Detection method and device for cable connector wire diameter mismatching defect, terminal equipment and storage medium

Abstract

The invention discloses a cable joint wire diameter mismatching defect detection method and device, terminal equipment and a storage medium. The method comprises the following steps: establishing a cable temperature rise simulation model according to cable parameters and test environment parameters, and then fitting to obtain a temperature current binomial expression of a test cable at each measurement point; according to a pre-established circuit loop, obtaining the measured temperature and actual resistance of the to-be-measured cable at each measurement point, the current of the to-be-measured cable and the partial discharge amount, and calculating to obtain the calculated temperature corresponding to each measurement point; under the condition that any temperature error does not exceed a preset error threshold value, determining that the accuracy of each measured value meets the requirement; and finally, determining whether the connector wire diameter of the to-be-measured cable has a mismatching defect or not according to the measurement temperature corresponding to each measurement point and the partial discharge amount. According to the invention, whether the measured data are accurate or not can be judged, so that the error of detecting the mismatching defect of the cable connector wire diameter is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cable joint defect detection, and in particular to a method, device, terminal equipment and storage medium for detecting a cable joint wire diameter mismatch defect. Background Art

[0002] Medium-voltage cables are the backbone of urban distribution networks. They mainly adopt a three-phase turnkey structure, and the voltage level is mainly 10kV. However, during the operation of medium-voltage cables, they need to be repaired or replaced after a fault. The common practice is to cut off the damaged part and connect the new cable to the old cable through a joint. At this time, there may be slight geometric differences at the contact between the old cable and the new cable, which will lead to an increase in contact resistance and insulation defects. On the one hand, the increase in contact resistance will directly affect the passage of current, generate additional heat, and cause temperature rise at the contact. The temperature rise not only affects the transmission efficiency of the cable, but also may cause further aging of the insulation layer and even cause joint failure. On the other hand, the mismatch between the conductor cross-sections of the new and old cables will inevitably introduce insulation defects such as air gaps, which may cause partial discharge.

[0003] The wire diameter mismatch defect of the medium-voltage cable joint is located near the conductor crimping tube. The tiny mismatch is difficult to see with the naked eye, so it is necessary to conduct an on-site acceptance voltage test for detection. However, during the on-site acceptance voltage test, the current of the connected circuit loop is very small, and it is impossible to judge whether the data measured by this circuit loop is accurate, which results in errors when detecting the wire diameter mismatch defect of the cable joint. Summary of the invention

[0004] The present invention provides a method, device, terminal equipment and storage medium for detecting cable joint wire diameter mismatch defects, which can determine whether various measured data are accurate, and then reduce the error when detecting cable joint wire diameter mismatch defects.

[0005] An embodiment of the present invention provides a method for detecting a cable connector wire diameter mismatch defect, comprising:

[0006] Obtaining cable parameters and test environment parameters of the test cable; wherein the test cable is formed by connecting two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current;

[0007] Establishing a cable temperature rise simulation model according to the cable parameters and the test environment parameters;

[0008] According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are obtained by fitting; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at the preset distance to the right of the first measurement point;

[0009] According to a pre-built circuit loop for the handover withstand voltage test, the measured temperature and actual resistance of the cable to be tested at the first measuring point, the second measuring point and the third measuring point, the current of the cable to be tested, and the partial discharge amount of the cable to be tested are obtained;

[0010] According to the measured temperature, actual resistance, current and temperature-current binomial corresponding to each measuring point, the calculated temperature corresponding to each measuring point is calculated, and according to the calculated temperature and measured temperature corresponding to each measuring point, the temperature error corresponding to each measuring point is calculated;

[0011] When any temperature error does not exceed a preset error threshold, determining that the accuracy of the measured temperature, actual resistance, current, and partial discharge amount obtained based on the circuit loop meets the requirements;

[0012] According to the measured temperature corresponding to each measuring point and the partial discharge amount, it is determined whether there is a mismatch defect in the wire diameter of the connector of the cable to be tested.

[0013] Furthermore, it also includes:

[0014] When the temperature errors exceed the preset error threshold, it is determined that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop does not meet the requirements. After testing the circuit loop, the circuit loop is rebuilt.

[0015] Furthermore, establishing a cable temperature rise simulation model according to the cable parameters and the test environment parameters includes:

[0016] According to the cable parameters and the test environment parameters, establish the electric field module control equation, the solid heat transfer module control equation, the electric-thermal coupling control equation, the heat conduction control equation, the temperature value boundary, the normal heat flux density boundary, and the convection heat transfer coefficient boundary;

[0017] The cable temperature rise simulation model is obtained according to the electric field module control equation, the solid heat transfer module control equation, the electric-thermal coupling control equation, the heat conduction control equation, the temperature value boundary, the normal heat flux density boundary, and the convection heat transfer coefficient boundary;

[0018] Among them, the control equation of the electric field module is:

[0019]

[0020] J=σE+J e

[0021]

[0022] Where J represents the current density vector, Q j represents the current source, σ represents the conductivity, E represents the electric field strength vector, represents the electric potential, J e represents the external injection current density;

