A method and device for detecting a cable joint mismatch defect, a terminal device, and a storage medium

Abstract

The application discloses a kind of cable joint line diameter mismatch defect detection method, device, terminal equipment and storage medium.The above-mentioned method includes: according to cable parameter and test environment parameter, establish cable temperature rise simulation model, then binomial of temperature current of test cable at each measuring point is obtained by fitting;According to the circuit loop that is built in advance, obtain the measured temperature and actual resistance of the cable to be measured at each measuring point, the current of the cable to be measured, and the partial discharge amount, the calculation temperature corresponding to each measuring point is calculated;In the case where any one temperature error does not exceed the preset error threshold, the accuracy of each measurement value is determined to meet the requirements;Finally, according to the measured temperature corresponding to each measuring point and the partial discharge amount, determine whether the joint line diameter of the cable to be measured has mismatch defect.Through the implementation of the present application, it can be judged whether the measured data is accurate, and then the error when detecting the mismatch defect of the cable joint line diameter is reduced.

Description

Technical Field

[0001] This invention relates to the field of cable joint defect detection technology, and in particular to a method, apparatus, terminal equipment and storage medium for detecting cable joint diameter mismatch defects. Background Technology

[0002] Medium-voltage cables form the backbone of urban power distribution networks, primarily employing a three-phase integrated structure with a voltage level mainly of 10kV. However, during operation, medium-voltage cables require repair or replacement after a fault. A common practice is to cut the damaged section and connect the new cable to the old one using a joint. At this point, slight geometric differences may exist at the contact point between the old and new cables, leading to increased contact resistance and insulation defects. Firstly, the increased contact resistance directly affects current flow, generating additional heat and causing a temperature rise at the contact point. This temperature rise not only affects the cable's transmission efficiency but may also cause further aging of the insulation layer, even leading to joint failure. Secondly, the mismatch in conductor cross-sections between the old and new cables inevitably introduces insulation defects such as air gaps, potentially triggering partial discharge.

[0003] The wire diameter mismatch defect of medium-voltage cable joints is located near the conductor crimping pipe. The tiny mismatch is difficult to see with the naked eye, so it needs to be detected by on-site acceptance withstand voltage test. However, the current in the circuit loop connected during the on-site acceptance withstand voltage test is very small, and it is not possible to accurately judge whether the data measured through this circuit loop is accurate. As a result, there will be errors when detecting the wire diameter mismatch defect of cable joints. Summary of the Invention

[0004] This invention provides a method, apparatus, terminal equipment, and storage medium for detecting cable joint diameter mismatch defects, which can determine whether the measured data are accurate, thereby reducing the error when detecting cable joint diameter mismatch defects.

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

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

[0007] Based on the cable parameters and the test environment parameters, a cable temperature rise simulation model is established;

[0008] Based on the cable temperature rise simulation model, the temperature rise of the test cable is simulated under different test currents and different contact resistances. The first temperature-current binomial, the second temperature-current binomial, and the third temperature-current binomial are fitted to the test cable at the first measurement point, the second measurement point, and the third measurement point, respectively. 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] Based on the pre-built circuit loop for the handover withstand voltage test, the measured temperature and actual resistance of the cable under test at the first measurement point, the second measurement point and the third measurement point are obtained, as well as the current of the cable under test and the partial discharge of the cable under test.

[0010] Based on the measured temperature, actual resistance, current, and temperature-current binomial formula corresponding to each measurement point, the calculated temperature corresponding to each measurement point is obtained. Based on the calculated temperature and measured temperature corresponding to each measurement point, the temperature error corresponding to each measurement point is calculated.

[0011] If any temperature error does not exceed a preset error threshold, the accuracy of the measured temperature, actual resistance, current and partial discharge obtained based on the circuit loop is determined to meet the requirements.

[0012] Based on the measured temperature and partial discharge quantity at each measurement point, determine whether there is a mismatch defect in the connector diameter of the cable under test.

[0013] Furthermore, it also includes:

[0014] If the temperature error exceeds the preset error threshold, and it is determined that the accuracy of the measured temperature, actual resistance, current and partial discharge obtained based on the circuit loop does not meet the requirements, the circuit loop is tested and then rebuilt.

[0015] Furthermore, the step of establishing a cable temperature rise simulation model based on the cable parameters and the test environment parameters includes:

[0016] Based on the cable parameters and the test environment parameters, the control equations for the electric field module, the solid heat transfer module, the electrothermal coupling, the heat conduction, the temperature boundary, the normal heat flux density boundary, and the convective heat transfer coefficient boundary are established.

