Three-phase cable live state recognition device and method based on annular magnetic field sensing array

Abstract

The application discloses a three-phase cable live state recognition device and method based on a ring magnetic field sensing array, and belongs to the technical field of power system safety detection. The existing non-contact electricity testing method is difficult to distinguish the target cable body current and the adjacent loop coupling current, thus leading to misjudgment. The application adopts an openable and closable ring support which is sleeved on the outside of the cable, three magnetic field sensors are fixed on the inner side of the ring support in a circle, each magnetic field sensor is respectively aligned with the top of a corresponding phase conductor in the three-phase cable in space, so as to independently sense the power frequency magnetic field of each phase; the instantaneous phase of each signal is extracted and the phase difference between each other is calculated by processing the three-way synchronous collected signals; finally, according to the comparison result of the three phase differences and the preset criterion, the state of the cable is determined, such as normal live, external coupling interference, unlive and no significant external magnetic field interference. The technical scheme can effectively recognize the live state of the three-phase cable in a non-contact, fast and reliable manner.

Description

Technical Field

[0001] This invention relates to the field of power system safety detection technology, and in particular to a device and method for identifying the live state of three-phase cables based on a ring magnetic field sensing array. Background Technology

[0002] With the increasing cabling prevalence in urban power distribution networks, cross-linked polyethylene (XLPE) insulated cables have been widely used in power transmission and distribution systems. When inspecting, maintaining, or troubleshooting cable lines, quickly and accurately determining whether a cable is energized is a prerequisite for ensuring operational safety. Traditional voltage testing methods are mainly divided into two categories: one is contact voltage testing, which requires direct contact with the cable conductor or using a high-voltage detector near the exposed portion. This often necessitates power outages, affecting power supply reliability, and is difficult to implement without damaging the insulation layer for fully insulated shielded cables; the other is non-contact magnetic field detection, which indirectly determines the presence of current by measuring the amplitude of the power frequency magnetic field around the cable.

[0003] However, in typical environments with densely laid multi-circuit cables, such as cable trenches, tunnels, or cable trays, existing non-contact magnetic field detection methods face severe challenges. The target cable may be de-energized due to a power outage, but adjacent energized circuits can generate strong power frequency magnetic fields that couple to the area around the target cable. The amplitude of this coupled magnetic field generated by neighboring circuits can be on the same order of magnitude as the magnetic field generated when the target cable itself is energized. This makes traditional non-contact voltage detectors, which rely solely on the magnitude of the magnetic field amplitude, prone to misjudgment, falsely reporting a state of "de-energized but with coupling interference" as "energized," seriously threatening the safety of operators and their operational decisions.

[0004] Furthermore, while existing magnetic field detection technologies (such as Hall effect sensors and anisotropic magnetoresistive sensors) can detect the presence of magnetic fields, their deployment methods are typically single-point or asymmetrical measurements. These methods fail to fully consider the inherent spatial geometry and electromagnetic field characteristics of three-phase AC cables, and also fail to utilize the crucial characteristic of the phase difference between the three-phase currents. Therefore, existing technologies cannot fundamentally distinguish between magnetic fields originating from the target cable itself and having a specific phase relationship, and coupled magnetic fields from external sources that are typically in approximately the same phase. Summary of the Invention

[0005] The technical problem to be solved and the technical task proposed by this invention is to improve and refine existing technical solutions, and to provide a device and method for identifying the energized state of three-phase cables based on a ring magnetic field sensing array, aiming to achieve non-contact, rapid and highly reliable identification of the energized state of cables. To this end, this invention adopts the following technical solution.

[0006] In a first aspect, the present invention provides a three-phase cable energization status identification device based on a ring magnetic field sensing array, the three-phase cable energization status identification device comprising:

[0007] A ring-shaped bracket, which is an openable and closable ring structure, is used to be fitted onto the outside of a three-phase AC cable and is coaxially arranged with the cable;

[0008] The sensor array module includes three magnetic field sensors, which are fixedly arranged circumferentially in the annular bracket, such that when the annular bracket is fitted onto the cable, each magnetic field sensor is spatially aligned directly above the corresponding phase conductor of the three-phase cable.

[0009] The signal conditioning and acquisition module is connected to each magnetic field sensor in the sensor array module. It is used to perform low-noise amplification, power frequency bandpass filtering and analog-to-digital conversion on the analog magnetic field signals output by each magnetic field sensor, and output three digital magnetic field signals.

