A corrosion detection method and device for substation grounding grid

Abstract

The present invention discloses a corrosion detection method and device for a substation grounding grid, and belongs to the technical field of power equipment detection. The corrosion detection method for the substation grounding grid generates each branch resistance increment according to each branch current and the node resistance increment, and calculates the node corrosion parameter according to the node resistance increment and the scattered current charge of the corresponding grounding down conductor. The two groups of measurement points with the smallest node corrosion parameters are taken as the second reference points, and an AC source is connected between the second reference points or between the measurement points to generate an environmental magnetic field gain and a magnetic field gain to be measured. The present invention determines the corroded branch based on the environmental magnetic field gain, the magnetic field gain to be measured and the branch resistance increment, reduces the influence of the substation environmental magnetic field on the detection result, and improves the accuracy of corrosion prediction.

Description

Technical Field

[0001] The present invention relates to the technical field of power equipment detection, and in particular to a corrosion detection method and device for a substation grounding grid. Background Art

[0002] The grounding grid is very important for ensuring the safe operation of the substation. Corrosion will weaken the conductive performance of the grounding grid and reduce its reliability. China Patent Publication No. CN110320238A discloses a grounding grid corrosion state detection circuit and a grounding grid corrosion state monitoring method. The method first measures the resistance and natural corrosion potential between the electrodes, then measures the voltage between the reference electrode and the research electrode and the current between the auxiliary electrode and the research electrode, and compares the average, maximum and minimum values ​​of the grounding resistance, the maximum step voltage and the maximum contact voltage with the corresponding design parameters to determine the grounding grid corrosion. The grounding grid resistance is greatly affected by the environment, and the grounding grid corrosion cannot be accurately estimated by the resistance alone. China Patent Publication No. CN118112371A discloses a grounding grid corrosion diagnosis method combining electrical impedance imaging and electromagnetic methods. The method injects sinusoidal alternating current of different frequencies into the grounding grid through the grounding lead, calculates the magnetic induction intensity in the horizontal direction of the induced magnetic field, and determines the grounding grid topology diagram according to the spatial distribution of the magnetic induction intensity in the horizontal direction. Then, the impedance diagram of the grounding grid is reconstructed in combination with the resistivity measurement method to complete the corrosion positioning diagnosis of the grounding grid branch. In the actual working environment, the substation generates an environmental magnetic field, and the magnetic field of the corroded branch is affected by the environmental magnetic field, which affects the judgment of the corrosion situation. Summary of the invention

[0003] In order to solve the defects of the above-mentioned prior art, the present invention proposes a corrosion detection method and device for a substation grounding grid, which adjusts the corrosion amount of the branch to be tested based on the environmental magnetic field gain of some branches, reduces the influence of the substation environmental magnetic field on the detection results, and improves the accuracy of corrosion prediction.

[0004] The technical solution of the present invention is achieved in this way:

[0005] A method for detecting corrosion of a substation grounding grid comprises the following steps:

[0006] Step 1: The grounding grid has M groups of branches. A nominal resistance matrix is ​​generated according to the nominal resistance of each branch. Adjacent branches intersect at N groups of nodes. K groups of nodes connected to the grounding down conductors of the substation are measurement points.

[0007] Step 2: Calibrate the measurement point x and the measurement point y as the first reference point, connect a DC source between the two sets of first reference points, generate a current direction matrix, generate a branch current matrix based on the nominal resistance matrix and the current direction matrix, and collect the first reference resistance r between the first reference points. 1xy, x≤K, y≤K;

[0008] Step 3: When the corrosion branch needs to be detected, a DC source is connected between the two sets of first reference points to collect the second reference resistance r between the first reference points. 2xy , calculate the node resistance increment r 3xy , based on the branch current matrix, the node resistance increment r is generated 3xy The measurement equation of

[0009] Step 4: Recalibrate the first reference point and connect the DC source to obtain the measurement equations of multiple sets of node resistance increments, and solve the branch resistance increment r according to the measurement equations. 3m , m≤M;

[0010] Step 5: Collect the ground current of each grounding conductor, generate the scattered charge of the grounding conductor according to the ground current at multiple moments, and calculate the node resistance increment r 3xy and the corresponding grounding down conductor scattered charge calculation node corrosion parameter q xy ;

[0011] Step 6: Calibrate the two groups of measurement points with the smallest node corrosion parameters as the second reference points, connect an AC source between the second reference points, and generate an environmental magnetic field gain g 1 ;

[0012] Step 7: Extract at least one group of branches whose branch resistance increment is greater than the first threshold, extract two groups of measurement points connected to the branches, connect an AC source between the two groups of measurement points, and generate a magnetic field gain g to be measured. 2 ;

[0013] Step 8: Based on the ambient magnetic field gain g 1 , the magnetic field gain to be measured g 2 And the branch resistance increment r 3m Identify the corroded branch.

