Grounding grid state evaluation and three-dimensional visualization method based on historical data comparison

Abstract

The invention discloses a grounding grid state evaluation and three-dimensional visualization method based on historical data comparison. The method comprises the following steps: step 1, intelligent acquisition of key parameters of a grounding grid: carrying out online monitoring and data acquisition on grounding impedance, contact potential difference and step potential difference parameters; 2, carrying out on-line monitoring and data acquisition on the conductivity of the grounding grid; step 3, performing comparison by adopting a fuzzy analytic hierarchy process and combining conductivity monitoring data between grounding grids in an access area, local grounding grid corrosion state monitoring data and grounding grid operation state monitoring historical data to realize grounding grid state comprehensive evaluation; step 4, establishing a grounding grid three-dimensional model and performing three-dimensional visualization by combining the plurality of key parameter detection values measured in the step 1 and the step 2 and the safety evaluation result obtained in the step 3; according to the method, the reasonable safety state of the grounding grid can be accurately expressed, and the real spatial position of the grounding system can be intuitively expressed.

Description

Technical Field

[0001] The present invention relates to the technical field of grounding grids, and in particular to a grounding grid state evaluation and three-dimensional visualization method based on historical data comparison. Background Art

[0002] The grounding grid is an important guarantee for the substation to protect the safety of the power system. Its main function is to provide a channel for the fault current to disperse. The grounding performance of a grounding grid is directly related to the personal safety of the staff in the power plant and the safe operation of various electrical equipment. The grounding grid system is a general term for a grounding body composed of multiple metal grounding electrodes buried at a certain depth underground and connected by conductors to form a mesh structure. Grounding grids are large and small, some are very complex and large, and some are composed of only one grounding electrode. They are usually designed according to needs. In hydropower stations and substations, a special underground grounding body and steel bars in the house are welded together to form a grounding grid. All electrical equipment casings and the neutral point of the transformer are connected to this network. According to the design requirements and actual layout, the grounding grid often presents a complex and criss-cross distribution in the underground space.

[0003] The grounding parameter measurements of the existing grounding system include grounding impedance, contact potential difference, step potential difference, grounding grid conductivity, grounding grid corrosion status, etc. The above grounding parameter measurements all require an external test power supply and are tested using the three-pole test principle. Affected by factors such as the test power supply and wiring path selection, there is no mature online monitoring technology for grounding grid grounding parameter measurements. Accurately evaluating the status of the grounding grid is the key to ensuring the safe and stable operation of the power system. At present, there are two main methods for evaluating the safety of the grounding grid: one is a rough calculation through empirical formulas, and the second is a precise calculation and evaluation through numerical calculation methods. Both methods use a single characteristic parameter to compare with the specified threshold. There is no complete evaluation method for whether the operating status of the grounding grid is good. It is difficult to accurately express the reasonable safety status of the grounding grid by setting the classification based on engineering experience alone.

[0004] At the same time, in the traditional two-dimensional grounding grid distribution map, the expression and management of the grounding grid and its related facilities are only carried out by combining two-dimensional point and line symbols. A large number of grounding conductors are crowded together, and different types cannot be clearly displayed on the two-dimensional grounding grid distribution map, resulting in poor readability, unclear topological logic, and difficulty in further expansion and analysis. In addition, there are some grounding conductors that are large in curvature and even perpendicular to the ground. In the two-dimensional map, this type of equipment can only be expressed as point marks with text descriptions on the map, and the real spatial position of the grounding system cannot be intuitively expressed. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a grounding grid status evaluation and three-dimensional visualization method based on historical data comparison to solve the problems raised in the background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a grounding grid status evaluation and three-dimensional visualization method based on historical data comparison, comprising the following steps:

[0007] Step 1: Intelligently collect key parameters of the grounding grid: including online monitoring and data collection of grounding impedance, contact potential difference, and step potential difference parameters;

[0008] Step 2: Online monitoring and data collection of grounding grid conductivity;

[0009] Step 3: Use fuzzy hierarchical analysis method to compare the conductivity monitoring data between the access area ground grids, the local ground grid corrosion status monitoring data and the ground grid operation status monitoring historical data to achieve a comprehensive assessment of the ground grid status;

[0010] Step 4: Based on the key parameter test values ​​measured in steps 1 and 2 and the safety assessment results obtained in step 3, a three-dimensional model of the grounding grid is established and visualized in three dimensions.

[0011] Preferably, the step 1 specifically includes the following process:

[0012] The three-pole test principle is used to intelligently collect ground impedance. The ground impedance is used to test the power supply and return current poles, and an electrical model of the grounding grid of a large hydropower station is built. The contact potential difference and step potential difference of the risk area are calculated. At the same time, areas with higher potential differences are selected, and voltage difference sensors are arranged in three directions to monitor the potential difference online in high-risk areas.

[0013] The current I flows in from the grounding device E and flows back from the auxiliary current electrode C to form a closed loop. The test resistance is derived by electrostatic theory:

[0014]

[0015] In the formula, is the actual grounding resistance of the grounding device; is the mutual resistance between auxiliary voltage and current electrodes; is the mutual resistance between the grounding device and the auxiliary voltage pole; is the mutual resistance between the grounding device and the auxiliary current electrode, where ρ is the resistivity, S PC is the auxiliary voltage and current inter-electrode radius, S EP S is the radius between the grounding device and the auxiliary voltage pole, EC is the radius between the grounding device and the auxiliary current electrode, and r is the actual radius of the grounding device.

