Dynamic frequency variation tracking live detection device

Abstract

The application belongs to the technical field of power system experiment, and relates to a dynamic frequency variation tracking live detection device, which comprises a main control module, a double-differential electric field coupling module, an ultrahigh resistance steady-state acquisition module, a differential amplification and signal conditioning module and a steady-state discrimination module; the double-differential electric field coupling module is used for forming two or more groups of coupling potential signals with different spatial positions under the action of a space electrostatic field around a measured conductor; the ultrahigh resistance steady-state acquisition module is connected with the double-differential electric field coupling module; the differential amplification and signal conditioning module is connected with the ultrahigh resistance steady-state acquisition module; and the steady-state discrimination module is connected with the differential amplification and signal conditioning module. The application introduces an ultrahigh resistance steady-state maintaining structure at an electric field coupling end, suppresses coupling charge discharge, and enables the coupling potential formed by the space electrostatic field under ultralow frequency and quasi-static conditions to exist stably, so that reliable identification of a direct current and an ultralow frequency live state is realized.

Description

Technical Field

[0001] This invention belongs to the field of power system experimental technology, and in particular relates to a non-contact live-line testing device for ultra-low frequency applications, suitable for high-voltage transmission, ultra-low frequency withstand voltage testing of cables, and unattended substations. Background Technology

[0002] With the rapid development of the power industry and the widespread application of ultra-high voltage direct current technology, ultra-low frequency withstand voltage testing is becoming increasingly important in power equipment inspection. As a core piece of equipment for safe operation in power systems, the performance of voltage testing devices directly affects the safety of operators and the stability of equipment operation. The core function of voltage testing devices is to provide safety warnings to operators by detecting the energized state of conductors, thus preventing electric shock and equipment damage accidents.

[0003] Meanwhile, in ultra-low frequency and quasi-static electric fields, only extremely weak static coupling charges are formed between the electrode and the conductor being measured. Any input impedance below 10¹²Ω will cause the coupling charges to dissipate rapidly within a time constant (τ=Rin・Ceq), making the sensor output approach zero and unable to form a discriminable signal. In substations, converter stations, and other similar scenarios, there are power frequency common-mode interference (the electric field strength at 50Hz can reach 10kV / m), corona discharge noise, and high-frequency radio interference. Traditional single-electrode structures lack common-mode rejection capability, have insufficient input impedance (usually below 100MΩ), cannot preserve μV-level weak coupling signals, and are susceptible to the influence of stray electric fields, leading to signal drift, high misjudgment rate, and inability to output stable and reliable detection results. Furthermore, existing technologies rely on electric field or voltage change rate to obtain signals, resulting in displacement current approaching zero under ultra-low frequency conditions and rapid discharge of coupled charges, making it impossible to form a stable detection signal. In addition, some non-contact voltage testing devices rely on the human body or external grounding as a reference, which limits their detection distance and makes them highly directional. In GIS equipment, high-altitude lines, and unattended scenarios, their operational safety margin is insufficient, making it difficult to meet the actual needs of voltage testing for DC and ultra-low frequency power equipment.

[0004] Therefore, it is necessary to design a non-contact voltage testing device that is suitable for ultra-low frequency scenarios, has strong anti-interference capabilities, long detection distance, and is easy to operate, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a dynamic frequency-varying tracking charged detection device. By introducing an ultra-high resistance steady-state holding structure at the electric field coupling end, the discharge of coupled charge is suppressed (satisfying τ≥1 / (2f)), so that the coupling potential formed by the spatial electrostatic field under ultra-low frequency and quasi-static conditions can be stably maintained, thereby realizing reliable identification of DC and 0.1Hz~1Hz ultra-low frequency charged states, and improving the safety and reliability of voltage detection in complex power operation environments.

[0006] The dynamic frequency-changing tracking live detection device includes a wireless communication module, an audible and visual alarm module, a mounting base and a protective housing; it also includes a main control module, a dual differential electric field coupling module, an ultra-high impedance steady-state acquisition module, a differential amplification and signal conditioning module and a steady-state discrimination module.

[0007] The dual differential electric field coupling module is used to generate two or more sets of coupled potential signals with different spatial positions under the action of the spatial electrostatic field around the conductor being measured.

