Method and system for detecting and locating early insulation faults of distribution cables

Abstract

The application discloses a distribution network cable early insulation fault detection positioning method and system, relates to the technical field of cable fault detection, and is based on insulation layer damage condition data in the cable installation stage and operation state data after the cable is put into use to perform future period operation state prediction analysis on the insulation layer in the cable use stage; whether the cable use in the future period has a problem generation risk is judged according to the future period operation state prediction analysis result of the insulation layer in the cable use stage; through fusion of the insulation layer damage condition in the cable installation stage, an initial operation state file is established for the cable, the accuracy and reliability of cable operation state analysis are improved, meanwhile, the cable is continuously divided in unit length segments, the initial damage degree and real-time operation data are fused to independently predict the future period operation state, the cable operation state is predicted in the space and time two dimensions, the power supply reliability is improved, the operation and maintenance resource distribution is optimized, and the power grid operation and maintenance cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of cable fault detection, and particularly relates to a distribution network cable early insulation fault detection positioning method and system. BACKGROUND

[0002] As a key carrier for transmitting electric energy, the integrity of the insulation layer of a power cable directly determines the safety and reliability of power grid operation. During long-term operation of the cable, the insulation performance of the cable gradually deteriorates due to multiple stresses such as electricity, heat, machinery and environment, and eventually may lead to insulation breakdown, causing power interruption and even safety accidents. Therefore, how to effectively monitor and healthily evaluate the insulation state of the cable and realize early warning of fault risks is an important problem in the field of power system operation and maintenance. At present, the monitoring and evaluation of the insulation state of the cable mainly has the following limitations:

[0003] 1. Most of the existing methods focus on online monitoring data (such as partial discharge, dielectric loss, temperature, etc.) of the cable after being put into operation, and generally ignore the initial insulation damage of the cable caused by extrusion, bending, scratching, etc. during the early stages of transportation, laying and installation. These congenital defects are the potential source and weak point of accelerated insulation deterioration during subsequent operation, and ignoring this factor will lead to incomplete basis for state evaluation and deviation of prediction results from reality.

[0004] 2. Most evaluation models are based on statistical analysis of current or historical operation state to judge the overall health condition or estimate the remaining life. They lack fine analysis of the continuous distribution characteristics of insulation damage along the length direction of the cable and cannot effectively integrate initial damage information to dynamically and continuously predict the future state of each unit length section of the cable. This makes it difficult to accurately locate the specific high-risk section for early warning and cannot provide quantitative judgment of the risk situation in the near future.

[0005] 3. The traditional state evaluation results are often macroscopic, and it is difficult for operation and maintenance personnel to intuitively and quantitatively know the risk of failure in the near future from the evaluation report, which is not conducive to the development of accurate and timely preventive maintenance strategies. In order to solve the problems in the background art, the application designs a distribution network cable early insulation fault detection positioning method and system. SUMMARY

[0006] In view of the above technical deficiencies, the application provides a distribution network cable early insulation fault detection positioning method and system.

[0007] To solve the above technical problems, the application adopts the following technical solution: the application provides a distribution network cable early insulation fault detection positioning method, which includes the following specific steps:

[0008] S1, acquire insulation layer damage data in the cable installation stage and real-time operation state data after the cable is put into use;

[0009] S2, analyze the continuous damage degree of each unit length section of the insulation layer in the cable installation stage based on the insulation layer damage data in the cable installation stage;

[0010] S3, based on the operation state data after the cable is put into use and the continuous damage degree analysis result of each unit length section of the insulation layer in the cable installation stage, perform future period operation state prediction analysis of each unit length section of the insulation layer in the cable use stage;

[0011] S4, based on the future period operation state prediction analysis result of each unit length section of the insulation layer in the cable use stage and the cable use time data, perform future period operation state prediction analysis of the insulation layer in the cable use stage;

[0012] S5, according to the future period operation state prediction analysis result of the insulation layer in the cable use stage, judge whether the future period cable use has a problem risk.

[0013] It should be noted that, as the preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, the specific steps of S1 are:

[0014] S11, acquire the insulation layer damage data in the cable installation stage by acquiring the cable insulation layer damage image, wherein the insulation layer damage data in the cable installation stage includes insulation layer damage type data, each type damage thickness data, damage point number data, each damage point damage type data and damage area data corresponding to each unit length section of the cable;

[0015] S12, acquire the operation state data after the cable is put into use through the cable joint intelligent sensor, the cable manufacturer technical specification book, the weather forecast, the real-time evaluation system of the power cable group load flow, the cable operation and maintenance record and the cable material parameter, wherein the operation state data after the cable is put into use includes real-time environmental temperature data, rated temperature data, future period environmental temperature prediction value data, load current data, cable maximum long-term working temperature data, cable use time data and cable insulation layer activation energy data after the cable is put into use;

[0016] S13, store the acquired data in a storage component for use in the analysis process.

