Injection flow testing method and system for welding state of steel grounding grid

Abstract

The invention provides an injection flow test method and system for a welding state of a steel grounding grid, and relates to the technical field of power grids. According to the method, a normal linear conductor in a grounding grid is subjected to a current injection test, a conduction impedance fitting function between the conduction impedance per unit length of the linear conductor and the test current of the current injection test is obtained through data fitting, and then a welding spot through-current impedance calculation model is constructed based on the conduction impedance fitting function; and calculating the calculated impedance of the welding spot under the normal condition. In addition, flow injection testing is carried out on all the welding spots, the testing impedance of all the welding spots is obtained, the calculated impedance and the testing impedance are compared, the welding state is judged, automatic calculation and testing of the welding state in the grounding grid are achieved, the accuracy of evaluation of the welding state in the grounding grid is improved, and the performance of the grounding grid is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power grid, and in particular to a current injection testing method and system for a welding state of a steel grounding grid. Background Art

[0002] The welding process performance of the grounding grid welding construction process has a great influence on the composition, structure, mechanical properties and certain welding defects (such as pores and crystal cracks) of the weld metal. There may be many welding defects in the grounding grid welding construction process, such as pores, inclusions, cracks, etc. Therefore, timely detection of the grounding grid welding state is of great significance for controlling the grounding grid welding quality and preventing grounding grid welding defects.

[0003] At present, the detection of solder joints in grounding grids mostly adopts the method of appearance observation, which observes the possible pores and cracks in the solder joints to determine whether the solder joints are normal or not. When there are pores, inclusions, and cracks inside the solder joints, the appearance observation method will lead to inaccurate judgment of the welding state, affecting the performance of the grounding grid. Summary of the invention

[0004] The present invention provides a flow injection test method and system for the welding state of a steel grounding grid, which can realize automatic testing of the welding state in the grounding grid, improve the accuracy of the welding state in the grounding grid, and ensure the performance of the grounding grid.

[0005] In a first aspect, the present invention provides a current injection test method for the welding state of a steel grounding grid, the method comprising: obtaining a grounding scheme diagram, weld point locations and current injection test data of each weld point of the grounding grid to be tested; performing a current injection test on a straight conductor in the grounding grid to be tested, and performing data fitting to obtain a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the current injection test; constructing a calculation model of the weld through-current impedance based on the grounding scheme diagram and the weld point locations, as well as the conduction impedance fitting function; the calculation model is used to calculate the through-current impedance of the weld under normal conditions; calculating the test impedance of each weld point based on the test data and a preset test impedance formula; calculating the calculated impedance of each weld point based on the test data and the calculation model of the weld through-current impedance; determining the welding state of each weld point based on the calculated impedance and the test impedance of each weld point, the welding state including abnormal weld point and normal weld point.

[0006] In a possible implementation, the welding state of each weld point is determined based on the calculated impedance and test impedance of each weld point, including: for any weld point, if the first calculated impedance of the weld point is greater than twice the first test impedance, the weld point is determined to be an observable weld point, and the observable weld point is a weld point whose welding state is pending and needs further observation; the first calculated impedance is the calculated impedance corresponding to the first test current, and the first test impedance is the test impedance corresponding to the first test current; if the first calculated impedance of the weld point is less than or equal to twice the first test impedance, the welding state of the weld point is determined to be a normal state.

[0007] In a possible implementation, for any weld, if the first calculated impedance of the weld is greater than twice the first test impedance, then after determining that the weld is an observable weld, it also includes: for any weld to be observed among the observable welds, if the second test impedance of the weld to be observed is less than a preset threshold, then determining that the welding state of the weld to be observed is a normal state; the second test impedance is a test impedance corresponding to a second test current, and the second test current is less than the first test current; if the second test impedance of the weld to be observed is greater than or equal to a preset threshold, then determining that the welding state of the weld to be observed is an abnormal state; the abnormal state indicates that the weld is cracked and broken.

[0008] In one possible implementation, a current injection test is performed on a straight conductor in a grounding grid to be tested, and data fitting is performed to obtain a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the current injection test, including: using different levels of test currents to perform a current injection test on a straight conductor of a set length to obtain the current injection test data of the straight conductor; the current injection test data includes the test voltages at both ends of the straight conductor under different test currents; based on the current injection test data of the straight conductor and the conductor length of the straight conductor, the conduction impedance per unit length of the straight conductor under each level of test current is calculated; based on the conduction impedance per unit length of the straight conductor under each level of test current and the test currents at each level, data fitting is performed to obtain the conduction impedance fitting function.

