CN-121978488-A - Wire and cable conductor insulation performance inspection method

CN121978488ACN 121978488 ACN121978488 ACN 121978488ACN-121978488-A

Abstract

The invention belongs to the technical field of wire and cable detection, and particularly discloses a wire and cable conductor insulation performance inspection method, which aims to solve the problem that insulation microscopic degradation is difficult to identify early by a traditional electrical measurement method. The method comprises the steps of applying nanosecond voltage pulse excitation to conductors to excite mechanical vibration waves in an insulating medium, collecting shear wave time domain signals by utilizing an acoustic sensor array surrounding a cable, extracting propagation speed, calculating elastic modulus spatial distribution by an inverse problem reconstruction algorithm, synchronously obtaining partial discharge signal characteristics, carrying out space-time alignment fusion on the two signals, constructing a comprehensive evaluation model, and outputting quantification results of micro mechanical embrittlement degree and irreversible heat aging grade. According to the invention, by introducing the shear wave elastography principle and combining with multisource information fusion analysis, nondestructive and high-sensitivity early diagnosis of the insulation state of the in-service cable is realized, the early warning capability is improved, and the method is suitable for online detection and intelligent operation and maintenance of various laying scenes.

Inventors

DAI XIKANG
AI JINTAO
LIU HONGBO
YANG SHAOBO
HE XINGUO
Wu Dieou
WANG MIN
ZHANG WEI
NA BO
ZHANG XUEDAN
ZHANG SHUSEN
ZHANG HAINING
Yu Shuze

