A low voltage line leakage current fault detection device

Abstract

The application relates to a low-voltage line leakage current fault detection device, which comprises a first current collector, a second current collector and a detection terminal; the first current collector is wirelessly connected with the detection terminal and is configured to collect overhead long-distance multi-branch current and multi-branch current of busbars, narrow spaces or thick-wire lines; the second current collector is wiredly connected with the detection terminal and is configured to collect cable branch box multi-branch current; the detection terminal performs low-voltage line leakage current fault detection based on current data of the first current collector and the second current collector. Compared with the prior art, the application adopts two different current collectors to measure leakage current online, and solves the measurement problem of leakage current on low-voltage lines in different environments such as overhead lines and cable branch boxes under the condition of no power-off.

Description

Technical Field

[0001] This invention relates to the field of low-voltage line leakage current measurement, and in particular to a low-voltage line leakage current fault detection device. Background Technology

[0002] Leakage current in low-voltage distribution lines increases power loss and creates potential faults, causing losses not only to power supply companies but also posing serious risks to users' electricity use and safety, leading to electrical fires, electric shocks, and other accidents. Therefore, accurate and efficient location of leakage current in distribution lines is crucial.

[0003] However, low-voltage leakage transformer areas have dispersed users, long power supply paths, and numerous branches. The conventional method for locating leakage faults in transformer areas involves shutting down each line one by one to identify the faulty low-voltage circuit; then climbing poles to disconnect and reconnect branches to pinpoint the faulty branch; and finally shutting down power to each household on the branch and inspecting the branch lines to identify the faulty user or the specific low-voltage line fault. This method is difficult to pinpoint, requires multiple people working together, involves multiple power outages and restorations, and necessitates repair personnel climbing poles to disconnect and reconnect components, resulting in a large workload, low efficiency, and increased risks of falls from heights, pole collapses, and electric shocks. Furthermore, in 400V three-phase four-wire overhead power supply systems, the large spacing between the four conductors makes it impossible to use clamp meters for leakage current measurement. In the prior art, Chinese invention patent application CN201811545653.2 discloses a novel leakage current measuring device and method. It utilizes the principle of current transformer to convert the original line into an equivalent secondary circuit of a current transformer that can be fitted into a measuring current transformer, thereby realizing the measurement of leakage current of low-voltage 400V overhead lines. This solves the problem that it is difficult to install leakage current transformers on low-voltage 400V overhead lines due to the large phase spacing. However, the accuracy of the equivalent conversion current data is not high. Due to the characteristics of the transformer itself and the influence of the primary and secondary circuits on site, the actual test data will have deviations. At the same time, it cannot accurately detect the leakage fault point in the transformer area. Chinese invention patent application CN201910162105.X discloses a tool for measuring leakage current in rural low-voltage power supply areas. To facilitate the troubleshooting of leakage faults in low-voltage overhead lines, the proposed tool connects one end of a current line to a clamp-on current transformer, and the other end extends to the ground and connects to a leakage current measuring instrument. However, the excessively long lead wire makes on-site operation inconvenient and cumbersome, and also results in low measurement accuracy. Leakage faults are even more difficult to detect in three-phase five-wire user lines, making it impossible to calculate leakage current for three-phase five-wire systems. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a low-voltage line leakage current fault detection device.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A low-voltage line leakage current fault detection device includes a first current acquisition unit, a second current acquisition unit, and a detection terminal;

[0007] The first current acquisition device is wirelessly connected to the detection terminal and is configured to acquire overhead long-distance multi-branch current, as well as busbar, narrow space or thick wire diameter line multi-branch current;

[0008] The second current acquisition device is wired to the detection terminal and is configured to acquire the current of multiple branches in the cable branch box;

[0009] The detection terminal performs low-voltage line leakage current fault detection based on the current data from the first current collector and the second current collector.

[0010] Preferably, the first current collector is divided into an A-phase first current collector, a B-phase first current collector, a C-phase first current collector, and an N-phase first current collector, which collect current data for phases A, B, C, and N, respectively.

[0011] The first current acquisition device includes: a first current input circuit, a first measurement processor, a first wireless module, a first GPS module, and a power supply circuit. The first current input circuit is connected to the first measurement processor and is used to acquire current. The first measurement processor is used to sample the current to obtain current data. The first wireless module is connected to the first measurement processor and is used to upload the current data to the detection terminal via wireless communication. The first GPS module is connected to the first measurement processor and is used to provide synchronization clock information and geographical location information. The power supply circuit is used to provide operating power for the first current acquisition device.

[0012] Preferably, when the first current collector collects overhead long-distance multi-branch current, the first current input circuit includes a detachable wireless synchronous measurement current clamp; when the first current collector collects busbar, narrow space, or line multi-branch current with thicker wire diameter, the first current input circuit includes a low-voltage flexible high-current clamp.

[0013] Preferably, the second current acquisition device includes: a 5-channel current input circuit, a second measurement processor, and a second wired module; the 5-channel current input circuit is connected to the second measurement processor and is used to acquire 5 current channels A, B, C, N, and PE; the second measurement processor is used to sample the 5 current channels to obtain current data; and the second wired module is connected to the second measurement processor and is used to upload the current data to the detection terminal via wired communication.

[0014] Preferably, the 5-channel current input circuit includes wired current clamps corresponding to channels A, B, C, N, and PE.

