High-frequency discharge signal detection device and method based on commercial frequency current transformer

Abstract

This application provides a high-frequency discharge signal detection apparatus and method based on a commercial frequency current transformer, which can be used in the field of online monitoring of power devices. The apparatus comprises a signal acquisition module and a signal processing module. The signal processing module comprises a frequency divider circuit and an intelligent device. The signal acquisition module is connected to the secondary junction box of the commercial frequency current transformer of the transformer and is connected to the frequency divider circuit. The signal acquisition module is configured to acquire signals from the transformer and transmit the signals to the frequency divider circuit, the signals including a commercial frequency signal and a high-frequency discharge signal. The frequency divider circuit is connected to the intelligent device, which is configured to separate the commercial frequency signal and the high-frequency discharge signal and transmit the high-frequency discharge signal to the intelligent device. The intelligent device is configured to analyze the high-frequency discharge signal.

Description

Technical Field

[0001] This application claims the priority of the Chinese patent application with application number 202410034550.9 filed with the China National Intellectual Property Administration on January 10, 2024, and all the contents of this application are incorporated herein by reference.

[0002] This application relates to the field of online monitoring of electrical equipment, for example, to a high-frequency discharge signal detection device and method based on a commercial frequency current transformer.

Background Art

[0003] The transformer is a core equipment in the power grid. However, in recent years, many transformer explosion and combustion accidents have occurred, seriously affecting the reliable supply of power and the safety of the power grid, resulting in huge economic losses and adverse social impacts, and becoming an important potential risk in the power system. Such accidents are caused by insulation failures inside the transformer, gradually developing from partial discharges to insulation breakdown, and finally generating huge discharge energy, causing the transformer to explode and burn. As transformers in related technologies, differential protection is carried out after an obvious short-circuit current occurs, gas protection is carried out after a rapid oil flow due to insulation breakdown occurs, and main protection is activated after insulation breakdown in both cases, so the explosion and combustion accidents of transformers cannot be effectively prevented.

[0004] High-frequency discharge signals are commonly used detection signals for fault detection in power transformers. In related technologies, as shown in Figure 14, sensors for online monitoring of high-frequency local discharges are often located on the core or clamp, and the discharge coupling characteristics are relatively poor in the bushing and high-voltage lead-out areas, which are prone to causing deflagration failures in transformers. Compared to the measurement method of drawing the signal at the grounding point of the bushing end shield, the grounding method of the bushing end shield in related technologies needs to be improved. Potential risks such as poor grounding and moisture are likely to occur in the bushing end shield, and at the same time, improvements may easily cause new failures in the bushing, thereby increasing additional potential risks to the transformer. For example, if a new sensor is added and installed, the connection stability and sealing performance of the end shield may decrease, potentially causing failures such as water ingress and moisture to the insulation during operation, which may lead to a bushing explosion. [Overview of the project] [Problems that the invention aims to solve]

[0005] Embodiments of the present invention provide a high-frequency discharge signal detection device and method based on a commercial frequency current transformer, which can avoid structural changes to parts such as the transformer bushing end shield grounding section and at least partially solve problems present in related technologies. [Means for solving the problem]

[0006] In a first aspect, the present application relates to a high-frequency discharge signal detection device based on a commercial frequency current transformer, comprising a signal acquisition module and a signal processing module, The signal processing module comprises a frequency divider circuit and an intelligent device, The signal acquisition module is provided in the secondary junction box of the commercial frequency current transformer in the transformer, connected to the frequency divider circuit, and configured to acquire the transformer signal and transmit the signal, including the commercial frequency signal and the high frequency discharge signal, to the frequency divider circuit. The frequency divider circuit is connected to the intelligent device and configured to separate the commercial frequency signal from the high-frequency discharge signal and to transmit the high-frequency discharge signal to the intelligent device. The intelligent device is configured to analyze the high-frequency discharge signal. The present invention provides a high-frequency discharge signal detection device based on a commercial frequency current transformer.

[0007] Preferably, the intelligent device is A polarity discrimination module configured to determine the polarity of the high-frequency discharge signal, The system includes a location determination module configured to determine the location where a discharge fault occurred based on the results of polarity determination.

[0008] Preferably, the polarity discrimination module is A noise reduction module configured to remove noise from the aforementioned high-frequency discharge signal, An alignment module configured to align high-frequency discharge signals from different commercial frequency current transformers to obtain an alignment result, A polarity information generation module configured to generate polarity information based on the aforementioned alignment result, The system includes a result generation module configured to obtain polarity determination results based on the aforementioned polarity information and a preset threshold.

[0009] Preferably, the alignment module is A coefficient generation submodule configured to generate weighting coefficients using the mutual power spectra of high-frequency discharge signals from different commercial frequency current transformers, A function generation submodule configured to generate a broad cross-correlation function based on the weighting coefficients and the high-frequency discharge signals from the different commercial frequency current transformers, The system comprises a signal alignment submodule configured to align high-frequency discharge signals from different commercial frequency current transformers based on the extrema of the broad cross-correlation function.

[0010] Preferably, the intelligent device is The system further includes an early warning and protection module configured to provide early warning or protection for a fault based on the location where the discharge fault occurred.

[0011] Preferably, the signal acquisition module is The secondary connection box is provided with a signal shield terminal configured to prevent leakage of high-frequency signals, The system includes a coaxial cable configured to connect the signal shield terminal and the frequency divider circuit, and to transmit the signal to the frequency divider circuit.

[0012] Preferably, the signal shield terminal comprises a high-frequency terminal provided on the common terminal of the secondary connection box and a ground terminal provided on a terminal other than the common terminal of the secondary connection box.

[0013] Preferably, the high-frequency terminal comprises a copper conductor layer, a polyethylene insulating layer, a copper ground layer, a connecting bolt, an impedance matching device, and a BNC joint.

[0014] Preferably, the signal acquisition module further comprises a ground connection lead configured to connect the high-frequency terminal and the ground terminal to achieve signal shielding.

[0015] Preferably, the coaxial cable is a BNC coaxial cable, connecting the high-frequency terminal and the frequency divider circuit.

[0016] Preferably, the frequency divider circuit comprises a first low-pass filter and a high-frequency bandpass filter consisting of a second low-pass filter and a high-pass filter connected in parallel to the first low-pass filter. Equipped with a filter, The first low-pass filter is configured to separate the commercial frequency signal from the signal, The high-frequency bandpass filter is connected to the intelligent device and is configured to separate the high-frequency discharge signal from the signal and transmit the high-frequency discharge signal to the intelligent device.

