CN117741356B - Lightning arrester valve plate aging evaluation method, medium and system under complex working conditions - Google Patents
Lightning arrester valve plate aging evaluation method, medium and system under complex working conditions Download PDFInfo
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Abstract
The invention provides a method, medium and system for evaluating aging of a valve plate of an arrester under a complex working condition, belonging to the technical field of aging of the arrester, and comprising the following steps: acquiring an ultrasonic signal received by an ultrasonic sensor arranged on a grounding end of a valve plate of the lightning arrester to be tested; preprocessing the ultrasonic signal to obtain a preprocessed ultrasonic signal; extracting frequency domain features of the preprocessed ultrasonic signals; deleting characteristics formed by valve plate metal parts of the lightning arrester to be detected in the frequency domain characteristics to generate a characteristic matrix; inputting the characteristic matrix into a pre-trained characteristic matrix-equivalent resistance network model to obtain an equivalent resistance network of a valve plate of the lightning arrester to be tested, and marking the equivalent resistance network as the equivalent resistance network to be tested; calculating a path from the starting point to the end point of the equivalent resistance network to be measured, and marking the path as a conductive path; the ratio of the number of the conductive paths to the number of the total paths is taken as the availability index of the lightning arrester valve plate, and the aging of the lightning arrester valve plate is=1-the availability index.
Description
Technical Field
The invention belongs to the technical field of lightning arrester aging, and particularly relates to a lightning arrester valve plate aging evaluation method, medium and system under complex working conditions.
Background
With the rapid development of power systems, the application of high-capacity converter devices is increasingly widespread, which makes the electromagnetic environment more complex, and the power devices face higher overvoltage risks. The lightning arrester is an important overvoltage protection device, and the aging of the insulation performance of the lightning arrester can seriously affect the protection level of the lightning arrester. The current insulation aging evaluation method of the lightning arrester mainly comprises an electrical test method and an anatomic test method. The electrical test method is an indirect method in which the degree of aging is reflected by the insulation resistance of the sample, but the aging reflected by this method is not accurate enough due to the presence of discharge, low leakage current, and the like. The anatomic test method requires dismantling of field devices, cannot realize online real-time monitoring, and cannot meet actual production requirements. In addition, the current test standard of the lightning arrester only aims at the performance index under the normal use state, and no aging evaluation method aims at abnormal conditions such as complex alternating current, direct current, lightning overvoltage and the like. Therefore, a novel detection technology capable of directly and rapidly evaluating insulation aging conditions of the lightning arrester under complex working conditions on site and realizing online real-time monitoring is needed.
Disclosure of Invention
In view of the above, the invention provides a method, medium and system for evaluating the aging of a valve plate of a lightning arrester under complex working conditions, which can solve the technical problem that the aging of the valve plate of the lightning arrester cannot be evaluated on line in the prior art.
The invention is realized in the following way:
The first aspect of the invention provides a lightning arrester valve plate aging evaluation method under a complex working condition, which comprises the following steps:
s10, acquiring an ultrasonic signal received by an ultrasonic sensor arranged on a grounding end of a valve plate of the lightning arrester to be tested, wherein the ultrasonic signal is sent out by an ultrasonic transmitter arranged on a line end of the valve plate of the lightning arrester to be tested;
s20, preprocessing an ultrasonic signal to obtain a preprocessed ultrasonic signal;
S30, extracting frequency domain characteristics of the preprocessed ultrasonic signals;
S40, deleting characteristics formed by the valve plate metal part of the lightning arrester to be detected in the frequency domain characteristics to generate a characteristic matrix;
S50, inputting the characteristic matrix into a pre-trained characteristic matrix-equivalent resistance network model to obtain an equivalent resistance network of a valve plate of the lightning arrester to be tested, and marking the equivalent resistance network as the equivalent resistance network to be tested;
S60, calculating a path from a starting point to an end point of the equivalent resistance network to be detected, and marking the path as a conductive path;
s70, taking the ratio of the number of the conductive paths to the number of all paths as an available index of the lightning arrester valve plate, wherein the aging = 1-available index of the lightning arrester valve plate;
The equivalent resistance network takes a line end of a lightning arrester valve plate as a starting point and takes a grounding end as an end point, and comprises a first number of resistance nodes, wherein the first number of resistance nodes are connected in a random interconnection mode, and each node is connected with 1-second number of other nodes; the resistance of the whole equivalent resistance network is equal to the resistance of the lightning arrester valve plate in the common state.