[0010] The digital processing and decision module, connected to the signal conditioning and acquisition module, is used to synchronously receive the three digital magnetic field signals and perform the following processing: extracting the power frequency component of each signal and calculating its instantaneous phase value; calculating the absolute value of the difference between any two of the three instantaneous phase values ​​to obtain three phase differences; comparing the three phase differences with a preset phase criterion to determine the energized state of the three-phase cable; the energized state includes: normal energized state, unenergized state but subject to interference from an external coupled magnetic field, and unenergized state with no significant magnetic field.

[0011] This technical solution combines spatial deployment with phase difference analysis to address the critical technical problem of unreliable cable energization in complex electromagnetic environments using traditional methods. Specifically, based on the core criterion of phase difference, it fundamentally distinguishes between the cable's intrinsic current and external coupling interference. Traditional non-contact detection methods rely on single-point magnetic field amplitude, which is prone to misjudgment under strong coupling magnetic field interference from nearby energized circuits. This solution utilizes the inherent 120° phase characteristic of a three-phase system, using the phase difference between the signals from three magnetic field sensors as the core criterion. This overcomes the fundamental problem of relying solely on amplitude to distinguish signal sources from a physical perspective, significantly improving the reliability and anti-interference capability of state identification in dense cable environments. By fixing the three magnetic field sensors on a ring bracket and ensuring that each sensor is aligned directly above the corresponding phase conductor of the three-phase cable after installation, each sensor can maximize the sensing of the magnetic field generated by the target phase current while minimizing direct interference from the other two phase magnetic fields. This lays a crucial physical foundation for extracting independent phase information that accurately reflects the characteristics of each phase current, and is a prerequisite for achieving precise phase difference analysis. The use of an openable ring-shaped bracket allows the device to be directly mounted on existing cables without the need for cable terminations, enabling non-destructive and rapid installation. Simultaneously, the bracket's coaxial alignment with the cable ensures symmetrical and stable spatial geometry of the three magnetic field sensors relative to the cable in the circumferential direction. This avoids inconsistencies in sensing conditions caused by installation eccentricity, thus guaranteeing the comparability and accuracy of measurement results. By simultaneously acquiring three digital magnetic field signals, extracting the power frequency component and instantaneous phase, and automatically calculating and comparing the phase difference, the device ultimately outputs a clear classification of the energized state (normal energization, coupling interference, no significant external magnetic field interference). This achieves automated and intelligent conversion from raw magnetic field signals to advanced state discrimination, reducing the possibility of manual intervention and misjudgment.

[0012] As a preferred technical means, the three magnetic field sensors are tunnel magnetoresistive sensors.

[0013] Employing a tunnel magnetoresistive (TMR) sensor significantly enhances the device's detection performance. The TMR magnetic field sensor boasts extremely high sensitivity, enabling precise measurement of even the weak power frequency magnetic field variations around the cable. Simultaneously, its excellent temperature stability and low power consumption ensure reliable long-term operation and measurement consistency in outdoor environments or cable tunnels with significant temperature variations. Compared to other magnetic sensing elements, the TMR magnetic field sensor exhibits superior linearity and low noise, providing a high-quality signal source foundation for subsequent high-precision phase extraction and difference calculation.

[0014] As a preferred technical means, the ring-shaped support is made of insulating non-metallic material.

[0015] It avoids the shielding and interference of the magnetic field by the metal bracket, and at the same time enhances electrical safety in high-voltage environments.

[0016] As a preferred technical means, the three magnetic field sensors are evenly distributed at 120° intervals along the circumference of the ring bracket.

[0017] The three magnetic field sensors are evenly distributed on the ring support at 120° intervals. This layout matches the symmetry of the three-phase power system, making the acquisition conditions of the three magnetic field signals comparable. This lays the foundation for subsequent fair and accurate phase difference comparison, effectively avoiding additional phase errors or amplitude deviations introduced by the asymmetrical spatial distribution of the magnetic field sensors, and improving the accuracy of state determination.

[0018] As a preferred technical means, the digital processing and decision module uses a digital lock-in amplification algorithm to extract the power frequency component and instantaneous phase value of the digital magnetic field signal.

[0019] A digital lock-in amplification algorithm is employed for signal processing, enhancing the system's noise immunity and phase detection accuracy. This algorithm can pinpoint and extract the weak 50Hz power frequency signal component from strong background noise (such as environmental electromagnetic noise and the background noise of the magnetic field sensor). By performing correlation calculations using an internally generated reference signal, the instantaneous amplitude and phase of the measured signal can be calculated, with a phase resolution far exceeding that of conventional zero-crossing detection methods. This ensures reliable and accurate acquisition of phase information from three magnetic field signals even in complex electromagnetic interference environments, providing a key technological guarantee for achieving a highly reliable phase difference criterion.

