CN114528721A - Cable intermediate joint insulation state assessment method and system - Google Patents
Cable intermediate joint insulation state assessment method and system Download PDFInfo
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Abstract
The application discloses a method and a system for evaluating the insulation state of a cable intermediate joint, wherein the method comprises the following steps: firstly, obtaining evaluation characteristic quantities representing the insulation state of a cable intermediate joint, and carrying out standardization processing on the evaluation characteristic quantities; secondly, determining the subjective weight of each index by adopting an improved analytic hierarchy process, determining the objective weight of each index by adopting an improved entropy method, combining the subjective weight and the objective weight by applying a comprehensive weighting method to obtain a constant weight, introducing a variable weight function to carry out weight correction on the constant weight, and taking corresponding measures to make up for the defect of poor weight correction effect of the variable weight function on the condition of serious distortion of multiple indexes; and finally, evaluating the insulation state of the cable intermediate joint by adopting an improved good-bad solution distance method to obtain the insulation deterioration condition of each intermediate joint and the comparison condition of the insulation deterioration degree of each joint. Therefore, the technical problems that the evaluation accuracy is poor and the insulation degradation conditions of a plurality of middle joints cannot be compared are solved.
Description
Technical Field
The application relates to the technical field of electric power, in particular to a cable intermediate joint insulation state assessment method and system.
Background
The cable accessories become the biggest weak link of the cable line, and the cable intermediate joint has the characteristics of large quantity and complex operation environment compared with the terminal joint and becomes the high-frequency zone of the cable accessory fault, so that the monitoring and evaluation of the insulation state of the cable intermediate joint are the important factors for solving the problem of the cable fault.
At present, the insulation state of the cable intermediate joint is evaluated mainly by the following methods; 1) the method is a non-electrical measurement method for monitoring the state quantity of the cable intermediate connector by selecting an ultrasonic signal, cannot accurately and quantitatively analyze the relation between the state quantity and the insulation state, and needs to improve the accuracy. 2) According to the change of the state quantity of the evaluation index of the cable joint, the weight change idea is adopted to correct each index weight, the actual operation condition of the cable joint is met, but when two or more indexes are seriously deviated, the assignment of each evaluation index weight cannot be well realized, and even the evaluation result is inconsistent with the actual operation state. 3) Five characteristic quantities such as electric field strength value are adopted to represent the insulation state of the joint, and the application level isThe weight of each index is determined by an analysis method, and the insulation state of the cable joint is evaluated by applying a fuzzy evaluation method, so that the basic thought is reasonable, certain practical application possibility exists, but the existing problems are obvious, namely, the weight of each index obtained by utilizing an analytic hierarchy process has strong subjective randomness, misjudgment is easily caused, and the error is large. 4) The objective weight of each index is calculated through an entropy method, the correlation of each evaluation characteristic quantity of each cable terminal joint of each switch cabinet is calculated for subjective weight determination, weighting is integrated to obtain a new weight combining subjective and objective factors, and the insulation state of the joint is evaluated by a fuzzy comprehensive evaluation method, although the rationality is strong. But in calculating the entropy of the index informationE j When the index weight approaches 1, although the size difference of the information entropy values is very slight, the entropy weight obtained by calculation has a ready multiple difference; and moreover, the insulation state of a single joint can only be evaluated, and the insulation states of all joints cannot be compared, so that the establishment of the maintenance work of a cable system by subsequent workers is not facilitated.
Disclosure of Invention
The application provides a cable intermediate joint insulation state assessment method and system, which are used for solving the technical problems that in the prior art, assessment accuracy is poor and insulation degradation conditions of a plurality of intermediate joints cannot be compared.
In view of the above, a first aspect of the present application provides a method for evaluating an insulation state of a cable intermediate joint, the method including:
taking the relative temperature rise of the surface temperature and the environment temperature of the intermediate joint and the partial discharge signal of the intermediate joint as evaluation characteristic quantities, and carrying out standardization processing on the evaluation characteristic quantities to obtain relative degradation values of the evaluation characteristic quantities;
when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold value, each evaluation characteristic quantity is used as an evaluation index of the intermediate joint, a geometric mean hyper-transport theory is adopted to improve the analytic hierarchy process, and the subjective weight of the evaluation index is determined through the improved analytic hierarchy process;
improving an entropy method through a preset correction formula group, and determining objective weight of the evaluation index through the improved entropy method;
comprehensively weighting the subjective weight and the objective weight to obtain a combined weight, taking the combined weight as a constant weight, and introducing a variable weight function to correct the constant weight to obtain a variable weight;
and taking the intermediate joint with extremely good insulation state as a positive reference point, taking the intermediate joint with extremely serious insulation aging as a negative reference point to improve the good-bad solution distance method, and analyzing the insulation state of the intermediate joint based on the improved good-bad solution distance method and the variable weight.