[0015] Preferably, the wired module further includes a power lead, which supplies power from the detection terminal to the second current collector.

[0016] Preferably, the detection terminal includes a third measurement processor, a human-computer interaction processor, a human-computer interaction input / output module, a storage module, a third GPS module, a third wireless module, a third wired module, and a power supply module;

[0017] The third measurement processor is used to detect low-voltage line leakage current faults based on the current data from the first and second current collectors. The third wireless module is connected to the third measurement processor and is used to acquire the current signal from the first current collector and send it to the third measurement processor. The third wired module is connected to the third measurement processor and is used to acquire the current signal from the second current collector and send it to the third measurement processor. The third GPS module is connected to the third measurement processor and is used to provide synchronization clock information and geographical location information. The power module is used to provide working power for the detection terminal. The third measurement processor is connected to a human-machine interaction processor, which is connected to a human-machine interaction input / output module and a storage module for displaying and saving the detection results.

[0018] Preferably, the detection terminal calculates the leakage current of low-voltage lines in overhead line environments based on the current data from the first current collector, calculates the leakage current of low-voltage lines in busbar, narrow space, or thicker wire diameter environments, and calculates the leakage current of low-voltage lines in cable branch box environments based on the current data from the second current collector; and completes the low-voltage line leakage current fault detection based on the value of the leakage current.

[0019] Preferably, the process for calculating the leakage current of a three-phase four-wire line is as follows:

[0020] Step 1-1: Obtain the A, B, C, and N phase vector current signals through the first or second current acquisition device:

[0021] Steps 1-2: Using digital signal processing technology to... FFT decomposition is performed, decomposing the signal into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components. The vector current signal of a certain phase is decomposed as follows:

[0022]

[0023] in, This is a vector current signal, where i0 is the DC component of the current and ω1 is the fundamental frequency. The fundamental component phase is represented by m, and the harmonic order is represented by i. n , This represents the amplitude and phase of the m-th harmonic current, and the frequency ω of the m-th harmonic. m It is an integer multiple of the fundamental frequency ω1;

[0024] Steps 1-3, for The fundamental and harmonic components are decomposed into coordinates to obtain the x-coordinate decomposed current I. mx Decomposing the current I using the y-coordinate my The decomposition of one component of a certain phase vector current signal is as follows:

[0025]

[0026]

[0027] in, The m-th current, that is, the m-th component of a certain phase vector current signal, corresponds to... This represents the phase of the m-th harmonic current;

[0028] Steps 1-4: Calculate the amplitude I of the leakage current. L and phase φ L :

[0029]

[0030]

[0031] Among them, I Lmx I is the sum of the amplitude components of the m vector currents along the x-axis after two decompositions of the four-phase current signal. Lmy I is the sum of the amplitude components of the m-th vector current in the y-axis after two decompositions of the four-phase current signal; L1x I is the sum of the amplitude components of the fundamental wave on the x-axis after two decompositions of the four-phase current signal. L1y It is the sum of the amplitude components of the fundamental wave on the y-axis after two decompositions of the four-phase current signal.

[0032] Preferably, the process for calculating the leakage current of a three-phase five-wire line is as follows:

[0033] Step 1-1: Obtain the vector current signals of phases A, B, C, N, and PE through the second current acquisition device:

[0034] Step 1-2: Set the current threshold δ PE ,like Then proceed to steps 1-6; otherwise, execute steps 1-3.

[0035] Steps 1-3: Using digital signal processing techniques to... FFT decomposition is performed, decomposing the signal into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components. The vector current signal of a certain phase is decomposed as follows:

[0036]

[0037] in, This is a vector current signal, where i0 is the DC component of the current and ω1 is the fundamental frequency. The fundamental component phase is represented by m, and the harmonic order is represented by i. n , This represents the amplitude and phase of the m-th harmonic current, and the frequency ω of the m-th harmonic. m It is an integer multiple of the fundamental frequency ω1;

[0038] Steps 1-4, for The fundamental and harmonic components are decomposed into coordinates to obtain the x-coordinate decomposed current I. mx Decomposing the current I using the y-coordinate my The decomposition of one component of a certain phase vector current signal is as follows:

[0039]

[0040]

[0041] in, The m-th current, that is, the m-th component of a certain phase vector current signal, corresponds to... This represents the phase of the m-th harmonic current;

[0042] Steps 1-5: Calculate the amplitude I of the leakage current. L and phase φ L :

[0043]

[0044]

[0045] Among them, I Lmx I is the sum of the amplitude components of the m vector currents along the x-axis after two decompositions of the four-phase current signal. Lmy I is the sum of the amplitude components of the m-th vector current in the y-axis after two decompositions of the four-phase current signal; L1x I is the sum of the amplitude components of the fundamental wave on the x-axis after two decompositions of the four-phase current signal. L1y It is the sum of the amplitude components of the fundamental wave on the y-axis after two decompositions of the four-phase current signal;

[0046] Steps 1-6: Calculate the amplitude and phase of the PE phase current:

[0047] Step 1-6-1: Utilize digital signal processing technology to... Performing FFT decomposition, the component is decomposed into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components, yielding:

[0048]

[0049] Step 1-6-2, for The fundamental and harmonic components are decomposed into coordinates to obtain the x-coordinate decomposed current I of the PE phase current signal. PEmx Decompose the current I in the y-coordinate of the phase current signal of the PE phase. PEmy :