[0017] It should be noted that, as the preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, S2 includes the following specific steps:

[0018] S21, preset the cable unit length section in the cable installation stage, obtain the insulation layer damage type data, each type damage thickness data, damage point number data, each damage point damage type data and damage area data corresponding to each unit length section of the cable;

[0019] S22, obtain the insulation layer each unit length section each damage point damage degree analysis result in the cable installation stage from the insulation layer damage type data, each type damage thickness data and damage area data corresponding to each unit length section of the cable;

[0020] S23, obtain the insulation layer each unit length section damage degree analysis result in the cable installation stage from the insulation layer each unit length section each damage point damage degree analysis result in the cable installation stage and the damage point number data corresponding to each unit length section of the cable;

[0021] S24, obtain the insulation layer each unit length section continuous damage degree analysis result in the cable installation stage from the insulation layer each unit length section damage degree analysis result in the cable installation stage.

[0022] It should be noted that, as the preferred technical solution of the distribution network cable early insulation fault detection and positioning method, the specific steps of S22 are: according to the insulation layer damage type data, each type damage thickness data, each damage point damage type data and damage area data corresponding to each unit length section of the cable, the insulation layer each unit length section each damage point damage degree analysis in the cable installation stage is carried out, wherein the insulation layer i section unit length section j damage point damage degree analysis process in the cable installation stage is: , j is the number corresponding to each damage point, j is any one of 1 to M, M is the maximum value of the number corresponding to each damage point, i is the number corresponding to each unit length section, i is any one of 1 to N, N is the maximum value of the number corresponding to each unit length section, q is the number corresponding to each damage type, q is any one of 1 to X, X is the maximum value of the number corresponding to each damage type, is the original thickness of the cable insulation layer, is the insulation layer damage thickness corresponding to the j damage point on the i unit length section, is the unit length section cable outer surface area, is the damage cable outer surface area corresponding to the j damage point on the i unit length section, is the weight corresponding to the j damage point damage type q, is the thickness damage sensitive coefficient, is the area damage nonlinear coefficient, and respectively, thickness damage weight and area damage weight; analyzing the damage condition data of each damage point in the cable installation stage, analyzing the initial health state of each damage point of the cable, laying a foundation for the analysis of the health state of each section of the cable, and improving the accuracy of the prediction of the health state of the cable.

[0023] It should be noted that, as a preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, the specific steps of S23 are: analyzing the damage degree of each unit length section of the insulation layer in the cable installation stage according to the damage degree analysis results of each damage point of each unit length section of the insulation layer in the cable installation stage and the damage point quantity data corresponding to each unit length section of the cable, wherein the damage degree analysis calculation formula of the i-th unit length section of the insulation layer in the cable installation stage is: wherein, is the damage point quantity data corresponding to the i-th unit length section of the cable, is the normalized distance of the j-th damage point of the cable from the center of the i-th unit length section, is the damage point quantity influence coefficient; although a single damage point analysis is accurate, it lacks overallness, and if there are multiple slight damages in a cable section, the cumulative effect may be more dangerous than a single serious damage, and the number of damage points in the cable section is combined to analyze the aggregation of the cable section, that is, the spatial distribution density and cumulative effect of the cable damage are analyzed.

[0024] It should be noted that, as a preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, the specific steps of S24 are: analyzing the continuous damage degree of each unit length section of the insulation layer in the cable installation stage according to the damage degree analysis results of each unit length section of the insulation layer in the cable installation stage, wherein the continuous damage degree analysis formula of each unit length section of the insulation layer in the cable installation stage is: wherein, is the damage degree analysis result corresponding to the i-1-th unit length section of the cable, is the damage degree analysis result corresponding to the i+1-th unit length section of the cable, is the spatial influence coefficient; processing the discrete unit length section damage degree analysis results into continuous damage degree analysis is a continuous spatial modeling of the health state of the cable insulation layer, which can completely retain the spatial continuity and clearly identify hidden risk features such as damage mutation points and gradient peaks that cannot be identified by traditional methods.

[0025] It should be noted that, as a preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, the specific steps of S3 are:

[0026] S31, according to the cable put into use after real-time environmental temperature data, rated temperature data, future period environmental temperature prediction value data, load current data and cable installation stage insulation layer each unit length section continuous damage degree analysis result carries out the cable use stage insulation layer each unit length section future period operation temperature prediction analysis, wherein, the cable use stage insulation layer i section unit length section t+1 period operation temperature prediction analysis formula is: Wherein, t is the corresponding number of each period after the cable is put into use, t is any one of 1 to G, G is the maximum value of the corresponding number of each period of the cable use stage insulation layer, It is the environmental temperature of the i section unit length section t period of the cable use stage insulation layer, It is the environmental temperature of the i section unit length section t+1 period of the cable use stage insulation layer, It is the i section unit length section t+1 period load current of the cable use stage insulation layer, Ie is the rated current, It is the rated temperature rise; the continuous damage degree of the cable is taken as the key input, and the prediction value of the future period load current is introduced, which improves the accuracy of the temperature rise increment caused by quantitative damage;

[0027] S32, according to the cable use stage insulation layer each unit length section future period operation temperature prediction analysis result, the cable highest long-term working temperature data and the cable insulation layer activation energy data, the cable use stage insulation layer each unit length section future period operation state prediction analysis is carried out, wherein, the calculation formula of the cable use stage insulation layer i section unit length section t+1 period operation state prediction analysis is: Wherein, It is the i section unit length section t+1 period operation temperature prediction analysis result of the cable use stage insulation layer, It is the highest long-term working temperature of the cable, Ea is the activation energy of the insulation layer, and k is the Boltzmann constant; temperature and time are converted into the consumption rate of insulation life, even if the temperature is not over standard, the small aging accumulation can also be calculated, the activation energy can accurately reflect the thermal aging characteristics of specific insulation materials, the prediction value of future period insulation state is analyzed through the future period temperature prediction value, and the dynamic evolution of the cable aging state is realized.

