Substation grounding grid detection method and system

Abstract

A transformer substation grounding grid detection method comprises the following steps: injecting detection current into a grounding grid, and sensing an induced magnetic field generated by the grounding grid above the grounding grid to obtain earth surface magnetic field data; determining a corresponding earth surface position of the grounding grid according to the earth surface magnetic field data; screening the earth surface magnetic field data according to the earth surface corresponding position to obtain to-be-detected data; initializing a covariance matrix optimization strategy; generating a basic population of a covariance matrix optimization strategy according to the to-be-detected data; sampling to generate a new population and calculating fitness; when the fitness meets a preset adaptation condition or the number of iterations reaches the maximum value, ending, otherwise, carrying out optimization and recombination on the basic population by utilizing the new population; and outputting grounding grid depth data according to the iterated basic population. The invention provides a transformer substation grounding grid detection method and system, which can detect the topological structure and the burying depth of a grounding grid on the premise of not excavating the ground.

Description

Technical Field

[0001] The invention relates to the technical field of substation grounding network detection, in particular to a substation grounding network detection method and system. Background Art

[0002] The grounding network of the substation is connected to the grounding wires of the high and low voltage electrical equipment of the whole station, the grounding of the low voltage power system, the cable shielding grounding, the grounding of the communication and computer monitoring system equipment, and some temporary grounding during the maintenance and overhaul of the substation, providing a common reference ground for the connected objects. At the same time, the grounding network has multiple uses such as working grounding, protective grounding, lightning protection and anti-static grounding. The most important thing is that it plays a role in quickly discharging short-circuit current when a power frequency grounding fault or lightning intrusion occurs. It is the fundamental guarantee and important measure to maintain the safe and reliable operation of the substation and ensure the safe operation of personnel and electrical equipment.

[0003] If the grounding resistance of the grounding grid is large, the ground potential may rise abnormally when a grounding fault occurs in the power system or other large current enters the ground; if the grid design of the grounding grid is unreasonable, the grounding system potential may be unevenly distributed, and the local potential may exceed the safety value, which will threaten the safety of the operating personnel. It may also damage the low-voltage or secondary equipment and cable insulation due to counterattack, causing the high-voltage intrusion control and protection system, substation monitoring and protection equipment to malfunction or refuse to operate, thereby bringing huge economic losses and social impacts. With the development of my country's power technology and the application of ultra-high voltage transmission, the requirements for the stability of the substation grounding grid are getting higher and higher. However, the grounding grid itself is a concealed project. After the construction is completed, it is difficult to find the real topological structure of the underground ground grid without large-scale excavation. Operation experience shows that there are serious discrepancies between the actual power grid structure and the construction drawings. There are common problems of random connection and non-construction according to the drawings. In areas with few equipment or relatively unimportant equipment, there are even cases where the grounding grid conductor is missing. Therefore, it is very important to detect the grounding grid during the operation of the substation.

[0004] In the traditional grounding grid handover and acceptance, electrical parameters such as grounding impedance, step voltage, contact voltage, and grounding grid conductivity are generally measured. The lack of a small amount of conductors in the grounding grid has no effect on the grounding impedance. After laying high soil resistivity materials on the surface of the substation, the step voltage and contact voltage are basically unaffected, and the lack of conductors in the grounding grid is basically undetectable; in the grounding grid conductivity test, since the grounding grid is made of copper or flat steel and other materials, the resistivity is very low. If there is no welding leakage, the grounding grid conductivity test result is also within the qualified range. There is currently no mandatory requirement to measure the integrity of the physical topological structure of the grounding grid during handover and acceptance. After the grounding grid is in operation, the existing technology mainly detects corrosion conditions and lacks means to detect the topological structure of the running grounding grid. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a substation grounding grid detection method and system, which can detect the topological structure and buried depth of the grounding grid without excavating the ground.