[0023] The control equation of the solid heat transfer module is:

[0024]

[0025] In the formula, ρ1 represents the density of the cable insulation material, C1 represents the specific heat capacity of the cable insulation material at normal pressure, T represents the cable temperature, λ represents the thermal conductivity of the cable insulation material, and Q1 represents the heat source in the cable insulation material;

[0026] The electrothermal coupling control equation is:

[0027]

[0028] In the formula, ρ represents the density of the cable insulation material, C represents the specific heat capacity of the cable insulation material at normal pressure, and Q represents the heat source in the cable insulation material;

[0029] The heat conduction control equation is:

[0030]

[0031] The temperature value boundaries are:

[0032]

[0033] The normal heat flux density boundary is:

[0034]

[0035] Where q represents the heat flux density;

[0036] The convection heat transfer coefficient boundary is:

[0037]

[0038] Where h represents the convective heat transfer coefficient and T2 represents the ambient temperature.

[0039] Furthermore, according to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature current binomial, the second temperature current binomial and the third temperature current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are fitted, including:

[0040] According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances to obtain the test temperature at each radial point of the test cable under each test current and each contact resistance;

[0041] Extracting, from the test temperatures at all points, a first test temperature corresponding to the first measurement point, a second test temperature corresponding to the second measurement point, and a third test temperature corresponding to the third measurement point;

[0042] Obtaining a first resistance of the test cable at the first measuring point, a second resistance at the second measuring point, and a third resistance at the third measuring point;

[0043] Perform binomial fitting according to the first test temperature of the first measurement point, the first cable resistance and the corresponding test current to obtain a first Joule term fitting coefficient and a first heat flow term fitting coefficient, and then obtain the first temperature-current binomial according to the first Joule term fitting coefficient and the first heat flow term fitting coefficient;

[0044] Perform binomial fitting according to the second test temperature of the second measurement point, the second cable resistance and the corresponding test current to obtain a second Joule term fitting coefficient and a second heat flow term fitting coefficient, and then obtain the second temperature-current binomial according to the second Joule term fitting coefficient and the second heat flow term fitting coefficient;

[0045] According to the third test temperature of the third measuring point, the third cable resistance and the corresponding test current, binomial fitting is performed to obtain the third joule term fitting coefficient and the third heat flow term fitting coefficient, and then the third temperature-current binomial is obtained according to the third joule term fitting coefficient and the third heat flow term fitting coefficient.

[0046] Further, the calculation of the calculated temperature corresponding to each measuring point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measuring point includes:

[0047] Calculate a first calculated temperature corresponding to the first measurement point according to a first measured temperature corresponding to the first measurement point, a first actual resistance, the current, and the first temperature-current binomial;

[0048] Calculate a second calculated temperature corresponding to the second measurement point according to a second measured temperature corresponding to the second measurement point, a second actual resistance, the current, and the second temperature-current binomial;

[0049] A third calculated temperature corresponding to the third measurement point is obtained by calculation according to the third measured temperature corresponding to the third measurement point, the third actual resistance, the current and the third temperature-current binomial.

[0050] Further, determining whether there is a mismatch defect in the connector wire diameter of the cable to be tested according to the measured temperature corresponding to each measuring point and the partial discharge amount includes:

[0051] Calculating the difference between the first measured temperature and the second measured temperature to obtain a first temperature difference, and calculating the difference between the first measured temperature and the third measured temperature to obtain a second temperature difference;

[0052] When the quotient of the first temperature difference and the second temperature difference is not within the preset temperature difference range, the second measurement temperature corresponding to the second measurement point is equal to the third measurement temperature corresponding to the third measurement point, any one of the measurement temperatures is not less than the preset temperature threshold, and the partial discharge amount is not less than the preset discharge amount threshold, it is determined that there is no mismatch defect in the connector wire diameter of the cable to be tested; otherwise, it is determined that there is a mismatch defect in the connector wire diameter of the cable to be tested.

[0053] Based on the above method embodiment, the present invention provides a corresponding device embodiment;

[0054] The present invention provides a device for detecting a cable joint wire diameter mismatch defect, comprising:

[0055] Parameter acquisition module, simulation model construction module, temperature fitting module, parameter measurement module, temperature difference calculation module, first accuracy evaluation module and defect detection module;

[0056] The parameter acquisition module is used to acquire the cable parameters of the test cable and the test environment parameters; wherein the test cable is formed by connecting two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current;

[0057] The simulation model building module is used to establish a cable temperature rise simulation model according to the cable parameters and the test environment parameters;

[0058] The temperature fitting module is used to perform temperature rise simulation on the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and to obtain the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point, respectively; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at the preset distance to the right of the first measurement point;

[0059] The parameter measurement module is used to obtain the measured temperature and actual resistance of the cable to be tested at the first measurement point, the second measurement point and the third measurement point, the current of the cable to be tested, and the partial discharge amount of the cable to be tested respectively according to the pre-built circuit loop for the handover withstand voltage test;

[0060] The temperature difference calculation module is used to calculate the calculated temperature corresponding to each measurement point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measurement point, and calculate the temperature error corresponding to each measurement point according to the calculated temperature and measured temperature corresponding to each measurement point;

[0061] The first accuracy evaluation module is used to determine that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop meets the requirements when any temperature error does not exceed a preset error threshold;

[0062] The defect detection module is used to determine whether there is a mismatch defect in the connector wire diameter of the cable to be tested according to the measured temperature corresponding to each measuring point and the partial discharge amount.

