Non-intrusive online low-voltage line phase sequence identification method based on multiple differential electrodes

Abstract

The invention discloses a non-intrusive on-line low-voltage line phase sequence identification method based on multiple differential electrodes, and the method comprises the steps: collecting voltage signals through an electric field sensor composed of calipers of a specific structure with multiple pairs of built-in differential electrodes, processing the signal collection problem of cables with different wire diameters, and enabling an MCU control chip to be combined with a Beidou module, thereby achieving the recognition of the phase sequence of a low-voltage line. Synchronous sampling of a wire outlet end and a to-be-measured point can be realized; the system can adaptively select a group of differential electrodes with optimal signals, ensure that the electrodes are in an opposite state, perform automatic gain control and analog-to-digital conversion processing on the collected signals, and then transmit data back to a background server through a 4G module; the server performs Fourier transform on the waveform data of the wire outlet end and the to-be-measured point, obtains an initial phase, calculates a phase difference, and judges a phase line to which the measuring point belongs according to the phase difference; non-intrusive measurement is adopted, electricity is not taken from a live cable, the safety coefficient is high, data are automatically processed through the server, and phase line identification can be rapidly and accurately achieved.

Description

Technical Field

[0001] This invention belongs to the field of power system detection technology, specifically relating to a non-intrusive online low-voltage line phase sequence identification method and system based on multiple differential electrodes. It is particularly suitable for non-intrusive phase sequence identification scenarios of online low-voltage lines and can be widely used in low-voltage line maintenance, line inspection, load adjustment and three-phase imbalance monitoring. Background Technology

[0002] In low-voltage power distribution systems, phase sequence identification of three-phase lines is a crucial step in ensuring the safe, stable, and efficient operation of the power system. During low-voltage line maintenance and inspection, in order to reasonably adjust the load rate and accurately understand the three-phase imbalance, staff must identify the phase line to which the current line belongs and perform corresponding load adjustment operations accordingly.

[0003] Currently, commonly used electrical measuring tools such as multimeters and power quality analyzers cannot directly identify the phase sequence of low-voltage lines. Traditional phase sequence identification methods mainly rely on the wiring sequence, markings, or color distinctions of the lines. However, in practical applications, some lines have problems such as incorrect wiring sequence, missing markings, or single color, making it difficult for these traditional methods to accurately identify the phase sequence.

[0004] In such situations, staff typically have to manually trace the phase sequence along the lines to determine it. However, this method is not only time-consuming and labor-intensive, but also carries a certain probability of error due to the subjectivity of human judgment and the complexity of the line environment. This could potentially lead to power system malfunctions or even safety accidents. Therefore, developing a method that can quickly, accurately, and safely identify the phase sequence of low-voltage lines has become an urgent technical problem to be solved in the field of power system detection. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing low-voltage line phase sequence identification methods, such as reliance on line identifiers leading to errors, low efficiency and large errors in manual queries, and poor security of invasive measurements. It provides a non-invasive online low-voltage line phase sequence identification method and system based on multiple differential electrodes to achieve fast, accurate, and safe phase sequence identification.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] This invention provides a non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes. The method is implemented using a system consisting of an electric field sensor composed of multiple pairs of differential electrodes and a specific structure slot, an AGC circuit, an ADC, an MCU control chip, a BeiDou module, a 4G module, and a backend server. The method includes the following steps:

[0008] Step 1, Voltage Signal Acquisition: A specific slot structure adapts to cables of different diameters, allowing for a closer fit with the differential electrodes. This enables adaptive selection of the electric field acquisition electrode sheet, resulting in high signal-to-noise ratio signals. An electric field sensor composed of multiple pairs of differential electrodes acquires the voltage signal of the low-voltage line under test. Through the differentiated layout design of multiple sets of differential electrodes, precise adaptation to the test line with different wire diameters can be achieved. One set of electrodes can be perfectly aligned with the target line, ensuring high-quality acquisition of the core signal.

