Non-contact measurement method and system for grid voltage based on multi-node electric field coupling

Abstract

This invention discloses a non-contact method and system for measuring power grid voltage based on multi-node electric field coupling, belonging to the field of voltage measurement technology. It achieves non-contact voltage measurement of overhead transmission lines by retrieving the conductor-to-ground voltage from the induced signals of multiple sensing nodes around the conductor. The method includes: acquiring the induced voltage signal of the cable under test detected by each of N pairs of sensing nodes; N≥3; each pair of sensing nodes includes two sensing nodes arranged radially; each pair of sensing nodes corresponds to a differential voltage signal; the differential voltage signal is calculated based on the two induced voltage signals detected by a pair of sensing nodes; a voltage reconstruction algorithm is used to construct a ternary nonlinear equation system for each differential voltage signal; the ground voltage value of the cable under test is calculated based on the N ternary nonlinear equation systems; this invention enables accurate voltage measurement at any location.

Description

Technical Field

[0001] This invention relates to the field of voltage measurement technology, and in particular to a non-contact method and system for measuring grid voltage based on multi-node electric field coupling. Background Technology

[0002] In the field of voltage measurement, while traditional contact-based voltage measurement systems and their underlying measuring devices have wide applications, the installation of these meters requires damaging the insulation layer of the power grid cables. At measurement points where damaging the insulation layer is neither possible nor convenient, non-contact voltage measurement devices are needed. With the research of electrical engineers and experts on non-contact voltage measurement methods, a series of such methods have emerged. Among them, the non-contact voltage measurement method based on the principle of electric field coupling is particularly favored by researchers, leading to the development of many practical non-contact voltage measurement systems based on this method.

[0003] Currently, non-contact voltage measurement methods based on the principle of electrode plate electric field coupling are relatively mature and can meet most voltage measurement needs. However, for some measurement points with high accuracy requirements, traditional non-contact voltage measurement methods still cannot meet the testing requirements. Furthermore, this method mainly considers the rather straightforward theory that "the sensor plate couples with the cable and ground to form capacitances," without conducting an objective analysis at the electric field level. Instead, it directly uses the voltage transfer function of the coupling circuit to theoretically calculate and solve for the voltage to be measured. Such a solution is singular and ignores the influence of parasitic capacitance. In addition, the measurement result is directly related to the size of the capacitance obtained by the electrode plate coupling, and because this coupling capacitance is unknown, there are often a series of problem-solving difficulties, which greatly increases the difficulty of maintaining high accuracy in the measurement results. Therefore, further research on non-contact voltage measurement systems based on this method mainly focuses on how to minimize measurement errors. Moreover, some existing non-contact voltage measurement systems based on this method have the disadvantage that the measurement position must be fixed, i.e., the positions of the sensor and the wires must be fixed during measurement, which limits the practical measurement in different scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide a non-contact method and system for measuring grid voltage based on multi-node electric field coupling, which can accurately measure voltage at any location.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A non-contact measurement method for grid voltage based on multi-node electric field coupling is proposed. This method uses the inductive signals from multiple inductive nodes around the conductor to inversely reflect the conductor-to-ground voltage, thereby achieving non-contact measurement of the voltage of overhead transmission lines.

[0007] The method includes: acquiring the induced voltage signal of the cable under test detected by each of N pairs of sensing nodes; N≥3; each pair of sensing nodes includes: two sensing nodes arranged radially; one differential voltage signal corresponds to one pair of sensing nodes; the differential voltage signal is calculated based on the two induced voltage signals detected by one pair of sensing nodes;

[0008] A voltage reconstruction algorithm is used to construct a set of three-dimensional nonlinear equations for each differential voltage signal;

[0009] The voltage to ground of the cable under test is calculated based on a system of N ternary nonlinear equations.

[0010] Optionally, the voltage reconstruction algorithm specifically includes:

[0011] The N differential voltage signals are preprocessed; the preprocessing includes filtering and analog-to-digital conversion.

[0012] Based on the preprocessed N differential voltage signals, construct N sets of ternary nonlinear equations;

[0013] From N systems of ternary nonlinear equations, three systems of ternary nonlinear equations are selected and arranged in a permutation and combination to obtain... A combination of three nonlinear equations;

[0014] Solve each of the three-variable nonlinear equation combinations to obtain the corresponding initial voltage value;

[0015] according to The average value of the initial voltage values ​​is calculated to obtain the voltage value to ground of the cable under test.

[0016] Optionally, the combination of the three-variable nonlinear equations specifically includes:

[0017]

[0018] Where r0 is the radius of the metal conductor of the cable under test; h is the thickness of the insulation layer of the cable under test; d1 is the distance between the two sensing nodes in each pair of sensing nodes; d2 is the distance between the sensing node closer to the cable under test and the metal shielding layer in each pair of sensing nodes; R is the radius of the metal shielding layer; ε1 is the dielectric constant of the insulation layer of the cable under test; ε2 is the dielectric constant of air; ε3 is the dielectric constant of the medium in the insulation separator layer; U is the voltage value of the cable under test to ground; x is the abscissa of the position of the axis of the cable under test relative to the center of the N pairs of sensing nodes; y is the ordinate of the position of the axis of the cable under test relative to the center of the N pairs of sensing nodes; u1 is the first differential voltage signal after processing; u2 is the second differential voltage signal after processing; u3 is the third differential voltage signal after processing; and r1 is the distance between the first pair of sensing nodes and the axis of the conductor.

