Coaxial double-coil structure and double-channel broadband current measurement system and method

Abstract

The invention discloses a coaxial dual-coil structure and a dual-channel broadband current measurement system and method, and the structure comprises two sets of PCB Rogowski coils which are coaxially disposed in a same mechanical housing, and the two sets of PCB Rogowski coils are a first Rogowski coil and a second Rogowski coil. The first Rogowski coil is a high-frequency measurement Rogowski coil and is used for detecting lightning impulse signals; the second Rogowski coil is a power frequency measurement Rogowski coil and is used for detecting a power frequency signal; the first Rogowski coil adopts a self-integration working mode, the second Rogowski coil adopts a composite integration working mode, the first Rogowski coil and the second Rogowski coil share the same hole, a high-voltage center conductor penetrates through the hole to provide a measured current, and the first Rogowski coil and the second Rogowski coil suppress electromagnetic coupling through a middle composite shielding partition plate and a preset axial distance. According to the invention, a coaxial double-coil structure, double-channel frequency division processing and intelligent identification fusion are combined, and simultaneous measurement of a power frequency low-frequency signal and a high-frequency transient impact signal is realized.

Description

Technical Field

[0001] This invention relates to the field of power system measurement, specifically to a coaxial dual-coil structure, a dual-channel broadband current measurement system and method. Background Technology

[0002] With the increasing complexity of power grid structures, the continuous rise in the proportion of renewable energy grid integration, and the widespread application of power electronic devices, there are more and more non-power frequency current components in the power grid, such as harmonics, electromagnetic transients, electrical equipment switching transients, and lightning impulses. The frequency range of these signals ranges from the power frequency (50Hz) to several MHz or even higher, bringing new challenges to current measurement and electromagnetic compatibility monitoring.

[0003] Traditional current measurement equipment mainly includes electromagnetic current transformers (CTs), shunts, Hall effect current sensors, optical current transformers (OpticalCTs), and Rogowski coils. The shortcomings of existing technologies are mainly reflected in the following aspects:

[0004] (1) The structural form or manufacturing method causes a trade-off in sensitivity or bandwidth.

[0005] Taking US-9448258-B2 as an example, it uses a rigid PCB with a bendable hinge structure to construct a "polygonal cross-section tubular" Rogowski coil. Although manufacturing consistency is improved, its structure is still a combination of multiple PCB panels or hinges, which may present challenges in terms of installation accuracy, geometric consistency, and inter-turn spacing control. Furthermore, using only a PCB winding structure may limit the number of coil turns, cross-sectional area, and loop geometry, thus affecting mutual inductance. Value and low-frequency sensitivity.

[0006] (2) The integrator design still suffers from low-frequency drift and phase deviation problems.

[0007] Taking US-9588147-B2 as an example, although this patent proposes an improved integrator design to remove DC bias and improve phase response, its description already points out that in the conventional structure, At 60Hz, the phase shift is only about 1.2, resulting in a significant phase shift in the integrator during power frequency measurements. Although the new circuit design solves some of the problems, its target application is still mainly power frequency measurements, and it does not fully cover the integration response requirements of MHz-level fast impulse signals. In addition, this scheme has little or no specific description of the sensor head structure, channel switching, and wideband integrated system. Therefore, while the accuracy is acceptable at low frequencies, for ultra-wideband (e.g., power frequency, harmonics, high-frequency transients, lightning impulses) integrated measurements, problems such as integration drift, phase error, insufficient low-frequency coverage, or high-frequency response degradation still exist.

[0008] (3) Lack of anti-interference, channel fusion and intelligent control capabilities.

[0009] Taking CN102944716A and US-11125783-B2 as references, the former, although using a PCB structure for lightning measurement, mainly focuses on structural implementation and frequency response, without fully addressing anti-interference design in electromagnetic interference (such as high-voltage electric fields, lightning electromagnetic pulses, and power supply interference) or strong coupling environments. The latter, while possessing wireless control and remote capabilities, still relies on a single-channel Rogowski + integration + wireless output architecture, failing to embody a system architecture of "multi-channel (power frequency / lightning), intelligent event recognition, channel switching / fusion output." It is still insufficient for power system monitoring scenarios simultaneously involving power frequency, harmonics, and high-frequency transients. Therefore, existing technologies have gaps in high anti-interference capabilities, automatic cross-frequency channel switching, and data fusion capabilities in complex power grid environments.

[0010] (4) Engineering manufacturing and batch consistency issues

[0011] While the aforementioned patents largely emphasize PCB or modular structures, actual manufacturing still faces engineering challenges such as turns control, interlayer alignment, via consistency, shielding structure manufacturing and installation errors, mutual inductance matching, and inter-channel delay correction. Especially under conditions of wide bandwidth, high voltage levels, and harsh installation environments (high-voltage indoor environments, frequent lightning strikes), the reliability, consistency, and ease of on-site testing / maintenance of the sensor head are still difficult to fully meet. Therefore, from the perspectives of manufacturing cost, production consistency, ease of on-site installation, and maintenance replaceability, the existing structure does not yet fully meet the needs of large-scale engineering applications in power systems.

[0012] (5) The trade-off between frequency coverage and accuracy has not been fully resolved.

