CN112067052A - Oil-immersed transformer fault diagnosis method based on feature selection - Google Patents
Oil-immersed transformer fault diagnosis method based on feature selection Download PDFInfo
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Abstract
The invention discloses an oil-immersed transformer fault diagnosis method based on feature selection. Specifically, the method firstly performs double construction of statistical characteristics and ratio characteristics on the dissolved gas concentration data. Secondly, the method selects the most suitable characteristic variable for fault classification diagnosis by using a neighbor component analysis algorithm. And finally, establishing a probabilistic neural network model by using the selected characteristic variables to implement transformer fault diagnosis. The method has the advantages that: firstly, the method firstly carries out feature optimization through feature expansion, thereby greatly ensuring the precision of the classification model; secondly, the method of the invention is simple to operate and very easy to implement.
Description
Technical Field
The invention relates to a transformer fault diagnosis method, in particular to an oil-immersed transformer fault diagnosis method based on feature selection.
Background
With the increasing demand for electric power, transformers have become indispensable electrical devices in electric power transmission systems. As a key link of power supply and distribution, the operation performance of the transformer directly affects the operation of the whole power system. Any transformer fault type results in wasted power and even more serious economic losses, so fault diagnosis of transformer equipment is of great research significance to avoid potential power or other economic losses. Since transformers used in power supply and distribution systems are generally oil-immersed transformers, a common idea for performing fault diagnosis of transformers is to analyze gases (hydrogen, methane, ethane, ethylene, and acetylene) dissolved in transformer oil. The method has the defects of code defect and critical value criterion defect. In recent years, the emerging transformer fault diagnosis methods use the dissolved gas concentration data to classify the faults, so as to realize the diagnosis of the transformer faults.
Discriminant analysis and neural network are the most common mode classification techniques, and can be applied to solving the problem of transformer fault classification diagnosis. However, the classification accuracy of the neural network-based transformer fault diagnosis model is directly affected by network input parameters or variables. In other words, the input variables or parameters of the neural network directly affect the accuracy of the diagnosis. In addition, discriminant analysis is a linear classification diagnosis strategy and cannot effectively adapt to the variability and nonlinear characteristics of the concentration data of the dissolved gas of the transformer. Most importantly, these methods for classification diagnosis require as much sample data as possible for training, and fail to select the most suitable features for diagnosing faults to establish the classification diagnosis fault types.
Data-driven transformer fault diagnosis is directly dependent on dissolved gas concentration data in transformer oil, and the dissolved gas concentration data can reflect different fault types. However, from the viewpoint of the requirement of reliable and accurate transformer fault diagnosis task, it is difficult to implement the task by directly relying on the concentration data of the dissolved gas alone, and it is necessary to further mine the change characteristics of the dissolved gas concentration data on the basis of the dissolved gas concentration data and perform the fault diagnosis of the transformer by using more characteristic data. However, in the existing scientific research literature and patent materials, there are few research results related to the above, and generally, the research is to directly use the dissolved gas concentration data to perform fault classification diagnosis.
In addition, as the category characteristics of the dissolved gas concentration data in the oil-immersed transformer are limited, the three-ratio method does not directly use the dissolved gas concentration data, and uses the ratio between the dissolved gas concentrations for further classification diagnosis. Therefore, further feature expansion and selection of the dissolved gas concentration data is positively effective for fault diagnosis. It can be said that the fault diagnosis of the transformer using the dissolved gas concentration data requires a fault diagnosis method technique capable of coping with the problem of a small sample and selecting from optimal characteristics.
Disclosure of Invention
The invention aims to solve the main technical problems that: and (3) implementing feature expansion and classification feature selection by using the concentration data of the dissolved gas in the oil-immersed transformer oil, and establishing a probabilistic neural network model by using the selected features, thereby implementing transformer fault diagnosis. Specifically, the method firstly performs double construction of statistical characteristics and ratio characteristics on the dissolved gas concentration data. Secondly, the method of the invention utilizes a neighbor Analysis (NCA) algorithm to select the most suitable characteristic variable for fault classification diagnosis. And finally, establishing a probabilistic neural network model by using the selected characteristic variables to implement transformer fault diagnosis.