[0017] As a second aspect, the present application provides a method for detecting a high-frequency discharge signal based on a commercial frequency current transformer, including: a signal collection module collects a signal in a transformer and transmits the signal to a frequency division circuit. The signal includes a commercial frequency signal and a high-frequency discharge signal. The signal collection module is provided in a secondary connection box of a commercial frequency current transformer in the transformer and is connected to the frequency division circuit. The frequency division circuit separates the commercial frequency signal and the high-frequency discharge signal and transmits the high-frequency discharge signal to an intelligent device. The intelligent device analyzes the high-frequency discharge signal.

[0018] Preferably, the frequency division circuit includes a first low-pass filter and a high-frequency bandpass filter connected in parallel to the first low-pass filter. The operation that the frequency division circuit separates the commercial frequency signal and the high-frequency discharge signal and transmits the high-frequency discharge signal to an intelligent device includes: The first low-pass filter separates the commercial frequency signal from the signal. The high-frequency bandpass filter separates the high-frequency discharge signal from the signal and transmits the high-frequency discharge signal to the intelligent device.

[0019] Preferably, the operation that the intelligent device analyzes the high-frequency discharge signal includes: The intelligent device discriminates the polarity of the high-frequency discharge signal. The intelligent device determines the position where a discharge fault has occurred based on the result of the polarity discrimination.

[0020] Preferably, the intelligent device determining the polarity of the high-frequency discharge signal includes: the intelligent device removing noise from the high-frequency discharge signal; the intelligent device aligning high-frequency discharge signals from different commercial-frequency current transformers to obtain an alignment result; the intelligent device generating polarity information based on the alignment result; the intelligent device obtaining a polarity determination result based on the polarity information and a preset threshold value.

[0021] Preferably, the intelligent device aligning high-frequency discharge signals from different commercial-frequency current transformers includes: the intelligent device generating a weight coefficient using the cross-power spectra of high-frequency discharge signals from different commercial-frequency current transformers; the intelligent device generating a generalized cross-correlation function based on the weight coefficient and the high-frequency discharge signals from different commercial-frequency current transformers; the intelligent device aligning the high-frequency discharge signals from different commercial-frequency current transformers based on the extreme values of the generalized cross-correlation function.

[0022] Preferably, the intelligent device further includes performing early warning or protection of the fault based on the position where the discharge fault occurs.

Brief Description of the Drawings

[0023] [Figure 1] It is a structural schematic diagram of a high-frequency discharge signal detection device based on a commercial-frequency current transformer according to an embodiment of the present application. [Figure 2] It is a structural schematic diagram of an intelligent device according to an embodiment of the present application. [Figure 3] It is a structural schematic diagram of an intelligent device according to an embodiment of the present application. [Figure 4] This is a schematic diagram of the structure of an intelligent device according to one embodiment of the present invention. [Figure 5] This is a schematic diagram of the structure of an intelligent device according to one embodiment of the present invention. [Figure 6] This is a schematic diagram of the structure of a high-frequency discharge signal detection device based on a commercial frequency current transformer according to one embodiment of the present invention. [Figure 7] This is a schematic diagram illustrating the structure of a high-frequency terminal and a ground terminal according to one embodiment of the present invention. [Figure 8] A schematic diagram of the structure of a frequency divider circuit according to one embodiment of the present invention. [Figure 9] This is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. [Figure 10] This is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. [Figure 11] This is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. [Figure 12] This is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. [Figure 13] This is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. [Figure 14] This is a schematic diagram illustrating the principle of the high-frequency pulsed current method in related technologies. [Figure 15] This is a comparison chart of transmission impedance curves for bushing commercial frequency current transformers and high frequency current transformers. [Figure 16] This is a schematic diagram of an internal discharge failure according to one embodiment of the present invention. [Figure 17] This is a schematic diagram of an external discharge failure according to one embodiment of the present invention. [Figure 18] This is a schematic diagram of pulse polarity according to one embodiment of the present invention. [Figure 19]This is a flowchart for aligning high-frequency discharge signals from different commercial frequency current transformers according to one embodiment of the present invention. [Figure 20] This is a flowchart showing how to arrange the signals collected by a transformer according to one embodiment of the present invention. [Figure 21] This is a flowchart for fault positioning according to one embodiment of the present invention. [Modes for carrying out the invention]

[0024] To further clarify the purpose, technical proposal, and advantages of the embodiments of this application, the embodiments will be described in detail below with reference to the drawings. Herein, the exemplary embodiments and their descriptions are for interpretive purposes only and do not limit this application. Notwithstanding that they do not contradict each other, the embodiments and features of the embodiments can be combined in any way.

[0025] In one embodiment, as shown in Figure 1, the high-frequency discharge signal detection device based on a commercial frequency current transformer according to the present invention comprises a signal acquisition module 101 and a signal processing module 102.

[0026] The signal processing module 102 comprises a frequency divider circuit 1021 and an intelligent device 1022.

[0027] The signal acquisition module 101 is installed in the secondary junction box of the commercial frequency current transformer in the transformer, connected to the frequency divider circuit 1021, and acquires the signal from the transformer. The signal is configured to be transmitted to the frequency divider circuit 1021. The signal includes a commercial frequency signal and a high-frequency discharge signal.

[0028] As shown in Figure 15, the present invention demonstrates that, as can be seen from the comparison curve of transmission impedance between bushing commercial frequency current transformers and high-frequency current transformers measured in the laboratory, bushing commercial frequency current transformers in transformers used for monitoring commercial frequency currents can achieve high responsiveness (1 mV / mA ​​or more) in the high-frequency band of 3 to 30 MHz where high-frequency local discharge signals are located, and are sufficient to meet the monitoring needs for high-frequency currents due to local discharge faults inside the transformer. In order to avoid the problem of poor coupling effect of external high-frequency current transformers to high-frequency discharge signals in the detection of high-frequency discharge signals, and safety issues due to improvements in bushing end shielding, the present invention proposes using a bushing commercial frequency current transformer in the transformer instead of a conventional high-frequency current transformer used for detecting local discharge faults. Furthermore, bushing commercial frequency current transformers are installed at the high-voltage, medium-voltage, low-voltage, and neutral points of the transformer, allowing for omnidirectional monitoring of high-frequency discharge signals inside the transformer to protect the transformer early and prevent deflagration.