[0017] Based on the control equations of the electric field module, the solid heat transfer module, the electrothermal coupling control equation, the heat conduction control equation, the temperature boundary, the normal heat flux density boundary, and the convective heat transfer coefficient boundary, the cable temperature rise simulation model is obtained.

[0018] The control equation for the electric field module is as follows:

[0019]

[0020] J = σE + J e

[0021]

[0022] In the formula, J represents the current density vector, and Q j Let σ represent the current source, σ represent the conductivity, and E represent the electric field intensity vector. J represents electric potential. e Indicates the externally injected current density;

[0023] The control equation for 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 under 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 as follows:

[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 under 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 boundary is:

[0032]

[0033] The normal heat flux density boundary is:

[0034]

[0035] In the formula, q represents the heat flux density;

[0036] The boundary of the convective heat transfer coefficient is:

[0037]

[0038] In the formula, h represents the convective heat transfer coefficient, and T2 represents the ambient temperature.

[0039] Furthermore, based on 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 equation, the second temperature-current binomial equation, and the third temperature-current binomial equation corresponding to the test cable at the first measurement point, the second measurement point, and the third measurement point are fitted, including:

[0040] Based on the cable temperature rise simulation model, the temperature rise simulation of the test cable is carried out 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] From the test temperatures at all points, the first test temperature corresponding to the first measurement point, the second test temperature corresponding to the second measurement point, and the third test temperature corresponding to the third measurement point are extracted.

[0042] Obtain the first resistance of the test cable at the first measurement point, the second resistance at the second measurement point, and the third resistance at the third measurement point;

[0043] Based on the first test temperature, the first cable resistance and the corresponding test current at the first measurement point, a binomial fit is performed to obtain the first Joule term fitting coefficient and the first heat flow term fitting coefficient. Then, based on the first Joule term fitting coefficient and the first heat flow term fitting coefficient, the first temperature-current binomial is obtained.

[0044] Based on the second test temperature, the second cable resistance, and the corresponding test current at the second measurement point, a binomial fit is performed to obtain the second Joule term fitting coefficient and the second heat flow term fitting coefficient. Then, based on the second Joule term fitting coefficient and the second heat flow term fitting coefficient, the second temperature-current binomial is obtained.

[0045] Based on the third test temperature, the third cable resistance, and the corresponding test current at the third measurement point, a binomial fit is performed to obtain the fitting coefficient of the third Joule term and the fitting coefficient of the third heat flow term. Then, based on the fitting coefficient of the third Joule term and the fitting coefficient of the third heat flow term, the third temperature-current binomial is obtained.

[0046] Furthermore, the step of calculating the calculated temperature corresponding to each measurement point based on the measured temperature, actual resistance, current, and the temperature-current binomial formula for each measurement point includes:

[0047] Based on the first measured temperature, the first actual resistance, the current, and the first temperature-current binomial formula corresponding to the first measurement point, the first calculated temperature corresponding to the first measurement point is calculated.

[0048] The second calculated temperature corresponding to the second measurement point is obtained by calculating the second measured temperature, the second actual resistance, the current, and the second temperature-current binomial formula based on the second measured temperature, the second measured temperature, and the second measured temperature.

[0049] The third calculated temperature corresponding to the third measurement point is obtained based on the third measured temperature, the third actual resistance, the current, and the third temperature-current binomial formula corresponding to the third measurement point.

[0050] Furthermore, determining whether there is a mismatch defect in the connector wire diameter of the cable under test based on the measured temperature and partial discharge quantity at each measurement point includes:

[0051] Calculate the difference between the first measured temperature and the second measured temperature to obtain the first temperature difference; calculate the difference between the first measured temperature and the third measured temperature to obtain the second temperature difference.

[0052] If 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 a preset temperature threshold, and the partial discharge amount is not less than a preset discharge amount threshold, then it is determined that the connector wire diameter of the cable under test has no mismatch defect; otherwise, it is determined that the connector wire diameter of the cable under test has a mismatch defect.

[0053] Based on the above method embodiments, the present invention provides corresponding apparatus embodiments;

[0054] This invention provides a device for detecting cable joint diameter mismatch defects, comprising:

[0055] The module includes a parameter acquisition module, a simulation model construction module, a temperature fitting module, a parameter measurement module, a temperature difference calculation module, a first accuracy evaluation module, and a defect detection module.

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

[0057] The simulation model construction module is used to establish a cable temperature rise simulation model based on the cable parameters and the test environment parameters.

