Impedance analysis-based wire crimping quality evaluation method for electric energy metering box

Abstract

The present application relates to the technical field of wire quality detection, and particularly relates to a method for evaluating wire crimping quality of an electric energy metering box based on impedance analysis. The method comprises the following steps: at a wire crimping detection station, a mechanical micro-vibration is applied to a terminal of a wire to be detected by using a vibration excitation element inside a clamp; high-frequency alternating excitation current is injected into both ends of the terminal of the wire to be detected, and the excitation voltage amplitude is limited within a safety threshold of dry circuit test of electric contact; an impedance response voltage signal affected by the mechanical micro-vibration is collected in real time, a driving signal of the mechanical micro-vibration is used as a homologous reference, orthogonal coherent demodulation and low-pass filtering are performed on the impedance response voltage signal, a dynamic impedance change rate is extracted, and early crimping quality defects of the terminal of the wire are evaluated according to the dynamic impedance change rate. The present application effectively solves the problem of missed detection caused by breakdown of an oxide layer on a production line.

Description

Technical Field

[0001] This invention relates to the field of conductor quality testing technology, and specifically to a method for evaluating the crimping quality of conductors in power metering boxes based on impedance analysis. Background Technology

[0002] As the core hub for electricity metering at the end of the power system, the quality of crimping of the high-current circuit conductors inside the electricity metering box is a key factor determining the safety of power grid operation. On automated production and assembly lines, due to factors such as uneven material hardness, wear of crimping molds, and oxidation of copper wire surfaces, early hidden defects such as loose connections, broken strands, or incomplete removal of oxide layers are prone to occur between the conductors and terminals. These defects are difficult to detect when the equipment is cold-state and shipped from the factory, but after the equipment is put into operation and a large current is applied, it will cause local heating of the contact surface and accelerate deterioration, eventually leading to meter burnout or even fire accidents.

[0003] Currently, the industry mainly relies on the following two technical approaches to inspect the quality of wire crimping: The first approach is based on physical flaw detection or machine vision for macroscopic deformation detection. For example, the Chinese patent application document CN114396842B, which describes a method for inspecting the crimping of tension clamps, uses X-ray penetration technology to screen for internal defects in the crimped area. However, such inspection methods based on X-rays, ultrasound, or industrial vision are expensive and have a slow inspection cycle. They can only observe the volume compression or macroscopic fracture on the outside of the terminal, and cannot see through and accurately assess the electrical connection contact quality at the internal metal lattice level. They are not suitable for large-scale real-time screening on production lines.

[0004] Another technical approach is contact resistance testing based on the constant current voltage reduction method. For example, Chinese patent application CN108982968A describes an online contact resistance measurement system and method, which uses conventional test excitation combined with Fourier algorithm to extract minute impedances for measurement. However, this method has an easily overlooked underlying physical paradox when used for production line evaluation: the open-circuit test terminal voltage of traditional low-resistance meters or testing instruments is usually as high as several volts. When the probe is applied to a defective product with a micron-sized oxide film or microscopic looseness, the excessively high voltage barrier will instantly trigger an electric arc, breaking down the microscopic insulating oxide layer, i.e., the Friding effect. This irreversible breakdown will conduct the originally poorly contacted microscopic cross-section at the moment of probe testing. Ultimately, the resistance value collected by the measurement and control equipment will show a low false health state, causing defective products to be missed and flow into the power grid. Summary of the Invention

[0005] To address the problem that existing technologies cannot detect deep crimping defects in the complex noise environment of a production line without inducing the Friding breakdown effect to preserve the original defect appearance, while maintaining a non-destructive and high signal-to-noise ratio, this invention proposes a method for evaluating the crimping quality of power metering box conductors based on impedance analysis. This method includes:

[0006] S1. Apply mechanical micro-excitation to the terminal of the conductor under test, inject a high-frequency AC excitation current into both ends of the terminal, and collect the impedance response voltage signal at both ends of the terminal affected by the mechanical micro-excitation in real time; S2. Using the transmitter clock of the high-frequency AC excitation current as the first reference carrier, perform digital down-conversion and primary low-pass filtering on the impedance response voltage signal to obtain a dynamic impedance voltage envelope signal; extract the driving signal of the mechanical micro-excitation as the second reference carrier, perform orthogonal multiplication and secondary low-pass filtering on the dynamic impedance voltage envelope signal to obtain the dynamic impedance change amplitude with the same frequency as the mechanical micro-excitation; S3. Obtain the static reference impedance of the terminal of the conductor under test, and calculate the dynamic impedance change rate by combining it with the dynamic impedance change amplitude; S4. Obtain the dynamic modulation depth threshold, compare the dynamic impedance change rate with the dynamic modulation depth threshold, and evaluate the quality of the terminal of the conductor under test based on the comparison result.

