29 results about "Transfer impedance" patented technology

The invention discloses a battery internal defect detection method, system, medium and equipment, and the method comprises the steps: preparing battery samples with different defects; performing an electrochemical impedance spectroscopy test on the battery sample under the same temperature environment, and establishing an impedance spectroscopy database of the battery in a normal state and a defect full charge state under a normal temperature working condition; calculating charge transfer impedance, solid electrolyte interfacial film impedance and relaxation time of a corresponding characteristic peak in the impedance spectrum data through the relaxation time distribution curve area, and analyzing the charge transfer impedance, the solid electrolyte interfacial film impedance and the relaxation time of the corresponding characteristic peak; constructing a battery internal defect identification model to accurately identify whether the battery has internal defects or not; performing relaxation time distribution quantification at a constant temperature to obtain charge transfer impedance, solid electrolyte interfacial film impedance and relaxation time of a corresponding characteristic peak; and importing the charge transfer impedance, the solid electrolyte interfacial film impedance and the relaxation time of the corresponding characteristic peak into the battery internal defect identification model to obtain a diagnosis result of whether the defect exists in the single battery or not.

The invention discloses an AI-enabled real-time electrochemical detection system, which is composed of a real-time electrochemical detection module and an embedded AI data processing and analysis module, the real-time electrochemical detection module comprises an electrochemical electrode system, a sample pool and an electrochemical workstation, the surface of a working electrode is modified with a probe of a specific recognition target, and when the probe is combined with the target, the probe of the specific recognition target can be detected by the embedded AI data processing and analysis module. The working electrode interface charge transfer impedance changes in real time to generate a dynamic electric signal, and the electrochemical workstation provides electric input and collects the signal; the embedded AI data processing and analysis module is used for denoising the dynamic electric signals through an adaptive filtering algorithm based on wavelet transform, extracting time-frequency domain joint features through a 1D-CNN and LSTM mixed deep learning model, and establishing a nonlinear mapping relation between the signals and target concentration. Through AI enabling electrochemical detection, the defects of low time efficiency, large error and low information utilization rate of the traditional technology are comprehensively overcome, and an innovative solution is provided for high-precision, rapid and anti-interference target substance detection.

The application provides a transient ground potential rise induced coupling determination method through cable shielding layer, and belongs to the technical field of cable shielding layer.The application establishes a distributed parameter partial element equivalent circuit model of a grounding network, solves transient ground potential distribution by using a finite difference time domain method, obtains equivalent transfer impedance frequency characteristics of a braided shielding layer by using a four-port S parameter vector network analysis method and a variational asymptotic homogenization multi-scale algorithm, solves core line common mode voltage and differential mode voltage by establishing a multi-conductor transmission line equation group, constructs an artificial intelligence prediction model based on a topology perception graph neural network, solves a large-scale sparse admittance matrix by using a multilevel fast multipole method to obtain full network induced voltage distribution, and establishes a quantitative relationship model between ground potential rise and core line induced voltage, so that the technical problems that cable core line induced voltage caused by transient ground potential rise is difficult to accurately predict and effectively suppress are solved.

This invention discloses a multi-harmonic source responsibility quantification method based on asynchronous measurement, relating to the field of power quality harmonic technology. The method includes measuring the harmonic voltage of the bus of interest and the harmonic current at the connection point between each harmonic source and the bus of interest to construct the observed signal. After centering and whitening, a covariance matrix is ​​constructed. For the covariance matrix, the optimal common orthogonal matrix is ​​determined, and the source signal matrix is ​​reconstructed. The harmonic transfer impedance corresponding to each harmonic source signal is calculated based on a fast-changing component model. Each harmonic source signal is multiplied by its corresponding harmonic transfer impedance to obtain the harmonic voltage of the corresponding harmonic source. The harmonic voltage is projected onto the harmonic voltage of the bus of interest to achieve multi-harmonic source responsibility quantification. This method does not rely on GPS, simplifying the operation steps of multi-harmonic source responsibility quantification and helping to improve quantization efficiency. Simultaneously, the sparsity of the hybrid matrix reduces the computational dimensionality, alleviating the computational burden and improving quantization accuracy.

