Substation grounding grid corrosion diagnosis method

Abstract

The invention discloses a transformer substation grounding grid corrosion diagnosis method. The method comprises the specific steps that parameters such as the size and the original cross section radius of a grounding grid are obtained through a design drawing; testing to obtain the potential between the ground surface vertically above the position of the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid downleads and the voltage between the downleads; constructing a ground potential solving equation set of the conductor section of the grounding grid; and initializing the radius and the oxide coverage rate of the conductor section of the grounding grid, and substituting the radius and the oxide coverage rate into the solving equation set to solve the potential between the ground surface vertically above the position of the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid downleads and the voltage between the downleads. And comparing whether the calculated and actually measured errors meet requirements, if not, updating the radius of the conductor section and the oxide coverage rate for recalculation, and if so, outputting and evaluating the conductor section and the oxide coverage rate. The grounding grid ground potential and the voltage between grounding grid downleads are utilized to calculate the radius of the cross section of a grounding grid conductor section so as to evaluate the corrosion of the grounding grid conductor section.

Description

Technical Field

[0001] This patent relates to the field of power grid safe operation, specifically to a method for diagnosing corrosion of substation grounding grids. Background Technology

[0002] The substation grounding grid in a power system functions as a current dissipator and voltage equalizer, serving as a crucial foundation and guarantee for the safe and stable operation of the power grid. However, due to its long-term contact with the soil, it inevitably undergoes gradual corrosion under the influence of oxygen, moisture, and microorganisms. Corrosion reduces the overall current dissipation area of ​​the grounding grid, leading to an increase in its grounding resistance. This can cause safety indicators such as contact voltage within the substation to fail to meet requirements, posing safety hazards. In my country, the design life of grounding grids is generally required to be over 30 years, with 50 years considered for important hub substations; however, in some severely corroded areas, the actual service life is only 3-4 years. Therefore, to ensure the safe and stable operation of the power system, regular inspection and evaluation of the corrosion status of the grounding grid are essential.

[0003] Currently, the main methods for assessing corrosion of grounding grids include electromagnetic detection and electrical network methods. Electromagnetic detection yields weak signals that are easily interfered with, resulting in poor practical application. In the electrical network method, the limited number of accessible nodes in the grounding grid leads to underdeterminism in the equations, meaning the number of final solutions is not unique, thus compromising accuracy. Summary of the Invention

[0004] This invention provides a method for diagnosing corrosion of substation grounding grids, which at least has the technical effect of accurately guiding power grid operation and maintenance personnel to assess the corrosion status of grounding grids and perform timely maintenance.

[0005] This invention provides a method for diagnosing corrosion of substation grounding grids, the specific steps of which include:

[0006] Obtain the dimensions of the substation grounding grid, the length of the conductor segment between nodes, and the original cross-sectional radius of the conductor segment;

[0007] The test obtains the measured potential between the ground surface vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor, as well as the measured voltage between the down conductors.

[0008] The grounding grid is equivalent to a resistive network structure, and a set of equations is constructed to solve for the ground potential of the conductor segment of the grounding grid.

[0009] Initialize the radius of the grounding grid conductor segment and the oxide coverage, and substitute them into the system of equations to solve the calculated potential between the ground surface vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the calculated voltage between the down conductors.

[0010] Compare the measured potential and the measured voltage between the down conductors with the calculated potential and the calculated voltage between the down conductors to see if the error meets the requirements. If it does not meet the requirements, update the conductor segment radius and oxide coverage and recalculate. If it meets the requirements, output the grounding grid conductor segment radius and oxide coverage area.

[0011] Evaluate the corrosion of grounding grid conductor segments based on their radius.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] This patent first tests the grounding grid to obtain the voltage between the ground surface potential vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the voltage between the down conductors. Then, using the radius of the grounding grid conductor segment as an iterative variable, it calculates the voltage between the ground surface potential vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the voltage between the down conductors. The final radius of the grounding grid conductor segment is calculated by using the error between the measured voltage and the calculated voltage as the convergence condition. By comparing the original radius and the calculated radius of the grounding grid conductor segment, the corrosion status of the grounding grid conductor segment is obtained.