[0013] The current common problem is that covering the range from power frequency to MHz while simultaneously ensuring amplitude accuracy, phase accuracy, response speed, and dynamic range in both the power frequency harmonic range and the lightning impulse range presents a significant technical challenge. For example, some Rogowski coil systems exhibit large drift and slow DC zero-point recovery at low frequencies; and low cutoff frequencies or distorted responses at high frequencies. Alternatively, they may suffer from excessively long rise times and insufficient bandwidth in extreme transient measurements. Therefore, truly achieving "integrated, high-precision, and high-dynamic" measurements from power frequency to MHz is impossible.

[0014] Therefore, existing technologies have not yet provided a system solution that can truly balance low-frequency accuracy, high-frequency response, wide-band coverage, and real-time event recognition. Summary of the Invention

[0015] The technical problem this invention aims to solve is that existing measuring equipment cannot simultaneously measure both low-frequency power frequency signals and high-frequency transient impulse signals, and suffers from low measurement accuracy and slow response speed. The purpose of this invention is to provide a coaxial dual-coil structure, dual-channel wideband current measurement system and method. This invention combines a coaxial dual-coil structure, dual-channel frequency division processing, and intelligent identification fusion to achieve simultaneous measurement of low-frequency power frequency signals and high-frequency transient impulse signals. It is suitable for accurate measurement and classification output of current signals ranging from power frequency to several MHz, including power frequency, power grid harmonics, switching transients, and lightning impulses.

[0016] This invention is achieved through the following technical solution:

[0017] In a first aspect, the present invention provides a coaxial dual-coil structure, comprising: two sets of PCB Rogowski coils coaxially arranged within the same mechanical housing, namely a first Rogowski coil and a second Rogowski coil;

[0018] The first Rogowski coil is a high-frequency measurement Rogowski coil used to detect lightning impulse signals;

[0019] The second Rogowski coil is a power frequency measurement Rogowski coil, used to detect power frequency signals;

[0020] The first Rogowski coil adopts a self-integrating working mode, and the second Rogowski coil adopts a composite integration working mode. The first and second Rogowski coils share the same opening, through which a high-voltage center conductor is inserted to provide the measured current. Furthermore, the two coils are separated by a composite shielding partition and a preset axial distance to suppress electromagnetic coupling.

[0021] Furthermore, the first Rogowski coil has a two-layer PCB structure, uses twisted pair wide-pitch winding with a wire width ranging from 0.2 to 0.3 mm and a number of turns ranging from 60 to 100.

[0022] The second Rogowski coil has a four-layer PCB structure, uses twisted-pair differential winding with an outer ground shield, and has a wire width ranging from 0.1 to 0.2 mm and a number of turns ranging from 200 to 300.

[0023] Furthermore, the composite shielding partition is a three-layer composite structure consisting of a high magnetic permeability material layer, a conductive material layer, and a supporting material layer;

[0024] The high permeability material layer uses permalloy or nanocrystalline alloy, the conductive material layer uses oxygen-free copper foil, and the support material layer uses polyimide or epoxy glass cloth.

[0025] Furthermore, the preset axial spacing is three times the outer diameter of the first or second Rogowski coil.

[0026] Furthermore, the preset axial spacing is 80~120mm.

[0027] Secondly, the present invention provides a dual-channel broadband current measurement system, the measurement system comprising:

[0028] A high-voltage center conductor is used to supply the measured current and generate a changing magnetic field around it;

[0029] The coaxial dual-coil structure, using one of the coaxial dual-coil structures described above, is used to output a voltage signal proportional to the rate of change of the measured current after sensing a change in magnetic flux. The first Rogowski coil outputs a first voltage signal, and the second Rogowski coil outputs a second voltage signal.

[0030] The first integrator is a self-generating integrator connected to the first Rogowski coil; the second integrator is a composite external integrator connected to the second Rogowski coil.

[0031] The first ADC converter, as a lightning channel ADC, is connected to the first integrator and outputs a first current digital signal; the second ADC converter, as a power frequency channel ADC, is connected to the second integrator and outputs a second current digital signal; and the first ADC converter and the second ADC converter have hardware timestamp synchronization function.

[0032] The FPGA intelligent signal processing module is used to extract features from the first and second current digital signals to obtain multi-dimensional features; based on the multi-dimensional features, it uses a machine learning model and a dual-threshold strategy to identify the signal type and obtain the signal identification result; based on the signal identification result, it automatically adjusts the weights of each channel; and based on the signal identification result and the corresponding channel weights, it fuses the results and outputs them.

[0033] Furthermore, the composite external integrator is a cascaded structure of passive integrator, active integrator and high-frequency filter, and the active integrator branch includes a feedback discharge resistor.

[0034] Furthermore, multidimensional features include time-domain features, frequency-domain features, and statistical features;

[0035] Time-domain characteristics include rise time, peak value, current pulse width, RMS value, and waveform symmetry; frequency-domain characteristics include FFT spectrum distribution, harmonic content, and energy concentration; statistical characteristics include waveform factor, zero-crossing rate, and root mean square deviation.

