Single-phase contact tree grounding fault detection method and device

Abstract

The invention provides a single-phase contact tree grounding fault detection method. The method comprises the following steps: acquiring initial zero-sequence voltage data in a power distribution network; the waveform amplitude of the initial zero-sequence voltage data is screened, and target zero-sequence voltage with the waveform amplitude abrupt change is obtained; judging whether the target zero-sequence voltage has a beat frequency characteristic or not, if so, determining that the target zero-sequence voltage has a first fault, and otherwise, entering the next step; and separating the target zero-sequence voltage by using a fixed point algorithm, judging whether the separated zero-sequence voltage has a beat frequency characteristic or not, and if so, determining that the target zero-sequence voltage has a second fault. The invention also provides a single-phase contact tree grounding fault detection device. According to the invention, single-phase contact tree grounding fault detection is carried out based on the fixed point algorithm FastICA, the identification speed is improved while the identification capability is ensured, and the detection efficiency can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of signal processing and high voltage power grid, and more specifically, the invention relates to a single-phase tree-contact grounding fault detection method and device. Background Art

[0002] Single-phase tree-touching grounding fault is a common fault in distribution network, which is easy to cause damage to forests and other places. Therefore, it is of great significance to design an algorithm that can monitor the single-phase tree-touching grounding fault in real time. At present, the design of this detection algorithm faces some challenges. First, the single-phase tree-touching grounding fault is a single-phase high-resistance grounding fault, and the current distribution network often adopts the neutral point grounding method through the arc suppression coil. However, since the size of the arc suppression coil is generally selected in an overcompensation manner, the amplitude of the commonly used detection quantity is low when a single-phase high-resistance grounding fault occurs (the zero-sequence voltage may be less than 15% of the phase voltage, and the fault current may be less than 1A), the fault characteristic quantity is not obvious, and it is easily affected by three-phase imbalance, noise, arc distortion, etc. For the single-phase tree-touching grounding fault, its transition resistance is also relatively large in the single-phase high-resistance grounding fault, which makes the amplitude of the commonly used detection quantity weaker than other types of single-phase high-resistance grounding faults. Therefore, the traditional fault detection based on amplitude and polarity is difficult to apply, and the traditional protection device can hardly have effective action. Therefore, it is necessary to design a detection method for single-phase tree-touching grounding fault. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the above-mentioned shortcomings, the main purpose of the present invention is to provide a single-phase tree-contact grounding fault detection method and device.

[0005] (II) Technical solution

[0006] In order to achieve the above-mentioned purpose, the present invention provides a single-phase tree-contact grounding fault detection method, comprising: step S1, collecting initial zero-sequence voltage data in the distribution network; step S2, screening the waveform amplitude of the initial zero-sequence voltage data to obtain a target zero-sequence voltage with a sudden change in waveform amplitude; step S3, judging whether the target zero-sequence voltage has a beat frequency feature, and if so, determining that the target zero-sequence voltage has a first fault; otherwise, entering the following step S4; step S4, separating the target zero-sequence voltage using a fixed point algorithm, judging whether the separated zero-sequence voltage has a beat frequency feature, and if so, determining that the target zero-sequence voltage has a second fault.

[0007] In the above scheme, the initial zero-sequence voltage data includes normal data and fault data, and step S1 includes: reading the parameters of the three-phase electricity in the distribution network in parallel through the voltage transformer to obtain the initial zero-sequence voltage data; or reading the parameters of the neutral point of the three-phase electricity through the voltage transformer to obtain the initial zero-sequence voltage data.

[0008] In the above scheme, step S3 includes: step S31, performing a fast Fourier transform on the target zero-sequence voltage to obtain a first frequency domain diagram of the target zero-sequence voltage; step S32, determining that the target zero-sequence voltage has a beat frequency characteristic when it is determined that there are multiple signal peaks within a preset neighborhood range of the industrial frequency in the first frequency domain diagram, and the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than a preset difference range.

