology. For example, the output power capacity of solar panels is insufficient under long-term rainy days or snow-covered conditions; the current transformer installed on the conductor cannot power the equipment installed on the tower because it is on the high-voltage side; the wireless power transmission efficiency is low and the equipment cost is high; new power generation technologies such as friction power generation and temperature difference power generation have low power levels and immature technical systems.

[0003] Domestic overhead lines with voltage levels of 110kV and above are generally equipped with two ground wires for lightning protection purposes. The power frequency current in the AC overhead line conductor generates a power frequency magnetic field in space, which acts on the ground wire loop to generate induced voltage or current. The magnetic induction energy on the ground wire is very abundant, which is an ideal power source for online monitoring equipment.

[0004] At present, the energy-collecting load is usually connected in parallel to the two ends of the insulator of the segmented insulated ground wire to realize the magnetic induction energy collection of the ground wire. However, the self-inductance of the ground wire in the energy collection loop and the mutual inductance between the two ground wires increase the reactive component in the energy collection loop, limiting the full utilization of the magnetic induction energy of the ground wire. In addition, for the purpose of overvoltage protection, the decoupling inductor is usually connected in series with the power load inside the energy collection device to limit the rate of change of transient current. This part of the inductance will also lose energy-collecting power under normal working conditions. Summary of the invention

[0005] The purpose of the present invention is to provide an overhead ground wire magnetic induction energy harvesting device based on capacitor compensation, which reduces or even eliminates the influence of inductance on energy harvesting power by introducing a compensation capacitor into the ground wire energy harvesting device, thereby improving the energy harvesting power.

[0006] To this end, the present invention provides an overhead ground wire magnetic induction energy collection device based on capacitor compensation, which is used for collecting power from online monitoring equipment of overhead lines. The overhead lines include ordinary ground wires and OPGW ground wires, and their wiring method is: the ordinary ground wires are segmented and single-point grounded, and the OPGW ground wires are grounded tower by tower; the energy collection device draws power from the parallel gap of the ground wire insulator, including a decoupling inductor, a varistor, and a rectifier and voltage-stabilizing module, wherein the decoupling inductor and the varistor are connected in series to form an overvoltage protection module and are connected in parallel with the parallel gap; and also includes a compensation capacitor, which is connected in series with the rectifier and voltage-stabilizing module and then connected in parallel with the varistor, the rectifier and voltage-stabilizing module is used to output a DC voltage with a stable amplitude, and the compensation capacitor is used to increase the theoretical maximum power of energy collection.

[0007] The present invention realizes online power extraction of overhead ground wires based on the magnetic induction voltage generated on the ground wire by the mutual inductance coupling of the ground wires. By introducing a compensation capacitor in the energy extraction device, the influence of the ground wire loop inductance on the energy extraction power is reduced, thereby improving the energy extraction power. This device can meet the power demand of the overhead line online monitoring equipment installed on the pole tower, and assist in the construction of digital transmission lines.

[0008] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0010] Figure 1 It is a schematic diagram of the overhead line ground wire wiring structure;

[0011] Figure 2 A circuit diagram of an overhead ground wire magnetic induction energy harvesting device based on capacitor compensation of the present invention is shown;

[0012] Figure 3 The ground wire energy extraction equivalent circuit of the present invention is shown;

[0013] Figure 4 The structure of a 500kV single-circuit line is shown;

[0014] Figure 5 The structure of a 500kV double-circuit line is shown;

[0015] Figure 6 The structure of a 220kV single-circuit line is shown;

[0016] Figure 7 The structure of the 220kV double-circuit line is shown;

[0017] Figure 8 The structure of a 110kV single-circuit line is shown;

[0018] Fig. 9 The structure of a 110 kV double-circuit line is shown. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0020] The present invention realizes online power drawing of overhead ground wires based on the magnetic induction voltage generated on the ground wire by the mutual inductance coupling of the ground wires. The influence of the ground wire loop inductance on the energy drawing power is reduced by introducing a compensation capacitor in the energy drawing device. A method for selecting the optimal compensation capacitor value is proposed based on the ground wire energy drawing equivalent circuit, thereby improving the theoretical maximum power of the overhead ground wire magnetic induction energy drawing.