[0008] The ultra-high impedance steady-state acquisition module is connected to the dual differential electric field coupling module, which is used to suppress the discharge of coupled charge and maintain the steady-state existence of the coupled potential signal under ultra-low frequency or quasi-static electric field conditions.

[0009] The differential amplification and signal conditioning module is connected to the ultra-high impedance steady-state acquisition module and is used to perform differential enhancement and low-frequency processing on the steady-state coupled potential signal;

[0010] The steady-state discrimination module is connected to the differential amplification and signal conditioning module and is used to output the charged state of the conductor under test based on the time stability characteristics of the steady-state coupled potential signal.

[0011] The main control module is electrically connected to the differential amplification and signal conditioning module, the steady-state discrimination module, the wireless communication module, and the audible and visual alarm module, and integrates data processing, logic control, and command issuance functions.

[0012] The dual differential electric field coupling module includes four or more electric field coupling electrodes, which form two sets of differential electrode pairs arranged opposite each other in space. Each differential electrode pair is used to sense the coupling potential formed by the spatial electrostatic field around the conductor under test at different positions. The unbalanced distribution characteristics of the spatial electrostatic field are characterized by the steady-state potential difference between each differential electrode pair.

[0013] The ultra-high impedance steady-state acquisition module includes an ultra-high impedance pre-hold structure, with an equivalent input impedance higher than 10 Ω. 13 Ω is set at the output end of the electric field coupling electrode, and works in conjunction with the dual differential electrode to ensure that the spatial unbalanced coupling potential is stably retained in the ultra-low frequency time scale.

[0014] The ultra-high impedance steady-state acquisition module also includes an input protection diode, which is a dual series diode with a withstand voltage of 85V, connected in parallel on both sides of the amplifier input terminal to protect against transient overvoltage.

[0015] The differential amplification and signal conditioning module is configured to operate in low-frequency or ultra-low-frequency mode, with a passband upper limit of less than 5Hz, in order to suppress interference signals in the power frequency and above frequency bands while maintaining steady-state coupling potential information.

[0016] The steady-state discrimination module makes a judgment based on the amplitude stability, change slope and statistical fluctuation characteristics of the steady-state coupled potential signal within a preset time window. When the steady-state coupled potential signal meets the stability criterion within the time window, it outputs the judgment result that the conductor under test is in a charged state.

[0017] The electric field coupling electrode is a nickel-plated copper sheet in the shape of a 150° arc, with dimensions of 50mm in height, 30mm in radius, and 1mm in thickness. The two sets of differential electrodes are symmetrically arranged on the mounting base with a spacing of 2mm between them. The electrode surfaces are passivated and the edges are designed with a radius of 2mm. The inner side of the electrodes is filled with epoxy resin LEDO6060 insulating medium, and the relative positions of the four electrodes are fixed by an integrally molded epoxy resin insulating bracket.

[0018] The ultra-high impedance pre-holding structure includes a leakage current suppression resistor pre-circuit, wherein the leakage current suppression resistor circuit adopts a 10¹ 4 The Ω ultra-high impedance chip forms a pre-amplifier non-inverting circuit, which is connected in series between the output terminals of each electrode and the input terminal of the differential amplifier to ensure that the equivalent input impedance is not less than 10¹³Ω.

[0019] The differential amplifier in the differential amplification and signal conditioning module adopts a two-stage amplification structure, with the first-stage amplification factor set to 10 times and the second-stage amplification factor set to 10 to 100 times, and the total differential gain A_d = 100 to 1000 times; the filter circuit adopts a second-order RC low-pass filter structure with a cutoff frequency of 0.5Hz; the differential amplifier is configured with an input impedance ≥10GΩ, an input bias current ≤3pA, and an equivalent noise voltage ≤10nV / √Hz.

[0020] A non-contact voltage detection method based on dual differential coupling, using the aforementioned dynamic frequency-changing tracking live-line detection device, includes the following steps:

[0021] Step 1: Device installation: Fix the device at a distance of 20-30cm from the conductor to be tested using the mounting base, adjust the device so that the dual differential electrodes are facing the conductor to be tested, and complete the self-test after turning on the power.

[0022] Step 2: Signal Coupling: The electrostatic field formed by the conductor under test acts on the dual differential electrodes. The upper outer electrode and the upper inner electrode generate the first differential signal Vd1=(k1-k2)Vm, and the lower outer electrode and the lower inner electrode generate the second differential signal Vd2=(k3-k4)Vm. The two sets of signals are synchronously input into the ultra-high impedance steady-state acquisition module.