[0009] In a possible implementation, based on the grounding scheme diagram and the positions of the weld points, and the on-resistance fitting function, a calculation model of the weld point current impedance is constructed, including: based on the grounding scheme diagram and the positions of the weld points, determining the topological relationship between the weld points and the branches in the grounding network to be tested; based on the topological relationship between the weld points and the branches, determining the first correlation matrix and the second correlation matrix; the first correlation matrix is ​​used to characterize the correlation between the weld point voltage and the branch voltage; the second correlation matrix is ​​used to characterize the correlation between the weld point current and the branch current; based on the conductor length of each branch and the on-resistance fitting function, constructing the branch conductor conduction impedance matrix; the branch conductor impedance matrix uses the test current of the injection current test as a variable; based on the first correlation matrix, the branch voltage column vector is constructed with the weld point voltage column vector as a variable; the weld point voltage column vector is a vector composed of the test voltages on both sides of each weld point in the injection current test; based on the branch voltage column vector and the branch conductor conduction impedance matrix, constructing the branch current column vector; based on the branch current column vector and the second correlation matrix, constructing the weld point current column vector. The solder joint current column vector takes the test current and test voltage of the injection current test as variables; based on the solder joint current column vector and the solder joint voltage column vector, a calculation model of the solder joint current impedance is constructed.

[0010] In a possible implementation, the test impedance of each solder joint is calculated based on the test data and a preset test impedance formula, including: for any solder joint, the test impedance of the solder joint is calculated based on the following preset test impedance formula;

[0011]

[0012] Where X(I) is the test impedance of the solder joint, U n (k) is the test voltage at the starting point of the solder joint test, U n (m) is the test voltage at the end point of the solder joint test, and I is the detection current of the solder joint in the injection current test.

[0013] In a possible implementation, before calculating the test impedance of each weld based on the test data and the preset test impedance formula, it also includes: constructing a conduction test weld voltage column vector based on the test current column vector, the first correlation matrix and the branch conductor impedance matrix; constructing a weld current column vector based on the conduction test weld voltage column vector, the first correlation matrix, the second correlation matrix and the branch conductor impedance matrix; constructing a preset test impedance formula based on the weld current column vector and the weld voltage column vector.

[0014] In a possible implementation, based on the test data and the calculation model of the solder joint current impedance, the calculation impedance of each solder joint is calculated, including: Step 1, initializing the number of iterations N it=1; Step 2: For each solder joint, based on the test data corresponding to the second test current and the calculation model of the solder joint through-current impedance, calculate the second calculated impedance corresponding to the second test current, and let I 0 =I 1 =||I n || 2 ; Step 3, for each solder joint, based on the test data corresponding to the first test current and the calculation model of the solder joint through-current impedance, calculate the first calculated impedance corresponding to the first test current; and let I 1 =||I n || 2 ; Step 4, calculate the two-norm convergence criterion; The two-norm convergence criterion is |I 1 -I 0 |≤10 -5 ; Step 5, if |I 1 -I 0 |>10 -5 , and the number of iterations is less than the maximum number of iterations, repeat steps 3 to 5 until the number of iterations is greater than or equal to the maximum number of iterations or |I 1 -I 0 |≤10 -5 ;if |I 1 -I 0 |>10 -5 , and the number of iterations is greater than or equal to the maximum number of iterations, then it is determined that the first calculation impedance calculation fails; Step 6, if |I 1 -I 0 |≤10 -5 , then the output is the first calculation impedance that satisfies the two-norm convergence criterion.

[0015] In one possible implementation, if the second test impedance of the weld to be observed is greater than or equal to a preset threshold, then after determining that the welding state of the weld to be observed is an abnormal state, it also includes: repairing the weld to be observed, and performing a current injection test on the modified weld to be observed with a second test current to obtain a repair test impedance of the weld to be observed; if the repair test impedance of the weld to be observed is less than the preset threshold, then determining that the welding state of the weld to be observed is a normal state; if the repair test impedance of the weld to be observed is greater than or equal to the preset threshold, then determining that the welding state of the weld to be observed is an abnormal state.

[0016] In a second aspect, an embodiment of the present invention provides a current injection test device for the welding status of a steel grounding grid, the device comprising: a communication module, for obtaining a grounding scheme diagram, weld point positions and current injection test data of each weld point of the grounding grid to be tested; a processing module, for performing a current injection test on a straight conductor in the grounding grid to be tested, and performing data fitting to obtain a conduction impedance fitting function between the unit length conduction impedance of the straight conductor and the test current of the current injection test; based on the grounding scheme diagram and the weld point positions, and the conduction impedance fitting function, a calculation model of the weld point through-current impedance is constructed; the calculation model is used to calculate the through-current impedance of the weld under normal conditions; based on the test data and a preset test impedance formula, the test impedance of each weld point is calculated; based on the test data and the calculation model of the weld point through-current impedance, the calculated impedance of each weld point is calculated; based on the calculated impedance and the test impedance of each weld point, the welding status of each weld point is determined, and the welding status includes abnormal weld point and normal weld point.

[0017] In the third aspect, an embodiment of the present invention provides a current injection test system for the welding state of a steel grounding grid, the current injection test system comprising a voltage measuring device, a current measuring device, a DC current source and a current injection test device; the voltage measuring device is connected to both sides of a weld to be tested in the grounding grid to be tested, and detects the starting voltage and the ending voltage of the weld; the current measuring device, the DC current source and the weld to be tested are electrically connected to form a path, and the current measuring device is used to measure the detection current flowing through the weld to be tested; the DC current source outputs a current source for each level of test current; the current injection test device is connected to the voltage measuring device, the current measuring device and the DC current source, receives the current injection test data of the voltage measuring device and the DC measuring device, and controls the DC current source to output each level of test current, and the current injection test device is also used to execute the steps of the method described in the first aspect and any possible implementation method of the first aspect.