[0020] As a preferred technical means, the signal conditioning and acquisition module includes: a low-noise preamplifier connected to the output of each magnetic field sensor, a bandpass filter for filtering out frequency components other than 50Hz power frequency, and an analog-to-digital converter.

[0021] The low-noise preamplifier first amplifies the weak voltage signal output from the magnetic field sensor, its low-noise characteristics avoiding the introduction of excessive interference at the signal source. The bandpass filter effectively filters out high-frequency interference (such as radio noise and switching harmonics) and low-frequency drift beyond the 50Hz power frequency, improving the signal-to-noise ratio and resulting in a cleaner signal for subsequent processing. The analog-to-digital converter digitizes the signal, enabling advanced algorithms such as digital lock-in amplification. The entire chain works collaboratively to provide the system with a high-quality, highly stable digital magnetic field signal input.

[0022] As a preferred technical means, the preset phase criterion includes:

[0023] If all three phase differences are within the range of 100° to 140°, the three-phase cable is determined to be in a normal energized state.

[0024] If all three phase differences are within the range of 0° to 40°, the three-phase cable is determined to be in a state of being unenergized but subject to interference from an external coupled magnetic field.

[0025] The phase criterion used in this technical solution employs a threshold range (100°-140° corresponding to normal charging, 0°-40° corresponding to coupling interference), making the decision logic operable and fault-tolerant. Considering slight imbalances, magnetic field sensor errors, and installation deviations in actual measurements, appropriate margins are provided based on the theoretical values ​​of 120° and 0°, avoiding misjudgments caused by minor deviations. It can directly correspond to the two most important field conditions, clearly and reliably distinguishing between self-charging and external coupling—two states that may be similar in amplitude but are physically completely different.

[0026] As a preferred technical means: the digital processing and decision module is also used to calculate the amplitude of the three digital magnetic field signals; the preset phase criterion further includes: if the amplitude of the three digital magnetic field signals is lower than a preset amplitude threshold, and the three phase differences have no stable relationship, then it is determined that the three-phase cable is in a state of no power and no significant magnetic field.

[0027] This technical solution introduces amplitude as an auxiliary decision condition based on the phase difference criterion, thus improving the entire state identification system. It is specifically designed to identify the third state: "the cable is not energized and there is no strong coupled magnetic field around it." When the magnetic field amplitude is extremely weak (below the threshold) and the phase relationship is chaotic, it can be clearly determined that the cable is in a safe, de-energized state. This solves the problem that a single phase criterion may lead to inaccurate phase calculations and an inability to make a clear judgment when the magnetic field is extremely weak due to noise dominance. This further reduces the system's false alarm rate and false negative rate, making the state classification more complete and reliable.

[0028] Another technical solution of the present invention is to provide a method for identifying the energized state of a three-phase cable based on a ring magnetic field sensing array, which employs the aforementioned device and includes the following steps:

[0029] 1) Fit the ring bracket onto the three-phase cable to be identified, ensuring that the three magnetic field sensors are located directly above each phase conductor of the three-phase cable;

[0030] 2) The original magnetic field waveforms output by the three magnetic field sensors are acquired synchronously, and each signal is amplified, filtered and digitized to obtain three digital magnetic field signals;

[0031] 3) Extract the instantaneous phase of the power frequency component from the three digital magnetic field signals, denoted as . , , ;

[0032] 4) Calculation , , Three absolute phase differences;

[0033] 5) Compare the calculated three phase differences with the preset decision thresholds to make a comprehensive judgment on the energized state of the three-phase cable; if the three absolute phase differences all fall within the first preset range, the three phases are judged to be normally energized; if the three absolute phase differences all fall within the second preset range, the cable is judged to be not energized but there is coupling current interference from the adjacent circuit.

[0034] This technical solution transforms the problem of identifying the energized state of three-phase cables into a deterministic decision-making process based on multi-channel synchronous phase difference analysis, thereby achieving improved anti-interference capability, reliability, and operability. Specifically, this method first completes the spatial positioning of the magnetic field sensors, ensuring that each sensor is aligned with its corresponding phase conductor. This guarantees from the measurement source that each signal can reflect the magnetic field of the target phase to the greatest extent, providing a physical basis for subsequent independent phase analysis. Next, it requires the synchronous acquisition of three original waveforms (step 2), eliminating timing errors that may be introduced by time-division sampling, ensuring the acquired waveforms are accurate and reliable. , , This method provides a true snapshot of the three-phase magnetic fields at the same moment, ensuring strict simultaneity and comparability of the calculated phase differences. It abandons the traditional method of relying on amplitude magnitude for rough judgment. Steps 3) and 4) extract the instantaneous power frequency phase from the three digital magnetic field signals and calculate the absolute phase difference between each pair, fundamentally distinguishing the physical characteristics of "self-charged" and "externally coupled"—that is, the phase relationship of the magnetic field signals. This transforms the complex problem of electromagnetic field spatial distribution into an analysis of three distinct numerical values ​​(phase differences), making the judgment process highly focused and directional. Step 5) By simply and directly comparing the calculated three phase differences with a threshold range, a definitive conclusion of "normally charged" or "coupled interference" state can be output. The judgment logic is simple and efficient, avoiding fuzzy or complex calculations and reducing decision uncertainty. Furthermore, because the phase difference is insensitive to external uniform coupling fields but highly sensitive to the 120° relationship of the three-phase currents within the device, this criterion possesses inherent robustness when facing major interference sources (nearby cables).