[0028] It should be noted that, as the preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, the specific steps of S4 are: obtaining the future period operation state prediction analysis result of each unit length section of the cable insulation layer in the use stage, integrating the future period operation state prediction analysis result of each unit length section of the cable insulation layer in the use stage on the cable used time, dividing the integral result by the cable used time, obtaining the average of the future period operation state prediction analysis result of each unit length section of the cable insulation layer in the use stage, and taking the average of the future period operation state prediction analysis result of each unit length section of the cable insulation layer in the use stage as the future period operation state prediction analysis result of the cable insulation layer in the use stage.

[0029] It should be noted that, as the preferred technical solution of the early insulation fault detection and positioning method of the distribution network cable, the specific steps of S5 are: obtaining the future period operation state prediction analysis result of the cable insulation layer in the use stage, comparing the future period operation state prediction analysis result of the cable insulation layer in the use stage with the set cable insulation layer operation state prediction analysis result threshold value, if the future period operation state prediction analysis result of the cable insulation layer in the use stage is greater than or equal to the set cable insulation layer operation state prediction analysis result threshold value, it is determined that the future period cable has a problem risk; if the future period operation state prediction analysis result of the cable insulation layer in the use stage is less than the set cable insulation layer operation state prediction analysis result threshold value, it is determined that the future period cable use state is healthy; and pushing the judgment result to relevant personnel for processing.

[0030] The early insulation fault detection and positioning system of the distribution network cable is realized based on the above-mentioned early insulation fault detection and positioning method of the distribution network cable, and specifically includes a cable insulation layer data acquisition module, a cable continuous damage degree analysis module, a cable operation state preliminary analysis module, a cable operation state prediction analysis module and a cable operation state prediction judgment module; the cable insulation layer data acquisition module is used to acquire the cable installation stage insulation layer damage data and the real-time operation state data after the cable is put into use;

[0031] The cable continuous damage degree analysis module is used to analyze the continuous damage degree of each unit length section of the cable insulation layer in the installation stage based on the cable installation stage insulation layer damage data;

[0032] The cable operation state preliminary analysis module is used to analyze the future period operation state prediction of each unit length section of the cable insulation layer in the use stage based on the operation state data after the cable is put into use and the continuous damage degree analysis result of each unit length section of the cable insulation layer in the installation stage;

[0033] The cable operation state prediction analysis module is configured to perform future period operation state prediction analysis on the insulation layer in the cable use stage based on the future period operation state prediction analysis result of each unit length section of the insulation layer in the cable use stage and the cable use time length data.

[0034] The cable operation state prediction judgment module is configured to judge whether the cable use in the future period has a problem generation risk according to the future period operation state prediction analysis result of the insulation layer in the cable use stage.

[0035] Compared with the prior art, the beneficial effects of the present application are that the present application acquires the insulation layer damage condition data in the cable installation stage and the real-time operation state data after the cable is put into use; performs continuous damage degree analysis on each unit length section of the insulation layer in the cable installation stage based on the insulation layer damage condition data in the cable installation stage; performs future period operation state prediction analysis on each unit length section of the insulation layer in the cable use stage based on the operation state data after the cable is put into use and the continuous damage degree analysis result of each unit length section of the insulation layer in the cable installation stage; performs future period operation state prediction analysis on the insulation layer in the cable use stage based on the future period operation state prediction analysis result of each unit length section of the insulation layer in the cable use stage and the cable use time length data; judges whether the cable use in the future period has a problem generation risk according to the future period operation state prediction analysis result of the insulation layer in the cable use stage; and establishes an initial operation state file for the cable by fusing the insulation layer damage condition in the cable installation stage, improves the accuracy and reliability of the cable operation state analysis, simultaneously continuously divides each unit length section of the cable, independently predicts the future period operation state by fusing the initial damage degree and the real-time operation data, makes the cable operation state prediction in the spatial and temporal dimensions, improves the power supply reliability, optimizes the operation and maintenance resource allocation, and reduces the power grid operation and maintenance cost. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a whole flowchart of the cable early insulation fault detection and positioning method of the distribution network of the present application.

[0037] Figure 2 It is a flowchart of step S2 of the cable early insulation fault detection and positioning method of the present application.

[0038] Figure 3 It is a whole framework diagram of the cable early insulation fault detection and positioning system of the present application.

[0039] Figure 4 It is a flowchart of the continuous damage degree analysis result acquisition of the cable early insulation fault detection and positioning method of the present application.

[0040] Figure 5A flowchart of a process for obtaining the prediction analysis result of the future period operation state of each unit length section of the power distribution cable early insulation fault detection and positioning method of the present application is shown. DETAILED DESCRIPTION

[0041] For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings.