[0014] In the present invention, in step 2, the branch admittance matrix is ​​calculated according to the nominal resistance matrix, the node admittance matrix and the branch voltage matrix are calculated according to the branch admittance matrix and the current direction matrix, and the branch current matrix is ​​calculated according to the branch admittance matrix and the branch voltage matrix.

[0015] In the present invention, in step 3, r 3xy =r 2xy -r 1xy , the measurement equation includes any branch resistance increment r 3m The node resistance increment r 3xy relationship.

[0016] In the present invention, in step 5, the scattered current charge of the grounding down conductor corresponding to the measuring point k is ,ikt ' is the grounding current of the grounding down conductor at time t, T is the detection time, k≤K.

[0017] In the present invention, the node corrosion parameter , Q x Q is the stray charge of the grounding conductor corresponding to the measuring point x, y It is the stray charge of the grounding down conductor corresponding to the measuring point y.

[0018] In the present invention, in step 6, the nominal magnetic induction intensity is calculated according to the multiple branch resistance increments between the second reference points, the measured magnetic induction intensity between the second reference points is collected, and the environmental magnetic field gain is calculated based on the measured magnetic induction intensity and the nominal magnetic induction intensity.

[0019] In the present invention, the branch d corresponding to the minimum branch resistance increment between the second reference points is extracted, the first measurement point is set according to the branch d, and the effective current i of the branch is calculated. d , nominal magnetic induction intensity , L 1 is the distance between the first measuring point and branch d, L 2 is the length of the branch, μ is the spatial magnetic permeability, and the measured magnetic induction intensity b at the first measuring point is collected. 2 , ambient magnetic field gain g 1 =b 2 / b 1 .

[0020] In the present invention, in step 8, the branch corrosion parameter z of branch m is m = r 3m g 1 / g 2 , branch corrosion parameter z m When it is greater than the second threshold, branch m is a corroded branch.

[0021] A corrosion detection device for implementing the corrosion detection method of the substation grounding grid, comprising:

[0022] A grounding grid;

[0023] K groups of grounding down conductors are connected to K groups of measuring points of the grounding grid respectively;

[0024] A monitoring unit, used for collecting the grounding current of each grounding down conductor;

[0025] A DC source connected to the first reference point of the ground grid;

[0026] A measuring unit, configured to collect a first reference resistance and a second reference resistance between a first reference point;

[0027] A first analysis unit, used for calculating the branch resistance increment of each branch;

[0028] A second analysis unit, used for calculating node corrosion parameters and extracting a second reference point;

[0029] AC source, connected to the second reference point of the ground grid;

[0030] A magnetic induction unit, used for measuring the environmental magnetic field gain of the second reference point and the magnetic field gain to be measured at the measuring point;

[0031] The data output unit is used to output the corrosion branch according to the environmental magnetic field gain, the magnetic field gain to be measured and the branch resistance increment.

[0032] In the present invention, the magnetic induction unit includes two sets of mutually perpendicular induction coils, the magnetic field component is calculated according to the induced voltage of each induction coil, and the measured magnetic induction intensity is obtained according to the two sets of magnetic field components.

[0033] The corrosion detection method and device for the substation grounding grid implemented in the present invention have the following beneficial effects: the present invention generates the resistance increment of each branch according to the current of each branch and the node resistance increment. The branch resistance increment reflects the reduction of the branch's conductive performance, and then combines the change of the branch's induced magnetic field to judge the corrosion situation. Furthermore, the environmental magnetic field gain of the second reference point is used as a reference, and the measured magnetic field gain of the corroded branch is combined to predict the corrosion amount, thereby reducing the influence of the substation environmental magnetic field on the detection results. The present invention calibrates the second reference point with low corrosion through the grounding current of the grounding down conductor, thereby improving the accuracy of the prediction of the corroded branch. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of a substation grounding grid;