Optionally, the normalizing each evaluation feature value to obtain the relative degradation value of each evaluation feature value specifically includes:
respectively inputting each evaluation characteristic quantity into a standardization processing formula to obtain a relative degradation value of each evaluation characteristic quantity, wherein the standardization processing formula is as follows:
in the formula (I), the compound is shown in the specification,
、
respectively, a lower threshold and an upper threshold for evaluating the characteristic quantity, the values of which are often determined according to a preventive test protocol or a handover test protocol.
Optionally, when the relative degradation value of each evaluation feature does not exceed the preset threshold, the evaluation feature is used as an evaluation index of the intermediate joint, the analytic hierarchy process is improved by using a geometric mean hyper-transport theory, and the subjective weight of the evaluation index is determined by the improved analytic hierarchy process, which specifically includes:
when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold value, taking each evaluation characteristic quantity as an evaluation index of the intermediate joint;
constructing an original judgment matrix and a complementary matrix of the original judgment matrix;
constructing a first column vector of a hyper-transfer approximation matrix according to the complementary matrix, and taking the first column vector as a weight vector of the evaluation index;
and carrying out normalization processing on the first column of column vectors to obtain the subjective weight of the evaluation index.
Optionally, the modifying an entropy method by a preset modification formula group, and determining the objective weight of the evaluation index by the modified entropy method specifically include:
calculating an index value of each evaluation index of the intermediate joint, correcting a probability calculation formula, inputting the index value into the corrected probability calculation formula to obtain the ratio of each index value to the sum of the index values, and calculating an information entropy value of the evaluation index according to the ratio;
inputting the information entropy value into an improved entropy weight calculation formula to obtain the objective weight of the evaluation index, wherein the improved entropy weight calculation formula specifically comprises:
in the formula (I), the compound is shown in the specification,
in order to be the objective weight,
for the information entropy of the j-th index,
is the information entropy value of the k-th index,
the information entropy value of the indicator is the I < th > item.
Optionally, the weight-varying function specifically includes:
and performing weight adjustment on the constant weight through a variable weight formula, wherein the variable weight formula specifically comprises:
in the formula (I), the compound is shown in the specification,
is as followsiThe deterioration value of each of the evaluation indexes,
is as followsiThe constant weight of each evaluation index,
is a firstiThe weight of each evaluation index is changed according to the weight,nis the number of the evaluation indexes,
are variable weight coefficients.
Optionally, the improving the good-bad solution distance method by using the intermediate joint with the extremely good insulation state as a positive reference point and the intermediate joint with the extremely severe insulation aging as a negative reference point, and analyzing the insulation state of the intermediate joint based on the improved good-bad solution distance method and the variable weight, specifically includes:
taking the middle joint with extremely good insulation state as a positive reference point, taking the middle joint with extremely serious insulation aging as a negative reference point, and constructing a decision matrix;
after the decision matrix is subjected to standardization processing, weighting processing is carried out to obtain a weighting matrix, and a positive ideal solution and a negative ideal solution are determined based on the weighting matrix;
and calculating Euclidean distances from the intermediate joint to the positive ideal solution and the negative ideal solution, calculating the closeness of the intermediate joint according to the Euclidean distances, and analyzing the closeness of each intermediate joint to obtain the quality of the insulation state of each intermediate joint and the grade of the insulation state of a single intermediate joint.
A second aspect of the present application provides a cable intermediate joint insulation state evaluation system, the system including:
the acquisition module is used for taking the relative temperature rise of the surface temperature of the intermediate joint and the ambient temperature and the partial discharge signal of the intermediate joint as evaluation characteristic quantities and carrying out standardization processing on the evaluation characteristic quantities to obtain relative degradation values of the evaluation characteristic quantities;
the first calculation module is used for taking each evaluation characteristic quantity as an evaluation index of the intermediate joint when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold, improving the analytic hierarchy process by adopting a geometric mean hyper-transfer theory, and determining the subjective weight of the evaluation index through the improved analytic hierarchy process;
the second calculation module is used for improving an entropy method through a preset correction formula group and determining the objective weight of the evaluation index through the improved entropy method;
the third calculation module is used for comprehensively weighting the subjective weight and the objective weight to obtain a combined weight, using the combined weight as a constant weight, and introducing a variable weight function to correct the constant weight to obtain a variable weight;
and the analysis module is used for improving the good-bad solution distance method by taking the intermediate joint with extremely good insulation state as a positive reference point and the intermediate joint with extremely serious insulation aging as a negative reference point, and analyzing the insulation state of the intermediate joint based on the improved good-bad solution distance method and the variable weight.
Optionally, the acquisition module is specifically configured to:
taking the relative temperature rise of the surface temperature of the intermediate joint and the ambient temperature and the partial discharge signal of the intermediate joint as evaluation characteristic quantities;
respectively inputting each evaluation characteristic quantity into a standardization processing formula to obtain a relative degradation value of each evaluation characteristic quantity, wherein the standardization processing formula is as follows:
in the formula (I), the compound is shown in the specification,
、
respectively, a lower threshold and an upper threshold for evaluating the characteristic quantity, the values of which are often determined according to a preventive test protocol or a handover test protocol.