[0058] The temperature fitting module is used to simulate the temperature rise of the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and to fit the first temperature-current binomial, the second temperature-current binomial, and the third temperature-current binomial corresponding to 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 under test at the first measurement point, the second measurement point and the third measurement point, the current of the cable under test and the partial discharge of the cable under test, 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 of each measurement point based on the measured temperature, actual resistance, current, and temperature-current binomial formula of each measurement point, and to calculate the temperature error of each measurement point based on the calculated temperature and the measured temperature of each measurement point.

[0061] The first accuracy evaluation module is used to determine whether the accuracy of the measured temperature, actual resistance, current and partial discharge obtained based on the circuit loop meets the requirements, provided that 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 under test based on the measurement temperature and partial discharge quantity corresponding to each measurement point.

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

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

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

[0066] 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. When the processor executes the computer program, it implements a method for detecting cable joint diameter mismatch defects according to any embodiment of the present invention.

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

[0068] The present invention provides a storage medium including 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, it implements a method for detecting cable joint diameter mismatch defects according to any embodiment of the present invention.

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

[0070] This invention provides a method for detecting cable joint diameter mismatch defects. The method includes: acquiring cable parameters and test environment parameters of a test cable; wherein the test cable is composed of two cable segments of the same length but different copper core radii connected together, and the two cable segments are connected by a contact resistance; the test environment parameters include a test current; subsequently, based on the cable parameters and the test environment parameters, a cable temperature rise simulation model is established; then, based on the cable temperature rise simulation model, the temperature rise of the test cable is simulated under different test currents and different contact resistances, and the first temperature-current binomial, second temperature-current binomial, and third temperature-current binomial equations corresponding to the test cable at a first measurement point, a second measurement point, and a third measurement point are fitted; wherein the first measurement point is the connection point of the cable segments, the second measurement point is located at a predetermined distance to the left of the first measurement point, and the third measurement point is located at the first measurement point... The test is conducted at the preset distance on the right. Then, based on the pre-built circuit loop for the withstand voltage test, the measured temperature and actual resistance of the cable under test at the first, second, and third measurement points, the current of the cable under test, and the partial discharge quantity of the cable under test are obtained. Subsequently, based on the measured temperature, actual resistance, current, and temperature-current binomial formula corresponding to each measurement point, the calculated temperature corresponding to each measurement point is obtained, and the temperature error corresponding to each measurement point is calculated based on the calculated temperature and measured temperature. Then, if any temperature error does not exceed the preset error threshold, the accuracy of the measured temperature, actual resistance, current, and partial discharge quantity obtained based on the circuit loop is determined to meet the requirements. Finally, based on the measured temperature and partial discharge quantity corresponding to each measurement point, it is determined whether there is a mismatch defect in the connector wire diameter of the cable under test. Therefore, this invention determines the temperature-current binomial formula of the cable measurement point by constructing a cable temperature rise simulation model. Then, it compares the measured temperature of the cable under test with the calculated temperature calculated by the temperature-current binomial formula. When the error is within the allowable range, it means that the temperature of the measured point is close to the actual temperature. Then, based on each measured value, it detects the mismatch defect of the joint wire diameter of the cable under test, thereby reducing the error when detecting the mismatch of the joint wire diameter. Attached Figure Description

[0071] Figure 1 This is a flowchart illustrating a method for detecting cable joint diameter mismatch defects according to an embodiment of the present invention.

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

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

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

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

[0076] Figure 6 This is a schematic diagram of a detection device for cable joint diameter mismatch defects provided in an embodiment of the present invention. Detailed Implementation

[0077] The technical solutions of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0078] like Figure 1 As shown, an embodiment of the present invention provides a method for detecting cable joint diameter mismatch defects, comprising:

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

[0080] Specifically, the cable parameters mentioned above include: the density of the cable insulation material, the thermal conductivity of the cable insulation material, the specific heat capacity of the cable insulation material, the electrical conductivity of the cable insulation material, the thermal conductivity coefficient of the cable insulation material, and the resistance at various points on the cable. The test parameters mentioned above include: electric potential, externally injected current density, test current, current source, heat source in the cable insulation material, and ambient temperature.