[0035] Figure 2 is a schematic diagram of an equivalent circuit of a grounding grid;

[0036] Figure 3 It is a flow chart of the corrosion detection method of the substation grounding grid of the present invention;

[0037] Figure 4 A schematic diagram of the present invention connecting a DC source at a first reference point;

[0038] Figure 5 A schematic diagram of the grounding current of the grounding down conductor of the present invention;

[0039] Figure 6 A schematic diagram of the present invention connecting an AC source to a second reference point;

[0040] Figure 7 It is a schematic diagram of measuring the branch magnetic induction intensity of the present invention;

[0041] Figure 8A block diagram of a corrosion detection device for realizing the corrosion detection method for a substation grounding grid according to the present invention;

[0042] Fig. 9 Schematic diagram of the magnetic induction unit of the present invention.

[0043] Reference numerals in the accompanying drawings: substation equipment 100 , earth 200 , grounding grid 300 , branch 311 , corroded branch 312 , measuring point 321 , non-measuring point 322 , grounding down conductor 400 . DETAILED DESCRIPTION

[0044] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0045] like Figure 1 and Figure 2 As shown, the substation has multiple groups of substation equipment 100. The grounding grid 300 of the substation is buried in the earth 200. The grounding grid 300 has multiple groups of branches 311. Adjacent branches 311 are connected to each other through nodes. Some nodes are connected to the substation equipment 100 through grounding down conductors 400. These nodes can be measured and are called measurement points 321. Some nodes are completely buried underground and are called non-measurement points 322. The grounding current of the substation equipment 100 enters the grounding grid through the measurement point 321, and then disperses into the earth through other nodes and branches. The measurement point 321 introduces the grounding current for a long time and is an important node for corrosion measurement. The effective diameter of the corroded branch 312 is reduced, and the corresponding resistance is increased. When studying the circuit state of the grounding grid, the branch of the grounding grid is equivalent to a resistor, the measurement point 321 is equivalent to a current injection end, and the earth 200 is regarded as an insulator. The substation equipment 100 of the substation generates an environmental magnetic field, which affects the prediction of the corrosion branch. The present invention adjusts the corrosion amount of the branch to be tested based on the environmental magnetic field gain of some branches, thereby reducing the influence of the environmental magnetic field of the substation on the detection result. Embodiment 1

[0046] like Figures 3 to 7 As shown, a corrosion detection method for a substation grounding grid of the present invention comprises the following steps:

[0047] Step 1: The grounding grid has M groups of branches. A nominal resistance matrix is ​​generated based on the nominal resistance of each branch. Adjacent branches intersect at N groups of nodes. K groups of nodes connected to the substation grounding conductor are measurement points. The nominal resistance is the design resistance of the branch. The nominal resistance can be calculated based on the size and resistivity of the branch. Due to the existence of the grounding conductor, voltage and current signals can be collected from the measurement point to obtain the resistance status of each branch.

[0048] Step 2: Calibrate the measurement point x and the measurement point y as the first reference point, connect a DC source between the two sets of first reference points, generate a current direction matrix, generate a branch current matrix based on the nominal resistance matrix and the current direction matrix, and collect the first reference resistance r between the first reference points. 1xy , x≤K, y≤K. x≠y, the injected current of the DC source is i 0 . This embodiment uses an electrical network method to calculate the branch current matrix. Specifically, the branch admittance matrix is ​​calculated based on the nominal resistance matrix, and then the node admittance matrix and the branch voltage matrix are calculated based on the branch admittance matrix and the current direction matrix, and the branch current matrix is ​​calculated based on the branch admittance matrix and the branch voltage matrix. Please refer to Example 2 for details. In a further embodiment, the circuit simulation method can also be used to calculate the branch current matrix, which is not limited by the present invention.

[0049] Step 3: When the corrosion branch needs to be detected, a DC source is connected between the two sets of first reference points to collect the second reference resistance r between the first reference points. 2xy , calculate the node resistance increment r 3xy , based on the branch current matrix, the node resistance increment r is generated 3xy The measurement equation of r 3xy =r 2xy -r 1xy After the grounding grid is put into operation, the corrosion of some branches exceeds the limit and becomes a corroded branch. A DC source is connected between two sets of first reference points. The corresponding second reference resistance is greater than the first reference resistance. The difference between the second reference resistance and the first reference resistance can be used to reverse the branch resistance increment.