[0019] A non-contact power grid voltage measurement system based on multi-node electric field coupling, wherein the system applies the method described in any one of the above-mentioned methods; the system includes: a multi-pole dual-probe voltage sensor and a voltage reconstruction processing module;

[0020] The voltage reconstruction processing module is connected to the multi-pole dual-probe voltage sensor;

[0021] The multi-pole dual-probe voltage sensor includes: a housing and N pairs of sensing nodes, where N≥3; the housing is a cylindrical structure with a cavity; the cavity extends axially through the upper and lower end faces; the N pairs of sensing nodes are evenly distributed on the inner surface of the cavity; each pair of sensing nodes includes: two sensing nodes arranged radially; the cavity is used to place the cable to be tested.

[0022] Each of the aforementioned sensing nodes is used to detect the induced voltage signal at a corresponding location on the cable under test; a pair of sensing nodes corresponds to a differential voltage signal; the differential voltage signal is calculated based on the two induced voltage signals detected by a pair of sensing nodes.

[0023] The voltage reconstruction processing module is used to construct a set of three-dimensional nonlinear equations for each differential voltage signal using a voltage reconstruction algorithm, and to calculate the voltage value to ground of the cable under test based on the N sets of three-dimensional nonlinear equations.

[0024] Optionally, the voltage reconstruction processing module includes: a preprocessing submodule and a data processing submodule;

[0025] The preprocessing submodule is used to preprocess the N differential voltage signals; the preprocessing includes filtering and analog-to-digital conversion;

[0026] The data processing submodule is used for:

[0027] Based on the preprocessed N differential voltage signals, construct N sets of ternary nonlinear equations;

[0028] From N systems of ternary nonlinear equations, three systems of ternary nonlinear equations are selected and arranged in a permutation and combination to obtain... A combination of three nonlinear equations;

[0029] Solve each of the three-variable nonlinear equation combinations to obtain the corresponding initial voltage value;

[0030] according to The average value of the initial voltage values ​​is calculated to obtain the voltage value to ground of the cable under test.

[0031] Optionally, the system further includes: a metal shielding layer; the metal shielding layer is copper foil;

[0032] The metal shielding layer is disposed on the inner surface of the cavity, and N pairs of the sensing nodes are evenly distributed on the metal shielding layer.

[0033] Optionally, the system further includes: an insulating separator layer;

[0034] An insulating separator is provided between the two sensing nodes of each pair of sensing nodes and between the sensing node and the metal shielding layer.

[0035] Optionally, the material of the insulating separator layer includes foam.

[0036] Optionally, the preprocessing submodule includes: a filter and a digital-to-analog converter;

[0037] The filter is connected to N pairs of sensing nodes; the digital-to-analog converter is connected to the filter.

[0038] Optionally, the system further includes: a display module;

[0039] The display module is connected to the voltage reconstruction processing module; the display module is used to display the voltage value to ground of the cable under test.

[0040] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0041] This invention provides a non-contact measurement method and system for power grid voltage based on multi-node electric field coupling. This method uses the induced signals from multiple sensing nodes around the conductor to inversely calculate the conductor-to-ground voltage, thus achieving non-contact voltage measurement of overhead transmission lines. First, the induced voltage signal of the cable under test detected by each of N pairs of sensing nodes is acquired. A differential signal is calculated based on the two induced voltage signals detected by a pair of sensing nodes. A voltage reconstruction algorithm is used to construct a set of three-variable nonlinear equations for each differential voltage signal. The ground voltage value of the cable under test is calculated based on the N sets of three-variable nonlinear equations. This method allows the cable under test to be located anywhere, rather than only at the center where the induced voltage signal can be detected. Furthermore, the use of paired sensing nodes eliminates potential ground errors caused by the measurement circuit itself and other errors during the measurement process, thus improving the accuracy of the measurement results. Therefore, this invention can achieve accurate voltage measurement at any location. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A flowchart of a non-contact grid voltage measurement method based on multi-node electric field coupling provided in an embodiment of the present invention;

[0044] Figure 2 This is a structural diagram of a non-contact power grid voltage measurement system based on multi-node electric field coupling provided in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the dielectric distribution within the spatial range of the sensor when the cable under test is located at the center of the sensor.

[0046] Figure 4 This is a schematic diagram illustrating the eccentric measurement using a three-pair-dual-induction node voltage sensor.

[0047] Figure 5 A schematic diagram showing the equivalent electric field strength near the sensing node;

[0048] Figure 6 A flowchart illustrating the derivation of the voltage reconstruction theory formula;

[0049] Figure 7 This is a circuit diagram for non-contact voltage measurement based on a three-pole-dual-induction node voltage sensor.

[0050] Figure 8A schematic diagram of the physical test scenario for the hardware device of the non-contact voltage measurement system;

[0051] Figure 9 This is a schematic diagram of a four-pole-dual-induction-node voltage sensor structure.

[0052] Figure 10 A schematic diagram illustrating sensor structure optimization for high-voltage measurement scenarios of overhead power lines;

[0053] Figure 11 This is a schematic diagram of the N-pole dual-sensing node sensor structure model;

[0054] Figure 12 A schematic diagram illustrating sensor placement optimization in a single-circuit overhead line measurement scenario on the same tower.