[0081] Specifically, the aforementioned test cable is 70mm².2 120mm 2 300mm 2 A cross-sectional view of a 10kV three-core cable is shown below. Figure 2 As shown, the cable mainly consists of a conductor, optical fiber, and outer materials. The conductor mainly consists of a water-blocking conductor, an inner semi-conductive layer, and a copper shield. A filler layer separates the conductor from the sheath. The outer materials mainly consist of an inner sheath, steel tape armor, and an outer sheath. The parameters of each structural component of the test cable are shown in the table below:

[0082] Parameters of each structural component of the cable

[0083]

[0084]

[0085] Specifically, two 500mm long cables are used, with a 0.1mm difference in the cross-sectional area of ​​the copper cores of the two cables. The contact resistance is used to simulate a loose connection. That is, the looser the contact, the greater the resistance at the contact point and the lower the conductivity. The contact resistance is expressed as a percentage of the copper conductivity.

[0086] Step S102: Establish a cable temperature rise simulation model based on the cable parameters and the test environment parameters;

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

[0088] Based on the cable parameters and the test environment parameters, the control equations for the electric field module, the solid heat transfer module, the electrothermal coupling, the heat conduction, the temperature boundary, the normal heat flux density boundary, and the convective heat transfer coefficient boundary are established.

[0089] Based on the control equations of the electric field module, the solid heat transfer module, the electrothermal coupling control equation, the heat conduction control equation, the temperature boundary, the normal heat flux density boundary, and the convective heat transfer coefficient boundary, the cable temperature rise simulation model is obtained.

[0090] The control equation for the electric field module is as follows:

[0091]

[0092] J = σE + J e

[0093]

[0094] In the formula, J represents the current density vector, with units of A / m. 3 , Q represents the vector differential operator. j This indicates a current source, with units of A / m. 3 σ represents electrical conductivity, with units of S / m, and E represents the electric field intensity vector, with units of V / m. Electric potential is expressed in V and J. e This represents the externally injected current density, expressed in A / m. 3 ;

[0095] The control equation for 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 under normal pressure, T represents the cable temperature, λ represents the thermal conductivity of the cable insulation material in W / (m·K), and Q1 represents the heat source in the cable insulation material in V / m. 3 ;

[0098] The electrothermal coupling control equation is as follows:

[0099]

[0100] In the formula, ρ represents the density of the cable insulation material, with units of kg / m³. 3 C represents the specific heat capacity of the cable insulation material under normal pressure, in J / (kg·K), λ represents the thermal conductivity of the cable insulation material, in W / (m·K), and Q represents the heat source in the cable insulation material.

[0101] The heat conduction control equation is:

[0102]

[0103] The temperature value boundary is:

[0104]

[0105] The normal heat flux density boundary is:

[0106]

[0107] In the formula, q represents the heat flux density, with units of W / m³. 2 ;

[0108] The boundary of the convective heat transfer coefficient is:

[0109]

[0110] In the formula, h represents the convective heat transfer coefficient, with units of W / (m³). 2·K), T1 represents the cable temperature, and T2 represents the ambient temperature, both in K.

[0111] Preferably, the aforementioned cable temperature rise simulation model provides a theoretical basis for determining cable diameter matching. The aforementioned governing equations are mathematical descriptions of the internal physical processes of the cable, providing a theoretical basis for accurately understanding and analyzing the electromagnetic phenomena and heat transfer mechanisms of the cable during operation. These equations allow for in-depth study of the electrical and thermal characteristics of the cable under different operating conditions, laying the foundation for subsequent calculations and analyses.

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

[0113] Step S103: Based on the cable temperature rise simulation model, perform temperature rise simulation on the test cable under different test currents and different contact resistances, and fit the first temperature-current binomial, second temperature-current binomial, and third temperature-current binomial equations corresponding to 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;

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

[0115] Specifically, the test current is set to 50A and 250A. The radial temperature of the cable and the temperature at the connection point are shown schematically when the test current is 50A. 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. From Figure 3 As can be seen, when the test current is 50A, the looser the connection at the joint, the lower the conductivity, the higher the resistance, and the greater the temperature rise. The radial temperature of the cable and the temperature at the joint are shown below when the test current is 250A. Figure 4 As shown, Figure 4 Figure c shows the radial temperature of the cable when the test current is 250A. Figure 4 d in the figure shows the temperature at the cable connection point when the test current is 250A. From... Figure 4 As can be seen, when the test current is 250A, the contact resistance caused by the loose connection at the connection point causes a 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 cable body is 71.65℃.

[0116] In a preferred embodiment, the step of performing temperature rise simulation on the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and fitting the first temperature-current binomial, second temperature-current binomial, and third temperature-current binomial equations corresponding to the test cable at the first measurement point, the second measurement point, and the third measurement point, respectively, includes:

[0117] Based on the cable temperature rise simulation model, the temperature rise simulation of the test cable is carried out 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] From the test temperatures at all points, the first test temperature corresponding to the first measurement point, the second test temperature corresponding to the second measurement point, and the third test temperature corresponding to the third measurement point are extracted.

