Anti-interference pulse coupling injection device

Abstract

The invention discloses an anti-interference pulse coupling injection device. The problem that winding deformation is not found in time and accidents are prone to being caused is solved. The invention relates to a high-voltage direct-current charging power supply, which consists of a pulse generation module, a coupling sensing module, a signal injection protection module, a signal acquisition module, a signal processing module and an FPGA (Field Programmable Gate Array) controller, and is characterized in that the pulse generation module adopts a multi-stage Marx circuit structure formed by connecting full-bridge switch capacitor units in series and is connected with the high-voltage direct-current charging power supply; and under the control of the FPGA controller, positive-polarity, negative-polarity or positive-negative alternating bipolar pulse signals can be output. The signal is transmitted to the coupling sensing module through the signal injection protection module, and the coupling sensing module is attached to the outer insulation surface of the transformer high-voltage bushing. The signal acquisition module synchronously acquires excitation voltage signals and transformer winding response signals, and the signal processing module receives the acquired signals and generates a frequency response curve so as to provide a direct basis for winding deformation state diagnosis and improve the reliability of fault identification.

Description

Technical Field

[0001] This application relates to the field of power grids, and in particular to an anti-interference pulse coupling injection device. Background Technology

[0002] As a core component of the power grid, the mechanical integrity of the power transformer windings directly determines the safe and stable operation of the grid. Windings are prone to deformation after being subjected to massive electrodynamic impacts such as short-circuit currents. These defects have a cumulative effect; if not detected in time, they can lead to insulation damage or even transformer burnout. Frequency response analysis (FRA) has been proven to be an effective method for detecting winding deformation, but traditional FRA requires offline testing with the transformer shut down, which cannot meet the real-time assessment needs of smart grids for critical equipment.

[0003] The frequency response method based on pulse coupling injection injects a wideband pulse signal into the transformer bushing, detects the response signal after propagation through the winding, and obtains the frequency response characteristics through signal processing, making it possible to monitor winding deformation online. Existing pulse sources mostly output fixed-parameter pulses of a single polarity (e.g., negative polarity), making it difficult to adapt to different transformer structures and on-site electromagnetic environments. During online monitoring, the pulse signal attenuates severely as it couples to the high-voltage conductor through the capacitive sensor, resulting in a response signal amplitude of only millivolts. This makes it highly susceptible to strong electromagnetic interference such as corona discharge, switching surges, fast transient pulse groups, and damped oscillating waves within the substation, leading to an extremely low signal-to-noise ratio.

[0004] Therefore, providing a diagnostic solution that can systematically optimize the signal chain from source to end, and which combines high signal-to-noise ratio, strong anti-interference capability, and high security, is a technical problem that urgently needs to be solved by those in the field. Summary of the Invention

[0005] The purpose of this application is to provide an anti-interference pulse coupling injection device to solve the problem that failure to detect winding deformation in a timely manner can easily lead to accidents.

[0006] To address the aforementioned technical problems, this application provides an anti-interference pulse coupling injection device, comprising: a pulse generation module, a coupling sensing module, a signal injection protection module, a signal acquisition module, a signal processing module, and an FPGA controller; the FPGA controller is connected to the pulse generation module, the signal injection protection module, the signal acquisition module, and the signal processing module respectively.

[0007] The pulse generation module is a multi-stage Marx circuit structure based on a series connection of full-bridge switched capacitor units. The FPGA controller controls the pulse generation module to output positive, negative, or alternating positive and negative bipolar pulse signals. The input terminal of the pulse generation module is connected to a high-voltage DC charging power supply, and the output terminal of the pulse generation module is connected to the input terminal of the signal injection protection module.

[0008] The signal injection protection module is used to filter out common-mode interference at a specific frequency, inject pulse signals forward, provide high-voltage isolation protection, and cut off abnormal overvoltage. The output terminal of the signal injection protection module is connected to the input terminal of the coupling sensing module.

[0009] The coupling sensing module is a capacitive coupling sensor, which is used to be sleeved on the high-voltage bushing of the transformer and to be in contact with the outer insulating surface of the high-voltage bushing of the transformer.

[0010] The signal acquisition module is used to synchronously acquire the excitation voltage signal output by the pulse generation module and the response signal of the transformer winding; the signal input terminal of the signal acquisition module is connected to the pulse generation module and the transformer neutral point grounding wire respectively, and the signal output terminal of the signal acquisition module is connected to the input terminal of the signal processing module.

[0011] The signal processing module is used to process the signals transmitted by the signal acquisition module and generate frequency response curves.

[0012] Optionally, in the above-mentioned anti-interference pulse coupling injection device, each stage of the full-bridge switched capacitor unit of the pulse generation module includes: an energy storage capacitor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a branch switch, and a diode;

[0013] The negative terminal of the diode is connected to the first terminal of the branch switch; the second terminal of the branch switch is connected to the first terminal of the first switching transistor, the first terminal of the energy storage capacitor, and the first terminal of the third switching transistor; the second terminal of the first switching transistor is connected to the first terminal of the second switching transistor; the second terminal of the second switching transistor is connected to the second terminal of the energy storage capacitor and the second terminal of the fourth switching transistor; the second terminal of the third switching transistor is connected to the first terminal of the fourth switching transistor; the positive terminal of the diode serves as the first input terminal of the full-bridge switched capacitor unit; the second terminal of the first switching transistor serves as the second input terminal of the full-bridge switched capacitor unit; the first terminal of the third switching transistor serves as the first output terminal of the full-bridge switched capacitor unit; and the second terminal of the third switching transistor serves as the second output terminal of the full-bridge switched capacitor unit.

[0014] The control terminals of the first switch, the second switch, the third switch, the fourth switch, and the branch switch are connected to the FPGA controller.

[0015] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the coupling sensing module is made of a stainless steel metal ring, the width of the metal strip is positively correlated with the signal coupling ratio, and the width of the metal strip is adjustable.

[0016] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the signal injection protection module is a passive double-T notch filter network, which consists of two T-type RC networks.

[0017] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the signal injection protection module further includes: a voltage monitoring unit and a fast-acting mechanical isolation switch;

[0018] The voltage monitoring unit monitors the induced voltage returned by the coupling sensing module in real time. When the voltage exceeds a preset threshold, it triggers the mechanical isolation switch to cut off the pulse injection circuit.

[0019] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the signal acquisition module includes: a current measuring device; the signal processing module includes: a data acquisition card;

[0020] The current measuring device is clamped to the neutral point grounding wire of the transformer and is used to measure the response current signal;

[0021] The data acquisition card is connected to the pulse generation module and the current sensor, and is used to synchronously acquire the excitation voltage signal output by the pulse generation module and the response current signal sensed by the current measuring device.

[0022] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the signal acquisition module includes: a voltage measurement device;

[0023] The voltage measuring device is clamped to the neutral point of the transformer and is used to measure the response voltage signal;

[0024] The data acquisition card is connected to the voltage measuring device and receives the response voltage signal sensed by the voltage measuring device.

[0025] Optionally, the above-mentioned anti-interference pulse coupling injection device further includes: multiple metal shielding shells;

[0026] The pulse generation module, the FPGA controller, and the signal acquisition module are each equipped with a fully enclosed and grounded metal shielding shell.