[0021] The ground wire connection method of the overhead line used in the present invention is as follows Figure 1 As shown. There are two ground wires for overhead lines, one is the common ground wire and the other is the OPGW ground wire (i.e., composite optical cable ground wire). The OPGW ground wire is grounded tower by tower. The common ground wire is segmented and grounded at a single point. The ground wire insulator at the tension tower is horizontal, and several straight towers are arranged between two adjacent tension towers. Only one straight tower has a common ground wire that is grounded at a single point. The ground wires at other straight towers are connected to the tower pole after passing through the insulator.

[0022] According to the idea of ​​capacitor compensation, the ground wire magnetic induction energy extraction circuit proposed in the present invention is designed as follows: Figure 2 shown.

[0023] The energy taking device takes power from the parallel gap of the ground wire insulator, and includes a decoupling inductor, a varistor, a compensation capacitor, and a rectifier and voltage stabilization module.

[0024] The parallel gap is a built-in accessory of the ground wire insulator, which plays the role of discharging lightning current. The decoupling inductor and the varistor together constitute the overvoltage protection module of the energy extraction device, which is connected in parallel with the parallel gap to prevent damage to the device in the event of lightning strikes. The compensation capacitor is connected in series with the rectifier and voltage regulator module and then in parallel with the varistor. The compensation capacitor is used to increase the theoretical maximum power of energy extraction. The rectifier and voltage regulator module converts the AC voltage into a DC voltage with a stable amplitude for use by the power load.

[0025] The optimal compensation capacitor value can be calculated based on the ground wire energy equivalent circuit ( Figure 3 ) is obtained by the port Thevenin equivalent method. Assume that the energy extraction circuit is the circuit formed by the ground wire between the i-th tower and the m-th tower, and the energy extraction load is installed on the tower numbered m. The subscript of the OPGW ground wire is 1, and the subscript of the segmented insulated ground wire is 2. l1: the circuit formed by the OPGW and the earth, l2: the circuit formed by the two ground wires.

[0026] Figure 2 The subscripts i and m in the column represent the tower number. The i-th column (between the i-1th tower and the i-th tower) and Z i-1(1) , They respectively represent the self-impedance and vortex induced potential of the OPGW. Corresponding to the eddy induced potential between the two ground wires at node i and node m. i-m(1e) , Z i-m(2e) Respectively represent the self-impedance of the two ground wires between node i and node m. i It represents the tower grounding resistance, and Z1 represents the energy-drawing load.

[0027] For the part on the left side of node i, let the equivalent voltage looking left from node i be The equivalent impedance is Z i(e) . It is assumed that the value of the induced potential of each OPGW ground wire is The self-impedance value is Z0, and the grounding resistance value of the tower is R0. Then it can be deduced that:

[0028]

[0029] According to formula (1), an iterative calculation can be formed, and the solution is carried out from point i to the left. When the number of towers on the left side of node i is large enough, in order to simplify the calculation, it can be approximately considered that Z i(e) ≈Z i-1(e) So we have:

[0030]

[0031] For the part to the right of node m, let the equivalent voltage looking right from node m be The equivalent impedance is Z m(e) . It is assumed that the value of the induced potential of each OPGW ground wire is The self-impedance value is Z0 ′ , the grounding resistance value of the tower is R0 ′ . Then we can deduce:

[0032]

[0033] According to the above formula, an iterative calculation can be formed, and the solution is carried out from point m to the right. When the number of towers on the right side of node m is large enough, in order to simplify the calculation, it can be approximately considered that: So we have:

[0034]

[0035] For the part between node i and node m, when performing equivalent circuit analysis, since the tower grounding resistance is much larger than the ground line impedance, the current flowing into the tower in the longitudinal direction can be ignored and the grounding channel can be regarded as an open circuit. So:

[0036]

[0037] In the formula is the average value of the induced potential of each level on the segmented insulated ground wire, Z 0(2) is the average value of the self-impedance of each level of the segmented insulated ground wire. From this, the ground wire current when no load is connected can be calculated

[0038]

[0039] On this basis, the Thevenin equivalent voltage from the energy-drawing load to the line can be obtained: With impedance Z e1 :

[0040]

[0041] The Thevenin equivalent impedance Z of the ground port calculated in formula (7) e1 is a complex number. The real part of the complex number represents the resistance of the ground loop, which cannot be compensated. The imaginary part of the complex number represents the inductive reactance of the ground loop, which can be compensated by capacitors. Let the imaginary part of the equivalent impedance be X in value, and let the decoupling inductance used for overvoltage protection be L, then the value of the compensation capacitor C can be determined according to formula (8):

[0042]

[0043] Where ω=2πf, f is the frequency of the conductor current, which is 50Hz in China.

[0044] against Figures 4 to 9 The improvement effect of the capacitance compensation method of the present invention on the theoretical maximum ground line magnetic induction energy extraction power is calculated for the line structures of different voltage levels, as shown in Table 1. The results show that the present invention can effectively improve the ground line magnetic induction energy extraction power and better power the online monitoring equipment of the overhead line.

[0045] Table 1. Energy efficiency improvement effect

[0046] Voltage level and line structure Energy extraction power improvement 110kV single circuit 20％ 110kV double circuit 22％ 220kV single circuit 19％ 220kV double circuit 24％ 500kV single circuit 23％ 500kV double circuit 22％

[0047] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An overhead ground wire magnetic induction energy harvesting device based on capacitance compensation, used for harvesting power from online monitoring equipment of overhead lines, characterized in that: The overhead line includes a common ground wire and an OPGW ground wire, and the connection method is: the common ground wire is segmented insulated and single-point grounded, and the OPGW ground wire is grounded tower by tower; The energy taking device takes power from the parallel gap of the ground wire insulator, and includes a decoupling inductor, a varistor, and a rectifier and voltage stabilizing module, wherein the decoupling inductor and the varistor are connected in series to form an overvoltage protection module and are connected in parallel with the parallel gap; It also includes a compensation capacitor, which is connected in series with the rectification and voltage stabilization module and then in parallel with the varistor. The rectification and voltage stabilization module is used to output a DC voltage with a stable amplitude, and the compensation capacitor is used to increase the theoretical maximum power of energy extraction.

2. The overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to claim 1 is characterized in that: The calculation formula for the optimal capacitance value of the compensation capacitor is: Wherein, L is the decoupling inductance value, ω=2πf, f is the conductor current frequency, and X is the imaginary value of the Thevenin equivalent impedance of the ground port, wherein the Thevenin equivalent impedance of the ground port is a complex number.

3. The overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to claim 1 is characterized in that: The calculation formula of the Thevenin equivalent impedance of the ground port is: In which, the energy-taking circuit of the ground wire is assumed to be the circuit formed by the ground wire between the ith tower and the mth tower, and the energy-taking load is installed on the tower numbered m, Z i-m(1e) , Z i-m(2e) Respectively represent the self-impedance of the two ground wires between node i and node m, Z i(e) is the equivalent impedance looking left from node i, Z m(e) is the equivalent impedance looking to the right from node m.

4. The overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to claim 1, characterized in that: The equivalent impedance Z looking left from node i i(e) The calculation formula is as follows: Among them, Z0 is the average self-impedance of each OPGW ground wire, and R0 is the average grounding resistance of the tower.

5. According to the overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to claim 1, the equivalent impedance z viewed from the node m to the right is m(e) The calculation formula is as follows: in, Z0 ′ is the average self-impedance of each OPGW ground line, R0 ′ is the average grounding resistance of the tower.

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