[0119] Obtain the first resistance of the test cable at the first measurement point, the second resistance at the second measurement point, and the third resistance at the third measurement point;

[0120] Based on the first test temperature, the first cable resistance and the corresponding test current at the first measurement point, a binomial fit is performed to obtain the first Joule term fitting coefficient and the first heat flow term fitting coefficient. Then, based on the first Joule term fitting coefficient and the first heat flow term fitting coefficient, the first temperature-current binomial is obtained.

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

[0122] T O =a O λI 2 R O +b O

[0123] In the formula, T O Indicates the first test temperature, a O R represents the fitting coefficient of the first Joule term, I represents the test current, and R represents the fitting coefficient of the first Joule term. O b represents the resistance of the first cable. O This represents the fitting coefficient for the first heat flow term.

[0124] Based on the second test temperature, the second cable resistance, and the corresponding test current at the second measurement point, a binomial fit is performed to obtain the second Joule term fitting coefficient and the second heat flow term fitting coefficient. Then, based on the second Joule term fitting coefficient and the second heat flow term fitting coefficient, the second temperature-current binomial is obtained.

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

[0126] T A =a A λI 2 R A +b A

[0127] In the formula, T A Indicates the second test temperature, a A R represents the fitting coefficient of the second Joule term. A Indicates the resistance of the second cable, b A This represents the fitting coefficient for the second heat flow term.

[0128] Based on the third test temperature, the third cable resistance, and the corresponding test current at the third measurement point, a binomial fit is performed to obtain the fitting coefficient of the third Joule term and the fitting coefficient of the third heat flow term. Then, based on the fitting coefficient of the third Joule term and the fitting coefficient of the third heat flow term, the third temperature-current binomial is obtained.

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

[0130] T B =a B λI 2 R B +b B

[0131] In the formula, T B Indicates the third test temperature, a B R represents the fitting coefficient of the third Joule term. B Indicates the resistance of the third cable, b B This represents the fitting coefficient for the third heat flow term.

[0132] In this preferred embodiment, based on the cable temperature rise simulation model, the temperature rise of the test cable is simulated 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 obtained by fitting.

[0133] Step S104: Based on the pre-built circuit loop for the handover withstand voltage test, obtain the measured temperature and actual resistance of the cable under test at the first measurement point, the second measurement point and the third measurement point, the current of the cable under test, and the partial discharge of the cable under test.

[0134] The circuit loop described above is illustrative. Figure 5As shown, it mainly includes a high-voltage partial discharge circuit and a high-current circuit, with cable insulation between the two circuits to prevent mutual interference. The measuring end consists of a current transformer (ammeter), an infrared thermal imager (thermometer), and a partial discharge meter. These three devices connect to the network via Wi-Fi and synchronously sample data. The infrared thermal imager measures the temperature at the first, second, and third measurement points; the current transformer measures the current; and the partial discharge meter measures the partial discharge quantity.

[0135] Step S105: Calculate the calculated temperature for each measurement point based on the measured temperature, actual resistance, current, and the temperature-current binomial formula for each measurement point. Calculate the temperature error for each measurement point based on the calculated temperature and the measured temperature.

[0136] In a preferred embodiment, the step of calculating the calculated temperature corresponding to each measurement point based on the measured temperature, actual resistance, current, and temperature-current binomial formula for each measurement point includes:

[0137] Based on the first measured temperature, the first actual resistance, the current, and the first temperature-current binomial formula corresponding to the first measurement point, the first calculated temperature corresponding to the first measurement point is calculated.

[0138] The second calculated temperature corresponding to the second measurement point is obtained by calculating the second measured temperature, the second actual resistance, the current, and the second temperature-current binomial formula based on the second measured temperature, the second measured temperature, and the second measured temperature.

[0139] The third calculated temperature corresponding to the third measurement point is obtained based on the third measured temperature, the third actual resistance, the current, and the third temperature-current binomial formula corresponding to the third measurement point.

[0140] Specifically, in the binomial equations for temperature and current at each measurement point, the parameter values ​​for the experimental current and cable resistance at the corresponding positions are replaced with the aforementioned current and actual resistance to calculate the calculated temperature for each measurement point. 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: If any temperature error does not exceed the preset error threshold, determine that the accuracy of the measured temperature, actual resistance, current and partial discharge 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 indicates that the error between the measured temperature obtained from the current circuit loop and the actual temperature of the cable is not large, and the cable joint diameter mismatch defect can be detected based on the measured temperature.