[0027] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the full-bridge switched capacitor units of each stage of the pulse generation module are arranged in a centrally symmetrical manner, and the corresponding control terminals are arranged in a preset order at the signal transmission terminal of the FPGA controller.

[0028] Optionally, in the above-mentioned anti-interference pulse coupling injection device, the signal injection protection module and the pulse generation module are connected by a coaxial cable, and the signal injection protection module and the coupling sensing module are connected by a high-voltage shielded wire.

[0029] The anti-interference pulse coupling injection device provided in this application comprises a pulse generation module, a coupling sensing module, a signal injection protection module, a signal acquisition module, a signal processing module, and an FPGA controller, forming a complete system. The FPGA controller serves as the core control unit, regulating each module. The pulse generation module employs a multi-stage Marx circuit structure with series-connected full-bridge switched capacitor units, connected to a high-voltage DC charging power supply. Under the control of the FPGA controller, it can output positive, negative, or alternating positive and negative bipolar pulse signals, adjusting the pulse parameters. The signal injection protection module processes the pulse signal in the signal transmission path. The coupling sensing module improves coupling efficiency through its installation method of being attached to the outer insulation surface of the transformer's high-voltage bushing. The acquisition end of the signal acquisition module is connected to both the pulse generation module and the transformer neutral point grounding wire, synchronously acquiring the excitation voltage signal and the transformer winding response signal to ensure the integrity and synchronization of signal acquisition. The signal processing module receives the acquired signals and generates a frequency response curve, providing direct evidence for diagnosing winding deformation conditions and improving the reliability of fault identification. Attached Figure Description

[0030] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A schematic diagram of an anti-interference pulse coupling injection device provided in this application;

[0032] Figure 2.1 A circuit diagram of a pulse generation module provided in this application;

[0033] Figure 2.2 A schematic diagram of the charging stage circuit of a pulse generation module provided in this application;

[0034] Figure 2.3 A schematic diagram of the positive discharge stage circuit of a pulse generation module provided in this application;

[0035] Figure 2.4 A schematic diagram of the positive and negative polarity discharge interval stage of a pulse generation module provided in this application;

[0036] Figure 2.5 A circuit schematic diagram of the negative polarity discharge stage of a pulse generation module provided in this application;

[0037] Figure 3.1 A 2D simulation model diagram of a transformer on the excitation injection side is provided in this application;

[0038] Figure 3.2 This application provides a 2D simulation model diagram of a transformer with a primary winding.

[0039] Figure 3.3 A waveform diagram of the winding withstand voltage under 1kV excitation coupling injection is provided in this application;

[0040] Figure 3.4 A control signal waveform diagram provided in this application;

[0041] Figure 4.1 This application provides an excitation waveform diagram under different excitation amplitudes;

[0042] Figure 4.2 This application provides a response waveform diagram under different excitation amplitudes;

[0043] Figure 4.3 This application provides an offline experimental wiring diagram;

[0044] Figure 4.4 A wiring diagram for an online experiment provided in this application;

[0045] Figure 4.5 This application provides an offline AO ​​neutral point current measurement curve.

[0046] Figure 4.6 This application provides an offline AO ​​coupling voltage measurement curve.

[0047] Figure 4.7 A comparison chart of neutral point current measurement and coupling voltage measurement curves provided in this application;

[0048] Figure 4.8 A curve comparison diagram of a three-phase coupled voltage measurement method provided in this application;

[0049] Figure 4.9 A curve comparison diagram of a three-phase neutral point current measurement method provided in this application;

[0050] Figure 4.10 This application provides a voltage sensor feedback voltage test waveform diagram;

[0051] Figure 4.11 A waveform diagram for testing the voltage of a mechanical switch provided in this application;

[0052] Figure 4.12 This application provides a comparison diagram of coupling voltage measurement waveforms under offline conditions with and without connection to a high-voltage three-phase line;

[0053] Figure 4.13 This application provides an AO coupling voltage measurement curve.

[0054] Figure 4.14 This application provides an AO neutral point current measurement curve.

[0055] Figure 4.15 A comparison chart of three-phase neutral point current measurement curves under the same percentage load provided in this application;

[0056] Figure 5.1 A schematic diagram of a notch filter provided in this application;

[0057] Figure 5.2 A notch filter simulation circuit diagram is provided for this application;

[0058] Figure 5.3 A notch filter amplitude-frequency response diagram is provided in this application;

[0059] Figure 5.4 A notch filter phase frequency characteristic diagram provided in this application;

[0060] Figure 5.5 A wiring diagram of a pulse coupling injection method provided in this application. Detailed Implementation

[0061] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0062] The core of this application is to provide an anti-interference pulse coupling injection device.

[0063] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] As a core component of the power grid, the mechanical integrity of the power transformer windings is crucial for ensuring the safe and stable operation of the grid. Windings are prone to deformation after being subjected to massive electrodynamic impacts such as short-circuit currents. These defects have a cumulative effect; if not detected in time, they can lead to insulation damage or even transformer burnout. Frequency response analysis (FRA) has proven to be an effective method for detecting winding deformation. However, traditional frequency sweep FRA methods require offline testing with the transformer shut down, which cannot meet the needs of smart grids for real-time status assessment of critical equipment.

[0065] The frequency response method based on pulse coupling injection injects a broadband pulse signal into the transformer bushing and detects the response signal after propagation through the winding. Signal processing is then used to obtain the transformer's frequency response characteristics, providing a possibility for online monitoring of winding deformation. However, this method faces significant challenges in practical engineering applications:

[0066] Insufficient adaptability of excitation signals: Existing pulse sources mostly output fixed parameter pulses of a single polarity (such as negative polarity), lacking adaptability to different transformer structures and different field electromagnetic environments. The influence of pulses of different polarities and parameters on the frequency response curve is unclear, and it is impossible to actively avoid the "pseudo-resonance" phenomenon in the frequency response curve caused by improper pulse parameters (such as excessively wide pulse width), affecting the accuracy of diagnosis.

[0067] The signal coupling and transmission links are fragile: During online monitoring, the pulse signal is coupled to the high-voltage conductor through the capacitive sensor, resulting in severe signal attenuation. The response signal amplitude is very small (usually in the millivolt range), making it extremely susceptible to being overwhelmed by strong electromagnetic interference within the substation (such as corona discharge, surges caused by switching operations, fast transient pulse groups, damped oscillation waves, etc.), leading to an extremely low signal-to-noise ratio.

[0068] Lack of system-level anti-interference design: Existing research focuses on improving signal processing algorithms, while neglecting end-to-end noise suppression from signal generation, injection, transmission to acquisition. Single noise reduction methods are insufficient to cope with the complex interference spectrum in the field, resulting in poor system robustness.

[0069] This application provides an anti-interference pulse coupling injection device, such as... Figure 1 As shown, it includes: a pulse generation module 11, a coupling sensing module 13, a signal injection protection module 12, a signal acquisition module 14, a signal processing module 15, and an FPGA controller 16; the FPGA controller 16 is connected to the pulse generation module 11, the signal injection protection module 12, the signal acquisition module 14, and the signal processing module 15 respectively.

[0070] The pulse generation module 11 is a multi-stage Marx circuit structure based on the series connection of full-bridge switched capacitor units. The FPGA controller 16 controls the pulse generation module 11 to output positive, negative or alternating positive and negative bipolar pulse signals. The input terminal of the pulse generation module 11 is connected to the high-voltage DC charging power supply, and the output terminal of the pulse generation module 11 is connected to the input terminal of the signal injection protection module 12.