Based on the technical scheme, the aging evaluation method of the valve plate of the lightning arrester under the complex working condition can be further improved as follows:
The specific method for preprocessing the ultrasonic signals comprises the following steps: pre-emphasis is carried out on the collected ultrasonic signals to improve the amplitude of the high-frequency component; removing noise by adopting a wavelet transformation method; designing a digital filter to realize low-pass filtering smooth signals; the extracted signal envelope reflects the signal strength variation.
Further, the step of extracting the frequency domain feature of the preprocessed signal specifically includes: dividing the preprocessed ultrasonic signal into a plurality of frames of short signals; and a window function is adopted for each frame of short signal, and frequency domain characteristics are obtained through fast Fourier transform.
Further, the step of deleting the feature formed by the metal part of the valve plate of the lightning arrester to be detected in the frequency domain feature to generate the feature matrix specifically includes: obtaining or simulating a metal part signal; comparing with the difference of the measurement characteristic matrix; extracting principal difference features using principal component analysis; the method of applying the support vector machine identifies classification deletion independent features.
Further, the building and training modes of the feature matrix-equivalent resistance network model specifically comprise:
building a training sample, acquiring a plurality of lightning arrester valve plates, obtaining characteristic matrixes of the plurality of lightning arrester valve plates, and building an equivalent matrix according to the resistance of the lightning arrester valve plates in a common state and the resistance of the lightning arrester valve plates in an overvoltage state;
establishing a model prototype, and establishing the model prototype by adopting a BP neural network;
Training the model prototype, and training the model prototype by using a training sample to obtain the feature matrix-equivalent resistance network model.
Further, the step of calculating a path from the start point to the end point of the equivalent resistance network to be measured specifically includes:
confirming that the starting point of the equivalent resistance network is a line end of a valve plate of the lightning arrester and the end point is a grounding end;
Adopting breadth-first search algorithm to start layer by layer to spread all nodes and paths traversing the network from the starting point, adding newly accessed nodes into a queue, and dequeuing the accessed nodes;
in the traversal process, the paths are traced back through the pointer, and the found reachable paths between all starting points are stored;
the number of discovered paths is counted as the number of conductive paths in the equivalent resistor network.
Wherein the first number is greater than 10000; the second number is greater than 64; and the second number is smaller than the first number.
Further, the first number = 1000000; the second number=1024.
The second aspect of the present invention provides a computer readable storage medium, where the computer readable storage medium stores program instructions, where the program instructions are used to execute the above-mentioned method for evaluating aging of a valve plate of an arrester under a complex working condition when the program instructions run.
The third aspect of the invention provides an aging evaluation system for a valve plate of an arrester under a complex working condition, wherein the aging evaluation system comprises the computer-readable storage medium.