[0023] Step 3: Steady-state holding and signal conditioning: The ultra-high impedance pre-hold structure suppresses coupled charge discharge and maintains signal steady state; the input protection diode prevents transient impact; the differential amplifier amplifies the μV-level differential signal to the mV level, and after being filtered by a second-order RC low-pass filter to remove interference in the power frequency and above frequency bands, it is output to the main control module.

[0024] Step 4: Steady-state identification: The ADC unit of the main control module acquires the amplified signal at a rate of 200 SPS, suppresses power frequency interference through the IIR filter unit, and the multi-dimensional criterion unit outputs three states: charged, uncharged, and abnormal interference through variance calculation, slope analysis, time window consistency determination and interference identification.

[0025] Step 5: Warning and Communication: If the circuit is determined to be live, the audible and visual alarm module will be activated, and the wireless communication module will push the live information to the background system; if the circuit is determined to be abnormal, the LED light will flash and the buzzer will sound continuously, prompting you to check the source of interference.

[0026] Through the above design scheme, the present invention can bring the following beneficial effects:

[0027] Breakthrough in low-frequency detection limitations: Based on the principle of electrostatic coupling and the steady-state holding mechanism of ultra-high impedance, and without relying on displacement current or dV / dt, the detection of ultra-low frequency voltages from 0.1Hz to 1Hz has been successfully achieved, solving the core problem that existing devices cannot detect ultra-low frequency voltages. Experimental verification shows that under conditions of 0.1Hz, 10kVAC voltage, and a distance of 30cm, a stable output of a 165μV differential signal can be achieved, meeting the voltage detection requirements for ultra-low frequency scenarios.

[0028] Strong anti-interference capability: The dual-differential structure achieves a common-mode rejection ratio (CMRR) of 80–100 dB. Combined with an ultra-high impedance acquisition module (input impedance ≥10 GΩ) and digital filtering technology, it can effectively filter power frequency interference, corona noise, and high-frequency radio signals. In the strong interference environment of substations, the steady-state measurement error is ≤±0.69%, and the phase error is only 0.17°–0.86°, which is far superior to the traditional single-electrode structure.

[0029] Safe and convenient operation features: The detection distance is increased to 20-30cm, which greatly improves the safety margin compared with traditional devices (3-10cm); no human body grounding is required, and the directional limitation is small (normal detection is still possible even with an angle deviation of ≤45°), making it suitable for complex scenarios such as GIS equipment and high-altitude lines.

[0030] Multi-scenario adaptability: The low-power design supports 72 hours of standby time, and the wireless communication function enables remote monitoring in unattended scenarios. It can be widely used in power operation scenarios such as DC converter stations, cable withstand voltage tests, and distribution cabinet inspections, and has strong adaptability. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0032] Figure 1 This is a schematic diagram illustrating the structural principle of the dynamic frequency-changing tracking charged detection device of the present invention.

[0033] Figure 2 This is a cross-sectional view of the structure of the dual differential electric field coupling module of the present invention.

[0034] Figure 3 This is a schematic diagram of the in-phase circuit of the ultra-high impedance steady-state acquisition module of the present invention.

[0035] Figure 4 This is a schematic diagram of the steady-state identification process of the dynamic frequency-changing tracking charged detection device of the present invention.

[0036] Figure 5 This is a schematic diagram of the equivalent circuit of the dynamic frequency-changing tracking charged detection device of the present invention.

[0037] Figure 2 In the middle: 1-Insulating support, 2-Inner upper electrode, 3-Outer upper electrode, 4-Inner lower electrode, 5-Outer lower electrode.

[0038] Figure 5 In the diagram: Cm1, Cm2, Cm3, and Cm4 are the mutual capacitances between the electrodes and the conductor under test; Cs1, Cs2, Cs3, and Cs4 are the stray capacitances from the electrodes to ground; Cm12 and Cm34 are the mutual capacitances between the two pairs of electrodes; R1 and R2 are the equivalent resistances of the ultra-high impedance chip input. Detailed Implementation

[0039] Dynamic frequency-conversion tracking live-line detection device, such as Figures 1-5 As shown, it includes a dual differential electric field coupling module, an ultra-high impedance steady-state acquisition module, a differential amplification and signal conditioning module, a steady-state discrimination module, a main control module, a wireless communication module, an audible and visual alarm module, a mounting base, and a protective housing.