Assignees

天津市产品质量监督检测技术研究院

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. The method for inspecting the insulation performance of the wire and cable conductor is characterized by comprising the following steps of: Applying voltage pulse excitation with preset amplitude and pulse width to conductors of the tested wires and cables to enable mechanical vibration waves to be generated inside the insulating medium due to electrostriction effect; Synchronously acquiring a time domain signal of the mechanical vibration wave propagating in an insulating medium by using an acoustic sensor array which is circumferentially arranged on the outer surface of the cable; Adopting an inverse problem reconstruction algorithm to calculate elastic modulus values corresponding to all areas in the insulating medium according to the propagation velocity information and generating a spatial distribution diagram; Synchronously collecting partial discharge signals generated in the process of applying the voltage pulse excitation, and extracting the amplitude, phase and repetition frequency characteristics of the partial discharge signals; Space distribution diagram and the partial discharge signal characteristics are subjected to space-time alignment and data fusion, and an insulation state comprehensive evaluation model is constructed; outputting the micro mechanical embrittlement degree and the irreversible heat aging grade of the insulating medium according to the comprehensive evaluation model.
2. The method for testing the insulation performance of the wire and cable conductor according to claim 1, wherein the step of applying voltage pulse excitation with preset amplitude and pulse width to the conductor of the wire and cable to be tested comprises the steps of adopting unipolar or bipolar square wave pulse for the voltage pulse excitation; The amplitude of the voltage pulse excitation is adaptively adjusted according to the rated voltage level of the tested wire and cable, and the width of the voltage pulse excitation is in the interval of 50 nanoseconds to 500 nanoseconds; The change rate of the electric field generated by the rising edge time of the voltage pulse excitation promotes the molecules inside the insulating medium to generate instantaneous polarization orientation and displacement, so as to induce high-frequency mechanical strain.
3. The method for testing the insulation performance of a wire and cable conductor according to claim 2, wherein the method for synchronously collecting the time domain signal of the mechanical vibration wave propagating in the insulation medium by using an acoustic sensor array surrounding the outer surface of the cable comprises the steps that the acoustic sensor array comprises a piezoelectric ceramic sensor or a fiber bragg grating sensor; the acoustic sensor array is integrated in the flexible annular clamp and is attached to the surface of the metal shielding layer or the outer sheath of the cable; The acoustic sensor array is of a two-dimensional sensing network structure in space, is arranged at preset intervals along the axial direction of the cable, and is uniformly distributed with a plurality of sensing units in the circumferential direction of each axial section, and the sensing units are used for capturing the propagation characteristics of shear waves in three dimensions of the radial direction, the axial direction and the circumferential direction.
4. The method for testing the insulation performance of the electric wire and cable conductor according to claim 3, wherein the method for extracting propagation speed information of the shear wave at different positions in the insulation medium based on the collected time domain signals comprises the steps of carrying out band-pass filtering pretreatment on the time domain signals received by each channel to filter out low-frequency electromagnetic interference and high-frequency system noise; The process of extracting the shear wave propagation velocity is achieved by performing a cross-correlation analysis on signal sequences received by two sensors adjacent in the wave propagation direction; The cross-correlation analysis comprises the steps of intercepting an effective data segment containing first wave head oscillation by utilizing a sliding window mechanism, calculating a time offset corresponding to the cross-correlation function reaching the maximum value, and determining the time offset as the time delay of propagation of shear waves in the distance between two sensors; Calculating the wave velocity of the local area by using the quotient of the physical distance between the sensors and the time delay; In the processing process of the cross-correlation analysis, hilbert transformation is firstly carried out on the signal sequence to extract the instantaneous envelope of the signal, so that the influence of phase fluctuation on time delay estimation is reduced; calculating the integral value of the product of the two envelope sequences on a time axis, and searching the time offset for maximizing the integral value by continuously translating the signal sequence; Fitting discrete data near the cross-correlation peak value points by adopting a parabolic interpolation method to obtain the time delay precision of a sub-sampling period; And the sliding window continuously scans the acquired sequence signals, and extracts and reflects the wave velocity evolution rule along the axial direction and the circumferential direction inside the insulating medium.
5. The method for testing the insulation performance of a wire and cable conductor according to claim 4, wherein the method for calculating the value of the elastic modulus corresponding to each region in the insulation medium according to the propagation speed information by adopting an inverse problem reconstruction algorithm and generating a spatial distribution diagram comprises the steps of establishing a mapping relation between a shear wave speed and a material mechanical parameter; the mapping relation satisfies that the square of the propagation speed of the shear wave in the isotropic medium is equal to the quotient of the shear modulus and the density; The inverse problem reconstruction algorithm adopts an iterative optimization strategy, takes the acquired multipath wave velocity observation value as a constraint condition, and solves the elastic modulus value of each voxel in the three-dimensional space grid inside the insulating medium by minimizing the residual square sum between the actual measured wave velocity and the theoretical model predicted wave velocity; the space distribution map is stored in a three-dimensional matrix form, and each coordinate point corresponds to a specific elastic modulus value; In each iteration, calculating theoretical propagation time on each observation path by utilizing a forward model of a wave equation according to the current initial value of the elastic modulus; calculating residual vectors between the actual measurement time and the theoretical propagation time, and constructing a jacobian matrix reflecting the sensitivity of the wave velocity to local elastic modulus change; And updating the elastic modulus value by solving a linear equation set until the two norms of the residual error are reduced below a preset convergence threshold value.
6. The method for testing insulation performance of a wire and cable conductor according to claim 5, wherein the step of synchronously collecting partial discharge signals generated during the excitation of the voltage pulse comprises the steps of obtaining current signals by using a high-frequency current transformer or a capacitive coupling probe mounted on a cable terminal ground down conductor; The sampling frequency of the partial discharge signal is not lower than 100 MHz; the extracted features comprise apparent amplitude of discharge charge quantity, phase distribution condition relative to excitation pulse period and pulse repetition frequency in preset observation time; the partial discharge signal reflects the electric weakness distribution of the insulating medium under the action of an electric field and is complementary with the mechanical weakness reflected by the elastic modulus value.
7. The method for testing insulation performance of a cable conductor according to claim 6, wherein the step of performing space-time alignment and data fusion on the spatial distribution pattern and the partial discharge signal characteristic to construct an insulation state comprehensive evaluation model comprises the steps of: Correlating the space coordinates of the acoustic signal positioning with the time of partial discharge signal generation according to the sound velocity propagation delay; The data fusion process adopts a multi-source information weighting association strategy and is realized by establishing a multi-dimensional feature vector containing an elastic modulus deviation degree, partial discharge amplitude density and a clustering index of discharge phase; The weighted association strategy comprises the steps of judging the coincidence relation between the elastic modulus decreasing region and the partial discharge active region in space topology, judging that the position is a high-risk aging point if coincidence exists, and giving higher confidence weight according to association strength; In the data fusion process, the determination of the weight matrix is based on the information entropy principle, and the weight coefficient of the elastic modulus characteristic and the partial discharge characteristic is dynamically adjusted by analyzing the mutual contribution degree of the elastic modulus characteristic and the partial discharge characteristic when the known defect sample is identified; When the operation period of the tested cable exceeds a preset old threshold value, the weight of the elastic modulus characteristic is increased; When the tested cable is in a new installation stage, focusing on the partial discharge characteristic to capture the construction process defect; and the comprehensive evaluation model calculates a comprehensive score representing the insulation health degree by introducing nonlinear fusion weight.
8. The method for testing insulation performance of a wire and cable conductor according to claim 7, wherein outputting the micromechanical embrittlement degree and the irreversible heat aging degree of the insulation medium according to the comprehensive evaluation model comprises: The micro mechanical embrittlement degree is characterized by calculating the relative ratio of the local elastic modulus average value obtained by current measurement to the reference elastic modulus value of the same type of cable in a new cable state; The irreversible heat aging grades are divided into a normal operation grade, an early aging grade, a medium-term degradation grade and a serious critical grade according to a plurality of preset discrete threshold intervals; When the relative ratio is reduced to a first threshold value, the system sends out early warning of mechanical property degradation; When the relative ratio is below a second threshold and the partial discharge frequency exceeds the background noise threshold, a severe critical grade is determined.
9. The method for testing insulation performance of a wire and cable conductor according to claim 8, further comprising the step of creating a history detection database for storing a spatial profile, partial discharge characteristic data, and environmental parameters obtained by a past test; Carrying out time sequence analysis on detection data of the same cable at different time nodes by using a pattern recognition algorithm, and recognizing the evolution rule of the aging trend; calculating an aging rate, wherein the aging rate is the change rate of elastic modulus along with running time; And calculating the residual effective life of the cable based on the aging rate.
10. The method for testing the insulation performance of a wire and cable conductor according to claim 9, further comprising the step of monitoring the temperature and humidity of the cable environment in real time before the test; Acquiring real-time temperature field data by using a temperature measuring device arranged on the surface of the cable; introducing environmental parameters as correction factors into the calculation process of the elastic modulus value; And normalizing the calculated elastic modulus by using a pre-calibrated temperature compensation curve to eliminate the interference of external environment fluctuation on the sound wave propagation speed.