[0036] Thirdly, the present invention provides a dual-channel broadband current measurement method, characterized in that the method includes:

[0037] The power frequency signal and / or lightning impulse signal of the measured current are obtained through a coaxial dual-coil structure.

[0038] Based on the power frequency signal and / or lightning impulse signal, the first current digital signal and the second current digital signal are obtained through the corresponding dual-channel integrator and ADC converter;

[0039] Feature extraction is performed on the first current digital signal and the second current digital signal respectively to obtain multidimensional features;

[0040] Based on multidimensional features, a machine learning model and a dual-threshold strategy are used to identify signal types and obtain signal identification results.

[0041] Based on the signal recognition results, the weights of each channel are automatically adjusted; and based on the signal recognition results and corresponding channel weights, an adaptive weighted fusion is performed to obtain the fusion result; and

[0042] Based on channel weights and signal types, different output modes are automatically selected for output.

[0043] Furthermore, based on the signal recognition results, the weights of each channel are automatically adjusted, including:

[0044] If the signal identification result is a power frequency signal, then increase the weight of the power frequency channel to make the active integration result the dominant output.

[0045] If the signal identification result is a lightning impulse signal, the weight of the lightning channel is increased to enhance the high-frequency response;

[0046] If the signal recognition result indicates that both the power frequency signal and the lightning impulse signal occur simultaneously, then both the power frequency channel and the lightning channel maintain their initial weights and output both the power frequency signal and the lightning impulse signal.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] This invention discloses a coaxial dual-coil structure, a dual-channel wideband current measurement system and method. Combining the coaxial dual-coil structure, dual-channel frequency division processing, and intelligent identification fusion, it achieves simultaneous measurement of low-frequency power frequency signals and high-frequency transient impulse signals, unifying high precision at low frequencies with rapid response at high frequencies. Compared to traditional single-coil Rogowski sensors, this invention significantly improves bandwidth, linearity, and anti-interference capabilities. Its coaxial dual-coil design effectively reduces errors caused by magnetic field inhomogeneity, the composite integral structure expands the system response range, and the FPGA intelligent processing module fully automates signal discrimination and channel switching, ensuring continuous and stable measurement of wideband current signals.

[0049] 1. Truly covers a wide frequency band: Through the coaxial dual-coil structure and dual-channel targeted optimization, the system can achieve effective measurement in the frequency band from power frequency to several MHz, taking into account both the 0.2-level accuracy of power frequency and the high fidelity requirements of lightning impulse (amplitude error and wavefront time difference meet the predetermined indicators).

[0050] 2. Compromise and optimization of the conflict between sensitivity and high-frequency response: The number of turns, board layers and wiring method of the first Rogowski coil and the second Rogowski coil are optimized respectively, so that the second Rogowski coil has high sensitivity in the low frequency band and the first Rogowski coil has good fidelity in the high frequency band. Furthermore, the two can coexist by suppressing mutual coupling through composite shielding and axial spacing.

[0051] 3. Easily manufactured and highly resistant to interference: The use of PCB coils combined with coaxial composite shielding design improves manufacturing consistency and facilitates mass production. At the same time, differential twisted pair wiring and shielding layer significantly enhance common mode rejection and resistance to external electromagnetic interference.

[0052] 4. Integrator performance is controlled over a wide bandwidth: The dual-path design of composite external integration + self-integration optimizes the low-frequency and high-frequency channels respectively, and avoids mutual damage and saturation through hardware protection strategies, reducing long-term drift and improving measurement stability.

[0053] 5. Intelligent identification and real-time switching output, reducing false alarm and missed alarm rates: FPGA-based parallel feature extraction and machine learning discrimination can identify event types and perform channel fusion and switching within milliseconds, significantly improving the reliability and practicality of the system under complex power grid conditions. Attached Figure Description

[0054] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0055] Figure 1 This is a schematic diagram of a coaxial dual-coil structure according to the present invention;

[0056] Figure 2 This is a general block diagram of a dual-channel broadband current measurement system according to the present invention;

[0057] Figure 3 This is a schematic diagram of the self-integrating circuit of the first Rogowski coil of the present invention;

[0058] Figure 4 This is a schematic diagram of the composite external integrating circuit of the second Rogowski coil of the present invention;

[0059] Figure 5 This is a flowchart of a dual-channel broadband current measurement method according to the present invention;

[0060] Figure 6 This is a detailed flowchart of the dual-channel broadband current measurement method of the present invention.

[0061] Figure reference numerals and corresponding component names:

[0062] 1-High voltage center conductor, 2-Shielding cover, 3-First Rogowski coil, 4-Composite shielding partition, 5-Second Rogowski coil. Detailed Implementation

[0063] In the following, the terms “comprising” or “may include” as used in various embodiments of the invention indicate the presence of an inventive function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of the invention, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0064] In various embodiments of the invention, the expression "or" or "at least one of A and / or B" includes any combination or all combinations of the words listed simultaneously. For example, the expression "A or B" or "at least one of A and / or B" may include A, may include B, or may include both A and B.

[0065] The expressions used in the various embodiments of the present invention (such as "first," "second," etc.) may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, a first user device and a second user device refer to different user devices, although both are user devices. For example, a first element may be referred to as a second element without departing from the scope of the various embodiments of the present invention, and similarly, a second element may also be referred to as a first element.