[0018] In a fourth aspect, an embodiment of the present invention provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to perform the steps of the method described in the first aspect and any possible implementation method of the first aspect.

[0019] In a fifth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and wherein when the computer program is executed by a processor, the steps of the method described in the first aspect and any possible implementation method of the first aspect are implemented.

[0020] The present invention provides a method and system for testing the welding state of a steel grounding grid. The present invention performs a flow injection test on a normal straight conductor in the grounding grid, and obtains a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the flow injection test through data fitting, and then constructs a calculation model of the flow impedance of the welding point based on the conduction impedance fitting function; and calculates the calculated impedance of the welding point under normal conditions. The present application also performs a flow injection test on each welding point to obtain the test impedance of each welding point, compares the calculated impedance with the test impedance, determines the welding state, realizes automatic calculation and testing of the welding state in the grounding grid, improves the accuracy of the welding state in the grounding grid, and ensures the performance of the grounding grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 It is a flow chart of a flow injection test method for a steel grounding grid in a welding state provided by an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of a current injection test for a straight conductor of a grounding grid provided by an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of a solder joint injection test provided by an embodiment of the present invention;

[0025] Figure 4 It is a flow chart of another method for testing the flow of a steel grounding grid in a welding state provided by an embodiment of the present invention;

[0026] Figure 5 It is a schematic diagram of a calculation process of a solder joint on-resistance provided by an embodiment of the present invention;

[0027] Figure 6 It is a structural schematic diagram of a flow injection testing device for a steel grounding grid in a welding state provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0029] In the description of the present invention, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, "at least one" and "plurality" refer to two or more. The words "first", "second", etc. do not limit the quantity and execution order, and the words "first", "second", etc. do not limit them to be different.

[0030] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0031] In addition, the terms "including" and "having" and any variations thereof mentioned in the description of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include other steps or modules that are not listed, or may optionally include other steps or modules that are inherent to these processes, methods, products or devices.

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following will be described through specific embodiments in conjunction with the accompanying drawings of the present invention.

[0033] As described in the background art, the traditional solder joint appearance inspection method has the problem of inaccurate inspection, which affects the performance of the grounding grid.

[0034] In order to solve the above technical problems, an embodiment of the present invention provides a current injection test method for the welding state of a steel grounding grid. First, a 55Hz amplitude modulation power supply is used to obtain the characteristics of the on-resistance per unit length of the grounding grid conductor changing with the effective value of the through-current, and the nonlinear model of the branch on-resistance for the on-current injection test is solved; secondly, a through-resistance simulation model considering the nonlinearity of the branch on-resistance is established, and the overall abnormal state of the weld is determined by comparing the simulation results of the on-current injection test with the on-site 500A high current test results; thirdly, a list of observable welds in abnormal state is given through the simulation results, and a 100A DC current test is performed for investigation. If the 100A DC current on-resistance of the weld is greater than 1mΩ, it is determined that the weld is of poor quality and needs to be repaired; finally, after the weld defect is repaired, the 500A high current on-resistance is re-tested, and the conclusion that "the down conductor and the grounding conductor connected to the measurable node have defects such as cracks and breaks" is given based on the results, and further on-site appearance inspection is recommended.

[0035] like Figure 1 As shown, the flow injection test method for the welding state of the steel grounding grid provided by the embodiment of the present invention includes steps S101-S106.

[0036] S101, obtaining a grounding scheme diagram of the grounding grid to be tested, positions of solder joints, and injection current test data of each solder joint.

[0037] Exemplarily, an embodiment of the present invention can collect the grounding conductor construction layout diagram of the grounding grid project, the material property parameters of the grounding conductor, the layout location of the down conductor, the grounding plan diagram of the electrical equipment in the substation, the welding point locations of the down conductor connection, as well as the regional distribution of transformers in the substation and the regional distribution of outgoing line fields of different voltages, and select the main transformer area and the outgoing line field areas of different voltages as the detection areas for measuring the down conductor welding points.

[0038] S102, performing a current injection test on a straight conductor in the grounding grid to be tested, and performing data fitting to obtain a fitting function of the on-resistance per unit length of the straight conductor and the test current of the current injection test.

[0039] In some embodiments, the on-resistance fitting function is a function between the on-resistance per unit length of the straight conductor and the test current of the injection current test.

[0040] Exemplarily, the current injection testing system for the welding state of a steel grounding grid provided in an embodiment of the present invention includes a hardware part and a software part.

[0041] The hardware part mainly includes a 55Hz constant current power supply with a maximum output of 500A, a 100A DC constant current power supply, a voltage measuring device and a current measuring device. The software part mainly includes a grounding grid welding state calculation method and a calculation system.

[0042] like Figure 2 As shown, an embodiment of the present invention provides a schematic diagram of current injection test for a straight conductor of a grounding grid. A voltage measuring device is connected in parallel to both sides of a straight conductor of length L, and a current measuring device and a 55Hz current source are connected in series to both sides of a straight conductor of length L.