[0050] I PEmx =I PEm ·cosφ PEm

[0051] I PEmy =I PEm ·sinφ PEm

[0052] Among them, I PEm The m-th order current of the PE phase is the m-th component of the PE phase vector current signal, corresponding to φ. PEm This represents the phase of the m-th harmonic current;

[0053] Step 1-6-3: Calculate the amplitude of the PE phase current I PE and phase φ PE :

[0054]

[0055]

[0056] Among them, I PEmx I represents the amplitude components of the m-th vector current along the x-axis after two decompositions of the PE phase current signal. PEmy The amplitude components of the m-th vector current in the y-axis after two decompositions of the PE phase current signal; I PE1x I represents the amplitude component of the fundamental frequency on the x-axis after two decompositions of the PE phase current signal. PE1y The amplitude component of the fundamental wave on the y-axis after two decompositions of the PE phase current signal.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) Two different current acquisition devices are used to measure leakage current online, so as to solve the problem of measuring leakage current on low-voltage lines in different environments such as overhead lines and cable branch boxes without power interruption.

[0059] (2) For overhead lines, a detachable wireless synchronous current measuring clamp is used, which eliminates the need for inspectors to climb poles, saving manpower and resources, enabling rapid measurement, and improving work efficiency and quality. For busbars, narrow spaces, or line branch currents with thicker wire diameters, a low-voltage flexible high-current clamp is used for data acquisition, which is convenient to use and allows for rapid measurement.

[0060] (3) Based on FFT decomposition and coordinate decomposition, the fundamental and harmonic components of leakage current are accurately calculated. Compared with the prior art, which calculates current based on the fundamental, this application can improve the calculation accuracy.

[0061] (4) Based on the time interval Δt, wireless synchronous measurement or wired synchronous measurement of synchronous ADC sampling at time t is realized to ensure the real-time performance of the measurement. Data compression processing facilitates the transmission of large amounts of data.

[0062] (5) It is equipped with GPS, wireless and wired modules to achieve remote multi-point synchronous data acquisition, accurately locate the fault point in the leakage current investigation process, and calculate the leakage current when the branch spacing is large or the number of branches is large; it can detect and locate the leakage current of multiple branches of three-phase four-wire or three-phase five-wire cables, especially in the case of three-phase five-wire cables, and promptly remind the load line of incorrect connection or check the equipment leakage current to ensure the user's power safety; it can accurately and quickly locate the leakage fault line and promptly report it to the maintenance personnel for repair, improve work efficiency and reduce the losses of the power supply company. Attached Figure Description

[0063] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are explained in detail together with the embodiments of the invention, but do not constitute a limitation thereof.

[0064] Figure 1 This is a schematic diagram of the low-voltage line leakage current fault detection device of the present invention;

[0065] Figure 2 This is a schematic diagram of the composition and structure of the low-voltage line leakage current fault detection device of the present invention.

[0066] Figure 3 This is a schematic diagram of the structure of the first current acquisition device of the present invention;

[0067] Figure 4 This is a schematic diagram of the structure of the second current collector of the present invention;

[0068] Figure 5 This is a schematic diagram of the detection terminal structure of the present invention;

[0069] Figure 6 This is a schematic diagram of the current coordinate decomposition of the present invention;

[0070] Figure 7 This is a flowchart of the three-phase four-wire leakage current calculation method of the present invention;

[0071] Figure 8 This is a flowchart of the leakage current calculation method for three-phase five-wire circuits according to the present invention;

[0072] Figure label:

[0073] S0, line; S1, first current collector; S2, second current collector; S3, detection terminal.

[0074] 11. First current input circuit; 12. First measurement processor; 13. First wireless module; 14. First GPS module; 15. Power supply circuit; 111. Detachable wireless synchronous measurement current clamp input; 112. Low-voltage flexible high-current clamp input; 121. ADC chip.

[0075] 21. 5-channel current input circuit; 22. Second measurement processor; 23. Second wired module; 221. ADC chip;

[0076] 30. Power supply module; 31. 3-channel voltage input circuit; 32. 3-channel current input circuit; 33. Third measurement processor; 34. Human-machine interaction processor; 35. Human-machine interaction input / output module; 36. Storage module; 37. Third GPS module; 38. Third wireless module; 39. Third wired module; 331. ADC chip. Detailed Implementation

[0077] In the description of this invention, it should be noted that the terms "vertical," "upper," "lower," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0078] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0079] This invention provides a low-voltage line leakage current fault detection device, such as... Figure 1 , Figure 2As shown, it includes a first current collector S1, a second current collector S2, and a detection terminal S3; the first current collector S1 is wirelessly connected to the detection terminal S3 and is configured to collect the current of multiple branches over long distances in overhead lines, as well as the current of multiple branches in busbars, narrow spaces, or lines with thicker wire diameters; the second current collector S2 is wiredly connected to the detection terminal S3 and is configured to collect the current of multiple branches in cable branch boxes; the detection terminal S3 performs leakage current fault detection on the low-voltage line S0 based on the current data from the first current collector S1 and the second current collector S2.