[0042] To solve the technical problems presented in the background art, the present application provides a preferred embodiment:

[0043] The specific content of the present embodiment is:

[0044] As shown in Figure 1 The power distribution cable early insulation fault detection and positioning method includes the following specific steps:

[0045] S1, obtaining insulation layer damage data during the cable installation stage and real-time operation state data after the cable is put into use;

[0046] In the present embodiment, the specific steps of S1 are:

[0047] S11, the insulation layer damage data during the cable installation stage includes insulation layer damage type data, each type of damage thickness data, damage point quantity data, each damage point damage type data, and damage area data corresponding to each unit length section of the cable; the insulation layer damage type data, each type of damage thickness data, damage point quantity data, each damage point damage type data, and damage area data corresponding to each unit length section of the cable are obtained by image processing technology on the cable insulation layer damage image;

[0048] S12, the operation state data after the cable is put into use includes real-time environmental temperature data, rated temperature data, future period environmental temperature prediction value data, load current data, cable maximum long-term working temperature data, cable usage time data, and cable insulation layer activation energy data after the cable is put into use; the real-time environmental temperature data after the cable is put into use is obtained by the cable joint intelligent sensor, the rated temperature data and the maximum long-term working temperature data are obtained by the cable manufacturer's technical specification book, the future period environmental temperature prediction value data is obtained by weather forecast, the future period load current data of the cable is obtained by the power cable group load flow real-time evaluation system, the cable usage time data is obtained by the cable operation and maintenance record, and the cable insulation layer activation energy data is obtained by the cable material parameters;

[0049] S13, store the obtained data in a storage component for use in the analysis process;

[0050] S2, as Figure 2 and Figure 4As shown, the continuous damage degree of each unit length section of the insulation layer in the cable installation stage is analyzed based on the insulation layer damage condition data in the cable installation stage;

[0051] S21, presetting the unit length section of the cable in the cable installation stage, obtaining the insulation layer damage type data, the thickness data of each type of damage, the number of damage points data, the damage type data of each damage point and the damage area data corresponding to each unit length section of the cable; It should be noted that each unit length section of the cable is an equal length unit length section;

[0052] S22, obtaining the damage degree analysis result of each damage point of each unit length section of the insulation layer in the cable installation stage from the insulation layer damage type data, the thickness data of each type of damage and the damage area data corresponding to each unit length section of the cable;

[0053] In this embodiment, S22 includes the following specific steps: analyzing the damage degree of each damage point of each unit length section of the insulation layer in the cable installation stage according to the insulation layer damage type data, the thickness data of each type of damage, the damage type data of each damage point and the damage area data corresponding to each unit length section of the cable, wherein the damage degree analysis process of the jth damage point of the ith unit length section of the insulation layer in the cable installation stage is: , j is the number corresponding to each damage point, j is any one of 1 to M, M is the maximum value of the number corresponding to each damage point, i is the number corresponding to each unit length section, i is any one of 1 to N, N is the maximum value of the number corresponding to each unit length section, q is the number corresponding to each damage type, q is any one of 1 to X, X is the maximum value of the number corresponding to each damage type, is the original thickness of the cable insulation layer, is the insulation layer damage thickness corresponding to the jth damage point on the ith unit length section, is the outer surface area of the unit length section of the cable, is the damaged cable outer surface area corresponding to the jth damage point on the ith unit length section, is the weight corresponding to the qth damage type of the jth damage point, is the thickness damage sensitivity coefficient, is the area damage nonlinear coefficient, and are the thickness damage weight and the area damage weight respectively; It should be noted that the insulation layer damage types include but are not limited to scratches, indentations, cracks, penetrations and burns, etc., and the weights of which are set as follows: scratches 1.5, indentations 2.5, burns 3.0, cracks 3.5, penetrations 4.0, and the weights are multiplied because the risk degree of different damage types is different, for example, the burn is twice the scratch, which reflects the risk amplification effect; The thickness damage sensitivity coefficient is 0.7 (used to control the steepness of the influence of thickness damage on the result), Area damage non-linear coefficient is 0.3 (used to control the initial influence degree of small area damage); The greater the result indicates the more serious the thickness damage, due to the growth characteristics of the exponential, when the thickness damage is more serious, that is The greater the result indicates the more serious the thickness damage, due to the growth characteristics of the exponential, when the thickness damage is more serious, that is The value will increase sharply, Using the exponential function exp can reflect the phenomenon that the reduction of insulation thickness leads to the non-linear increase of electric field strength, at this time the risk of breakdown will rise sharply; The greater the result indicates the more serious the area damage, The setting is because the influence of area damage has a marginal diminishing effect, that is, when a small scratch appears, it destroys the integrity of the insulation layer and may become the starting point of partial discharge, at this time the risk is significantly increased, but as the damage area continues to expand, the speed of risk increase will slow down, at this time the decisive factor gradually shifts to damage depth, the exponential decay term Can represent this rule: that is, when Is very small, Is approximately linear and rapidly increasing; when Increases, the growth gradually slows down and approaches 1, Is a measure of the spatial coverage of the area damage;

[0054] S23, the damage degree analysis result of each unit length section of the insulation layer in the cable installation stage is obtained from the damage degree analysis result of each damage point of each unit length section of the insulation layer in the cable installation stage and the number of damage points corresponding to each unit length section of the cable;