[0035] As a preferred technical means, step 5) also includes amplitude-assisted decision-making:

[0036] Calculate the amplitude of the power frequency component of the three digital magnetic field signals;

[0037] If all three amplitude values ​​are lower than a preset amplitude threshold, and the phase difference of the three absolute values ​​does not show a stable 120° or 0° relationship, then it is determined that the cable is not energized and there is no significant external magnetic field interference.

[0038] This technical solution improves the entire state recognition system, especially demonstrating significant advantages when handling special boundary conditions such as "no signal" or "extremely weak signal". Specifically, in addition to phase logic, this technical solution establishes an independent judgment channel based on amplitude threshold. When the amplitudes of the three digital magnetic field signals are all below the preset threshold, it indicates that there is no influential power frequency magnetic field in the cable body and the surrounding environment. At this time, combined with the condition of "no stable phase difference relationship" for verification, the state of "not energized and without significant external magnetic field interference" can be clearly and reliably determined. Thus, it can clearly distinguish between the aforementioned "coupled interference" state (with a strong external magnetic field) and the "safe no-magnetic" state here, achieving full coverage recognition of all possible on-site conditions (normal energization, coupled interference, safe no-energization), making the logic system more complete. When the magnetic field signal is extremely weak (e.g., below the noise level), the extracted phase information may be entirely dominated by random noise, and the calculation results will lose physical meaning. This could lead to a random distribution of the calculated phase difference. If only the phase difference criterion is relied upon, such random results may accidentally fall into a preset range, thus causing misjudgment. This technical solution sets an amplitude pre-screening checkpoint to filter out such conditions with extremely low signal-to-noise ratios and guides the final "no significant magnetic field" judgment, thereby fundamentally avoiding the risk of phase misjudgment caused by noise and significantly improving the reliability and robustness of the system's judgment in low-signal scenarios. This technical solution first performs amplitude judgment (whether all values ​​are below the threshold), and then performs phase relationship verification on the signals that pass the initial screening (whether there is no stable relationship). This dual verification mechanism makes the determination of the "safe no-power" state more rigorous and prudent. It does not make a hasty conclusion based on a single amplitude condition, but requires that both the extremely low amplitude and the chaotic phase relationship be met simultaneously. This is highly consistent with the actual physical situation (the magnetic field measurement results in a truly passive environment are exactly like this), thus ensuring the high accuracy and reliability of the final judgment result. In summary, the main advantage of adding an amplitude-assisted decision step is that it specifically addresses the decision blind spot and risk issues in the system when detecting extremely weak magnetic fields. By introducing amplitude threshold judgment and dual verification logic, the method's state recognition system becomes more complete and its boundaries clearer, and it possesses highly reliable decision-making capabilities across the entire range (from strong signals to no signals).

[0039] Beneficial effects:

[0040] This invention has advantages such as simple structure, convenient installation, no need to strip insulation, strong anti-interference ability, and clear criteria. It is particularly suitable for environments with dense multi-circuit installations such as cable trenches, tunnels, and cable trays. Specifically:

[0041] (1) Strong spatial resolution capability - through independently deployed three-channel magnetic field sensors, the three-phase cables can be accurately distinguished;

[0042] (2) High reliability of discrimination - using the inherent 120° phase difference characteristic of the power frequency magnetic field to form robust phase criteria and energy criteria;

[0043] (3) Easy installation without damaging the insulation - the ring structure supports quick snap-fitting, without contacting the conductor, and does not affect the safety of the cable structure;

[0044] (4) Strong anti-interference capability - It can automatically identify the equal-phase magnetic field caused by external coupling current, thereby avoiding misjudgment;

[0045] (5) Wide range of applications - can be used in areas where traditional methods are difficult to operate, such as cable trenches, tunnels, cable trays, and direct-buried cable troughs. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the assembly structure of the device of the present invention.

[0047] Figure 2 This is a cross-sectional structural schematic diagram of the device of the present invention.