[0029] In a transformer, the commercial frequency current transformer senses high-frequency discharge signals inside the transformer, collects these signals using a signal acquisition module 101 provided in the commercial frequency current transformer, and transmits them to a signal processing module 102 for processing. The commercial frequency current transformer can acquire information such as apparent discharge amount, discharge phase, and discharge frequency. The signal acquisition module 101 can collect signals from the transformer. These signals are multiband signals and include commercial frequency signals and high-frequency discharge signals. At the same time, the signal acquisition module 101 can also enable signal transmission from the wiring terminals of the commercial frequency current transformer in the transformer to the frequency divider circuit 1021.

[0030] The frequency divider circuit 1021 is connected to the intelligent device 1022 and is configured to separate the commercial frequency signal from the high-frequency discharge signal and transmit the high-frequency discharge signal to the intelligent device 1022.

[0031] For example, the frequency divider circuit 1021 may consist of a low-pass filter and a high-pass filter, enabling the separation and individual processing of the commercial frequency signal and the local discharge pulse signal.

[0032] The intelligent device 1022 is configured to analyze the high-frequency discharge signal.

[0033] For example, the intelligent electronic device (IED) 1022 first analyzes the high-frequency discharge signal, that is, it determines the polarity of the high-frequency discharge signal, and based on the result of the polarity determination, distinguishes whether the discharge fault is an internal discharge fault or an external discharge fault.

[0034] In one embodiment, as shown in Figure 2, the intelligent device 1022 comprises a polarity determination module 201 and a position determination module 202.

[0035] The polarity discrimination module 201 is configured to discriminate the polarity of the high-frequency discharge signal.

[0036] For example, transformer discharge faults can be divided into internal discharge faults and external discharge faults depending on the location where the fault occurs, and the polarity of the pulse current generated in each bushing commercial frequency current transformer differs depending on whether it is an internal or external discharge fault in the transformer. The Regent device 1022 enables the distinction and positioning of internal and external faults. For example, fault analysis is performed using a single-phase autowinding 500kV (or 500kV or higher) power transformer, and its structure is shown in Figure 16.

[0037] The location determination module 202 is configured to determine the location where the discharge fault occurred based on the results of polarity determination.

[0038] For example, a transformer may be equipped with multiple commercial frequency current transformers, allowing for simultaneous monitoring of high-frequency currents during operation. As shown in Figure 16, when an internal fault occurs, local discharge pulses can be detected on the secondary side of each wound commercial frequency current transformer and the secondary side of the neutral-grounded commercial frequency current transformer, and their polarities are opposite. Conversely, as shown in Figure 17, when an external fault occurs, the fault current is a through-current, and the polarity of the pulses detected in the wound commercial frequency current transformer and the neutral-grounded commercial frequency current transformer is the same. Based on this characteristic, the positioning module 202 can achieve positioning for discharge faults by detecting the polarity of the high-frequency discharge signal during the transformer's operation, and pulses of the same polarity and opposite polarity are shown in Figure 18.

[0039] In one embodiment, as shown in Figure 3, the polarity discrimination module 201 includes a noise reduction module 301, an alignment module 302, a polarity information generation module 303, and a result generation module 304.

[0040] The noise reduction module 301 is configured to remove noise from the high-frequency discharge signal.

[0041] For example, if the distance from the fault point to the commercial frequency current transformer is not constant, and there is a certain delay in the high-frequency discharge signals collected by different commercial frequency current transformers, as well as a certain amount of noise, then it is necessary to first denoise the high-frequency discharge signals collected by different commercial frequency current transformers. The noise reduction module 301 of the intelligent device 1022 can denoise the high-frequency discharge signals by methods such as wavelet soft thresholding, empirical mode decomposition, or smoothing noise reduction.

[0042] The alignment module 302 is configured to align high-frequency discharge signals from different commercial frequency current transformers to obtain an alignment result.

[0043] For example, due to the difference in distance from the location of a local discharge fault to different commercial frequency current transformers, there is a certain delay in the received pulse, and if polarity discrimination is performed as is, an anomaly may occur. The noise reduction module 301 of the intelligent device 1022 removes noise from the high-frequency discharge signal, and then the alignment module 302 of the intelligent device 1022 aligns the high-frequency discharge signals from different commercial frequency current transformers to obtain the alignment result. Here, the alignment of high-frequency discharge signals from different commercial frequency current transformers may be achieved according to phase, or by a generalized cross-correlation (GCC) method, and the present invention is not limited thereto.

[0044] The polarity information generation module 303 is configured to generate polarity information based on the alignment result and the high-frequency discharge signal.

[0045] Exemplary, the alignment module 302 of the intelligent device 1022 aligns local discharge pulse signals collected by different commercial frequency current transformers, and then the polarity information generation module 303 of the intelligent device 1022 generates polarity information based on the alignment result. Polarity information is generated. This polarity information is the distribution of same-polarity or opposite-polarity pulses within one period.

[0046] The result generation module 304 is configured to obtain polarity determination results based on the polarity information and a preset threshold.

[0047] For example, the results of polarity discrimination of a high-frequency discharge signal are divided into two types: same polarity and opposite polarity. The result generation module 304 of the intelligent device 1022 statistically analyzes the polarity distribution of pulses within one cycle and can distinguish between internal and external faults based on a preset threshold. For example, if the threshold is 75%, if the number of pulses with the same polarity within one cycle exceeds 75%, the result of polarity discrimination is determined to be the same polarity, and the fault is determined to be an external discharge fault. If the number of pulses with opposite polarity within one cycle exceeds 75%, the result of polarity discrimination is determined to be the opposite polarity, and the fault is determined to be an internal discharge fault.

[0048] In one embodiment, as shown in Figure 4, the alignment module 302 includes a coefficient generation submodule 401, a function generation submodule 402, and a signal alignment submodule 403.

[0049] The coefficient generation submodule 401 is configured to generate weighting coefficients by utilizing the cross-power spectra of high-frequency discharge signals from different commercial frequency current transformers.

[0050] Exemplary, to align and analyze high-frequency discharge signals from different commercial frequency current transformers, the intelligent device 1022 can process the high-frequency discharge signals by a broad cross-correlation method. In practice, the effects of reverberation and noise are present, and the broad cross-correlation function

number

number

[0051] Selection weight coefficients

number

number

[0052] However, ω represents the angular frequency.

number

number

number

[0053] The function generation submodule 402 is configured to generate a broad cross-correlation function based on the weighting coefficients and the high-frequency discharge signals from the different commercial frequency current transformers.