[0009] Step 2: First, set all amplifier circuits to fixed gain. After ADC conversion, calculate the amplitude and total harmonic distortion (THD) of each channel signal. Filter out the channel corresponding to the strongest signal and the lowest THD to determine the slot position of the current cable. Then, acquire the signal for the differential electrode of the slot, dynamically increase the loop gain to make the signal amplitude within the maximum effective range of the ADC, and then perform ADC conversion.

[0010] Step 3, Synchronous Sampling and Data Transmission: The PPS signal output by the Beidou module serves as the trigger signal for the start of ADC sampling on different devices, achieving sampling synchronization across all devices; the MCU control chip adds a timestamp to the data converted by the ADC and transmits it back to the backend server in real time via the 4G module.

[0011] Step 4, Server background data processing: The server receives waveform data, performs Fourier transform on it, obtains the initial phase, and stores the phase and time stamp together;

[0012] Step 5, Phase line identification: Steps 1 to 3 are executed simultaneously at the power output terminal and the point to be measured to obtain waveform data from both. The server performs Fourier transform on the waveform data from both terminals to obtain the initial phase and calculate the phase difference. When the phase difference between the measuring point and the waveform of a certain output terminal is less than the preset allowable error X, it is determined that the phase line of the measuring point is consistent with the phase line of the output terminal.

[0013] In a preferred embodiment of the present invention, in step 1, the electric field acquisition adopts a specific structure slot to achieve adaptive selection and tight integration of cables of different diameters with the corresponding slots; multiple pairs of differential electrode plates for acquiring electric field strength are distributed in the center of each slot segment to achieve the alignment of the cable and the electrode plates, thereby realizing signal acquisition.

[0014] In a preferred embodiment of the present invention, the preset allowable error X in step 5 ranges from 0° to 1°.

[0015] In a preferred embodiment of the present invention, the dynamic adjustment gain range of the AGC circuit is determined according to the voltage signal strength range of the low-voltage line, and multiple pairs of differential electrodes are added to adaptively select the strongest signal and sense the signal that is closest to the measured phase line voltage waveform.

[0016] In a preferred embodiment of the present invention, the BeiDou module is also used to provide positioning information to the system and realize the associated storage of phase sequence identification and location information.

[0017] This invention provides a system for implementing a non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes, comprising an electric field sensor composed of multiple pairs of differential electrodes, an AGC circuit, an ADC, an MCU control chip, a BeiDou module, a 4G module, and a back-end server; the electric field sensor is connected to the AGC circuit, the AGC circuit is connected to the ADC and the MCU control chip respectively, the ADC, the BeiDou module, and the 4G module are connected to the MCU control chip respectively, and the 4G module is communicatively connected to the back-end server.

[0018] In a preferred embodiment of the present invention, the electric field sensor employs multiple pairs of differential electrodes, arranged symmetrically on the left and right sides with a single-core cable as the center, and the AGC circuit is a variable gain amplifier.

[0019] In a preferred embodiment of the present invention, the ADC is an AD7606BSTZ module.

[0020] In a preferred embodiment of the present invention, the BeiDou module is a G28Z2FTTL module and the 4G module is a WH-GM5_C2833613 module.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The non-invasive measurement method avoids direct contact with low-voltage lines, greatly improves the safety factor in the measurement process, and reduces the risk of electric shock and other safety accidents.

[0023] (2) Through a specific slot structure and a differentiated layout design of multiple pairs (no less than 2 pairs) of differential electrodes, one set of differential electrodes can be perfectly aligned with the circuit under test for any wire diameter. This design ensures that the sampling voltage phase is basically unaffected by other circuits, thereby guaranteeing a high signal-to-noise ratio of the core detection signal and effectively improving the accuracy of phase sequence identification. (3) By using the AGC circuit to dynamically adjust the gain, the signal is ensured to be within the range of the ADC, avoiding the problem of invalid sampling caused by weak or oversaturated signals, and ensuring the validity and reliability of the acquired data.