[0063] Further, it also includes: a second accuracy assessment module;

[0064] The second accuracy evaluation module is used to determine that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop does not meet the requirements when the temperature errors exceed the preset error threshold, and rebuild the circuit loop after detecting the circuit loop.

[0065] Based on the above method embodiment, the present invention provides a terminal device embodiment;

[0066] The present invention provides a terminal device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, a method for detecting a cable joint wire diameter mismatch defect as described in any embodiment of the present invention is implemented.

[0067] Based on the above method embodiment, the present invention provides a storage medium embodiment;

[0068] The present invention provides a storage medium, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, a method for detecting a cable joint wire diameter mismatch defect as described in any embodiment of the present invention is implemented.

[0069] The embodiments of the present invention have the following beneficial effects:

[0070] The present invention provides a method for detecting the wire diameter mismatch defect of a cable joint. The above method includes: obtaining the cable parameters and test environment parameters of a test cable; wherein the test cable is connected by two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current; then, according to the cable parameters and the test environment parameters, a cable temperature rise simulation model is established; then, according to the cable temperature rise simulation model, the test cable is subjected to temperature rise simulation under different test currents and different contact resistances, and the first temperature current binomial, the second temperature current binomial and the third temperature current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are fitted; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at a preset distance to the left of the first measurement point. point at the preset distance to the right of the point; then, according to the pre-built circuit loop for the handover withstand voltage test, the measured temperature and actual resistance of the cable to be tested at the first measuring point, the second measuring point and the third measuring point, the current of the cable to be tested, and the partial discharge amount of the cable to be tested are obtained; then, according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measuring point, the calculated temperature corresponding to each measuring point is calculated, and according to the calculated temperature and measured temperature corresponding to each measuring point, the temperature error corresponding to each measuring point is calculated; then, when any temperature error does not exceed the preset error threshold, it is determined that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop meets the requirements; finally, according to the measured temperature corresponding to each measuring point and the partial discharge amount, it is determined whether there is a mismatch defect in the connector wire diameter of the cable to be tested. Therefore, the present invention determines the temperature-current binomial of the cable measurement point by constructing a cable temperature rise simulation model, and then compares the measured temperature of the cable to be tested with the calculated temperature calculated by the temperature-current binomial. When the error is within the allowable range, it means that the temperature of the measurement point currently measured is slightly different from the actual temperature. Then, the mismatch defect of the connector wire diameter of the cable to be tested is detected based on each measured value, thereby reducing the error in detecting the mismatch of the connector wire diameter. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The present invention is a flowchart of a method for detecting a cable joint wire diameter mismatch defect provided by an embodiment of the present invention.

[0072] Figure 2 This is a structural cross-sectional view of a 10kv three-core cable provided by an embodiment of the present invention.

[0073] Figure 3 It is a schematic diagram of the radial temperature of the cable and the temperature at the connection point when the test current is 50A provided by an embodiment of the present invention.

[0074] Figure 4 It is a schematic diagram of the radial temperature of the cable and the temperature at the connection point when the test current is 250A provided by an embodiment of the present invention.

[0075] Figure 5 It is a schematic diagram of a circuit loop provided by an embodiment of the present invention.

[0076] Figure 6 The present invention is a schematic diagram of the structure of a device for detecting wire diameter mismatch defects in a cable joint provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0077] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] like Figure 1 As shown, a method for detecting a cable joint wire diameter mismatch defect provided by an embodiment of the present invention includes:

[0079] Step S101: obtaining cable parameters and test environment parameters of a test cable; wherein the test cable is formed by connecting two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current;

[0080] Specifically, the cable parameters include: density of cable insulation material, thermal conductivity of cable insulation material, specific heat capacity of cable insulation material, electrical conductivity of cable insulation material, thermal conductivity of cable insulation material, and resistance of each point of the cable. The test parameters include: potential, external injection current density, test current, current source, heat source in cable insulation material, and ambient temperature.

[0081] Specifically, the test cable is 70mm2 , 120mm 2 、300mm 2 The cross-section of a 10kV three-core cable. The structural cross-section of a 10kv three-core cable is as follows Figure 2 As shown, it is mainly composed of a core, optical fiber and outer layer materials; the core is mainly composed of a water-blocking conductor, an inner semi-conductive layer, and a copper shield. The core and the sheath are filled with a filling layer. The outer layer material is mainly composed of an inner sheath, steel belt armor and an outer sheath. The parameters of the various structural parts of the test cable are shown in the following table:

[0082] Parameters of each structural part of the cable

[0083]

[0084]

[0085] Specifically, two sections of 500 mm long cables are set, and the copper core cross-sections of the two sections of the cables differ by 0.1 mm. Contact resistance is used to simulate loose connection. That is, the looser the contact, the greater the resistance at the contact point and the smaller the conductivity. The value of contact resistance is expressed as a percentage of copper conductivity.