[0040] Among them, the signal output terminal of the dual differential electric field coupling module is connected to the ultra-high impedance steady-state acquisition module to form coupling potential signals with different spatial positions;

[0041] The ultra-high impedance steady-state acquisition module is connected to the differential amplifier and signal conditioning module to achieve charge discharge suppression, signal steady-state maintenance and differential enhancement.

[0042] The differential amplification and signal conditioning module is connected to the steady-state discrimination module to provide a conditioned signal for steady-state determination;

[0043] The main control module is electrically connected to the differential amplification and signal conditioning module, the steady-state discrimination module, the wireless communication module, and the audible and visual alarm module, integrating data processing, logic control, and command issuance functions. The main control module and each functional module are fixed on the mounting base, and the protective shell is sealed to the mounting base with bolts to achieve the protection function.

[0044] Under ultra-low frequency and quasi-DC electric field conditions, the electric field around the conductor under test changes extremely slowly. The electric field coupling electrode and the conductor under test are mainly connected by capacitive coupling through the spatial electrostatic field. This coupling relationship can be equivalent to the mutual capacitance (Cmi) between the electrode and the conductor under test, where (i) represents different electric field coupling electrodes.

[0045] When the conductor under test is in a charged state (potential is Vm), the coupling charge formed on the (i)th electric field coupling electrode can be expressed as: Qi = Cmi・Vm (i = 1, 2, 3, 4), where: (Qi) is the coupling charge on the i-th electrode, and (Cmi) is the equivalent mutual capacitance between the electrode and the conductor under test.

[0046] The actual potential of an electrode node is affected by the mutual capacitance (Cmi), the stray capacitance to ground (Csi), and the equivalent capacitance of the acquisition terminal input (Cin). Its steady-state coupling potential can be expressed as: Vi = Qi / (Cmi + Csi + Cin). Substituting the coupling charge formula and combining it with the defined electrode coupling coefficient (ki = Cmi / (Cmi + Csi + Cin)), it can be simplified to: Vi = ki・Vm.

[0047] Since the coupled charge at the electrode nodes is discharged to the reference ground through the input impedance of the acquisition terminal, its charge retention capability is determined by the time constant, i.e.: τ = Rin・Ceq (where Rin is the equivalent input impedance of the ultra-high impedance steady-state acquisition module, and Ceq = Cmi + Csi + Cin is the equivalent capacitance of the electrode node). To ensure the stability of the steady-state coupling potential within the detection timescale, the charge retention time constant must be on the same order of magnitude as the period of the measured signal, i.e.: τ ≥ 1 / (2f) (where f is the frequency of the measured signal). Taking the 0.1Hz ultra-low frequency condition as an example, the minimum time constant requirement is τ ≥ 5s; when Ceq is on the order of 10^-13F, the input impedance of the acquisition terminal must be no less than 5 × 10^13 Ω. Therefore, this invention adopts an ultra-high impedance steady-state acquisition structure with an equivalent input impedance of no less than 10^13 Ω.

[0048] To further suppress environmental interference and enhance the ability to extract spatial electric field imbalance distribution, this invention employs a dual differential electric field coupling structure. Let the coupling coefficients of the four electrodes be k1, k2, k3, and k4, respectively. Then, the steady-state outputs of the two sets of differential electrodes are: Vd1 = (k1-k2)・Vm, Vd2 = (k3-k4)・Vm. After processing by the differential amplification and signal conditioning module, the final steady-state output of the system is: Vout = G・[(k1-k2)-(k3-k4)]・Vm (G is the steady-state gain coefficient). By extracting the steady-state characteristics of spatial electric field imbalance, reliable determination of the charged state of the measured conductor is achieved.