[0071] The signal injection protection module 12 is used to filter out common-mode interference at a specific frequency, positive injection of pulse signals, high-voltage isolation protection, and abnormal overvoltage cutoff. The output terminal of the signal injection protection module 12 is connected to the input terminal of the coupling sensing module 13.

[0072] The coupling sensing module 13 is a capacitive coupling sensor, which is used to be sleeved on the high-voltage bushing of the transformer and is in contact with the outer insulating surface of the high-voltage bushing of the transformer.

[0073] The signal acquisition module 14 is used to synchronously acquire the excitation voltage signal output by the pulse generation module 11 and the response signal of the transformer winding; the signal input terminal of the signal acquisition module 14 is connected to the pulse generation module 11 and the transformer neutral point grounding wire respectively, and the signal output terminal of the signal acquisition module 14 is connected to the input terminal of the signal processing module 15.

[0074] The signal processing module 15 is used to process the signals transmitted by the signal acquisition module 14 and generate frequency response curves.

[0075] First, the FPGA controller 16 is connected to the pulse generation module 11, signal injection protection module 12, signal acquisition module 14, and signal processing module 15, respectively. Its core function is to achieve timing synchronization and precise parameter control of each module. Through programming logic, the multiple modules work collaboratively. For example, while the pulse generation module 11 outputs an excitation signal, the signal acquisition module 14 is simultaneously triggered to start acquisition, ensuring that the excitation and response signals are aligned in time and avoiding signal processing errors caused by timing deviations. On the other hand, the field-programmable gate array (FPGA) needs to respond quickly to parameter modification commands through a preset program, achieving millisecond-level adjustments to parameters such as pulse polarity, amplitude, and pulse width.

[0076] The pulse generation module 11 adopts a multi-stage Marx generator circuit structure based on a series connection of full-bridge switched capacitor units. The multi-stage Marx circuit, through the principle of parallel charging and series discharging, can flexibly output positive, negative, or alternating positive and negative bipolar pulse signals under the control of the FPGA controller 16. It should be noted that the full-bridge switched capacitor unit is the key component for achieving multipolar output. Each unit contains multiple switching devices and energy storage capacitors. By controlling the on / off sequence of the switching devices, the series connection direction of the capacitors can be changed, thereby achieving the output of pulses of different polarities. For example, when the switching devices are forward-biased, the capacitors are connected in series in the forward direction, outputting a positive pulse; when reverse-biased, the capacitors are connected in series in the reverse direction, outputting a negative pulse; alternating control achieves bipolar pulse output. Furthermore, the input terminal of the pulse generation module 11 is connected to a high-voltage DC charging power supply. The purpose of this design is to change the pulse amplitude by adjusting the DC charging voltage, rather than fixing the output voltage level. For example, a lower charging voltage can be set for a 10kV transformer, and a higher charging voltage can be set for a 220kV transformer, adapting to the excitation requirements of equipment with different voltage levels. It should also be noted that "multi-stage" does not mean that the number of stages is fixed. This embodiment does not impose strict limitations. Generally, a 7-stage structure can be used to achieve a maximum peak pulse output of 7kV. The number of stages can also be adjusted according to actual needs, taking into account both excitation intensity and equipment insulation safety.

[0077] The signal injection protection module 12 performs four main functions: filtering out common-mode interference at specific frequencies, forward injection of pulse signals, high-voltage isolation protection, and abnormal overvoltage cutoff. Its core function is to ensure effective signal transmission and system safety in complex electromagnetic environments. First, filtering out common-mode interference at specific frequencies targets damped oscillation waves and corona discharge interference commonly found in substations, such as those in the 100kHz~1MHz range. By integrating filtering units (such as a passive dual-T notch filter network), it can specifically filter out narrowband interference.

[0078] On the other hand, high-voltage isolation protection is necessary because the high-voltage bushings of the transformer are at voltage levels of several kilovolts or even higher. If a high-voltage reverse input pulse generator module 11 is used, it could lead to equipment damage or even personnel safety accidents. Therefore, this module uses a high-voltage isolation circuit to block reverse high-voltage transmission, ensuring the safety of the low-voltage side module. Abnormal overvoltage cutoff is achieved by real-time monitoring of the induced voltage returned by the coupling sensor module 13. When the voltage exceeds a preset threshold, a switch is immediately triggered to cut off the injection circuit, preventing sudden overvoltage from impacting the equipment. It should be noted that the "forward injection" function of this module requires the signal injection and protection circuit to be fully conductive from the pulse generator circuit to the bushing capacitance coupling sensor in the forward direction. Furthermore, filtering and protection must be implemented in the reverse circuit in the opposite direction. This is achieved by designing a filter to simultaneously ensure the full conduction of the forward circuit and the filtering of the power frequency signal in the reverse circuit.

[0079] The coupling sensing module 13 is specifically a capacitive coupling sensor, which is used to be sleeved on the high-voltage bushing of the transformer and attached to the outer insulation surface, thus solving the problems of low coupling efficiency and severe signal attenuation of traditional sensors.

[0080] First, the principle of capacitive coupling is to use the parasitic capacitance between the sensor and the high-voltage conductor of the transformer to couple the pulse signal to the winding. The close-fitting installation can reduce energy loss during the signal coupling process. Compared with traditional non-contact sensors, the close-fitting design can significantly improve the coupling ratio.

[0081] It should be noted that mounting the sensor on the high-voltage bushing of the transformer does not mean the sensor size is fixed. Instead, it must be adapted to the bushing size. For example, a 7cm wide copper strip sensor can be used for a 220kV transformer bushing. The width of the metal strip is positively correlated with the coupling ratio, and the size can be adjusted to adapt to bushings of different voltage levels. Furthermore, the sensor material can be a stainless steel metal ring or highly conductive copper tape. The selection criteria are a balance between conductivity and installation fit, and it is not limited to a single material. This embodiment does not impose strict limitations. It should also be noted that the sensor must be tightly and smoothly fitted to the external insulation surface during installation, without any wrinkles or gaps. This is to ensure the stability of the coupling capacitance and avoid signal fluctuations caused by poor contact, which is a key detail for improving coupling efficiency.

[0082] The signal acquisition module 14 is used to synchronously acquire the excitation voltage signal output by the pulse generation module 11 and the response signal of the transformer winding. First, it is necessary to ensure that the excitation signal and the response signal are synchronized in time, which will directly affect the accuracy of the frequency response curve. Therefore, this module ensures that the two signals are acquired at the same time through the timing control of the FPGA controller 16 to avoid phase deviation caused by time difference.

[0083] On the other hand, the signal input terminal of the signal acquisition module 14 is connected to the pulse generation module 11 and the transformer neutral point grounding wire, respectively: the former acquires the excitation voltage signal, and the latter acquires the response current signal, thereby generating a frequency response curve. It should be noted that the current signal at the transformer neutral point grounding wire can accurately reflect the impedance characteristics of the winding.

[0084] The signal processing module 15 is used to process the acquired signal and generate a frequency response curve, transforming the original time-domain signal into frequency-domain characteristics that reflect the winding state. Firstly, the signal processing is not a simple filtering or amplification process, but rather employs time-frequency analysis algorithms (using short-time Fourier transform or wavelet transform, etc., to process the excitation and response signals). Compared to traditional fast Fourier transform (FFT) algorithms, these algorithms can better locate the signal and noise in the time and frequency domains, suppressing noise while preserving, to the maximum extent possible, key characteristic information in the frequency response curve, such as resonance peaks and valleys, that characterize the winding state.