[0055] Figure 13 A schematic diagram illustrating sensor placement optimization in a measurement scenario for a double-circuit overhead line on the same tower.

[0056] Figure 14 A schematic diagram showing the optimized location and structure of the voltage sensor in a single-circuit, linear overhead line measurement scenario on the same tower.

[0057] Figure 15 This is a schematic diagram of the phasor decomposition of the sensor-induced voltage in a single-circuit, linear overhead line measurement scenario.

[0058] Symbol explanation:

[0059] Multi-pole dual-probe voltage sensor-1, voltage reconstruction processing module-2, filter-3, digital-to-analog converter-4, data processing sub-module-5, display module-6, metal shielding layer-7, cable under test-8, dual sensing node-9. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] The purpose of this invention is to provide a non-contact method and system for measuring grid voltage based on multi-node electric field coupling, which can accurately measure voltage at any location.

[0062] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] Example 1

[0064] like Figure 1 As shown, this embodiment of the invention provides a non-contact measurement method for grid voltage based on multi-node electric field coupling. This method uses the inductive signals from multiple inductive nodes around the conductor to inversely reflect the conductor-to-ground voltage, thereby achieving non-contact measurement of overhead transmission line voltage.

[0065] The method includes:

[0066] Step 100: Obtain the induced voltage signal of the cable under test detected by each of the N pairs of sensing nodes; N≥3; Each pair of sensing nodes includes: two sensing nodes arranged radially; Each pair of sensing nodes corresponds to a differential voltage signal; The differential voltage signal is calculated based on the two induced voltage signals detected by a pair of sensing nodes.

[0067] Step 200: Use the voltage reconstruction algorithm to construct a set of three-dimensional nonlinear equations for each differential voltage signal.

[0068] Step 300: Calculate the voltage to ground of the cable under test based on the N sets of ternary nonlinear equations.

[0069] Specifically, the voltage reconstruction algorithm includes:

[0070] Preprocess N differential voltage signals; preprocessing includes filtering and analog-to-digital conversion.

[0071] Based on the preprocessed N differential voltage signals, construct N sets of ternary nonlinear equations.

[0072] From N systems of ternary nonlinear equations, three systems of ternary nonlinear equations are selected and arranged in a permutation and combination to obtain... A combination of three nonlinear equations.

[0073] Solve each combination of three-variable nonlinear equations to obtain the corresponding initial voltage value.

[0074] according to The average value of the initial voltage values ​​is calculated to obtain the voltage value to ground of the cable under test.

[0075] Example 2

[0076] like Figure 2 As shown, this embodiment of the invention provides a non-contact measurement system for grid voltage based on multi-node electric field coupling. The system includes a multi-pole dual-probe voltage sensor 1 and a voltage reconstruction processing module 2.

[0077] The voltage reconstruction processing module 2 is connected to the multi-pole dual-probe voltage sensor 1. The multi-pole dual-probe voltage sensor 1 includes a housing and N pairs of sensing nodes, where N ≥ 3. The housing is a cylindrical structure with a cavity. The cavity extends axially through the upper and lower end faces. The N pairs of sensing nodes are evenly distributed on the inner surface of the cavity. Each pair of sensing nodes includes two sensing nodes arranged radially. The cavity is used to place the cable under test 8. Each sensing node is used to detect the induced voltage signal at the corresponding position on the cable under test 8. A pair of sensing nodes corresponds to a differential voltage signal. The differential voltage signal is calculated based on the two induced voltage signals detected by a pair of sensing nodes.

[0078] The outer shell can be cylindrical. Specifically, the outer shell can consist of a pair of semi-cylindrical surfaces that, when fastened together, form a complete cylindrical surface. The N pairs of sensing nodes are identical iron sensing nodes.

[0079] The voltage reconstruction processing module 2 is used to construct a set of three-dimensional nonlinear equations for each differential voltage signal using a voltage reconstruction algorithm, and calculate the voltage value to ground of the cable under test 8 based on the N sets of three-dimensional nonlinear equations. Figure 6 This is a flowchart illustrating the derivation of the voltage reconstruction theory formula.

[0080] In one embodiment, the system further includes an insulating separator layer; the insulating separator layer is disposed between the two sensing nodes of each pair of sensing nodes and between the sensing node and the metal shielding layer 7. Specifically, the insulating separator layer is made of foam. Figure 11 This is a schematic diagram of the N-pole dual-sensor node sensor structure model. A metal shielding layer 7 is disposed on the inner surface of the cavity, and N pairs of sensing nodes are evenly distributed on the metal shielding layer 7. Specifically, the metal shielding layer 7 is copper foil, which can shield against the influence of other sources around the cable.

[0081] In one embodiment, the system further includes: a display module 6; the display module 6 is connected to the voltage reconstruction processing module 2; the display module 6 is used to display the voltage value to ground of the cable 8 under test.

[0082] Display module 6 is built using MATLAB and C language and is used to display measured voltage values ​​and waveforms.

[0083] Specifically, the voltage reconstruction processing module 2 includes a preprocessing submodule and a data processing submodule 5.

[0084] The preprocessing submodule is used to preprocess N differential voltage signals; the preprocessing includes filtering and analog-to-digital conversion; the preprocessing submodule includes a filtering module and an A / D conversion module. The filtering module can use filter 3.