[0007] This invention introduces mechanical micro-excitation to transform microscopic crimping defects into dynamic modulation characteristics of high-frequency electrical signals. It also employs a two-stage coherent demodulation architecture. After filtering out the high-frequency carrier, the driving signal of the mechanical micro-excitation is extracted and used as a second demodulation reference for orthogonal multiplication. This cross-mode signal extraction method can accurately separate weak dynamic impedance change characteristics in the complex background noise of the production line, achieving non-destructive and highly interference-resistant identification of hidden crimping defects.

[0008] Furthermore, injecting high-frequency AC excitation current into both ends of the test wire terminal includes: setting a preset dry circuit test safety threshold, limiting the open circuit test voltage amplitude corresponding to the high-frequency AC excitation current to be less than the dry circuit test safety threshold, so as to prevent arc breakdown of the oxide layer inside the test wire terminal and maintain the original state of the crimped contact surface.

[0009] This invention effectively avoids the high-voltage test signal from triggering an arc and breaking down the micron-level oxide film, i.e., the Friding effect, by limiting the open-circuit test voltage to within the safe threshold of dry circuit testing. This ensures that the original failure site of the crimped contact surface is not destroyed during the testing process, and reduces the risk of defective products being missed due to current micro-melting welding.

[0010] Furthermore, applying mechanical micro-excitation to the test wire terminal includes: using a vibrator integrated into the testing station fixture to output a mechanical stress wave of a fixed frequency to the test wire terminal.

[0011] Furthermore, the method for evaluating the wire crimping quality of the power metering box based on impedance analysis also includes: differentially amplifying the impedance response voltage signal using a differential amplifier circuit to suppress electromagnetic common-mode interference; and band-limiting the amplified impedance response voltage signal using a band-pass filter network, wherein the center frequency of the band-pass filter network is the frequency of the high-frequency AC excitation current.

[0012] This invention utilizes a differential amplifier circuit and a bandpass filter network for pre-processing hardware. The differential structure can suppress common-mode interference from high-power motors in the production line environment, while the bandpass filter filters out out-of-band noise in advance, effectively improving the signal-to-noise ratio of the original impedance response signal and reducing the computational burden of back-end demodulation.

[0013] Further, the impedance response voltage signal is digitally down-converted and subjected to primary low-pass filtering to obtain a dynamic impedance voltage envelope signal. Specifically, this includes multiplying the impedance response voltage signal with an orthogonal sequence of the first reference carrier, inputting the calculation result into a primary low-pass filter network to filter out high-frequency carrier components, and extracting the dynamic impedance voltage envelope signal.

[0014] Further, obtaining the dynamic impedance change amplitude at the same frequency as the mechanical micro-excitation specifically includes: orthogonally multiplying the dynamic impedance voltage envelope signal with the second reference carrier to generate an in-phase branch signal and a quadrature branch signal; inputting the in-phase branch signal and the quadrature branch signal into a secondary low-pass filter array for integration and smoothing to obtain quadrature DC components; and extracting the dynamic impedance change amplitude at the same frequency as the mechanical micro-excitation based on the quadrature DC components.

[0015] Furthermore, the secondary low-pass filter array employs a cascaded integrator comb filter, the cutoff frequency of which is half the mechanical micro-excitation frequency.

[0016] The secondary low-pass filter array of this invention uses a cascaded integrator comb filter, and sets its cutoff frequency to half of the mechanical micro-excitation frequency. This not only reduces the occupancy of hardware resources, but also effectively removes broadband Gaussian white noise from the production line and random vibration noise from pneumatic equipment, ensuring the purity of the final extracted impedance change amplitude.