[0009] In the above scheme, step S4 includes: step S41: fast Fourier transform the target zero-sequence voltage and read the power frequency ω0; step S42: construct a signal observation matrix according to the power frequency ω0, and solve the observation matrix using a fixed point algorithm to obtain a mixing matrix A; step S43: use the mixing matrix A to separate the power frequency signal in the target zero-sequence voltage to obtain a separated zero-sequence voltage; step S44: fast Fourier transform the separated zero-sequence voltage to obtain a second frequency domain diagram of the separated zero-sequence voltage; step S45: determine whether the separated zero-sequence voltage has a beat frequency feature based on the second frequency domain diagram.

[0010] In the above scheme, step S45 includes determining that the separated zero-sequence voltage has a beat frequency characteristic when the following three conditions are met: there are multiple signal peaks within a preset neighborhood range of the power frequency in the second frequency domain diagram; the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than the preset difference range; the amplitude of the separated zero-sequence voltage is not less than 5% of the target zero-sequence voltage waveform amplitude.

[0011] In the above scheme, the reading of the power frequency in step S41 includes: adding 0 after the target zero-sequence voltage data, performing fast Fourier transform on the target zero-sequence voltage data after adding 0, and reading the power frequency ω0.

[0012] In the above scheme, the signal observation matrix of step S42 is expressed as:

[0013] X={U o (t), sin(ω0t), cos(ω0t)}

[0014] Among them, U o (t) represents the target zero-sequence voltage; sin(ω0t) and cos(ω0t) represent the sine signal of the power frequency ω0 and the cosine signal of the power frequency ω0, respectively; X represents the signal observation matrix.

[0015] The present invention also provides a single-phase tree-contact grounding fault detection device, comprising: an initial zero-sequence voltage reading module, used to read the initial zero-sequence voltage data in the distribution network; a target zero-sequence voltage screening module, used to screen the zero-sequence voltage with a sudden change in waveform amplitude in the initial zero-sequence voltage data; a first fault judgment module, used to judge whether the target zero-sequence voltage has a beat frequency feature, if so, it is determined that the target zero-sequence voltage has a first fault; otherwise, enter the following second fault judgment module; the second fault judgment module is used to separate the target zero-sequence voltage using a fixed point algorithm, and judge whether the separated zero-sequence voltage has a beat frequency feature, if so, it is determined that the target zero-sequence voltage has a second fault.

[0016] Furthermore, the first fault judgment module also includes: a first frequency domain diagram determination unit, used to perform a fast Fourier transform on the target zero-sequence voltage to obtain a first frequency domain diagram of the target zero-sequence voltage; a first fault judgment unit, used to determine that the target zero-sequence voltage has a beat frequency characteristic when it is determined that there are multiple signal peaks within a preset neighborhood range of the power frequency in the first frequency domain diagram, and the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than a preset difference range.

[0017] Furthermore, the second fault judgment module includes: an industrial frequency reading unit, which is used to perform a fast Fourier transform on the target zero-sequence voltage and read the industrial frequency ω0; a mixed matrix determination unit, which is used to construct an industrial frequency ω0 signal observation matrix, and solve the observation matrix using a fixed point algorithm to obtain a mixed matrix A; a signal separation unit, which uses the mixed matrix A to separate the industrial frequency signal in the target zero-sequence voltage to obtain a separated zero-sequence voltage; a second frequency domain graph determination unit, which performs a fast Fourier transform on the separated zero-sequence voltage to obtain a second frequency domain graph of the separated zero-sequence voltage; and a second fault judgment unit, which determines whether the separated zero-sequence voltage has a beat frequency feature based on the second frequency domain graph, and if so, determines that the target zero-sequence voltage has a second fault.

[0018] (III) Beneficial effects

[0019] Compared with the prior art, the beneficial effects of the present invention include:

[0020] (1) This detection method can effectively distinguish the normal state from the fault state.

[0021] (2) This detection method effectively improves the detection efficiency. While ensuring the recognition capability, it can accurately distinguish the normal state from the fault state and improve the detection speed of the algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The flowchart of the single-phase tree-contact grounding fault detection method according to an embodiment of the present invention is schematically shown.