[0085] That is, in practice, the preprocessing submodule includes: filter 3 and digital-to-analog converter 4; filter 3 is connected to N pairs of sensing nodes; digital-to-analog converter 4 is connected to filter 3.

[0086] Specifically, the filtering module filters the induced voltage signal acquired by each pair of metal sensing nodes to obtain a well-formed analog voltage signal.

[0087] The A / D conversion module converts the filtered analog signal into a digital signal.

[0088] Then, the MCU data processing module, specifically data processing submodule 5, is used to process the induced voltage signals based on N digital values ​​and their corresponding values. A set of three nonlinear equations was used to calculate the voltage value of the cable under test.

[0089] Specifically, the data processing submodule 5 is used to construct N sets of ternary nonlinear equations based on the preprocessed N differential voltage signals.

[0090] Data processing submodule 5 is used to select three ternary nonlinear equation systems from N ternary nonlinear equation systems and arrange them in a permutation and combination to obtain... A combination of three nonlinear equations.

[0091] The data processing submodule 5 is used to solve each combination of three-variable nonlinear equations to obtain the corresponding initial voltage value.

[0092] Data processing submodule 5 is used to... The average value of the initial voltage values ​​is calculated to obtain the voltage value to ground of the cable 8 under test.

[0093] In non-contact voltage measurement, a multi-pole dual-probe voltage sensor 1 is wrapped around the cable under test 8. Thus, each pair of metal sensing nodes in the sensor acquires N differential voltage signals by sensing the electric field signal radiated by the voltage of the cable under test 8. Let u be the voltage signal acquired by the i-th pair of metal sensing nodes. i Let i = 1, 2, ..., N. The solution is obtained from N induced voltage signals after filtering, analog-to-digital conversion, etc. After averaging a set of three nonlinear equations to further improve accuracy, the voltage of the cable under test can be obtained.

[0094] The solution formula is based on the theory of electric field radiation, which has only three unknowns: U, x, and y. The system of equations can be solved.

[0095] The solution formula in data processing submodule 5 can be expanded as the number of measurement points, i.e., the logarithm N of the sensing nodes, increases. If N > 3, then the following can be obtained: The system of equations can be solved to obtain The measurement results can be averaged to further improve the accuracy of the measurement results.

[0096] In practical applications, the system's structure consists of three parts: a signal acquisition section using sensors, a signal processing section using bandpass filtering, analog-to-digital conversion, and MCU data processing, and a result display section for digital display.

[0097] The system provided in this embodiment is characterized by its simple structure, low cost, and ease of operation.

[0098] Example 3

[0099] To save costs, the sensor pole number N = 3 is selected. When the three pairs of sensing nodes are symmetrically distributed about the sensor center, it can be called a three-pole-dual-sensing-node voltage sensor. Taking a three-pole-dual-sensing-node voltage sensor as an example:

[0100] The system provided in this embodiment of the invention is highly dependent on the key technical principles of this voltage sensor, the theoretical basis of which is as follows.

[0101] First, the equation concerning the electric displacement vector in Maxwell's equations is:

[0102]

[0103] Integrating both sides of the equation, we get:

[0104]

[0105] The formula obtained after integration is Gauss's theorem, which describes how electric charge generates an electric field.

[0106] In practical applications, low-voltage transmission cables are considered as long, straight cylindrical conductors. Ignoring the influence of the radial conduction time of the electromagnetic field, the electric field around the conductor can be regarded as a quasi-electrostatic field. A closed cylindrical Gaussian surface of length l and radius R can be coaxially wrapped around a unit length of conductor. Based on Gauss's law, integrating the electric displacement vector with respect to the Gaussian surface at radius R yields... Therefore, the electric displacement vector is:

[0107]

[0108] From the corresponding property equation It can be seen that the electric field strength at a location R, a distance R from the center of the conductor, is:

[0109]

[0110] Where ρ is the charge density of a single conductor in an overhead line, and ε is the dielectric constant of the medium at point R.

[0111] Taking low-voltage power transmission aluminum core cables as an example, Figure 3 This refers to the dielectric distribution within the spatial range of the sensor when the cable is located at the center of the sensor.

[0112] Assuming the radius of the aluminum core conductor inside the cable is r0, the electric field distribution around the conductor is as follows. Where ε1 is the dielectric constant of the conductor insulation layer; ε2 is the dielectric constant of air; and ε3 is the dielectric constant of the insulating medium.

[0113]

[0114] Depend on It can be seen that the potential difference between any two points in the space surrounding the cable can be expressed in the form of an electric field integral. That is:

[0115]

[0116] In actual measurements, the three-pole-dual-induction node electric field sensor is wrapped with a cable, and the shielding layer is grounded. However, under normal circumstances, it cannot be guaranteed that the cable will be centered on the sensor, so the explanation will focus on the general case where the cable deviates from the center of the sensor.