[0017] Furthermore, the calculation of the dynamic impedance change rate includes: extracting the DC component of the dynamic impedance voltage envelope signal under static clamping conditions as the static reference impedance of the terminal of the conductor under test; and obtaining the dynamic impedance change rate based on the dynamic impedance change amplitude and the static reference impedance.

[0018] Furthermore, the evaluation of the quality of the test conductor terminal based on the comparison results includes: when the dynamic impedance change rate is greater than the dynamic modulation depth threshold, determining that there is an internal defect in the test conductor terminal and generating a poor contact alarm flag.

[0019] Furthermore, the method for evaluating the wire crimping quality of the power metering box based on impedance analysis also includes: converting the poor contact alarm sign into a control command, sending the control command to the production line programmable logic controller, and triggering the defective product rejection station to perform automated sorting and interception actions.

[0020] This invention solves the problem of delay in alarm waiting time in conventional host computer software by directly converting alarm indicators of poor contact into control commands and sending them to the production line programmable logic controller. It forms an automated operation from defect identification to physical removal, effectively avoiding missed detections in manual processing and effectively improving the cycle time and efficiency of batch inspection on the production line.

[0021] The present invention has the following technical effects: This invention overcomes the technical limitations of traditional wire crimping quality inspection, such as the inability of visual inspection to see the internal structure and the susceptibility of conventional electrical testing to damage the site. By employing a combined excitation of active mechanical micro-vibration and high-frequency impedance detection in a dry circuit, the dynamic impedance characteristics of the defective area are extracted without damaging the microstructure of the crimp. Utilizing hardware-level dual-stage orthogonal coherent demodulation technology, the mechanical micro-vibration frequency is used as the extraction reference for the electrical signal, effectively filtering out stray noise from the production line environment. This not only achieves high-precision, non-destructive interception of hidden defects such as loose wires and residual oxide layers, avoiding the risk of meter burnout caused by defective products entering the power grid, but also enables automatic sorting through underlying communication linkage, effectively improving the quality control level of automated production lines. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for evaluating the wire crimping quality of an energy metering box based on impedance analysis, provided in an embodiment of the present invention. Figure 2 This is a comparison diagram of the effects of the prior art provided in the embodiments of the present invention and the present invention. Detailed Implementation

[0023] This invention provides a method for evaluating the crimping quality of power metering box wires based on impedance analysis, referring to... Figure 1 This includes steps S1-S4: S1: Data Acquisition and Preprocessing.

[0024] Specifically, mechanical micro-excitation is applied to the terminals of the conductor under test, high-frequency AC excitation current is injected into both ends of the terminals of the conductor under test, and the impedance response voltage signal at both ends of the terminals of the conductor under test affected by the mechanical micro-excitation is collected in real time.

[0025] First, in the offline wire crimping inspection station, the pneumatic clamp is closed to fix the terminal of the wire to be tested. In this embodiment, a piezoelectric ceramic vibrator is preferably embedded inside the jaws of the pneumatic clamp. After the terminal of the wire to be tested is completely clamped and fixed, the drive circuit sends a fixed frequency drive signal to the piezoelectric ceramic vibrator to control it to continuously output a constant frequency mechanical stress wave to the terminal of the wire to be tested. In this embodiment, the frequency of the mechanical micro-excitation is preferably set to 500Hz. This frequency setting has been verified by frequency sweep in the early stage and can effectively avoid the 50Hz motor fundamental frequency noise commonly found in the production line environment. At the same time, it is far away from the mechanical resonance frequency of the pneumatic clamp itself, thereby ensuring that the applied mechanical stress wave is pure and stable. This pure mechanical stress wave can cause the possible loose tight parts inside the crimping surface to undergo micro-deformation with the same frequency period.

[0026] While applying mechanical micro-excitation, a high-frequency AC excitation current is simultaneously injected into both ends of the test conductor terminal. In this embodiment, a 10000Hz high-frequency sine wave test signal is preferably generated using a direct digital frequency synthesis chip. This signal is converted into a stable high-frequency AC excitation current via a digital-to-analog converter circuit and a voltage-controlled constant current source circuit. To prevent high voltage from breaking down any residual insulating oxide layer inside the test conductor terminal, a precision passive resistor attenuation network is connected in series at the signal output end. Preferably, the open-circuit test voltage amplitude corresponding to the high-frequency AC excitation current is limited to 20mV. This extremely low voltage amplitude is within the safety threshold range of classic dry circuit testing, which can physically block the conditions for the Friding effect to occur, ensuring that the test process will not trigger micro-arc breakdown, thereby preserving the original failure state of the crimped contact surface without damage.