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

[0144] If the temperature error exceeds the preset error threshold, and it is determined that the accuracy of the measured temperature, actual resistance, current and partial discharge obtained based on the circuit loop does not meet the requirements, the circuit loop is tested and then rebuilt.

[0145] Specifically, if all temperature errors exceed the preset error threshold, meaning 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 incorrect and rebuild the circuit loop.

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

[0147] Step S107: Based on the measured temperature and partial discharge amount at each measurement point, determine whether there is a mismatch defect in the connector diameter of the cable under test.

[0148] In a preferred embodiment, determining whether the connector wire diameter of the cable under test has a mismatch defect based on the measured temperature and partial discharge quantity at each measurement point includes:

[0149] Calculate the difference between the first measured temperature and the second measured temperature to obtain the first temperature difference; calculate the difference between the first measured temperature and the third measured temperature to obtain the second temperature difference.

[0150] If 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 a preset temperature threshold, and the partial discharge amount is not less than a preset discharge amount threshold, then it is determined that the connector wire diameter of the cable under test has no mismatch defect; otherwise, it is determined that the connector wire diameter of the cable under test has a mismatch defect.

[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 joint crimping point does not exceed 8% (it is difficult to crimp if it exceeds 8%), the difference in cable cross-sectional area and resistance on both sides of the crimping tube does not exceed 8%, and the heat flow term fitting coefficient is basically the same in the same environment, therefore, when mismatch defects exist, 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 a large cross-section is necessarily less than that at a small cross-section, the relative temperature criterion is as follows when a mismatch defect exists:

[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 from the cable current carrying capacity table based on the cross-sectional area), the absolute temperature criterion is obtained: when the temperature at all three measurement points is less than 90 degrees, it indicates that there is a mismatch defect.

[0158] Specifically, experience shows that if the cable diameter is mismatched and there are no defects, the partial discharge is less than 50 pC.

[0159] In this preferred embodiment, the presence of a mismatch defect in the connector diameter of the cable under test is determined based on the measured temperature at each measurement point and the partial discharge quantity.

[0160] Based on the above method embodiments, the present invention provides corresponding apparatus embodiments.

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

[0162] The module includes a parameter acquisition module, a simulation model construction module, a temperature fitting module, a parameter measurement module, a temperature difference calculation module, a first accuracy evaluation module, and a defect detection module.

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

[0164] The simulation model construction module is used to establish a cable temperature rise simulation model based on the cable parameters and the test environment parameters.

[0165] The temperature fitting module is used to simulate the temperature rise of the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and to fit the first temperature-current binomial, the second temperature-current binomial, and the third temperature-current binomial corresponding to 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 under test at the first measurement point, the second measurement point and the third measurement point, the current of the cable under test and the partial discharge of the cable under test, 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 of each measurement point based on the measured temperature, actual resistance, current, and temperature-current binomial formula of each measurement point, and to calculate the temperature error of each measurement point based on the calculated temperature and the measured temperature of each measurement point.

[0168] The first accuracy evaluation module is used to determine whether the accuracy of the measured temperature, actual resistance, current and partial discharge obtained based on the circuit loop meets the requirements, provided that 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 under test based on the measurement temperature and partial discharge quantity corresponding to each measurement point.

[0170] In a preferred embodiment, it further includes: a second accuracy evaluation module;

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

[0172] It should be noted that the device embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationship between modules indicates that they have a communication connection, which can be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without creative effort. The above schematic diagram is merely an example of a device for detecting cable joint diameter mismatch defects and does not constitute a limitation on a device for detecting cable joint diameter mismatch defects. It may include more or fewer components than shown, or combine certain components, or use different components.

[0173] Based on the above method embodiments, the present invention provides corresponding terminal device 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. When the processor executes the computer program, it implements a method for detecting cable joint diameter mismatch defects as described in any embodiment of the present invention.

[0175] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the device.

[0176] The aforementioned terminal devices may be computing devices such as desktop computers, laptops, handheld computers, and cloud servers. These devices may include, but are not limited to, processors and memory.

[0177] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. This processor is the control center of the device, connecting various parts of the device via various interfaces and lines.

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

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

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

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

[0182] Compared with the prior art, by implementing the above embodiments of the present invention, it is possible to determine whether the measured data are accurate, thereby reducing the error when detecting cable joint diameter mismatch defects.