The application discloses a kind of lithium battery charge-discharge intelligent early warning method and system, belong to computer technology field.The method includes: when battery charges and discharges, actively injects multiple-frequency ac disturbance signal;Response signal is collected and is parsed to obtain dynamic electrochemical impedance spectroscopy containing charge transfer impedance and low-frequency phase angle;Based on the preset multidimensional health impedance mapping table, the reference impedance and reference phase angle corresponding to the current temperature and state of charge are inquired;Impedance relative deviation and phase angle offset are calculated;At least based on the deviation and offset, the internal micro-short circuit of battery is identified and early warning operation is executed;Through multidimensional mapping table and dynamic threshold mechanism, effectively eliminate working condition and aging interference, with high sensitivity and low false alarm rate;And supplemented by hierarchical early warning, standing verification and multi-cell collaborative calibration, the safety and usability of battery system are significantly improved.

This invention discloses a simulation-based method and system for handling electromagnetic interference in motor controllers, belonging to the field of electromagnetic compatibility testing and simulation technology. By constructing a test environment structural model including a test bench, artificial power network, shielded cables, current probes, the motor controller body, and the motor load using an electromagnetic simulation platform, electromagnetic field simulation calculations are performed to extract structural parasitic parameters and convert them into an equivalent circuit model. The equivalent circuit model is integrated into the main circuit simulation model to form a field-circuit coupled simulation model, and preliminary conducted emission simulation results are obtained. A current probe model is established, and the transfer impedance calibration factor is calculated. The preliminary simulation results are coupled and calibrated to obtain high-precision conducted emission simulation results. Based on the calibrated simulation results, the suppression effects of different interference suppression schemes are configured and evaluated, and the optimal suppression scheme is selected. The proposed scheme significantly improves the simulation accuracy of the conducted emission current method.

The application discloses a battery lithium precipitation detection method and device. When an electrochemical impedance test is performed on a battery, a corresponding first test result can be obtained. According to the first test result, corresponding first positive electrode charge transfer impedance and first negative electrode charge transfer impedance can be determined. Then, at least according to the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance, whether the battery has lithium precipitation can be determined. In this way, when detecting whether the battery has lithium precipitation, the battery does not need to be disassembled, and the detection can be realized, so that nondestructive testing is realized.

The invention discloses an in-situ lithium precipitation detection method based on a sweep frequency impedance test, and the method comprises the steps: carrying out the sweep frequency impedance test through superposing sine AC signals in a specific frequency range and amplitude in a conventional constant current charging process of a lithium ion battery, and achieving the synchronization of the charging process and the impedance test; and judging whether the lithium precipitation behavior of the battery occurs or not by analyzing the change trend of the constant phase element CPE corresponding to the charge transfer impedance. The method provided by the invention has the characteristics of high sensitivity and quick response, can detect the internal state of the battery in real time without damage, and provides online safety early warning for the battery. The composite material is widely applicable to various positive and negative electrode materials and lithium ion batteries under different working conditions, is helpful for improving the safety and stability of the batteries, and particularly has remarkable application potential in high-power charging and extreme environments.

The invention discloses a flow battery state-of-charge estimation method based on an electrochemical impedance spectrum, and belongs to the technical field of flow batteries. According to the method, a flow battery mechanism model and an electrochemical impedance spectrum model considering an electrochemical reaction process are established, electrochemical impedance spectrums under different SOCs are measured, and the models are utilized to carry out fitting analysis on impedance spectrum data; impedance characteristic parameters such as ohmic impedance, charge transfer impedance, diffusion resistance, diffusion time constant, constant phase angle element constant and diffusion coefficient are extracted; by calculating the Pearson's correlation coefficient between the SOC and each impedance characteristic parameter, the characteristic parameter with strong correlation with the SOC is screened out, and the mapping relation between the SOC and the impedance characteristic parameter is established, so that the accurate estimation of the SOC of the flow battery is realized. According to the method, the physical model of the electrochemical process in the battery is combined, the method has the advantages of high physical significance, high real-time performance, wide applicability and the like, the SOC estimation precision and reliability are improved, and the method is suitable for flow battery systems under different working conditions.

The invention relates to harmonic current emission level estimation, in particular to a distributed multi-source harmonic current emission level estimation method under an under-quantitative measurement condition, which comprises the following steps of: synchronously acquiring a concerned frequency harmonic voltage phasor of a concerned bus and a concerned frequency harmonic current phasor of a concerned harmonic source incoming line provided with a monitoring device in a concerned time period; the collected harmonic phasor time sequence data are preprocessed; converting the preprocessed harmonic phasor time sequence data from a time domain form into a frequency domain form; calculating harmonic transfer impedance between the concerned bus and the concerned harmonic source; estimating a harmonic emission current of the harmonic source of interest; according to the technical scheme provided by the invention, the defect that the emission level of the distributed multi-source harmonic current is difficult to accurately estimate under the conditions that the harmonic sources are distributed at multiple points and the number of monitoring devices is insufficient in the prior art can be effectively overcome.