[0049] Furthermore, the dual differential electric field coupling module includes an outer upper electrode 3, an inner upper electrode 2, an outer lower electrode 5, an inner lower electrode 4, and an insulating support 1. The outer upper electrode 3 and the inner upper electrode 2 are arranged in parallel to form a first differential pair, and the outer lower electrode 5 and the inner lower electrode 4 are arranged in parallel to form a second differential pair. The two sets of differential pairs are symmetrical about the center of the mounting base to ensure the symmetry and stability of the electric field coupling. The electrode spacing is set to 2mm, and the electrodes are made of nickel-plated copper sheets, designed as a 150° arc structure with a height of 50mm, a radius of 30mm, and a thickness of 1mm, which ensures both coupling area and ease of installation. The electrode surface is passivated to reduce the influence of corona discharge, and the electrode edges are designed with R2mm rounded corners to avoid electric field concentration. The inner side of the electrodes is filled with LEDO6060 insulating medium, and the insulating support 1 is integrally molded with epoxy resin to fix the relative positions of the four electrodes and prevent vibration from causing the coupling coefficient to shift.

[0050] Furthermore, the ultra-high impedance steady-state acquisition module and the differential amplification and signal conditioning module are integrated to form a functional unit, including a leakage current suppression resistor pre-amplifier circuit, an input protection diode, a high-precision differential amplifier, and a filter circuit. The leakage current suppression resistor circuit uses a 10¹... 4 An Ω ultra-high impedance chip forms a pre-amplifier non-inverting circuit, connected in series between the output terminals of each electrode and the input terminal of the differential amplifier, forming an ultra-high impedance pre-amplifier holding structure with an equivalent input impedance of not less than 10¹³Ω, effectively suppressing signal attenuation and charge discharge, and extending the charge hold time constant. The input protection diode uses dual series diodes with a withstand voltage of 85V, connected in parallel on both sides of the amplifier input terminal to protect against transient overvoltages. The differential amplifier is configured with an input impedance ≥10GΩ, input bias current ≤3pA, and equivalent noise voltage ≤10nV / √Hz to meet the requirements of ultra-low frequency weak signal acquisition. The filtering circuit adopts a second-order RC low-pass filter structure with a cutoff frequency of 0.5Hz, effectively filtering out high-frequency interference. The differential amplifier adopts a two-stage amplification structure, with the first-stage amplification factor set to 10x and the second-stage amplification factor adjustable from 10x to 100x, and a total differential gain A_d = 100 to 1000x, which can adapt to coupling signals of different strengths.

[0051] Furthermore, the steady-state discrimination module includes an ADC sampling unit, an IIR filtering unit, and a multi-dimensional criterion unit. The ADC sampling unit uses a 12-bit precision chip with a sampling rate of 200 SPS, balancing sampling accuracy and data processing efficiency. The IIR filtering unit is a second-order low-pass filter structure, further suppressing power frequency and high-frequency interference. The multi-dimensional criterion unit incorporates variance calculation, slope analysis, time window consistency determination, and power frequency identification algorithms. It sets a variance threshold σ² < 0.01 mV² (for extremely low-frequency signals with minimal fluctuations), a slope threshold |dV / dt| < 0.1 mV / s, and uses three time windows of 50 ms, 100 ms, and 200 ms for time window consistency determination, with a threshold ε = 5 mV. When |mean... 50 -mean 200 When | < ε, it is determined to be a steady-state signal, ensuring accurate identification of effective ultra-low frequency signals.

[0052] Furthermore, the main control module employs a low-power MCU, integrating data processing, logic control, and power management functions. The main control module has a built-in 3000mAh lithium battery power supply unit, supports 5V USB charging, has a standby time of ≥72 hours, and a continuous working time of ≥8 hours, meeting the needs of outdoor and long-term operation. The wireless communication module supports 2.4GHz / Sub-GHz dual-mode communication for remote data transmission and alarm signal push, with a communication distance of ≥500m in open environments. The audible and visual alarm module includes a red LED light and a buzzer. The LED light has an operating current of 20mA and a luminous intensity of ≥5000mcd, while the buzzer alarm volume is ≥85dB, ensuring a clear warning effect in noisy environments.

[0053] The device in this embodiment was specifically tested for ultra-low frequency detection scenarios, and the test results under different operating conditions are as follows:

[0054] 1. Ultra-low frequency core detection scenario: A 0.1Hz, 10kVAC ultra-low frequency voltage is applied to the conductor under test. The device is installed 30cm away from the conductor according to the specification. The dual differential electrodes output a stable 165μV differential signal, which is amplified 100 times and outputs a 16.5mV standard signal. The ADC sampling value variance is 0.004mV², the signal slope is 0.05mV / s, and the difference between the mean values ​​of the 50ms and 200ms windows is 1.2mV < ε. The system judges it as "energized". The red LED light stays on, the buzzer alarms intermittently once every 2 seconds, and the wireless communication module pushes the information "ultra-low frequency energized - voltage level estimated 10kV" to the background monitoring system with a response delay ≤100ms.