[0043] The on-state impedance is tested with the change of the through-current amplitude using grounding conductor materials on site. A straight conductor is selected for testing on site, and the two current electrodes are located outside the voltage electrode. The 55Hz AC current of the test is passed through the current electrode and connected to the current sampling system. The voltage electrode is connected to the voltage sampling system to measure the voltage waveform. The minimum distance between the two voltage electrodes is L, which is used to convert the on-state impedance to the on-state impedance per unit length.

[0044] As a possible implementation manner, step S102 may be specifically implemented as steps S1021 - S1023 .

[0045] S1021. Use test currents of different levels to perform a current injection test on a straight conductor of a set length to obtain current injection test data of the straight conductor.

[0046] In some embodiments, the injection current test data includes test voltages across the linear conductor at different test currents.

[0047] S1022. Based on the injection current test data of the straight conductor and the conductor length of the straight conductor, calculate the unit length on-resistance of the straight conductor at each level of test current.

[0048] S1023. Based on the on-resistance per unit length of the straight conductor at each level of test current and the test current at each level, data fitting is performed to obtain an on-resistance fitting function.

[0049] S103, based on the grounding scheme diagram and the solder joint positions, as well as the on-resistance fitting function, a calculation model of the solder joint current impedance is constructed.

[0050] In the embodiment of the present application, the calculation model is used to calculate the current impedance of the solder joint under normal conditions.

[0051] As a possible implementation method, the calculation model can be constructed through steps S1031-S1037.

[0052] S1031. Based on the grounding scheme diagram and the locations of the welding points, determine the topological relationship between the welding points and the branches in the grounding grid to be tested.

[0053] S1032: Determine a first association matrix and a second association matrix based on the topological relationship between the welding points and the branches.

[0054] In some embodiments, the first correlation matrix is ​​used to characterize the correlation between the welding point voltage and the branch voltage; and the second correlation matrix is ​​used to characterize the correlation between the welding point current and the branch current.

[0055] S1033. Construct a branch conductor conduction impedance matrix based on the conductor length of each branch and the conduction impedance fitting function.

[0056] In some embodiments, the branch conductor impedance matrix uses the test current of the injection current test as a variable;

[0057] S1034. Based on the first correlation matrix, a branch voltage column vector is constructed using the welding point voltage column vector as a variable.

[0058] In some embodiments, the solder joint voltage column vector is a vector formed by the test voltages at both sides of each solder joint in the current injection test.

[0059] S1035. Construct a branch current column vector based on the branch voltage column vector and the branch conductor conduction impedance matrix;

[0060] S1036. Construct a welding point current column vector based on the branch current column vector and the second association matrix.

[0061] In some embodiments, the welding point current column vector takes the test current and the test voltage of the current injection test as variables.

[0062] S1037. Based on the welding point current column vector and the welding point voltage column vector, construct a calculation model of welding point current impedance.

[0063] S104, calculating the test impedance of each solder joint based on the test data and a preset test impedance formula.

[0064] Exemplarily, for any solder joint, the embodiment of the present invention may calculate the test impedance of the solder joint based on the following preset test impedance formula;

[0065]

[0066] Where X(I) is the test impedance of the solder joint, U n (k) is the test voltage at the starting point of the solder joint test, U n (m) is the test voltage at the end point of the solder joint test, and I is the detection current of the solder joint in the injection current test.

[0067] Exemplarily, before step S104, the embodiment of the present invention may construct a preset test impedance formula based on steps A1-A4.

[0068] A1. Construct a conduction test solder joint voltage column vector based on the test current column vector, the first correlation matrix and the branch conductor impedance matrix.

[0069] A2. Construct a welding point current column vector based on the conduction test welding point voltage column vector, the first correlation matrix, the second correlation matrix and the branch conductor impedance matrix.

[0070] A3. Based on the welding point current column vector and the welding point voltage column vector, a preset test impedance formula is constructed.

[0071] S105 , calculating the calculated impedance of each solder joint based on the test data and the calculation model of the solder joint current impedance.

[0072] As a possible implementation manner, step 105 can be specifically implemented as steps 1 to 6.

[0073] Step 1: Initialize the number of iterations N it =1;

[0074] Step 2: For each solder joint, based on the test data corresponding to the second test current and the calculation model of the solder joint through-current impedance, calculate the second calculated impedance corresponding to the second test current, and set I 0 =I 1 =||I n || 2 ;

[0075] Step 3: For each solder joint, based on the test data corresponding to the first test current and the calculation model of the solder joint through-current impedance, calculate the first calculated impedance corresponding to the first test current; and let I 1 =||I n || 2 ;

[0076] Step 4: Calculate the two-norm convergence criterion; the two-norm convergence criterion is |I 1 -I 0 |≤10 -5 ;

[0077] Step 5: If |I 1 -I 0 |>10 -5 , and the number of iterations is less than the maximum number of iterations, repeat steps 3 to 5 until the number of iterations is greater than or equal to the maximum number of iterations or |I 1 -I 0 |≤10 -5 ;if I 1 -I 0 |>10 -5 , and the number of iterations is greater than or equal to the maximum number of iterations, it is determined that the first calculation impedance calculation fails;

[0078] Step 6: If |I 1 -I 0 |≤10 -5, then the output is the first calculation impedance that satisfies the two-norm convergence criterion.