[0006] In order to achieve the above object, the specific scheme adopted by the present invention is: a substation grounding network detection method, comprising the following steps: A detection current is injected into the grounding grid, and the induced magnetic field generated by the grounding grid is sensed above the grounding grid to obtain surface magnetic field data; Determine the corresponding surface position of the grounding grid according to the surface magnetic field data; The surface magnetic field data is screened according to the corresponding position on the surface to obtain the data to be detected; Initialize the covariance matrix optimization strategy; Generate a basic population of covariance matrix optimization strategy based on the data to be tested; Sampling generates new populations and calculating fitness; The process ends when the fitness meets the preset fitness condition or the number of iterations reaches the maximum value, otherwise the new population is used to optimize the basic population for reorganization; Output the grounding grid depth data based on the iterated basic population.

[0007] As a further optimization of the above-mentioned substation grounding grid detection method: the specific method of injecting a detection current into the grounding grid and sensing the induced magnetic field generated by the grounding grid above the grounding grid includes: Determine the grounding grid entry point, and use the two closest entry points as current entry points; A detection current is injected into the grounding grid through a current access point. The detection current is a sinusoidal alternating current, and the frequency of the detection current is different from the power frequency of the substation. Establish an xyz coordinate system and determine the reference plane based on the surface topography; The magnetic induction intensity receiving device is driven to move in the reference plane, and the magnetic induction intensity receiving device is used to sense the induced magnetic field to obtain the surface magnetic field data.

[0008] As a further optimization of the above-mentioned substation grounding grid detection method: a method for determining the corresponding surface position of the grounding grid according to the surface magnetic field data includes: Screening the surface magnetic field data to extract multiple reference points where the magnetic field intensity exceeds a preset intensity threshold; Perform regional fitting on all reference points to obtain the corresponding surface position of the grounding grid.

[0009] As a further optimization of the above-mentioned substation grounding grid detection method: a method for screening the surface magnetic field data according to the corresponding position on the surface to obtain the data to be detected includes: Perform morphological fitting on the surface magnetic field data to obtain the virtual structure of the grounding grid; Specifying the target position in the ground grid virtual structure; Determine multiple key points in the virtual structure of the grounding grid according to the target orientation; All parts corresponding to key points are selected from the surface magnetic field data to form the data to be detected.

[0010] As a further optimization of the above-mentioned substation grounding grid detection method: when initializing the covariance matrix optimization strategy, the initialization parameters include the population size ε, the number of parent individuals μ, and the recombination weight ω i,...,μ and the maximum number of iterations G, and μ<ε; When generating the basic population of the covariance matrix optimization strategy based on the data to be tested, the population initialization distribution mean is m∈R N , where N = 1, and the initial evolution path is p σ =0.

[0011] As a further optimization of the above-mentioned substation grounding grid detection method: the method of sampling to generate a new population is: in, is the new population generated, N(m,C) is mostly normally distributed, σ is the global standard deviation, and σ∈R + ,λ k is a random variable drawn from a standard normal distribution N(0,I) and serves as the local standard deviation; The calculation method of fitness is: Where h is the depth of the grounding grid.

[0012] As a further optimization of the above-mentioned substation grounding network detection method: the method of using the new population to optimally reorganize the basic population is: After optimizing and reorganizing the basic population with the new population, the covariance matrix and exploration step size are updated; The method to update the covariance matrix is: Among them, c cov is the learning rate of the covariance matrix; The method to update the step size is: d is the dimension of the target space, ||·|| represents the Euclidean norm of the vector, is the gradient of the fitness function.

[0013] A substation grounding network detection system, comprising: A current injection device, used for injecting a detection current into the grounding grid to make the grounding grid generate an induced magnetic field; A magnetic induction intensity receiving device is used to sense the induced magnetic field generated by the grounding grid above the grounding grid to obtain surface magnetic field data; The data processing device is used to determine the surface corresponding position of the grounding grid and the depth data of the grounding grid according to the surface magnetic field data.