[0027] Since the test excitation voltage has been compressed, the impedance response voltage signal generated at both ends of the terminal is relatively weak and is superimposed with a large amount of electromagnetic interference in the production line space. Therefore, in this embodiment, the impedance response voltage signal is extracted in real time by a pure copper voltage probe independent of the current injection circuit and sent to the hardware preprocessing link. In this embodiment, a differential instrumentation amplifier circuit with a high common-mode rejection ratio is preferably used to perform primary differential amplification on the extracted weak signal. This differential topology can effectively cancel electromagnetic common-mode interference in the production line space by utilizing positive and negative symmetrical input terminals. Subsequently, the differentially amplified analog signal is input to an active bandpass filter network for bandwidth limitation. In this embodiment, the center frequency of the bandpass filter network is preferably aligned with 10000Hz, which is consistent with the transmission frequency of the high-frequency AC excitation current, thereby filtering out broadband spurious noise outside the 10000Hz effective frequency band. The analog signal after bandpass filtering is finally sampled in real time by a high-speed analog-to-digital converter and converted into a discrete digital data stream, which serves as the underlying data source for subsequent feature extraction.

[0028] S2: Two-stage orthogonal coherent demodulation and dynamic impedance extraction.

[0029] Specifically, using the transmitter clock of the high-frequency AC excitation current as the first reference carrier, the impedance response voltage signal is digitally down-converted and primary low-pass filtered to obtain the dynamic impedance voltage envelope signal; the driving signal of the mechanical micro-excitation is extracted as the second reference carrier, and the dynamic impedance voltage envelope signal is orthogonally multiplied and secondary low-pass filtered to obtain the dynamic impedance change amplitude with the same frequency as the mechanical micro-excitation.

[0030] The discrete digital data stream output from S1 is input into a field-programmable gate array (FPGA) chip for the first stage of digital down-conversion processing. The transmitter clock that generates the high-frequency AC excitation current is obtained as the first reference carrier. Inside the FPGA, a hardware multiplier is used to multiply the acquired impedance response voltage signal point by point with the sine and cosine sequences of the first reference carrier. The multiplied signal is then input into a primary low-pass filter network. In this embodiment, the cutoff frequency of the primary low-pass filter network is preferably set to 1000Hz to ensure that the high-frequency carrier component corresponding to the high-frequency AC excitation current and its high-order harmonic interference are filtered out, thereby separating the dynamic impedance voltage envelope signal in the baseband. At this time, the envelope signal is still mixed with broadband noise from the production line environment and characteristic modulation signals caused by mechanical micro-excitation.

[0031] To accurately extract features related to crimping quality in complex environmental noise, this embodiment performs a second-stage orthogonal coherent demodulation on the dynamic impedance voltage envelope signal, extracts the driving signal used to drive the piezoelectric ceramic exciter as the second reference carrier, and performs quadrature multiplication of the dynamic impedance voltage envelope signal with the sine and cosine sequences of the second reference carrier, respectively, to generate mutually orthogonal in-phase and quadrature branch signals. This synchronization mechanism, which directly uses the mechanical drive source as the electrical demodulation reference, can shift the weak impedance changes that are in sync with the mechanical micro-excitation to near the DC zero frequency, while pushing other unrelated random vibration noise in the production line to the high-frequency band.

[0032] Finally, the generated in-phase and quadrature branch signals are respectively sent to the secondary low-pass filter array for deep integral smoothing. In this embodiment, a cascaded integrator comb filter is preferably used as the hardware architecture of the filter array. In order to achieve the ultimate cutting of Gaussian white noise on the production line, the cutoff frequency of the cascaded integrator comb filter is preferably set to 250Hz. This parameter is set to half of the 500Hz frequency of the mechanical micro-excitation to prevent spectral aliasing. After the in-phase and quadrature branch signals pass through the filter, the high-frequency AC noise components are completely filtered out, and finally pure quadrature DC components are output. Then, the hardware calculation module is controlled to sum the squares of the two quadrature DC components and then take the square root to extract the dynamic impedance change amplitude with the same frequency as the mechanical micro-excitation.