[0079] like Figure 3 As shown in FIG. 1 , an embodiment of the present invention provides a schematic diagram of a solder joint current injection test. A solder joint is formed by welding two conductors in a grounding grid. A voltage measuring device, a current measuring device and a DC current source are shown in FIG. Figure 3 After the injection test, the injection test data of each solder joint is obtained.

[0080] S106 , determining the welding state of each welding point based on the calculated impedance and the tested impedance of each welding point.

[0081] In the embodiment of the present application, the welding status includes abnormal welding points and normal welding points.

[0082] As a possible implementation manner, step S106 can be specifically implemented as steps S1061-S1064.

[0083] S1061. For any solder joint, if the first calculated impedance of the solder joint is greater than twice the first tested impedance, the solder joint is determined to be an observable solder joint.

[0084] In some embodiments, the observable weld is a weld whose welding status is pending and needs further observation; the first calculated impedance is the calculated impedance corresponding to the first test current, and the first test impedance is the test impedance corresponding to the first test current.

[0085] S1062: If the first calculated impedance of the solder joint is less than or equal to twice the first tested impedance, it is determined that the soldering state of the solder joint is a normal state.

[0086] S1063: For any weld point to be observed among the observable weld points, if the second test impedance of the weld point to be observed is less than a preset threshold, it is determined that the welding state of the weld point to be observed is a normal state.

[0087] In some embodiments, the second test impedance is a test impedance corresponding to a second test current, and the second test current is smaller than the first test current.

[0088] Exemplarily, the first test current may be 500A, and the second test current may be 100A.

[0089] S1064: If the second test impedance of the weld to be observed is greater than or equal to a preset threshold, determine that the welding state of the weld to be observed is an abnormal state; the abnormal state indicates that the weld is cracked or broken.

[0090] For example, the preset threshold value may be 1 mΩ. If the DC current conduction resistance of the solder joint 100A is greater than 1 mΩ, it is determined that the solder joint quality is poor and needs to be repaired.

[0091] The present invention provides a method for testing the welding state of a steel grounding grid by injection current. The method performs an injection current test on a normal straight conductor in the grounding grid, and obtains a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the injection current test through data fitting. Then, a calculation model of the conduction impedance of the welding point is constructed based on the conduction impedance fitting function; and the calculated impedance of the welding point under normal conditions is calculated. The present application also performs an injection current test on each welding point to obtain the test impedance of each welding point, compares the calculated impedance with the test impedance, determines the welding state, realizes automatic calculation and testing of the welding state in the grounding grid, improves the accuracy of the welding state in the grounding grid, and ensures the performance of the grounding grid.

[0092] Optionally, the flow injection test method for the welding state of a steel grounding grid provided in an embodiment of the present invention further includes steps S201-S203 after step S106.

[0093] S201, repairing the solder joint to be observed, and performing a current injection test on the modified solder joint to be observed with a second test current to obtain a repair test impedance of the solder joint to be observed.

[0094] S202: If the repair test impedance of the solder joint to be observed is less than a preset threshold, it is determined that the welding state of the solder joint to be observed is a normal state.

[0095] S203: If the repair test impedance of the solder joint to be observed is greater than or equal to a preset threshold, determine that the welding state of the solder joint to be observed is an abnormal state.

[0096] In this way, the present invention can repair defective welding spots and re-test the repaired welding spots to ensure the accuracy of the welding state.

[0097] Figure 4 A schematic flow chart of a flow injection test method for a steel grounding grid in a welding state provided in an embodiment of the present invention. Figure 5 Figure 2 is a schematic diagram of the calculation process of the solder joint on-resistance.

[0098] like Figure 4 and Figure 5 As shown, the flow injection test method for the welding state of the steel grounding grid provided in the embodiment of the present invention can be implemented as steps S1-S3.

[0099] S1. Collect basic information of grounding grid and its solder joints.

[0100] S2. Obtain the characteristics of the on-resistance per unit length of the grounding grid conductor changing with the effective value of the through-current, that is, construct an on-resistance fitting function.

[0101] The embodiment of the present invention can select the effective value of the test current I 551A, 2A, 3A, 5A, 7A, 10A, 14A, 20A, 30A, 50A, 70A, 140A, 150A, 200A, 300A, 500A. Through the test, a series of data on the change of the on-resistance per unit length with the effective value of the test current is obtained.

[0102]

[0103] Among them, z r is the real part of the on-resistance Z, z i is the imaginary part of the on-resistance z, U 55 is the effective value of the test voltage at 55Hz, I 55 is the effective value of the test current at 55Hz. Afterwards, a spline fitting is performed on the test data to generate an on-resistance fitting function F.

[0104]

[0105] Wherein, I is the effective value of any test current in the range of 1 to 500 A, and F(I) is the on-resistance fitting function.

[0106] S3: Establish the basic theoretical method for calculating the welding status of the grounding grid.