[0050] Step 4: Recalibrate the first reference point and connect the DC source to obtain the measurement equations of multiple sets of node resistance increments, and solve the branch resistance increment r according to the measurement equations. 3m , m≤M. Specifically, when building a grounding network, different first reference points are calibrated to obtain multiple sets of first reference resistances, and the corresponding branch current matrix is ​​calculated. After the grounding network is put into operation, different first reference points are calibrated to obtain multiple sets of second reference resistances. The measurement equation contains any branch resistance increment r 3m The node resistance increment r 3xy The relationship between 3xy =f(r 31 , r 32 ,...,r 3m ,..., r 3M ). K groups of measurement points can generate K×(K-1) combinations of first reference points, corresponding to K×(K-1) groups of measurement equations. When the unknown quantity is less than or equal to K×(K-1), the branch resistance increment can be solved directly. When the unknown quantity is greater than K×(K-1), the optimal solution of the branch resistance increment can be approximated by the minimum norm.

[0051] Step 5: Collect the ground current of each grounding conductor, generate the scattered charge of the grounding conductor according to the ground current at multiple moments, and calculate the node resistance increment r 3xy and the corresponding grounding down conductor scattered charge calculation node corrosion parameter q xy After the grounding grid is put into operation, the grounding current of the substation equipment is injected into the grounding grid through the grounding down conductor. The measurement point k corresponds to the scattered current charge of the grounding down conductor. ,i kt ' is the grounding current of the grounding down conductor at time t, T is the detection time, k≤K. The detection time is, for example, the substation operation time calculated from the last maintenance time. Node corrosion parameters , Q x Q is the stray charge of the grounding conductor corresponding to the measuring point x, y is the stray charge of the grounding conductor corresponding to the measuring point y. The smaller the grounding current is, the shorter the duration is, and the smaller the stray charge is. The smaller the stray charge is, the smaller the node corrosion parameter is.

[0052] Step 6: Calibrate the two groups of measurement points with the smallest node corrosion parameters as the second reference points, connect an AC source between the second reference points, and generate an environmental magnetic field gain g 1 The nominal magnetic induction intensity is calculated based on the increment of multiple branch resistances between the second reference points. The nominal magnetic induction intensity is the theoretical magnetic induction intensity after connecting to the AC source. The measured magnetic induction intensity between the second reference points is collected, and the environmental magnetic field gain is calculated based on the measured magnetic induction intensity and the nominal magnetic induction intensity.

[0053] Specifically, the branch d corresponding to the minimum branch resistance increment between the second reference points is extracted, and the first measurement point is set according to the branch d. The method of step 2 is used to determine the node resistance increment at this time using the voltmeter and the ammeter, and the effective current i of the branch is calculated using the effective current injected by the AC source. d , nominal magnetic induction intensity , L 1 is the distance between the first measuring point and branch d, L 2 is the length of the branch, μ is the spatial magnetic permeability, and the measured magnetic induction intensity b at the first measuring point is collected. 2 , ambient magnetic field gain g 1 =b 2 / b 1 Usually the magnetic field gain is ≤1. The magnetic field gain can also be used to characterize the reduction in the effective diameter of the branch. The closer the magnetic field gain is to 0, the greater the branch corrosion.

[0054] Step 7: Extract at least one group of branches whose branch resistance increment is greater than the first threshold, extract two groups of measurement points connected to the branches, connect an AC source between the two groups of measurement points, and generate a magnetic field gain g to be measured. 2The first threshold is, for example, 1.75 to 4 times the nominal resistance. Referring to the method described in step 6, the corresponding second measurement point is first determined according to the position of the branch, the theoretical nominal magnetic induction intensity of the second measurement point is calculated, and then the actual measured magnetic induction intensity is measured, and finally the magnetic field gain to be measured is generated.

[0055] Step 8: Based on the ambient magnetic field gain g 1 , the magnetic field gain to be measured g 2 And the branch resistance increment r 3m Determine the corroded branch. Branch corrosion parameter z of branch m m =r 3m g 1 / g 2 , the magnetic field gain is inversely correlated with the amount of corrosion. Branch corrosion parameter z m When it is greater than the second threshold, branch m is a corroded branch. The branch corrosion parameter determined by the present invention through two types of corrosion characterization quantities can better reflect the actual corrosion situation of the actual branch. The branch corrosion parameter is the product of the two types of corrosion characterization quantities, and the second threshold is, for example, 1.5 to 16 times the nominal resistance. Embodiment 2

[0056] This embodiment discloses a preferred method for calculating the branch resistance increment.