[0023] Figure 2 A flowchart of a first fault judgment according to an embodiment of the present invention is schematically shown.

[0024] Figure 3 A flowchart of a second fault judgment according to an embodiment of the present invention is schematically shown.

[0025] Figure 4 A block diagram of a single-phase tree-touching grounding fault detection device according to an embodiment of the present invention is schematically shown.

[0026] Figure 5 The block diagram schematically shows a composition of a first fault judgment module according to an embodiment of the present invention.

[0027] Figure 6 The following schematically shows a block diagram of the composition of the second fault judgment module according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Please refer to Figure 1 , Figure 1 The flowchart of the single-phase tree-contact grounding fault detection method according to an embodiment of the present invention is schematically shown.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a single-phase tree-contact grounding fault detection method, comprising:

[0031] Step S1, collecting initial zero-sequence voltage data in the distribution network;

[0032] Step S2, screening the waveform amplitude of the initial zero-sequence voltage data to obtain a target zero-sequence voltage with a sudden change in waveform amplitude;

[0033] Step S3, judging whether the target zero-sequence voltage has a beat frequency feature, if so, determining that the target zero-sequence voltage has a first fault; otherwise, proceeding to the following step S4;

[0034] Step S4, using a fixed point algorithm to separate the target zero-sequence voltage, and determining whether the separated zero-sequence voltage has a beat frequency feature, and if so, determining that the target zero-sequence voltage has a second fault.

[0035] The initial zero-sequence voltage data includes normal data and fault data, and step S1 includes:

[0036] Voltage transformers are installed along the transmission lines, and the parameters of the three-phase electricity in the distribution network are read in parallel through the voltage transformers to obtain initial zero-sequence voltage data; or the parameters of the neutral point of the three-phase electricity are read through the voltage transformers to obtain initial zero-sequence voltage data.

[0037] In this embodiment, please refer to Figure 2 , Figure 2 A flowchart of a first fault judgment according to an embodiment of the present invention is schematically shown.

[0038] The first fault judgment step S3 includes:

[0039] Step S31, performing a fast Fourier transform on the target zero-sequence voltage to obtain a first frequency domain diagram of the target zero-sequence voltage;

[0040] Step S32, when it is determined that there are multiple signal peaks in the preset neighborhood range of the power frequency in the first frequency domain diagram, and the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than the preset difference range, it is determined that the target zero-sequence voltage has a beat frequency feature.

[0041] In this embodiment, please refer to Figure 3 , Figure 3 A flowchart of a second fault judgment according to an embodiment of the present invention is schematically shown.

[0042] The second fault judgment step S4 includes:

[0043] Step S41: Perform fast Fourier transform on the target zero-sequence voltage and read the power frequency ω0;

[0044] Step S42: construct a signal measurement matrix according to the power frequency ω0, and solve the measurement matrix using a fixed point algorithm to obtain a mixing matrix A;

[0045] Step S43: using the mixing matrix A to separate the power frequency signal in the target zero-sequence voltage to obtain a separated zero-sequence voltage;

[0046] Step S44: performing fast Fourier transform on the separated zero-sequence voltage to obtain a second frequency domain diagram of the separated zero-sequence voltage;

[0047] Step S45: judging whether the separated zero-sequence voltage has a beat frequency feature according to the second frequency domain diagram.

[0048] Specifically, step S45 includes determining that the separated zero-sequence voltage has a beat frequency characteristic when the following three conditions are met:

[0049] There are multiple signal peaks within the preset neighborhood range of the power frequency in the second frequency domain diagram; the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than the preset difference range; the amplitude of the separated zero-sequence voltage is not less than 5% of the target zero-sequence voltage waveform amplitude.

[0050] Specifically, the step S41 of performing fast Fourier transform on the target zero-sequence voltage and reading the power frequency ω0 includes:

[0051] The target zero-sequence voltage data is processed by adding 0 after the end, and then the target zero-sequence voltage data after adding 0 is subjected to fast Fourier transform to read the power frequency ω0.