[0014] As a further optimization of the above-mentioned substation grounding grid detection system: the magnetic induction intensity receiving device includes: an alternating magnetic field sensor module, which is used to sense the induced magnetic field generated by the grounding grid above the grounding grid to generate an original electrical signal; A signal conditioning circuit module is used to condition the original electrical signal and output an optimized electrical signal; A positioning module, used to determine the spatial position of the magnetic induction intensity receiving device and generate a position signal; A posture sensing module, used to determine the posture of the magnetic induction intensity receiving device and generate a posture signal; The signal acquisition module is used to convert the optimized electrical signal, position signal and posture signal and transmit them to the data processing device.

[0015] Beneficial effects: The present invention can detect the topological structure and burial depth of the grounding grid without excavating the ground, and the detection efficiency is higher; the present invention detects the burial depth of the grounding grid based on the covariance matrix optimization strategy, and the result has high accuracy and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the infinite length wire model of the grounding grid;

[0017] Figure 2 is a flow chart of the detection method of the present invention;

[0018] Figure 3 It is a schematic diagram of the structure of the detection system of the present invention;

[0019] Figure 4 is a schematic diagram of an experimental grounding grid model in a specific implementation manner;

[0020] Figure 5 It is a schematic diagram of experimental results in a specific implementation manner. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] According to engineering experience, the substation grounding grid conductor is usually very long and buried at a shallow depth. The length of the conductor is much larger than other dimensions such as width and height. Therefore, the grounding grid conductor can be approximated as an infinitely long conductor, and then an infinitely long conductor model is established, such as Figure 1 As shown. On this basis, assuming that the conductor is buried at a depth of h and the soil magnetic permeability is μ, an xyz rectangular coordinate system is established with point O on the conductor as the origin of the coordinates. The conductor passes through the x-axis, the current passing through the conductor is I, and point P is a point on the ground with a vertical distance of ρ from the conductor. When current is input into the grounding grid, according to the Biot-Savart law, the magnetic field strength generated by the conductor at point P is:

[0023] The y-direction component B generated by the conductor at point P y (y) is:

[0024] Furthermore, in the actual substation scenario, the buried depth h of the grounding grid conductor and the soil magnetic permeability μ are constants, while the current I passing through the conductor is an unknown quantity. It can be known that By(y) has a maximum value at y=0, that is:

[0025] On the other hand, the substation grounding grid is mostly a mesh structure rather than a single conductor. Therefore, the magnetic field strength at any position above the grounding grid will be affected by many factors, mainly including the magnetic field B1(y) of the grounding grid conductor closest to the position, the magnetic field B2(y) generated by other surrounding conductors at this position, and the magnetic field error B3(y) caused by factors such as sensor error and equipment inclination. The size of B2(y) will vary greatly depending on the structure of the substation grounding grid and the position of the grounding grid conductor.

[0026] In summary, the magnetic field strength at any position above the ground surface of the substation grounding grid measured by the equipment can be expressed as: B Y (y) = k[B1(y)+B2(y)+B3(y)].

[0027] like Figure 2 As shown, based on the above theory, the present invention provides a substation grounding grid detection method, including the following steps S1 to S8.

[0028] S1, injecting a detection current into the grounding grid, and sensing the induced magnetic field generated by the grounding grid above the grounding grid to obtain surface magnetic field data. The specific method includes S11 to S14.

[0029] S11. Determine the introduction point of the grounding grid, and use the two closest introduction points as current access points. By selecting the two closest introduction points as current access points, and using one as the current input point and the other as the current output point, it can be ensured that after the detection current is injected into the grounding grid, the grounding grid has a large constant current, thereby ensuring the accuracy of the final detection result. The grounding grid introduction point is a conductor reserved in advance for measuring the grounding grid during the construction and installation of the grounding grid, which belongs to the prior art in this field and will not be described in detail here.

[0030] S12. Inject a detection current into the grounding grid through a current access point. The detection current is a sinusoidal AC current, and the frequency of the detection current is different from the power frequency of the substation to avoid interference from the power frequency current of the substation.

[0031] S13. Establish an xyz coordinate system and determine a reference plane according to the surface topography, wherein the reference plane is parallel to the surface.