[0024] (4) Using Beidou PPS as the sampling synchronization trigger signal, accurate synchronous sampling between different devices is realized, making the device data at the same time scale comparable, and laying the foundation for accurate calculation of phase difference.

[0025] (5) After data collection, the data is transmitted back to the backend server in real time, and the server performs automatic calculation and judgment, which avoids identification errors caused by human factors and improves the efficiency and accuracy of phase sequence identification.

[0026] (6) Combining the positioning function of the Beidou module, it is possible to associate phase sequence identification with measurement point location information, which facilitates staff to have a comprehensive and intuitive understanding and management of the phase sequence status of the line. It supports the use of extension poles of different lengths to adapt to various outdoor measurement scenarios, making operation more flexible and convenient. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments or prior art, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes provided in an embodiment of the present invention; the output terminal of the electric field sensor is connected to the input terminal of the AGC circuit, the output terminal of the AGC circuit is connected to the input terminal of the ADC, the output terminal of the ADC is connected to the input terminal of the MCU control chip, the output terminal of the Beidou module is connected to the input terminal of the MCU control chip, the output terminal of the MCU control chip is connected to the input terminal of the 4G module, and the 4G module is connected to the back-end server through wireless network communication.

[0029] Figure 2 This is a schematic diagram of the slot structure and differential electrode layout provided in an embodiment of the present invention. Cables of different diameters will be in different slots, and there is a set of differential electrodes facing each other in the slot.

[0030] Figure 3 The image shows a side view of the slot structure and differential electrode provided in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The terms "upper," "lower," "front," "rear," "left," and "right," etc., used when describing the installation position or direction of the structure or components in this embodiment are based on the orientation shown in the accompanying drawings. They are merely for convenience of description, used to distinguish the relative positions of various components or directions, and do not represent the orientation of the system or functional components in this embodiment during use.

[0032] refer to Figure 1 This invention provides a non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes. The method is implemented using a system consisting of an electric field sensor composed of multiple pairs (no less than two pairs) of differential electrodes, an AGC circuit, an ADC, an MCU control chip, a BeiDou module, a 4G module, and a backend server. The method includes the following steps:

[0033] Step 1, Voltage Signal Acquisition: A specific slot structure adapts to cables of different diameters, allowing for a closer fit with the differential electrodes. This enables adaptive selection of the electric field acquisition electrode sheet, resulting in high signal-to-noise ratio signals. An electric field sensor composed of multiple pairs (no less than 2 pairs) of differential electrodes is used to acquire the voltage signal of the low-voltage line under test. Through the differentiated layout design of multiple sets of differential electrodes, precise adaptation to the test line with different wire diameters can be achieved. One set of electrodes can be perfectly aligned with the target line, ensuring high-quality acquisition of the core signal.

[0034] Step 2, Signal Processing: First, set all amplifier circuits to fixed gain. After ADC conversion, calculate the amplitude and total harmonic distortion (THD) of each channel signal, and filter out the channel corresponding to the strongest signal and the lowest THD to determine the slot location of the current cable. Then, acquire the signal for the differential electrode of the slot, dynamically adjust the loop gain to make the signal amplitude within the maximum effective range of the ADC, and then perform ADC conversion processing.

[0035] Step 3, Synchronous Sampling and Data Transmission: The PPS output by the Beidou module serves as the trigger signal for the start of ADC sampling on different devices, achieving sampling synchronization across all devices; the MCU control chip adds a timestamp to the data converted by the ADC and transmits it back to the backend server in real time via the 4G module; providing basic data for the server to perform synchronous comparison.

[0036] Step 4, Server background data processing: The server receives the waveform data, performs a Fourier transform on it, obtains the initial phase, and stores the phase and time stamp together.