[0080] Among them, such as Figure 3 As shown, the first current acquisition device S1 includes: a first current input circuit 11, a first measurement processor 12, a first wireless module 13, a first GPS module 14, and a power supply circuit 15. The first current input circuit 11 is connected to the first measurement processor 12 and is used to acquire current. The first measurement processor 12 is used to acquire current and sample it to obtain current data. The first wireless module 13 is connected to the first measurement processor 12 and is used to upload the current data to the detection terminal S3 via wireless communication. The first GPS module 14 is connected to the first measurement processor 12 and is used to provide synchronization clock information and geographical location information. The power supply circuit 15 is used to provide operating power to the first current acquisition device S1.

[0081] Specifically, the first current input circuit 11 includes a detachable wireless synchronous measurement current clamp input 111 and a low-voltage flexible high-current clamp input 112. When the first current collector S1 collects overhead long-distance multi-branch current, the first current input circuit 11 includes a detachable wireless synchronous measurement current clamp. When the first current collector S1 collects busbar, narrow space, or thick-diameter line multi-branch current, the first current input circuit 11 includes a low-voltage flexible high-current clamp. Meanwhile, due to the long distances between line branches in overhead line environments and busbar, narrow space, or thick-diameter line environments, the first current collector S1 is divided into an A-phase first current collector S1, a B-phase first current collector S1, a C-phase first current collector S1, and an N-phase first current collector S1, which collect A, B, C, and N phase current data respectively. Using four first current collectors S1 at the same measurement point allows for the simultaneous acquisition of A, B, C, and N phase current data at that measurement point. The first measurement processor 12 uses an STM32F4 series chip and is equipped with an ADC chip 121 for analog-to-digital conversion. The first current input circuit 11 collects current and connects to the ADC chip 121 of the first measurement processor 12. The first wireless module 13 uses a 2.4G wireless module RF2401, and the first GPS module 14 uses a Beidou / GPS dual-mode module SKG125. The power supply circuit 15 steps down the 3.8V lithium battery to power the system. Simultaneously, for multiple first current collectors S1 at different measurement points, the first GPS module 14 can determine the location of each first current collector S1 and achieve multi-point synchronous positioning and data acquisition.

[0082] like Figure 4 As shown, the second current acquisition device S2 includes: a 5-channel current input circuit 21, a second measurement processor 22, and a second wired module 23; the 5-channel current input circuit 21 is connected to the second measurement processor 22 and is used to acquire 5 currents (A, B, C, N, PE); the second measurement processor 22 is used to sample the 5 currents to obtain current data; the second wired module 23 is connected to the second measurement processor 22 and is used to upload the current data to the detection terminal S3 via wired communication.

[0083] The 5-channel current input circuit 21 includes wired current clamps corresponding to the A, B, C, N, and PE channels. The 5 current inputs utilize high-precision open-close current transformers or high-precision current clamps. Depending on whether the environment is a three-phase four-wire or three-phase five-wire system, it can collect the current of the A, B, C, N, and PE branch lines in a three-phase five-wire system or the A, B, C, and N currents in a three-phase four-wire system within a branch box. The second measurement processor 22 uses an STM32F4 series chip and incorporates an ADC chip 221 for analog-to-digital conversion. The current acquisition circuit 21 is connected to the ADC chip 221 of the second measurement processor 22. The second wired module 23 integrates power leads and wired communication, and uses an RJ45 interface for communication. The power lead of the second wired module 23 is connected to the detection terminal S3 to supply power to the second current acquisition unit S2. The second wired module 23 and the detection terminal S3 are connected via wired communication. The second measurement processor 22 is connected to the second wired module 23. The detection terminal S3 continuously queries the second measurement processor 22 to see if it has measured an input current signal through wired communication. After finding one, it uploads the measurement data to the detection terminal S3.

[0084] like Figure 5 As shown, the detection terminal S3 includes a third measurement processor 33, a human-machine interaction processor 34, a human-machine interaction input / output module 35, a storage module 36, a third GPS module 37, a third wireless module 38, a third wired module 39, and a power module 30. The third measurement processor 33 is used to detect low-voltage line leakage current faults based on the current data from the first current collector S1 and the second current collector S2. The third wireless module 38 is connected to the third measurement processor 33 and is used to acquire the current signal from the first current collector S1 and send it to the third measurement processor 33. The third wired module 39 is connected to the third measurement processor 33 and is used to acquire the current signal from the second current collector S2 and send it to the third measurement processor 33. The third GPS module 37 is connected to the third measurement processor 33 and is used to provide synchronization clock information and geographical location information. The power module 30 is used to provide operating power for the detection terminal S3. The third measurement processor 33 is connected to the human-machine interaction processor 34, and the human-machine interaction processor 34 is connected to the human-machine interaction input / output module 35 and the storage module 36 to display and save the detection results.