[0117] Figure 4 This illustrates the case of eccentric measurement using a three-pole-dual-induction node voltage sensor. In the figure, assuming the conductor's central axis is not deviated from the sensor center, the electric field distribution around the conductor differs in the three directions R1, R2, and R3. However, the electric field intensity E near the induction node in each direction can be considered constant. i The electric field strength near the sensing node when the conductor is at the center of the sensor, with R1, R2, and R3 being the radii of the shielding layer, can be considered as three equivalent cases, such as... Figure 5 As shown, and satisfying the following functional relationship:

[0118]

[0119] From this, we can deduce the conductor-to-ground voltage U and its electric field strength E at the inner induction nodes in three directions. i (R i The relationship between )

[0120]

[0121] In the formula, U is the voltage of the conductor relative to ground, and R is the conductor diameter. This establishes the relationship between the voltage of the conductor relative to ground and the electric field strength around it.

[0122] Then, calculate the electric field strength E at the plate. i (R iThe calculation of ) can be performed. Taking the sensor dual-sensing node 9 substructure at point A as an example, the following can be obtained: Figure 4 The electric field intensity at the induction node a.

[0123]

[0124] The voltage u1 between the dual induction nodes a and a' can be measured by an external sampling circuit, and the voltages u1′ and u1″ between the dual induction node 9 and the ground plane can be obtained by the following relationship.

[0125]

[0126]

[0127]

[0128] Therefore, the electric field strength E1(R1) at the induction node a can be obtained.

[0129]

[0130] Similarly, the electric field intensity E in other directions can be obtained. i (R i ).

[0131]

[0132] Finally, a preliminary expression for the voltage U to be measured can be obtained:

[0133]

[0134] Then, the position of the cable shaft center relative to the sensor center is analyzed. To further simplify the positional relationships and more easily obtain the mathematical relationship between distances R1, R2, R3 and the relative position coordinates (x, y) of the cable shaft center. Figure 4 In the diagram, P is the cable axis, O is the sensor center point, and points A, B, and C represent the dual-induction node substructures of voltage sensors ①, ②, and ③, respectively. A Cartesian coordinate system is established with O as the origin, the line containing OA as the y-axis, and the line perpendicular to OA and passing through point O as the x-axis. The distances from the induction nodes closest to the cable at the three locations to the cable center P are R1, R2, and R3, respectively. The coordinates of the conductor axis P are (x, y). ∠AOB=∠BOC=∠COA=120°. Through geometric analysis, the Pythagorean theorem can be applied to obtain the relationship between the axis coordinates (x, y) and R1, R2, and R3.

[0135]

[0136] Based on the above theoretical formulas, we can obtain the following system of equations, which has three unknowns: U, x, and y, and can be solved.

[0137] The three-variable nonlinear equation system specifically includes:

[0138]

[0139] Where r0 is the radius of the metal conductor of the cable under test; h is the thickness of the insulation layer of the cable under test; d1 is the distance between the two sensing nodes in each pair of sensing nodes; d2 is the distance between the sensing node closer to the cable under test and the metal shielding layer in each pair of sensing nodes; R is the radius of the metal shielding layer; ε1 is the dielectric constant of the insulation layer of the cable under test; ε2 is the dielectric constant of air; ε3 is the dielectric constant of the medium in the insulation separator layer; U is the voltage value of the cable under test to ground; x is the abscissa of the position of the axis of the cable under test relative to the center of the N pairs of sensing nodes; y is the ordinate of the position of the axis of the cable under test relative to the center of the N pairs of sensing nodes; u1 is the first differential voltage signal after processing; u2 is the second differential voltage signal after processing; u3 is the third differential voltage signal after processing; and r1 is the distance between a pair of sensing nodes and the axis of the conductor.

[0140] The system uses a three-pole-dual-induction node electric field sensor to infer the cable voltage by collecting the electric field at the induction node near the cable. In practice, it uses the electric field strength at the surface of the induction node closest to the cable. Furthermore, the cable selected for the measurement model is general; for some special cables, the voltage measured by this system will inevitably differ significantly. Moreover, the accuracy of the measurement results is independent of the cable location; even if the cable to be measured is located anywhere other than the center of the sensor, the accuracy can be guaranteed to reach an acceptable level. Compared to traditional fixed-parameter non-contact measurement devices, this test system provides more accurate measurement results. Figure 7 This is a circuit diagram for non-contact voltage measurement based on a three-pole-dual-induction node voltage sensor.

[0141] In this embodiment, the measurement system acquires the input voltage signal through three pairs of sensing nodes a-a', b-b', and c-c' of a three-pair-dual-sensor electric field sensor. Based on the electric field formed by the cable under test 8 in the surrounding space, the three pairs of sensing nodes of the sensor acquire the potential difference between each pair of sensing nodes in the electric field space, which serves as the input voltage signal for the circuit processing module, named u1, u2, and u3 respectively. Next, the three voltage signals undergo a series of processing steps in the signal processing circuit, including a filtering module, an A / D conversion module, and an MCU digital processing module. The filtering module contains three identical filtering circuits, each with its input connected to a dual-sensor node to receive the input voltage signal. After filtering by the three circuits, the signal is output to the A / D conversion module. The filtered output voltage signal is an analog signal. To facilitate data processing by the MCU data processing module, the A / D conversion module converts this analog signal into a digital signal. In this embodiment, an analog-to-digital converter (ADC) is used to digitize the analog signal. For a nominal 50Hz input signal, this measuring device uses a 3kHz sampling frequency for the ADC to sample the output signal from the signal processing circuit, providing 256 samples within 100ms to prepare for Fast Fourier Transform and voltage reconstruction algorithm processing in the MCU data processing module. The MCU data processing module acquires the digital signal output from the digital-to-analog converter, solves the voltage under test using a computer program based on the voltage reconstruction equations, and obtains and displays the accurate measurement result. This measurement system performs non-contact voltage measurement via a single wire, capable of measuring both DC and AC voltages, offering convenient operation and good practicality.