[0054] For example, the broad cross-correlation function describes the degree of correlation between the values ​​of random high-frequency discharge signals x1(s) and x2(t) at any two times s and t, and is defined as follows:

number

[0055] However, X1(s) represents the random variable corresponding to x1(s), and X2(t) represents the random variable corresponding to x2(t).

[0056] According to the Weiner-Khinchin theorem, the generalized cross-correlation function and its cross-power spectral density are the same as the generalized cross-correlation function of x1(t) and x2(t), if they are Fourier transform pairs of each other.

number

number

[0057] However, j represents the imaginary unit, ω represents the angular frequency, and X1(ω) and X2(ω) represent the Fourier transforms of the high-frequency discharge signals x1(t) and x2(t), respectively.

number

number

[0058] Then, the generalized cross-correlation function with its peak value at the delay is sharpened using weight coefficients.

number

number

[0059] However, j represents the imaginary unit, ω represents the angular frequency, and X1(ω) and X2(ω) represent the Fourier transforms of the high-frequency discharge signals x1(t) and x2(t), respectively.

number

number

[0060] The signal alignment submodule 403 is configured to align the high-frequency discharge signals from the different commercial frequency current transformers based on the extrema of the broad cross-correlation function.

[0061] For example, the broad cross-correlation function

number

[0062] For example, a transformer may have multiple sets of current transformers installed. One of these is arbitrarily selected as a time reference and designated as sensor 1, while the remaining ones are numbered sequentially. The signal alignment process for the entire transformer is shown in Figure 20. The intelligent device 1022 aligns the high-frequency discharge signals from different commercial frequency current transformers to determine polarity.

[0063] In one embodiment, as shown in Figure 5, the intelligent device 1022 is The system further includes an early warning protection module 501 configured to provide early warning or protection for a fault based on the location where the discharge fault occurred.

[0064] Exemplary, as shown in Figure 21, the early alarm protection module 501 of the intelligent device 1022 can provide early alarm or protection for a fault based on the location where the detected discharge fault occurred. If the discharge fault is determined to be an internal fault, the early alarm protection module 501 of the intelligent device 1022 determines whether the discharge fault has reached an alarm threshold based on several parameters, such as a set discharge threshold (e.g., amplitude, pulse count, and rate of increase). If the discharge fault has reached an alarm threshold, it issues an early alarm or protection operation signal. Conversely, if it continues monitoring and determines that the discharge fault is an external fault, the early alarm protection module 501 of the intelligent device 1022 does not operate and continues normal monitoring.

[0065] Furthermore, if a fault occurs in the transformer that is neither an internal nor an external fault, the early alarm protection module 501 of the intelligent device 1022 performs an abnormality count, and after the abnormality count reaches 50, it issues a monitoring abnormality alarm signal.

[0066] In one embodiment, as shown in Figure 6, the signal acquisition module 101 includes a signal shield terminal and a coaxial cable.

[0067] The signal shield terminal is provided in the secondary connection box and is configured to prevent leakage of high-frequency signals.

[0068] For example, the secondary junction box of a commercial frequency current transformer is typically used only to extract commercial frequency current, and its extraction terminals are not specifically designed for high-frequency signals. If used as is, this can cause leakage and crosstalk of high-frequency signals, resulting in significant attenuation of high-frequency currents and poor extraction efficiency. Furthermore, its terminal impedance is matched only to the rated secondary load value required at commercial frequency and cannot meet the 50-ohm load matching required for high-frequency signal acquisition. By providing signal shielding terminals, multiband signals can be extracted more effectively, and synchronous acquisition of commercial frequency and high-frequency signals can be achieved.

[0069] In one embodiment, the housing of the signal shield terminal is an aluminum shield cover, and the outlet is a female bayonet nut connector (BNC), with a connecting bolt provided on one side, thereby effectively preventing leakage of high-frequency signals.

[0070] The coaxial cable connects the signal shield terminal and the frequency divider circuit 1021, and the signal The signal is configured to be transmitted to the frequency divider circuit 1021.

[0071] For example, the cross-sectional area of ​​the central conductor of the coaxial cable is selected by multiplying the rated current of the commercial frequency current transformer by an overcurrent coefficient k, where the overcurrent coefficient k may be set between 1.2 and 1.5.

[0072] In one embodiment, as shown in Figure 6, the signal shield terminal includes a high-frequency terminal 601 and a ground terminal 602. The high-frequency terminal 601 is provided on the common terminal S1 of the secondary connection box. The ground terminal 602 is provided on a terminal other than the common terminal of the secondary connection box.

[0073] For example, a high-frequency terminal 601 provided on the common terminal S1 of the secondary junction box and a ground terminal 602 provided on a terminal other than the common terminal of the secondary junction box jointly realize signal shielding to prevent leakage and crosstalk of high-frequency signals and effectively extract high-frequency discharge signals. The secondary junction box of a commercial frequency current transformer has multiple lead terminals. For example, as shown in Figure 6, in addition to the common terminal S1, the secondary junction box has one lead terminal S2 and another lead terminal S3, and the ground terminal is provided on a lead terminal other than the common terminal based on the transformer parameters.

[0074] In one embodiment, as shown in Figure 7, the high-frequency terminal comprises a copper conductor layer 701, a polyethylene insulating layer 702, a copper ground layer 703, a connecting bolt 704, an impedance matching device 705, and a BNC joint 706.

[0075] As an example, the structure of the high-frequency terminal 601 and the ground terminal 602 is as shown in Figure 7. Both the high-frequency terminal 601 and the ground terminal 602 are provided with female threads inside, and can be directly screwed into the lead terminals in the secondary connection box of the transformer bushing commercial frequency current transformer, making connection to the secondary connection box convenient. Here, the impedance matching device 705 of the high-frequency terminal 601 can ensure the secondary load required for the secondary side of the current transformer to meet its rated value at commercial frequency, and can satisfy output impedance matching of 50 ohms in the high-frequency range. The BNC connector 706 of the high-frequency terminal 601 is a female connector, making connection to the signal line (coaxial cable) convenient.

[0076] In one embodiment, as shown in Figure 6, the signal acquisition module 101 further includes a ground connection lead 603 configured to connect the high-frequency terminal 601 and the ground terminal 602, thereby ensuring a good shielding effect.