[0014] The invention involves comparing the ground surface potential vertically above the midpoint of the measurable conductor segment of the grounding grid obtained through testing with the voltage between the selected grounding grid down conductor and the voltage between the down conductors, as well as the voltage between the down conductors. Theoretically calculated voltages are then used to determine the radius of the grounding grid conductor through iterative calculations. Based on this, the degree of corrosion of the grounding grid conductor is assessed, thereby guiding power grid maintenance personnel in maintaining the grounding grid. This method is applicable to scenarios where the number of grounding grid nodes is limited and can calculate the radius of the grounding grid conductor segment, providing more accurate guidance for power grid maintenance personnel to assess the corrosion status of the grounding grid and perform timely maintenance.

[0015] The method of this invention comprehensively utilizes the voltage between the ground surface vertically above the midpoint of the grounding grid conductor segment and the selected grounding grid down conductor, as well as the voltage between the grounding grid down conductors, to achieve grounding grid corrosion assessment. This method is not limited by the number of down conductors, the corresponding equation system does not have underdeterminacy, and it considers the impact of grounding grid conductor segment corrosion on conductor leakage current, making the grounding grid corrosion assessment more accurate. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for diagnosing corrosion of a substation grounding grid according to the present invention.

[0017] Figure 2 This is a flowchart for diagnosing corrosion of substation grounding grids according to the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0019] This invention provides a method for diagnosing corrosion in substation grounding grids, and also a method for locating weak sections of subway rail insulation. Its flowchart is shown below. Figure 1 As shown, the details are as follows:

[0020] A method for diagnosing corrosion of substation grounding grids includes the following steps:

[0021] S1, obtain the substation grounding grid dimensions, inter-node conductor segment lengths, and original cross-sectional radii of the conductor segments;

[0022] S2, Test to obtain the measured potential between the ground surface vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor, as well as the measured voltage between the down conductors.

[0023] S3, the grounding grid is equivalent to a resistor network structure, and a set of equations is constructed to solve the potential of the conductor segment of the grounding grid to the ground.

[0024] S4. Initialize the radius of the grounding grid conductor segment and the oxide coverage. Substitute them into the system of equations to solve the calculated potential between the ground surface vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the calculated voltage between the down conductors.

[0025] S5. Compare the measured potential and the measured voltage between the down conductors with the calculated potential and the calculated voltage between the down conductors to see if the error meets the requirements. If it does not meet the requirements, update the conductor segment radius and oxide coverage and recalculate. If it meets the requirements, output the grounding grid conductor segment radius and oxide coverage area.

[0026] S6, assess the corrosion of grounding grid conductor segments based on the radius of the grounding grid conductor segment.

[0027] In one embodiment, the grounding grid is equivalent to a resistor network structure. The steps for constructing a set of equations to determine the ground potential of the conductor segment of the grounding grid include:

[0028] S1. Based on the obtained grounding grid size and quantity, the grounding grid is equivalent to a resistor network structure. An expression is established to describe the relationship between the voltage at the midpoint of any conductor segment of the grounding grid and the leakage current; an expression is established to describe the relationship between the soil potential near the midpoint of any conductor segment and the leakage current; an expression is established to describe the relationship between the leakage current of the conductor segment and the grounding grid potential to the ground.

[0029] S2, Substitute the grounding grid node and conductor segment numbers into the aforementioned expression, and combine them with the conductor segment oxide product coverage expression to form a matrix of equations for solving the ground potential at the midpoint of all conductor segments of the grounding grid.

[0030] In one embodiment, the initialization of the conductor segment radius and oxide coverage of the grounding grid, and the substitution of these parameters into a system of equations to solve for the calculated potential between the ground surface vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the calculated voltage between the down conductors, includes the following steps:

[0031] S1, Initialize the cross-sectional radius r of the grounding grid conductor. n and the coefficients in the expression for oxide coverage of conductor segments;

[0032] S2, Brought in the cross-sectional radius r of the grounding grid conductor n The coefficients in the oxide coverage expression are used to calculate the midpoint-to-ground potential of all conductor segments by solving the matrix of equations for the midpoint-to-ground potential of all conductor segments in the grounding grid.

[0033] S3, based on the potential of the midpoint to ground of all conductor segments Calculate the voltage between the ground surface vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor. and the voltage between the nodes where the two grounding grid down conductors are located.

[0034] In one embodiment, the assessment of grounding grid conductor segment corrosion based on the conductor segment radius includes the following steps:

[0035] Calculate the original cross-sectional radius r of each grounding grid conductor segment in sequence. c and conductor segment cross-sectional radius r n The ratio dig is used to determine whether the conductor segment is slightly corroded. If dig < 1.4, the conductor segment is considered to have mild corrosion; if 1.4 ≤ dig ≤ 3.2, the conductor segment is considered to have moderate corrosion; and if dig > 3.2, the conductor segment is considered to have severe corrosion.