[0055] 2. Close-range ultra-low frequency scenario: The conductor under test is a 0.5Hz, 5kVAC cable. The device is installed 20cm away from the conductor. The electrode outputs a 98μV differential signal, which is amplified to 9.8mV. The signal stability is good, with no obvious drift. The system accurately determines that it is "energized". The alarm and communication functions are normal, verifying the reliability of close-range detection.

[0056] 3. Strong interference ultra-low frequency scenario: Under the power frequency interference environment of 50Hz and 10kV / m, when a voltage of 0.1Hz and 8kVAC is applied to the conductor under test, the device outputs a 132μV differential signal. After IIR filtering, the power frequency interference component is attenuated to below 0.05mV, and the signal-to-noise ratio is ≥30dB. The system accurately identifies the effective ultra-low frequency signal and determines it to be "charged", without any misjudgment or missed judgment.

[0057] 4. No power interference scenario: There is no voltage being measured, the environment has 50Hz power frequency and high frequency radio interference, the device output signal variance is 0.8mV², and the time window statistical analysis shows that there is no effective steady-state signal component in the 0.1Hz~1Hz frequency band. The system judges it as "no power". The sound and light alarm module does not activate and wirelessly pushes the status information "no power - environmental interference exists".

[0058] 5. Impedance Influence Verification Scenario: The equivalent input impedance of the pre-acquisition structure was adjusted to 10¹²Ω. Under the conditions of 0.1Hz and 10kVAC, the charge holding time constant τ < 5s, the coupled charge was rapidly discharged, and the output signal decayed to 12μV, which was lower than the noise floor (15μV), making it impossible to complete steady-state identification. When the impedance was restored to 10¹³Ω, the signal recovered to 162μV, and the system made normal judgment, verifying the core role of ultra-high impedance as an essential technical feature.

[0059] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A dynamic frequency-changing tracking live-line detection device, comprising a wireless communication module, an audible and visual alarm module, a mounting base, and a protective housing; characterized in that: It also includes a main control module, a dual differential electric field coupling module, an ultra-high impedance steady-state acquisition module, a differential amplification and signal conditioning module, and a steady-state discrimination module; The dual differential electric field coupling module is used to generate two or more sets of coupled potential signals with different spatial positions under the action of the spatial electrostatic field around the conductor being measured. The ultra-high impedance steady-state acquisition module is connected to the dual differential electric field coupling module, which is used to suppress the discharge of coupled charge and maintain the steady-state existence of the coupled potential signal under ultra-low frequency or quasi-static electric field conditions. The differential amplification and signal conditioning module is connected to the ultra-high impedance steady-state acquisition module and is used to perform differential enhancement and low-frequency processing on the steady-state coupled potential signal; The steady-state discrimination module is connected to the differential amplification and signal conditioning module and is used to output the charged state of the conductor under test based on the time stability characteristics of the steady-state coupled potential signal. The main control module is electrically connected to the differential amplification and signal conditioning module, the steady-state discrimination module, the wireless communication module, and the audible and visual alarm module, respectively, and is used for data processing, logic control, and command issuance. The dual differential electric field coupling module includes four or more electric field coupling electrodes, which form two sets of differential electrode pairs arranged opposite each other in space. Each differential electrode pair is used to sense the coupling potential formed by the spatial electrostatic field around the conductor under test at different positions. The unbalanced distribution characteristics of the spatial electrostatic field are characterized by the steady-state potential difference between each differential electrode pair.

2. The dynamic frequency-changing tracking charged detection device according to claim 1, characterized in that: The ultra-high impedance steady-state acquisition module includes an ultra-high impedance pre-hold structure, with an equivalent input impedance higher than 10 Ω. 13 Ω is set at the output end of the electric field coupling electrode, and works in conjunction with the dual differential electrode to ensure that the spatial unbalanced coupling potential is stably retained in the ultra-low frequency time scale.

3. The dynamic frequency-changing tracking charged detection device according to claim 1, characterized in that: The ultra-high impedance steady-state acquisition module also includes an input protection diode, which is a dual series diode with a withstand voltage of 85V, connected in parallel on both sides of the amplifier input terminal to protect against transient overvoltage.