Optionally, the second calculating module is specifically configured to:
calculating an index value of each evaluation index of the intermediate joint, correcting a probability calculation formula, inputting the index value into the corrected probability calculation formula to obtain the ratio of each index value to the sum of the index values, and calculating an information entropy value of the evaluation index according to the ratio;
inputting the information entropy value into an improved entropy weight calculation formula to obtain the objective weight of the evaluation index, wherein the improved entropy weight calculation formula specifically comprises:
in the formula (I), the compound is shown in the specification,
in order to be the objective weight,
for the information entropy of the j-th index,
for the information entropy value of the k-th index,
the information entropy value of the indicator is the I < th > item.
Optionally, the analysis module is specifically configured to:
taking the middle joint with extremely good insulation state as a positive reference point, taking the middle joint with extremely serious insulation aging as a negative reference point, and constructing a decision matrix;
after the decision matrix is subjected to standardization processing, weighting processing is carried out to obtain a weighting matrix, and a positive ideal solution and a negative ideal solution are determined based on the weighting matrix;
and calculating Euclidean distances from the intermediate joint to the positive ideal solution and the negative ideal solution, calculating the closeness of the intermediate joint according to the Euclidean distances, and analyzing the closeness of each intermediate joint to obtain the quality of the insulation state of each intermediate joint and the grade of the insulation state of a single intermediate joint.
According to the technical scheme, the method has the following advantages:
the application provides a cable intermediate joint insulation state evaluation method, which comprises the steps of firstly obtaining evaluation characteristic quantities representing the insulation state of a cable intermediate joint, and carrying out standardization processing on the evaluation characteristic quantities; secondly, determining subjective weight of each index by adopting an improved analytic hierarchy process, determining objective weight of each index by adopting an improved entropy method, and combining the subjective weight and the objective weight by applying a comprehensive weighting method to obtain new weight, wherein the weight is constant weight; comprehensively considering the condition that the insulation state of the cable intermediate joint is greatly influenced when the small weight index of the cable intermediate joint is seriously deviated from a normal value, introducing a variable weight function to carry out weight correction on the normal weight, and because the weight correction function of the traditional variable weight theory on the condition of serious distortion of a plurality of indexes is very small, corresponding measures are taken to make up the defect; and finally, evaluating the insulation state of the cable intermediate joint by adopting an improved good-bad solution distance method to obtain the insulation deterioration condition of each intermediate joint and the comparison condition of the insulation deterioration degree of each joint.
Compared with the prior art:
1) the method and the device obtain real-time data of the insulation state evaluation value of the cable intermediate joint through an online monitoring technology, and the real operation condition of the intermediate joint can be truly reflected by evaluating the data.
2) Aiming at the defects of the traditional analytic hierarchy process, the geometric mean hyper-transport theory is adopted for improvement, the improved analytic hierarchy process does not need to be subjected to consistency check, the original opinions of experts can be kept, meanwhile, the implemented steps greatly simplify the calculated amount, and the calculation steps are simple and convenient.
3) Aiming at the defects of the traditional entropy method, correction is carried out in a probability calculation formula, so that the situation that the entropy calculation is meaningless is avoided; the traditional entropy weight calculation formula is corrected, and the situation that the entropy value changes slightly when the entropy value tends to 1, but the entropy weight changes by multiples is avoided.
4) Aiming at the defects of a single weighting method, a comprehensive weighting method is adopted in the aspect of weight determination, and the advantages of subjective weight and objective weight are integrated, so that the evaluation object can be reasonably evaluated.
5) Aiming at the defects of the traditional variable weight theory, the evaluation result is directly output to be serious if the degradation degree of any index is more than 0.8; if the deterioration degree of any index is not more than 0.8, variable weight correction and judgment matrix can be carried out to obtain other results, thereby making up the deficiency of the variable weight formula and improving the precision of the evaluation result.
6) The improved good and bad solution distance method is applied to the middle joint insulation state evaluation, the insulation state grade of a single joint can be output, the insulation degradation conditions of a plurality of joints can be compared, and operation and maintenance work is facilitated.