The technical scheme adopted by the method for solving the problems is as follows: an oil-immersed transformer fault diagnosis method based on feature selection comprises the following steps:
step (1): carrying out characteristic expansion on the dissolved gas concentration data of the oil-immersed transformer in 7 different working states so as to obtain N in a healthy working state0A feature vectorN in partial discharge fault state1A feature vectorN in spark-over fault condition2A feature vectorN in arc discharge fault condition3A feature vectorN in medium temperature overheat fault state4A feature vectorN at low temperature over-temperature fault condition5A feature vectorAnd N in a high temperature overheat fault condition6A feature vectorThe specific implementation process comprises the following steps (1.1) to (1.5).
Step (1.1): the analysis data of the dissolved gas in the transformer oil specifically comprises the following steps: concentration of hydrogenConcentration of methaneEthane concentrationEthylene concentrationAnd acetylene concentrationThe 5 concentration data can be used for constructing a concentration vector of the dissolved gasWherein k represents a sample number, and the upper label c is belonged to {0, 1, 2, 3, 4, 5, 6} to respectively indicate a healthy working state, a partial discharge fault state, a spark discharge fault state, an arc discharge fault state, a medium-temperature overheat fault state, a low-temperature overheat fault state, and a high-temperature overheat fault state.
Step (1.2): respectively calculating the mean value of each dissolved gas concentration vector according to the formula shown belowStandard deviation ofKurtosisDeflection degreeRoot mean squareCrest factorForm factorPulse factorEdge factorMaximum logarithm of
Wherein b is equal to {1, 2, 3, 4, 5}, and the sample number k is equal to {1, 2, …, N ∈ [ ]c},Representation calculationThe maximum value of the medium element.
Step (1.3): the ratio coefficient of each dissolved gas concentration vector is calculated according to the formula shown below
In the above formula, d ∈ {1, 2, …, 15 }.
Step (1.4): according toConstructing a multi-feature fusion vectorWhereinR25×1A real number vector of 25 × 1 dimensions is represented, and the upper symbol T represents a transposed symbol of a matrix or vector.
Step (1.5): and (4) repeating the steps (1.2) to (1.4) to respectively obtain the multi-feature fusion vectors of the oil-immersed transformer operating in 7 different working states.
Step (2): building a feature matrixBuilding class label vector y ═ y0,y1,…,y6]T∈RN×1(ii) a Wherein N is N0+N1+…+N6,RN×1Representing vectors, of real numbers in dimension Nx 1All elements in are equal to 0, vectorAll elements in are equal to 1, vectorAll elements in (1) are equal to 2, vectorAll of the elements inAre all equal to 3, vectorAll elements in (1) are equal to 4, vectorAll elements in (1) are equal to 5, vectorAll elements in (a) are equal to 6.
And (3): for the feature matrix X ∈ RN×25After the standardization processing is carried out, a characteristic weight vector w epsilon R is obtained by utilizing a neighbor component analysis algorithm1×25。
And (4): finding out the largest f elements from the characteristic weight vector w, recording the positions of the f elements as a position set phi, correspondingly selecting the column vectors at the same positions from the characteristic matrix X, and establishing a new characteristic matrixWherein R isN×fA matrix of real numbers representing dimensions N × f.
And (5): to be provided withAnd taking each row vector as input data, taking elements of a corresponding row in the class label vector y as output data, and establishing a probabilistic neural network model.
And (6): the new measurement obtains the concentration data of the dissolved gas in the oil-immersed transformer, specifically including 5 concentration data of hydrogen concentration, methane concentration, ethane concentration, ethylene concentration and acetylene concentration
And (7): performing feature expansion on the 5 concentration data in the step (6) to obtain a feature vector xnew∈R1 ×25The specific implementation process is the same as the steps (1.1) to (1.4), and then the feature vector x is selected from the feature vector x according to the position set recorded in the step (4)newSelecting elements at corresponding positions in the image to construct a new feature vectorWherein R is1×fRepresenting a real number vector of dimension 1 xf.
And (8): with new feature vectorsUsing the probabilistic neural network model established in the step (5) as input data to calculate and obtain an output estimation value ynewAnd based on the output estimate ynewAnd determining the current working state of the oil-immersed transformer.
By carrying out the steps described above, the advantages of the method of the invention are presented below.