[0048] Figure 3 This is a partial structural disassembly diagram of the device of the present invention.

[0049] Figure 4 This is a system structure block diagram of the device of the present invention.

[0050] Figure 5 This is a flowchart illustrating the method of the present invention.

[0051] Figure 6 This is a graph showing the magnetic field signal of the current flowing through the cable to be tested.

[0052] Figure 7 This is a graph showing the magnetic field signal of the interfering cable carrying current.

[0053] In the diagram: 1. Ring bracket; 101. Magnetic field sensor housing cavity; 102. Semi-circular ring hoop; 103. Connecting part; 104. Screw; 2. Sensor array module; 201. Magnetic field sensor; 202. Connecting line; 3. Signal conditioning and acquisition module; 4. Digital processing and decision module; 5. Display and alarm module; 6. Cable. Detailed Implementation

[0054] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings.

[0055] Example 1

[0056] This embodiment provides a three-phase cable energization status identification device based on a ring magnetic field sensing array, such as... Figures 1-4 As shown, it includes a ring support 1, a sensor array module 2, a signal conditioning and acquisition module 3, a digital processing and decision module 4, and a display and alarm module 5.

[0057] I. Circular support 1:

[0058] like Figures 1-3 As shown, the annular bracket 1 is injection molded from insulating high-strength engineering plastic (such as PEEK or reinforced nylon). Its inner diameter can be customized according to the outer diameter of the target cable 6 to ensure good coaxiality with the cable 6 after installation. To facilitate connection with the cable 6, the annular bracket 1 is formed by two symmetrical semi-circular rings 102. The mating part of the semi-circular rings 102 extends axially to form a connecting part 103. The connecting part 103 can be connected by a connector, which can be a buckle; a screw 104; or a hinge on one side and a buckle on the other side, using a combination of both; of course, the connecting part 103 can also be omitted and the cable can be directly fixed by binding or other means.

[0059] Three magnetic field sensor receiving cavities 101 are provided on the annular bracket 1, which are distributed at 120° to fix the magnetic field sensor 201.

[0060] The ring bracket 1 adopts a non-metallic, openable, and coaxial design, which makes the spatial position relationship of the magnetic field sensor 201 accurate and easy to install without power outages.

[0061] II. Sensor Array Module 2:

[0062] The sensor array module 2 consists of three high-performance magnetic field sensors 201, which are fixed circumferentially within the magnetic field sensor housing cavity 101 of the annular bracket 1. The sensitive axis of each magnetic field sensor is radially aligned with the center of the cable 6, and each magnetic field sensor 201 is spatially aligned directly above (i.e., the radially closest point) of the corresponding phase conductor of the three-phase cable 6, so as to achieve independent sensing of the power frequency magnetic field of each phase. The signal from the magnetic field sensor 201 is led out to the signal conditioning and acquisition module 3 through the connecting line 202. In this embodiment, the magnetic field sensor 201 is a tunnel magnetoresistive sensor (TMR).

[0063] III. Signal Conditioning and Acquisition Module 3:

[0064] Connected to each magnetic field sensor 201 in the sensor array module 2, it contains three identical signal channels. Each channel includes: a low-noise preamplifier for amplifying the weak differential signal output by the magnetic field sensor; a bandpass filter with a center frequency of 50Hz for filtering out interference other than power frequency; and a high-precision analog-to-digital converter (ADC) for synchronously sampling and digitizing the signal, ultimately outputting three digital magnetic field signals.

[0065] IV. Digital Processing and Decision Module 4:

[0066] Connected to signal conditioning and acquisition module 3, it is used to synchronously receive three digital magnetic field signals and perform the following processing:

[0067] Feature extraction: A digital lock-in amplification algorithm is used to accurately extract the instantaneous phase and amplitude of the 50Hz power frequency component from each signal. The power frequency component of each signal is extracted, and its instantaneous phase value is calculated.

[0068] Phase difference calculation: Calculate the absolute value of the difference between any two of the three instantaneous phase values ​​to obtain the three phase differences;

[0069] State determination: The energized state of the three-phase cable 6 is determined by comparing the three phase differences with preset phase criteria. The energized states include: normal energized state, unenergized state but subject to external coupled magnetic field interference, and unenergized state with no significant magnetic field interference. If all three phase differences are close to 120° (tolerance ±20°), the three-phase cable 6 is determined to be in a normal energized state. If all the phase differences are close to 0° (tolerance ±20°), the three-phase cable 6 is determined to be in an unenergized state but subject to external coupled magnetic field interference. If the measured signal amplitude is abnormally low (can be set to below 50nT) and there is no stable phase relationship, the cable 6 is determined to be unenergized and without significant external magnetic field interference.