[0055] In this embodiment, the specific steps of S23 are: according to the damage degree analysis result of each damage point of each unit length section of the insulation layer in the cable installation stage and the number of damage points corresponding to each unit length section of the cable, the damage degree analysis of each unit length section of the insulation layer in the cable installation stage is performed, wherein the damage degree analysis calculation formula of the i-th unit length section of the insulation layer in the cable installation stage is: Wherein, is the number of damage points corresponding to the i-th unit length section of the cable, is the normalized distance of the j-th damage point of the cable from the center of the i-th unit length section, is the damage point number influence coefficient; it should be noted that, The normalized distance of the j-th damage point of the cable from the center of the i-th unit length section is divided by the half-section length (when the damage point is located at the center of the section, that is =0, +1 is added to avoid division by zero); The value is 0.2, which is used to control the strength of the cumulative effect of multiple damage points; is the distance reciprocal ) weighted average, the formula in the numerator denominator the meaning: is the standard form of weighted average (i.e. distance weight the greater), the numerator is the weighted sum, the denominator is the weight sum; The logarithmic function is used to reflect the marginal diminishing effect (for example, the 100th damage point contributes much less to the risk than the first damage point), and the risk of multiple small damages is not simply additive. Using the logarithmic function can ensure that the risk grows faster (i.e. accumulates) when the number of damage points is small, but grows slower when the number of damage points is large, avoiding the risk of masking individual fatal damage by a large number of minor damage; Reflects the density of each damaged section.

[0056] S24, the cable installation stage insulation layer each unit length section damage degree analysis result obtained by the cable installation stage insulation layer each unit length section continuous damage degree analysis result;

[0057] In this embodiment, the specific steps of S24 are: according to the cable installation stage insulation layer each unit length section damage degree analysis result, the cable installation stage insulation layer each unit length section continuous damage degree analysis is carried out, wherein the cable installation stage insulation layer each unit length section continuous damage degree analysis formula is: , wherein, is the damage degree analysis result corresponding to the i-1 section of the cable unit length section, is the damage degree analysis result corresponding to the i+1 section of the cable unit length section, is the space influence coefficient; It should be noted that the continuous damage degree of each unit length section is analyzed because the electric field, thermal field and mechanical stress are continuously distributed on the cable, and serious damage of a section will cause distortion of the electric field and temperature distribution of the adjacent section, thereby amplifying the risk of original damage of the adjacent section, and making the originally safe damage point unsafe, The value is 0.3;

[0058] S3, based on the cable running state data after being put into use and the cable installation stage insulation layer each unit length section continuous damage degree analysis result, the cable usage stage insulation layer each unit length section future period running state prediction analysis is carried out;

[0059] As shown in Figure 5 , in this embodiment, the specific steps of S3 are:

[0060] S31, according to the real-time environmental temperature data after the cable is put into use, the rated temperature data, the future period environmental temperature prediction value data, the load current data and the continuous damage degree analysis result of each unit length section of the insulation layer in the cable installation stage, the future period operation temperature prediction analysis of each unit length section of the insulation layer in the cable use stage is carried out, wherein the future period operation temperature prediction analysis formula of the i-th unit length section of the insulation layer in the cable use stage is: Wherein, t is the number corresponding to each period after the cable is put into use, t is any one of 1 to G, G is the maximum value of the number corresponding to each period of the insulation layer in the cable use stage, is the environmental temperature of the i-th unit length section of the insulation layer in the cable use stage in t period, is the environmental temperature of the i-th unit length section of the insulation layer in the cable use stage in t+1 period, is the load current of the i-th unit length section of the insulation layer in the cable use stage in t+1 period, Ie is the rated current, is the rated temperature rise; it should be noted that all the heat of the cable is finally dissipated to the surrounding environment, so the conductor temperature must be accumulated from the ambient temperature, and the average value of the current period environmental temperature and the future period environmental temperature prediction value is used as the basic value of the future period cable working temperature, which is the first order approximation of the environmental temperature change in time step t, that is, the trapezoidal method is used instead of the rectangular method to improve the precision of the operation temperature prediction analysis process when the environmental temperature changes rapidly; in the formula Part of the average of the adjacent period environmental temperature is used, because the cable has thermal inertia, that is, the temperature cannot respond to the instantaneous jump of the current; in the formula The square is used because according to the Joule law, the conductor resistance heating power is proportional to the square of the current, and at the same time it represents the normalized load rate of the cable, which converts the load current value into a ratio relative to full load, and then multiplies the rated temperature rise (i.e. the formula Part), so that the temperature rise of the cable under this load rate is obtained; in the formula Part represents that the damaged part of the cable insulation layer under the load current generates Times of the additional Joule heat, that is, the theoretical temperature rise value determined by the load current, which exceeds the environmental temperature.