The utility model discloses an inner loop matching clamp suitable for a cable transfer impedance test of a three-coaxial method, and belongs to the field of electromagnetic compatibility test. The device is characterized by comprising a main body (6), a through inner cavity is formed in the main body (6), the inner cavity comprises a clamping cavity (8), a clamping block mechanism (3) is arranged in the clamping cavity (8) in a tightly attached mode, a cable (1) to be tested is located in the clamping block mechanism (3), a shielding layer (103) of the cable (1) to be tested is attached to the inner wall of the clamping block mechanism (3), and a resistor containing cavity (9) communicated with the clamping cavity (8) is further formed in the main body (6). And a matched resistor (4) is placed in the resistor accommodating cavity (9) and is connected with an inner core (102) of the to-be-tested cable (1). According to the inner loop matching clamp suitable for the cable transfer impedance test of the three-coaxial method, an inner loop in the test of the three-coaxial method is formed, the coaxiality of a cable to be tested and a shielding layer is met, and the arrangement of a matching resistor is facilitated.

The invention relates to the technical field of durability testing, in particular to a high-voltage component transfer impedance testing device and method cooperating with comprehensive environment durability. The device comprises an environment testing system which comprises a built-in environment bin and a salt mist device and is used for testing temperature, humidity, altitude and salt mist working conditions of a high-pressure part sample; the salt mist device is arranged at the top of the built-in environment bin; the soaking test system comprises a first mounting clamp, a sample lifting platform and a soaking pool; the vibration test system comprises a second mounting clamp and a vibration table, the transfer impedance test system comprises an outer pipe, an outer sheath and a network analyzer, the outer sheath is arranged in the outer pipe and is mounted in an axial symmetry manner, and the network analyzer is connected with the outer pipe and is used for measuring the transfer impedance of the high-voltage component sample. Various complex environment conditions can be simulated, the change of the transfer impedance of the high-voltage component is tested, and the influence of the environment conditions on the shielding effectiveness is analyzed.

The invention discloses a multi-harmonic source responsibility quantification method based on asynchronous measurement, and relates to the technical field of electric energy quality harmonics. The method comprises the following steps: measuring harmonic voltage of a concerned bus and harmonic current at a connection point of each harmonic source and the concerned bus to construct an observation signal, and constructing a covariance matrix after centralization and whitening: for the covariance matrix, determining an optimal common orthogonal matrix and reconstructing a source signal matrix; calculating harmonic transfer impedance corresponding to each harmonic source signal based on a fast-changing component model; multiplying each harmonic source signal by the corresponding harmonic transfer impedance to obtain a harmonic voltage of the corresponding harmonic source; and projecting the harmonic voltage to the harmonic voltage of the concerned bus to realize multi-harmonic source responsibility quantification. The method does not depend on a GPS, the operation steps of multi-harmonic source responsibility quantification are simplified, and the quantification efficiency can be improved; meanwhile, the calculation estimation dimension can be reduced through the sparsity of the hybrid matrix, the calculation burden is reduced, and the quantization precision is improved.

The invention discloses an ex-service battery health state assessment method and system, and the method comprises the steps: applying an AC excitation signal in a preset frequency range to a to-be-tested ex-service battery, collecting the impedance response data of the ex-service battery at a plurality of frequency points, and forming an impedance spectrum original data set; the impedance spectrum original data set is processed, and multi-dimensional parameters including high-frequency-band electrolyte resistance characteristics, middle-frequency-band charge transfer impedance characteristics and low-frequency-band diffusion impedance characteristics are extracted; based on the multi-dimensional parameters, a target factor vector representing the health state of the retired battery is constructed, and the target factor vector comprises a capacity attenuation factor and an internal resistance growth factor; inputting the target factor vector into a health state mapping model obtained by training based on a decommissioned battery historical sample, and calculating to obtain a health index of the decommissioned battery to be tested; and according to the health indexes, the retired batteries are divided into different health levels. According to the method, evaluation efficiency and evaluation precision can be considered, and efficient and accurate grading of the retired batteries is realized.