[0066] It should be noted that if a description is made of "connecting" one component to another, then the first component can be directly connected to the second component, and a third component can be "connected" between the first and second components. Conversely, when a component is "directly connected" to another component, it can be understood that there is no third component between the first and second components.

[0067] The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of the invention.

[0068] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0069] To address the shortcomings of existing technologies, this invention aims to solve the following technical problems:

[0070] (1) The measurement challenge of simultaneously meeting the accuracy of low frequency power frequency (e.g., power frequency 0.2 level) and waveform fidelity and amplitude accuracy (amplitude error ≤ ±10%, wavefront time difference ≤ ±15%) of MHz-level high frequency transient impact (e.g., 4 / 10μs lightning impact) in a single device.

[0071] (2) Provides a PCB-type Rogowski coil sensor head structure that is easy to mass-produce in engineering (good manufacturing consistency), has strong resistance to electromagnetic interference, and can be safely used in high-voltage electrical environments.

[0072] (3) Design an integration system that can achieve a trade-off between analog integration and digital processing, so that the system can maintain high precision at low frequencies, high fidelity at high frequencies and fast dynamic response, while suppressing integral drift and saturation.

[0073] (4) Realize an intelligent recognition system based on real-time feature extraction and machine learning to quickly and reliably determine events such as power frequency, harmonics, transients, and lightning, and automatically select and fuse the optimal channel output accordingly.

[0074] The key design features of this invention are: a coaxial dual-coil structure, dual-channel frequency division processing, and intelligent identification fusion. This invention has significant engineering application value in smart grids, relay protection, fault diagnosis, lightning measurement, and high-bandwidth current monitoring scenarios, and can fill the gaps in existing technologies regarding wide bandwidth, high precision, and engineering applicability.

[0075] Example 1

[0076] like Figure 1As shown, the present invention provides a coaxial dual-coil structure, comprising: two sets of PCB Rogowski coils coaxially arranged within the same mechanical housing, namely a first Rogowski coil 3 and a second Rogowski coil 5;

[0077] The first Rogowski coil 3 is a high-frequency measurement Rogowski coil used to detect lightning impulse signals;

[0078] The second Rogowski coil 5 is a power frequency measurement Rogowski coil used to detect power frequency signals;

[0079] The first Rogowski coil 3 adopts a self-integrating working mode to prioritize high-frequency response and fast rise time; the second Rogowski coil 5 adopts a composite integration working mode to prioritize low-frequency sensitivity and power frequency accuracy.

[0080] The first Rogowski coil 3 and the second Rogowski coil 5 share the same opening, which can be replaced on site and installed in an integrated manner; a high-voltage center conductor 1 runs through the opening to provide the measured current, and the two are separated by a middle composite shielding partition 4 and a preset axial distance to suppress electromagnetic coupling.

[0081] Among them, the first Rogowski coil 3 and the second Rogowski coil 5 are also provided with a shielding cover 2, and the first Rogowski coil 3 and the second Rogowski coil 5 are symmetrically arranged on both sides of the composite shielding partition 4.

[0082] In this embodiment, the first Rogowski coil 3 has a two-layer PCB structure, uses twisted wide-pitch wire with a wire width ranging from 0.2 to 0.3 mm and a number of turns ranging from 60 to 100.

[0083] The second Rogowski coil 5 has a four-layer PCB structure, uses twisted-pair differential winding with an outer grounding shield, and has a wire width ranging from 0.1 to 0.2 mm and a number of turns ranging from 200 to 300.

[0084] In this embodiment, the composite shielding partition 4 is a three-layer composite structure consisting of a high magnetic permeability material layer, a conductive material layer, and a supporting material layer; the high magnetic permeability material layer is made of permalloy or nanocrystalline alloy, the conductive material layer is made of oxygen-free copper foil, and the supporting material layer is made of polyimide or epoxy glass cloth.

[0085] In this embodiment, the preset axial spacing is three times the outer diameter of the first Rogowski coil 3 or the second Rogowski coil 5; or the preset axial spacing is 80~120mm.

[0086] In this embodiment, the ratio of the inner and outer radii of the second Rogowski coil 5 is 1.6 to 2.4, and the plate thickness of the second Rogowski coil 5 and the first Rogowski coil 3 is 1.4 to 1.8 mm; the parasitic capacitance of the first Rogowski coil 3 is ≤2 pF, and the self-resonant frequency is ≥5 MHz.