[0107] A grounding grid welding state calculation method is established for the working conditions of the conduction test in different areas. The grounding grid welding state calculation method is realized by implementing the injection flow experiment between different welding points and solving the conduction impedance.

[0108] S3.1: According to different areas, select the grounding wire welding points of the main transformer down conductor flat steel, the arrester grounding wire welding points, the line switch grounding wire welding points and the site portal frame grounding wire welding points. These welding points in the area are arranged and combined, and two welding points are selected for injection test.

[0109] S3.2: The specific approach of the injection impedance analysis model is to organize the grounding model of the grounding grid, divide the solder joints and branches of the grounding grid, and obtain all the divided solder joints and divided conductor branches of the grounding grid.

[0110] S3.3: A branch conductor conduction impedance matrix is ​​formed from all the split conductor branches of the grounding grid.

[0111] [z]=diag([z 1 ,z 2 ,…,z b ,…,z n ]);

[0112] Where [z] is the branch conductor conduction impedance matrix, and diag is the operation function that expands the row vectors to the matrix diagonal. The conduction impedance z of branch conductor b is bDetermined by the following formula:

[0113]

[0114] Among them, L b is the length of the conductor, I b is the test current of the conductor, z b (I b ) is the on-resistance of the branch conductor.

[0115] S3.4: Arrange the topological relationship between the welding point and the branch, obtain the welding point voltage-branch voltage correlation topological matrix A, and then obtain the branch current column vector I b .

[0116] Define the two welding points of branch b as the starting point k and the end point m, A(b,k)=1, A(b,m)=-1, and take 0 for other elements in this row. The welding point voltage column vector U n and the branch voltage column vector U b The operation relationship is: U b =AU n .

[0117] Branch current column vector I b For: I b =z -1 U b .

[0118] Among them, I b is the branch current column vector, U b is the branch voltage column vector, U n is the welding point voltage column vector, z is the branch conductor conduction impedance matrix, and A is the first correlation matrix.

[0119] S3.5: Based on the topological relationship between the welding point and the branch, obtain the welding point current and branch current correlation topological matrix B, and then obtain the welding point current column vector I n .

[0120] Define the two welding points of branch b as the starting point k and the end point m, B(b,k)=0.5, B(b,m)=0.5, and take 0 for other elements in this row. Welding point current column vector I n and the branch current column vector I b The operation relationship is:

[0121] I n =B|I b |;

[0122] Among them, I n is the welding point current column vector, I b is the branch current column vector, and B is the second incidence matrix.

[0123] S3.6: Obtain the on-resistance of the current test.

[0124] Exemplarily, step S3.6 may be implemented as steps S3.6.1-3.6.4.

[0125] S3.6.1: Generate a conduction test current column vector F. For the test start point k and the end point m, the elements of the test current column vector F are respectively F(k)=-I and F(m)=I, and the other elements are 0.

[0126] S3.6.2: Solve for the voltage column vector U of the continuity test solder joint n :

[0127] U n =[A T z -1 A[ -1 F;

[0128] Where, the superscript T is the matrix transpose operation, F is the test current column vector, and U n is the welding point voltage column vector.

[0129] S3.6.3: Solve for the continuity test solder joint current column vector I n .

[0130] I n =B|z -1 AU n |;

[0131] Among them, I n is the welding point current column vector, B is the second correlation matrix, z is the branch conductor conduction impedance matrix, A is the first correlation matrix, U n is the welding point voltage column vector.

[0132] S3.6.4: Solve for the on-resistance X of the test:

[0133]

[0134] Where X(I) is the test impedance when the injection test current is I; U n (m) is the voltage at the test end point m, U n (k) is the voltage at the test starting point k, and I is the detection current of the current measurement device in the injection current test.

[0135] S3.7: Initialize the grounding grid welding state calculation.

[0136] For the test starting point k and end point m, let I = 100A, solve for the on-resistance X(100), and record the number of iterations N it is 1, let I n The second norm of ||In || 2 , with I 0 =I 1 =||I n || 2 Perform the base transfer step 3.8.

[0137] S3.8: Perform a continuity test at I = 500A and solve for the conduction impedance X(500). N it =N it +1,I 1 =||I n || 2 .

[0138] S3.9: Obtain a list of observable solder joints for the injection flow test.

[0139] Welding point current column vector I n The two-norm convergence criterion for convergence judgment is:

[0140] |I 1 -I 0 |≤10 -5 ;

[0141] If |I 1 -I 0 |≤10 -5 Satisfied, if Nit<1001, N it =N it +1,I 0 =||I n || 2 , go to step S3.7; if N it >1000, end outputting calculation failure information.

[0142] If |I 1 -I 0 |≤10 -5 Satisfy, obtain the observable solder joint list, if the conduction test solder joint current column vector I n If the element is greater than 0.1I, the solder joint is included in the observable solder joint list {N}.

[0143] Output X(500) and go to step S3.10.

[0144] S3.10: X(500) is compared with the test result. If X(500)>2 times the test result, the mechanism of local solder joint detection needs to be activated, otherwise the test is terminated.

[0145] like Figure 3As shown, the observable solder joint list {N} given by the simulation is tested with a DC current of 100A in sequence. If the on-resistance is greater than 1mΩ, the solder joint is considered to be of poor quality and needs to be repaired until the on-resistance of the solder joint is ≤1mΩ.