[0037] Step 5, Phase Line Identification: Steps 1 to 3 are executed simultaneously at the power supply output terminal (transformer output terminal, known phase sequence) and the point to be measured to acquire waveform data from both. The server performs a Fourier transform on the waveform data from both terminals to obtain the initial phase and calculate the phase difference. When the phase difference between the measuring point and the waveform at a certain output terminal is less than a preset allowable error X, it is determined that the phase line to which the measuring point belongs is consistent with the phase line at that output terminal. In this embodiment, the server background software performs a Fourier transform on the waveform data acquired from the output terminal and the measuring point respectively to obtain the initial phase of each waveform and calculate the phase difference between them. Based on the phase difference, the phase line to which the measuring point belongs is determined: the phase difference of the initial phase of waveforms of different phase lines at the same time is ±120°, and the initial phase of waveforms of the same phase line at the same time is the same. When the phase difference between the measuring point and the waveform at a certain output terminal is less than a preset allowable error X, it is determined that the phase line to which the measuring point belongs is consistent with the phase line at that output terminal.

[0038] refer to Figure 2 In step 1, voltage signal acquisition involves a specific angular arrangement of multiple sets of differential electrodes. This ensures that, regardless of the cable diameter at the test point, there is always at least one set of differential electrodes directly facing it, guaranteeing a high signal-to-noise ratio for the core detection signal. Preferably, the electric field sensor employs multiple pairs (no fewer than two pairs) of differential electrodes, symmetrically arranged around the single-core cable. (Reference) Figure 3 , Figure 3 Regardless of the cable's diameter, there are corresponding slots at different heights, with corresponding differential electrodes facing each other to ensure measurement effectiveness.

[0039] The preset allowable error X in step 5 is set according to the actual measurement accuracy requirements, with a value range of 0° to 1°. The dynamic adjustment gain range of the AGC circuit is determined based on the voltage signal strength range of the low-voltage line, ensuring that signals of different strengths can be adjusted to the optimal range of the ADC. The Beidou module is also used to provide positioning information for the system, facilitating the server to record the location information of the measurement points and realize the associated storage of phase sequence identification and location information.

[0040] Figure 2 The design features a collaborative layout of multiple pairs of differential electrodes and slots, centered around the single-core cable under test. Multiple sets of differential electrodes (such as S1P / S1N, S2P / S2N, etc., with no fewer than two pairs) are symmetrically arranged around the cable, forming a comprehensive acquisition array. Test cables of different diameters naturally adapt to the corresponding slot positions; regardless of wire diameter, there is always a set of differential electrodes that precisely aligns with the wire core, effectively eliminating environmental common-mode noise interference. The layout also includes a data display screen, which intuitively presents the acquisition status and core data, providing visual support for subsequent signal filtering and channel determination, ensuring stable acquisition of high signal-to-noise ratio signals.

[0041] Figure 3The side view reveals the three-dimensional fit between the slots and differential electrodes. Different diameter test cables correspond to dedicated slots of varying heights. The slot dimensions are designed based on the common low-voltage cable diameter gradient, ensuring a tight fit between the cables and the slot walls. The differential electrodes (S1-S6) are fixed in the center of each slot, their installation height precisely aligned with the cable core height of the corresponding slot. Regardless of cable thickness, the electrodes and cores are aligned directly. This side-view structure visually demonstrates the precise matching relationship between cable diameter, slot, and electrode, physically ensuring the stability and reliability of signal acquisition and laying the foundation for subsequent gain adjustment and phase identification.

[0042] like Figure 1 As shown, the present invention also provides a system for implementing the above method, comprising an electric field sensor composed of multiple pairs (not less than 2 pairs) of differential electrodes, an AGC circuit, an ADC, an MCU control chip, a Beidou module, a 4G module, and a back-end server; the electric field sensor is connected to the AGC circuit, the AGC circuit is connected to the ADC, the ADC, the Beidou module, and the 4G module are respectively connected to the MCU control chip, and the 4G module is communicatively connected to the back-end server.