Drawings
Fig. 1 is a schematic flowchart of an embodiment of a method for evaluating an insulation state of a cable intermediate joint provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of an embodiment of an insulation state evaluation system for a cable intermediate joint provided in an embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, an insulation state evaluation method for a cable intermediate joint provided in an embodiment of the present application includes:
it should be noted that, the determining and normalizing process evaluation feature quantity specifically includes the following steps:
(1) data acquisition and data processing of cable intermediate joint
Determining the number of evaluation objects, namely the number of intermediate joints in an evaluation range according to actual conditions on site, wherein the number is m; in the aspect of selecting the evaluation characteristic quantity, in order to make the evaluation result conform to the actual operation condition of the joint, the embodiment performs online monitoring on the cable intermediate joint in the operation state, acquires real-time data for evaluation, and simultaneously considers the difficulty degree of acquiring data by different online monitoring technologies in engineering practice and the requirement of performing nondestructive detection on the operated cable intermediate joint, so that the embodiment selects to detect local discharge signals, relative temperature rise signals of the surface temperature of the intermediate joint and the environmental temperature, and performs data acquisition and processing on the signals. The method comprises the following specific steps:
1) acquisition and processing of relative temperature rise signals of surface of intermediate joint
The reason for selecting the relative temperature rise of the surface temperature of the intermediate joint and the ambient temperature as the characteristic quantity is that the temperature data is easy to monitor, the insulation of the intermediate joint is not damaged in the detection process, and the joint temperature rises when the intermediate joint breaks down, so that the insulation aging condition of the cable joint can be known and the working state of the cable joint can be accurately evaluated by measuring and monitoring the temperature of the power cable joint. In the embodiment, multipoint distribution temperature measurement is performed in a point-type temperature measurement mode so as to obtain the characteristic quantities of the surface temperature and the environment temperature of the joint, the adopted sensor is a DS18B20 digital sensor, A/D conversion is not needed, and a digital signal is directly output. For cable intermediate joints, along the diameter at the center of the surface of the intermediate jointArranging a sensor at intervals of 120 degrees in the direction, taking the value of the sensor as processing data, and recording the data as the processing dataT 1. An additional sensor detects the ambient temperature, notedT 2. The temperature difference between the two is the input data and is recorded asT 0. The formula of the relative temperature rise is as follows:
the unit in the formula is ℃.
2) Acquisition and processing of partial discharge signals
The reason for selecting partial discharge as the characteristic quantity is that the partial discharge is closely related to the insulation condition of the joint, and numerous studies show that: most faults of the middle joint are electrical breakdown faults caused by electrical branches, and the generation and development of the electrical branches are accompanied by partial discharge phenomena, so that the measurement and analysis of joint partial discharge parameters are the most intuitive and effective method for judging the change of the joint insulation state.
In this embodiment, a high-frequency current sensor is used to obtain a partial discharge signal, and the partial discharge signal is subjected to filtering, denoising, attenuation amplification, a/D conversion, feature extraction, and other steps to obtain a partial discharge feature set, where the selected feature value is a partial discharge amountQmAverage amount of dischargeQavNumber of partial dischargesnLocal discharge energy maximumWm. Amount of partial dischargeQmThe value of (A) is the maximum value of the local discharge values of all the partial discharge signals in the detection period, and the value can visually reflect the severity of insulation damage of the joint due to the fact that insulation of the joint is usually accompanied by the local discharge phenomenon of large local discharge; average amount of dischargeQavIs the arithmetic mean value of the partial discharge quantities of all the partial discharge signals detected in the detection period, and the calculation formula is shown as (1). The value can be used as a reference for the overall intensity of the partial discharge signal; number of dischargesnThe number of all partial discharge signals in a detection period is detected, and when the insulation of the joint is degraded, the higher the degradation degree is, the higher the partial discharge frequency is correspondingly; maximum of partial discharge energyWmIs the local discharge energy value of all partial discharge signals in the detection periodWiOf whereinWiIs the first in the detection periodiThe energy of the sub-discharge pulse is calculated by the formula (2), and since the breakdown of the insulation by the partial discharge is necessarily accompanied by the exchange of energy, the discharge energy is closely related to the insulation breakdown, and generally, the more the insulation deterioration is, the larger the discharge energy is. The detection period of the embodiment is a power frequency period, namely, the characteristic quantity in the power frequency period is subjected to statistical analysis.
In the above formula, the first and second groups of the formula,nit indicates the number of times of discharge,q i is shown asiThe apparent amount of discharge detected by the sub-discharge,u i indicating the initial discharge voltage of the i-th discharge.
(2) The respective feature quantities are normalized by introducing the relative deterioration degree.
The degradation degree of the characteristic quantity refers to a degradation degree compared with the actual operation state and the fault state of the current equipment, and the value range is [0,1 ]. Different degradation degree values represent that the equipment is in different running states, and the corresponding relation between the value range of the degradation degree of the intermediate joint and the running states is shown in table 1.
TABLE 1 degradation degree and State correspondence
The indexes selected in this embodiment are smaller and more optimal indexes, and are normalized by formula (4).
In the formula，
、
Respectively, a lower threshold and an upper threshold for evaluating the characteristic quantity, the values of which are often determined according to a preventive test protocol or a handover test protocol. The value range is shown in table 2 (single cycle, within one power frequency period).
TABLE 2 evaluation of upper and lower thresholds of feature quantity
it should be noted that, after the normalization processing, the relative degradation value of each evaluation index is obtained, and if the degradation degree of any index is greater than 0.8, the evaluation result is directly output as "serious"; if the deterioration degree of any of the indices is not more than 0.8, the following variable weight correction step may be performed.