[0077] For example, by providing a connecting bolt on one side of both the high-frequency terminal 601 and the ground terminal 602, and connecting the high-frequency terminal 601 and the ground terminal 602 using a ground connection lead 603, a better signal shielding effect can be achieved, ensuring the collection of high-frequency discharge signals, and the ground connection lead 603 can also satisfy the requirement that the secondary side of the current transformer needs to be grounded during operation at commercial frequencies. The ground connection lead 603 may be a metal wire.

[0078] In one embodiment, as shown in Figure 6, the coaxial cable is a BNC coaxial cable 604, connecting the high-frequency terminal 601 and the frequency divider circuit 1021.

[0079] For example, one end of a BNC coaxial cable 604 is connected to a high-frequency terminal 601 provided in a secondary junction box via a BNC connector 706 of the high-frequency terminal 601, and the other end is connected to a frequency divider circuit 1021 of a signal processing module 102, thereby transmitting the multiband signal of the transformer (including the commercial frequency signal and the high-frequency discharge signal) to the frequency divider circuit 1021 to separate the commercial frequency signal from the high-frequency signal. Separation is performed from the discharge signal.

[0080] In one embodiment, as shown in Figure 8, the frequency divider circuit 1021 includes a first low-pass filter 801 and a high-frequency bandpass filter 802 consisting of a second low-pass filter 8021 and a high-pass filter 8022 connected in parallel to the first low-pass filter 801.

[0081] The first low-pass filter 801 is configured to separate the commercial frequency signal from the signal.

[0082] Exemplary, a low-pass filter is an electronic filter primarily configured to remove high-frequency components from a signal while retaining low-frequency components. It is typically used in fields such as audio, video, and communications to filter noise and interference signals, thereby improving signal quality and reliability.

[0083] The main components of a low-pass filter are a capacitor and a resistor. The capacitor blocks the passage of high-frequency signals and allows the passage of low-frequency signals, while the resistor is configured to limit the flow of current and adjust the amplitude of the signal. The cutoff frequency of a low-pass filter is the highest frequency at which the filter will allow a signal to pass; signals above this frequency are filtered out.

[0084] The low-pass filter can be a Butterworth filter or a Bézier filter, among others. The filter order can be selected according to the actual requirements, and is generally controlled to be 2nd to 4th order to achieve a balance between the steepness of the filtering transient and the complexity of the circuit, and the cutoff frequency can be set to 300 Hz. The commercial frequency signal obtained after frequency band separation using the low-pass filter does not need to be processed separately and can be sent directly to a differential protection device, current recorder, or measuring device.

[0085] The high-frequency bandpass filter 802 is connected to the intelligent device 1022 and is configured to separate the high-frequency discharge signal from the signal and transmit the high-frequency discharge signal to the intelligent device 1022.

[0086] For example, the high-pass filter 8022 achieves signal separation within the 3MHz to 30MHz range by connecting a low-pass filter with a cutoff frequency of 30MHz and a high-pass filter 8022 with a cutoff frequency of 3MHz in series. The filters can be Butterworth filters or Bézier filters, etc. The filter order can be selected according to actual requirements and is generally controlled to be 2nd to 4th order to achieve a balance between the steepness of the filtering transient and the complexity of the circuit. The high-frequency discharge signal obtained after frequency band separation using the high-frequency bandpass filter 802, which is formed by connecting the second low-pass filter 8021 and the high-pass filter 8022 in series, is first sent to a local discharge analyzer for processing, then sent to the intelligent device 1022 for analysis, or it may be sent directly to the intelligent device 1022 for analysis.

[0087] The high-frequency discharge signal detection device based on a commercial frequency current transformer according to the present invention comprises a signal acquisition module and a signal processing module. The signal processing module comprises a frequency divider circuit and an intelligent device. The signal acquisition module is provided in the secondary junction box of the commercial frequency current transformer in the transformer, connected to the frequency divider circuit, and configured to acquire the transformer signal and transmit the signal to the frequency divider circuit. The signal includes a commercial frequency signal and a high-frequency discharge signal. The frequency divider circuit is connected to the intelligent device and separates the commercial frequency signal and the high-frequency discharge signal, and the high-frequency The system is configured to transmit high-frequency discharge signals to the intelligent device. The intelligent device is configured to analyze the high-frequency discharge signals, enabling analysis of the transformer's high-frequency discharge signals and local discharge fault positioning. Here, the signal acquisition module allows sensing of high-frequency local discharge currents using only the secondary terminals of the bushing commercial frequency current transformer in related technologies, without requiring the addition of additional sensors or improvements to the end shield of the current transformer. The frequency divider circuit enables synchronous acquisition of multiband signals at the secondary terminals of the commercial frequency current transformer and separation of commercial frequency signals from high-frequency discharge signals. The intelligent device enables polarity discrimination of the high-frequency discharge signals and, by linking them to a set multi-parameter discharge threshold, enables differentiation and early warning of transformer faults. By detecting high-frequency discharge signals using the bushing commercial frequency current transformer in the transformer, simultaneous online local discharge monitoring at the high-voltage terminals, neutral point, etc., of each winding of the transformer is achieved, the detection range effectively covers the transformer, and the detection sensitivity to local discharge signals that may occur inside the transformer can be greatly improved.

[0088] Furthermore, this application provides a method for detecting high-frequency discharge signals based on a commercial frequency current transformer, and by using the high-frequency discharge signal detection device based on a commercial frequency current transformer described in the above embodiment, the analysis of the transformer high-frequency discharge signal can be completed.

[0089] Figure 9 is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. As shown in Figure 9, the high-frequency discharge signal detection method based on a commercial frequency current transformer according to the present invention includes S901 to S903.

[0090] S901: A signal acquisition module acquires signals from a transformer and transmits the signals to a frequency divider circuit. The signals include commercial frequency signals and high-frequency discharge signals.

[0091] Exemplary, a signal acquisition module acquires signals from a transformer. These signals are multiband signals, including commercial frequency signals and high-frequency discharge signals. Simultaneously, the signal acquisition module transmits the multiband signals from the commercial frequency current transformer connection terminals in the transformer to a frequency divider circuit.

[0092] S902: The frequency divider circuit separates the commercial frequency signal and the high-frequency discharge signal, and transmits the high-frequency discharge signal to the intelligent device.