[0043] like Figure 2 As shown, the electric field sensor employs multiple pairs (no fewer than two pairs) of differential electrodes, arranged in a ring around a single-core cable. In this embodiment, the electrodes are made of copper to achieve signal acquisition coverage for wires of different diameters.

[0044] The AGC circuit uses a variable gain amplifier, model AD8367, with a dynamic gain adjustment range of -11dB to +31dB. It can automatically adjust the gain according to the input signal strength to ensure that the output signal is within the range of the ADC.

[0045] The ADC uses a high-precision analog-to-digital converter (ADC) of model ADS1256, with a resolution of 24 bits and a sampling rate of up to 30kSPS, which can meet the high-precision sampling requirements of low-voltage line voltage signals. Preferably, the ADC uses an AD7606BSTZ module.

[0046] MCU control chip: The STM32F407 microcontroller unit is used, with a main frequency of 168MHz. It has rich peripheral interfaces and can effectively control the AGC, ADC, Beidou module and 4G module.

[0047] The BeiDou module uses the G28Z2FTTL module, which supports BeiDou B1I signal reception and outputs PPS pulses with an accuracy of up to 10ns, providing the system with a high-precision synchronization clock and positioning information, with a positioning accuracy of 10m.

[0048] The 4G module uses the WH-GM5_C2833613 module, which supports LTE Cat1 network and has a data transmission rate of up to 10Mbps, ensuring that the collected data can be transmitted back to the backend server in real time.

[0049] Backend server: It adopts a high-performance industrial server, configured with an Intel Xeon E5-2680v4 processor, 32GB of memory, 1TB solid-state drive, and backend processing software based on Windows Server 2016 operating system, which has the functions of data receiving, storage, processing and analysis.

[0050] Specifically, the voltage signal acquisition process: the multiple pairs (no less than 2 pairs) of differential electrodes S1P / S1N, S2P / S2N, S3P / S3N, S4P / S4N, and S5P / S5N of the electric field sensor are arranged as follows: Figure 2 and Figure 3 The differential electrodes are arranged in a layout that surrounds the low-voltage single-core cable to be measured. When voltage flows through the low-voltage line, an electric field is generated in the surrounding area. The differential electrodes sense this electric field signal and convert it into a voltage signal. The use of differential electrodes effectively eliminates common-mode noise in the environment, such as electromagnetic interference, making the acquired voltage signal more reliable. Simultaneously, the design of multiple sets of differential electrodes with slots of different sizes ensures that regardless of the wire diameter at the test point, there is always a set of differential electrodes facing it, guaranteeing a high signal-to-noise ratio and improving the system's adaptability and detection stability in complex wire diameter scenarios. This provides a stable input for subsequent signal processing and phase recognition.

[0051] Signal processing: The acquired voltage signal first enters the AGC circuit. Multiple AD8367 variable gain amplifiers maintain the same amplification ratio. By judging the strength and THD of the acquired signal, the circuit determines which pair of differential electrodes is currently facing the cable. Then, the gain is synchronously adjusted to stabilize the signal amplitude within the optimal range (0-5V) of the ADC (ADS1256). Simultaneously, the gain adjustment of each channel remains synchronized to ensure that the relative relationship between the signals of each channel remains consistent, providing a reliable reference for subsequent signal comparison and phase identification.

[0052] Synchronous sampling and data transmission process: The BeiDou module (BD-1575M3) outputs one PPS pulse signal per second, which serves as the trigger signal for ADC sampling. When the PPS pulse arrives, the MCU control chip (STM32F407) sends a sampling command to the ADC, and the ADC begins sampling the signal after AGC processing. Since all devices use the BeiDou PPS pulse as the trigger signal, precise synchronous sampling between different devices is achieved, ensuring the temporal consistency of signals acquired at the same point in time.