The application provides a cost allocation method and device for an AC-DC hybrid power distribution network based on a distribution factor, which comprises the following steps: constructing an equivalent model of the AC-DC hybrid power distribution network; the equivalent model is used to calculate the transfer impedance of each node of the AC-DC hybrid power distribution network to a branch; based on the equivalent model, the transfer impedance of each node to the branch is calculated, and an augmented distribution factor matrix of the AC-DC hybrid power distribution network is determined; the augmented distribution factor matrix is used to calculate the usage degree of each node of the AC-DC hybrid power distribution network to a line; based on the augmented distribution factor matrix, a cost allocation principle is determined, the cost of the AC-DC hybrid power distribution network is allocated, and an initial cost allocation result is calculated; the cost comprises a fixed cost and a variable cost; based on a generator-load power distribution matrix, the initial cost allocation result is corrected to obtain a cost allocation result. The application can improve the rationality, fairness, applicability and stability of the cost allocation of the AC-DC hybrid power distribution network.

The invention relates to the technical field of electromagnetic compatibility, and discloses a control method for suppressing cable conducted radiation by carbon dioxide laser, which is used for solving the problems of discontinuous shielding and high transfer impedance of a cable-connector transition area. A circle of 360-degree continuous conductive skin is formed in situ in a cable-connector transition area, a radial micro through hole array is arranged in the area, and a 360-degree grading ring at the connector end is combined for primary press fitting, so that a stable circumferential fracture-free closed path is formed among a cable shielding layer, the conductive skin, the grading ring and a shell. The structure geometrically eliminates discontinuity caused by shielding gaps and single-point lap joint in a transition area, and meanwhile, uneven contact and batch difference caused by traditional turning, welding or local crimping are avoided in a multi-point parallel connection and integral press fitting mode. On the basis, the structure can realize stable electromagnetic compatibility under the condition of batch assembly, and is suitable for a high-frequency system sensitive to interference and a complex working condition environment.

The application provides a device and a method for predicting a common-mode disturbance proportion in a disturbance voltage test, the device comprising a high-voltage probe, a damped oscillation wave generator, a cable, an oscilloscope, a current probe and a controller; when the common-mode transfer impedance is determined, the high-voltage probe is connected with the damped oscillation wave generator; when the disturbance voltage of the measured port is measured, the measured port is connected with the high-voltage probe and the damped oscillation wave generator respectively; the controller is connected with the oscilloscope, and is used for calculating the common-mode disturbance proportion based on the measurement result of the oscilloscope. The common-mode voltage and the common-mode current in the measurement circuit are used to obtain the common-mode transfer impedance, and then the common-mode voltage proportion in the disturbance voltage of the measured port is obtained. The method can eliminate the common-mode disturbance voltage component in the port voltage, has the advantages of simple operation, easy implementation, good economy, high safety and the like, and can be widely applied to transient electromagnetic disturbance tests of power system on-site secondary equipment.

This invention discloses a charging method based on an adjustable charging curve for battery health status perception, comprising the following steps: synchronously acquiring voltage and current responses through a micro EIS measurement circuit and obtaining the real and imaginary parts of impedance at different frequencies using Fast Fourier Transform, thereby generating an electrochemical impedance spectrum of the battery during charging and discharging; segmenting and fitting the high-frequency, mid-frequency, and low-frequency regions, extracting characteristic values ​​of ohmic internal resistance, charge transfer impedance, and diffusion impedance respectively, and generating impedance spectrum characteristic parameters; inputting the impedance spectrum characteristic parameters to a control chip to fit and estimate the battery health status assessment value, and constructing a battery health status perception model to dynamically generate an adjustable charging curve; performing a charging operation on the battery according to the adjustable charging curve, and dynamically adjusting the parameters of the adjustable charging curve, thereby achieving closed-loop adaptive adjustment of the charging process. This invention can dynamically adjust the charging curve parameters to achieve closed-loop adaptive adjustment of the charging process.

The invention relates to a single-pole grounding protection method for a complex multi-terminal flexible direct current power distribution network based on a phase space transient mapping trajectory, which is suitable for a multi-terminal flexible direct current system comprising various converters. According to the method, phase space trajectories of currents at two ends of a fault line are constructed, a delay embedded vector is constructed by using dominant frequency, trajectory directivity and main axis offset are extracted, direction criteria and form criteria are formed respectively, and dual identification of internal and external faults is realized. And by combining a virtual breaking point theory and transfer impedance modeling, the universality and accuracy of fault modeling are ensured. The method does not depend on communication and synchronization, has good high-resistance adaptability and anti-noise performance, and is suitable for engineering deployment.