[0036] In one embodiment, the voltage test method between the ground surface vertically above the midpoint of the grounding grid conductor segment and the selected grounding grid down conductor is as follows:

[0037] S1, Based on the substation grounding grid design drawings and on-site inspection, determine the actual measurable conductor section of the grounding grid, and record the node numbers at both ends of the measurable conductor section (i m ,j m The actual location and the total number of measurable conductor segments are N. m Where m = 1, 2, ..., N m The node where the downline is located is represented by k. h The total number is represented by N. k It is represented as, where h = 1, 2, ..., N k And arbitrarily select a downleader as the downleader reference point, and the node corresponding to the downleader reference point adopts k m It means that km ∈k h ;

[0038] S2, connect a positive terminal of a power supply to k m The negative terminal of the down conductor is injected into the ground surface vertically above any node of the grounding grid, so that the power supply is sufficient to make the position of the midpoint of one measurable conductor segment perpendicularly above the ground surface and the down conductor k of the grounding grid. m The power supply amplitude is adjusted to achieve a potential difference of 1V.

[0039] S3, based on the measurable conductor segment node (i m ,j m The reference electrode is then placed in the actual position (i) in sequence. m ,j m The soil surface directly above the midpoint between the two points is connected to a reference electrode at one end and a down conductor k at the other end. m Thus, the test obtains the lead-in k. m With all measurable conductor segments N m Voltage between the ground surface potentials vertically above the midpoint Connect one end of the measuring instrument to the down conductor k. h1 (h1∈h), the other end is connected to another downleader k. h2 (h2∈h), obtain the voltage between each pair of down conductors.

[0040] In one embodiment, the expression describing the relationship between the midpoint potential and leakage current of any conductor segment is represented by a combination of equations (1), (2), and (3):

[0041]

[0042] In formula (1) Let I be the potential at the center of the cross-section of the conductor segment between nodes i and j (referred to as the "midpoint potential"). Here, i is the grounding grid node number at one end of the conductor segment, and j is the node number at the other end of the conductor segment. J(i,j) G represents the leakage current of the conductor segment between nodes i and j. c(i,j) Let the longitudinal conductance be the conductor segment between nodes i and j. and Let i and j be the potentials of the grounding grid nodes, respectively. Formula (2) expresses the relationship between the midpoint potential of the conductor segment, the conductance of the conductor segment, the total leakage current of the conductor segment, and the excitation source current.

[0043]

[0044] In equations (2) and (3), i1, i2, i3 and i4 represent grounding grid nodes adjacent to grounding grid node i in the four directions of up, down, left and right; j1, j2, j3 and j4 represent grounding grid nodes adjacent to grounding grid node j in the four directions of up, down, left and right.

[0045] In one embodiment, the expression describing the relationship between the soil potential and leakage current at the midpoint of any conductor segment between nodes i and j is represented by equation (4):

[0046]

[0047] In formula (4) For all conductor segment leakage currents, the surface proximity (x) of the midpoint of the conductor segment between nodes i and j (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The sum of soil potentials generated by (x) (i,j) ,y (i,j) ,z (i,j) ) represents the coordinates of the midpoint potential of the conductor segment, r n(i,j) The radius of the cross-section of the conductor segment is... and The leakage current of conductor segment w and the injected negative current of the power source are respectively located in the coordinate (x) (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The soil potential generated at location ) where w is the conductor segment number, n c This represents the total number of conductor segments.

[0048] In one embodiment, the expression describing the relationship between the leakage current of any conductor segment at grounding grid nodes i and j and the grounding grid-to-ground potential is represented by (12):

[0049]

[0050] Among them, I J1 I represents the current leaking from the exposed portions of conductor segments at nodes i and j. J2 R represents the current leaking from the oxide-covered portion of the conductor segment; y This is the equivalent resistance of the oxide in the conductor segment; This is the potential of the midpoint of the conductor relative to ground. This represents the surface potential of the conductor oxide product relative to ground in this segment; υ (i,j) r represents the coverage of oxidation products in this conductor segment. n(i,j) r is the radius of the remaining central cylinder of the conductor after corrosion. c i is the original cross-sectional radius of the conductor segment; corr It is the natural corrosion current density; Ecorr It is the natural corrosion potential; β a It is the Tafel slope of the anode; β b Cathode Tafel slope.