[0052] For example, the sampled data is stored in Excel, and the sampling amplitude is 1, 2, 3, 4, 5. 0 is added after the floating-point data to get 1, 2, 3, 4, 5, 0, 0, 0, 0 again, and then Fourier transform is performed.

[0053] For example, according to the power frequency ω0, a signal measurement matrix is ​​constructed, and the measurement matrix is ​​solved using a fixed point algorithm to obtain the mixing matrix A. The signal measurement matrix can be expressed as:

[0054] X={U o (t), sin(ω0t), cos(ω0t)}

[0055] Among them, U o (t) represents the target zero-sequence voltage; sin(ω0t) and cos(ω0t) represent the sine signal of the power frequency ω0 and the cosine signal of the power frequency ω0, respectively; X represents the signal observation matrix.

[0056] When the zero-sequence voltage of the second fault is detected, the final result is output for corresponding processing such as tripping and dispatching personnel for inspection.

[0057] The present invention also provides a single-phase tree-contact grounding fault detection device. The device provided by an embodiment of the present invention is described below. The device described below corresponds to the method described above.

[0058] Figure 4 A block diagram of a single-phase tree-touching grounding fault detection device according to an embodiment of the present invention is schematically shown.

[0059] like Figure 4 As shown, the single-phase tree-contact grounding fault detection device 400 may include, for example:

[0060] An initial zero-sequence voltage reading module 401 is used to read initial zero-sequence voltage data in the distribution network;

[0061] The target zero-sequence voltage screening module 402 is used to screen the zero-sequence voltage with sudden change in waveform amplitude in the initial zero-sequence voltage data;

[0062] The first fault judgment module 403 is used to judge whether the target zero-sequence voltage has a beat frequency feature. If yes, it is determined that the target zero-sequence voltage has a first fault; otherwise, the process proceeds to the following second fault judgment module;

[0063] The second fault judgment module 404 is used to separate the target zero-sequence voltage by using a fixed point algorithm, and judge whether the separated zero-sequence voltage has a beat frequency feature. If so, it is determined that the target zero-sequence voltage has a second fault.

[0064] Figure 5 The block diagram schematically shows the composition of the first fault judgment module 403 according to an embodiment of the present invention.

[0065] like Figure 5 As shown, the first fault judgment module 403 may include, for example: a first frequency domain diagram determining unit 501 and a first fault judgment unit 502;

[0066] The first frequency domain map determining unit 501 is used to perform a fast Fourier transform on the target zero-sequence voltage to obtain a first frequency domain map of the target zero-sequence voltage;

[0067] The first fault judgment unit 502 is used to determine that the target zero-sequence voltage has a beat frequency feature when it is determined that there are multiple signal peaks in a preset neighborhood range of the power frequency in the first frequency domain diagram, and the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than a preset difference range.

[0068] Figure 6 The block diagram schematically shows the composition of the second fault judgment module 404 according to an embodiment of the present invention.

[0069] like Figure 6 As shown, the second fault judgment module 404 may include: an industrial frequency reading unit 601, a mixing matrix determining unit 602, a signal separation unit 603, a second frequency domain diagram determining unit 604 and a second fault judgment unit 605;

[0070] The power frequency reading unit 601 is used to perform fast Fourier transform on the target zero-sequence voltage and read the power frequency ω0;

[0071] The mixing matrix determination unit 602 is used to construct the power frequency ω0 signal observation matrix, and solve the observation matrix using a fixed point algorithm to obtain a mixing matrix A;

[0072] The signal separation unit 603 uses a mixing matrix A to separate the power frequency signal from the target zero-sequence voltage to obtain a separated zero-sequence voltage;

[0073] The second frequency domain map determining unit 604 performs fast Fourier transform on the separated zero-sequence voltage to obtain a second frequency domain map of the separated zero-sequence voltage;

[0074] The second fault judgment unit 605 judges whether the separated zero-sequence voltage has a beat frequency feature according to the second frequency domain diagram, and if so, determines that the target zero-sequence voltage has a second fault.