[0183] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method of detecting a cable joint mismatch defect, characterized by, The method comprises the following steps: obtaining cable parameters of a test cable and test environment parameters; wherein the test cable is connected by two cable sections with the same length but different copper core radii, and the two cable sections are connected by a contact resistance; the test environment parameters include a test current; establishing a cable temperature rise simulation model according to the cable parameters and the test environment parameters; performing temperature rise simulation on the test cable under different test currents and different contact resistances according to the cable temperature rise simulation model, and fitting to obtain a first temperature-current binomial, a second temperature-current binomial and a third temperature-current binomial corresponding to a first measurement point, a second measurement point and a third measurement point of the test cable respectively; wherein the first measurement point is a connection point of the cable sections, the second measurement point is located at a preset distance on the left side of the first measurement point, and the third measurement point is located at the preset distance on the right side of the first measurement point; obtaining the measured temperature and actual resistance of a to-be-tested cable at the first measurement point, the second measurement point and the third measurement point, the current of the to-be-tested cable, and the partial discharge quantity of the to-be-tested cable according to a circuit loop previously built for a transfer withstand voltage test; calculating the calculation temperature corresponding to each measurement point according to the measured temperature, actual resistance, current and temperature-current binomial corresponding to each measurement point, and calculating the temperature error corresponding to each measurement point according to the calculation temperature and the measured temperature corresponding to each measurement point; determining that the accuracy of the measured temperature, actual resistance, current and partial discharge quantity obtained based on the circuit loop meets the requirements in the case that any one temperature error does not exceed a preset error threshold; determining whether the joint wire diameter of the to-be-tested cable has a mismatch defect according to the measured temperature of each measurement point and the partial discharge quantity.

2. The method of claim 1, wherein the method further comprises: Further comprising: in the case that all the temperature errors exceed the preset error threshold, determining that the accuracy of the measured temperature, actual resistance, current and partial discharge quantity obtained based on the circuit loop does not meet the requirements, and rebuilding the circuit loop after detecting the circuit loop.

3. The method of claim 1, wherein the method further comprises: The method of establishing a cable temperature rise simulation model according to the cable parameters and the test environment parameters comprises the following steps: establishing an electric field module control equation, a solid heat transfer module control equation, an electro-thermal coupling control equation, a heat conduction control equation, a temperature value boundary, a normal heat flux density boundary, and a convection heat transfer coefficient boundary according to the cable parameters and the test environment parameters; obtaining the cable temperature rise simulation model according to the electric field module control equation, the solid heat transfer module control equation, the electro-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; wherein the electric field module control equation is: wherein denotes the current density vector, denotes the current source, denotes the conductivity, denotes the electric field strength vector, denotes the electric potential, denotes the externally injected current density; the solid heat transfer module control equation is: wherein represents the density of the cable insulation material, represents the specific heat capacity of the cable insulation material at normal pressure, T represents the cable temperature, represents the thermal conductivity of the cable insulation material, represents the heat source in the cable insulation material; the electro-thermal coupling control equation is: wherein C represents the specific heat capacity of the cable insulation material at normal pressure. the heat conduction control equation is: wherein Q represents a heat source in the cable insulation material; the temperature value boundary is: the normal heat flux density boundary is: wherein q represents the heat flux density; the convection heat transfer coefficient boundary is: In the formula, h represents a convective heat transfer coefficient, T represents the ambient temperature.

4. The method for detecting cable joint diameter mismatch defects according to claim 3, characterized in that, The temperature rise simulation of the test cable is performed under different test currents and different contact resistances according to the cable temperature rise simulation model, and first, second and third temperature-current binomials corresponding to the first, second and third measuring points of the test cable are fitted, including: The temperature rise simulation of the test cable is performed under different test currents and different contact resistances according to the cable temperature rise simulation model, and the test temperature of each point of the test cable under each test current and each contact resistance is obtained; The first test temperature corresponding to the first measuring point, the second test temperature corresponding to the second measuring point, and the third test temperature corresponding to the third measuring point are extracted from all point test temperatures; The first resistance of the test cable at the first measuring point, the second resistance at the second measuring point, and the third resistance at the third measuring point are obtained; According to the first test temperature, the first resistance and the corresponding test current of the first measuring point, binomial fitting is performed to obtain the first Joule term fitting coefficient and the first heat flow term fitting coefficient, and then the first temperature-current binomial is obtained according to the first Joule term fitting coefficient and the first heat flow term fitting coefficient. According to the second test temperature, the second resistance and the corresponding test current of the second measuring point, binomial fitting is performed to obtain the second Joule term fitting coefficient and the second heat flow term fitting coefficient, and then the second temperature-current binomial is obtained according to the second Joule term fitting coefficient and the second heat flow term fitting coefficient. According to the third test temperature, the third resistance and the corresponding test current of the third measuring point, 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. The method of claim 4, wherein the step of detecting the mismatch of the cable joint is performed by using a method of detecting a mismatch of a diameter of a cable joint. The calculation temperature corresponding to each measuring point is calculated according to the measured temperature, the actual resistance, the current and the temperature-current binomial corresponding to each measuring point, including: The first calculation temperature corresponding to the first measuring point is calculated according to the first measured temperature, the first actual resistance, the current and the first temperature-current binomial corresponding to the first measuring point. The second calculation temperature corresponding to the second measuring point is calculated according to the second measured temperature, the second actual resistance, the current and the second temperature-current binomial corresponding to the second measuring point. The third calculation temperature corresponding to the third measuring point is calculated according to the third measured temperature, the third actual resistance, the current and the third temperature-current binomial corresponding to the third measuring point.