[0085] In this embodiment, the detection terminal S3 is located on the secondary side, while the first current collector S1 and the second current collector S2 are located on the primary side. Besides receiving data from the first current collector S1 and the second current collector S2, the detection terminal S3 also detects the current and voltage on the secondary side. Therefore, the detection terminal S3 further includes three voltage input circuits 31 and three current input circuits 32. These three voltage input circuits 31 and 3 current input circuits 32 are connected to a third measurement processor 33. The three voltage input circuits 31 and 3 current input circuits 32 collect the three-phase voltage and three-phase current of the secondary circuit. The third measurement processor 33 is used to sample the three-phase voltage and three-phase current of the secondary circuit to obtain secondary side data for further operations and monitoring. Correspondingly, the third measurement processor 33 uses an STM32F4 series chip and is equipped with an ADC chip 331 for analog-to-digital conversion. In addition, the third wireless module 38 adopts the 2.4G wireless module RF2401, the third GPS module 37 adopts the Beidou / GPS dual-mode module SKG125, and the third wired module 39 integrates power leads and wired communication, and uses an RJ45 interface for communication access. The human-machine interaction processor 34 uses an STM32F4 series chip. The third measurement processor 33 is connected to the human-machine interaction processor 34. The human-machine interaction input / output module 35 uses a 3.5-inch standard TFT true-color human-machine interface touch screen. The human-machine interaction processor 34 is connected to the human-machine interaction input / output module 35 to display and control the measured secondary circuit three-phase voltage, secondary circuit three-phase current, and current data acquired from the first current collector S1 and the second current collector S2, as well as the leakage current calculation results. The storage module 36 uses an SD memory card. The human-machine interaction processor 34 is connected to the storage module 36 to store the measured secondary circuit three-phase voltage, secondary circuit three-phase current, and current data acquired from the first current collector S1 and the second current collector S2, as well as the leakage current calculation results. The power supply module 30 converts the battery voltage to supply power to the detection terminal S3.

[0086] Meanwhile, for multiple detection terminals S3 at different measurement points, the location of each detection terminal S3 can be determined by the third GPS module 37, and multi-point synchronous positioning and data acquisition can be achieved.

[0087] The detection terminal S3 calculates the leakage current of low-voltage lines in overhead line environments based on the current data of the first current collector S1, calculates the leakage current of low-voltage lines in busbar, narrow space or thick wire diameter environments, and calculates the leakage current of low-voltage lines in cable branch box environments based on the current data of the second current collector S2; and completes the low-voltage line leakage current fault detection based on the leakage current value.

[0088] (1) As Figure 7 As shown, the process of calculating the leakage current of a three-phase four-wire line is as follows:

[0089] Step 1-1: Obtain the A, B, C, and N phase vector current signals through the first or second current acquisition device:

[0090] For leakage current calculation on three-phase four-wire lines in overhead line environments, four primary current acquisition devices can be used. The primary current input circuit uses detachable wireless synchronous measurement current clamps, which are installed on the A, B, C, and N phase lines to collect the vector current signals of phases A, B, C, and N respectively. For leakage current calculation on three-phase four-wire lines in busbar, narrow space, or thicker wire diameter environments, four primary current acquisition devices can be used. The primary current input circuit uses low-voltage flexible high-current clamps, which are installed on the A, B, C, and N phase lines respectively to collect the vector current signals of phases A, B, C, and N respectively. For leakage current calculation on three-phase four-wire lines in cable branch boxes, a five-channel current input circuit of a secondary current acquisition device can be used to collect the vector current signals of phases A, B, C, and N. Four of the five current input circuits, along with four high-precision current clamps, are installed on the A, B, C, and N phase lines.

[0091] The detection terminal can send a synchronous measurement command to the first current collector and / or the second current collector at time intervals Δt; the first current collector and / or the second current collector respond to the synchronous acquisition command from the detection terminal, acquire the branch current signal, compress the data, and synchronously upload the data to the detection terminal wirelessly or via wired connection.

[0092] In this embodiment, the following acquisition mechanism is set: at time t, the detection terminal sends a synchronous measurement command to the first current collector and / or the second current collector. The first current collector and / or the second current collector start the measurement. When there is measured current data, they respond to the detection terminal, respond, compress the current data packet and upload it. After successful response, the current measurement data at time t is recorded synchronously in real time. If the response fails, the synchronous measurement command is sent and responded to at time t+Δt. Δt is set to 500ms until all the first current collectors and all the second current collectors respond, obtaining the vector current signals of phases A, B, C, and N at the same time. The responded current data is compressed and sent to the detection terminal.

[0093] Steps 1-2: The detection terminal decompresses the acquired current data and uses digital signal processing technology to process it. FFT decomposition is performed, decomposing the signal into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components. The vector current signal of a certain phase is decomposed as follows:

[0094]

[0095] in, This is a vector current signal, where i0 is the DC component of the current and ω1 is the fundamental frequency. The phase of the fundamental component. Let m be the fundamental component and i be the harmonic order. n , This represents the amplitude and phase of the m-th harmonic current, and the frequency ω of the m-th harmonic. m It is an integer multiple of the fundamental frequency ω1;

[0096] Steps 1-3, refer to Figure 6 Establish a two-dimensional coordinate system for... The fundamental and harmonic components are decomposed into coordinates to obtain the x-coordinate decomposed current I. mx Decomposing the current I using the y-coordinate my The decomposition of one component of a certain phase vector current signal is as follows:

[0097]

[0098]

[0099] in, The m-th current, that is, the m-th component of a certain phase vector current signal, corresponds to... This represents the phase of the m-th harmonic current;

[0100] right The vector signals of the fundamental and harmonic components are decomposed into coordinates to obtain I. Amx =I Am ·cosφ Am ;I Bmx =I Bm ·cosφ Bm ;I Cmx =I Cm ·cosφ Cm ;I Nmx =I Nm ·cosφ Nm ;I Amy =I Am ·sinφ Am ;I Bmy =I Bm ·sinφ Bm ;I Cmy =I Cm ·sinφ Cm ;I Nmy =I Nm ·sinφ Nm ;