[0085] After generating the frequency response curve, it can be compared with the baseline health curve obtained before transformer commissioning or during the last maintenance. Quantitative analysis is performed using indicators such as correlation coefficient (CC) and standard deviation (SD). The curve can be input into a pre-trained deep learning model (such as a convolutional neural network), which will automatically identify curve features and output diagnostic results for the winding condition (such as "health," "radial deformation," and "axial deformation"). It should also be noted that the processed frequency response curve covers a frequency range of 10kHz-5MHz, including both the low-to-mid-frequency bands sensitive to winding deformation and high-frequency characteristics, ensuring comprehensive diagnostics.

[0086] The anti-interference pulse coupling injection device provided in this application comprises a pulse generation module 11, a coupling sensing module 13, a signal injection protection module 12, a signal acquisition module 14, a signal processing module 15, and an FPGA controller 16, forming a complete system. The FPGA controller 16 serves as the core control unit, regulating each module. The pulse generation module 11 employs a multi-stage Marx circuit structure with series-connected full-bridge switched capacitor units, connected to a high-voltage DC charging power supply. Under the control of the FPGA controller 16, it can output positive, negative, or alternating positive and negative bipolar pulse signals, adjusting the pulse parameters. The signal injection protection module 12 processes the pulse signal in the signal transmission path. The coupling sensing module 13 improves coupling efficiency through its installation method of being attached to the outer insulation surface of the transformer's high-voltage bushing. The acquisition end of the signal acquisition module 14 is connected to both the pulse generation module 11 and the transformer neutral point grounding wire, synchronously acquiring the excitation voltage signal and the transformer winding response signal to ensure the integrity and synchronization of signal acquisition. The signal processing module 15 receives the acquired signals and generates a frequency response curve, providing direct evidence for diagnosing winding deformation conditions and improving the reliability of fault identification.

[0087] According to the above embodiments, specifically, as follows: Figure 2.1 As shown, each stage of the full-bridge switched capacitor unit of the pulse generation module 11 includes: energy storage capacitor VC, first switch A, second switch B, third switch C, fourth switch D, branch switch Sch, and diode Di; (the subscripts corresponding to each unit are 1, 2...n);

[0088] The negative terminal of the diode is connected to the first terminal of the branch switch; the second terminal of the branch switch is connected to the first terminal of the first switching transistor A, the first terminal of the energy storage capacitor, and the first terminal of the third switching transistor C; the second terminal of the first switching transistor A is connected to the first terminal of the second switching transistor B; the second terminal of the second switching transistor B is connected to the second terminal of the energy storage capacitor and the second terminal of the fourth switching transistor D; the second terminal of the third switching transistor C is connected to the first terminal of the fourth switching transistor D; the positive terminal of the diode serves as the first input terminal of the full-bridge switched capacitor unit; the second terminal of the first switching transistor A serves as the second input terminal of the full-bridge switched capacitor unit; the first terminal of the third switching transistor C serves as the first output terminal of the full-bridge switched capacitor unit; and the second terminal of the third switching transistor C serves as the second output terminal of the full-bridge switched capacitor unit.

[0089] The control terminals of the first switch A, the second switch B, the third switch C, the fourth switch D, and the branch switch are connected to the FPGA controller 16.

[0090] like Figure 2.1As shown, this topology uses full-bridge (FB) switch-capacitor cells (SCCs) connected in series. These cells can generate positive and negative pulses through different states of different switches. The semiconductor switch used in each SCC is independently controlled, allowing for simultaneous output of positive and negative pulses from a shared capacitor. Furthermore, the operation of each SCC cell is independently controlled, enabling not only simple voltage control but also advanced control of pulse parameters.

[0091] The positive terminal of the diode serves as the first input terminal, used to connect to the positive terminal of the high-voltage DC charging power supply or to the first output terminal of the previous stage; the second terminal of the first switch A serves as the second input terminal, used to connect to the negative terminal of the high-voltage DC charging power supply or to the second output terminal of the previous stage; the second terminal of the third switch is used to output pulse signals of different polarities.

[0092] During pulse output, after the charging power supply charges the capacitor, the capacitor is isolated from the charging circuit by turning off the charging switch, thereby achieving the desired output for each SCC (Signal Capacitor). Figure 2.1 The series connection of units SCC1, SCC2, and SCCn in the diagram ensures normal pulse generation. The schematic diagrams of each stage's operation and their underlying principles are as follows: In the diagrams, gray lines represent unconnected lines, and black lines represent connected lines.

[0093] ① Charging stage: such as Figure 2.2 As shown, a high-voltage DC power supply Vin charges C1 through diode Sch1 of the first-stage SCC unit, then charges C2 through diode Sch2 of the second-stage SCC unit, and so on. in The capacitors in each stage will be charged in parallel, ultimately making the capacitor voltage of each unit equal to the output voltage of the high-voltage DC power supply, i.e., V. in =V C1 =V C2 =V C3 =…=V C7 .

[0094] ② Positive polarity output stage: such as Figure 2.3 As shown, after the charging process, by controlling the switches B1~B7 and C1~C7 of each SCC unit to be turned on, and the switches A1~A7 and D1~D7 of each module to be turned off, diode D... i1 ~D i7 Due to reverse bias, the circuit is cut off, and Sch1~Sch7 are turned off. Each capacitor and the switch form a series circuit to discharge to the load resistor. The positive pulse discharge circuit is B1-V. C1 -C1-B2-Vc2-C2~B7-V C7-C7-load-ground, ultimately a total of 7Vin positive pulses will be formed on the load.

[0095] ③ The positive and negative polarity interval stage: such as Figure 2.4 As shown, after positive discharge, in order to prevent competition hazards between switches, a transition between positive and negative discharge stages is achieved through a stage in which only B1~B7 and D1~D7 remain open.

[0096] ④ Negative polarity discharge stage: such as Figure 2.5 As shown, after the interval phase process, by controlling the switches A1~A7 and D1~D7 of each SCC unit to be turned on, and the switches B1~B7 and C1~C7 of each module to be turned off, diode D... i1 ~D i7 Due to reverse bias, the circuit is cut off, and Sch1~Sch7 are turned off. Each capacitor and the switch form a series circuit to discharge to the load resistor. The negative pulse discharge circuit is D7-V. C7 -A7-D6-V C6 -A6~D1-V C1 -A1-ground-load, ultimately a total of -7V will be formed on the load. in The negative pulse.

[0097] Since noise is present at the transformer site, and the response voltage generated by the pulse coupling injection method is too small, it will be drowned out by the noise, resulting in an inability to obtain an effective response signal. Therefore, from a practical engineering perspective, increasing the amplitude can effectively increase the corresponding response amplitude, thereby enabling effective response signal extraction. Thus, it is recommended to increase the pulse output amplitude. However, considering the limitations of transformer insulation levels and creepage distances, as well as the differences in withstand voltage and coupling ratio caused by different transformer sizes, the amplitude of the pulse generator is still subject to some limitations. Therefore, for verification, this application uses electronic circuit simulation software to build a 2D model of a 30-panel transformer and measures the coupling voltage on each winding stage by setting coupling injection sensors and pulse excitation. Part of the 2D model is shown below. Figure 3.1 , Figure 3.2 As shown, the measurement results are as follows Figure 3.3 As shown.