[0033] S3: Static reference impedance extraction and dynamic impedance change rate calculation.

[0034] Specifically, the static reference impedance of the terminal of the conductor under test is obtained, and the dynamic impedance change rate is calculated by combining the dynamic impedance change amplitude.

[0035] First, the static reference impedance of the terminal under test is obtained. In this embodiment, the initial static holding phase is defined as the first 500ms after the pneumatic clamp closes and fully clamps the terminal under test, before the drive signal is sent to the piezoelectric ceramic vibrator. During this static phase, the DC component of the dynamic impedance voltage envelope signal output by the primary low-pass filter network in S2 is continuously acquired and extracted. At this time, due to the lack of physical modulation effect of external mechanical micro-excitation, the envelope signal presents a stable DC level. The average value of this DC level is extracted and directly latched into the static reference register inside the field programmable gate array as the static reference impedance of the terminal under test in the current clamping state.

[0036] After obtaining the static reference impedance, the dynamic impedance change rate is calculated by combining the dynamic impedance change amplitude extracted in S2. Due to the slight differences in wire diameter production tolerances and terminal materials between different batches of conductors, the initial absolute impedance values ​​of the contact surfaces of different qualified products will also have natural fluctuations. If the absolute value of the change amplitude is used directly for evaluation, it is easy to make misjudgments. Therefore, in this embodiment, it is preferable to call the hardware divider logic unit configured inside the field programmable gate array to perform normalization calculation. The dynamic impedance change amplitude obtained in S2, which is in sync with the mechanical micro-excitation, is used as the numerator, and the static reference impedance latched in the static reference register is used as the denominator. The underlying hardware division operation is performed, and the direct output of this division operation is the normalized dynamic impedance change rate. Through the above calculation, the absolute impedance value, which is easily affected by natural deviations, can be transformed into a relative proportional characteristic that only reflects the mechanical stability of the internal micro-contact surface.

[0037] S4: Defect identification and automated production line sorting and interception.

[0038] Specifically, the dynamic modulation depth threshold is obtained, the dynamic impedance change rate is compared with the dynamic modulation depth threshold, and the quality of the conductor terminal under test is evaluated based on the comparison results.

[0039] First, the dynamic modulation depth threshold is obtained. In this embodiment, the dynamic modulation depth threshold is set to 0.005. This value is calibrated in advance in the production line environment through a sample optimization experiment. The specific steps are as follows: extract defective samples that are known to be in a loose state and standard good samples that are completely qualified. Under the same mechanical micro-excitation and high-frequency AC excitation conditions, continuously collect and calculate the impedance data of these two types of samples, and then draw the statistical distribution curve of the dynamic impedance change rate of the two types of samples. Extract the intersection critical point of the two sets of data distribution curves as the final dynamic modulation depth threshold.

[0040] After obtaining the threshold, the dynamic impedance change rate calculated in S3 is read in real time using the hardware comparison module and compared with the dynamic modulation depth threshold. The crimping quality of the wire terminal under test is evaluated based on the comparison result: if the comparison result shows that the current dynamic impedance change rate is greater than the set dynamic modulation depth threshold, it indicates that the wire terminal under test exhibits an abnormally sensitive response to external vibration. At this time, it is determined that there are hidden defects such as the insulation oxide layer not being removed or the metal wire harness being loose inside the wire terminal under test, and the state machine is immediately triggered to flip, generating a high-level contact failure alarm mark.

[0041] After generating a poor contact alarm flag, the production line-level control operation is immediately executed: the poor contact alarm flag is packaged into a control command under the standard industrial control protocol, and the control command is sent to the programmable logic controller (PLC) of the production line master through the industrial field communication bus. Upon receiving the command, the PLC immediately triggers the end effector located at the defective product rejection station. The PLC directly drives the pneumatic push rod device to perform an automated sorting and interception action, quickly pushing the test wire terminal with contact defects into the defective product recycling tank, realizing automated online interception without manual intervention.

[0042] Figure 2 This is a comparison chart of the effects of the prior art and the present invention provided in the embodiments of the present invention. It can be seen that the prior art curve has a high impedance at the beginning, but the voltage is too high in the early stage of the test, which causes the oxide layer to be broken down instantly, and the impedance drops, which is disguised as a healthy low impedance straight line. In contrast, the present invention curve does not break down the oxide layer under the limit, and the overall impedance remains at a high level. At the same time, under the action of mechanical micro-excitation, the impedance exhibits obvious periodic dynamic modulation fluctuations.