[0086] Step S102: establishing a cable temperature rise simulation model according to the cable parameters and the test environment parameters;

[0087] In a preferred embodiment, the establishing of the cable temperature rise simulation model according to the cable parameters and the test environment parameters includes:

[0088] According to the cable parameters and the test environment parameters, establish the electric field module control equation, the solid heat transfer module control equation, the electric-thermal coupling control equation, the heat conduction control equation, the temperature value boundary, the normal heat flux density boundary, and the convection heat transfer coefficient boundary;

[0089] The cable temperature rise simulation model is obtained according to the electric field module control equation, the solid heat transfer module control equation, the electric-thermal coupling control equation, the heat conduction control equation, the temperature value boundary, the normal heat flux density boundary, and the convection heat transfer coefficient boundary;

[0090] Among them, the control equation of the electric field module is:

[0091]

[0092] J=σE+J e

[0093]

[0094] Where J represents the current density vector, in A / m 3 , represents the vector differential operator, Q j Indicates the current source, the unit is A / m 3 , σ represents conductivity, unit is S / m, E represents electric field intensity vector, unit is V / m, Indicates electric potential, unit is V, J e Indicates the external injection current density, in A / m 3 ;

[0095] The control equation of the solid heat transfer module is:

[0096]

[0097] In the formula, ρ1 represents the density of the cable insulation material, C1 represents the specific heat capacity of the cable insulation material at normal pressure, T represents the cable temperature, λ represents the thermal conductivity of the cable insulation material, the unit is W / (m·K), Q1 represents the heat source in the cable insulation material, the unit is V / m 3 ;

[0098] The electrothermal coupling control equation is:

[0099]

[0100] Where ρ represents the density of the cable insulation material, in kg / m 3 , C represents the specific heat capacity of the cable insulation material at normal pressure, the unit is J / (kg·K), λ represents the thermal conductivity of the cable insulation material, the unit is W / (m·K), Q represents the heat source in the cable insulation material;

[0101] The heat conduction control equation is:

[0102]

[0103] The temperature value boundaries are:

[0104]

[0105] The normal heat flux density boundary is:

[0106]

[0107] Where q represents the heat flux density in W / m 2 ;

[0108] The convection heat transfer coefficient boundary is:

[0109]

[0110] Where h represents the convective heat transfer coefficient, and its unit is W / (m 2·K), T1 represents the cable temperature, T2 represents the ambient temperature, the unit is K.

[0111] Preferably, the cable temperature rise simulation model provides a theoretical basis for cable diameter matching judgment, and the control equations are mathematical descriptions of the physical process inside the cable, providing a theoretical basis for accurately understanding and analyzing the electromagnetic phenomena and heat transfer mechanisms of the cable during operation. Through these equations, the electrical and thermal characteristics of the cable under different working conditions can be deeply studied, laying the foundation for subsequent calculations and analysis.

[0112] In this preferred embodiment, a cable temperature rise simulation model is established through cable parameters and test environment parameters.

[0113] Step S103: According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are obtained by fitting; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at the preset distance to the right of the first measurement point;

[0114] Specifically, the first measuring point is set as point O, the second measuring point is set as point A, and the third measuring point is set as point B. The preset distance is 10 cm.

[0115] Specifically, the test current is set to 50A and 250A. Schematically, when the test current is 50A, the radial temperature of the cable and the temperature at the connection point are as follows: Figure 3 As shown, Figure 3 Figure a shows the radial temperature of the cable when the test current is 50A. Figure 3 Figure b shows the temperature at the cable connection point when the test current is 50A. Figure 3 It can be seen that when the test current is 50A, the looser the connection at the connection point, the smaller the conductivity, the greater the resistance, and the greater the temperature rise. When the test current is 250A, the radial temperature of the cable and the temperature at the connection point are as follows Figure 4 As shown, Figure 4 Figure c shows the radial temperature of the cable when the test current is 250A. Figure 4 Figure d in the figure shows the temperature at the cable connection point when the test current is 250A. Figure 4 It can be seen that when the test current is 250A, the contact resistance caused by the loose connection at the connection causes temperature rise, making the conductor temperature at the connection point higher than the conductor temperature at the cable body. The highest temperature at the connection point is 71.86℃, and the highest temperature at the body is 71.65℃.

[0116] In a preferred embodiment, according to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are fitted, including:

[0117] According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances to obtain the test temperature at each radial point of the test cable under each test current and each contact resistance;

[0118] Extracting, from the test temperatures at all points, a first test temperature corresponding to the first measurement point, a second test temperature corresponding to the second measurement point, and a third test temperature corresponding to the third measurement point;

[0119] Obtaining a first resistance of the test cable at the first measuring point, a second resistance at the second measuring point, and a third resistance at the third measuring point;

[0120] Perform binomial fitting according to the first test temperature of the first measurement point, the first cable resistance and the corresponding test current to obtain a first Joule term fitting coefficient and a first heat flow term fitting coefficient, and then obtain the first temperature-current binomial according to the first Joule term fitting coefficient and the first heat flow term fitting coefficient;

[0121] Specifically, based on binomial regression, the first temperature current binomial is obtained as:

[0122] T O =a O λI 2 R O +b O

[0123] Where, T O represents the first test temperature, a O represents the first joule fitting coefficient, I represents the test current, R O represents the first cable resistance, b O Represents the fitting coefficient of the first heat flow term.