[0142] Figure 8 This is a physical test scenario for the hardware device of the non-contact voltage measurement system provided by the present invention. The hardware device of the system consists of a sensor probe and two circuit boards connected by an HDMI interface. One circuit board is equipped with a signal input interface and a signal processing circuit, while the other circuit board is equipped with a data processing circuit, a data transmission interface, and a power interface.

[0143] Example 4

[0144] When measuring, a four-pole dual-inductive node voltage sensor with N=4 poles is used, and when the four poles are symmetrically distributed, it is named a four-pole dual-inductive node voltage sensor. The main focus is on analyzing the position of the cable axis relative to the sensor center, based on the above.

[0145] Figure 9The diagram illustrates a four-pole-dual-inductive node voltage sensor structure. In the figure, P is the cable axis, O is the sensor center point, and points A, B, C, and D represent the dual-inductive node substructures of voltage sensors ①, ②, ③, and ④, respectively. A Cartesian coordinate system is established with O as the origin, the line containing OA as the y-axis, and the line containing OD as the x-axis. The distances from the inductive node closest to the cable to the cable center P at the four locations are R1, R2, R3, and R4, respectively. The coordinates of the conductor axis P are (x, y). ∠AOB = ∠BOC = ∠COD = ∠DOA = 90°. Through geometric analysis, the Pythagorean theorem can be applied to obtain the relationship between the axis coordinates (x, y) and R1, R2, R3, and R4.

[0146]

[0147] Furthermore, by extending the relation, a preliminary expression for the voltage U to be measured is obtained.

[0148]

[0149] The final result is a system of equations as shown below, which has three unknowns: U, x, and y, and can be solved.

[0150]

[0151] By combining any three equations from the above system of equations, a value of the voltage to be measured can be obtained. Finally, the value can be calculated. The average value of these results can be calculated to further improve the accuracy of the measurement. If even higher measurement accuracy is desired, the number of sensor poles can be further increased, but this also increases the cost of the measurement system and the complexity of the solution.

[0152] Example 5

[0153] For high-voltage transmission lines, such as 110kV / 220kV overhead lines, which use bare conductors, the electric field distribution around the conductor can be removed from the electric field distribution of the insulation layer when considering the surrounding electric field distribution. The following relationship is obtained.

[0154]

[0155] Where r0 is the radius of the conductor, and point R can be considered as a zero potential point. From this, the following voltage reconstruction relationship can be obtained.

[0156]

[0157] Considering the unique characteristics of overhead power lines, the sensor is placed directly beneath them. Furthermore, the internal structure of the sensor has been optimized to accommodate the distribution of small-angle, arc-shaped sensor sensing nodes and measurement points under overhead power lines.

[0158] Figure 10 This paper optimizes the sensor structure for high-voltage measurement scenarios of overhead power lines. In the diagram, P is the conductor axis, point B is directly below the conductor, and points A and C are equidistant from B; ∠BOA = ∠BOC, and the precise value of this angle can be measured using tools; the origin O is the center of the circle determined by the three sensing node positions within the sensor. Dual-sensor node substructures of voltage sensors ①, ②, and ③ are placed at points A, B, and C respectively. A Cartesian coordinate system is established with O as the origin, the line containing OB as the y-axis, and the line perpendicular to OB and passing through point O as the x-axis, as shown below. Figure 10 As shown. The distances of the three points from the center O of the conductor are R1, R2, and R3, respectively, and the coordinates of the conductor axis P are (x, y). In particular, when ∠BOA=∠BOC=60°, through geometric analysis, the Pythagorean theorem can be applied to obtain the relationship between the coordinates of the axis (x, y) and R1, R2, and R3.

[0159]

[0160] In addition, for ease of measurement, other special angles can be used, such as 45°, 30°, 15°, etc., and the sensor radius will gradually increase for ease of manufacturing and installation. Combining the above, a system of equations can be obtained, and solving them will yield the measurement results.

[0161] The above content only applies to a single overhead line. However, most high-voltage transmission lines are overhead lines with multiple conductors, such as single-circuit or double-circuit lines on the same tower. Based on the principle of electric field superposition, it is necessary to decompose the sensor voltage and optimize the voltage reconstruction algorithm. Figures 12-13 This demonstrates sensor placement optimization in measurement scenarios for single-circuit and double-circuit overhead lines on the same tower. Figure 12 In the diagram, points A, B, and C are cable detection locations in a single-circuit overhead line measurement scenario on the same tower, while point D is the location of the voltage sensor. Figure 13 In the diagram, points A, B, and C are the cable detection locations in a double-circuit overhead line measurement scenario on the same tower, and point D is the location of the voltage sensor. The following explanation uses a single-circuit overhead line measurement scenario on the same tower as an example.