Compared with the prior art, the lightning arrester valve plate aging evaluation method, medium and system provided by the invention have the beneficial effects that: through signal analysis and feature extraction, a mapping relation between the feature and a valve plate equivalent resistance network model is established, insulation availability of the valve plate is evaluated through analysis of the equivalent resistance network, and accurate evaluation of aging degree of insulation of the lightning arrester under complex working conditions can be achieved. Compared with the existing electrical test method, the invention actually detects the ultrasonic wave of the lightning arrester, and has high accuracy; compared with an anatomic test method, the method is used for on-site direct and on-line detection; the technical problem that the aging of the valve plate of the lightning arrester cannot be evaluated on line in the prior art is solved.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments of the present invention will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method provided by the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
As shown in fig. 1, the first aspect of the present invention provides a flow chart of a method for evaluating aging of a valve plate of an arrester under a complex working condition, where the method includes the following steps:
s10, acquiring an ultrasonic signal received by an ultrasonic sensor arranged on a grounding end of a valve plate of the lightning arrester to be tested, wherein the ultrasonic signal is sent out by an ultrasonic transmitter arranged on a circuit end of the valve plate of the lightning arrester to be tested;
s20, preprocessing an ultrasonic signal to obtain a preprocessed ultrasonic signal;
S30, extracting frequency domain characteristics of the preprocessed ultrasonic signals;
S40, deleting characteristics formed by the valve plate metal part of the lightning arrester to be detected in the frequency domain characteristics to generate a characteristic matrix;
S50, inputting a characteristic matrix into a pre-trained characteristic matrix-equivalent resistance network model to obtain an equivalent resistance network of a valve plate of the lightning arrester to be tested, and marking the equivalent resistance network as the equivalent resistance network to be tested;
s60, calculating a path from a starting point to an end point of the equivalent resistance network to be measured, and marking the path as a conductive path;
s70, taking the ratio of the number of the conductive paths to the number of all paths as an available index of the lightning arrester valve plate, wherein the aging = 1-available index of the lightning arrester valve plate;
the equivalent resistance network takes a line end of a lightning arrester valve plate as a starting point and takes a grounding end as an end point, and comprises a first number of resistance nodes, wherein the first number of resistance nodes are connected in a random interconnection mode, and each node is connected with 1 to a second number of other nodes; the resistance of the whole equivalent resistance network is equal to the resistance of the lightning arrester valve plate in the common state.
The following describes the specific embodiments of the above steps:
S10 detailed description of the steps
1) Selecting an appropriate ultrasonic sensor
A sensor with a moderate frequency range, typically 200K-10MHz, needs to be selected here. Too high a frequency causes severe attenuation, and too low a frequency causes insufficient resolution. Parameters such as sensitivity, directivity, temperature stability of the sensor are also required to be considered.
2) Determining the installation position of an ultrasonic sensor
The position of the grounding end of the lightning arrester valve plate, which has uniform hardness and no obvious damage, needs to be selected. The direction of the sound beam is vertical to the surface of the valve plate, so that good contact is ensured, and the reflected signal is convenient to receive.
3) Connection sensor and data acquisition system
The weak analog signal output by the sensor needs to be digitized after amplified and filtered. The signals are collected into a computer through an A/D converter. It is also necessary to design a hardware filter circuit to suppress noise.
4) Starting an ultrasonic transmitter to transmit signals
And selecting a proper pulse mode, and controlling parameters such as pulse width, repetition frequency and the like. Adjustment is required to achieve the optimum probe depth.
5) Recording and storing analog signals received from the sensor
This is the original signal, including the useful signal and noise. Subsequent steps are processed and analyzed based on the signal.
Detailed description of the step S20
1) Analog signal pre-emphasis
The amplitude of the high frequency component in the signal is boosted using analog or digital methods. This may improve the effect of subsequent filtering and transformation.
2) Wavelet transform denoising
And selecting proper mother wavelet and decomposition level, extracting useful signals and removing noise. Common wavelets include Db, sym, etc.
3) Low pass filtering smooth signal
A digital FIR or IIR filter is designed with a cut-off frequency slightly higher than the signal's highest frequency. The mixed high-frequency noise can be effectively removed.
4) Signal envelope processing
The signal envelope, i.e. the domain amplitude, is extracted by Hilbert transform and other methods. Reflecting the signal strength variation.
Specific embodiment of step S30
1) Splitting signals
The long-time signal is divided into a plurality of frames of short signals, so that the subsequent processing is convenient. The appropriate frame length is determined, preferably 512-2048 points.
2) Window intercept signal
Typically windowed per frame, such as a Hamming window. Frequency spectrum leakage can be eliminated, and frequency domain analysis accuracy can be improved.