[0032] S14, driving the magnetic induction intensity receiving device to move in the reference plane, and using the magnetic induction intensity receiving device to sense the induced magnetic field to obtain surface magnetic field data. By determining the reference plane and ensuring that the magnetic induction intensity receiving device moves in the reference plane, it is possible to avoid errors in the collected surface magnetic field data caused by changes in the distance between the magnetic induction intensity receiving device and the surface. If necessary, a guide rail or other device can be installed in the reference plane to control the movement process of the magnetic induction intensity receiving device to ensure that the magnetic induction intensity receiving device can stably move in the reference plane.

[0033] After obtaining the surface magnetic field data, the surface magnetic field data is processed by power frequency filtering, notching and amplification, and then the processed surface magnetic field data is subjected to covariance matrix optimization processing to obtain the magnetic field strength at different locations, and a curve chart of the change in magnetic field strength can be drawn.

[0034] S2. Determine the corresponding surface position of the grounding grid according to the surface magnetic field data. The specific method includes S21 to S22.

[0035] S12. Screen the surface magnetic field data and extract multiple reference points where the magnetic field intensity exceeds a preset intensity threshold. As described above, the surface magnetic field data By(y) has a maximum value at y=0. This is because the distance between the magnetic induction intensity receiving device and the grounding grid conductor is the shortest at this position. Therefore, by screening out the part with a sufficiently high magnetic field intensity from the surface magnetic field data, the position of the grounding grid conductor can be determined. More specifically, because the length of the grounding grid conductor is relatively long, a grounding grid conductor can correspond to multiple reference points. The position of the reference point can be determined based on the xyz coordinate system established in S13. All reference points corresponding to a grounding grid conductor are connected, and the position of the grounding grid conductor can be determined by combining the position of the reference plane and the conventional burial depth of the grounding grid.

[0036] S13, performing regional fitting on all reference points to obtain the corresponding surface position of the grounding grid. After obtaining the positions of all grounding grid conductors in the grounding grid, the corresponding surface position of the grounding grid can be combined.

[0037] S3, screening the surface magnetic field data according to the corresponding position on the surface to obtain the data to be detected. The specific method includes S31 to S34.

[0038] S31. Perform morphological fitting on the surface magnetic field data to obtain a virtual structure of the grounding grid.

[0039] S32. Specify a target location in the grounding grid virtual structure.

[0040] S33. Determine a plurality of key points in the virtual structure of the grounding grid according to the target orientation.

[0041] S34. Filter out all parts corresponding to key points from the surface magnetic field data to form data to be detected.

[0042] As described above, because the position of the magnetic induction intensity receiving device relative to the grounding grid will have a great impact on the surface magnetic field data, for a grounding grid conductor, the magnetic field strength on both sides may also be different. In order to avoid introducing sampling errors, the present invention formulates a target orientation based on the virtual structure of the grounding grid in S3, and determines key points based on the target orientation. For a grounding grid conductor, all key points corresponding to it are located on the same side of the grounding grid conductor, thereby ensuring that the data to be detected can more accurately reflect the state of the grounding grid.

[0043] S4. Initialize the covariance matrix optimization strategy. The covariance matrix optimization strategy is a global optimization algorithm based on evolutionary strategy. It uses Gaussian normal distribution to sample in the solution space of the optimization problem, and updates the Gaussian normal distribution through a fitness selection mechanism. The sampling and updating process is continuously iterated until a satisfactory solution is found or the maximum number of sampling times is reached, and then the optimization is stopped to obtain the desired result. The present invention uses a covariance matrix optimization strategy to process the data to be detected, and can obtain an accurate buried depth of the grounding grid. More specifically, when initializing the covariance matrix optimization strategy, the parameters initialized include the population size ε, the number of parent individuals μ, and the recombination weight ω. i,...,μ and the maximum number of iterations G, and μ<ε.

[0044] S5. Generate a basic population of the covariance matrix optimization strategy based on the data to be tested. When generating a basic population of the covariance matrix optimization strategy based on the data to be tested, the population initialization distribution mean is m∈R N , where N = 1, and the initial evolution path is p σ = 0, the global standard deviation is σ∈R + , the covariance matrix C∈R N×N Initialized to the unit matrix I, the iterative algebra g = 0. In the present invention, because the only parameter to be obtained is the buried depth h of the grounding grid, N = 1 can be set.