[0061] S32, according to the future period operation temperature prediction analysis result of each unit length section of the insulation layer in the cable use stage, the highest long-term working temperature data of the cable and the activation energy data of the cable insulation layer, the future period operation state prediction analysis of each unit length section of the insulation layer in the cable use stage is carried out, wherein the future period operation state prediction analysis calculation formula of the i-th unit length section of the insulation layer in the cable use stage is: Wherein, The prediction analysis result of the i-th unit length section of the insulation layer of the cable in the t+1 period of the use stage, is the maximum long-term working temperature of the cable, Ea is the activation energy of the insulation layer, and k is the Boltzmann constant; it should be noted that, represents the aging rate of the cable in the future period, and is a dimensionless multiple (i.e., when is equal to 2, it means that the aging speed of the cable at this temperature is 2 times that of the reference temperature, i.e., the life consumption is 1 time faster); the temperature is used +273 because it needs to be converted to Kelvin (because the formula is based on the Arrhenius law, and the Arrhenius law is based on thermodynamic temperature); the Boltzmann constant is 8.617*10 -5 eV / K, which is a physical constant and has a fixed value, and is used to ensure the dimension of the formula; regarding the activation energy Ea of the insulation layer: it is a characteristic of the cable resisting thermal aging, and is the sensitivity of the aging rate of the cable material to temperature, the greater the value, the more sensitive to temperature, and for XLPE insulation, its typical range is 0.7-1.2 eV, which is a material parameter; an example is given to explain the reason for using the exponential function: if Ea is 1.0 eV, is 90°C (at this time is 1), then when is 95°C, is about 1.5, i.e., the life consumption speed of the cable is accelerated by 50%, and the exponential function exp can reflect the phenomenon that a small change in the working temperature of the cable will cause a large change in its aging rate.

[0062] S4, based on the prediction analysis result of the future period running state of each unit length section of the insulation layer of the cable in the use stage and the data of the used time length of the cable, the future period running state of the insulation layer of the cable in the use stage is predicted and analyzed;

[0063] In the embodiment, the specific steps of S4 are: obtaining the future period operation state prediction analysis result of each unit length section of the cable in use stage insulation layer, integrating the future period operation state prediction analysis result of each unit length section of the cable in use stage insulation layer on the cable used time, dividing the integral result by the cable used time, obtaining the average of the future period operation state prediction analysis result of each unit length section of the cable in use stage insulation layer, taking the average of the future period operation state prediction analysis result of each unit length section of the cable in use stage insulation layer as the future period operation state prediction analysis result of the cable in use stage insulation layer. It should be noted that integrating the prediction state of each unit length section in the future period on the used time is actually to calculate the cumulative state load of each unit length section in its entire use history, and then dividing the integral result of all unit length sections by the total time to obtain the average, and finally obtaining the result which can represent the health status of the cable insulation layer in the future period. This result integrates the cumulative effect of space and time (those sections which are in poor state or have early damage for a long time have a higher weight in the overall health analysis because their integral value (cumulative state over time) is larger and can more affect the final average result).

[0064] S5, judging whether the cable use in the future period has a problem generation risk according to the future period operation state prediction analysis result of the cable in use stage insulation layer.

[0065] In the embodiment, the specific steps of S5 are: obtaining the future period operation state prediction analysis result of the cable in use stage insulation layer, comparing the future period operation state prediction analysis result of the cable in use stage insulation layer with the set threshold value of the operation state prediction analysis result of the cable in use stage insulation layer, if the future period operation state prediction analysis result of the cable in use stage insulation layer is greater than or equal to the set threshold value of the operation state prediction analysis result of the cable in use stage insulation layer, it is determined that the cable in the future period has a problem generation risk; if the future period operation state prediction analysis result of the cable in use stage insulation layer is less than the set threshold value of the operation state prediction analysis result of the cable in use stage insulation layer, it is determined that the cable use state in the future period is healthy; pushing the judgment result to the relevant personnel for processing; it should be noted that by comparing the continuous prediction analysis result with a preset and explicit threshold value, the decision is clear; the threshold value of the operation state prediction analysis result of the cable in use stage insulation layer is obtained: the operation state prediction analysis result threshold value model is established, a large number of historical normal and fault data are used to train the operation state prediction analysis result threshold value model, and the operation state prediction analysis result threshold value model learns the cable operation state health boundary from the normal sample data (but as the cable operation time increases and new data accumulates, the model should be retrained periodically (for example, every year) or triggered (for example, after line reconstruction) to update the threshold value parameters, so that they can evolve synchronously with the current actual state of the cable).

[0066] According to the above implementation, the embodiment has the following advantages over the prior art: the embodiment obtains cable installation stage insulation layer damage data and real-time operation state data after the cable is put into use; the cable installation stage insulation layer each unit length segment continuous damage degree analysis is carried out based on the cable installation stage insulation layer damage data; the cable use stage insulation layer each unit length segment future period operation state prediction analysis is carried out based on the cable use stage insulation layer each unit length segment future period operation state prediction analysis result and the cable used time length data; whether the future period cable use has a problem risk is judged according to the cable use stage insulation layer future period operation state prediction analysis result; the initial operation state file of the cable is established by fusing the insulation layer damage in the cable installation stage, the accuracy and reliability of the cable operation state analysis are improved, the cable is continuously divided into unit length segments, the initial damage degree and the real-time operation data are fused to independently predict the future period operation state, the cable operation state is predicted in the space and time two dimensions, the power supply reliability is improved, the operation and maintenance resource allocation is optimized, and the power grid operation and maintenance cost is reduced.