[0146] S3.11: After repairing all measurable nodes, recalculate the 500A high current conduction impedance X(500) and compare it with the test result of the repaired solder joint impedance. If X(500) < 2 times the test result, the test is terminated. Otherwise, the conclusion is given that the down conductor and the grounding conductor connected to the measurable node have defects such as cracks and breaks, and it is recommended to conduct on-site appearance inspection.

[0147] The present invention proposes a flow injection test method and system for the welding state of a steel grounding grid. The nonlinear conduction characteristics of the grounding conductor are obtained through testing, and then an implementation plan for detecting the welding state of the grounding grid is formed. The results of the 500A high current detection are compared with the simulation evaluation results, and a list of welds with problems is obtained through analysis. A 100A low current weld resistance test is further performed to discover and repair weld defects. A flow injection test method and system for the welding state of a steel grounding grid provides technical support for flow injection test methods and evaluation means for detecting the welding state of the grounding grid through the cooperation of hardware and software technologies.

[0148] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0149] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0150] Figure 6 The schematic diagram of the structure of a flow injection test device for a steel grounding grid in a welding state provided by an embodiment of the present invention is shown. The flow injection test device 300 includes a communication module 301 and a processing module 302 .

[0151] The communication module 301 is used to obtain the grounding scheme diagram of the grounding grid to be tested, the positions of the welding points and the injection current test data of each welding point.

[0152] The processing module 302 is used to perform a current injection test on the straight conductor in the grounding grid to be tested, and perform data fitting to obtain a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the current injection test; based on the grounding scheme diagram and the solder joint positions, and the conduction impedance fitting function, a calculation model of the solder joint current impedance is constructed; the calculation model is used to calculate the current impedance of the solder joint under normal conditions; based on the test data and a preset test impedance formula, the test impedance of each solder joint is calculated; based on the test data and the calculation model of the solder joint current impedance, the calculated impedance of each solder joint is calculated; based on the calculated impedance and the test impedance of each solder joint, the welding state of each solder joint is determined, and the welding state includes abnormal solder joints and normal solder joints.

[0153] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A flow injection test method for a steel grounding grid in a welding state, characterized in that: include: Obtain the grounding scheme diagram, solder joint locations and injection current test data of each solder joint of the grounding grid to be tested; Performing a current injection test on the straight conductor in the grounding grid to be tested, and performing data fitting to obtain a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the current injection test; Based on the grounding scheme diagram and the solder joint positions, and the on-resistance fitting function, a calculation model of solder joint on-resistance is constructed; the calculation model is used to calculate the on-resistance of the solder joint under normal conditions; Calculating the test impedance of each solder joint based on the test data and a preset test impedance formula; Calculating the calculated impedance of each solder joint based on the test data and the calculation model of the solder joint current impedance; Based on the calculated impedance and the tested impedance of each welding point, the welding state of each welding point is determined, and the welding state includes an abnormal welding point and a normal welding point.

2. The flow injection test method for the welding state of the steel grounding grid according to claim 1 is characterized in that: The step of determining the welding state of each welding point based on the calculated impedance and the tested impedance of each welding point comprises: For any welding point, if the first calculated impedance of the welding point is greater than 2 times of the first test impedance, the welding point is determined to be an observable welding point, and the observable welding point is a welding point whose welding state is to be determined and needs further observation; the first calculated impedance is the calculated impedance corresponding to the first test current, and the first test impedance is the test impedance corresponding to the first test current; If the first calculated impedance of the welding spot is less than or equal to twice of the first tested impedance, it is determined that the welding state of the welding spot is a normal state.

3. The flow injection test method for the welding state of the steel grounding grid according to claim 2 is characterized in that: For any solder joint, if the first calculated impedance of the solder joint is greater than 2 times of the first tested impedance, then after determining that the solder joint is an observable solder joint, the method further includes: For any observable solder joint, If the second test impedance of the weld to be observed is less than a preset threshold, it is determined that the welding state of the weld to be observed is a normal state; the second test impedance is a test impedance corresponding to a second test current, and the second test current is less than the first test current; If the second test impedance of the weld to be observed is greater than or equal to a preset threshold, it is determined that the welding state of the weld to be observed is an abnormal state; the abnormal state indicates that the weld is cracked and broken.

4. The flow injection test method for the welding state of the steel grounding grid according to claim 1 is characterized in that: The method of performing a current injection test on a straight conductor in the grounding grid to be tested and performing data fitting to obtain a conduction impedance fitting function between the conduction impedance per unit length of the straight conductor and the test current of the current injection test includes: Using different levels of test currents, an injection current test is performed on a linear conductor of a set length to obtain injection current test data of the linear conductor; the injection current test data includes test voltages at both ends of the linear conductor under different test currents; Based on the injection current test data of the linear conductor and the conductor length of the linear conductor, the unit length on-resistance of the linear conductor at each level of test current is calculated; Based on the on-resistance per unit length of the straight conductor under each level of test current and the test current at each level, data fitting is performed to obtain the on-resistance fitting function.