[0045] S6. Sampling generates a new population and calculates the fitness. The method of sampling to generate a new population is: in, is the new population generated, N(m,C) is mostly normally distributed, σ is the global standard deviation, and σ∈R + ,λ k is a random variable drawn from the standard normal distribution N(0,I) and is the local standard deviation.

[0046] The calculation method of fitness is: Among them, h is the depth of the grounding grid, and y is the position of the grounding grid in the y direction in the xyz coordinate system. Therefore, this fitness calculation function can reflect the correlation between the surface magnetic field data and the corresponding position on the surface. It should also be noted that for the new population It is necessary to comprehensively calculate its fitness, that is, to calculate the fitness of each individual in the new population.

[0047] S7. The process ends when the fitness meets the preset fitness condition or the number of iterations reaches the maximum value. Otherwise, the new population is used to optimize the basic population for reorganization. Specifically, the candidate solutions are sorted according to the fitness, and the μ individuals with the best fitness are selected to update the mean mg+1. The way to update the mean is through weighted summation, and the weighted weight is determined by the reorganization weight ω i It is decided that the method of using the new population to optimally reorganize the basic population is:

[0048] After optimizing and reorganizing the basic population with the new population, the covariance matrix and exploration step size are updated. Specifically, a combination of rank-μ update and rank-1 update is used to adapt to the current search direction and step size.

[0049] The method to update the covariance matrix is: Among them, c cov is the learning rate of the covariance matrix; The method to update the step size is: Where d is the dimension of the target space, ||·|| represents the Euclidean norm of the vector, is the gradient of the fitness function.

[0050] S8. Output grounding grid depth data according to the iterated basic population.

[0051] like Figure 3 As shown, the present invention further provides a substation grounding network detection system, including a current injection device, a magnetic induction intensity receiving device and a data processing device.

[0052] The current injection device is used to inject a detection current into the grounding grid to make the grounding grid generate an induced magnetic field.

[0053] The magnetic induction intensity receiving device is used to sense the induced magnetic field generated by the grounding grid above the grounding grid to obtain surface magnetic field data. The magnetic induction intensity receiving device includes an alternating magnetic field sensor module, a signal conditioning circuit module, a positioning module, a posture sensing module and a signal acquisition module.

[0054] The alternating magnetic field sensor module is used to sense the induced magnetic field generated by the grounding grid above the grounding grid and generate the original electrical signal. The alternating magnetic field sensor module uses three moving coil magnetoelectric sensors to obtain the magnetic field signals in three directions of the location of the magnetic induction intensity receiving device. The sensor skeleton specifications are 18mm inner hole, 60mm outer diameter, and 1mm wall thickness. Copper material with a purity of 99% is selected as the moving coil wire material. The moving coil is wound with 8000 turns, and the wire diameter of each turn is 0.2mm. During the moving coil winding process, it is necessary to ensure that the spacing between each turn is uniform to ensure the uniform distribution of the magnetic field and the accuracy of the sensor.

[0055] The signal conditioning circuit module is used to condition the original electrical signal and output an optimized electrical signal. Figure 2 As shown, the signal conditioning circuit module is connected to the alternating magnetic field sensor module, and is used to perform power frequency trapping, filtering, amplification and other operations on the magnetic field signal obtained by the alternating magnetic field sensor module to eliminate the electromagnetic interference problem of the substation. The signal conditioning circuit consists of three parts: differential signal conversion to single-ended signal, power frequency interference filtering, and signal buffer amplifier circuit. The AD620ARZ chip is used to convert the magnetic field signal obtained by the alternating magnetic field sensor into a single-ended signal, and the power frequency interference signal is filtered out by the OPA2188AIDR chip. Finally, under the action of the amplifier circuit, the output capacity of the signal is improved.