Firstly, the method of the invention involves substantially no complex transformations or mathematical calculations, and is simple to operate and very easy to implement. Secondly, the method firstly carries out feature optimization through feature expansion, and greatly ensures the precision of the classification model. Finally, in the specific implementation case, the reliability and the superiority of the method are fully illustrated by the comparison of case implementation results.
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FIG. 1 is a schematic flow chart of the method of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention discloses an oil-immersed transformer fault diagnosis method based on feature selection, and the specific implementation mode of the method is described by combining an implementation flow schematic diagram shown in figure 1.
In this embodiment, the oil immersed transformer has N in a healthy working state050 dissolved gas concentration data, N in partial discharge fault state1In the spark failure state, N is present in 21 groups of data2For 16 sets of data, there is N in the arc fault condition318 groups of data, N in medium-temperature overheat fault state423 groups of data, N in low-temperature overheat fault state523 groups of data, highN in the warm overheat fault state624 sets of data. And establishing a fault diagnosis model of the transformer by using the data and carrying out online fault diagnosis, wherein the method specifically comprises the following steps.
Step (1): carrying out characteristic expansion on the dissolved gas concentration data of the oil-immersed transformer operating under 7 different working states according to the steps (1.1) to (1.5), thereby obtaining N under the healthy working state0A feature vectorN in partial discharge fault state1A feature vectorN in spark-over fault condition2A feature vectorN in arc discharge fault condition3A feature vectorN in medium temperature overheat fault state4A feature vectorN at low temperature over-temperature fault condition5A feature vectorAnd N in a high temperature overheat fault condition6A feature vector
Step (3): for the feature matrix X ∈ RN×25Obtaining a matrix after carrying out standardization processingAnd obtaining a characteristic weight vector w epsilon R by utilizing a neighbor component analysis algorithm1×25The specific implementation process is as follows:
first, the initialization gradient step α is 1, and the initialization objective function value F is set to 10(w)=-106And initializing the weight coefficient vector w ═ 1, 1, …, 1]∈R1×25。
② calculating the objective function value F (w) under the condition of the current weight coefficient vector w:
wherein the probability p of correct classificationiCan be calculated according to the formula shown below:
in the above formula, pijThe calculation formula of (a) is as follows:
wherein the content of the first and second substances,andrespectively represent matricesThe ith and jth row vectors of (1), if and only ifAndwhen belonging to the same class (i.e. the ith element is equal to the jth element in the class label vector y), yijOther cases y 1ij0; distance Dw(xi,xj) The calculation of (c) is as follows:
where i ═ 1, 2, …, N, j ═ 1, 2, …, N, the notation | | | | | denotes the length of the calculated vector, and diag (w) denotes the transformation of the vector w into a diagonal matrix.
(iii) determining whether the convergence condition | F (w) -F is satisfied0(w)|<10-6(ii) a If yes, outputting a weight coefficient vector w; if not, continuing to implement the fourth step.
Fourthly, F is arranged0Calculating a gradient value delta f after (w) f (w), and updating the weight coefficient vector according to a formula w + alpha delta f; the gradient value Δ f is calculated as follows:
fifthly, according to the above formulaCalculating an objective function value F (w), and judging whether a condition F (w) > F is met0(w)? If yes, updating the gradient step length alpha according to the formula alpha which is 1.01 alpha; if not, updating the gradient step length alpha according to the formula alpha being 0.4 alpha.
And sixthly, returning to the step III to continue the next iterative optimization until the convergence condition in the step III is met.
And (4): finding out the largest f elements from the characteristic weight vector w, recording the positions of the f elements in the w as a position set phi, correspondingly selecting the column vectors at the same positions from the characteristic matrix X, and establishing a new characteristic matrix
And (5): to be provided withAnd taking each row vector as input data, taking elements of a corresponding row in the class label vector y as output data, and establishing a probabilistic neural network model.
And (6): the new measurement obtains the concentration data of the dissolved gas in the oil-immersed transformer, and specifically comprises 5 concentration data of hydrogen concentration, methane concentration, ethane concentration, ethylene concentration and acetylene concentration.
And (7): performing feature expansion on the 5 concentration data in the step (6) to obtain a feature vector xnew∈R1 ×25The specific implementation process is the same as the steps (1.1) to (1.4), and then the position set phi recorded in the step (4) is used for determining the position from the feature vector xnewSelecting elements at corresponding positions in the image to construct a new feature vector
And (8): with new feature vectorsUsing the probabilistic neural network model established in the step (5) as input data to calculate and obtain an output estimation value ynewAnd based on the output estimate ynewAnd determining the current working state of the oil-immersed transformer.