[0051] In one embodiment, the oxide equivalent resistance R corresponding to any conductor segment of grounding grid nodes i and j y(i,j) This can be expressed by equation (13):

[0052]

[0053] Where L is the length of the conductor; ρ rust α represents the resistivity of the oxidation product. z α is the transfer coefficient. p These are the expansion coefficients, and all three are constants.

[0054] In one embodiment, the coverage of oxidation products of any conductor segment is υ (i,j) The value is represented by equation (14), where a o and b o These are the fitting coefficients to be solved:

[0055]

[0056] Where L is the length of the conductor; ρ rust α represents the resistivity of the oxidation product. z α is the transfer coefficient. p These are the expansion coefficients, and all three are constants.

[0057] The following specific embodiment illustrates this solution:

[0058] Step 1: Based on the substation grounding grid design drawings, obtain the location of the grounding grid installation, the location of the grounding grid nodes, the length L of the conductor segment between nodes, and the original cross-sectional radius r of the conductor segment. c The location of the grounding grid down conductor of the substation is obtained, and the grounding grid nodes and the conductor segments between the nodes are numbered, denoted by i and w respectively.

[0059] Step 2: Test and obtain the voltage between the ground surface potential vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor. and voltage between leads

[0060] Step 3: Based on the size and number of the grounding grid obtained in Step 1, the grounding grid is equivalent to a resistor network structure. An expression is established to describe the relationship between the voltage at the midpoint of any conductor segment of the grounding grid and the leakage current; an expression is established to describe the relationship between the soil potential near the midpoint of any conductor segment and the leakage current; and an expression is established to describe the relationship between the leakage current of the conductor segment and the grounding grid potential to the ground.

[0061] Step 4: Substitute the grounding grid node and conductor segment numbers into the expression described in Step 3, and combine them with the expression for the oxide product coverage rate of the conductor segment to form a matrix of equations for solving the ground potential at the midpoint of all conductor segments of the grounding grid.

[0062] Step 5: Initialize the cross-sectional radius r of the grounding grid conductor. n And the coefficients in the expression for oxide coverage of conductor segments.

[0063] Step 6: Incorporate the cross-sectional radius r of the grounding grid conductor. n And the coefficients in the oxide coverage expression, use the equations described in step 4 to calculate the midpoint-to-ground potential of all conductor segments.

[0064] Step 7: Based on the potential of the midpoint of all conductor segments to ground Calculate the voltage between the ground surface potential vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor. and the voltage between the nodes where the two grounding grid down conductors are located.

[0065] Step 8: Determine whether the error between the measured voltage in Step 2 and the calculated voltage in Step 7 meets the requirements. If not, update the cross-sectional radius of the grounding grid conductor according to the iterative algorithm and return to Step 6. Otherwise, output the cross-sectional radius of the grounding grid conductor in the current iterative solution process.

[0066] Step 9: Calculate the original cross-sectional radius r of each grounding grid conductor segment in sequence. c and conductor segment cross-sectional radius r n The ratio is rounded to obtain dig. If dig < 2, the conductor segment is judged to have mild corrosion; if 2 ≤ dig ≤ 9, the conductor segment is judged to have moderate corrosion; if dig > 9, the conductor segment is judged to have severe corrosion.

[0067] Furthermore, the voltage test method between the ground surface vertically above the midpoint of the grounding grid conductor segment mentioned in step 2 and the selected grounding grid down conductor is as follows:

[0068] S21. Based on the substation grounding grid design drawings and on-site inspection, determine the actual measurable conductor section of the grounding grid, and record the node numbers at both ends of the measurable conductor section (i m ,j m The actual location and the total number of measurable conductor segments are N. m Where m = 1, 2, ..., N m The node where the downline is located is represented by k. h The total number is represented by N. k It is represented as, where h = 1, 2, ..., N kAnd arbitrarily select a downleader as the downleader reference point, and the node corresponding to the downleader reference point adopts k. m It means that k m ∈k h .

[0069] S22. Connect a positive terminal of a power supply to k. m The negative terminal of the down conductor is injected into the ground surface perpendicularly above any node of the grounding grid. The power supply should ensure that the midpoint of one measurable conductor segment is perpendicularly connected to the ground surface above the ground conductor k of the grounding grid. m The power supply amplitude is adjusted to achieve a potential difference of 1V.