4. The dynamic frequency-changing tracking charged detection device according to claim 1, characterized in that: The differential amplification and signal conditioning module is configured to operate in low-frequency or ultra-low-frequency mode, with a passband upper limit of less than 5Hz, in order to suppress interference signals in the power frequency and above frequency bands while maintaining steady-state coupling potential information.

5. The dynamic frequency-changing tracking charged detection device according to claim 1, characterized in that: The steady-state discrimination module makes a judgment based on the amplitude stability, change slope and statistical fluctuation characteristics of the steady-state coupled potential signal within a preset time window. When the steady-state coupled potential signal meets the stability criterion within the time window, it outputs the judgment result that the conductor under test is in a charged state.

6. The dynamic frequency-changing tracking charged detection device according to claim 1, characterized in that: The electric field coupling electrode is a nickel-plated copper sheet in the shape of a 150° arc, with dimensions of 50mm in height, 30mm in radius, and 1mm in thickness. The two sets of differential electrodes are symmetrically arranged on the mounting base with a spacing of 2mm between them. The electrode surfaces are passivated and the edges are designed with a radius of 2mm. The inner side of the electrodes is filled with epoxy resin LEDO 6060 insulating medium, and the relative positions of the four electrodes are fixed by an integrally molded epoxy resin insulating bracket.

7. The dynamic frequency-changing tracking charged detection device according to claim 2, characterized in that: The ultra-high impedance pre-holding structure includes a leakage current suppression resistor pre-circuit, wherein the leakage current suppression resistor circuit adopts a 10 14 An Ω ultra-high impedance chip forms the preamplifier non-inverting circuit, connected in series between the output terminals of each electrode and the input terminal of the differential amplifier, ensuring that the equivalent input impedance is not less than 10Ω. 13 Ω.

8. The dynamic frequency-changing tracking charged detection device according to claim 4, characterized in that: The differential amplifier in the differential amplification and signal conditioning module adopts a two-stage amplification structure, with the first-stage amplification factor set to 10 times and the second-stage amplification factor set to 10 to 100 times, and the total differential gain A_d = 100 to 1000 times; the filter circuit adopts a second-order RC low-pass filter structure with a cutoff frequency of 0.5Hz; the differential amplifier is configured with an input impedance ≥10GΩ, an input bias current ≤3pA, and an equivalent noise voltage ≤10nV / Hz.

9. A non-contact voltage detection method for ultra-low frequency voltages based on dual differential coupling, characterized in that: The application of the dynamic frequency-changing tracking charged detection device according to any one of claims 1-8 includes the following steps: Step 1: Device installation: Fix the device 20-30cm away from the conductor to be tested using the mounting base, adjust the device so that the dual differential electrodes face the conductor to be tested, and complete the self-test after turning on the power. Step 2: Signal Coupling: The electrostatic field generated by the conductor under test acts on the dual differential electrodes. The upper outer electrode and the upper inner electrode generate the first differential signal Vd1=(k1-k2) Vm, and the lower outer electrode and the lower inner electrode generate the second differential signal Vd2=(k3-k4) Vm. In the formula, k1, k2, k3, and k4 are the coupling coefficients of the four electrodes, and Vm is the potential of the conductor under test in the charged state. The two sets of signals are synchronously input into the ultra-high impedance steady-state acquisition module. Step 3: Steady-state holding and signal conditioning: The ultra-high impedance pre-hold structure suppresses coupled charge discharge and maintains signal steady state; the input protection diode prevents transient impact; the differential amplifier amplifies the μV-level differential signal to the mV level, and after being filtered by a second-order RC low-pass filter to remove interference in the power frequency and above frequency bands, it is output to the main control module. Step 4: Steady-state identification: The ADC unit of the main control module acquires the amplified signal at a rate of 200 SPS, suppresses power frequency interference through the IIR filter unit, and the multi-dimensional criterion unit outputs three states: charged, uncharged, and abnormal interference through variance calculation, slope analysis, time window consistency determination and interference identification. Step 5: Warning and Communication: If the circuit is determined to be live, the audible and visual alarm module will be activated, and the wireless communication module will push the live information to the background system; if the circuit is determined to be abnormal, the LED light will flash and the buzzer will sound continuously, prompting you to check the source of interference.

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