[0101] Among them, I AmxI represents the amplitude component of the m-th harmonic on the x-axis after FFT decomposition of the phase A current signal; Amy I represents the amplitude component of the m-th harmonic on the y-axis after FFT decomposition of the phase A current signal; Am φ represents the amplitude of the m-th harmonic after FFT decomposition of the phase A current signal; Am I represents the phase of the m-th harmonic after FFT decomposition of the A-phase current signal; Bmx I represents the amplitude component of the m-th harmonic on the x-axis after FFT decomposition of the B-phase current signal; Bmy I represents the amplitude component of the m-th harmonic on the y-axis after FFT decomposition of the B-phase current signal. Bm φ represents the amplitude of the m-th harmonic after FFT decomposition of the B-phase current signal; Bm I represents the phase of the m-th harmonic after FFT decomposition of the B-phase current signal; Cmx I represents the amplitude component of the m-th harmonic on the x-axis after FFT decomposition of the C-phase current signal; Cmy I represents the amplitude component of the m-th harmonic on the y-axis after FFT decomposition of the C-phase current signal. Cm φ represents the amplitude of the m-th harmonic after FFT decomposition of the C-phase current signal; Cm I represents the phase of the m-th harmonic after FFT decomposition of the C-phase current signal; Nmx I represents the amplitude component of the m-th harmonic on the x-axis after FFT decomposition of the N-phase current signal; Nmy I represents the amplitude component of the m-th harmonic on the y-axis after FFT decomposition of the N-phase current signal; Nm φ represents the amplitude of the m-th harmonic after FFT decomposition of the N-phase current signal; Nm The phase of the m-th harmonic after FFT decomposition of the N-phase current signal is given.

[0102] Steps 1-4: Calculate the amplitude I of the leakage current. L and phase φ L The amplitudes are as follows:

[0103]

[0104] Among them, I Lmx I is the sum of the amplitude components of the m vector currents along the x-axis after two decompositions of the four-phase current signal. Lmy This is the sum of the amplitude components of the m-th vector current in the y-axis after two decompositions of the four-phase current signal. Specifically:

[0105]

[0106] Among them, I L I is the leakage current amplitude. Lm The amplitude component of the m-th harmonic after FFT decomposition of the vector current signal;

[0107] The phases are as follows:

[0108]

[0109] Among them, I L1x I is the sum of the amplitude components of the fundamental wave on the x-axis after two decompositions of the four-phase current signal. L1y This is the sum of the amplitude components of the fundamental frequency on the y-axis after two decompositions of the four-phase current signal. Specifically, the amplitude component I of the fundamental frequency of the leakage current on the x-axis is... L1x =I A1x +I B1x +I C1x +I N1x And the amplitude component I of the fundamental frequency of leakage current on the y-axis L1y =I A1y +I B1y +I C1y +I N1y ;

[0110] Among them, I A1x I represents the amplitude component of the fundamental wave on the x-axis after FFT decomposition of the phase A current signal; B1x I represents the amplitude component of the fundamental wave on the x-axis after FFT decomposition of the B-phase current signal; C1x I represents the amplitude component of the fundamental wave on the x-axis after FFT decomposition of the C-phase current signal. N1x I represents the amplitude component of the fundamental frequency on the x-axis after FFT decomposition of the N-phase current signal; A1y I represents the amplitude component of the fundamental wave on the y-axis after FFT decomposition of the phase A current signal; B1y I represents the amplitude component of the fundamental wave on the y-axis after FFT decomposition of the B-phase current signal; C1y I represents the amplitude component of the fundamental wave on the y-axis after FFT decomposition of the C-phase current signal. N1y This represents the amplitude component of the fundamental wave on the y-axis after FFT decomposition of the N-phase current signal.

[0111] (2) Figure 8 As shown, the process for calculating the leakage current of a three-phase five-wire circuit is as follows:

[0112] Step 1-1: Obtain the vector current signals of phases A, B, C, N, and PE through the second current acquisition device:

[0113] For a three-phase five-wire system, a second current acquisition device and detection terminal are selected for leakage current detection. Five measurement circuits and five high-precision current clamps are installed on the five-phase current lines A, B, C, N, and PE using the five current input circuits.

[0114] The detection terminal can send a synchronous measurement command to the second current collector at time intervals Δt; the second current collector responds to the synchronous acquisition command from the detection terminal, acquires the branch current signal, performs data compression, and synchronously uploads the data to the detection terminal wirelessly or via wired connection.

[0115] In this embodiment, the following acquisition mechanism is set: at time t, the detection terminal sends a synchronous measurement command to the second current acquisition device. The second current acquisition device starts the measurement and responds to the detection terminal when there is measured current data. It compresses the current data packet and uploads it. After successful response, the current measurement data at time t is recorded synchronously in real time. If the response fails, the synchronous measurement command is sent and responded to again at time t+Δt. Δt is set to 500ms until all the second current acquisition devices respond, and the vector current signals of phases A, B, C, and N at the same time are obtained. The responded current data is compressed and sent to the detection terminal.

[0116] Step 1-2: Set the current threshold δ PE In the embodiments of this application, δ PE =50mA, if If there is a problem with the PE phase, it prompts you to check if there is an incorrect connection in the load line or if the equipment is leaking current. Proceed to step 1-6. Otherwise, execute steps 1-3 to 1-5 and refer to the above steps for collecting and calculating leakage current in a three-phase four-wire system to calculate the leakage current of the line.