[0098] Under pulse excitation with an amplitude of 1000V, a rise and fall edge of 30ns, a pulse width of 500ns, and a frequency of 10Hz, the voltage on the winding gradually decreases from the first pulse, with a maximum amplitude of approximately 16V. This voltage varies across transformers of different voltage levels and sizes. Simulation results show that even after increasing the voltage several times, the voltage on the winding still does not exceed 1000V. Therefore, under actual operating conditions, the pulse amplitude should be appropriately increased to improve the response, but the voltage amplitude is still limited by the transformer size.

[0099] Currently, the pulse excitation used in pulse-coupled injection methods is mostly nanosecond pulses. Therefore, to achieve the target function and realize a peak output of 7kV nanosecond pulse, a 300Ω pure resistive load was selected for testing. The maximum current I that each stage of the circuit can handle during operation was calculated. m =7kV / 300Ω=23.3A, therefore, the first switch A, the second switch B, the third switch, the fourth switch, and the branch switch are selected as metal-oxide-semiconductor transistors (MOSFETs) of model IMZ120R030M1H as the main switching devices, and diodes of model DSEI60-12A.

[0100] To provide a stable DC power supply, the device uses the DW-P102-30F53, which outputs a DC voltage of 0~1000V and an output current of 30mA. This DC power module has short-circuit protection.

[0101] According to circuit principles, the capacitors in each module serve two functions: energy storage and energy transmission. Therefore, the peak voltage rating and capacitance value of the capacitors are considered when selecting them. Simultaneously, to meet the voltage requirements of the main switch, the capacitor's voltage rating should be greater than the operating voltage of the switching device; therefore, a 1200V capacitor is selected. To achieve higher performance requirements, the output square wave is set to have a maximum voltage drop of 10% at the maximum pulse width and frequency. The corresponding capacitance value satisfies the following formula:

[0102] ;

[0103] Among them, C N V is the equivalent series capacitance of the 7-stage module; C is the capacitance of each stage module; τ is the maximum pulse width; V o The amplitude of the output pulse voltage; ΔV d This represents 10% of the maximum drop in output pulse voltage. is the load resistance; N is the number of stages in the switching unit.

[0104] According to the above formula, the energy storage capacitor value of each module should not be less than 0.19μF. Therefore, in order to leave a certain margin, a 1μF CBB22 capacitor with a working voltage of 1000V was selected as the energy storage capacitor of each module.

[0105] Furthermore, to achieve pulse output of different polarities on a single pulse generator, a synchronous trigger control signal needs to be designed. Since the control signal switches the capacitor connection mode by controlling the on / off state of the MOSFET switches in each module, thus ensuring the load receives the required pulse, a method such as... Figure 3.4The switching timing controls the charging switch and the unit's main switch. To facilitate the adjustment of key parameters such as the positive discharge pulse width, the positive and negative polarity interval pulse width, and the negative discharge pulse width during field use, a parameter control module was developed using a field-programmable gate array (FPGA), which can achieve free control of the output parameters.

[0106] like Figure 3.4 As shown, within one operating cycle, the timing sequence satisfies the cycle of capacitor charging phase - positive polarity output phase - positive and negative polarity output interval phase - negative polarity output phase - capacitor charging phase. The dead time, positive polarity pulse width, charging interval time, and negative polarity pulse width are all adjustable. By setting the positive polarity pulse width to 0, unipolar output of negative polarity pulse can be achieved. Setting the negative polarity pulse width to 0 can achieve unipolar output of positive polarity pulse. Simultaneously setting the positive and negative polarity pulse widths can achieve bipolar output.

[0107] Specifically, the coupling sensing module 13 is made of a stainless steel metal ring, and the width of the metal strip is positively correlated with the signal coupling ratio. The width of the metal strip is adjustable.

[0108] The coupling sensing module 13 is made of a stainless steel metal ring. The material was not chosen arbitrarily, but was determined by comprehensively considering the transformer's on-site operating conditions and coupling performance requirements. It has good conductivity (ensuring signal coupling efficiency), weather resistance (adapting to the high humidity and large temperature difference environment of substations), and mechanical strength (preventing deformation during installation or long-term operation). Compared with ordinary metals, it can reduce the impact of oxidation and corrosion on the stability of the coupling capacitor.

[0109] According to the capacitive coupling formula, the size of the coupling capacitance is positively correlated with the area of ​​the plates facing each other. Increasing the width of the metal strip will expand the area of ​​the sensor and the high-voltage conductor of the transformer facing each other, thereby increasing the coupling capacitance and the coupling ratio.

[0110] To verify the relationship between the metal strip width and the coupling ratio, experiments were conducted on transformers of different grades.

[0111] (1) The test was conducted with the 110kV bushing offline. The experimental procedure was to wrap a thin copper strip around the outer insulation layer of the high-voltage bushing near the grounding flange, inject a voltage signal through CCS and measure the response signal to obtain the frequency response curve. The 110kV bushing is an independent bushing. Since it was not possible to customize a stainless steel metal ring that was wide enough, a metal ring made of 304 stainless steel and copper metal tape were used as capacitive coupling sensors in the experiment.

[0112] Considering the complex electromagnetic environment and interference at the site, the response signal injected into the transformer winding via the guide rod will experience significant attenuation after passing through the winding. Therefore, to further improve the coupling ratio, the width of the capacitive coupling sensor was increased to 7 cm, and the experiment was conducted again. Increasing the width of the capacitive coupling sensor is equivalent to increasing the area of ​​the two plates facing each other; a larger coupling capacitor should result in a larger coupling ratio. Parameter experiments with different excitation amplitudes were conducted in the laboratory, and the corresponding coupling response voltages were obtained. Each experiment was repeated three times. The injected signal was a unipolar negative pulse square wave with a pulse width of 500 ns and a frequency of 10 Hz. The specific injected excitation amplitude and response amplitude measurements for sensors with different widths are shown in Tables 1 and 2.

[0113] Table 1. Measurement of excitation and response of 2cm coupled injection sensor

[0114]

[0115] Table 2. Measurement of Excitation and Response of 7cm Coupled Injection Sensor

[0116]

[0117] Experimental tests show that different widths of the coupling injection sensor have a significant impact on the coupling response amplitude. Wider coupling injection sensors achieve a higher signal-to-noise ratio (SNR). Therefore, in high-voltage devices, wider capacitive coupling sensors can be considered to achieve a higher SNR. This also verifies that increasing the amplitude has little effect on improving the SNR. The specific experimental waveforms of the 7cm coupling injection sensor are shown below. Figure 4.1 , 4.2 As shown.

[0118] As can be observed from the waveforms, the corresponding response waveforms do not differ significantly when different excitation amplitudes are injected; only the amplitude differs. Considering the safety hazard related to creepage distance between the coupled sensor and the flange when the excitation voltage is injected, the excitation voltage cannot be increased indefinitely in actual experiments; the specific voltage depends on the structure of the transformer bushing itself.

[0119] (2) Select a 220kV main transformer to carry out transformer pulse frequency response test based on capacitive coupling injection. The experiment adopts an offline-online experimental method to obtain the frequency response curves of the transformer under different operating conditions.