[0057] When building a grounding grid, the branch admittance matrix is ​​calculated based on the nominal resistance matrix. 1 =[r 11 ,r 12 ,...,r 1m ,...,r 1M ] T , r 1m is the nominal resistance of branch m. The branch admittance matrix is ​​an M×M matrix, whose diagonal elements are the inverses of the corresponding nominal resistances. .

[0058] Calculate the node admittance matrix Y 2 = A·Y 1 ·A T The calibration measurement point x and the measurement point y are used as the first reference points, and a DC source is connected between the two sets of first reference points to generate a current direction matrix. The reference directions can be defined from north to south and from east to west. , The current direction matrix A expresses the topological relationship of the grounding grid, that is, the correlation matrix of the grounding grid. T is the transposed matrix of A.

[0059] Generate a current injection matrix based on the injection direction of the DC source, and then calculate the branch voltage matrix based on the node admittance matrix and the current injection matrix. The branch voltage matrix = Y2 -1 B. Current injection matrix B = [b 1 ,b 2 ,...,b n ,...,b N ] T , the current injection matrix expresses the injection direction and magnitude of the current, where .

[0060] The branch current matrix is ​​calculated based on the branch admittance matrix and the branch voltage matrix. 2 = Y 1 ·A T ·(Y 2 -1 B). Among them, I 2 =[i 11 ,i 12 ,...,i 1m ,...,i 1M ] T ,i 1m is the branch current of branch m.

[0061] The first reference points are connected to a first measuring unit, and the first measuring unit collects a first reference resistance r between the first reference points. 1xy The first measuring unit of this embodiment may be composed of an ammeter and a voltmeter, and calculates the first reference resistance according to Ohm's law.

[0062] After the grounding grid is put into operation, some branches of the grounding grid are corroded, and the corrosion causes the resistance of any branch to increase. A DC source is connected between the two sets of first reference points to collect the second reference resistance r between the first reference points. 2xy , the second reference resistance is greater than the first reference resistance. Calculate the node resistance increment r 3xy , r 3xy =r 2xy -r 1xy .

[0063] Generate node resistance increment r based on branch current matrix 3xy The measurement equation includes any branch resistance increment r 3m The node resistance increment r 3xy The relationship between 3xy =f(r 31 , r 32 ,...,r 3m ,..., r 3M ). Specifically, according to the KCL and LVL laws, the branch resistance increment r 3m The node resistance increment r 3xy The relationship is: ,i 1m is the element value of the branch current matrix when building the grounding network, i 2m is the element value of the current branch current matrix, i 0 is the injected current of the DC source. 3xy 、i 1m 、i 0 is a known quantity, i 2m and r 3m Is an unknown quantity.

[0064] Recalibrate different measurement points as the first reference point to obtain multiple sets of node resistance increment measurement equations. When the number of measurement equations is greater than or equal to M×M, the branch resistance increment r can be solved. 3m In a more specific embodiment, if the number of measurement equations is less than M×M, the branch resistance increment can be solved by using methods such as Tikhonov regularization and minimum norm. Further, when the nodes at both ends of m are measurement points, the branch current can be measured. At this time, i 2m It is also a known quantity, which can be used to reduce the number of unknown quantities and improve the accuracy of the solution. Embodiment 3

[0065] Reference Figure 7 , this embodiment further discloses a preferred method for calculating the environmental magnetic field gain.

[0066] The two groups of measurement points with the smallest node corrosion parameters are used as the second reference points, and an AC source is connected between the second reference points. The AC source is, for example, a sinusoidal AC signal. The smaller the node corrosion parameter, the smaller the ground current of the grounding down conductor corresponding to the measurement point, the smaller the possibility of corrosion, and it can be used as a reference for the environmental interference magnetic field.

[0067] Extract the corresponding branch d with the minimum branch resistance increment between the second reference points, d≤M, and set the first measurement point according to branch d. The smaller the branch resistance increment, the less likely it is to be corroded. When there are multiple branches between the second reference points, select the current path with the smallest series resistance and extract the corresponding branch d with the minimum branch resistance increment in the current path. The first measurement point is located at the intersection of the perpendicular bisector of branch d and the earth.