3) Fourier transform
And (5) rapidly calculating FFT (fast Fourier transform) for each frame of signal to obtain complex frequency domain characteristics. Including amplitude features and phase features.
4) Feature normalization
And eliminating the influence of the signal energy on the characteristic value by methods such as amplitude normalization and the like.
5) Feature selection
The amplitude characteristic and the phase characteristic are taken as frequency domain characteristics.
Detailed description of the step S40
1) Collecting or simulating metal part signals
The ultrasonic frequency domain characteristics of the metal component are obtained through testing or simulation.
2) Comparison with measurement feature matrix
And finding out the difference between the measured characteristic matrix and the ideal characteristic matrix. The differences reflect, in part, material aging information.
3) Principal component analysis
And extracting main difference features by a PCA method, deleting redundant repeated information, and obtaining a feature matrix.
4) Pattern recognition removal of extraneous features
And carrying out pattern classification recognition by using SVM, BN and other methods, and deleting irrelevant features.
Detailed description of the S50 step
1) BP neural network is built
And determining the number of nodes of the input layer as the dimension of the feature matrix, and determining the nodes of the output layer as the equivalent resistance.
2) Network training
Training by using a large number of characteristic matrixes of valve plates with known quality and corresponding resistance data to obtain a characteristic-resistance mapping model.
3) Model evaluation
And (5) verifying the predicted performance of the model, entering the next step if the model passes, otherwise, returning to modify the network structure and the training parameters.
The specific implementation manner of calculating the path (i.e. the conductive path) from the starting point to the end point of the equivalent resistance network to be measured in the step S60 is as follows:
1) Confirming starting point and end point of equivalent resistance network
And (5) determining the starting point of the equivalent resistance network to be detected as the line end of the lightning arrester valve plate and the end point of the equivalent resistance network to be detected as the grounding end of the lightning arrester valve plate according to the equivalent resistance network to be detected obtained in the step (S50).
2) Searching for all reachable paths using breadth-first search algorithm
From the starting point, traversing the equivalent resistance network according to a strategy of layer-by-layer expansion, and finding a new reachable path when expanding one layer. The specific implementation method is that a queue is used for storing the nodes to be expanded, the newly accessed nodes are enqueued, and the head nodes are dequeued after expansion.
3) Path reproduction
And recording the father pointer at the same time in the expansion process, and pointing to the node at the previous stage of the current node. When the end point is searched, the entire path can be restored by recursively searching the parent.
4) Storing all resulting reachable paths
And storing all the reachable paths between the start and stop points found in the searching process, including information of each node on the path. These paths are the conductive paths in the equivalent resistor network.
5) Counting the number of paths
The number of reachable paths, i.e. the total number of conductive paths from the start point to the end point in the equivalent resistor network, is recorded. The availability index is then calculated on the basis of this.
Through the implementation of the flow, all the conductive paths in the equivalent resistance network can be obtained efficiently, and data support is provided for subsequent analysis and calculation.
In the step S70, the ratio of the number of the conductive paths to the number of all paths is used as the availability index of the valve block of the lightning arrester, and the specific implementation mode for evaluating the aging degree of the valve block of the lightning arrester is as follows:
1) Calculating the number of all possible paths in the equivalent resistance network
And calculating all possible path numbers from the starting point to the end point in the equivalent resistance network through a mathematical derivation or traversal simulation mode according to the number of network nodes and the connection relation of the network nodes.
2) Regularized number of steerable paths
And (3) regularizing the number of the conductive paths obtained by statistics in the step (S60) to map the number of the conductive paths to the [0,1] interval. The regularization function can be selected from Sigmoid, tanh and the like, and can be designed in a self-defined way.
3) Calculating a usable index
Dividing the regularized guidable path number by the total possible path number to obtain the availability index of the equivalent resistance network, wherein the availability index reflects the guidable capacity of the network.
4) Determining an aging level
Subtracting the available index from 1 to obtain the ageing degree evaluation value of the lightning arrester valve plate. The quantity can intuitively reflect the damaged percentage of the insulating property of the valve plate.