(3) The improvement of the analytic hierarchy process needs to be illustrated as follows:
the traditional analytic hierarchy process has larger subjectivity, and experts may have larger difference in judgment of the same index due to the influence of various factors, so that consistency check is required. However, the original judgment matrix often does not have good consistency, and the consistency check can be passed only by continuous adjustment, and the adjusted judgment result does not necessarily accord with the opinion of the original decision maker. Aiming at the defects of the analytic hierarchy process, the embodiment adopts a geometric mean hyper-transport theory for improvement, the improved analytic hierarchy process not only retains the original opinions of experts, but also does not need consistency check, and the analytic hierarchy process has the advantages of simplicity, convenience and small calculation amount. Because the hyper-transport approximation matrix is a complete consistency matrix, consistency check is not needed, and a weight vector taking any column in the matrix as an index can be calculated without calculating all elements in the matrix, so that the calculation amount is greatly reduced (only the first column of the hyper-transport approximation matrix is calculated in the embodiment). The specific steps for improving the analytic hierarchy process are as follows:
1) constructing a judgment matrix by adopting 1-9 scales
The elements of the A matrix are
. The scale is shown in Table 3.
TABLE 3 Scale of meanings
Constructing complementary matrices
The first column of column vectors.
Constructing a complementary matrix according to the original judgment matrix A
Is the first column vector of
，nIs the matrix order, i.e. the index number.
The formula of (c) is as follows:
in the formula (I), the compound is shown in the specification,
represents the element of the nth column of the kth row in the original judgment matrix A.
3) Constructing a hyper-transport approximation matrix
First column vector of
According to complementary matrices
Constructing a hyper-transport approximation matrix
First column vector of:
wherein
The calculation formula (6) is shown.
4) Based on hyper-transport approximation matrix
Is normalized.
Hypertransfer approximation matrix
The first column vector of the consistency can be used as the weight vector of the index, and the index weight can be obtained by normalizing the column vectorw i The normalization formula is shown in (7).
The subjective weight of each index can be calculated through the above steps 1) to 4).
103, improving an entropy method through a preset correction formula group, and determining objective weight of an evaluation index through the improved entropy method;
(4) improved entropy method for determining objective weight of each index
Two problems often exist in the traditional entropy method, one is that in an entropy calculation formula, a logarithm operation is provided as a formula (8), and when the logarithm operation is performed, the entropy calculation formula is adoptedp ij Equal to zero, i.e.
The equation is meaningless when equal to zero; secondly, when the index entropy approaches to 1, the small difference between the entropy values will cause the change of the corresponding entropy weight by times. In view of the above problems, the present embodiment improves accordingly, and determines the objective weight of each index by applying the improved entropy method. The method comprises the following specific steps:
1) raw data normalization
The indexes adopted in the present embodiment are all the more optimal indexes, and are processed by equation (8).
In the formulamThe number of the evaluation objects is shown,nthe number of the evaluation indexes is shown,X ij is shown asiA connectorjNumerical value of each index.
2) And correcting the probability calculation formula and calculating.
Computingp ij I.e. calculate the i The object to be evaluated j The index value is the first of all the evaluated objects jIn order to make the logarithm operation meaningful in the entropy calculation, the proportion of the total index value is modified non-zero, that is, the index is translated, and the specific modification formula is as follows:
the smaller the unit of index translation is, the smaller the change of entropy value is, and the translation unit in the embodiment is
The entropy error caused by the method is extremely small, and the method can meet the actual requirements of engineering.
3) Calculate the firstjInformation entropy of item index
The formula of entropy value is as follows:
4) calculating the weight of each index
If a conventional entropy weight calculation formula is adopted, when the index entropy value approaches 1, a small difference between the entropy values will cause a change of the corresponding entropy weights by multiples. Therefore, in the present embodiment, the following correction formula is used to calculate the index weight, as shown in formula (11).
The objective weight of each evaluation index can be obtained by the above steps 1) to 4).
104, comprehensively weighting the subjective weight and the objective weight to obtain a combined weight, taking the combined weight as a constant weight, and introducing a variable weight function to correct the constant weight to obtain a variable weight;
it should be noted thatThe insulation state of the intermediate joint is evaluated by using a single subjective weight or objective weight, the result is sometimes too unilateral, and in order to fully integrate the influence of the subjective weight and the objective weight on the evaluation, the embodiment adopts an integrated weighting method to combine the advantages of the subjective weight and the objective weight to obtain a combined weight
The formula is as follows:
further, in the embodiment, for the case that extreme degradation of the small weight index seriously affects the overall evaluation result, the weight change theory is introduced to perform weight adjustment on the obtained constant weight. The weight-varying formula is shown in formula (13).
In the formula (I), the compound is shown in the specification,
is as followsiThe deterioration value of each of the evaluation indexes,
is as followsiThe constant weight of each evaluation index,
is as followsiThe weight of each evaluation index is changed according to the weight,nis the number of the evaluation indexes,
are variable weight coefficients. General will, when the balance of each factor is not considered much, get
Greater than 1/2; when severe defects of some factors cannot be tolerated, take
< 1/2; when in use
If =1, the operation is equivalent to the constant-weight mode.
The specific value is obtained according to national standard or expert experience.
The weight-variable formula usually obtains good weight correction effect only when one index is seriously deviated, and the weight-variable effect is very poor when two or more index state quantities are seriously distorted, and in order to make up for the defect, analysis is carried out by combining the relative degradation degree of the step (2): if the deterioration degree of any index is more than 0.8, directly outputting the 'serious' evaluation result; and if the deterioration degree of any index is not more than 0.8, performing variable weight correction.