[0056] The positioning module is used to determine the spatial position of the magnetic induction intensity receiving device to generate a position signal. The positioning module adopts UWB (Ultra Wide Band) positioning technology. The positioning module consists of two parts: a base station and a tag. Before the detection begins, the base station needs to be arranged in the substation as a reference coordinate in advance. The tag is built into the magnetic induction intensity receiving device to obtain the real-time coordinates and movement trajectory of the tag during the detection process. The base station uses the STM32F103CBT6 microcontroller as the main control MCU and the DW1000 as the core UWB chip. It has a shell and an external antenna, and a built-in rechargeable lithium battery. It is easy to use, high precision, and compact. The tag uses the STM32F103TBU6 microcontroller as the main control MCU and the DW1000 as the core UWB chip. The onboard PA can effectively resist NLOS interference and increase positioning stability.

[0057] The attitude sensing module is used to determine the attitude of the magnetic induction intensity receiving device and generate an attitude signal. The attitude sensing module uses the WT901C attitude sensor, which is installed in parallel with the magnetic field sensor to ensure that the direction of the magnetic field sensor is consistent with the direction of the device casing, and to ensure that the magnetic field sensor does not have an angle offset during the detection process, thereby reducing data errors caused by changes in the angle of the magnetic field sensor during the detection process. The WT901C attitude sensor integrates motion sensors such as a three-axis gyroscope, a three-axis accelerometer, and a three-axis electronic compass. It can accurately output the current attitude of the module in a dynamic environment, with an attitude measurement accuracy of 0.2°. The integrated three-axis gyroscope can automatically calibrate the current attitude angle of the sensor so that it is always consistent with the direction of the device casing.

[0058] The signal acquisition module is used to convert the optimized electrical signal, position signal and attitude signal and transmit them to the data processing device. The signal acquisition module collects attitude angle signals, magnetic field signals and UWB positioning signals, and coordinates the transmission of data streams between modules. Its data format is a signed 16-bit integer, the sampling rate is 20480KSa / s, the single sampling data volume is 40kb, and the data transmission frequency is 40kb / s. The synchronous processing, caching and output of data are realized. The signal acquisition module can be connected to the data processing device through a USB output module.

[0059] The data processing device is used to determine the corresponding surface position of the grounding grid and the depth data of the grounding grid according to the surface magnetic field data. The data processing device can be a common computer.

[0060] Finally, in order to verify the present invention, the following experiment was designed.

[0061] like Figure 4 As shown in the figure, the main body of the simulated grounding grid in this experiment is a square of 8m×8m, with a grid spacing of 4m and an original design burial depth of 0.74m. Two wires with a total length of about 30m are connected to the output port of the current injection device, and the surface return lead is led back from the periphery of the grounding grid, as far away from the measurement area as possible to avoid affecting the measurement.

[0062] Place the magnetic induction intensity receiving device above the rectangular loop, keep the coil plane parallel to the conductor, and adjust the current injection device to output current of 1A. Then, at the same height, translate the magnetic induction intensity receiving device and keep the coil plane direction unchanged. Some of the data measured when determining the location of the BC segment grounding grid conductor are shown in Table 1 and Figure 5 shown.

[0063] Table 1 BC section grounding grid conductor position and burial depth judgment data table

[0064] According to Table 1 and Figure 5 It can be known that when y=0, the measured magnetic field intensity reaches the maximum value. Therefore, it can be judged that the BC section grounding grid conductor is located on the coordinate axis of y=0, and then, the buried depth of the grounding grid conductor is 0.74m. Comparing the actual buried depth of the BC section grounding grid conductor of the laboratory simulation grounding grid, the inspection is consistent with the actual situation.

[0065] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A substation grounding network detection method, characterized in that: The steps include: A detection current is injected into the grounding grid, and the induced magnetic field generated by the grounding grid is sensed above the grounding grid to obtain surface magnetic field data; Determine the corresponding surface position of the grounding grid according to the surface magnetic field data; The surface magnetic field data is screened according to the corresponding position on the surface to obtain the data to be detected; Initialize the covariance matrix optimization strategy; Generate a basic population of covariance matrix optimization strategy based on the data to be tested; Sampling generates new populations and calculating fitness; The process ends when the fitness meets the preset fitness condition or the number of iterations reaches the maximum value, otherwise the new population is used to optimize the basic population for reorganization; Output the grounding grid depth data based on the iterated basic population.