[0068] Calculate the effective current i of this branch d The effective injection current of the AC source is collected, and the branch current matrix can be obtained by combining the method of the second embodiment, and the effective current i of branch d in the branch current matrix is ​​extracted. d .

[0069] Nominal magnetic induction intensity b at the first measuring point 1 =μi d cosθ / (2πL 1 ), .therefore , L 1 is the distance between the first measuring point and branch d, L 2 is the length of the branch, and μ is the spatial magnetic permeability.

[0070] Collect the measured magnetic induction intensity b at the first measuring point 2 , the magnetic field generated by branch d is perpendicular to the current direction of branch d. The present invention can measure two sets of magnetic field components b perpendicular to branch d 21 and b 22 , measure magnetic induction intensity .

[0071] Further, at least one group of branches whose branch resistance increment is greater than the first threshold value is extracted, and two groups of measurement points connected to the branch are extracted. Specifically, the current path where the branch is located is first determined, and the measurement points on the current path are searched one by one. When the branch is connected to multiple groups of current paths, the current path with the smallest series resistance is selected, and then the measurement points on both sides of the branch are searched one by one along the current path. Embodiment 4

[0072] like Figure 8 and Fig. 9 A corrosion detection device for implementing the corrosion detection method of the substation grounding grid of the present invention includes: a grounding grid, K groups of grounding down conductors, a monitoring unit, a DC source, a measuring unit, a first analysis unit, a second analysis unit, an AC source, a magnetic induction unit, a data output unit and a database.

[0073] K groups of grounding down conductors are respectively connected to K groups of measuring points of the grounding grid. The monitoring unit is used to collect the grounding current of each grounding down conductor. The monitoring unit generates a timing signal of the grounding current. A DC source is connected to the first reference point of the grounding grid, and the DC source generates a DC signal. The injection current of the DC source is, for example, 0.1A. The measuring unit is used to collect the first reference resistance and the second reference resistance between the first reference point. In this embodiment, the measuring unit is composed of an ammeter and a voltmeter. The first analysis unit is used to calculate the branch resistance increment of each branch. The second analysis unit is used to calculate the node corrosion parameter and extract the second reference point. The AC source is connected to the second reference point of the grounding grid. In order to facilitate calculation, the AC source generates a sinusoidal AC signal. The injection current of the AC source is, for example, 0.5A. The magnetic induction unit is used to measure the environmental magnetic field gain of the second reference point and the magnetic field gain to be measured at the measuring point. The data output unit is used to output the corroded branch according to the environmental magnetic field gain, the magnetic field gain to be measured and the branch resistance increment. The database is used to store the topology of the grounding grid and the nominal resistance of each branch.