And 105, taking the intermediate joint with extremely good insulation state as a positive reference point, taking the intermediate joint with extremely serious insulation aging as a negative reference point, improving the good-bad solution distance method, and analyzing the insulation state of the intermediate joint based on the improved good-bad solution distance method and the variable weight.
It should be noted that, in the conventional good and bad solution distance method, the euclidean distances between each evaluation object and the positive and negative ideal solutions are respectively calculated, so as to determine the closeness between each evaluation object and the positive ideal solution, and the closeness is divided into various state intervals, so as to finally determine the good and bad properties of each evaluation object. This method has the following problems: the positive ideal solution and the negative ideal solution are extracted from the evaluation objects, only the relative insulation quality relation between the evaluation objects can be compared through the closeness, the specific insulation state cannot be given, and once the evaluation objects are all in the state with serious insulation degradation, the evaluation result can obtain the condition of relatively good insulation and is not in line with the actual condition.
In view of the above problems, the present embodiment improves the good-bad solution distance method, and uses the improved good-bad solution distance method to realize the insulation state evaluation of the intermediate joint, and the specific steps are as follows:
1) constructing a decision matrix from the evaluation objects
This embodiment hasmAn object to be evaluated is evaluated,nthe evaluation index is shown in equation (8). Two evaluation objects are introduced to serve as a positive reference point and a negative reference point respectively, the middle joint with a good insulation state serves as the positive reference point, and the middle joint with severe insulation aging serves as the negative reference point. Namely havem+2 of the number of the evaluation subjects,nthe index, the decision matrix formed is:
in the formula (I), the compound is shown in the specification,X ij is the firstiThe first to evaluate the objectjThe measured values of the item indices.
2) Standardizing decision matrix
Different evaluation indexes have different dimensions, the decision matrix needs to be standardized, and the smaller the overall selection is, the better the indexes are, and therefore the formula (8) is applied to process data. The normalized decision matrix after processing is:
3) forming a weighted normalization matrix
Considering the different influence degrees of each index, the step (6) obtains the variable weight
Combining with the Y decision matrix in the step 2) to obtain a weighting matrix:
wherein:
the specific formula is as follows:
4) determining a positive ideal solution:
negative ideal solution:
for negative correlation evaluation indices (smaller values are better for insulation) there are:
in the embodiment, the middle joint with a very good insulation state is selected as a positive reference point, and the middle joint with a very serious insulation aging is selected as a negative reference point, so that the weighted standardization indexes of the positive reference point and the negative reference point are respectively a positive ideal solution and a negative ideal solution.
5) And (3) calculating Euclidean distances from each evaluation object to positive and negative ideal solutions:
distance between evaluation scheme of each evaluation object and ideal solution
The formula is as follows:
distance between evaluation scheme of each evaluation object and negative ideal solution
The formula is as follows:
6) calculating closeness of each evaluation object
：
The proximity formula is as follows:
the larger the closeness is, the closer the insulation state of the evaluation object is to a positive ideal solution (positive reference point), namely, the better the insulation state is; the smaller the closeness, the closer the insulation state of the evaluation object is to the negative ideal solution (negative reference point), i.e., the more the insulation aging is severe. The quality comparison of the insulation state of each intermediate joint can be realized through the comparison of the proximity degree, the insulation state of a single intermediate joint can be determined after the positive and negative reference points are introduced, and table 4 represents the relationship between the pasting degree and the insulation state of the intermediate joint.
TABLE 4 relationship between paste progress and insulation state of intermediate joint
In summary, the embodiments of steps 101 to 105 can evaluate the insulation state of the cable intermediate connector.
According to the method for evaluating the insulation state of the cable intermediate joint, 1) an improved analytic hierarchy process based on a geometric mean excess transfer distance theory is applied, errors caused by consistency inspection are avoided, expert opinions are kept, calculation is simple and fast, and subjective weight of evaluation indexes can be better determined. 2) On the basis of a traditional entropy method, a probability calculation formula and an entropy weight calculation formula are corrected, the situation that the entropy weight is multiplied when the entropy method cannot be applied and the entropy value tends to change towards 1 due to extreme values is avoided, and the objective weight of the evaluation index is determined by applying an improved entropy method. 3) And (3) introducing a degradation degree to judge the defects of the traditional variable weight function, if any index degradation degree exceeds a set threshold, directly outputting a 'serious' evaluation result, and if all index degradation degrees are below the set threshold, performing variable weight correction. Therefore, the defect that the variable weight function is ineffective when two or more indexes are seriously distorted is overcome. 4) Aiming at the defect that the traditional good-poor solution distance method can only compare the relative insulation good-poor relation between evaluation objects and cannot determine the specific insulation state, the intermediate joint with extremely good insulation and extremely serious insulation aging is introduced as a positive reference point and a negative reference point for improvement, and the comparison of the insulation degradation conditions between joints and the specific insulation state grade of a single joint are determined by the steps of constructing a weighted standardized matrix, determining a positive ideal solution and a negative ideal solution, calculating Euclidean distance, calculating closeness and the like.