[0087] In specific implementation, the coaxial dual-coil structure of this invention adopts a coaxial symmetrical structure. The outer part is a cylindrical shield 2, and inside the shield 2, a first Rogowski coil 3, a composite shielding partition 4, and a second Rogowski coil 5 are sequentially arranged. The first Rogowski coil 3 is located on one side of the composite shielding partition 4 and is used to detect high-frequency transient components, such as lightning impulse signals. The first Rogowski coil 3 has relatively few turns, uses a double-layer PCB process, and is wound with twisted pairs, with a larger line width to reduce parasitic inductance. The second Rogowski coil 5 is located on the other side of the composite shielding partition 4, has more turns, uses a four-layer PCB process, and is double-layered wound to improve low-frequency response sensitivity. The composite shielding partition 4 is disposed between the two coils and consists of a three-layer composite structure composed of a high-permeability material layer, a conductive material layer, and a supporting material layer. In the three-layer composite structure, the high-permeability material layer is made of permalloy, the conductive material layer is made of oxygen-free copper foil, and the supporting material layer is made of polyimide. This composite shielding structure provides good shielding effectiveness, effectively suppressing electromagnetic coupling between the two coils and avoiding measurement errors caused by signal crosstalk. The entire structure ensures uniform mutual inductance of the coils through coaxial symmetrical arrangement, resulting in excellent linearity of the induced signals output by both sets of coils. The inner side of the shield 2 is made of copper metal with a reliable base, while the outer side is cast with epoxy resin to form an integrated protective shell with an IP65 protection rating, suitable for high humidity and high voltage environments.

[0088] The PCB routing strategy of this invention is as follows: the first Rogowski coil 3 adopts a simple two-layer twisted-pair routing to reduce parasitic capacitance; the second Rogowski coil 5 adopts a four-layer PCB with an invisible return / twisted-pair differential line structure and an outer ground shield. Symmetrical and differential routing is used in the design to reduce common-mode sensitivity and external field coupling.

[0089] The first Rogowski coil 3 is primarily used to detect lightning impulse currents and high-frequency transient signals. This coil employs a double-layer PCB layout, specifically with a line width of a = 0.25 mm and 80 turns. This minimizes distributed inductance and capacitance to improve the natural resonant frequency and high-frequency flatness. The end is loaded with a low-resistance (a few Ω to tens of Ω, using a non-inductive thin-film resistor) load to meet the self-integration condition, thereby achieving high-fidelity measurement of short pulses / fast rise edges. The first Rogowski coil 3 is internally filled with low-dielectric-constant epoxy resin to reduce dielectric polarization effects and improve high-frequency response speed. Its parasitic capacitance is less than 2 pF, and its self-resonant frequency is higher than 5 MHz. While its sensitivity is slightly lower than that of a power frequency coil, its response time is faster, accurately capturing the lightning wavefront within microseconds. Electromagnetic isolation from the inner coil via a composite shielding partition 4 significantly reduces mutual inductance interference, ensuring signal independence when both coils operate simultaneously.

[0090] The second Rogowski coil 5 is primarily designed for detecting low-frequency power frequency currents. It employs a four-layer PCB with interleaved wiring, where wiring is evenly distributed across each layer, and closed loops are formed between layers via soldering. Specifically, the line width a = 0.15mm, and the number of turns is 250 (adjustable according to range / sensitivity); the board thickness is a standard 1.6mm to balance processing and reliability; the outer / inner diameter is optimized based on the transformer cavity and installation space (inner diameter d = 150mm, outer diameter D = 280mm, with an optimized inner / outer radius ratio ranging from 1.6 to 2.4). These selections ensure mutual inductance and sensitivity while achieving high anti-interference and good low-frequency response through inner-layer differential twisted-pair wiring and outer-layer shielding. To reduce electromagnetic inhomogeneity, the wiring start and end points are symmetrically arranged, and impedance matching resistors are added at the connections. Tests show that this structure exhibits good linear output in the 50 Hz to 10 kHz range, with a sensitivity error of less than ±0.2%. The Rogowski coil 5 for power frequency measurement is connected to the composite external integrating circuit via a coaxial cable to achieve accurate integration and recovery of the measured current change.

[0091] Example 2

[0092] like Figure 2 As shown, the difference between this embodiment and Embodiment 1 is that this embodiment provides a dual-channel broadband current measurement system, mainly including a first Rogowski coil 3 arranged coaxially, a composite shielding plate 4, a second Rogowski coil 5, a shielding cover 2, a composite external integrating circuit, an FPGA intelligent signal processing module, and protection and communication units, etc. The entire measurement system is compact in structure and complementary in function, and can achieve high-precision detection of current signals from power frequency to MHz level.

[0093] Specifically, the measurement system includes:

[0094] High-voltage center conductor 1 is used to provide the measured current and generate a changing magnetic field around it;

[0095] The coaxial dual-coil structure, using one of the coaxial dual-coil structures described above, is used to output a voltage signal proportional to the rate of change of the measured current after sensing a change in magnetic flux. The first Rogowski coil 3 outputs a first voltage signal, and the second Rogowski coil 5 outputs a second voltage signal.

[0096] The first integrator is a self-generating integrator, which is connected to the first Rogowski coil 3; the second integrator is a composite external integrator, which is connected to the second Rogowski coil 5.

[0097] The first ADC converter, as a lightning channel ADC, is connected to the first integrator and outputs a first current digital signal; the second ADC converter, as a power frequency channel ADC, is connected to the second integrator and outputs a second current digital signal; and the first ADC converter and the second ADC converter have hardware timestamp synchronization function.