[0162] Figure 14This paper optimizes the location and structure of voltage sensors for measuring single-circuit overhead lines on a single tower. Generally, the height of the overhead conductor above the ground and the distance between conductors can be measured at the tower location. For ease of installation and measurement, the sensor is placed on the tower directly below the overhead conductor. After measuring the sensor's height above the ground, the position coordinates of the overhead line relative to the center of the sensor's positioning circle can be determined, eliminating the need to solve a system of equations to find the position coordinates. Furthermore, since multiple conductors act simultaneously, the sensor's output response is the superposition of the responses produced by each conductor acting individually. Therefore, phasor decomposition of the sensor's output response is necessary.

[0163] Figure 15 This diagram illustrates the phasor decomposition of the sensor-induced voltage in a single-circuit, linear overhead line measurement scenario. In the diagram, ①②③ correspond to the phases of the three-phase voltages ABC of the overhead line being 0°, 120°, and 240°, respectively. Specifically, it shows the phasor decomposition of the induced voltage. Because of symmetry, it can be clearly known that it is related to... In phase, that is Based on the sensor's sensed voltage relative to The phase difference is obtained sequentially The phase of the voltage is determined, and the three voltages are decomposed into phasors to obtain the three induced voltages u generated by the sensor for each phase conductor. Ai u Bi u Ci (i = 1, 2, 3). Finally, the voltage of each phase conductor of the overhead line is obtained by solving the equations, thus completing the non-contact measurement of the overhead line voltage.

[0164] The multi-pole dual-probe voltage sensor 1 can adopt a ring structure in low-voltage measurement scenarios and an arc-shaped structure in high-voltage measurement scenarios. The arc-shaped structure is optimized based on the special characteristics of overhead lines, adapting to the small-angle arc-shaped distribution of sensor sensing nodes under overhead lines. The arc-shaped distribution angle of the sensor sensing nodes can be specific angles such as 45°, 30°, and 15° to facilitate voltage reconstruction.

[0165] The multi-pole dual-probe voltage sensor 1 can perform multi-objective optimization analysis under parameters such as distance from overhead lines, arc distribution angle of sensing nodes, measurement accuracy, and sensor cost to obtain the most suitable sensor structure and location distribution.

[0166] An arc-shaped sensor suitable for voltage measurement of high-voltage overhead lines optimizes its voltage reconstruction algorithm based on the principle of voltage superposition, performing phasor decomposition on the sensor's induced voltage. This allows for the decomposition of complex multi-conductor environments into single target environments, which are then solved one by one.

[0167] The purpose of this invention is to overcome the shortcomings of the prior art, improve the theoretical depth, and provide a non-contact measurement system for power grid voltage based on a multi-pole dual-induction node voltage sensor. By sensing the electric field intensity generated in the space around the line under test through multiple pairs of metal induction nodes, multiple induced voltages related to the line under test are obtained, and multiple nonlinear algebraic equations about the voltage under test and unknown position parameters are obtained to solve the voltage signal of the line under test, thus completing the non-contact measurement of the voltage of the line under test.

[0168] The non-contact measurement method for grid voltage based on multi-node electric field coupling provided by this invention ensures acceptable accuracy even when the cable to be measured is located anywhere other than the center of the sensor. It eliminates potential ground errors caused by the measurement circuit itself and other errors in the measurement process by using paired sensing nodes. It is suitable for AC and DC voltage monitoring. It is suitable for high-bandwidth voltage level measurements. It can further improve the accuracy of measurement results by expanding the number of detection points inside the sensor.

[0169] This invention provides an objective analysis and study of the electric field level based on the principle of electric field radiation. By analyzing the electric field strength at multiple locations around the cable and considering the number of unknown parameters, it inversely derives the voltage of the cable under test, forming a non-contact voltage measurement system primarily composed of a multi-pole, dual-induction node voltage sensor. The advantages of this system are: based on the theoretical analysis of the electric field around the cable, the voltage to be measured is solved by a system of three nonlinear equations, resulting in high accuracy. Furthermore, the measurement accuracy can be further improved by expanding the number of measurement points within the sensor, without increasing cost. In addition, even if the cable to be measured is located anywhere other than at the center of the sensor, the accuracy can still be ensured to reach an acceptable level.

[0170] The non-contact voltage measurement system of this invention also has the following beneficial effects:

[0171] (1) The voltage sensor on which the system depends includes 2N (N pairs) metal sensing nodes and a metal shielding layer. It is small in size, easy to carry, and has low manufacturing cost, which is conducive to large-scale production applications. Even if the cable to be measured is located anywhere rather than the center of the sensor, the accuracy can be ensured to reach an acceptable level.

[0172] (2) The measurement system senses the electric field strength generated around the cable under test based on the principle of electric field radiation, and obtains the voltage signal of the line under test in this way. It has good adaptability and can be used for AC and DC voltage monitoring.

[0173] (3) It uses paired sensing nodes to eliminate potential ground errors caused by the measurement circuit itself and other errors in the measurement process.

[0174] (4) In non-contact voltage measurement, N differential induced voltage signals can be obtained simultaneously through N pairs of sensing nodes. Any three signals and their corresponding three nonlinear equations can be used to form a... Solving this system of three nonlinear equations yields the following results: Calculating the average of the measurement results can further improve measurement accuracy. The larger N is, the higher the accuracy of the measurement results, but the higher the cost and the higher the system complexity.