Claims

1. A method for evaluating the crimping quality of power metering box conductors based on impedance analysis, characterized in that, include: S1, apply mechanical micro-excitation to the terminal of the conductor under test, inject high-frequency AC excitation current into both ends of the terminal of the conductor under test, and collect the impedance response voltage signal of both ends of the terminal of the conductor under test affected by the mechanical micro-excitation in real time; S2, using the transmitter clock of the high-frequency AC excitation current as the first reference carrier, the impedance response voltage signal is digitally down-converted and primary low-pass filtered to obtain the dynamic impedance voltage envelope signal; the driving signal of the mechanical micro-excitation is extracted as the second reference carrier, and the dynamic impedance voltage envelope signal is orthogonally multiplied and secondary low-pass filtered to obtain the dynamic impedance change amplitude with the same frequency as the mechanical micro-excitation. S3, obtain the static reference impedance of the terminal of the conductor to be tested, and calculate the dynamic impedance change rate by combining the dynamic impedance change amplitude; S4, obtain the dynamic modulation depth threshold, compare the dynamic impedance change rate with the dynamic modulation depth threshold, and evaluate the quality of the test conductor terminal based on the comparison result.

2. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, Injecting a high-frequency AC excitation current into both ends of the test conductor terminal includes: setting a preset dry circuit test safety threshold, limiting the open circuit test voltage amplitude corresponding to the high-frequency AC excitation current to be less than the dry circuit test safety threshold, so as to prevent the oxide layer inside the test conductor terminal from arcing and breaking down, and maintaining the original state of the crimped contact surface.

3. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, The mechanical micro-excitation applied to the test wire terminal includes: using a vibrator integrated into the testing station fixture to output a mechanical stress wave of a fixed frequency to the test wire terminal.

4. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, The method further includes: differentially amplifying the impedance response voltage signal using a differential amplifier circuit to suppress electromagnetic common-mode interference; and band-limiting the amplified impedance response voltage signal using a band-pass filter network, wherein the center frequency of the band-pass filter network is the frequency of the high-frequency AC excitation current.

5. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, The impedance response voltage signal is digitally down-converted and subjected to primary low-pass filtering to obtain a dynamic impedance voltage envelope signal. Specifically, this includes multiplying the impedance response voltage signal with an orthogonal sequence of the first reference carrier, inputting the calculation result into a primary low-pass filter network to filter out high-frequency carrier components, and extracting the dynamic impedance voltage envelope signal.

6. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, Obtaining the dynamic impedance change amplitude at the same frequency as the mechanical micro-excitation specifically includes: orthogonally multiplying the dynamic impedance voltage envelope signal with the second reference carrier to generate an in-phase branch signal and a quadrature branch signal; inputting the in-phase branch signal and the quadrature branch signal into a secondary low-pass filter array for integration and smoothing to obtain a quadrature DC component; and extracting the dynamic impedance change amplitude at the same frequency as the mechanical micro-excitation based on the quadrature DC component.

7. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 6, characterized in that, The secondary low-pass filter array employs a cascaded integrator-comb filter, and the cutoff frequency of the cascaded integrator-comb filter is half of the mechanical micro-excitation frequency.

8. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, The calculation of the dynamic impedance change rate includes: extracting the DC component of the dynamic impedance voltage envelope signal under static clamping condition, as the static reference impedance of the terminal of the conductor under test; and obtaining the dynamic impedance change rate based on the dynamic impedance change amplitude and the static reference impedance.

9. The method for evaluating the wire crimping quality of an energy metering box based on impedance analysis according to claim 1, characterized in that, The evaluation of the quality of the test conductor terminal based on the comparison results includes: when the dynamic impedance change rate is greater than the dynamic modulation depth threshold, it is determined that there is a defect inside the test conductor terminal, and a poor contact alarm is generated.

10. The method for evaluating the crimping quality of power metering box wires based on impedance analysis according to claim 9, characterized in that, The method further includes: converting the poor contact alarm sign into a control command, sending the control command to the production line programmable logic controller, and triggering the defective product rejection station to perform automated sorting and interception actions.

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