[0124] Perform binomial fitting according to the second test temperature of the second measurement point, the second cable resistance and the corresponding test current to obtain a second Joule term fitting coefficient and a second heat flow term fitting coefficient, and then obtain the second temperature-current binomial according to the second Joule term fitting coefficient and the second heat flow term fitting coefficient;

[0125] Specifically, based on binomial regression, the second temperature current binomial is obtained as follows:

[0126] T A =a A λI 2 R A +b A

[0127] Where, T A represents the second test temperature, a A represents the fitting coefficient of the second joule term, R A represents the second cable resistance, b A Represents the fitting coefficient of the second heat flow term.

[0128] According to the third test temperature of the third measuring point, the third cable resistance and the corresponding test current, binomial fitting is performed to obtain the third joule term fitting coefficient and the third heat flow term fitting coefficient, and then the third temperature-current binomial is obtained according to the third joule term fitting coefficient and the third heat flow term fitting coefficient.

[0129] Specifically, based on binomial regression, the third temperature current binomial is obtained as follows:

[0130] T B =a B λI 2 R B +b B

[0131] Where, T B represents the third test temperature, a B represents the third joule fitting coefficient, R B represents the third cable resistance, b B Represents the fitting coefficient of the third heat flow term.

[0132] In this preferred embodiment, according to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial are fitted.

[0133] Step S104: obtaining the measured temperature and actual resistance of the cable under test at the first measuring point, the second measuring point and the third measuring point, the current of the cable under test, and the partial discharge amount of the cable under test respectively according to the pre-built circuit loop for the handover withstand voltage test;

[0134] Schematically, the above circuit loop is as follows Figure 5As shown, it mainly includes a high-voltage partial discharge circuit and a high-current circuit. There is cable insulation between the two circuits, so they will not interfere with each other. The measuring end consists of a current transformer (ammeter), an infrared thermal imager (thermometer) and a partial discharge meter. The three devices are connected to the network through wifi and synchronously sample data. The infrared thermal imager is used to measure the measurement temperature corresponding to the first measurement point, the second measurement point and the third measurement point, the current transformer is used to measure the current, and the partial discharge meter is used to measure the partial discharge amount.

[0135] Step S105: Calculate the calculated temperature corresponding to each measuring point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measuring point, and calculate the temperature error corresponding to each measuring point according to the calculated temperature and measured temperature corresponding to each measuring point;

[0136] In a preferred embodiment, the step of calculating the calculated temperature corresponding to each measuring point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measuring point includes:

[0137] Calculate a first calculated temperature corresponding to the first measurement point according to a first measured temperature corresponding to the first measurement point, a first actual resistance, the current, and the first temperature-current binomial;

[0138] Calculate a second calculated temperature corresponding to the second measurement point according to a second measured temperature corresponding to the second measurement point, a second actual resistance, the current, and the second temperature-current binomial;

[0139] A third calculated temperature corresponding to the third measurement point is obtained by calculation according to the third measured temperature corresponding to the third measurement point, the third actual resistance, the current and the third temperature-current binomial.

[0140] Specifically, in the temperature-current binomial corresponding to each measurement point, the parameter values ​​of the experimental current and the corresponding position of the cable resistance are replaced with the above current and actual resistance, and the calculated temperature corresponding to each measurement point can be calculated. Then, for each measurement point, the difference between the measured temperature and the calculated temperature is calculated to obtain the temperature error.

[0141] Step S106: when any temperature error does not exceed a preset error threshold, determining that the accuracy of the measured temperature, actual resistance, current, and partial discharge amount obtained based on the circuit loop meets the requirements;

[0142] Specifically, when at least one temperature error does not exceed the preset error threshold, it means that the error between the measured temperature obtained according to the current circuit loop and the actual temperature of the cable is not large, and the mismatch defect of the cable joint wire diameter can be detected based on the measured temperature.

[0143] In a preferred embodiment, it also includes:

[0144] When the temperature errors exceed the preset error threshold, it is determined that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop does not meet the requirements. After testing the circuit loop, the circuit loop is rebuilt.

[0145] Specifically, if all temperature errors exceed the preset error threshold, that is, the accuracy of the measured temperature, actual resistance, current and partial discharge does not meet the requirements, it indicates that there is a problem with the current circuit loop construction. Therefore, it is necessary to check whether the circuit loop construction is correct and rebuild the circuit loop.

[0146] In this preferred embodiment, when all temperature errors exceed a preset error threshold, the current circuit loop is detected and the circuit loop is rebuilt.

[0147] Step S107: determining whether there is a mismatch defect in the connector wire diameter of the cable to be tested according to the measured temperature corresponding to each measuring point and the partial discharge amount.