[0098] The FPGA intelligent signal processing module is used to extract features from the first and second current digital signals to obtain multi-dimensional features; based on the multi-dimensional features, it uses a machine learning model and a dual-threshold strategy to identify the signal type and obtain the signal identification result; based on the signal identification result, it automatically adjusts the weights of each channel; and based on the signal identification result and the corresponding channel weights, it fuses the results and outputs them.

[0099] The working principle of this invention is as follows: When the measured current flows in the high-voltage center conductor 1, a changing magnetic field is generated around it. Two sets of Rogowski coils (first Rogowski coil 3 and second Rogowski coil 5) induce the change in magnetic flux and output a voltage signal proportional to the rate of change of the measured current. The two sets of Rogowski coils are used for detecting lightning impulse signals and power frequency signals, respectively. After processing by independent integrator circuits, the signals are input to the FPGA intelligent signal processing module for intelligent fusion and output, thereby obtaining a precise current waveform across the entire frequency band.

[0100] In this embodiment, the two Rogowski coils are respectively configured with an integrator and an ADC converter; the second Rogowski coil 5 is connected to a composite external integrator, which is a cascaded structure of passive integrator, active integrator and high-frequency filter, and the active integrator branch includes a feedback discharge resistor; the first Rogowski coil 3 is configured with a self-integrating impedance; the two circuits are respectively paired with independent ADC converters, and the dual ADC converters have hardware timestamp synchronization function.

[0101] The above Rogowski coils are configured with integrators and ADC converters respectively, ensuring that the two channels are optimized independently in their respective best operating modes without sacrificing the performance of either channel.

[0102] Specifically, the dual ADC sampling strategy is as follows: the power frequency channel uses a high-resolution ADC (e.g., 24-bit level, sampling rate of tens to hundreds of kS / s) to ensure the amplitude and phase accuracy of power frequency and harmonic measurements; the lightning channel uses a high-speed ADC (e.g., hundreds of MS / s, 16-bit or 14-bit) to capture high-frequency details of lightning impacts and rapid transients.

[0103] Both channels should have hardware timestamps and precise synchronization (FPGA pin-level triggering and timestamp counter) to ensure microsecond or even nanosecond-level time alignment, facilitating subsequent fusion.

[0104] In this embodiment, the self-integrating impedance of the first Rogowski coil 3 is a non-inductive thin-film resistor of 5~50Ω; in the composite external integrator of the second Rogowski coil 5, the passive integration time constant is 1~10μs, the active integration feedback resistor is 100M~1GΩ, and the operational amplifier is a low bias current JFET / CMOS type operational amplifier.

[0105] In this embodiment, the power frequency channel ADC is 24-bit with a sampling rate of 50~500kS / s; the lightning channel ADC is 14~16-bit with a sampling rate of 200~500MS / s; and the synchronization error of the dual ADC converter is ≤10ns.

[0106] In this embodiment, the multidimensional features include time-domain features, frequency-domain features, and statistical features;

[0107] Time-domain characteristics include rise time, peak value, current pulse width, RMS value, and waveform symmetry; frequency-domain characteristics include FFT spectrum distribution, harmonic content, and energy concentration; statistical characteristics include waveform factor, zero-crossing rate, and root mean square deviation.

[0108] In this embodiment, the machine learning model is a lightweight CNN, SVM, or decision tree ensemble model, etc.; the dual-threshold strategy includes a primary amplitude threshold (≥10kA to trigger lightning channel determination) and a secondary spectral centroid threshold (≥100kHz to confirm transient events); the phase error of data fusion is ≤0.1μs, and the weight adjustment response time is ≤10μs.

[0109] The coaxial dual-coil structure, composite shielding partition, FPGA intelligent signal processing module, etc., all adopt a modular design and can be replaced independently.

[0110] Figure 3 This is a schematic diagram of the first Rogowski coil self-integrating circuit of the present invention. Figure 4 This is a schematic diagram of the composite external integrating circuit of the second Rogowski coil of the present invention.

[0111] like Figure 3 As shown, the voltage signal output from the first Rogowski coil 3 is directly output to the subsequent lightning channel ADC via self-integration. The self-integrating circuit consists of distributed capacitance, self-inductance, internal resistance, and sampling resistor, and is suitable for processing high-frequency transient signals from 100 kHz to 1 MHz. The integration channel outputs an analog signal to the synchronous sampling module, which achieves 16-bit precision sampling through a high-speed analog-to-digital converter, with a sampling rate of 20 MS / s, ensuring signal integrity at high frequencies.

[0112] like Figure 4 As shown, the horizon signal output from the second Rogowski coil 5 is processed by a composite external integrator circuit. The composite external integrator circuit is a passive... Intermediate frequency external integrator, active It consists of a low-frequency integrator and a high-frequency filter. The passive component... In the points-based process In the active integration stage , For the feedback resistor, take It can effectively reduce DC gain, decrease output offset, effectively suppress integral drift, and prevent integral output saturation. The operational amplifier in the active integrator is the single-channel low-noise THS4031CD; in the high-pass filter stage... The composite external integrator circuit can achieve the function of extending the frequency band by coordinating the amplitude-frequency characteristics of the high-frequency self-integrator of the Rogowski coil body with the external active integrator, external passive integrator, external high-pass filter, and the high-frequency self-integrator of the Rogowski coil itself.