This invention provides an in-situ non-destructive diagnostic method for sodium deposition during low-temperature charging of sodium-ion batteries, belonging to the field of battery diagnostic technology. In this invention, ultrasonic emission, reflection, and transmission receiving modules are arranged along the thickness direction of the battery under test, connected to an electrochemical workstation, constructing a dual-mode ultrasonic detection architecture of transmission and reflection to achieve in-situ non-destructive testing. The battery is adjusted to a fully discharged state, placed in a high-low temperature test chamber, and a room-temperature control group is set up. It is charged with a preset constant current, and AC disturbances are simultaneously applied to drive ultrasonic pulses. Cyclic testing is performed at set time intervals to achieve in-situ, continuous, and synchronous acquisition of electrochemical and ultrasonic data. Charge transfer impedance is extracted based on impedance spectroscopy, interface main echo and layered slice imaging are obtained based on ultrasonic reflection data, and a two-dimensional sound velocity distribution image is established based on ultrasonic transmission data. A multi-signal joint criterion is used to determine sodium deposition and distinguish between early and late stages, effectively improving the accuracy and flexibility of low-temperature sodium deposition diagnosis.

The present invention relates to the technical field of instruments and meters, and specifically provides an impedance measurement method, aiming to solve the technical problem of relatively large measurement errors corresponding to the existing impedance measurement methods. For this purpose, the impedance measurement method of the present invention includes: obtaining an input impedance measurement value of an impedance network based on an impedance measurement component; obtaining an input voltage and an output voltage of the impedance network based on a voltage measurement component; and determining a transfer impedance of the impedance network based on the input impedance measurement value of the impedance network, the input voltage, and the output voltage of the impedance network. In this way, the measurement accuracy is improved.

The present application relates to the field of shielded cable transfer impedance measurement, and particularly relates to a shielded cable transfer impedance measurement method under the condition of impedance mismatch, which improves the precision of shielded cable transfer impedance measurement under the condition of impedance mismatch. The scheme comprises: obtaining an inner loop near-end load Z n and an inner loop far-end load Z f , obtaining an outer loop phase constant β 1 and an inner loop phase constant β 2 , obtaining an internal impedance Z S of a voltage source, obtaining an outer loop far-end load Z L ; testing and calculating an outer loop characteristic impedance Z1 and an inner loop characteristic impedance Z2; testing and calculating a ratio V(L) / V S of a coupling voltage at the far end of the inner loop to an output voltage amplitude of the voltage source and a ratio V(0) / V S of a coupling voltage at the near end to the output voltage amplitude of the voltage source; and calculating the transfer impedance according to the obtained and calculated parameters. The present application is applicable to shielded cable transfer impedance measurement.

The invention discloses an electrostatic discharge target link transfer impedance calibration method, which belongs to the technical field of electrostatic discharge, and comprises the following steps: firstly, connecting the positive electrode of the output end of a direct current source to the input end of a metered ampere meter, and converting the output end of the ampere meter and the negative electrode of the direct current source into an N-type or SMA-type radio frequency cable to be connected with a current target adapter; after the current target adapter is aligned with the electrostatic discharge target, the screws of the through holes are tightened, so that the current target adapter is connected with the inner cores of the electrostatic discharge target, the shells are reliably connected, and the output end of the electrostatic discharge target is connected with an attenuator and then connected with an oscilloscope through a radio frequency cable. According to the calibration method, the current target adapter is connected with the current target, the current target is converted into a common radio frequency connector, the reliability of the calibration system is improved, and measurement errors caused by poor contact are reduced. By introducing the ampere meter, the input current of the input end of the current target is monitored in real time, and the influence factor of inaccurate output current caused by impedance matching is reduced.

The invention discloses a short-circuit current suppression method, device and equipment and a storage medium, and belongs to the technical field of power systems and power electronics, and the method comprises the steps: building an equivalent model of a target power grid, and carrying out the load flow calculation of the equivalent model, and obtaining an initial state; when the initial state accords with an operable state, calculating an admittance matrix based on line parameters and equipment parameters of each line in the equivalent model; the line comprises a bus and a branch line; calculating according to the admittance matrix to obtain an impedance matrix, and obtaining transfer impedance between corresponding buses according to the impedance matrix; establishing a short-circuit current sensitivity index according to the transfer impedance, and determining a target AC line based on the short-circuit current sensitivity index; and replacing the target alternating-current line with a flexible direct-current transmission line so as to suppress the short-circuit current. Therefore, by implementing the method, the problem of low stability caused by non-uniform power flow distribution on the line in the prior art can be solved.