[0148] In a preferred embodiment, determining whether there is a mismatch defect in the connector wire diameter of the cable to be tested according to the measured temperature corresponding to each measuring point and the partial discharge amount includes:

[0149] Calculating the difference between the first measured temperature and the second measured temperature to obtain a first temperature difference, and calculating the difference between the first measured temperature and the third measured temperature to obtain a second temperature difference;

[0150] When the quotient of the first temperature difference and the second temperature difference is not within the preset temperature difference range, the second measurement temperature corresponding to the second measurement point is equal to the third measurement temperature corresponding to the third measurement point, any one of the measurement temperatures is not less than the preset temperature threshold, and the partial discharge amount is not less than the preset discharge amount threshold, it is determined that there is no mismatch defect in the connector wire diameter of the cable to be tested; otherwise, it is determined that there is a mismatch defect in the connector wire diameter of the cable to be tested.

[0151] Specifically, the quotient of the first temperature difference and the second temperature difference can be expressed by the following formula:

[0152]

[0153] Considering that the interface mismatch at the cable connector crimping does not exceed 8% (it is difficult to crimp if it exceeds 8%), the cable cross-sectional area and resistance on both sides of the crimping tube do not differ by more than 8%, and the thermal flow fitting coefficient is basically the same in the same environment. Therefore, when there is a mismatch defect, the corresponding empirical ratio criterion is:

[0154] 0.92<(T O -T A ) / (T O -T B )<1.08

[0155] Specifically, considering that the resistance at the large cross section must be smaller than the resistance at the small cross section, when there is a mismatch defect, the relative temperature criterion is as follows:

[0156] T A <T B , or T A >T B

[0157] Specifically, considering that the cable operating temperature is limited by the maximum allowable operating temperature of the insulation, when it is below the rated current carrying capacity I0 (which can be provided by the manufacturer or obtained by referring to the cable current carrying capacity table based on the cross-sectional area), the absolute temperature criterion is obtained: when the temperatures at the three measuring points are all less than 90 degrees, it indicates a mismatch defect.

[0158] Specifically, experience shows that if the cable diameters are not matched and there are no defects, the partial discharge is less than 50pC.

[0159] In this preferred embodiment, whether the connector wire diameter of the cable to be tested has a mismatch defect is determined based on the measured temperature corresponding to each measuring point and the partial discharge amount.

[0160] Based on the above method embodiment, the present invention provides a corresponding device embodiment.

[0161] like Figure 6 As shown, an embodiment of the present invention provides a device for detecting a cable joint wire diameter mismatch defect, comprising:

[0162] Parameter acquisition module, simulation model construction module, temperature fitting module, parameter measurement module, temperature difference calculation module, first accuracy evaluation module and defect detection module;

[0163] The parameter acquisition module is used to acquire the cable parameters of the test cable and the test environment parameters; wherein the test cable is formed by connecting two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current;

[0164] The simulation model building module is used to establish a cable temperature rise simulation model according to the cable parameters and the test environment parameters;

[0165] The temperature fitting module is used to perform temperature rise simulation on the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and to obtain the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point, respectively; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at the preset distance to the right of the first measurement point;

[0166] The parameter measurement module is used to obtain the measured temperature and actual resistance of the cable to be tested at the first measurement point, the second measurement point and the third measurement point, the current of the cable to be tested, and the partial discharge amount of the cable to be tested respectively according to the pre-built circuit loop for the handover withstand voltage test;

[0167] The temperature difference calculation module is used to calculate the calculated temperature corresponding to each measurement point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measurement point, and calculate the temperature error corresponding to each measurement point according to the calculated temperature and measured temperature corresponding to each measurement point;

[0168] The first accuracy evaluation module is used to determine that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop meets the requirements when any temperature error does not exceed a preset error threshold;

[0169] The defect detection module is used to determine whether there is a mismatch defect in the connector wire diameter of the cable to be tested according to the measured temperature corresponding to each measuring point and the partial discharge amount.

[0170] In a preferred embodiment, it further comprises: a second accuracy assessment module;

[0171] The second accuracy evaluation module is used to determine that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop does not meet the requirements when the temperature errors exceed the preset error threshold, and rebuild the circuit loop after detecting the circuit loop.

[0172] It should be noted that the device embodiments described above are merely schematic, wherein the modules described above as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. In addition, in the accompanying drawings of the device embodiments provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which can be specifically implemented as one or more communication buses or signal lines. Ordinary technicians in this field can understand and implement it without paying creative labor. The above schematic diagram is only an example of a detection device for a cable joint wire diameter mismatch defect, and does not constitute a limitation on a detection device for a cable joint wire diameter mismatch defect, and may include more or fewer components than shown in the figure, or a combination of certain components, or different components.

[0173] Based on the above method item embodiments, the present invention provides corresponding terminal device item embodiments.

[0174] Another embodiment of the present invention provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements a method for detecting a cable joint wire diameter mismatch defect as described in any embodiment of the present invention when executing the computer program.