The foregoing is an embodiment of a method for evaluating an insulation state of a cable intermediate joint provided in the embodiment of the present application, and the following is an embodiment of a system for evaluating an insulation state of a cable intermediate joint provided in the embodiment of the present application.
Referring to fig. 2, an insulation state evaluation system for a cable intermediate joint provided in an embodiment of the present application includes:
the acquisition module 201 is configured to normalize each evaluation characteristic quantity to obtain a relative degradation value of each evaluation characteristic quantity, by using a relative temperature rise between a surface temperature of the intermediate joint and an ambient temperature and a partial discharge signal of the intermediate joint as the evaluation characteristic quantity;
the first calculation module 202 is configured to, when the relative degradation value of each evaluation feature does not exceed a preset threshold, use each evaluation feature as an evaluation index of the intermediate joint, improve the analytic hierarchy process by using a geometric mean hyper-transport theory, and determine a subjective weight of the evaluation index by the improved analytic hierarchy process;
the second calculation module 203 is configured to improve the entropy method by using a preset correction formula group, and determine the objective weight of the evaluation index by using the improved entropy method;
a third calculating module 204, configured to perform comprehensive weighting on the subjective weight and the objective weight to obtain a combined weight, use the combined weight as a constant weight, and introduce a variable weight function to correct the constant weight to obtain a variable weight;
and the analysis module 205 is configured to use the intermediate joint with the extremely good insulation state as a positive reference point, use the intermediate joint with the extremely severe insulation aging as a negative reference point, and improve the good-bad solution distance method, and analyze the insulation state of the intermediate joint based on the improved good-bad solution distance method in combination with the variable weight.
It can be clearly understood by those skilled in the art that, for convenience and simplicity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The terms "first," "second," "third," "fourth," and the like in the description of the present application and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that in the present application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a portable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A cable intermediate joint insulation state evaluation method is characterized by comprising the following steps:
taking the relative temperature rise of the surface temperature and the environment temperature of the intermediate joint and the partial discharge signal of the intermediate joint as evaluation characteristic quantities, and carrying out standardization processing on the evaluation characteristic quantities to obtain relative degradation values of the evaluation characteristic quantities;
when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold value, each evaluation characteristic quantity is used as an evaluation index of the intermediate joint, a geometric mean hyper-transport theory is adopted to improve the analytic hierarchy process, and the subjective weight of the evaluation index is determined through the improved analytic hierarchy process;
improving an entropy method through a preset correction formula group, and determining the objective weight of the evaluation index through the improved entropy method;
comprehensively weighting the subjective weight and the objective weight to obtain a combined weight, taking the combined weight as a constant weight, and introducing a variable weight function to correct the constant weight to obtain a variable weight;
and taking the intermediate joint with extremely good insulation state as a positive reference point, taking the intermediate joint with extremely serious insulation aging as a negative reference point to improve the good-bad solution distance method, and analyzing the insulation state of the intermediate joint based on the improved good-bad solution distance method and the variable weight.
2. The method for evaluating the insulation state of the cable intermediate joint according to claim 1, wherein the step of normalizing each evaluation characteristic quantity to obtain a relative degradation value of each evaluation characteristic quantity specifically comprises:
respectively inputting each evaluation characteristic quantity into a standardization processing formula to obtain a relative degradation value of each evaluation characteristic quantity, wherein the standardization processing formula is as follows:
in the formula (I), the compound is shown in the specification,
、
respectively, a lower threshold and an upper threshold for evaluating the characteristic quantity, the values of which are often determined according to a preventive test protocol or a handover test protocol.
3. The method for evaluating the insulation state of the cable intermediate joint according to claim 1, wherein when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold, each evaluation characteristic quantity is used as an evaluation index of the intermediate joint, a geometric mean hyper-transport theory is adopted to improve a hierarchy analysis method, and the subjective weight of the evaluation index is determined by the improved hierarchy analysis method, and specifically comprises the following steps:
when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold value, taking each evaluation characteristic quantity as an evaluation index of the intermediate joint;
constructing an original judgment matrix and a complementary matrix of the original judgment matrix;
constructing a first column vector of a hyper-transfer approximation matrix according to the complementary matrix, and taking the first column vector as a weight vector of the evaluation index;
and carrying out normalization processing on the first column of column vectors to obtain the subjective weight of the evaluation index.
4. The method for evaluating the insulation state of the cable intermediate joint according to claim 1, wherein an entropy method is improved by a preset correction formula set, and the objective weight of the evaluation index is determined by the improved entropy method, and specifically comprises the following steps:
calculating an index value of each evaluation index of the intermediate joint, correcting a probability calculation formula, inputting the index value into the corrected probability calculation formula to obtain the ratio of each index value to the sum of the index values, and calculating an information entropy value of the evaluation index according to the ratio;
inputting the information entropy value into an improved entropy weight calculation formula to obtain the objective weight of the evaluation index, wherein the improved entropy weight calculation formula specifically comprises:
in the formula (I), the compound is shown in the specification,
in order to be the objective weight,
for the information entropy of the j-th index,
for the information entropy value of the k-th index,
the information entropy value of the indicator is the I < th > item.