[0117] Steps 1-3: Using digital signal processing techniques to... FFT decomposition is performed, decomposing the signal into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components. The vector current signal of a certain phase is decomposed as follows:

[0118]

[0119] in, This is a vector current signal, where i0 is the DC component of the current and ω1 is the fundamental frequency. The fundamental component phase is represented by m, and the harmonic order is represented by i. n , This represents the amplitude and phase of the m-th harmonic current, and the frequency ω of the m-th harmonic. m It is an integer multiple of the fundamental frequency ω1;

[0120] Steps 1-4, refer to Figure 6 Establish a two-dimensional coordinate system for... The fundamental and harmonic components are decomposed into coordinates to obtain the x-coordinate decomposed current I. mx Decomposing the current I using the y-coordinate my The decomposition of one component of a certain phase vector current signal is as follows:

[0121]

[0122]

[0123] in, The m-th current, that is, the m-th component of a certain phase vector current signal, corresponds to... This represents the phase of the m-th harmonic current;

[0124] Steps 1-5: Calculate the amplitude I of the leakage current. L and phase φ L :

[0125]

[0126]

[0127] Among them, I Lmx I is the sum of the amplitude components of the m vector currents along the x-axis after two decompositions of the four-phase current signal. Lmy I is the sum of the amplitude components of the m-th vector current in the y-axis after two decompositions of the four-phase current signal; L1x I is the sum of the amplitude components of the fundamental wave on the x-axis after two decompositions of the four-phase current signal. L1y It is the sum of the amplitude components of the fundamental wave on the y-axis after two decompositions of the four-phase current signal;

[0128] Steps 1-6: Calculate the amplitude and phase of the PE phase current:

[0129] Step 1-6-1: Utilize digital signal processing technology to... Performing FFT decomposition, the component is decomposed into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components, yielding:

[0130]

[0131] Step 1-6-2, refer to Figure 6 Establish a two-dimensional coordinate system for... The fundamental and harmonic components are decomposed into coordinates to obtain the x-coordinate decomposed current I of the PE phase current signal. PEmx Decompose the current I in the y-coordinate of the phase current signal of the PE phase. PEmy :

[0132] I PEmx =I PEm ·cosφ PEm

[0133] I PEmy =I PEm ·sinφ PEm

[0134] Among them, IPEm The m-th order current of the PE phase is the m-th component of the PE phase vector current signal, corresponding to φ. PEm This represents the phase of the m-th harmonic current;

[0135] Step 1-6-3: Calculate the amplitude of the PE phase current I PE and phase φ PE :

[0136]

[0137]

[0138] Among them, I PEmx I represents the amplitude components of the m-th vector current along the x-axis after two decompositions of the PE phase current signal. PEmy The amplitude components of the m-th vector current in the y-axis after two decompositions of the PE phase current signal; I PE1x I represents the amplitude component of the fundamental frequency on the x-axis after two decompositions of the PE phase current signal. PE1y The amplitude component of the fundamental wave on the y-axis after two decompositions of the PE phase current signal.

[0139] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A low-voltage line leakage current fault detection device, characterized in that, It includes a first current acquisition unit, a second current acquisition unit, and a detection terminal; The first current acquisition device is wirelessly connected to the detection terminal and is configured to acquire overhead long-distance multi-branch current, as well as busbar, narrow space or thick wire diameter line multi-branch current; The second current acquisition device is wired to the detection terminal and is configured to acquire the current of multiple branches in the cable branch box; The detection terminal performs low-voltage line leakage current fault detection based on the current data from the first current collector and the second current collector. The first current acquisition unit is divided into a phase A first current acquisition unit, a phase B first current acquisition unit, a phase C first current acquisition unit, and a phase N first current acquisition unit, which respectively acquire the current data of phases A, B, C, and N; The first current acquisition device includes: a first current input circuit, a first measurement processor, a first wireless module, a first GPS module, and a power supply circuit. The first current input circuit is connected to the first measurement processor and is used to acquire current. The first measurement processor is used to sample the current to obtain current data. The first wireless module is connected to the first measurement processor and is used to upload the current data to the detection terminal via wireless communication. The first GPS module is connected to the first measurement processor and is used to provide synchronization clock information and geographical location information. The power supply circuit is used to provide operating power for the first current acquisition device. The second current acquisition device includes: a 5-channel current input circuit, a second measurement processor, and a second wired module; the 5-channel current input circuit is connected to the second measurement processor and is used to acquire 5 current channels A, B, C, N, and PE; the second measurement processor is used to acquire the 5 current channels and sample them to obtain current data; the second wired module is connected to the second measurement processor and is used to upload the current data to the detection terminal via wired communication. The detection terminal includes a third measurement processor, a human-machine interaction processor, a human-machine interaction input / output module, a storage module, a third GPS module, a third wireless module, a third wired module, and a power supply module; The third measurement processor is used to detect low-voltage line leakage current faults based on the current data from the first and second current collectors. The third wireless module is connected to the third measurement processor and is used to acquire the current signal from the first current collector and send it to the third measurement processor. The third wired module is connected to the third measurement processor and is used to acquire the current signal from the second current collector and send it to the third measurement processor. The third GPS module is connected to the third measurement processor and is used to provide synchronization clock information and geographical location information. The power module is used to provide working power for the detection terminal. The third measurement processor is connected to a human-machine interaction processor, which is connected to a human-machine interaction input / output module and a storage module for displaying and saving the detection results.