Description

Wire and cable conductor insulation performance inspection method Technical Field The invention belongs to the technical field of wire and cable detection, and particularly relates to a wire and cable conductor insulation performance inspection method. Background With the continuous advancement of electric infrastructure construction, the electric wires and cables serve as core carriers for energy transmission, and the integrity of the insulation layers of the electric wires and cables plays an irreplaceable role in maintaining long-term stable operation of the whole power grid system. The insulating medium is subjected to multiple coupling effects of electric field stress, thermal load and mechanical stress during long-term operation, and the physical and chemical properties of the insulating medium slowly and complexly evolve. In order to ensure the operation safety of the power system, real-time monitoring and periodic evaluation of the insulation performance of the cable have become key subjects for research in the field of power maintenance. The test of the insulation performance of the electric wires and cables is mainly focused on capturing and diagnosing the electrical parameters of the medium, and aims to predict the insulation failure risk through a specific detection means. Conventional performance evaluation generally depends on applying a high-voltage load to a conductor, and collecting key indexes such as partial discharge pulse or leakage current intensity in real time to determine an electrical response condition of an insulating layer in a strong electric field environment. This detection mode focuses on end recognition of insulation failure results, attempting to indirectly map the electrical strength and operational life of the insulation material through abnormal fluctuations in electrical parameters. The traditional electrical measurement method is difficult to effectively judge the internal micro mechanical embrittlement and early irreversible thermal aging degree before the insulation material is subjected to dominant electrical breakdown or macroscopic air gap discharge, so that the detection result has obvious hysteresis in early warning and prevention. The prior art scheme excessively depends on the sensitivity of electrical characteristics, lacks the perceptibility of the evolution of microscopic mechanical parameters of an insulating medium, and cannot realize nondestructive quantitative evaluation of the insulating layer in the stage of no electrical damage. Meanwhile, the traditional evaluation system is difficult to deeply fuse the acoustic mechanical response and the electrical state characteristics, so that the accurate characteristic extraction and association algorithm is lacking when the multi-source heterogeneous signals are faced, and an intuitive and high-precision physical state sensing system cannot be constructed. Disclosure of Invention The invention aims to provide a method for checking the insulation performance of a wire and cable conductor, which solves the problems in the background technology. In order to achieve the above object, the present invention provides a method for inspecting insulation performance of a wire and cable conductor, comprising the steps of: Applying voltage pulse excitation with preset amplitude and pulse width to conductors of the tested wires and cables to enable mechanical vibration waves to be generated inside the insulating medium due to electrostriction effect; Synchronously acquiring a time domain signal of the mechanical vibration wave propagating in an insulating medium by using an acoustic sensor array which is circumferentially arranged on the outer surface of the cable; Adopting an inverse problem reconstruction algorithm to calculate elastic modulus values corresponding to all areas in the insulating medium according to the propagation velocity information and generating a spatial distribution diagram; Synchronously collecting partial discharge signals generated in the process of applying the voltage pulse excitation, and extracting the amplitude, phase and repetition frequency characteristics of the partial discharge signals; Performing space-time alignment and data fusion on the spatial distribution map and the partial discharge signal characteristics to construct an insulation state comprehensive evaluation model; outputting the micro mechanical embrittlement degree and the irreversible heat aging grade of the insulating medium according to the comprehensive evaluation model. Preferably, the method for applying voltage pulse excitation with preset amplitude and pulse width to the conductor of the tested wire and cable comprises the steps of adopting unipolar or bipolar square wave pulse for the voltage pulse excitation; The amplitude of the voltage pulse excitation is adaptively adjusted according to the rated voltage level of the tested wire and cable, and the width of the voltage pulse excitation is in the interval of 5