[0067] As shown in Figure 3 The embodiment also provides a distribution network cable early insulation fault detection and positioning system, which is based on the above-mentioned distribution network cable early insulation fault detection and positioning method, and specifically includes a cable insulation layer data acquisition module, a cable continuous damage degree analysis module, a cable operation state preliminary analysis module, a cable operation state prediction analysis module, and a cable operation state prediction judgment module; the cable insulation layer data acquisition module is used to acquire cable installation stage insulation layer damage data and real-time operation state data after the cable is put into use; the cable continuous damage degree analysis module is used to carry out cable installation stage insulation layer each unit length segment continuous damage degree analysis based on the cable installation stage insulation layer damage data; the cable operation state preliminary analysis module is used to carry out cable use stage insulation layer each unit length segment future period operation state prediction analysis based on the cable use stage insulation layer each unit length segment future period operation state prediction analysis result and the cable used time length data; the cable operation state prediction analysis module is used to carry out cable use stage insulation layer future period operation state prediction analysis based on the cable use stage insulation layer each unit length segment future period operation state prediction analysis result and the cable used time length data; the cable operation state prediction judgment module is used to judge whether the future period cable use has a problem risk according to the cable use stage insulation layer future period operation state prediction analysis result.

[0068] The specific steps of the above-mentioned various unit modules in the power distribution cable early insulation fault detection and positioning system of the present application for realizing the corresponding functions can refer to the steps in the embodiments of the power distribution cable early insulation fault detection and positioning method, which will not be described here.

[0069] The above description is merely preferred embodiments of the present application and a description of the technical principles used. Those skilled in the art should understand that the application scope involved in the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by any combinations of the above technical features or equivalent features without departing from the above application concept. For example, the technical solutions formed by mutually replacing the above features and the technical features applied in the present application (but not limited to) having similar functions.

Claims

1. A method for detecting and locating early insulation faults in distribution network cables, characterized in that, include: S1. Obtain data on insulation damage during cable installation and real-time operating status data after the cable is put into use; S2. Based on the data on insulation layer damage during the cable installation stage, analyze the degree of continuous damage to the insulation layer per unit length segment during the cable installation stage. S3. Based on the operational status data after the cable is put into use and the analysis results of the continuous damage degree of each unit length of the insulation layer during the cable installation stage, predict and analyze the future cyclical operational status of each unit length of the insulation layer during the cable service stage. S4. Based on the prediction and analysis results of the future cycle operation status of the insulation layer of the cable during the service stage and the data of the cable's service time, predict and analyze the future cycle operation status of the insulation layer of the cable during the service stage. S5. Based on the prediction and analysis results of the future cycle operation status of the insulation layer during the cable's service stage, determine whether there are risks of problems arising during the cable's future service cycle.

2. The method for detecting and locating early insulation faults in distribution network cables as described in claim 1, characterized in that, S2 includes the following specific steps: S21. During the cable installation phase, preset the unit length segments of the cable and obtain the insulation layer damage type data, damage thickness data, damage point quantity data, damage type data and damage area data corresponding to each unit length segment of the cable. S22. The damage level analysis results of each damage point of the insulation layer per unit length segment during the cable installation stage are obtained from the data of insulation layer damage type, damage thickness and damage area corresponding to each unit length segment of the cable. S23. The damage degree analysis results of each unit length segment of the insulation layer during the cable installation stage are obtained from the damage degree analysis results of each damage point of each unit length segment of the insulation layer during the cable installation stage and the data of the number of damage points corresponding to each unit length segment of the cable. S24. The analysis results of the continuous damage degree of the insulation layer per unit length segment during the cable installation stage are obtained from the analysis results of the damage degree of the insulation layer per unit length segment during the cable installation stage.

3. The method for detecting and locating early insulation faults in distribution network cables as described in claim 2, characterized in that, The specific steps of S22 are as follows: Based on the insulation layer damage type data, damage thickness data, damage type data, and damage area data corresponding to each unit length segment of the cable, analyze the damage degree of each damage point in each unit length segment of the insulation layer during the cable installation stage. Specifically, the damage degree analysis process for the j-th damage point in the i-th unit length segment of the insulation layer during the cable installation stage is as follows: Let j be the number corresponding to each damage point, where j can be any one of 1 to M, and M is the maximum number corresponding to each damage point. Let i be the number corresponding to each unit length segment, where i can be any one of 1 to N, and N is the maximum number corresponding to each unit length segment. Let q be the number corresponding to each damage type, where q can be any one of 1 to X, and X is the maximum number corresponding to each damage type. This refers to the original thickness of the cable insulation layer. Let be the insulation layer damage thickness corresponding to the j-th damage point on the i-th unit length segment. The outer surface area of ​​the cable per unit length. Let J be the damaged cable outer surface area corresponding to the j-th damage point on the i-th unit length segment. The weight corresponding to the damage type q at the j-th damage point. The thickness damage sensitivity coefficient, The area damage nonlinearity coefficient is... and These are the thickness damage weight and the area damage weight, respectively.

4. The method for detecting and locating early insulation faults in distribution network cables as described in claim 3, characterized in that, The specific steps of S23 are as follows: Based on the damage degree analysis results of each damage point in each unit length segment of the insulation layer during the cable installation stage and the data on the number of damage points corresponding to each unit length segment of the cable, the damage degree analysis of each unit length segment of the insulation layer during the cable installation stage is performed. The calculation formula for the damage degree analysis of the i-th unit length segment of the insulation layer during the cable installation stage is: ,in, This represents the number of damage points per unit length of the i-th segment of the cable. Let be the normalized distance from the j-th damage point of the cable to the center of the i-th unit length segment. This is the influence coefficient of the number of damage points.