[0053] After the ADC sampling is completed, the analog signal is converted into a digital signal and transmitted to the MCU control chip. Upon receiving the digital signal, the MCU control chip obtains the start time information (accurate to milliseconds) from the BeiDou module and adds a timestamp to the data set. Subsequently, the MCU packages and sends the timestamped data to the backend server via the 4G module (EC200S). The 4G module establishes a connection with the server using the TCP / IP protocol, ensuring the reliability and real-time performance of data transmission.

[0054] Server backend data processing: After receiving data transmitted from various devices, the backend server first verifies the data to check its integrity and validity. For valid data, the server stores it in the database, while also recording the corresponding timestamp, measurement point number, and positioning information (provided by the BeiDou module).

[0055] The server's backend processing software performs Fourier transform on the stored waveform data. Fourier transform converts time-domain waveform signals into frequency-domain signals, thereby extracting characteristic information such as frequency, amplitude, and phase. By performing Fourier transform on the waveform data, the server can accurately obtain the starting phase of the voltage signal at each measurement point and associate and store the starting phase with the corresponding timescale and measurement point information, forming a complete phase information database.

[0056] Phase line identification process: When performing phase line identification, the staff first installs the same acquisition equipment as the measurement point at the power supply output terminal (transformer output terminal, the known phase sequence is phase A, phase B, and phase C). At the same time, the acquisition equipment at the output terminal and the measurement point is started to perform the above-mentioned voltage signal acquisition, signal processing, synchronous sampling and data transmission process.

[0057] The server's backend software retrieves waveform data from the database for the line terminals (phase A, phase B, and phase C) and the point to be measured at the same time scale. It then performs Fourier transforms on these waveforms to obtain their respective initial phases. Finally, it calculates the initial phase difference between the point to be measured and the output phases A, B, and C.

[0058] According to the characteristics of three-phase electricity, at the same time, the phase difference between phases A, B, and C is 120°, that is, the phase difference between phase B and phase A is 120°, the phase difference between phase C and phase B is 120°, and the phase difference between phase C and phase A is 240° (or -120°). Furthermore, the initial phases of the same phase line are the same at the same time.

[0059] The preset allowable error X is set to 1°. When the phase difference between the point to be measured and phase A of the outgoing line is less than 1°, the point to be measured is determined to be phase A; when the phase difference between the point to be measured and phase B of the outgoing line is less than 1°, the point to be measured is determined to be phase B; when the phase difference between the point to be measured and phase C of the outgoing line is less than 1°, the point to be measured is determined to be phase C.

[0060] For example, if the starting phase of phase A at the outgoing terminal is 30° at a certain time scale, and the starting phase of the point to be measured is 30.5° at the same time scale, and the phase difference between the two is 0.5°, which is less than the preset allowable error of 1°, then the point to be measured is determined to be phase A.

[0061] System Testing and Verification: To verify the effectiveness and accuracy of this invention, the following tests were conducted: In a low-voltage power distribution line, the outgoing terminals of phases A, B, and C with known phase sequences, and three measurement points with unknown phase sequences (actually phases A, B, and C, respectively), were selected. The method of this invention was used for phase sequence identification. The test results showed that all three measurement points with unknown phase sequences were accurately identified, consistent with the actual phase sequences, with an identification accuracy rate of 100%. Furthermore, no safety incidents occurred during the measurement process, data transmission was real-time, and the server processing speed was fast, with the time from data acquisition to the output of the phase sequence identification results not exceeding 5 seconds.