[0075] It should be noted that the implementation method of the device part is similar to the implementation method of the method part, and the technical effects achieved are also similar. For specific details, please refer to the above-mentioned method implementation method part, which will not be repeated here.

[0076] According to the embodiments of the present invention, any multiple or at least part of the functions of any multiple of the modules can be implemented in one module. According to the embodiments of the present invention, any one or more of the modules can be split into multiple modules for implementation. According to the embodiments of the present invention, any one or more of the modules can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application-specific integrated circuit (ASIC), or can be implemented by hardware or firmware of any other reasonable way of integrating or packaging the circuit, or implemented in any one of the three implementation methods of software, hardware and firmware or in any appropriate combination of any of them. Alternatively, according to the embodiments of the present invention, one or more of the modules can be at least partially implemented as a computer program module, and when the computer program module is run, the corresponding function can be executed.

[0077] In summary, the present invention provides a single-phase tree-contact grounding fault detection method and device. This detection method first detects whether the zero-sequence voltage amplitude has changed to perform a preliminary fault signal selection, and then performs a first fault judgment by whether the zero-sequence voltage has a beat frequency feature. If it is impossible to determine that there is an obvious fault, the unbalanced component of the distribution network is removed in combination with FastICA (fixed point algorithm) to perform a second fault judgment. In order to improve the recognition speed of the algorithm, this detection method can effectively improve the detection efficiency, and while ensuring the recognition ability, it can accurately distinguish the normal state from the fault state, thereby improving the detection speed of the algorithm.

[0078] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, functions and operations of the system, method and computer program product according to various embodiments of the present invention. In this regard, each box in the flow chart or block diagram can represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flow chart, and the combination of the boxes in the block diagram or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0079] It will be appreciated by those skilled in the art that, although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, it will be appreciated by those skilled in the art that, without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents, various changes in form and detail may be made to the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

[0080] Similarly, it should be understood that in order to streamline the present invention and aid in understanding one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: that the claimed invention requires more features than the features explicitly recited in each claim. More specifically, as reflected in the preceding claims, the disclosed aspects are less than all the features of the single embodiment disclosed previously. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present invention.

[0081] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A single-phase tree-to-ground fault detection method, characterized in that: include: Step S1, collecting initial zero-sequence voltage data in the distribution network; Step S2, screening the waveform amplitude of the initial zero-sequence voltage data to obtain a target zero-sequence voltage with a sudden change in waveform amplitude; Step S3, determining whether the target zero-sequence voltage has a beat frequency feature, and if so, determining that the target zero-sequence voltage has a first fault; Otherwise, proceed to the following step S4; Step S4, using a fixed point algorithm to separate the target zero-sequence voltage, and determining whether the separated zero-sequence voltage has a beat frequency feature, and if so, determining that the target zero-sequence voltage has a second fault.

2. The single-phase tree-contact grounding fault detection method according to claim 1, characterized in that: The initial zero-sequence voltage data includes normal data and fault data, and the step S1 includes: Reading the parameters of the three-phase electricity in the distribution network through voltage transformers in parallel to obtain the initial zero-sequence voltage data; or The parameters of the three-phase electrical neutral point are read through the voltage transformer to obtain the initial zero-sequence voltage data.

3. The single-phase tree-contact grounding fault detection method according to claim 1, characterized in that: The step S3 comprises: Step S31, performing a fast Fourier transform on the target zero-sequence voltage to obtain a first frequency domain diagram of the target zero-sequence voltage; Step S32, when it is determined that there are multiple signal peaks in the preset neighborhood range of the power frequency in the first frequency domain diagram, and the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than the preset difference range, it is determined that the target zero-sequence voltage has a beat frequency feature.