[0120] The high-voltage winding and medium-voltage winding of the 220kV power transformer are Y-connected, while the low-voltage winding is Δ-connected. During testing, all experiments used the same pulse signal as excitation parameters: amplitude 1500V, pulse width 600ns, and frequency 50Hz. To avoid errors caused by different wiring configurations, the wiring for all experiments under the same configuration remained unchanged, and the excitation phase used in the experiments was always the 220kV side. The experimental wiring diagram is shown below. Figure 4.3 , 4.4 As shown.

[0121] During offline coupling measurement on the high-voltage side, all winding terminals are left floating, and the positive output of the pulse source is connected to the sensor via a wire, while the negative output of the pulse source is connected to ground potential. The high-voltage neutral point is grounded, and a Pearson 7790 is used to measure the current signal. A voltage probe is used to measure the voltage signal at the high-voltage neutral point sensor. The online coupling injection wiring procedure is the same as the offline procedure. After wiring, three-phase power is connected through the three-phase bus for live testing. During the offline experiment, the neutral point current and coupling voltage of the three phases A on the high-voltage side are measured first. The experimental waveforms are as follows: Figure 4.5 , 4.6 As shown.

[0122] To avoid experimental problems caused by pulse generator issues during testing, all experiments were conducted offline, acquiring the neutral point current curve and AO coupling voltage measurement curve. The experiments were repeated five times, and the waveforms were averaged 128 times before being saved. The obtained curves show good excitation stability. Furthermore, to compare the effects of current and voltage measurement methods on the frequency response curve, the two curves were compared. Figure 4.7 As shown.

[0123] Comparative observation reveals that the neutral point current measurement method exhibits a significant resonance trough around 30kHz, while the voltage-coupled method shows an additional small resonance trough around 330kHz. The resonance trough is more pronounced in the 550kHz-650kHz range for the neutral point current measurement method, but there is no significant difference in the frequency response curves at 650kHz and above. The overall trends of the two methods are nearly identical. In practical measurements, if a suitable measurement environment cannot be provided for the current measurement probe, the voltage-coupled method can be used.

[0124] Meanwhile, considering the different transformer operating states and wiring configurations when the three phases are suspended offline, connected to the three-phase bus, and online, as well as the potential differences in frequency response curves due to different injection phases when excitation is injected into phases A, B, and C, relevant comparative experiments were conducted. Specific experimental curves are shown below. Figure 4.8 , 4.9 As shown.

[0125] Before conducting the online experiment, to ensure the safety of the method, a switch was added at the excitation signal injection end for protection. The return voltage of the capacitively coupled sensor and the switch voltage were measured respectively, and the measurement results are as follows: Figure 4.10 , 4.11 As shown, the voltage waveform transmitted back to the excitation side from the coupling sensor via the wire was measured before the online experiment, and the magnitude was less than 1 volt; the voltage of the switch was measured to be less than 0.5 volts, indicating that the online experiment could be carried out safely.

[0126] Specifically, the signal injection protection module 12 also includes: a voltage monitoring unit and a fast-acting mechanical isolating switch;

[0127] The voltage monitoring unit monitors the induced voltage returned by the coupling sensing module 13 in real time. When the voltage exceeds the preset threshold, it triggers the mechanical isolation switch to cut off the pulse injection circuit.

[0128] The voltage monitoring unit utilizes a high-precision, wide-bandwidth voltage sensor (such as a voltage divider probe) adapted to a monitoring frequency band of 10kHz~1MHz, achieving a measurement accuracy of ≤±1%. This allows for precise capture of the weak induced voltage (<1V under normal conditions) returned by the coupled sensing module 13, while also enabling rapid response to sudden overvoltages. An integrated low-noise signal conditioning circuit amplifies and filters the monitored voltage signal before transmitting it to the trigger logic unit, preventing false triggering due to electromagnetic interference. For example, an RC filter circuit filters out high-frequency noise, ensuring a response only to genuine overvoltage signals.

[0129] Mechanical isolating switches should be high-voltage fast isolating switches (rated voltage ≥ 5kV, rated current ≥ 10A), with an action response time ≤ 10ms. They should be able to quickly cut off pulse injection circuits and withstand reverse impact voltage from transformer high-voltage bushings, preventing self-breakdown. An arc-extinguishing device and a spring-operated mechanism can be used. The arc-extinguishing device suppresses the arc generated when cutting off the high-voltage circuit, preventing arc burning of contacts or secondary faults. The spring-operated mechanism ensures the consistency and reliability of the switch's action, preventing protection failure due to mechanical jamming. The switch's control terminal is directly connected to the trigger output terminal of the voltage monitoring unit, while a 16-linkage interface for the FPGA controller is reserved, achieving dual protection of local fast triggering and remote intelligent control. Local triggering prioritizes response to sudden overvoltages, and the FPGA can be programmed with additional protection logic (such as timed self-testing and manual emergency disconnection).

[0130] Secondly, considering that different wiring and operating states may lead to differences in frequency response curves when injecting excitation into the same phase, the frequency response curve for phase A was obtained by measuring the neutral point current in three states: offline (three-phase suspended), offline (three-phase connected), and online. The different curves were then compared and analyzed. Specific experimental curves are shown below. Figure 4.12 As shown.

[0131] When using neutral point current measurement to obtain frequency response curves, significant differences were observed between the frequency response curves with and without three-phase lines connected. Specifically, these differences manifested in the overall amplitude of the curves and significant differences in the resonance peaks and valleys above 550kHz. With three-phase lines connected, only slight differences were observed between the offline and online frequency response curves. Experiments show that the transformer's operating state has a negligible impact on the frequency response curve when three-phase lines are connected using pulse-coupled injection. In practical production applications, offline and online states only refer to whether the transformer is powered, not the connection or disconnection of the three-phase busbars. Therefore, this method can effectively compare and analyze offline and online frequency response curves.

[0132] Finally, to verify the safety and effectiveness of the pulse-coupled injection method in online operation, online experiments will be conducted with different percentage loads. Frequency response curves will be obtained using coupling voltage measurement and neutral point current measurement. Specific experimental curves are shown below. Figure 4.13 , 4.14 As shown.

[0133] (3) A winding fault experiment was carried out on a 10kV transformer. During the experiment, a pulse square wave with fixed parameters was injected as the excitation. Its amplitude was 1000V, the frequency was 10Hz, and the pulse width was 500ns. The neutral point current was measured by Pearson7790 to obtain the response signal.

[0134] The experiment first conducted offline and online tests based on pulse coupling injection under normal transformer conditions. Frequency response curves were then obtained under the same offline conditions using a TDT-6U winding deformation tester. Specific curve comparisons are shown below. Figure 4.15 As shown.

[0135] The curve comparison shows that the frequency response curves obtained by the winding deformation tester and the pulse coupling injection method are highly similar. This indicates that under the same offline conditions, both methods can obtain the same frequency response curve. Therefore, it can be extended to use the pulse coupling injection method to replace the winding deformation tester for detection in online experiments, thereby realizing the online condition monitoring function of transformers.

[0136] To further verify the different effects of different wiring methods and operating states on the results obtained by pulse coupling injection, tests were conducted on the transformer in the following states: three-phase unloaded state, three-phase connected to the bus but not energized state, and three-phase energized state. The test results are shown in Figure 4.16.