2. The low-voltage line leakage current fault detection device according to claim 1, characterized in that, When the first current collector collects overhead long-distance multi-branch current, the first current input circuit includes a detachable wireless synchronous measurement current clamp. When the first current collector collects busbar, narrow space, or line multi-branch current with thicker wire diameter, the first current input circuit includes a low-voltage flexible high-current clamp.

3. The low-voltage line leakage current fault detection device according to claim 1, characterized in that, The five-channel current input circuit includes wired current clamps corresponding to channels A, B, C, N, and PE.

4. The low-voltage line leakage current fault detection device according to claim 1, characterized in that, The wired module also includes a power lead, which supplies power from the detection terminal to the second current collector.

5. The low-voltage line leakage current fault detection device according to claim 1, characterized in that, The detection terminal calculates the leakage current of low-voltage lines in overhead line environments, low-voltage lines in busbar, narrow space or thick wire diameter environments, and low-voltage lines in cable branch box environments based on the current data of the second current collector. The leakage current value is used to complete the low-voltage line leakage current fault detection.

6. The low-voltage line leakage current fault detection device according to claim 5, characterized in that, The process of calculating the leakage current of a three-phase four-wire line is as follows: Step 1-1: Obtain the A, B, C, and N phase vector current signals through the first or second current acquisition device: , , , ; Steps 1-2: Using digital signal processing technology to... , , , FFT decomposition is performed, decomposing the signal into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components. The vector current signal of a certain phase is decomposed as follows: in, It is a vector current signal. The DC component of the current. The fundamental frequency, The phase of the fundamental component. For harmonic order, , express The amplitude and phase of the second harmonic current The frequency of subharmonics It is the fundamental frequency. Integer multiples of; Steps 1-3, for , , , The fundamental and harmonic components are decomposed into coordinates to obtain... x Coordinate decomposition of current and y Coordinate decomposition of current The decomposition of one component of a certain phase vector current signal is as follows: in, for Secondary current, i.e., the vector current signal of a certain phase. Secondary component, corresponding express The phase of the subharmonic current; Steps 1-4: Calculate the amplitude of leakage current. and phase : in, After two decompositions of the four-phase current signal Secondary vector current in x The sum of the amplitude components of the axis, After two decompositions of the four-phase current signal Secondary vector current in y The sum of the amplitude components; The fundamental frequency of the four-phase current signal after two decompositions is at x The sum of the amplitude components of the axis, The fundamental frequency of the four-phase current signal after two decompositions is at y The sum of the amplitude components of the axis.

7. A low-voltage line leakage current fault detection device according to claim 5, characterized in that, The process of calculating the leakage current of a three-phase five-wire circuit is as follows: Step 1-1: Obtain the vector current signals of phases A, B, C, N, and PE through the second current acquisition device: , , , , ; Step 1-2: Set the current threshold ,like If yes, proceed to steps 1-6; otherwise, execute steps 1-3. Steps 1-3: Using digital signal processing techniques to... , , , FFT decomposition is performed, decomposing the signal into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components. The vector current signal of a certain phase is decomposed as follows: in, It is a vector current signal. The DC component of the current. The fundamental frequency, The phase of the fundamental component. For harmonic order, , express The amplitude and phase of the second harmonic current The frequency of subharmonics It is the fundamental frequency. Integer multiples of; Steps 1-4, for , , , The fundamental and harmonic components are decomposed into coordinates to obtain... x Coordinate decomposition of current and y Coordinate decomposition of current The decomposition of one component of a certain phase vector current signal is as follows: in, for Secondary current, i.e., the vector current signal of a certain phase. Secondary component, corresponding express The phase of the subharmonic current; Steps 1-5: Calculate the amplitude of leakage current. and phase : in, After two decompositions of the four-phase current signal Secondary vector current in x The sum of the amplitude components of the axis, After two decompositions of the four-phase current signal Secondary vector current in y The sum of the amplitude components; The fundamental frequency of the four-phase current signal after two decompositions is at x The sum of the amplitude components of the axis, The fundamental frequency of the four-phase current signal after two decompositions is at y The sum of the amplitude components of the axis; Steps 1-6: Calculate the amplitude and phase of the PE phase current: Step 1-6-1: Utilize digital signal processing technology to... Performing FFT decomposition, the component is decomposed into a superposition of DC component, fundamental component, and 2nd to 50th harmonic components, yielding: Step 1-6-2, for The fundamental and harmonic components are decomposed into coordinates to obtain the PE phase current signal. x Coordinate decomposition of current and PE phase current signal y Coordinate decomposition of current : in, PE phase Secondary current, i.e., the vector current signal of the PE phase. Secondary component, corresponding express The phase of the subharmonic current; Step 1-6-3: Calculate the amplitude of the PE phase current. and phase : in, After two decompositions of the PE phase current signal Secondary vector current in x The amplitude components of the axis, After two decompositions of the PE phase current signal Secondary vector current in y The amplitude components; The fundamental frequency of the PE phase current signal after two decompositions is at x The amplitude components of the axis, The fundamental frequency of the PE phase current signal after two decompositions is at y The amplitude component of the axis.

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