The present invention provides a field-circuit combined method for evaluating high-intensity radiation field conduction interference of aircraft onboard equipment: S1. By simulating the aircraft HIRF effect, the interference current induced by the cable of the onboard equipment is solved. I out ( f );S2. Calculate the shielding effectiveness of the shielded cable through the transfer impedance test of the airborne equipment cable S ( f ); S3. Based on I out ( f ), S ( f ), computer onboard device pin-end interference current I in ( f ); S4. Establish an airborne equipment circuit simulation model; S5. Injection through airborne equipment circuit simulation model simulation analysis I in ( f The present invention solves the problem of predicting and evaluating the HIRF interference of airborne equipment during the HIRF protection design process of aircraft.

The invention relates to the technical field of power system monitoring and control, and discloses a multi-dimensional perception power grid harmonic impedance real-time monitoring and analysis early warning system, which comprises a broadband data acquisition and preprocessing module used for acquiring mixed electric signals and separating voltage and current disturbance components; the harmonic impedance tensor identification module is used for constructing and solving a harmonic transfer impedance matrix for describing the transfer characteristics of the whole network based on the disturbance component; the active detection and calibration module is used for accurately calibrating the harmonic transfer impedance matrix by injecting coding perturbation into a power grid; and the analysis and early warning decision module is used for analyzing and early warning the harmonic stability of the power grid based on the calibrated matrix. According to the invention, a harmonic transmission impedance matrix is constructed by using a power line carrier signal and combining active coding perturbation, and non-intrusive and multi-dimensional monitoring and prospective early warning of the harmonic stability of the power grid are realized.

The invention proposes a power distribution system voltage sag estimation method based on a system impedance matrix, and relates to the technical field of power distribution networks, and the method comprises the steps: S1, defining a voltage sag correlation region based on the transfer impedance correlation of the impedance matrix of a power distribution system, and determining the position of an optimal power quality monitoring point; s2, acquiring a transfer impedance sum ratio of a monitoring node to a non-monitoring node based on the position of the optimal power quality monitoring point, and establishing a linear correlation model of the indexes; s3, analyzing the influence of the number of monitoring points on the voltage sag estimation precision of the power distribution system through multi-scene simulation according to the linear correlation model of the indexes; s4, verifying in an IEEE24 node system network according to an analysis result, and outputting a power distribution system voltage sag estimation result passing verification; the method can directly reflect the physical mechanism of the voltage sag of the power distribution system, avoids the problem of separation from the actual operation characteristics of the power distribution system caused by pure mathematical fitting in the existing method, and is adaptive to the engineering application scene of the power distribution system.

The invention relates to the technical field of cable shielding test, and discloses a shielding effectiveness calculation method based on a multi-conductor transmission line equation, which comprises the following steps of: 1, establishing a cable theoretical model according to an injection method test mode; the cable theoretical model is a structural model of an injection line and a shielding line to be tested; 2, extracting model parameters according to the cable theoretical model, and substituting the model parameters into a distributed parameter extraction program to obtain inter-line distributed capacitance and distributed inductance of the cable; 3, the distributed capacitance and the distributed inductance are substituted into the multi-conductor transmission line equation for decoupling, and current distributed along the line on the shielding layer is obtained; step 4, taking the current as an along-line distributed excitation source of the core wire to obtain a terminal voltage of the core wire; and calculating the transfer impedance of the shielded wire according to an injection method formula. According to the method, a two-dimensional transmission line equation method is adopted, only cross section parameters of the cable need to be input, a complicated modeling process is skipped, and the shielding effectiveness of the braided coaxial shielding cable is effectively calculated.

The invention discloses an intelligent detector for tomography and material recognition. The intelligent detector comprises a shell and a sensor module in the shell. The signal processing module comprises an analog switch matrix, a multi-frequency excitation signal generation unit and a response signal acquisition unit; the calculation control module is used for controlling the channel switching of the analog switch matrix, the generation of a multi-frequency excitation signal and the acquisition of a response signal, and processing the obtained transfer impedance data; the interface module receives an input instruction of a user and transmits the input instruction to the calculation control module; and outputting an image and a material identification result obtained by processing of the calculation control module. Therefore, through the technical means of applying multi-frequency current, measuring the electrical impedance distribution of an object under different frequencies and further identifying the material type according to the difference of the electrical impedance characteristics of different materials, uniform detection response is achieved to eliminate the end effect, high-precision material type identification is achieved, and wood, metal, PVC and other materials are accurately distinguished.