[0070] S23, Based on the measurable conductor segment node (i m ,j m The reference electrode is then placed in the actual position (i) in sequence. m ,j m The soil surface directly above the midpoint between () is measured. Further measurements are taken using a multimeter or similar measuring instrument, with one end connected to a reference electrode and the other end connected to the lead-in line k. m Thus, the test obtains the lead-in k. m With all measurable conductor segments N m Voltage between the ground surface potentials vertically above the midpoint Further connect one end of the measuring instrument to the lead wire k h1 (h1∈h), the other end is connected to another downleader k. h2 (h2∈h), thereby obtaining the voltage between each pair of down conductors.

[0071] Furthermore, the expression describing the relationship between the midpoint potential and leakage current of any conductor segment in step 3 is represented by a combination of equations (1), (2), and (3):

[0072]

[0073] In formula (1) The potential at the center of the cross-section of the conductor segment between nodes i and j (referred to as "midpoint potential") is the potential of the conductor segment between nodes i and j. i is the grounding grid node number at one end of the conductor segment, and j is the node number at the other end of the conductor segment. J(i,j) G represents the leakage current of the conductor segment between nodes i and j. c(i,j) Let the longitudinal conductance be the conductor segment between nodes i and j. and The potentials of grounding grid nodes i and j are respectively expressed by formula (2) as the relationship between the midpoint potential of the conductor segment, the conductor segment conductance, the total leakage current of the conductor segment and the excitation source current.

[0074]

[0075] In equations (2) and (3), i1, i2, i3 and i4 represent grounding grid nodes adjacent to grounding grid node i in the four directions of up, down, left and right; j1, j2, j3 and j4 represent grounding grid nodes adjacent to grounding grid node j in the four directions of up, down, left and right.

[0076] Furthermore, the expression describing the relationship between the soil potential and leakage current at the midpoint of any conductor segment between nodes i and j, as described in step 3, is represented by equation (4):

[0077]

[0078] In formula (4) For all conductor segment leakage currents, the surface proximity (x) of the midpoint of the conductor segment between nodes i and j (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The sum of soil potentials generated by (x) (i,j) ,y (i,j) ,z (i,j) ) represents the coordinates of the midpoint potential of the conductor segment, r n(i,j) Let be the radius of the cross-section of the conductor segment. and The leakage current of conductor segment w and the injected negative current of the power source are respectively located in the coordinate (x) (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The soil potential generated at location ) where w is the conductor segment number, n c This represents the total number of conductor segments.

[0079] Furthermore, This represents the leakage current of any conductor segment w from the beginning to the end of the segment, within the coordinate (x, y). (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The integral of the soil potential generated at point () is expressed by equation (5):

[0080]

[0081] This indicates that the injected source negative electrode current is located in the coordinate (x) (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The integral of the soil potential generated at point () is expressed by equation (6):

[0082]

[0083] In formula (5) For the soil layer Q where the grounding grid is located s Soil resistivity; I J (w) represents the leakage current of conductor segment w; (x) w ,y w ,z w ) represents the coordinates of the potential at the midpoint of any conductor segment w; L represents the length of any conductor segment; in equation (6), (x in ,y in ,z in ) represents the coordinates corresponding to the location of the negative terminal of the injected power source; in equations (5) and (6), a p b p To fit A q The coefficient of the complex exponential term used, c k d k To fit B q The coefficients of the complex exponential terms used satisfy the relationships shown in equations (7) and (8), respectively. The fitting methods can include the commonly used Prony approximation method, matrix bundle method, etc. χ represents the number of fitting sampling points, χ = 0, 1, 2, ..., 4N. s -1, N s The total number of soil layers; p and k represent the total number of soil layers, respectively. and Fitting term number.

[0084]

[0085] in and The system of equations (9) is constructed by substituting χ into the equations. The specific process is to successively substitute χ = 0, 1, 2, ..., 4N. s -1 Construct a system of equations (9) corresponding to any χ to solve A q (χ) and B q (χ), and then obtain soil layer Q. s corresponding and

[0086]

[0087] In the formula, q represents the soil layer number, q = 1, 2, ..., N s The if statement represents the interface number between soil layers q and q+1, where if = 1, 2, ..., N. s , where if=1 represents the interface between the ground and the air. z if This indicates the depth of the `if` statement within the interface. M q N q The value of z is determined by formula (10). p0 Indicates the depth of the source.