5) Setting an aging determination threshold
Several thresholds for the aging determination level are set according to different application environments. And finally judging the grade of the aging degree of the lightning arrester valve plate according to the aging evaluation quantity.
The following is a specific embodiment of the present invention:
S10 detailed description of the steps
When selecting the sensor, parameters such as the center frequency f c, the frequency range, the frequency response curve and the like need to be considered. The center frequency is related to the depth of detection and the frequency range determines the size of defects that can be detected. Its frequency response satisfies the gaussian distribution:
the sensor is arranged on the surface of the valve plate to be measured in a contact way The normal vector direction is
The signal acquisition system comprises an amplifier, a band-pass filter and an A/D converter. The magnification is G, and the relation is satisfied:
Uout＝GUin
if the sampling frequency is f s, the sampling interval Acquisition discretizes the analog signal:
x(n)＝x(nΔt)，n＝0，1，...N-1
Detailed description of the step S20
The signal pre-emphasis is realized by adopting first-order high-pass filtering:
Wherein μ is a pre-emphasis coefficient ranging between [0,1 ]. Too small results are not obvious and too large results introduce distortion.
And (5) adopting wavelet transformation to realize signal denoising.
Specific embodiment of step S30
The hamming window function is used for each frame of signal:
For each frame, a fast fourier transform is used for frequency domain conversion:
the normalization process suppresses the amplitude variation influence:
The frequency points with the largest energy are selected to form feature vectors for classification.
Detailed description of the step S40
1) Collecting or simulating metal part signals
The ultrasonic frequency domain characteristics of the metal component are obtained through testing or simulation.
2) Comparison with measurement feature matrix
And finding out the difference between the measured characteristic matrix and the ideal characteristic matrix. The differences reflect, in part, material aging information.
3) Principal component analysis
And extracting main difference features by a PCA method, deleting redundant repeated information, and obtaining a feature matrix.
4) Or removing extraneous features using pattern recognition
And carrying out pattern classification recognition by using SVM, BN and other methods, and deleting irrelevant features.
Detailed description of the S50 step
The number of the input layer nodes is the number of columns of Z, and the number of the output layer nodes is the number of resistors. The hidden layer node number generally takes the average of the input and output layer node numbers.
The hidden layer output function adopts a hyperbolic tangent function:
yk＝aktanh(bkzk) (12)
Wherein z is hidden layer input, and a and b are parameters. The output layer outputs linearly.
And taking the mean square error as a loss function, and training a model by adopting an LM algorithm.
Specific embodiment of steps S60-S70
The equivalent network connects a first number of nodes using an ER model:
lambda is the average node degree. All paths are generated according to probability distribution.
Calculating the network communication rate:
Wherein the numerator is the starting and ending point reachable path number, and the denominator is the total path number. The final ageing index is 1-R c.
The details of the algorithm for each step are specifically set forth above. The characteristics of the algorithm are fully considered, and the aging evaluation task is customized and optimized, so that the accuracy is improved.
The specific implementation process of the establishment of the equivalent resistance network can be expressed by the following formula:
1. determining the node number N as a preset first number:
N=first number
2. Generating an adjacency matrix A:
Wherein the connection probability p (k) is:
Each node is guaranteed to be connected to 1 to a second number of other nodes.
3. Calculating resistance value distribution parameters:
if the equivalent total resistance of the valve plate in the common state is R, the average resistance of the single resistance node is
4. Constructing a network G:
G＝(V，E，r)
v-first number of nodes
E-corresponds to the non-zero element (i, j) inA
R-according toSetting resistance value
5. The analysis network evaluates the degree of aging.
The above constitutes an equivalent resistance network modeling process consistent with the description.