[0137] Experimental tests revealed significant changes in the waveform before and after connecting a three-phase power supply in offline conditions. Specifically, the amplitude of the curve increased within the 100-300kHz frequency range, the overall curve shifted downwards, the resonant peaks and valleys of the 400kHz and 560kHz curves disappeared, and the resonant peaks and valleys of the 700kHz-900kHz curve reversed. After connecting a three-phase power supply, both offline and online tests were conducted. The results showed that after connecting a 380V three-phase AC power supply, the amplitude of the curve increased within the 700-800kHz frequency range, the curve shifted downwards, the overall curve showed a slight downward trend, and the waveform did not change significantly.

[0138] Comparing the frequency response curves of the corresponding wiring methods and operating conditions of the 220kV transformers, the two transformers of different voltage levels showed similar results: under the same wiring conditions, the main difference in the frequency response curves in the low and medium frequency bands with and without three-phase busbar connection was the amplitude difference, while in the mid and high frequency bands, there was a reversal of the resonance peak and valley. Therefore, when actually testing the transformer winding condition, the frequency response curves in the offline and online states should be uniformly measured by connecting to the three-phase busbar, so as to compare them with the measurement results of the winding deformation tester during the factory test.

[0139] Specifically, the signal injection protection module 12 is a passive dual-T notch filter network, which consists of two T-type RC networks.

[0140] The signal injection protection module 12 adopts a passive dual-T notch filter network, which consists of two symmetrical T-type RC networks. This structure is designed to meet the precise filtering requirements of common-mode interference at specific frequencies in substations.

[0141] like Figure 5.1 As shown, the first T-type RC network consists of one resistor and two capacitors. The resistor is connected in series in the main signal path, and the two capacitors are connected in parallel between the two sides of the resistor and ground, forming a "resistor-capacitor" T-type topology. The second T-type RC network consists of two resistors and one capacitor. The two resistors are connected in series in the two sides of the main signal path, and the capacitor is connected in parallel between the common node of the two resistors and ground, forming a "capacitor-resistor" reverse T-type topology.

[0142] To filter interference signals with an amplitude of 100kHz, a system was built based on calculations as follows. Figure 5.2 The circuit simulation model shows a resistor R of 100Ω and a capacitor of 15.9nF. The frequency and phase frequency characteristics of the filtering effect are as follows: Figure 5.3 ,5.4 As shown, the filter circuit can achieve both forward all-pass and reverse power frequency filtering. However, for interference with variable frequency ranges that may span the entire effective frequency range of the frequency response curve, an adaptive filter is required. This filter parameter should be dynamically adjusted according to the characteristics of the input signal to adapt to different interference conditions.

[0143] Based on the entire testing process, anti-interference schemes can be set separately for the pulse generator, transmission line, and measuring device. Firstly, regarding the pulse generator, even if the pulse excitation is continuously output with the same parameters, it cannot be guaranteed that the excitation for each output will be completely consistent. Therefore, developing a more stable pulse generator is an effective approach. Since the control signals before the pulse generator's drive are easily affected by electromagnetic interference, a fully enclosed grounded metal casing can be added to the FPGA control terminal for electromagnetic shielding to suppress potential electromagnetic interference in the substation. The pulse generator contains a high-voltage pulse generation module 11 and a low-voltage signal control module; therefore, these two modules also need to be isolated. Similar to the independent electromagnetic shielding method for the weak current modules, electromagnetic and electrostatic shielding can be achieved by adding a grounded metal casing to each part. The pulse coupling injection method wiring method is as follows: Figure 5.5 As shown, corresponding anti-interference schemes can be added to it.

[0144] Anti-interference solutions can be implemented not only through hardware facilities but also through software functions. Filtering methods need to consider factors such as signal characteristics, interference types, and processing requirements. Regarding data storage, when using an oscilloscope or other acquisition devices to store signal data, averaging can provide basic but highly effective filtering. Compared to the Fast Fourier Transform, current time-frequency analysis methods similar to wavelet transform can reduce noise in measurement results to some extent and ensure that effective information about resonance peaks and valleys is not lost. Therefore, different time-frequency analysis methods can be used to process the data, and algorithms can be improved for the frequency range required for transformer fault diagnosis to reduce interference while ensuring signal integrity.

[0145] Specifically, the signal acquisition module 14 includes a current measuring device; the signal processing module 15 includes a data acquisition card.

[0146] The current measuring device is clamped to the neutral point grounding wire of the transformer and is used to measure the response current signal;

[0147] The data acquisition card is connected to the pulse generation module 11 and the current sensor to synchronously acquire the excitation voltage signal output by the pulse generation module 11 and the response current signal sensed by the current measuring device.

[0148] Signal acquisition module 14 includes: a voltage measuring device;

[0149] The voltage measuring device is clamped to the neutral point of the transformer to measure the response voltage signal;

[0150] The data acquisition card is connected to the voltage measuring device and receives the response voltage signal sensed by the voltage measuring device.

[0151] like Figure 4.3 , Figure 4.4 As shown, the clamps of the current measuring device are tightly clamped onto the neutral point grounding wire of the transformer, ensuring full contact with the conductor and reducing measurement errors caused by contact resistance. The signal output terminal of the sensor is connected to the first signal input terminal of the data acquisition card through a high-voltage shielded wire. The grounding layers at both ends of the shielded wire are reliably grounded to suppress electromagnetic interference during transmission. The second signal input terminal of the data acquisition card is connected to the excitation signal output terminal of the pulse generation module 11 through a coaxial cable. The characteristic impedance matching of the coaxial cable avoids amplitude attenuation and waveform distortion caused by signal reflection.

[0152] The signal output of the voltage measurement device is connected to the spare signal input of the data acquisition card via a coaxial cable to avoid amplitude attenuation and waveform distortion caused by signal reflection. The data acquisition card configures the channel parameters through the FPGA controller 16 to keep the sampling rate and resolution of the voltage measurement channel consistent with those of the current measurement channel (e.g., sampling rate 10MS / s, resolution 16 bits), ensuring the synchronous acquisition of the response signal.

[0153] Specifically, it also includes: multiple metal shielding shells;

[0154] The pulse generation module 11, the FPGA controller 16, and the signal acquisition module 14 are each equipped with a fully enclosed and grounded metal shielding shell.

[0155] The fully enclosed structure isolates electromagnetic interference. The pulse generation module 11, FPGA controller, and signal acquisition module 14 are each equipped with a fully enclosed metal shielding shell. The core function is to block the propagation path of electromagnetic interference: blocking strong electromagnetic interference from outside the substation, preventing intrusion into the weak current control circuit (FPGA) and sensitive acquisition links, and ensuring signal purity. The high-voltage pulse electromagnetic radiation generated by the pulse generation module 11 during operation is limited by its own shielding shell, preventing interference with the normal operation of other modules.

[0156] The core purpose of grounding the shielding shell is to quickly release the captured electromagnetic interference energy and conduct the electromagnetic interference collected by the shielding shell to the ground, so as to prevent the interference from accumulating inside the shell or entering the module.

[0157] Specifically, the full-bridge switched capacitor units of the pulse generation module 11 are arranged in a centrally symmetrical manner, and the corresponding control terminals are arranged in a preset order at the signal transmission terminal of the FPGA controller 16.