6. The method of claim 5, wherein the step of detecting the mismatch of the cable joint is performed by using a method of detecting a mismatch of a diameter of a cable joint. Whether the joint wire diameter of the cable to be measured has a mismatch defect is determined according to the measured temperature and the partial discharge amount of each measuring point, including: The first temperature difference is obtained by calculating the difference between the first measured temperature and the second measured temperature, and the second temperature difference is obtained by calculating the difference between the first measured temperature and the third measured temperature. When the quotient of the first temperature difference and the second temperature difference is not in a 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 a preset temperature threshold, and the local discharge amount is not less than a preset discharge amount threshold, it is determined that the joint wire diameter of the to-be-measured cable has no mismatch defect; otherwise, it is determined that the joint wire diameter of the to-be-measured cable has a mismatch defect.

7. An apparatus for detecting a cable joint mismatch defect, characterized by, Comprise: A parameter acquisition module, a simulation model construction module, a temperature fitting module, a parameter measurement module, a temperature difference calculation module, a first accuracy evaluation module, and a defect detection module; The parameter acquisition module is configured to acquire cable parameters of a test cable and test environment parameters; wherein the test cable is connected by two cable segments with the same length but different copper core radii, and the two cable segments are connected by a contact resistance; and the test environment parameters include a test current; The simulation model construction module is configured to establish a cable temperature rise simulation model according to the cable parameters and the test environment parameters; The temperature fitting module is configured 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 fit to obtain first, second, and third temperature-current binomials corresponding to first, second, and third measurement points of the test cable respectively; wherein the first measurement point is a connection point of the cable segments, the second measurement point is located at a preset distance left of the first measurement point, and the third measurement point is located at the preset distance right of the first measurement point; The parameter measurement module is configured to acquire measurement temperatures and actual resistances of a to-be-measured cable at first, second, and third measurement points, a current of the to-be-measured cable, and a local discharge amount of the to-be-measured cable according to a circuit loop previously built for a joint withstand voltage test; The temperature difference calculation module is configured to calculate a calculation temperature corresponding to each measurement point according to the measurement temperature, the actual resistance, the current, and the temperature-current binomial corresponding to each measurement point, and calculate a temperature error corresponding to each measurement point according to the calculation temperature and the measurement temperature corresponding to each measurement point; The first accuracy evaluation module is configured to determine that the accuracy of the measurement temperature, the actual resistance, the current, and the local discharge amount acquired based on the circuit loop meets the requirements in a case where any one of the temperature errors does not exceed a preset error threshold; The defect detection module is configured to determine whether the joint wire diameter of the to-be-measured cable has a mismatch defect according to the measurement temperature corresponding to each measurement point and the local discharge amount.

8. The apparatus for detecting a mismatch defect of a cable joint according to claim 7, wherein Further comprise: A second accuracy evaluation module; The second accuracy evaluation module is configured to determine that the accuracy of the measurement temperature, the actual resistance, the current, and the local discharge amount acquired based on the circuit loop does not meet the requirements in a case where the temperature errors all exceed the preset error threshold, and to rebuild the circuit loop after detecting the circuit loop.

9. A terminal device, comprising: The computer program product comprises a computer program and a storage medium. The computer program is stored in the storage medium and configured to be executed by a processor. The processor executes the computer program to implement the method for detecting the cable joint diameter mismatch defect according to any one of claims 1 to 6.

10. A storage medium, characterized by The storage medium comprises a stored computer program. When the computer program runs, the storage medium controls the device where the storage medium is located to execute the method for detecting the cable joint diameter mismatch defect according to any one of claims 1 to 6.

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