[0070] V. Display and Alarm Module 5:

[0071] This module includes an LCD display, an audible and visual alarm, and a wireless communication module (such as 4G / LoRa). It receives judgment result instructions from the digital processing and judgment module 4, performs human-computer interaction and remote alarm, and is the external manifestation of the "real-time alarm" function.

[0072] Example 2

[0073] A method for identifying the live state of three-phase cables based on a ring magnetic field sensing array is provided, such as... Figure 5 As shown, it includes the following steps:

[0074] S1. Magnetic field sensor deployment:

[0075] Fit the ring bracket 1 onto the outside of the three-phase AC cable 6 to be identified. Adjust and ensure that the three magnetic field sensors 201 are spatially aligned directly above the A-phase, B-phase, and C-phase conductors of the cable 6, respectively. Ensure that the bracket is coaxial with the cable.

[0076] S2. Magnetic field signal acquisition and processing:

[0077] The data acquisition is initiated synchronously, with three magnetic field sensors 201 simultaneously acquiring the original power frequency magnetic field simulation signals from their respective locations. For example... Figure 6 The diagram shows the original magnetic field waveform output by the magnetic field sensor 201 when cable 6 is normally energized. It can be seen that the amplitudes of the three-phase waveforms are similar, with a phase difference of approximately 120°. Each signal first enters the signal conditioning and acquisition module 3 for preprocessing: it is initially amplified by a low-noise preamplifier to improve the signal-to-noise ratio; then it passes through a bandpass filter with a center frequency of 50Hz to filter out interference such as power grid harmonics and radio frequencies; finally, it undergoes synchronous sampling and digitization through a high-precision analog-to-digital converter, outputting three synchronous time-domain digital signals. , , This step ensures the high quality and timing consistency of the data used in subsequent processing.

[0078] S3. Instantaneous phase extraction of power frequency component:

[0079] The digital processing and decision module 4 receives three digital signals. To accurately extract the power frequency (50Hz) component and its instantaneous phase of each signal, this embodiment employs a digital phase-locked loop (PLL) amplification algorithm. Taking phase A signal as an example, the algorithm generates a pair of orthogonal 50Hz digital reference signals. and , respectively with Perform digital correlation calculations to determine the in-phase component of the 50Hz component in the signal. and orthogonal components Subsequently, through the formula Calculate its instantaneous phase value (usually normalized to the range of 0°-360°). Similarly, the instantaneous phases of phases B and C can be calculated. and This algorithm can robustly extract weak power frequency phase information from strong background noise.

[0080] S4. Calculate the three-phase phase difference:

[0081] Based on the extracted instantaneous phase , , Calculate the absolute phase difference between each pair of the three pairs:

[0082] ;

[0083] ;

[0084] ;

[0085] This group , , The data directly reflects the temporal relationship between the three-phase magnetic fields and is the core characteristic quantity for state discrimination in this method.

[0086] S5. State determination based on phase and amplitude:

[0087] First, perform the phase difference main criterion judgment:

[0088] If the three phase differences , , If all angles fall within the range of 100° to 140°, the three-phase cable is considered to be normally energized. Figure 3 As shown in the phase relationship, this state corresponds to the three-phase current of the body operating in balance.

[0089] If all three phase differences fall within the range of 0° to 40°, it is determined that the cable is not energized but there is external coupled magnetic field interference from a nearby circuit. In this state, the external uniform coupled magnetic field makes the signals measured by the three magnetic field sensors nearly in phase.

[0090] Secondly, amplitude auxiliary criteria are used to supplement and verify the main criteria:

[0091] Digital processing and decision module 4 simultaneously calculates the amplitude of the power frequency components of the three digital magnetic field signals. , , .

[0092] If all three amplitudes are below the preset amplitude threshold (e.g., 50 nT), and the three phase differences do not satisfy either the 120° or 0° relationship (i.e., the data is scattered and there is no stable phase relationship), then the final judgment is that the cable is not energized and there is no significant external magnetic field interference. This criterion effectively avoids phase misjudgment that may occur when the signal is extremely weak and noise dominates.

[0093] S6. Results Output and Alerts:

[0094] The judgment result is output via display and alarm module 5. If the judgment is "normally energized", the display screen will brighten and emit a continuous beep; if the judgment is "not energized but subject to external coupled magnetic field interference" or "not energized and without significant magnetic field", the corresponding safety status prompt will be displayed. The result can also be uploaded to the remote monitoring center via the communication module.

[0095] Based on the spatial symmetry of the ring magnetic field sensing array and the physical characteristics of the three-phase electromagnetic field, this invention realizes a highly reliable non-contact voltage detection scheme, which is especially suitable for cable live identification in multi-circuit parallel environments.