[0093] For example, the frequency divider circuit may separate and process the commercial frequency signal and the local discharge pulse signal separately, and may consist of a low-pass filter and a high-pass filter.

[0094] Figure 10 is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. As shown in Figure 10, S902 includes S1001 to S1002.

[0095] S1001: The first low-pass filter separates the commercial frequency signal from the signal.

[0096] For example, a low-pass filter is an electronic filter primarily configured to remove high-frequency components from a signal while retaining low-frequency components. It is typically used to filter noise and interference signals in fields such as audio, video, and communications, improving signal quality and reliability.

[0097] The main components of a low-pass filter are capacitors and resistors. Capacitors block the passage of high-frequency signals and allow the passage of low-frequency signals, while resistors control the current. It is configured to restrict the flow and adjust the amplitude of the signal. The cutoff frequency of a low-pass filter is the highest frequency at which the filter will allow a signal to pass through; signals above this frequency are filtered out.

[0098] The low-pass filter can be a Butterworth filter or a Bézier filter, among others. The filter order can be selected according to the actual requirements, and is generally controlled to be 2nd to 4th order to achieve a balance between the steepness of the filtering transient and the complexity of the circuit, and the cutoff frequency can be set to 300 Hz. The commercial frequency signal obtained after frequency band separation using the low-pass filter does not need to be processed separately and can be sent directly to a differential protection device, current recorder, or measuring device.

[0099] S1002: The high-frequency bandpass filter separates the high-frequency discharge signal from the signal and transmits the high-frequency discharge signal to the intelligent device.

[0100] For example, a high-pass filter achieves signal separation within the 3MHz to 30MHz range by connecting a low-pass filter with a cutoff frequency of 30MHz and a high-pass filter with a cutoff frequency of 3MHz in series. The filters can be Butterworth filters or Bézier filters, etc. The filter order can be selected according to actual requirements, and is generally controlled to be 2nd to 4th order to achieve a balance between the steepness of the filtering transient and the complexity of the circuit. The high-frequency discharge signal obtained after frequency band separation using a high-frequency bandpass filter formed by connecting a second low-pass filter and a high-pass filter in series is first sent to a local discharge analyzer for processing, then sent to an intelligent device for analysis, or may be sent directly to an intelligent device for analysis.

[0101] S903: The intelligent device analyzes the high-frequency discharge signal.

[0102] For example, an intelligent electronic device (IED) first analyzes the high-frequency discharge signal, that is, it determines the polarity of the high-frequency discharge signal, and based on the result of the polarity determination, distinguishes whether the discharge fault is an internal discharge fault or an external discharge fault.

[0103] Figure 11 is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. As shown in Figure 11, S903 includes S1101 to S1102.

[0104] S1101: The intelligent device determines the polarity of the high-frequency discharge signal.

[0105] For example, transformer discharge faults can be divided into internal and external discharge faults depending on the location of the fault. The polarity of the pulse current in bushing commercial frequency current transformers and neutral-grounded commercial frequency current transformers differs depending on whether the fault is internal or external. Intelligent devices can distinguish between internal and external faults and determine their location. For example, a fault analysis was performed using a single-phase autowinding 500kV (or 500kV or higher) power transformer, and its structure is shown in Figure 16.

[0106] Figure 12 is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. As shown in Figure 12, S1101 includes S1201 to S1204.

[0107] S1201: The intelligent device removes noise from the high-frequency discharge signal.

[0108] For example, if the distance from the fault point to the commercial frequency current transformer is not constant, and high-frequency discharge signals collected by different commercial frequency current transformers have a certain delay and are mixed with a certain amount of noise, then it is necessary to first denoise the high-frequency discharge signals collected by different commercial frequency current transformers. The noise reduction module of an intelligent device can denoise high-frequency discharge signals by methods such as wavelet soft thresholding, empirical mode decomposition, or smoothing noise reduction.

[0109] S1202: The intelligent device aligns high-frequency discharge signals from different commercial frequency current transformers to obtain an alignment result.

[0110] For example, due to the difference in distance from the location of a local discharge fault to different commercial frequency current transformers, there is a certain delay in the received pulse, and if polarity discrimination is performed as is, an anomaly may occur. The noise reduction module of the intelligent device removes noise from the high-frequency discharge signal, and then the alignment module of the intelligent device aligns the high-frequency discharge signals from different commercial frequency current transformers to obtain the alignment result. Here, the alignment of high-frequency discharge signals from different commercial frequency current transformers may be achieved according to phase, or by a generalized cross-correlation (GCC) method, and the present invention is not limited thereto.

[0111] Figure 13 is a flowchart of a high-frequency discharge signal detection method based on a commercial frequency current transformer according to one embodiment of the present invention. As shown in Figure 13, S1202 includes S1301 to S1303.

[0112] S1301: The intelligent device generates weighting coefficients by utilizing the cross-power spectra of high-frequency discharge signals from different commercial frequency current transformers.

[0113] For example, to align and analyze high-frequency discharge signals from different commercial frequency current transformers, an intelligent device can process the high-frequency discharge signals using a broad cross-correlation method. In practice, the effects of reverberation and noise are present, and the broad cross-correlation function...

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[0114] Selection weight coefficients

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[0115] However, ω represents the angular frequency.

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number

number

[0116] S1302: The intelligent device generates a broad cross-correlation function based on the weighting coefficients and the high-frequency discharge signals from the different commercial frequency current transformers.

[0117] For example, the broad cross-correlation function describes the degree of correlation between the values ​​of random high-frequency discharge signals x1(s) and x2(t) at any two times s and t, and is defined as follows:

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[0118] However, X1(s) represents the random variable corresponding to x1(s), and X2(t) represents the random variable corresponding to x2(t).

[0119] According to the Weiner-Khinchin theorem, the generalized cross-correlation function and its cross-power spectral density are the same as the generalized cross-correlation function of x1(t) and x2(t), if they are Fourier transform pairs of each other.

number

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[0120] However, j represents the imaginary unit, ω represents the angular frequency, and X1(ω) and X2(ω) represent the Fourier transforms of the high-frequency discharge signals x1(t) and x2(t), respectively.

number

number

[0121] Then, the generalized cross-correlation function with its peak value at the delay is sharpened using weight coefficients.

number

number

[0122] However, j represents the imaginary unit, ω represents the angular frequency, and X1(ω) and X2(ω) represent the Fourier transforms of the high-frequency discharge signals x1(t) and x2(t), respectively.

number

number

[0123] S1303: The intelligent device aligns the high-frequency discharge signals from the different commercial frequency current transformers based on the extrema of the broad cross-correlation function.