[0113] The system of this invention is not only applicable to power frequency current monitoring of high-voltage transmission lines, but also to lightning impulse current measurement and partial discharge detection, and has high practical value and engineering application prospects.

[0114] Example 3

[0115] like Figure 5 As shown, the difference between this embodiment and Embodiment 2 is that this embodiment provides a dual-channel broadband current measurement method, which is based on a dual-channel broadband current measurement system of Embodiment 2 for measurement; the method includes:

[0116] The power frequency signal and / or lightning impulse signal of the measured current are obtained through a coaxial dual-coil structure.

[0117] Based on the power frequency signal and / or lightning impulse signal, the first current digital signal and the second current digital signal are obtained through the corresponding dual-channel integrator and ADC converter;

[0118] Feature extraction is performed on the first current digital signal and the second current digital signal respectively to obtain multidimensional features;

[0119] Based on multidimensional features, a machine learning model and a dual-threshold strategy are used to identify signal types and obtain signal identification results.

[0120] Based on the signal recognition results, the weights of each channel are automatically adjusted; and based on the signal recognition results and corresponding channel weights, an adaptive weighted fusion is performed to obtain the fusion result; and

[0121] Based on channel weights and signal types, different output modes are automatically selected for output.

[0122] As a further implementation, this invention performs timing correction on the first and second current digital signals obtained after sampling by dual-channel integration and ADC converter to ensure consistency of subsequent fusion timing. The synchronized data undergoes multi-stage digital filtering, including low-pass, band-pass, and adaptive notch filtering, which effectively suppresses noise and power frequency electric field interference while preserving the main time-domain characteristics of the signal. After filtering, feature extraction is performed to extract multi-dimensional features.

[0123] Specifically, the multidimensional features include time-domain features, frequency-domain features, and statistical features; time-domain features include rise time, peak value, current pulse width, RMS value, and waveform symmetry; frequency-domain features include FFT spectrum distribution, harmonic content, and energy concentration; and statistical features include waveform factor, zero-crossing rate, and root mean square deviation.

[0124] Specifically, the machine learning model consists of a finite state machine and a small-scale neural network. It automatically determines the signal type based on the extracted multidimensional features and can identify typical waveforms such as power frequency signals, harmonic components, lightning impulses, switching operation transients, and short-circuit faults.

[0125] Furthermore, to adapt to dynamic changes under different operating conditions, this invention designs a dual-threshold triggering strategy. This strategy can determine the event level based on the combined rate of change of signal amplitude and frequency, thereby distinguishing between high-energy lightning strikes and ordinary current disturbances.

[0126] Specifically, based on the signal recognition results, the weights of each channel are automatically adjusted, including:

[0127] If the signal identification result is a power frequency signal, then increase the weight of the power frequency channel to make the active integration result the dominant output.

[0128] If the signal identification result is a lightning impulse signal, the weight of the lightning channel is increased to enhance the high-frequency response;

[0129] If the signal identification result indicates that both the power frequency signal and the lightning impulse signal occur simultaneously, then the two channels maintain their initial weights and output both the power frequency signal and the lightning impulse signal.

[0130] In addition, the channel weight adjustment logic of this invention is implemented with a hardware state machine, with a response time of less than 10 µs, which can complete the channel switching in real time when the signal changes abruptly.

[0131] Specifically, adaptive weighted fusion includes:

[0132] Timestamp alignment: The FPGA's internal clock is used to precisely synchronize the dual-channel data, ensuring that the phase error between the two signals is less than 0.1 µs when they are fused.

[0133] The weights are dynamically calculated, and the fusion coefficients are updated in real time based on the classification results of the previous stage and the current spectral energy distribution.

[0134] Channel data fusion outputs a continuous current waveform by combining weighted averaging and time-domain reconstruction, ensuring that the signal amplitude-frequency characteristics remain consistent across the entire frequency band. The specific fusion process is implemented using a fixed-point DSP algorithm, with a calculation delay of no more than 20 sampling cycles.

[0135] Specifically, the fusion result can automatically select the output mode based on channel weights and signal types. When in power frequency measurement mode, the system outputs a smooth and stable power frequency current waveform, while simultaneously sending harmonic components as additional information to the host computer. When lightning strikes or transient waveforms are detected, the system switches to high-speed output mode, directly outputting the lightning channel waveform and activating the protection circuit trigger signal to prevent overvoltage damage to downstream equipment. The FPGA packages and sends the output data via an Ethernet interface, including current waveform data, signal type tags, characteristic parameters, and event timestamps.

[0136] This invention combines a coaxial dual-coil structure, dual-channel frequency division processing, and intelligent recognition fusion to achieve simultaneous measurement of low-frequency power frequency signals and high-frequency transient impact signals, unifying high precision at low frequencies with rapid response at high frequencies. Compared with traditional single-coil Rogowski sensors, this invention significantly improves bandwidth, linearity, and anti-interference capabilities. Its coaxial dual-coil design effectively reduces errors caused by magnetic field inhomogeneity, the composite integral structure expands the system response range, and the FPGA intelligent processing module fully automates signal discrimination and channel switching, ensuring continuous and stable measurement of wideband current signals.