[0096] The following describes the specific experiments used in this embodiment:

[0097] Experimental process

[0098] I. Experimental Objective

[0099] This experiment aims to verify the function and reliability of a three-phase cable live-state detection device based on a ring magnetic field sensor array, focusing on:

[0100] Can the device accurately determine the energized state of the three-phase cable requiring voltage testing?

[0101] When the device generates magnetic field interference from the interference cable below, can it distinguish between the device itself being charged and the coupled magnetic field?

[0102] II. Experimental Apparatus and Equipment

[0103] Experimental cable layout

[0104] Cables requiring voltage testing: Three-phase high-voltage AC cables (A, B, and C phases), equipped with a ring magnetic field sensor array device;

[0105] Interference cable: Three-phase high-voltage AC cable (A, B, and C phases), approximately 40cm away from the cable to be tested, and arranged in parallel;

[0106] Ring magnetic field sensing array voltage detector

[0107] Three magnetic field sensors are fixed on a ring bracket, each positioned directly above the phase of the cable to be tested.

[0108] Current source

[0109] A controllable three-phase AC current generator with a 120° phase difference between each phase, providing precise current magnitude.

[0110] III. Experimental Procedure

[0111] Step 1: Device Installation and Initial Calibration

[0112] Attach the ring bracket to the outside of the cable to be tested, ensuring that the three magnetic field sensors are located directly above the A, B, and C phase cables, respectively.

[0113] The three magnetic field signal outputs were confirmed to be normal, with stable amplitude and phase, and synchronized signal sampling.

[0114] Step 2: Live-line test of the cable to be tested

[0115] The cable to be tested is powered by a three-phase AC power supply, with each phase current set to 20 Arms and the three phases being 0°, -120°, and +120° respectively.

[0116] The magnetic field signals from three magnetic field sensors are acquired in real time, and the data is recorded for a period of 20 seconds.

[0117] Amplitude analysis and instantaneous phase calculation were performed on the three digital magnetic field signals to verify whether they met the characteristic of approximately 120° phase difference between the three phases.

[0118] Based on the device's algorithm, determine the energized state of the cable to be tested and record the device's output results.

[0119] Step 3: Interference cable energization test (interference verification)

[0120] The cable to be tested must be de-energized, while the interference cable is energized at the same time, with a current of 30 Arms per phase and three phases of 0°, -120° and +120° respectively.

[0121] The synchronous acquisition device acquires three magnetic field signals and records data for a period of 20 seconds.

[0122] Amplitude analysis and phase calculation were performed on the three digital magnetic field signals to observe the effect of magnetic field coupling of the lower cable on the upper device.

[0123] The device identifies the energized state of the overhead cable based on phase criteria and outputs the determination result.

[0124] IV. Results Analysis

[0125] During the experiment, when the cable to be tested was energized with a current of 20 Arms per phase, the phase difference of the three magnetic field signals acquired by the ring magnetic field sensor array was approximately 120°, with amplitudes of 5369 nT, 3482 nT, and 3163 nT, respectively. This result is consistent with theoretical analysis, clearly demonstrating that each magnetic field sensor is primarily dominated by the magnetic field of the corresponding phase current directly below it, and the inherent 120° phase difference of the three-phase current is accurately reflected in the acquired signals. This verifies the device's independent ability to determine the energized state of the three-phase cable and its phase extraction accuracy. Figure 6 As shown.

[0126] When the interfering cable carries a 30 Arms / phase current, the phase difference of the three magnetic field signals acquired by the device is approximately 0°, with amplitudes of 178 nT, 143 nT, and 116 nT, respectively. These amplitudes are significantly lower than the signals when the cable being tested is energized, and the three digital magnetic field signals are essentially in phase, indicating that the magnetic field of the interfering cable primarily acts on the measuring device through coupling interference, but does not form a definable 120° phase difference. This demonstrates that the ring magnetic field sensing array device can effectively distinguish between the dominant magnetic field of the cable directly below it and the coupled magnetic field generated by neighboring cables, thus avoiding misjudgment. Figure 7 As shown.

[0127] Based on the above data analysis, we can conclude that:

[0128] When the cable to be tested is energized, the device can accurately identify the three-phase energized state and phase relationship;

[0129] The device can distinguish between the dominant magnetic field and coupled interference when the nearby cable is energized, thus maintaining the accuracy of the energization determination.

[0130] The amplitude differences and phase characteristics of the three magnetic fields all meet the theoretical expectations, fully verifying the device's three-phase independent detection capability and anti-interference performance.