[0124] For example, the broad cross-correlation function

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[0125] For example, a transformer may have multiple sets of current transformers installed. One of these is arbitrarily selected as a time reference and designated as sensor 1, while the remaining ones are numbered sequentially. The signal alignment process for the entire transformer is shown in Figure 20. The intelligent device aligns the high-frequency discharge signals from different commercial frequency current transformers to determine polarity.

[0126] S1203: The intelligent device generates polarity information based on the alignment result and the high-frequency discharge signal.

[0127] For example, an intelligent device alignment module aligns the phases of local discharge pulse signals collected by different commercial frequency current transformers, and then an intelligent device polarity information generation module generates polarity information based on the alignment results and the high-frequency discharge signals. This polarity information represents the distribution of like-polarity or opposite-polarity pulses within one cycle.

[0128] S1204: The intelligent device obtains the result of polarity determination based on the polarity information and a preset threshold.

[0129] For example, the results of polarity determination of a high-frequency discharge signal are divided into two types: same polarity and opposite polarity. The result generation module of an intelligent device can statistically analyze the polarity distribution of pulses within one cycle and distinguish between internal and external faults based on a preset threshold. For example, if the threshold is 75%, if the number of pulses with the same polarity within one cycle exceeds 75%, the result of polarity determination is same polarity, and the fault is determined to be an external discharge fault. If the number of pulses with opposite polarity within one cycle exceeds 75%, the result of polarity determination is opposite polarity, and the fault is determined to be an internal discharge fault.

[0130] S1102: The intelligent device determines the location where the discharge fault occurred based on the result of polarity determination.

[0131] For example, a transformer may have multiple commercial frequency current transformers, allowing for simultaneous monitoring of the current. As shown in Figure 16, when an internal fault occurs, local discharge pulses can be detected on the secondary side of each wound commercial frequency current transformer and the secondary side of the neutral-grounded commercial frequency current transformer, and their polarities are opposite. Conversely, as shown in Figure 17, when an external fault occurs, the fault current is a through-current, and the pulses detected in the wound commercial frequency current transformer and the neutral-grounded commercial frequency current transformer have the same polarity. Based on this characteristic, the intelligent device's positioning module can achieve positioning for discharge faults by detecting the polarity of the high-frequency discharge signal during the transformer's operation. The same-polarity and opposite-polarity pulses are shown in Figure 18.

[0132] In one embodiment, a high-frequency discharge signal detection method based on a commercial frequency current transformer further includes the following after S903.

[0133] The intelligent device provides early warning or protection against a fault based on the location where the discharge fault occurred.

[0134] Exemplary, as shown in Figure 21, the early warning protection module of an intelligent device can provide early warning or protection for a fault based on the location where a determined discharge fault occurs. If the discharge fault is determined to be an internal fault, the early warning protection module of the intelligent device determines whether the discharge fault has reached an alarm threshold based on several parameters, such as a set discharge threshold (e.g., amplitude, pulse count, and rate of increase). If the discharge fault has reached an alarm threshold, it issues an early warning or protection operation signal. Conversely, if it continues monitoring and determines that the discharge fault is an external fault, the early warning protection module of the intelligent device does not operate and continues normal monitoring.

[0135] Furthermore, if a fault occurs in the transformer that is neither internal nor external, the early warning protection module of the intelligent device will perform an anomaly count, and after the anomaly count reaches 50, it will issue a monitoring anomaly alarm signal.

[0136] In the high-frequency discharge signal detection method based on a commercial frequency current transformer according to the present invention, a signal acquisition module collects a signal from the transformer and transmits the signal to a frequency divider circuit, the signal including a commercial frequency signal and a high-frequency discharge signal. The frequency divider circuit separates the commercial frequency signal and the high-frequency discharge signal and transmits the high-frequency discharge signal to an intelligent device. The intelligent device analyzes the high-frequency discharge signal to perform analysis of the high-frequency discharge signal and position the local discharge fault. Here, by collecting the transformer signal and transmitting the signal to the frequency divider circuit, the signal acquisition module can perform sensing of high-frequency local discharge current using only the secondary terminals of a bushing commercial frequency current transformer in related technologies, without requiring the addition of additional sensors or improvements to the end shield of the current transformer. By separating the commercial frequency signal and the high-frequency discharge signal, the frequency divider circuit can achieve synchronous acquisition of multiband signals at the secondary terminals of the commercial frequency current transformer and separation of the commercial frequency signal and the high-frequency discharge signal. The intelligent device analyzes the high-frequency discharge signal to determine its polarity and, by linking it to a set multi-parameter discharge threshold, can distinguish and provide early warnings for transformer faults. The transformer bushing commercial frequency current transformer detects the high-frequency discharge signal to enable simultaneous online local discharge monitoring at the high-voltage terminals, neutral point, etc., of each winding of the transformer. The detection range effectively covers the transformer, and the detection sensitivity to local discharge signals that may occur inside the transformer can be greatly improved.

[0137] In this description, the orientations or positional relationships indicated by terms such as "center," "vertical," "horizontal," "up," "down," "front," "back," "left," "right," "perpendicular," "horizontal," "top," "bottom," "inside," and "outside" are based on the orientations or positional relationships shown in the drawings and are merely for the convenience and simplification of the description of this application. They do not indicate or imply that the specified device or element has a specific orientation or must be configured and operated in a specific orientation, and should not be understood as limitations on this application. Furthermore, terms such as "first," "second," etc., are merely for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of specified technical features. Thus, features limited to "first," "second," etc., may explicitly or implicitly include one or more such features. In this description, unless otherwise stated, "plural" means two or more.

[0138] "One example," "One specific example," "Several examples," "For example," Any description referring to terms such as “example,” “specific example,” or “some examples” means that the specific features, structures, materials, or characteristics described in conjunction with the example are included in at least one example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in an appropriate manner in any one or more examples. The step order relating to each example is for schematic purposes of illustrating the implementation of the present application, and the step order is not limited and may be adjusted as needed.

[0139] In this description, unless otherwise specifically defined and limited, the terms “attach,” “connect,” and “connect” should be understood in a broad sense, for example, a fixed connection, a removable connection, a jointly connected connection, a mechanical connection, an electrical connection, a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. A person skilled in the art will be able to understand the specific meaning of these terms in this application from the specific context.