[0062] Multiple tests were conducted using the sensor and wires of different diameters. The results showed that the system could accurately identify the phase sequence regardless of the wire diameter, verifying the effectiveness of the slot structure and differential electrode arrangement. Tests were performed on voltage signals of varying intensities (220V±20%), and the AGC circuit consistently adjusted the signal to the ADC range, ensuring the validity of the sampled data and further validating the system's reliability.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes, characterized in that, The system, based on an electric field sensor composed of multiple pairs of differential electrodes and a specific structure slot, an AGC circuit, an ADC, an MCU control chip, a BeiDou module, a 4G module, and a backend server, includes the following steps: Step 1, Voltage Signal Acquisition: A specific slot structure adapts to cables of different diameters, allowing for a closer fit with the differential electrodes. This enables adaptive selection of the electric field acquisition electrode sheet, resulting in high signal-to-noise ratio signals. An electric field sensor composed of multiple pairs of differential electrodes acquires the voltage signal of the low-voltage line under test. Through the differentiated layout design of multiple sets of differential electrodes, precise adaptation to the test line with different wire diameters can be achieved. One set of electrodes can be perfectly aligned with the target line, ensuring high-quality acquisition of the core signal. Step 2: First, set all amplifier circuits to fixed gain. After ADC conversion, calculate the amplitude and total harmonic distortion (THD) of each channel signal. Filter out the channel corresponding to the strongest signal and the lowest THD to determine the slot position of the current cable. Then, acquire the signal for the differential electrode of the slot, dynamically increase the loop gain to make the signal amplitude within the maximum effective range of the ADC, and then perform ADC conversion. Step 3, Synchronous Sampling and Data Transmission: The PPS signal output by the Beidou module serves as the trigger signal for the start of ADC sampling on different devices, achieving sampling synchronization across all devices; the MCU control chip adds a timestamp to the data converted by the ADC and transmits it back to the backend server in real time via the 4G module. Step 4, Server background data processing: The server receives waveform data, performs Fourier transform on it, obtains the initial phase, and stores the phase and time stamp together; Step 5, Phase line identification: Steps 1 to 3 are executed simultaneously at the power output terminal and the point to be measured to obtain waveform data from both. The server performs Fourier transform on the waveform data from both terminals to obtain the initial phase and calculate the phase difference. When the phase difference between the measuring point and the waveform of a certain output terminal is less than the preset allowable error X, it is determined that the phase line of the measuring point is consistent with the phase line of the output terminal.

2. The non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes according to claim 1, characterized in that, In step 1, the electric field acquisition uses a specific structure slot to achieve adaptive selection and tight integration of cables of different diameters with the corresponding slots; multiple pairs of differential electrode plates for acquiring electric field strength are distributed in the center of each slot segment to ensure that the cable and the electrode plates are aligned, thereby achieving signal acquisition.

3. The non-contact online low-voltage line phase sequence identification method based on multiple differential electrodes according to claim 1, characterized in that, The preset allowable error X in step 5 ranges from 0° to 1°.

4. The non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes according to claim 1, characterized in that, The dynamic adjustment gain range of the AGC circuit is determined based on the voltage signal strength range of the low-voltage line. Multiple pairs of differential electrodes are added to adaptively select the strongest signal and sense the signal that is closest to the measured phase line voltage waveform.

5. The non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes according to claim 1, characterized in that, The BeiDou module is also used to provide positioning information to the system and realize the associated storage of phase sequence recognition and location information.

6. A system for implementing the non-invasive online low-voltage line phase sequence identification method based on multiple differential electrodes as described in any one of claims 1-5, characterized in that, It includes an electric field sensor composed of multiple pairs of differential electrodes, an AGC circuit, an ADC, an MCU control chip, a Beidou module, a 4G module, and a back-end server; the electric field sensor is connected to the AGC circuit, the AGC circuit is connected to the ADC and the MCU control chip respectively, the ADC, the Beidou module, and the 4G module are connected to the MCU control chip respectively, and the 4G module is connected to the back-end server for communication.

7. The system according to claim 6, characterized in that, The electric field sensor uses multiple pairs of differential electrodes, arranged symmetrically on the left and right sides with a single-core cable as the center, and the AGC circuit is a variable gain amplifier.

8. The system according to claim 6, characterized in that, The ADC uses the AD7606BSTZ module.

9. The system according to claim 6, characterized in that, The BeiDou module uses the G28Z2FTTL module, and the 4G module uses the WH-GM5_C2833613 module.

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