[0088]

[0089] Furthermore, the expression describing the relationship between the leakage current of any conductor segment at grounding grid nodes i and j and the grounding grid potential in step 3 is represented by (12):

[0090]

[0091] Among them, I J1 I represents the current leaking from the exposed portions of conductor segments at nodes i and j. J2 R represents the current leaking from the oxide-covered portion of the conductor segment; y This is the equivalent resistance of the oxide in the conductor segment; This is the potential of the midpoint of the conductor relative to ground. This represents the surface potential of the conductor oxide product relative to ground in this segment; υ (i,j) r represents the coverage of oxidation products in this conductor segment. n(i,j) r is the radius of the remaining central cylinder of the conductor after corrosion. c i is the original cross-sectional radius of the conductor segment; corr It is the natural corrosion current density; E corr It is the natural corrosion potential; β a It is the Tafel slope of the anode; β b Cathode Tafel slope.

[0092] Furthermore, the oxide equivalent resistance R corresponding to any conductor segment at grounding grid nodes i and j y(i,j) This can be expressed by equation (13):

[0093]

[0094] Where L is the length of the conductor; ρ rust α represents the resistivity of the oxidation product. z α is the transfer coefficient. p These are the expansion coefficients, and all three are constants.

[0095] Furthermore, the coverage of oxidation products in any conductor segment is υ (i,j) The value is represented by equation (14), where a o and b o These are the fitting coefficients to be solved:

[0096]

[0097] Where L is the length of the conductor; ρ rust α represents the resistivity of the oxidation product. z α is the transfer coefficient. p These are the expansion coefficients, and all three are constants.

[0098] Furthermore, based on the expression described in step 3, by substituting the grounding grid node numbers i and j, the conductor segment number w, and equation (14), a set of equations for solving the ground potential at the midpoint of all conductor segments of the grounding grid described in step 4 is constructed, and written in matrix form as shown in equation (15):

[0099]

[0100] Where G is the soil potential matrix corresponding to a unit leakage current, and G(w1,w2) represents the soil potential near the middle position of the w2 conductor when the 1A leakage current from the w1 conductor is at the middle position; B is the matrix formed by taking the absolute value of the correlation matrix of the equivalent circuit of the grounding grid and then transposing it; Y is the branch admittance matrix of the grounding grid; C is the matrix composed of the main diagonal elements of the node admittance matrix; I0 is the column vector of current injected into each node of the grounding grid, where node k m The injected current is I in All other nodes are zero; This is a column vector consisting of the potentials of the midpoints of all conductor segments relative to ground. This represents the leakage current calculated using the conductor segment's potential to ground according to expression (10).

[0101] Furthermore, in step 7, the grounding grid (i m ,j m The location of the midpoint of any measurable conductor segment between the points is perpendicular to the ground surface above the selected downleader reference point k. m voltage between Calculated using formula (16):

[0102]

[0103] Voltage between grounding grid lead-down conductors k in step 7 Calculated using formula (17):

[0104]

[0105] Furthermore, the grounding grid node (i m ,j m The voltage difference between the soil surface potential of the conductor segment and the soil potential adjacent to the conductor segment can be measured. Calculated using formula (18):

[0106]

[0107] in, This indicates that the leakage current in any conductor segment w is... The soil potential at the location is calculated using equation (5). Indicates the injected source negative current at The soil potential at the location is calculated using equation (6). This indicates the coordinates of the Earth's surface directly above the center of the conductor segment. express The soil potential at the location is calculated using equation (4). Let be the coordinates of the center of the cross-section at the middle position of the conductor segment. Let be the radius of the conductor segment.

[0108] Furthermore, the grounding grid node (i m ,j m The distance from the midpoint of the conductor segment to the downlead k can be measured between ) m Potential difference between nodes Calculated using formula (19):

[0109]

[0110] In equation (17) The required leakage current in formula (2) is calculated using formula (2), and the solution is obtained using formula (11). Calculate using formula (18).