Specifically, the molar ratio of ynewIf the voltage is equal to 0, the transformer runs in a healthy working state; if ynew1, the transformer is operated in a partial discharge fault state; if ynewWhen it is 2, it indicates a spark discharge failure state, and if ynewWhen the value is 3, the arc discharge fault state is indicated; if ynewWhen y is 4, it indicates a medium-temperature overheat fault statenew5, indicating a low-temperature overheat fault state; if ynew6 denotes high-temperature overheatingA fault condition.
Claims (1)
1. An oil-immersed transformer fault diagnosis method based on feature selection is characterized by comprising the following steps:
step (1): carrying out characteristic expansion on the dissolved gas concentration data of the oil-immersed transformer in 7 different working states so as to obtain N in a healthy working state0A feature vectorN in partial discharge fault state1A feature vectorN in spark-over fault condition2A feature vectorN in arc discharge fault condition3A feature vectorN in medium temperature overheat fault state4A feature vectorN at low temperature over-temperature fault condition5A feature vectorAnd N in a high temperature overheat fault condition6A feature vectorThe specific implementation process comprises the following steps (1.1) to (1.5);
step (1.1): the dissolved gas concentration data in the transformer oil specifically comprises: concentration of hydrogenConcentration of methaneEthane concentrationEthylene concentrationAnd acetylene concentrationThe 5 concentration data can be used for constructing a concentration vector of the dissolved gasWherein k represents a sample number, and the upper label c is belonged to {0, 1, 2, 3, 4, 5, 6} to respectively indicate a healthy working state, a partial discharge fault state, a spark discharge fault state, an arc discharge fault state, a medium-temperature overheat fault state, a low-temperature overheat fault state, and a high-temperature overheat fault state;
step (1.2): respectively calculating the mean value of each dissolved gas concentration vector according to the formula shown belowStandard deviation ofKurtosisDeflection degreeRoot mean squarePeak valueFactor(s)Form factorPulse factorEdge factorMaximum logarithm of
step (1.3): the ratio coefficient of each dissolved gas concentration vector is calculated according to the formula shown below
In the above formula, d is belonged to {1, 2, …, 15 };
step (1.4): according toConstructing feature vectorsWherein, the upper label T represents the transposition symbol of the matrix or the vector;
step (1.5): repeating the steps (1.2) to (1.4) to respectively obtain characteristic vectors of the oil-immersed transformer operating in 7 different working states;
step (2): building a feature matrixBuilding class label vector y ═ y0,y1,…,y6]T∈RN×1(ii) a Wherein N is N0+N1+…+N6,RN×1Representing vectors, of real numbers in dimension Nx 1All elements in are equal to 0, vectorAll elements in are equal to 1, vectorAll elements in (1) are equal to 2, vectorAll elements in (1) are equal to 3, vectorAll elements in (1) are equal to 4, vectorAll elements in (1) are equal to 5, vectorAll elements in (1) are equal to 6;
and (3): for the feature matrix X ∈ RN×25After the standardization processing is carried out, a characteristic weight vector w epsilon R is obtained by utilizing a neighbor component analysis algorithm1×25;
And (4): finding out the largest f elements from the characteristic weight vector w, recording the positions of the f elements in the w as a position set phi, correspondingly selecting the column vectors at the same positions from the characteristic matrix X, and establishing a new characteristic matrixWherein R isN×fA real number matrix representing dimensions N × f;
and (5): to be provided withTaking each row vector as input data, taking elements of corresponding rows in the class label vector y as output data, and establishing a probabilistic neural network model;
and (6): newly measuring to obtain concentration data of dissolved gas in the oil-immersed transformer, wherein the concentration data specifically comprises 5 concentration data of hydrogen concentration, methane concentration, ethane concentration, ethylene concentration and acetylene concentration;
and (7): performing feature expansion on the 5 concentration data in the step (6) to obtain a feature vector xnew∈R1×25The specific implementation process is the same as the steps (1.1) to (1.4), and then the position set phi recorded in the step (4) is used for determining the position from the feature vector xnewSelecting elements at corresponding positions in the image to construct a new feature vector
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