2. A substation grounding grid detection method as claimed in claim 1, characterized in that: The specific method of injecting the detection current into the grounding grid and sensing the induced magnetic field generated by the grounding grid above the grounding grid includes: Determine the grounding grid entry point, and use the two closest entry points as current entry points; A detection current is injected into the grounding grid through a current access point. The detection current is a sinusoidal AC current, and the frequency of the detection current is different from the power frequency of the substation. Establish an xyz coordinate system and determine the reference plane based on the surface topography; The magnetic induction intensity receiving device is driven to move in the reference plane, and the magnetic induction intensity receiving device is used to sense the induced magnetic field to obtain the surface magnetic field data.

3. A substation grounding grid detection method according to claim 1, characterized in that: The method for determining the corresponding surface position of the grounding grid according to the surface magnetic field data includes: Screening the surface magnetic field data to extract multiple reference points where the magnetic field intensity exceeds a preset intensity threshold; Perform regional fitting on all reference points to obtain the corresponding surface position of the grounding grid.

4. A substation grounding grid detection method according to claim 1, characterized in that: The method of screening the surface magnetic field data according to the corresponding position on the surface to obtain the data to be detected includes: Perform morphological fitting on the surface magnetic field data to obtain the virtual structure of the grounding grid; Specifying the target position in the ground grid virtual structure; Determine multiple key points in the virtual structure of the grounding grid according to the target orientation; All parts corresponding to key points are selected from the surface magnetic field data to form the data to be detected.

5. A substation grounding grid detection method according to claim 1, characterized in that: When initializing the covariance matrix optimization strategy, the initialization parameters include population size ε, number of parent individuals μ, and recombination weight ω i,...,μ and the maximum number of iterations G, and μ<ε; When generating the basic population of the covariance matrix optimization strategy based on the data to be tested, the population initialization distribution mean is m∈R N , where N = 1, and the initial evolution path is p σ =0.

6. A substation grounding grid detection method as claimed in claim 5, characterized in that: The method of sampling to generate a new population is: in, is the new population generated, N(m,C) is mostly normally distributed, σ is the global standard deviation, and σ∈R + ,λ k is a random variable drawn from the standard normal distribution N(0,I) and serves as the local standard deviation; The calculation method of fitness is: Where h is the depth of the grounding grid.

7. A substation grounding grid detection method according to claim 1, characterized in that: The method of using the new population to optimally reorganize the basic population is:

8. A substation grounding grid detection method as claimed in claim 7, characterized in that: After optimizing and reorganizing the basic population with the new population, the covariance matrix and exploration step size are updated; The method to update the covariance matrix is: Among them, c cov is the learning rate of the covariance matrix; The method to update the step size is: Where d is the dimension of the target space, ||·|| represents the Euclidean norm of the vector, is the gradient of the fitness function.

9. A substation grounding network detection system, characterized in that: include: A current injection device, used for injecting a detection current into the grounding grid to cause the grounding grid to generate an induced magnetic field; A magnetic induction intensity receiving device is used to sense the induced magnetic field generated by the grounding grid above the grounding grid to obtain surface magnetic field data; The data processing device is used to determine the surface corresponding position of the grounding grid and the depth data of the grounding grid according to the surface magnetic field data.

10. A substation grounding grid detection system as claimed in claim 9, characterized in that: The magnetic induction intensity receiving device comprises: The alternating magnetic field sensor module is used to sense the induced magnetic field generated by the grounding grid above the grounding grid and generate an original electrical signal; A signal conditioning circuit module is used to condition the original electrical signal and output an optimized electrical signal; A positioning module, used to determine the spatial position of the magnetic induction intensity receiving device and generate a position signal; A posture sensing module, used to determine the posture of the magnetic induction intensity receiving device and generate a posture signal; The signal acquisition module is used to convert the optimized electrical signal, position signal and posture signal and transmit them to the data processing device.

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