[0140] The specific examples described above further illustrate the purpose, technical proposal, and beneficial effects of this application. However, these are merely specific examples of this application and are not intended to limit the scope of protection. It should be understood that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should all be included within the scope of protection.

Claims

1. A high-frequency discharge signal detection device based on a commercial frequency current transformer, comprising a signal acquisition module and a signal processing module, The signal processing module comprises a frequency divider circuit and an intelligent device, The signal acquisition module is provided in the secondary junction box of the commercial frequency current transformer in the transformer, connected to the frequency divider circuit, and configured to acquire the transformer signal and transmit the signal, including the commercial frequency signal and the high frequency discharge signal, to the frequency divider circuit. The frequency divider circuit is connected to the intelligent device and configured to separate the commercial frequency signal from the high-frequency discharge signal and to transmit the high-frequency discharge signal to the intelligent device. The intelligent device is configured to analyze the high-frequency discharge signal. A high-frequency discharge signal detection device based on a commercial frequency current transformer.

2. The intelligent device, A polarity discrimination module configured to determine the polarity of the high-frequency discharge signal, A location determination module configured to determine the location where a discharge fault occurred based on the result of polarity determination, comprising: A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 1.

3. The polarity determination module is A noise reduction module configured to remove noise from the aforementioned high-frequency discharge signal, An alignment module configured to align high-frequency discharge signals from different commercial frequency current transformers to obtain an alignment result, A polarity information generation module configured to generate polarity information based on the aforementioned alignment result, The system includes a result generation module configured to obtain polarity determination results based on the aforementioned polarity information and a preset threshold, A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 2.

4. The aforementioned alignment module is A coefficient generation submodule configured to generate weighting coefficients using the mutual power spectra of high-frequency discharge signals from different commercial frequency current transformers, A function generation submodule configured to generate a broad cross-correlation function based on the weighting coefficients and the high-frequency discharge signals from the different commercial frequency current transformers, A signal alignment submodule configured to align high-frequency discharge signals from different commercial frequency current transformers based on the extrema of the broad cross-correlation function, A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 3.

5. The intelligent device, The system further includes an early warning protection module configured to provide early warning or protection for a fault based on the location where the discharge fault occurred. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 2.

6. The aforementioned signal acquisition module is The secondary connection box is provided with a signal shield terminal configured to prevent leakage of high-frequency signals, The system comprises a coaxial cable configured to connect the signal shield terminal and the frequency divider circuit, and to transmit the signal to the frequency divider circuit. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 1.

7. The signal shield terminal comprises a high-frequency terminal provided on the common terminal of the secondary connection box and a ground terminal provided on a terminal other than the common terminal of the secondary connection box. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 6.

8. The high-frequency terminal includes a BNC fitting which is a copper conductor layer, a polyethylene insulating layer, a copper ground layer, a connecting bolt, an impedance matching device, and a bayonet nut connector. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 7.

9. The signal acquisition module further comprises a ground connection lead configured to connect the high-frequency terminal and the ground terminal and to provide signal shielding. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 7.

10. The coaxial cable is a BNC coaxial cable, and connects the high-frequency terminal and the frequency divider circuit. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 7.

11. The frequency divider circuit comprises a first low-pass filter and a high-frequency band-pass filter consisting of a second low-pass filter and a high-pass filter connected in parallel to the first low-pass filter. The first low-pass filter is configured to separate the commercial frequency signal from the signal, The high-frequency bandpass filter is connected to the intelligent device and is configured to separate the high-frequency discharge signal from the signal and transmit the high-frequency discharge signal to the intelligent device. A high-frequency discharge signal detection device based on a commercial frequency current transformer as described in claim 1.

12. A signal acquisition module acquires signals in a transformer and transmits them to a frequency divider circuit, the signals include a commercial frequency signal and a high frequency discharge signal, the signal acquisition module is installed in the secondary junction box of the commercial frequency current transformer in the transformer and is connected to the frequency divider circuit, The frequency divider circuit separates the commercial frequency signal and the high-frequency discharge signal, and transmits the high-frequency discharge signal to the intelligent device. The intelligent device includes analyzing the high-frequency discharge signal, A method for detecting high-frequency discharge signals based on a commercial frequency current transformer.

13. The frequency divider circuit comprises a first low-pass filter and a high-frequency band-pass filter connected in parallel to the first low-pass filter. The frequency divider circuit separates the commercial frequency signal and the high-frequency discharge signal, and transmits the high-frequency discharge signal to the intelligent device. The first low-pass filter separates the commercial frequency signal from the signal, The high-frequency bandpass filter separates the high-frequency discharge signal from the signal and transmits the high-frequency discharge signal to the intelligent device, A method for detecting a high-frequency discharge signal based on a commercial frequency current transformer as described in claim 12.

14. The intelligent device analyzes the high-frequency discharge signal, The intelligent device determines the polarity of the high-frequency discharge signal, The intelligent device determines the location where a discharge fault occurred based on the result of polarity determination, A method for detecting a high-frequency discharge signal based on a commercial frequency current transformer as described in claim 12.

15. The intelligent device determines the polarity of the high-frequency discharge signal, The intelligent device removes noise from the high-frequency discharge signal, The intelligent device aligns high-frequency discharge signals from different commercial frequency current transformers to obtain the alignment result. The intelligent device generates polarity information based on the alignment result, The intelligent device obtains a polarity determination result based on the polarity information and a preset threshold, A method for detecting a high-frequency discharge signal based on a commercial frequency current transformer as described in claim 14.

16. The intelligent device aligns high-frequency discharge signals from different commercial frequency current transformers. The intelligent device generates weighting coefficients by utilizing the mutual power spectra of high-frequency discharge signals from different commercial frequency current transformers. The intelligent device generates a broad cross-correlation function based on the weighting coefficients and the high-frequency discharge signals from the different commercial frequency current transformers, The intelligent device aligns the high-frequency discharge signals from the different commercial frequency current transformers based on the extrema of the broad cross-correlation function, A method for detecting a high-frequency discharge signal based on a commercial frequency current transformer as described in claim 15.

17. The intelligent device further includes providing early warning or protection for a fault based on the location where the discharge fault occurred. A method for detecting a high-frequency discharge signal based on a commercial frequency current transformer as described in claim 14.

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