[0175] Exemplarily, in this embodiment, the computer program may be divided into one or more modules, which are stored in the memory and executed by the processor to implement the present invention. The one or more module elements may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program in the device;

[0176] The terminal device may be a computing device such as a desktop computer, a notebook, a PDA, a cloud server, etc. The device may include, but is not limited to, a processor, a memory;

[0177] The processor referred to herein may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc. The above-mentioned processor is the control center of the above-mentioned device, and uses various interfaces and lines to connect various parts of the entire device;

[0178] The above-mentioned memory can be used to store the above-mentioned computer programs and / or modules. The above-mentioned processor realizes various functions of the above-mentioned device by running or executing the computer programs and / or modules stored in the above-mentioned memory, and calling the data stored in the memory. The above-mentioned memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application required for a function, etc.; in addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0179] Based on the above method item embodiments, the present invention provides a corresponding storage medium item embodiment.

[0180] Another embodiment of the present invention provides a storage medium, which includes a stored computer program, wherein when the computer program is running, the device where the storage medium is located is controlled to execute a method for detecting a cable joint wire diameter mismatch defect as described in any embodiment of the present invention.

[0181] In this embodiment, the storage medium is a computer-readable storage medium, the computer program includes computer program code, and the computer program code may be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0182] Compared with the prior art, by implementing the above-mentioned embodiments of the present invention, it is possible to determine whether the various data obtained by measurement are accurate, thereby reducing the error in detecting the wire diameter mismatch defect of the cable joint.

[0183] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for detecting a cable joint wire diameter mismatch defect, characterized in that: include: Obtaining cable parameters and test environment parameters of the test cable; wherein the test cable is formed by connecting two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current; Establishing a cable temperature rise simulation model according to the cable parameters and the test environment parameters; According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are obtained by fitting; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at the preset distance to the right of the first measurement point; According to a pre-built circuit loop for the handover withstand voltage test, the measured temperature and actual resistance of the cable to be tested at the first measuring point, the second measuring point and the third measuring point, the current of the cable to be tested, and the partial discharge amount of the cable to be tested are obtained; According to the measured temperature, actual resistance, current and temperature-current binomial corresponding to each measuring point, the calculated temperature corresponding to each measuring point is calculated, and according to the calculated temperature and measured temperature corresponding to each measuring point, the temperature error corresponding to each measuring point is calculated; When any temperature error does not exceed a preset error threshold, determining that the accuracy of the measured temperature, actual resistance, current, and partial discharge amount obtained based on the circuit loop meets the requirements; According to the measured temperature corresponding to each measuring point and the partial discharge amount, it is determined whether there is a mismatch defect in the wire diameter of the connector of the cable to be tested.

2. A method for detecting a cable joint wire diameter mismatch defect according to claim 1, characterized in that: Also includes: When the temperature errors exceed the preset error threshold, it is determined that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop does not meet the requirements. After testing the circuit loop, the circuit loop is rebuilt.

3. A method for detecting a cable joint wire diameter mismatch defect according to claim 1, characterized in that: The establishing of a cable temperature rise simulation model according to the cable parameters and the test environment parameters comprises: According to the cable parameters and the test environment parameters, establish the electric field module control equation, the solid heat transfer module control equation, the electric-thermal coupling control equation, the heat conduction control equation, the temperature value boundary, the normal heat flux density boundary, and the convection heat transfer coefficient boundary; The cable temperature rise simulation model is obtained according to the electric field module control equation, the solid heat transfer module control equation, the electric-thermal coupling control equation, the heat conduction control equation, the temperature value boundary, the normal heat flux density boundary, and the convection heat transfer coefficient boundary; Among them, the control equation of the electric field module is: J=σE+Je e Where J represents the current density vector, Q j represents the current source, σ represents the conductivity, E represents the electric field strength vector, represents the electric potential, J e represents the external injection current density; The control equation of the solid heat transfer module is: In the formula, ρ1 represents the density of the cable insulation material, C1 represents the specific heat capacity of the cable insulation material at normal pressure, T represents the cable temperature, λ represents the thermal conductivity of the cable insulation material, and Q1 represents the heat source in the cable insulation material; The electrothermal coupling control equation is: In the formula, ρ represents the density of the cable insulation material, C represents the specific heat capacity of the cable insulation material at normal pressure, and Q represents the heat source in the cable insulation material; The heat conduction control equation is: The temperature value boundaries are: The normal heat flux density boundary is: Where q represents the heat flux density; The convection heat transfer coefficient boundary is: Where h represents the convective heat transfer coefficient and T2 represents the ambient temperature.