[0158] The full-bridge switched capacitor units at each stage are arranged in a centrally symmetrical manner. This symmetrical layout ensures that the distance from the FPGA controller 16 to the control terminals of each unit is consistent, reducing the difference in control signal transmission delay (≤5ns), ensuring synchronous switching action of all units, and avoiding uneven pulse amplitude or waveform distortion caused by timing deviations. The centrally symmetrical design also ensures uniform heat distribution among the units, preventing localized overheating; at the same time, it is compatible with the overall housing structure of the pulse generation module 11, reducing wiring intersections and improving installation and maintenance convenience.

[0159] The corresponding control terminals are arranged in a preset order at the FPGA controller signal transmitter (e.g., AD and BC arranged sequentially). This fixed order ensures that the FPGA controller's control signal outputs correspond one-to-one with the cell layout, eliminating the need for complex address mapping, reducing programming difficulty, and minimizing logic errors. The sequential, centralized arrangement of the control terminals facilitates connections using ribbon cables or strip cables, reducing wiring length and intersections, lowering electromagnetic interference during signal transmission, and improving control signal integrity.

[0160] Specifically, the signal injection protection module 12 is connected to the pulse generation module 11 via a coaxial cable, and the signal injection protection module 12 is connected to the coupling sensing module 13 via a high-voltage shielded wire.

[0161] The signal injection protection module 12 and the pulse generation module 11 are connected via a coaxial cable to avoid amplitude attenuation and waveform distortion caused by signal reflection, ensuring that the fast edge (nanosecond level) and spectral characteristics of the pulse signal are not lost. The coaxial metal shielding layer can suppress spatial electromagnetic interference, reduce the impact of corona discharge and fast transient pulse groups on the signal in the substation environment, and ensure the purity of the excitation signal received by the injection protection module.

[0162] The signal injection protection module 12 and the coupling sensing module 13 are connected by a high-voltage shielded cable with a high withstand voltage rating (≥5kV), which can withstand the high-voltage reverse coupling voltage on the transformer bushing side, preventing cable breakdown and ensuring system safety. The shielding layer can block electromagnetic radiation and conducted interference in the high-voltage environment, prevent the filtered clean signal from being contaminated again, and reduce signal transmission attenuation, ensuring that the coupling sensing module 13 obtains a sufficiently strong excitation signal.

[0163] The anti-interference pulse coupling injection device provided in this application has been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0164] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

Claims

1. An anti-interference pulse coupling injection device, characterized in that, include: Pulse generation module, coupling sensing module, signal injection protection module, signal acquisition module, signal processing module, FPGA controller; The FPGA controller is connected to the pulse generation module, the signal injection protection module, the signal acquisition module, and the signal processing module, respectively. The pulse generation module is a multi-stage Marx circuit structure based on a series connection of full-bridge switched capacitor units. The FPGA controller controls the pulse generation module to output positive, negative, or alternating positive and negative bipolar pulse signals. The input terminal of the pulse generation module is connected to a high-voltage DC charging power supply, and the output terminal of the pulse generation module is connected to the input terminal of the signal injection protection module. The signal injection protection module is used to filter out common-mode interference at a specific frequency, inject pulse signals forward, provide high-voltage isolation protection, and cut off abnormal overvoltage. The output terminal of the signal injection protection module is connected to the input terminal of the coupling sensing module. The coupling sensing module is a capacitive coupling sensor, which is used to be sleeved on the high-voltage bushing of the transformer and to be in contact with the outer insulating surface of the high-voltage bushing of the transformer. The signal acquisition module is used to synchronously acquire the excitation voltage signal output by the pulse generation module and the response signal of the transformer winding; the signal input terminal of the signal acquisition module is connected to the pulse generation module and the transformer neutral point grounding wire respectively, and the signal output terminal of the signal acquisition module is connected to the input terminal of the signal processing module. The signal processing module is used to process the signals transmitted by the signal acquisition module and generate frequency response curves.

2. The anti-interference pulse coupling injection device according to claim 1, characterized in that, Each stage of the full-bridge switched capacitor unit of the pulse generation module includes: an energy storage capacitor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a branch switch, and a diode; The negative terminal of the diode is connected to the first terminal of the branch switch; the second terminal of the branch switch is connected to the first terminal of the first switching transistor, the first terminal of the energy storage capacitor, and the first terminal of the third switching transistor; the second terminal of the first switching transistor is connected to the first terminal of the second switching transistor; the second terminal of the second switching transistor is connected to the second terminal of the energy storage capacitor and the second terminal of the fourth switching transistor; the second terminal of the third switching transistor is connected to the first terminal of the fourth switching transistor; the positive terminal of the diode serves as the first input terminal of the full-bridge switched capacitor unit; the second terminal of the first switching transistor serves as the second input terminal of the full-bridge switched capacitor unit; the first terminal of the third switching transistor serves as the first output terminal of the full-bridge switched capacitor unit; and the second terminal of the third switching transistor serves as the second output terminal of the full-bridge switched capacitor unit. The control terminals of the first switch, the second switch, the third switch, the fourth switch, and the branch switch are connected to the FPGA controller.

3. The anti-interference pulse coupling injection device according to claim 1, characterized in that, The coupling sensing module is made of a stainless steel metal ring, and the width of the metal strip is positively correlated with the signal coupling ratio. The width of the metal strip is adjustable.

4. The anti-interference pulse coupling injection device according to claim 1, characterized in that, The signal injection protection module is a passive dual-T notch filter network, which consists of two T-type RC networks.

5. The anti-interference pulse coupling injection device according to claim 4, characterized in that, The signal injection protection module also includes: a voltage monitoring unit and a fast-acting mechanical isolation switch; The voltage monitoring unit monitors the induced voltage returned by the coupling sensing module in real time. When the voltage exceeds a preset threshold, it triggers the mechanical isolation switch to cut off the pulse injection circuit.

6. The anti-interference pulse coupling injection device according to claim 1, characterized in that, The signal acquisition module includes a current measuring device; the signal processing module includes a data acquisition card. The current measuring device is clamped to the neutral point grounding wire of the transformer and is used to measure the response current signal; The data acquisition card is connected to the pulse generation module and the current sensor, and is used to synchronously acquire the excitation voltage signal output by the pulse generation module and the response current signal sensed by the current measuring device.

7. The anti-interference pulse coupling injection device according to claim 6, characterized in that, The signal acquisition module includes: a voltage measuring device; The voltage measuring device is clamped to the neutral point of the transformer and is used to measure the response voltage signal; The data acquisition card is connected to the voltage measuring device and receives the response voltage signal sensed by the voltage measuring device.

8. The anti-interference pulse coupling injection device according to claim 1, characterized in that, Also includes: Multiple metal shielding shells; The pulse generation module, the FPGA controller, and the signal acquisition module are each equipped with a fully enclosed and grounded metal shielding shell.

9. The anti-interference pulse coupling injection device according to claim 2, characterized in that, The full-bridge switched capacitor units of the pulse generation module are arranged in a centrally symmetrical manner, and the corresponding control terminals are arranged in a preset order at the signal transmission terminal of the FPGA controller.

10. The anti-interference pulse coupling injection device according to claim 1, characterized in that, The signal injection protection module is connected to the pulse generation module via a coaxial cable, and the signal injection protection module is connected to the coupling sensing module via a high-voltage shielded wire.

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