[0074] According to the right-hand rule, the magnetic field generated by the corrosion branch is in the magnetic field plane perpendicular to the branch direction. The magnetic induction unit includes two sets of mutually perpendicular induction coils. The magnetic field components are calculated based on the induced voltage of each induction coil. The two sets of magnetic field components are mutually perpendicular and located in the magnetic field plane. The measured magnetic induction intensity is obtained based on the two sets of magnetic field components. This method can reduce the influence of the magnetic field in other branch directions. Furthermore, the induction coil is equivalent to an RLC equivalent circuit composed of its own distributed capacitance, coil resistance, and parasitic inductance. The magnetic field excites an induced electromotive force in the induction coil, and the induced electromotive force is proportional to the magnetic induction intensity. The magnetic induction unit also includes a signal acquisition unit and a signal analysis unit connected to the induction coil. The signal acquisition unit acquires the induced electromotive force of the induction coil, and the signal analysis unit calculates the magnetic induction intensity based on the induced electromotive force of the two induction coils.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting corrosion of a substation grounding grid, characterized in that: The following steps are involved: Step 1: The grounding grid has M groups of branches. A nominal resistance matrix is ​​generated according to the nominal resistance of each branch. Adjacent branches intersect at N groups of nodes. K groups of nodes connected to the grounding down conductors of the substation are measurement points. Step 2: Calibrate the measurement point x and the measurement point y as the first reference point, connect a DC source between the two sets of first reference points, generate a current direction matrix, generate a branch current matrix based on the nominal resistance matrix and the current direction matrix, and collect the first reference resistance r between the first reference points. 1xy , x≤K, y≤K; Step 3: When the corrosion branch needs to be detected, a DC source is connected between the two sets of first reference points to collect the second reference resistance r between the first reference points. 2xy , calculate the node resistance increment r 3xy , based on the branch current matrix, the node resistance increment r is generated 3xy The measurement equation of Step 4: Recalibrate the first reference point and connect the DC source to obtain the measurement equations of multiple sets of node resistance increments, and solve the branch resistance increment r according to the measurement equations. 3m , m≤M; Step 5: Collect the ground current of each grounding conductor, generate the scattered charge of the grounding conductor according to the ground current at multiple moments, and calculate the node resistance increment r 3xy and the corresponding grounding down conductor scattered charge calculation node corrosion parameter q xy , where the measurement point k corresponds to the stray charge of the grounding down conductor ,i kt ' is the grounding current of the grounding down conductor at time t, T is the detection time, k≤K, node corrosion parameter , Q x Q is the stray charge of the grounding conductor corresponding to the measuring point x, y The stray charge of the grounding down conductor corresponding to the measuring point y; Step 6: Calibrate the two groups of measurement points with the smallest node corrosion parameters as the second reference points, connect the AC source between the second reference points, generate the environmental magnetic field gain g1, wherein the nominal magnetic induction intensity is calculated according to the multiple branch resistance increments between the second reference points, collect the measured magnetic induction intensity between the second reference points, calculate the environmental magnetic field gain based on the measured magnetic induction intensity and the nominal magnetic induction intensity, extract the corresponding branch d with the smallest branch resistance increment between the second reference points, set the first measurement point according to the branch d, and calculate the effective current i of the branch d , nominal magnetic induction intensity , L1 is the distance between the first measuring point and the branch d, L2 is the length of the branch, μ is the spatial magnetic permeability, the measured magnetic induction intensity b2 of the first measuring point is collected, and the environmental magnetic field gain g1=b2 / b1; Step 7: extract at least one group of branches whose branch resistance increment is greater than the first threshold, extract two groups of measurement points connected to the branches, connect an AC source between the two groups of measurement points, and generate a magnetic field gain g2 to be measured; Step 8: Based on the environmental magnetic field gain g1, the magnetic field gain to be measured g2 and the branch resistance increment r 3m Calculate the branch corrosion parameter z of branch m m = r 3m g1 / g2 to determine the corrosion branch.

2. The corrosion detection method for substation grounding grid according to claim 1 is characterized in that: The branch admittance matrix is ​​calculated according to the nominal resistance matrix, and then the node admittance matrix and the branch voltage matrix are calculated according to the branch admittance matrix and the current direction matrix, and the branch current matrix is ​​calculated according to the branch admittance matrix and the branch voltage matrix.

3. The corrosion detection method for substation grounding grid according to claim 1 is characterized in that: In step 3, r 3xy =r 2xy -r 1xy , the measurement equation includes any branch resistance increment r 3m The node resistance increment r 3xy relationship.

4. The corrosion detection method for substation grounding grid according to claim 1, characterized in that: In step 8, the branch corrosion parameter z m When it is greater than the second threshold, branch m is a corroded branch.

5. A corrosion detection device for implementing the corrosion detection method for substation grounding grid according to claim 1, characterized in that: include: A grounding grid; K groups of grounding down conductors are connected to K groups of measuring points of the grounding grid respectively; A monitoring unit, used for collecting the grounding current of each grounding down conductor; A DC source connected to the first reference point of the ground grid; A measuring unit, configured to collect a first reference resistance and a second reference resistance between a first reference point; A first analysis unit, used for calculating the branch resistance increment of each branch; A second analysis unit, used for calculating node corrosion parameters and extracting a second reference point; AC source, connected to the second reference point of the ground grid; A magnetic induction unit, used for measuring the environmental magnetic field gain of the second reference point and the magnetic field gain to be measured at the measuring point; The data output unit is used to output the corrosion branch according to the environmental magnetic field gain, the magnetic field gain to be measured and the branch resistance increment.

6. The corrosion detection device according to claim 5, characterized in that: The magnetic induction unit includes two sets of mutually perpendicular induction coils. The magnetic field component is calculated according to the induced voltage of each induction coil, and the measured magnetic induction intensity is obtained according to the two sets of magnetic field components.

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