4. The single-phase tree-contact grounding fault detection method according to claim 1, characterized in that: The step S4 comprises: Step S41: Perform fast Fourier transform on the target zero-sequence voltage and read the power frequency ω0; Step S42: constructing a signal measurement matrix according to the power frequency ω0, and solving the measurement matrix using the fixed point algorithm to obtain a mixing matrix A; Step S43: using the hybrid matrix A to separate the power frequency signal in the target zero-sequence voltage to obtain a separated zero-sequence voltage; Step S44: performing fast Fourier transform on the separated zero-sequence voltage to obtain a second frequency domain graph of the separated zero-sequence voltage; Step S45: judging whether the separated zero-sequence voltage has a beat frequency feature according to the second frequency domain diagram.

5. The single-phase tree-contact grounding fault detection method according to claim 4 is characterized in that: The step S45 includes determining that the separated zero-sequence voltage has a beat frequency feature when the following three conditions are met: There are multiple signal peaks within a preset neighborhood range of the power frequency in the second frequency domain graph; The difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than a preset difference range; The amplitude of the separated zero-sequence voltage is not less than 5% of the target zero-sequence voltage waveform amplitude.

6. The single-phase tree-contact grounding fault detection method according to claim 4, characterized in that: The reading of the power frequency in step S41 includes: The target zero-sequence voltage data is processed by adding 0 after the end, and then the target zero-sequence voltage data after adding 0 is subjected to fast Fourier transform to read the power frequency ω0.

7. The single-phase tree-contact grounding fault detection method according to claim 4, characterized in that: The signal observation matrix of step S42 is expressed as: X={U o (t),sin(ω0t),cos(ω0t)} Among them, U o (t) represents the target zero-sequence voltage; sin(ω0t) and cos(ω0t) represent the sine signal of the power frequency ω0 and the cosine signal of the power frequency ω0, respectively; X represents the signal observation matrix.

8. A single-phase tree-contact grounding fault detection device, characterized in that: include: An initial zero-sequence voltage reading module is used to read the initial zero-sequence voltage data in the distribution network; A target zero-sequence voltage screening module is used to screen the zero-sequence voltage with a sudden change in waveform amplitude in the initial zero-sequence voltage data; A first fault judgment module is used to judge whether the target zero-sequence voltage has a beat frequency feature, and if so, determine that the target zero-sequence voltage has a first fault; otherwise, enter the following second fault judgment module; The second fault judgment module is used to separate the target zero-sequence voltage by using a fixed point algorithm, and judge whether the separated zero-sequence voltage has a beat frequency feature. If so, it is determined that the target zero-sequence voltage has a second fault.

9. The single-phase tree-contact grounding fault detection device according to claim 8, characterized in that: The first fault judgment module also includes: A first frequency domain map determining unit, configured to perform a fast Fourier transform on the target zero-sequence voltage to obtain a first frequency domain map of the target zero-sequence voltage; The first fault judgment unit is used to determine that the target zero-sequence voltage has a beat frequency feature when it is determined that there are multiple signal peaks within a preset neighborhood range of the power frequency in the first frequency domain diagram, and the difference between the multiple signal peaks and the target zero-sequence voltage waveform amplitude is less than a preset difference range.

10. The single-phase tree-contact grounding fault detection device according to claim 8, characterized in that: The second fault judgment module includes: A power frequency reading unit, used for performing a fast Fourier transform on the target zero-sequence voltage to read the power frequency ω0; A mixing matrix determination unit is used to construct an industrial frequency ω0 signal observation matrix, and solve the observation matrix using a fixed point algorithm to obtain a mixing matrix A; A signal separation unit, using the mixing matrix A, separates the power frequency signal in the target zero-sequence voltage to obtain a separated zero-sequence voltage; a second frequency domain map determining unit, performing a fast Fourier transform on the separated zero-sequence voltage to obtain a second frequency domain map of the separated zero-sequence voltage; The second fault judgment unit judges whether the separated zero-sequence voltage has a beat frequency feature according to the second frequency domain diagram, and if so, determines that the target zero-sequence voltage has a second fault.

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