[0111]

[0112] Furthermore, whether the error between the measured voltage in step 2 and the calculated voltage in step 6 in step 7 meets the requirements is measured by equation (21):

[0113]

[0114] The above description is merely a preferred embodiment of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

[0115] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications based on these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this application.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for diagnosing corrosion of substation grounding grids, characterized in that, Includes the following steps: Obtain the dimensions of the substation grounding grid, the length of the conductor segment between nodes, and the original cross-sectional radius of the conductor segment; The test obtains the measured potential between the ground surface vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor, as well as the measured voltage between the down conductors. The grounding grid is equivalent to a resistive network structure, and a set of equations is constructed to solve for the ground potential of the conductor segment of the grounding grid. Initialize the radius of the grounding grid conductor segment and the oxide coverage, and substitute them into the system of equations to solve the calculated potential between the ground surface vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the calculated voltage between the down conductors. Compare the measured potential and the measured voltage between the down conductors with the calculated potential and the calculated voltage between the down conductors to see if the error meets the requirements. If it does not meet the requirements, update the conductor segment radius and oxide coverage and recalculate. If it meets the requirements, output the grounding grid conductor segment radius and oxide coverage area. Evaluate the corrosion of grounding grid conductor segments based on their radius.

2. The method for diagnosing corrosion of a substation grounding grid according to claim 1, characterized in that, The grounding grid is equivalent to a resistor network structure. A set of equations for solving the ground potential of the conductor segment of the grounding grid is constructed, including the following steps: Based on the obtained grounding grid size and quantity, the grounding grid is equivalent to a resistor network structure. An expression is established to describe the relationship between the voltage at the midpoint of any conductor segment of the grounding grid and the leakage current; an expression is established to describe the relationship between the soil potential near the midpoint of any conductor segment and the leakage current; and an expression is established to describe the relationship between the leakage current of the conductor segment and the grounding grid potential to the ground. Substitute the grounding grid node and conductor segment numbers into the aforementioned expression, and combine them with the expression for the oxide product coverage of the conductor segment to form a matrix of equations for solving the ground potential at the midpoint of all conductor segments of the grounding grid.

3. The method for diagnosing corrosion of a substation grounding grid according to claim 1, characterized in that, The initialization of the conductor segment radius and oxide coverage of the grounding grid, substituted into the system of equations, is used to solve for the calculated potential between the ground surface vertically above the midpoint of the measurable conductor segment of the grounding grid and the selected grounding grid down conductor, as well as the calculated voltage between the down conductors. This includes the following steps: Initialize the cross-sectional radius r of the grounding grid conductor n and the coefficients in the expression for oxide coverage of conductor segments; Incorporating the cross-sectional radius r of the grounding grid conductor n The coefficients in the oxide coverage expression are used to calculate the midpoint-to-ground potential of all conductor segments by solving the matrix of equations for the midpoint-to-ground potential of all conductor segments in the grounding grid. Based on the potential of the midpoint to ground of all conductor segments Calculate the voltage between the ground surface vertically above the midpoint of the measurable conductor section of the grounding grid and the selected grounding grid down conductor. and the voltage between the nodes where the two grounding grid leads are located.

4. The method for diagnosing corrosion of a substation grounding grid according to claim 1, characterized in that, The method for assessing the corrosion of a grounding grid conductor segment based on its radius includes the following steps: Calculate the original cross-sectional radius r of each grounding grid conductor segment in sequence. c and conductor segment cross-sectional radius r n The ratio dig is used to determine whether the conductor segment is slightly corroded. If dig < 1.4, the conductor segment is considered to have mild corrosion; if 1.4 ≤ dig ≤ 3.2, the conductor segment is considered to have moderate corrosion; and if dig > 3.2, the conductor segment is considered to have severe corrosion.

5. The method for diagnosing corrosion of a substation grounding grid according to claim 1, characterized in that, The voltage test method between the ground surface vertically above the midpoint of the grounding grid conductor segment and the selected grounding grid down conductor is as follows: Based on the substation grounding grid design drawings and on-site inspection, determine the actual measurable conductor section of the grounding grid and record the node numbers at both ends of the measurable conductor section (i m ,j m The actual location and the total number of measurable conductor segments are N. m Where m = 1, 2, ..., N m The node where the downline is located is represented by k. h The total number is represented by N. k It is represented as, where h = 1, 2, ..., N k And arbitrarily select a downleader as the downleader reference point, and the node corresponding to the downleader reference point adopts k m It means that k m ∈k h ; Connect a power supply positive terminal to k m The negative terminal of the down conductor is injected into the ground surface vertically above any node of the grounding grid, so that the power supply is sufficient to make the position of the midpoint of one measurable conductor segment perpendicularly above the ground surface and the down conductor k of the grounding grid. m The power supply amplitude is adjusted to achieve a potential difference of 1V. Based on the measurable conductor segment node (i) m ,j m The reference electrode is then placed in the actual position (i) in sequence. m ,j m The soil surface directly above the midpoint between the two points is connected to a reference electrode at one end and a down conductor k at the other end. m Thus, the test obtains the lead-in k. m With all measurable conductor segments N m Voltage between the ground potentials vertically above the midpoint Connect one end of the measuring instrument to the down conductor k. h1 (h1∈h), the other end is connected to another downleader k. h2 (h2∈h), obtain the voltage between each pair of down conductors.