5. The method for detecting and locating early insulation faults in distribution network cables as described in claim 4, characterized in that, The specific steps of S24 are as follows: Based on the damage analysis results of each unit length segment of the insulation layer during the cable installation stage, perform a continuous damage analysis of each unit length segment of the insulation layer during the cable installation stage. The formula for this analysis is: ,in, This is the analysis result of the damage degree per unit length of the (i-1)th segment of the cable. This is the analysis result of the damage degree per unit length of the (i+1)th segment of the cable. This represents the spatial influence coefficient.

6. The method for detecting and locating early insulation faults in distribution network cables as described in claim 5, characterized in that, The specific steps of S3 are as follows: S31. Based on the real-time ambient temperature data, rated temperature data, predicted ambient temperature data for future cycles, load current data, and the analysis results of continuous damage to the insulation layer per unit length segment during the cable installation stage, a prediction analysis of the future cycle operating temperature of the insulation layer per unit length segment during the cable's service stage is performed. The formula for predicting the operating temperature of the i-th unit length segment of the insulation layer during cycle t+1 during the cable's service stage is as follows: Where t is the number corresponding to each cycle after the cable is put into use, t is any term from 1 to G, and G is the maximum number corresponding to each cycle of the cable insulation layer during the cable's service stage. The ambient temperature per unit length segment t of the insulation layer during the cable's service life is given. The ambient temperature per unit length of the i-th segment of the cable insulation layer during the cable's service life, in cycle t+1. Ie represents the load current per unit length segment of the insulation layer during the cable's service life, spanning cycle t+1, where Ie is the rated current. This is the rated temperature rise; S32. Based on the predicted operating temperature of each unit length segment of the cable insulation layer during its service life, the maximum long-term operating temperature data of the cable, and the activation energy data of the cable insulation layer, a predicted operating state analysis of each unit length segment of the cable insulation layer during its service life is performed. The calculation formula for the predicted operating state analysis of the i-th unit length segment of the cable insulation layer during cycle t+1 is as follows: ,in, This is the result of the predicted temperature analysis for the i-th unit length segment of the cable insulation layer during the t+1 cycle of operation. is the maximum long-term operating temperature of the cable, Ea is the activation energy of the insulation layer, and k is the Boltzmann constant.

7. The method for detecting and locating early insulation faults in distribution network cables as described in claim 6, characterized in that, The specific steps of S4 are as follows: obtain the prediction and analysis results of the future cycle operation status of each unit length segment of the insulation layer during the cable's service stage; integrate the prediction and analysis results of the future cycle operation status of each unit length segment of the insulation layer during the cable's service stage over the cable's service time; divide the integration result by the cable's service time to obtain the mean value of the prediction and analysis results of the future cycle operation status of each unit length segment of the insulation layer during the cable's service stage; and use the mean value of the prediction and analysis results of the future cycle operation status of each unit length segment of the insulation layer during the cable's service stage as the prediction and analysis result of the future cycle operation status of the insulation layer during the cable's service stage.

8. The method for detecting and locating early insulation faults in distribution network cables as described in claim 7, characterized in that, The specific steps of S5 are as follows: obtain the prediction and analysis results of the future cycle operation status of the cable insulation layer during the cable's service stage; compare the prediction and analysis results of the future cycle operation status of the cable insulation layer during the cable's service stage with the set threshold for the prediction and analysis results of the cable insulation layer during the cable's service stage; if the prediction and analysis results of the future cycle operation status of the cable insulation layer during the cable's service stage are greater than or equal to the set threshold for the prediction and analysis results of the cable insulation layer during the cable's service stage, it is determined that the cable has a risk of problems arising in the future cycle; if the prediction and analysis results of the future cycle operation status of the cable insulation layer during the cable's service stage are less than the set threshold for the prediction and analysis results of the cable insulation layer during the cable's service stage, it is determined that the cable's service status is healthy in the future cycle. The judgment result will be sent to the relevant personnel for processing.

9. A system for detecting and locating early insulation faults in distribution network cables, implemented based on the method for detecting and locating early insulation faults in distribution network cables according to any one of claims 1-8, characterized in that, Specifically, it includes a cable insulation layer data acquisition module, a cable continuous damage degree analysis module, a cable operation status preliminary analysis module, a cable operation status prediction analysis module, and a cable operation status prediction and judgment module; the cable insulation layer data acquisition module is used to acquire data on insulation layer damage during cable installation and real-time operation status data after the cable is put into use; The cable continuous damage analysis module is used to analyze the continuous damage degree of the insulation layer per unit length segment during the cable installation stage based on the data on insulation layer damage during the cable installation stage. The cable operation status preliminary analysis module is used to predict and analyze the future cycle operation status of each unit length of the insulation layer during the cable service stage based on the operation status data after the cable is put into use and the analysis results of the continuous damage degree of each unit length segment of the insulation layer during the cable installation stage. The cable operation status prediction and analysis module is used to predict and analyze the future cycle operation status of the cable insulation layer based on the prediction and analysis results of the future cycle operation status of each unit length segment of the cable insulation layer during the cable service stage and the cable service duration data. The cable operation status prediction and judgment module is used to determine whether there are risks of problems arising in the future use of the cable based on the prediction and analysis results of the future cycle operation status of the insulation layer during the cable's service stage.

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