The specific implementation formulas of the building and training modes of the feature matrix-equivalent resistance network model are expressed as follows:
1. Collecting M lightning arrester valve plates, and extracting a frequency domain feature matrix X:
X＝x1,x2,...,xM,xi∈RN
2. The common state resistance r n and the overvoltage resistance r o of each valve plate are measured, and a tag matrix Y is constructed:
3. Establishing a BP neural network, wherein the number of nodes at an input layer is N, the number of nodes at an output layer is 2, and the number of nodes at a hidden layer is P:
f(x)＝g(W2g(W1x+b1)+b2)
4. Training the network, updating the parameter W 1,W2,b1,b2:
5. and obtaining a mapping model f * of the final characteristic matrix X to the resistance matrix Y.
Wherein the first number is greater than 10000; the second number is greater than 64. Preferably, the first number = 1000000; the second number=1024. The larger the first number, the more accurate.
Specifically, the principle of the invention is as follows:
In the long-term use process of the lightning arrester valve plate, the oxidation layer and the dielectric layer of the lightning arrester valve plate are physically damaged due to the influences of overvoltage, current and environmental factors.
The ultrasonic detection utilizes the interaction of high-frequency sound waves and material defects, and can directly collect information of the internal structure and damage of the material. After the current enters the lightning arrester, the current passes through the main insulating layer of the valve plate and then reaches the metal cover and the base. The damage of the valve plate detected by ultrasonic waves can reduce the upper conductivity of the ultrasonic waves, so that the acoustic wave path is blocked.
And establishing an equivalent resistance network according to the valve plate frequency domain characteristics, and simulating the conductivity of current passing through. The change of the resistance value among the nodes reflects the damage characteristic of ultrasonic detection and represents the influence of the local insulation defect of the valve plate on the overall conduction. The fewer all conducting paths from the start point to the end point in the equivalent resistance network, the serious damage to the insulation network is indicated.
The specific principle analysis is as follows:
1. Scattering effect of ultrasonic waves on cracks and micro-cavities
The piezoelectric transducer receives the reflected sound wave, and the changes of the frequency spectrum and the time domain waveform of the reflected sound wave can quantitatively analyze the properties of the cavity and the crack, such as:
Direction and position-determining time to reach sensor
Size-impact attenuation and response bandwidth
Shape-changing reflection coefficient and frequency characteristics
Quantity and distribution status-echo superposition effect
2. Insulating layer damage affects sound wave transport channel
The crack blocks the propagation path of the ultrasonic wave, reduces the effective range of the sound pressure, and blocks part or all of the paths between the connection ports. The sound beam is closed by damage and attenuated in the direction and energy after isolation, and finally the probe cannot receive the reflected signal.
3. Equivalent circuit network simulation sound wave path and impedance relation
Damage node resistance ∈ → reduction of communication branches → reduction of reachable paths of start-stop nodes → reduction of communication capability of an insulating network → difficulty in passing current, and insulation performance ∈.
The heavier the lesion, the faster the reachable path/total path ratio drops. And when the ratio is lower than the threshold value, judging that the valve plate is damaged and fails.
By combining the theory of ultrasonic propagation and the circuit theory, the corresponding relation between the characteristic damage and the insulation property change is constructed through an equivalent model, so that the sensitivity prediction which cannot be achieved by the traditional indirect detection technology is realized.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (10)
1. The lightning arrester valve plate aging evaluation method under the complex working condition is characterized by comprising the following steps of:
s10, acquiring an ultrasonic signal received by an ultrasonic sensor arranged on a grounding end of a valve plate of the lightning arrester to be tested, wherein the ultrasonic signal is sent out by an ultrasonic transmitter arranged on a line end of the valve plate of the lightning arrester to be tested;
s20, preprocessing an ultrasonic signal to obtain a preprocessed ultrasonic signal;
S30, extracting frequency domain characteristics of the preprocessed ultrasonic signals;
S40, deleting characteristics formed by the valve plate metal part of the lightning arrester to be detected in the frequency domain characteristics to generate a characteristic matrix;
S50, inputting the characteristic matrix into a pre-trained characteristic matrix-equivalent resistance network model to obtain an equivalent resistance network of a valve plate of the lightning arrester to be tested, and marking the equivalent resistance network as the equivalent resistance network to be tested;
S60, calculating a path from a starting point to an end point of the equivalent resistance network to be detected, and marking the path as a conductive path;
s70, taking the ratio of the number of the conductive paths to the number of all paths as an available index of the lightning arrester valve plate, wherein the aging = 1-available index of the lightning arrester valve plate;
The equivalent resistance network takes a line end of a lightning arrester valve plate as a starting point and takes a grounding end as an end point, and comprises a first number of resistance nodes, wherein the first number of resistance nodes are connected in a random interconnection mode, and each node is connected with 1-second number of other nodes; the resistance of the whole equivalent resistance network is equal to the resistance of the lightning arrester valve plate in the common state.