[0131] The above-described specific embodiments of the present invention demonstrate the substantial features and advancements of the present invention. Equivalent modifications can be made to these embodiments based on actual usage needs and the guidance of the present invention are all within the scope of protection of this solution.

Claims

1. A three-phase cable energization status identification device based on a ring magnetic field sensing array, characterized in that, include: A ring-shaped bracket, which is an openable and closable ring structure, is used to be fitted onto the outside of a three-phase AC cable and is coaxially arranged with the cable; The sensor array module includes three magnetic field sensors, which are fixedly arranged circumferentially in the annular bracket, such that when the annular bracket is fitted onto the cable, each magnetic field sensor is spatially aligned directly above the corresponding phase conductor of the three-phase cable. The signal conditioning and acquisition module is connected to each magnetic field sensor in the sensor array module. It is used to perform low-noise amplification, power frequency bandpass filtering and analog-to-digital conversion on the analog magnetic field signals output by each magnetic field sensor, and output three digital magnetic field signals. The digital processing and decision module, connected to the signal conditioning and acquisition module, is used to synchronously receive the three digital magnetic field signals and perform the following processing: extract the power frequency component of each signal and calculate its instantaneous phase value; calculate the absolute value of the difference between any two of the three instantaneous phase values ​​to obtain the three phase differences; The energized state of the three-phase cable is determined by comparing the three phase differences with a preset phase criterion. The charged states include: normal charged state, uncharged state but subject to interference from external coupled magnetic field, and uncharged state with no significant magnetic field. The preset phase criteria include: If all three phase differences are within the range of 100° to 140°, the three-phase cable is determined to be in a normal energized state. If all three phase differences are within the range of 0° to 40°, the three-phase cable is determined to be in a state of being unenergized but subject to interference from an external coupled magnetic field.

2. The three-phase cable energization status identification device based on a ring magnetic field sensing array according to claim 1, characterized in that: The three magnetic field sensors are tunnel magnetoresistive sensors.

3. The three-phase cable energization status identification device based on a ring magnetic field sensing array according to claim 1, characterized in that: The ring-shaped support is made of insulating non-metallic material.

4. The three-phase cable energization status identification device based on a ring magnetic field sensing array according to claim 1, characterized in that: The three magnetic field sensors are evenly distributed at 120° intervals along the circumference of the ring bracket.

5. The three-phase cable energization status identification device based on a ring magnetic field sensing array according to claim 1, characterized in that: The digital processing and decision module uses a digital lock-in amplification algorithm to extract the power frequency component and instantaneous phase value of the digital magnetic field signal.

6. The three-phase cable energization status identification device based on a ring magnetic field sensing array according to claim 1, characterized in that: The signal conditioning and acquisition module includes: a low-noise preamplifier connected to the output of each magnetic field sensor, a bandpass filter for filtering out frequency components other than 50Hz power frequency, and an analog-to-digital converter.

7. The three-phase cable energization status identification device based on a ring magnetic field sensing array according to claim 1, characterized in that: The digital processing and decision module is also used to calculate the amplitude of the three digital magnetic field signals; the preset phase criterion further includes: if the amplitude of the three digital magnetic field signals is lower than a preset amplitude threshold and the three phase differences have no stable relationship, then it is determined that the three-phase cable is in a state of no power and no significant magnetic field.

8. A method for identifying the live state of three-phase cables based on a ring magnetic field sensing array, characterized in that: Using the apparatus as described in any one of claims 1 to 7, and comprising the following steps: 1) Fit the ring bracket onto the three-phase cable to be identified, ensuring that the three magnetic field sensors are located directly above each phase conductor of the three-phase cable; 2) The original magnetic field waveforms output by the three magnetic field sensors are acquired synchronously, and each signal is amplified, filtered and digitized to obtain three digital magnetic field signals; 3) Extract the instantaneous phase of the power frequency component from the three digital magnetic field signals, denoted as . , , ; 4) Calculation , , Three absolute phase differences; 5) Compare the calculated three phase differences with the preset decision thresholds to make a comprehensive judgment on the energized state of the three-phase cable; if the three absolute phase differences all fall within the first preset range, the three phases are judged to be normally energized; if the three absolute phase differences all fall within the second preset range, the cable is judged to be not energized but there is coupling current interference from the adjacent circuit.

9. The method for identifying the energized state of a three-phase cable based on a ring magnetic field sensing array according to claim 8, characterized in that: Step 5) also includes amplitude-assisted decision-making: Calculate the amplitude of the power frequency component of the three digital magnetic field signals; If all three amplitude values ​​are lower than a preset amplitude threshold, and the phase difference of the three absolute values ​​does not show a stable 120° or 0° relationship, then it is determined that the cable is not energized and there is no significant external magnetic field interference.

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