5. The flow injection test method for the welding state of the steel grounding grid according to claim 1 is characterized in that: The step of constructing a calculation model of solder joint current impedance based on the grounding scheme diagram and solder joint positions, and the on-resistance fitting function, includes: Based on the grounding scheme diagram and the positions of the welding points, determining the topological relationship between the welding points and the branches in the grounding grid to be tested; Based on the topological relationship between the welding point and the branch, a first correlation matrix and a second correlation matrix are determined; the first correlation matrix is ​​used to characterize the correlation between the welding point voltage and the branch voltage; the second correlation matrix is ​​used to characterize the correlation between the welding point current and the branch current; Based on the conductor length of each branch and the conduction impedance fitting function, a branch conductor conduction impedance matrix is ​​constructed; the branch conductor impedance matrix uses the test current of the injection current test as a variable; Based on the first correlation matrix, a branch voltage column vector is constructed with a solder point voltage column vector as a variable; the solder point voltage column vector is a vector composed of test voltages on both sides of each solder point in the current injection test; Constructing a branch current column vector based on the branch voltage column vector and the branch conductor conduction impedance matrix; Based on the branch current column vector and the second association matrix, a welding spot current column vector is constructed; the welding spot current column vector takes the test current and test voltage of the injection current test as variables; Based on the welding point current column vector and the welding point voltage column vector, a calculation model of the welding point current impedance is constructed.

6. The flow injection test method for the welding state of the steel grounding grid according to claim 1 is characterized in that: The calculating the test impedance of each solder joint based on the test data and a preset test impedance formula includes: For any solder joint, the test impedance of the solder joint is calculated based on the following preset test impedance formula; Where X(I) is the test impedance of the solder joint, U n (k) is the test voltage at the starting point of the solder joint test, U n (m) is the test voltage at the end point of the solder joint test, and I is the detection current of the solder joint in the injection current test.

7. The flow injection test method for the welding state of the steel grounding grid according to claim 1 is characterized in that: Before calculating the test impedance of each solder joint based on the test data and the preset test impedance formula, the method further includes: Constructing a continuity test solder joint voltage column vector based on the test current column vector, the first correlation matrix and the branch conductor impedance matrix; Constructing a welding point current column vector based on the conduction test welding point voltage column vector, the first correlation matrix, the second correlation matrix and the branch conductor impedance matrix; The preset test impedance formula is constructed based on the welding point current column vector and the welding point voltage column vector.

8. The flow injection test method for the welding state of the steel grounding grid according to claim 1 is characterized in that: The calculating impedance of each solder joint based on the test data and the calculation model of the solder joint current impedance includes: Step 1: Initialize the number of iterations N it =1; Step 2: For each solder joint, based on the test data corresponding to the second test current and the calculation model of the solder joint current impedance, calculate the second calculated impedance corresponding to the second test current, and set I0=I1=||I n ||2; Step 3: For each solder joint, based on the test data corresponding to the first test current and the calculation model of the solder joint current impedance, calculate the first calculated impedance corresponding to the first test current; and set I1 = || I n ||2; Step 4: Calculate the two-norm convergence criterion; the two-norm convergence criterion is |I1-I0|≤10 -5 ; Step 5: If |I1-I0|>10 -5 , and the number of iterations is less than the maximum number of iterations, repeat steps 3 to 5 until the number of iterations is greater than or equal to the maximum number of iterations or |I1-I0|≤10 -5 ; If I1-I0|>10 -5 , and the number of iterations is greater than or equal to the maximum number of iterations, it is determined that the first calculation impedance calculation fails; Step 6: If |I1-I0|≤10 -5 , then the output is the first calculation impedance that satisfies the two-norm convergence criterion.

9. The flow injection test method for the welding state of the steel grounding grid according to claim 1, characterized in that: If the second test impedance of the welding point to be observed is greater than or equal to the preset threshold, after determining that the welding state of the welding point to be observed is an abnormal state, the method further includes: Repairing the solder joint to be observed, and performing a current injection test on the modified solder joint to be observed with a second test current to obtain a repair test impedance of the solder joint to be observed; If the repair test impedance of the solder joint to be observed is less than a preset threshold, it is determined that the soldering state of the solder joint to be observed is a normal state; If the repair test impedance of the solder joint to be observed is greater than or equal to a preset threshold, it is determined that the welding state of the solder joint to be observed is an abnormal state.

10. A flow injection test system for welding state of steel grounding grid, characterized in that: The injection current test system includes a voltage measuring device, a current measuring device, a direct current source and an injection current test device; the voltage measuring device is connected to both sides of the welding point to be tested in the grounding grid to be tested to detect the starting voltage and the end voltage of the welding point; the current measuring device, the direct current source and the welding point to be tested are electrically connected to form a path, and the current measuring device is used to measure the detection current flowing through the welding point to be tested; the direct current source outputs the current source of each level of test current; the injection current test device is connected to the voltage measuring device, the current measuring device and the direct current source, receives the injection current test data of the voltage measuring device and the direct current measuring device, and controls the direct current source to output the test current of each level, and the injection current test device is also used to perform the steps of the method as described in any one of claims 1 to 9.

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