4. A method for detecting a cable joint wire diameter mismatch defect according to claim 3, characterized in that: According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances, and the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point are obtained by fitting, including: According to the cable temperature rise simulation model, the temperature rise simulation of the test cable is performed under different test currents and different contact resistances to obtain the test temperature at each radial point of the test cable under each test current and each contact resistance; Extracting, from the test temperatures at all points, a first test temperature corresponding to the first measurement point, a second test temperature corresponding to the second measurement point, and a third test temperature corresponding to the third measurement point; Obtaining a first resistance of the test cable at the first measuring point, a second resistance at the second measuring point, and a third resistance at the third measuring point; Perform binomial fitting according to the first test temperature of the first measurement point, the first cable resistance and the corresponding test current to obtain a first Joule term fitting coefficient and a first heat flow term fitting coefficient, and then obtain the first temperature-current binomial according to the first Joule term fitting coefficient and the first heat flow term fitting coefficient; Perform binomial fitting according to the second test temperature of the second measurement point, the second cable resistance and the corresponding test current to obtain a second Joule term fitting coefficient and a second heat flow term fitting coefficient, and then obtain the second temperature-current binomial according to the second Joule term fitting coefficient and the second heat flow term fitting coefficient; According to the third test temperature of the third measuring point, the third cable resistance and the corresponding test current, binomial fitting is performed to obtain the third joule term fitting coefficient and the third heat flow term fitting coefficient, and then the third temperature-current binomial is obtained according to the third joule term fitting coefficient and the third heat flow term fitting coefficient.

5. A method for detecting a cable joint wire diameter mismatch defect according to claim 4, characterized in that: The step of calculating the calculated temperature corresponding to each measuring point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measuring point includes: Calculate a first calculated temperature corresponding to the first measurement point according to a first measured temperature corresponding to the first measurement point, a first actual resistance, the current, and the first temperature-current binomial; Calculate a second calculated temperature corresponding to the second measurement point according to a second measured temperature corresponding to the second measurement point, a second actual resistance, the current, and the second temperature-current binomial; A third calculated temperature corresponding to the third measurement point is obtained by calculation according to the third measured temperature corresponding to the third measurement point, the third actual resistance, the current and the third temperature-current binomial.

6. A method for detecting a cable joint wire diameter mismatch defect according to claim 5, characterized in that: The step of determining whether the connector wire diameter of the cable to be tested has a mismatch defect according to the measured temperature corresponding to each measuring point and the partial discharge amount includes: Calculating the difference between the first measured temperature and the second measured temperature to obtain a first temperature difference, and calculating the difference between the first measured temperature and the third measured temperature to obtain a second temperature difference; When the quotient of the first temperature difference and the second temperature difference is not within the preset temperature difference range, the second measurement temperature corresponding to the second measurement point is equal to the third measurement temperature corresponding to the third measurement point, any one of the measurement temperatures is not less than the preset temperature threshold, and the partial discharge amount is not less than the preset discharge amount threshold, it is determined that there is no mismatch defect in the connector wire diameter of the cable to be tested; otherwise, it is determined that there is a mismatch defect in the connector wire diameter of the cable to be tested.

7. A detection device for cable joint wire diameter mismatch defect, characterized in that: include: Parameter acquisition module, simulation model construction module, temperature fitting module, parameter measurement module, temperature difference calculation module, first accuracy evaluation module and defect detection module; The parameter acquisition module is used to acquire the cable parameters of the test cable and the test environment parameters; wherein the test cable is formed by connecting two cable segments of the same length but different copper core radii, and the two cable segments are connected by contact resistance; the test environment parameters include: test current; The simulation model building module is used to establish a cable temperature rise simulation model according to the cable parameters and the test environment parameters; The temperature fitting module is used to perform temperature rise simulation on the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and to obtain the first temperature-current binomial, the second temperature-current binomial and the third temperature-current binomial corresponding to the test cable at the first measurement point, the second measurement point and the third measurement point, respectively; wherein the first measurement point is the connection point of the cable segment, the second measurement point is located at a preset distance to the left of the first measurement point, and the third measurement point is located at the preset distance to the right of the first measurement point; The parameter measurement module is used to obtain the measured temperature and actual resistance of the cable to be tested at the first measurement point, the second measurement point and the third measurement point, the current of the cable to be tested, and the partial discharge amount of the cable to be tested respectively according to the pre-built circuit loop for the handover withstand voltage test; The temperature difference calculation module is used to calculate the calculated temperature corresponding to each measurement point according to the measured temperature, actual resistance, current, and temperature-current binomial corresponding to each measurement point, and calculate the temperature error corresponding to each measurement point according to the calculated temperature and measured temperature corresponding to each measurement point; The first accuracy evaluation module is used to determine that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop meets the requirements when any temperature error does not exceed a preset error threshold; The defect detection module is used to determine whether there is a mismatch defect in the connector wire diameter of the cable to be tested according to the measured temperature corresponding to each measuring point and the partial discharge amount.

8. A detection device for cable joint wire diameter mismatch defects according to claim 7, characterized in that: Also includes: A second accuracy assessment module; The second accuracy evaluation module is used to determine that the accuracy of the measured temperature, actual resistance, current and partial discharge amount obtained based on the circuit loop does not meet the requirements when the temperature errors exceed the preset error threshold, and rebuild the circuit loop after detecting the circuit loop.

9. A terminal device, characterized in that: It comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, it implements a method for detecting a cable joint wire diameter mismatch defect as described in any one of claims 1 to 6.

10. A storage medium, characterized in that: The storage medium includes a stored computer program, wherein when the computer program is executed, the device where the storage medium is located is controlled to execute a method for detecting a cable joint wire diameter mismatch defect as described in any one of claims 1 to 6.

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