2. The method for evaluating the aging of the valve plate of the lightning arrester under the complex working condition according to claim 1, wherein the specific method for preprocessing the ultrasonic signal is as follows: pre-emphasis is carried out on the collected ultrasonic signals to improve the amplitude of the high-frequency component; removing noise by adopting a wavelet transformation method; designing a digital filter to realize low-pass filtering smooth signals; the extracted signal envelope reflects the signal strength variation.
3. The method for evaluating aging of a valve plate of a lightning arrester under a complex working condition according to claim 2, wherein the step of extracting the frequency domain characteristics of the preprocessed signal specifically comprises: dividing the preprocessed ultrasonic signal into a plurality of frames of short signals; and a window function is adopted for each frame of short signal, and frequency domain characteristics are obtained through fast Fourier transform.
4. The method for evaluating aging of a valve plate of a lightning arrester under a complex working condition according to claim 3, wherein the step of deleting characteristics formed by metal parts of the valve plate of the lightning arrester to be tested in the frequency domain characteristics to generate a characteristic matrix specifically comprises the following steps: obtaining or simulating a metal part signal; comparing with the difference of the measurement characteristic matrix; extracting principal difference features using principal component analysis; the method of applying the support vector machine identifies classification deletion independent features.
5. The method for evaluating the aging of the valve plate of the lightning arrester under the complex working condition according to claim 4, wherein the method for establishing and training the characteristic matrix-equivalent resistance network model is specifically comprised of:
building a training sample, acquiring a plurality of lightning arrester valve plates, obtaining characteristic matrixes of the plurality of lightning arrester valve plates, and building an equivalent matrix according to the resistance of the lightning arrester valve plates in a common state and the resistance of the lightning arrester valve plates in an overvoltage state;
establishing a model prototype, and establishing the model prototype by adopting a BP neural network;
Training the model prototype, and training the model prototype by using a training sample to obtain the feature matrix-equivalent resistance network model.
6. The method for evaluating aging of a valve plate of a lightning arrester under a complex working condition according to claim 5, wherein the step of calculating a path from a start point to an end point of the equivalent resistance network to be tested specifically comprises:
confirming that the starting point of the equivalent resistance network is a line end of a valve plate of the lightning arrester and the end point is a grounding end;
Adopting breadth-first search algorithm to start layer by layer to spread all nodes and paths traversing the network from the starting point, adding newly accessed nodes into a queue, and dequeuing the accessed nodes;
in the traversal process, the paths are traced back through the pointer, and the found reachable paths between all starting points are stored;
the number of discovered paths is counted as the number of conductive paths in the equivalent resistor network.
7. The method for evaluating the aging of the valve plate of the lightning arrester under the complex working condition according to claim 1, wherein the first number is more than 10000; the second number is greater than 64.
8. The method for evaluating the aging of the valve plate of the lightning arrester under the complex working condition according to claim 7, wherein the first quantity=1000000; the second number=1024.
9. A computer readable storage medium, wherein program instructions are stored in the computer readable storage medium, and the program instructions are used for executing the lightning arrester valve plate aging evaluation method under the complex working condition of any one of claims 1-8 when running.
10. A lightning arrester valve sheet aging evaluation system under complex operating conditions, comprising the computer readable storage medium of claim 9.
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