[0137] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coaxial double coil structure, characterized by, The application relates to a lightning impulse current measurement system. The application comprises: The first Rogowski coil (3) is a high-frequency measurement Rogowski coil, which is used for detecting lightning impulse signals; The second Rogowski coil (5) is a power-frequency measurement Rogowski coil, which is used for detecting power-frequency signals; The first Rogowski coil (3) adopts a self-integration working mode, and the second Rogowski coil (5) adopts a composite integration working mode; the first Rogowski coil (3) and the second Rogowski coil (5) share the same opening, a high-voltage center conductor (1) penetrates through the opening to provide a measured current, and the two coils are separated by an intermediate composite shielding partition (4) with a preset axial spacing to inhibit electromagnetic coupling.

2. A coaxial double coil structure according to claim 1, characterized in that The first Rogowski coil (3) is a two-layer PCB structure, adopts double-twisted wide-line-spacing winding, the line width ranges from 0.2 mm to 0.3 mm, and the number of turns ranges from 60 to 100 turns; The second Rogowski coil (5) is a four-layer PCB structure, adopts double-twisted differential winding and is provided with an outer layer of grounding shielding, the line width ranges from 0.1 mm to 0.2 mm, and the number of turns ranges from 200 to 300 turns.

3. A coaxial double coil structure according to claim 1, characterized in that The composite shielding partition (4) is a three-layer composite structure composed of a high-magnetic-permeability material layer, a conductive material layer and a supporting material layer; The high-magnetic-permeability material layer adopts permalloy or nanocrystalline alloy, the conductive material layer adopts oxygen-free copper foil, and the supporting material layer adopts polyimide or epoxy glass cloth.

4. A coaxial double coil structure according to claim 1, characterized in that The preset axial spacing is 3 times the outer diameter of the first Rogowski coil (3) or the second Rogowski coil (5).

5. A coaxial double coil structure according to claim 1, characterized in that The preset axial spacing is 80-120 mm.

6. A dual channel broadband current measurement system, characterized by, The measurement system comprises: A high-voltage center conductor (1) is used for providing a measured current and generating a changing magnetic field around the high-voltage center conductor (1); A coaxial double-coil structure adopts any one of the coaxial double-coil structures as claimed in claims 1 to 5, and is used for inducting a magnetic flux change to output a voltage signal proportional to the change rate of the measured current, wherein the first Rogowski coil (3) outputs a first voltage signal, and the second Rogowski coil (5) outputs a second voltage signal; A first integrator adopts a passive self-integrator and is connected to the first Rogowski coil (3); a second integrator adopts a composite external integrator and is connected to the second Rogowski coil (5); A first ADC converter is used as a lightning channel ADC, is connected to the first integrator and outputs a first current digital signal; a second ADC converter is used as a power-frequency channel ADC, is connected to the second integrator and outputs a second current digital signal; and the first ADC converter and the second ADC converter have a hardware time stamp synchronization function; An FPGA intelligent signal processing module is used for extracting features from the first current digital signal and the second current digital signal respectively to obtain multi-dimensional features; performing signal type identification by using a machine learning model and a double-threshold strategy according to the multi-dimensional features to obtain a signal identification result; automatically adjusting the weights of the channels according to the signal identification result; and performing result fusion and outputting according to the signal identification result and the corresponding channel weights.

7. A dual-channel broadband current measurement system according to claim 6, wherein, The composite external integrator is a cascaded structure of passive integration, active integration and high-frequency filtering, and the active integration branch contains a feedback bleeder resistor.

8. The dual-channel broadband current measurement system of claim 6, wherein, The multi-dimensional features include time domain features, frequency domain features and statistical features. The time domain features include rise time, peak value, current pulse width, effective value and waveform symmetry; the frequency domain features include FFT frequency spectrum distribution, harmonic content and energy concentration; and the statistical features include waveform factor, zero-crossing rate and root mean square deviation.

9. A dual-channel broadband current measurement method, characterized by, The method comprises: obtaining a power frequency signal and / or a lightning impulse signal of the measured current through a coaxial double coil structure; obtaining a first current digital signal and a second current digital signal through a corresponding double-channel integration and an ADC converter according to the power frequency signal and / or the lightning impulse signal; extracting features from the first current digital signal and the second current digital signal respectively to obtain multi-dimensional features; adopting a machine learning model and a double-threshold strategy to identify the signal type according to the multi-dimensional features to obtain a signal identification result; automatically adjusting the channel weights according to the signal identification result; obtaining a fusion result through adaptive weighted fusion according to the signal identification result and the corresponding channel weights; and automatically selecting different output modes for output according to the channel weights and the signal type.

10. The dual-channel broadband current measurement method of claim 9, wherein, The automatic adjustment of the channel weights according to the signal identification result comprises: if the signal identification result is a power frequency signal, increasing the power frequency channel weight to make the active integration result the dominant output; if the signal identification result is a lightning impulse signal, increasing the lightning channel weight to enhance the high-frequency response; if the signal identification result is both a power frequency signal and a lightning impulse signal, maintaining the initial weights of the power frequency channel and the lightning channel, and simultaneously outputting the power frequency signal and the lightning impulse signal.

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