[0175] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0176] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A non-contact measurement method for grid voltage based on multi-node electric field coupling, characterized in that, The method describes how to perform non-contact voltage measurement of overhead transmission lines by inverting the voltage between the conductor and ground using the induction signals from multiple induction nodes around the conductor. The method includes: acquiring the induced voltage signal of the cable under test detected by each of N pairs of sensing nodes; N≥3; each pair of sensing nodes includes: two sensing nodes arranged radially; one differential voltage signal corresponds to one pair of sensing nodes; the differential voltage signal is calculated based on the two induced voltage signals detected by one pair of sensing nodes; A voltage reconstruction algorithm is used to construct a set of three-dimensional nonlinear equations for each differential voltage signal; The voltage to ground of the cable under test is calculated based on a system of N ternary nonlinear equations. The voltage reconstruction algorithm specifically includes: The N differential voltage signals are preprocessed; the preprocessing includes filtering and analog-to-digital conversion. Based on the preprocessed N differential voltage signals, construct N sets of ternary nonlinear equations; From N systems of ternary nonlinear equations, three systems of ternary nonlinear equations are selected and arranged in a permutation and combination to obtain... A combination of three nonlinear equations; Solve each of the three-variable nonlinear equation combinations to obtain the corresponding initial voltage value; according to The average value of the initial voltage values ​​is calculated to obtain the voltage value to ground of the cable under test.

2. The non-contact measurement method for grid voltage based on multi-node electric field coupling according to claim 1, characterized in that, The combination of the three-variable nonlinear equations specifically includes: Where r0 is the radius of the metal conductor of the cable under test; h is the thickness of the insulation layer of the cable under test; d1 is the distance between the two sensing nodes in each pair of sensing nodes; d2 is the distance between the sensing node closer to the cable under test and the metal shielding layer in each pair of sensing nodes; R is the radius of the metal shielding layer; ε1 is the dielectric constant of the insulation layer of the cable under test; ε2 is the dielectric constant of air; ε3 is the dielectric constant of the medium in the insulation separator layer; U is the voltage value of the cable under test to ground; x is the abscissa of the position of the axis of the cable under test relative to the center of the N pairs of sensing nodes; y is the ordinate of the position of the axis of the cable under test relative to the center of the N pairs of sensing nodes; u1 is the first differential voltage signal after processing; u2 is the second differential voltage signal after processing; u3 is the third differential voltage signal after processing; and r1 is the distance between the first pair of sensing nodes and the axis of the conductor.

3. A non-contact power grid voltage measurement system based on multi-node electric field coupling, characterized in that, The system employs the method described in any one of claims 1-2; the system comprises: a multi-pole dual-probe voltage sensor and a voltage reconstruction processing module; The voltage reconstruction processing module is connected to the multi-pole dual-probe voltage sensor; The multi-pole dual-probe voltage sensor includes: a housing and N pairs of sensing nodes, where N≥3; the housing is a cylindrical structure with a cavity; the cavity extends axially through the upper and lower end faces; the N pairs of sensing nodes are evenly distributed on the inner surface of the cavity; each pair of sensing nodes includes: two sensing nodes arranged radially; the cavity is used to place the cable to be tested. Each of the aforementioned sensing nodes is used to detect the induced voltage signal at a corresponding location on the cable under test; a pair of sensing nodes corresponds to a differential voltage signal; the differential voltage signal is calculated based on the two induced voltage signals detected by a pair of sensing nodes. The voltage reconstruction processing module is used to construct a set of three-dimensional nonlinear equations for each differential voltage signal using a voltage reconstruction algorithm, and to calculate the voltage value to ground of the cable under test based on the N sets of three-dimensional nonlinear equations. The voltage reconstruction processing module includes: a preprocessing submodule and a data processing submodule; The preprocessing submodule is used to preprocess the N differential voltage signals; the preprocessing includes filtering and analog-to-digital conversion; The data processing submodule is used for: Based on the preprocessed N differential voltage signals, construct N sets of ternary nonlinear equations; From N systems of ternary nonlinear equations, three systems of ternary nonlinear equations are selected and arranged in a permutation and combination to obtain... A combination of three nonlinear equations; Solve each of the three-variable nonlinear equation combinations to obtain the corresponding initial voltage value; according to The average value of the initial voltage values ​​is calculated to obtain the voltage value to ground of the cable under test.

4. The non-contact grid voltage measurement system based on multi-node electric field coupling according to claim 3, characterized in that, The system further includes: a metal shielding layer; the metal shielding layer is copper foil; The metal shielding layer is disposed on the inner surface of the cavity, and N pairs of the sensing nodes are evenly distributed on the metal shielding layer.

5. The non-contact grid voltage measurement system based on multi-node electric field coupling according to claim 4, characterized in that, The system also includes: an insulating separation layer; An insulating separator is provided between the two sensing nodes of each pair of sensing nodes and between the sensing node and the metal shielding layer.

6. The non-contact grid voltage measurement system based on multi-node electric field coupling according to claim 5, characterized in that, The insulating separator layer is made of foam.

7. The non-contact grid voltage measurement system based on multi-node electric field coupling according to claim 3, characterized in that, The preprocessing submodule includes: a filter and a digital-to-analog converter; The filter is connected to N pairs of sensing nodes; the digital-to-analog converter is connected to the filter.

8. The non-contact grid voltage measurement system based on multi-node electric field coupling according to claim 3, characterized in that, The system also includes: a display module; The display module is connected to the voltage reconstruction processing module; the display module is used to display the voltage value to ground of the cable under test.

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