5. The method for evaluating the insulation state of the cable intermediate joint according to claim 1, wherein the weight-varying function is specifically:
in the formula (I), the compound is shown in the specification,
is as followsiThe deterioration value of each of the evaluation indexes,
is as followsiThe constant weight of each evaluation index,
is as followsiThe weight of each evaluation index is changed according to the weight,nis the number of evaluation indexes, and α is a variable weight coefficient.
6. The method for evaluating the insulation state of an intermediate joint of a cable according to claim 1, wherein the step of improving the good-bad solution distance method by using the intermediate joint with the excellent insulation state as a positive reference point and the intermediate joint with the severe insulation aging as a negative reference point, and the step of analyzing the insulation state of the intermediate joint based on the improved good-bad solution distance method and the variable weight weights specifically comprises the steps of:
taking the middle joint with extremely good insulation state as a positive reference point, taking the middle joint with extremely serious insulation aging as a negative reference point, and constructing a decision matrix;
after the decision matrix is subjected to standardization processing, weighting processing is carried out to obtain a weighting matrix, and a positive ideal solution and a negative ideal solution are determined based on the weighting matrix;
and calculating Euclidean distances from the intermediate joint to the positive ideal solution and the negative ideal solution, calculating the closeness of the intermediate joint according to the Euclidean distances, and analyzing the closeness of each intermediate joint to obtain the quality of the insulation state of each intermediate joint and the grade of the insulation state of a single intermediate joint.
7. A cable intermediate joint insulation state evaluation system, comprising:
the acquisition module is used for taking the relative temperature rise of the surface temperature of the intermediate joint and the ambient temperature and the partial discharge signal of the intermediate joint as evaluation characteristic quantities and carrying out standardization processing on the evaluation characteristic quantities to obtain relative degradation values of the evaluation characteristic quantities;
the first calculation module is used for taking each evaluation characteristic quantity as an evaluation index of the intermediate joint when the relative degradation value of each evaluation characteristic quantity does not exceed a preset threshold, improving the analytic hierarchy process by adopting a geometric mean hyper-transfer theory, and determining the subjective weight of the evaluation index through the improved analytic hierarchy process;
the second calculation module is used for improving an entropy method through a preset correction formula group and determining the objective weight of the evaluation index through the improved entropy method;
the third calculation module is used for comprehensively weighting the subjective weight and the objective weight to obtain a combined weight, using the combined weight as a constant weight, and introducing a variable weight function to correct the constant weight to obtain a variable weight;
and the analysis module is used for improving the good and bad solution distance method by taking the intermediate joint with extremely good insulation state as a positive reference point and the intermediate joint with extremely serious insulation aging as a negative reference point, and analyzing the insulation state of the intermediate joint based on the improved good and bad solution distance method and the variable weight.
8. The cable intermediate joint insulation state evaluation system of claim 7, wherein the acquisition module is specifically configured to:
taking the relative temperature rise of the surface temperature of the intermediate joint and the ambient temperature and the partial discharge signal of the intermediate joint as evaluation characteristic quantities;
and respectively inputting the evaluation characteristic quantities into a standardization processing formula to obtain the relative degradation values of the evaluation characteristic quantities, wherein the standardization processing formula is as follows:
in the formula (I), the compound is shown in the specification,
、
respectively, a lower threshold and an upper threshold for evaluating the characteristic quantity, the values of which are often determined according to a preventive test protocol or a handover test protocol.
9. The system for evaluating an insulation state of an intermediate joint of a cable according to claim 7, wherein the second calculation module is specifically configured to:
calculating an index value of each evaluation index of the intermediate joint, correcting a probability calculation formula, inputting the index value into the corrected probability calculation formula to obtain the ratio of each index value to the sum of the index values, and calculating an information entropy value of the evaluation index according to the ratio;
inputting the information entropy value into an improved entropy weight calculation formula to obtain the objective weight of the evaluation index, wherein the improved entropy weight calculation formula specifically comprises:
in the formula (I), the compound is shown in the specification,
in order to be the objective weight,
for the information entropy of the j-th index,
for the information entropy value of the k-th index,
the information entropy value of the indicator is the I < th > item.
10. The cable intermediate joint insulation state evaluation system of claim 7, wherein the analysis module is specifically configured to:
taking the middle joint with extremely good insulation state as a positive reference point, taking the middle joint with extremely serious insulation aging as a negative reference point, and constructing a decision matrix;
after the decision matrix is subjected to standardization processing, weighting processing is carried out to obtain a weighting matrix, and a positive ideal solution and a negative ideal solution are determined based on the weighting matrix;
and calculating Euclidean distances from the intermediate joint to the positive ideal solution and the negative ideal solution, calculating the closeness of the intermediate joint according to the Euclidean distances, and analyzing the closeness of each intermediate joint to obtain the quality of the insulation state of each intermediate joint and the grade of the insulation state of a single intermediate joint.
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