6. The method for diagnosing corrosion of a substation grounding grid according to claim 5, characterized in that, The expression describing the relationship between the midpoint potential and leakage current of any conductor segment is represented by a combination of equations (1), (2), and (3): In formula (1) Let I be the potential at the center of the cross-section of the conductor segment between nodes i and j (referred to as "midpoint potential"). Here, i is the grounding grid node number at one end of the conductor segment, and j is the node number at the other end of the conductor segment. J(i,j) G represents the leakage current of the conductor segment between nodes i and j. c(i,j) Let the longitudinal conductance be the conductor segment between nodes i and j. and Let i and j be the potentials of the grounding grid nodes, respectively. Formula (2) expresses the relationship between the midpoint potential of the conductor segment, the conductance of the conductor segment, the total leakage current of the conductor segment, and the excitation source current. In equations (2) and (3), i1, i2, i3 and i4 represent grounding grid nodes adjacent to grounding grid node i in the four directions of up, down, left and right; j1, j2, j3 and j4 represent grounding grid nodes adjacent to grounding grid node j in the four directions of up, down, left and right.

7. The method for diagnosing corrosion of a substation grounding grid according to claim 6, characterized in that, The expression describing the relationship between the soil potential near the midpoint of any conductor segment between nodes i and j and the leakage current is represented by equation (4): In formula (4) For all conductor segment leakage currents, the surface proximity (x) of the midpoint of the conductor segment between nodes i and j (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The sum of soil potentials generated by (x) (i,j) ,y (i,j) ,z (i,j) ) represents the coordinates of the midpoint potential of the conductor segment, r n(i,j) The radius of the cross-section of the conductor segment is... and The leakage current of conductor segment w and the injected negative current of the power source are respectively located in the coordinate (x) (i,j) ,y (i,j) ,z (i,j) -r n(i,j) The soil potential generated at location ) where w is the conductor segment number, n c This represents the total number of conductor segments.

8. The method for diagnosing corrosion of a substation grounding grid according to claim 7, characterized in that, The expression describing the relationship between the leakage current of any conductor segment at nodes i and j of the grounding grid and the ground potential of the grounding grid is represented by (12): Among them, I J1 I represents the current leaking from the exposed portions of conductor segments at nodes i and j. J2 R represents the current leaking from the oxide-covered portion of the conductor segment; y This is the equivalent resistance of the oxide in the conductor segment; This is the potential of the midpoint of the conductor relative to ground. This represents the surface potential of the conductor oxide product relative to ground in this segment; υ (i,j) r represents the coverage of oxidation products in this conductor segment. n(i,j) r is the radius of the remaining central cylinder of the conductor after corrosion. c i is the original cross-sectional radius of the conductor segment; corr It is the natural corrosion current density; E corr It is the natural corrosion potential; β a It is the Tafel slope of the anode; β b Cathode Tafel slope.

9. The expression describing the relationship between the leakage current of any conductor segment at grounding grid nodes i and j and the grounding grid-to-ground potential, as described in claim 8, is characterized in that... The oxide equivalent resistance R of any conductor segment at grounding grid nodes i and j y(i,j) This can be expressed by equation (13): Where L is the length of the conductor; ρ rust α represents the resistivity of the oxidation product. z α is the transfer coefficient. p These are the expansion coefficients, and all three are constants.

10. The expression describing the relationship between the leakage current of any conductor segment at grounding grid nodes i and j and the grounding grid-to-ground potential, as described in claim 9, is characterized in that... Oxidation product coverage υ of any conductor segment (i,j) The value is represented by equation (14), where a o and b o These are the fitting coefficients to be solved: Where L is the length of the conductor; ρ rust α represents the resistivity of the oxidation product. z α is the transfer coefficient. p These are the expansion coefficients, and all three are constants.

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