[0016] Preferably, the step 2 specifically includes the following process: the grounding grid of the hydropower station is divided into the following five parts: (1) the dam body grounding grid; (2) the diversion tunnel grounding grid; (3) the underground plant grounding grid; (4) the outgoing line field / switch station grounding grid; (5) various tunnel grounding grids within the hub; therefore, the monitoring of the conductivity of the hydropower station grounding grid is divided into the following multiple parts of the grounding system The reliability of multiple grounding points within the same part of the grounding system; according to the field investigation and actual measurement of the hydropower station grounding system, a reliable grounding point is selected as the reference point for the conductivity test, and the area with poor conductivity and the important equipment area are selected as the monitoring area, and voltage poles are pre-buried at the reference point and the monitoring point, and a different frequency power supply is used as the test power supply to regularly monitor the conductivity of the grounding system; when measuring, first determine a grounding lead of a device that is well connected to the main grounding grid as the reference point, and then measure the DC resistance between the grounding part of the surrounding electrical equipment and the reference point; if the conductivity test results of more measured points and the reference point are poor, it is advisable to consider replacing the reference point and re-measuring.

[0017] Preferably, the step three specifically includes the following process:

[0018] Step 3.1: Divide the evaluation results of the grounding grid into five levels: very safe - unsafe - safe - relatively unsafe - unsafe; the corresponding scores and specific descriptions of each level are as follows:

[0019] (1) Very safe (85-100): indicates that the grounding grid is in good condition and all performance indicators are almost unchanged;

[0020] (2) Safer (70-85): Indicates that the grounding grid is currently in good operating condition. Some grounding conductors may be slightly corroded. The electrical performance of the grounding grid is slightly reduced. The possibility of failure is low, and the maintenance period can be appropriately extended.

[0021] (3) Safe (60-70): Indicates that the grounding grid is operating safely. Some key electrical performance indicators may increase significantly, but are still within safety limits. The grounding conductor may be moderately corroded. Regular maintenance of the grounding grid should be ensured.

[0022] (4) Less safe (40-60): This indicates that the grounding grid has a high safety risk in operation. Due to long operation years or harsh operating environment, the conductor corrosion is serious and some key electrical performance indicators have declined significantly. The key electrical parameters should be retested in time to further confirm the safety status. If there is indeed a high safety risk, rectification and maintenance should be carried out.

[0023] (5) Unsafe (<40): This indicates that the grounding grid has a high safety risk in operation. The key electrical performance of the grounding grid has been greatly reduced. The grounding conductor may have been seriously corroded. When the ground current is high, there is a high possibility of safety accidents. The grounding grid should be rectified and repaired.

[0024] Step 3.2: According to the historical data and online data obtained by monitoring in step 1 and step 2, the comprehensive evaluation parameters of the grounding grid status are determined as follows: grounding impedance Z, on-resistance R, step voltage Us, and contact voltage UT; then, the judgment matrix of the key parameters for the safety status evaluation of the grounding grid is constructed by combining the initial value and the measured value, and the consistency test of the judgment matrix is ​​performed to obtain the eigenvector corresponding to the maximum eigenvalue of the judgment matrix, and the eigenvector is normalized to obtain the weight of each key parameter for the status evaluation. Finally, the weight of the key parameters for the safety status evaluation of the grounding grid is determined by the hierarchical analysis method; the score items of each factor can be calculated according to the following formula:

[0025] P i =100K(CM) / (CO)

[0026] Where:

[0027] O——initial value;

[0028] C——safety limit;

[0029] M——measurement value;

[0030] K – weight;

[0031] After obtaining the total score of the grounding grid status assessment, the safety level is divided according to the total score P, which can directly give the level of the assessed grounding grid status and provide a basis for grounding grid fault diagnosis;

[0032]

[0033] More preferably, the specific operation process of step 3.2 is as follows:

[0034] Step 1: Establish a pairwise comparison matrix A of each parameter, whose eigenvector is the corresponding weight of each parameter. The four parameters in the matrix A are: contact voltage, step voltage, ground impedance, and on-resistance. Establish a pairwise comparison matrix of the four parameters;

[0035] The second step is to compare and judge the advantages and disadvantages of the evaluation schemes. For the four parameters, the five schemes are set up in pairs. B1, B2, B3, and B4 are the comparison matrices of the five schemes under contact voltage, step voltage, ground impedance, and on-resistance respectively. The meaning of the B matrix is ​​that its eigenvector represents the advantages and disadvantages of the five schemes for a certain parameter.

[0036] The third step is to find the weight coefficients of each parameter, that is, to find the values ​​of the unknowns in the A matrix; first set the initial values: x = 1, y = 1, a = 1, b = 1, c = 1, d = 1, and get the A and B matrices. Then, according to the following formula, find the eigenvectors of A and B1, B2, B3, B4:

[0037]

[0038] Let the eigenvector of A be U', and the eigenvectors of B1, B2, B3, and B4 be ω(B1), ω(B2), ω(B3), ω(B4), ω(B5);

[0039] The score is calculated as follows:

[0040]

[0041] Since Scheme I is the original data of the hydropower station, that is, the best case of various data indicators measured under the same conditions, its final score, that is, P1, is 100 points; Schemes II, III, IV and V are respectively based on the 110kV hydropower station, and a single data exceeds the standard, so their scores are no more than 60 points, which is taken as 60 here; according to this theory, the elements in the matrix A and B1, B2, B3, B4 are modified in turn, and finally P1≈100, P2≈60, P3≈60, P4≈60, P5≈60 are made. After calculating x and y in the A matrix, the eigenvector of the A matrix can be obtained, that is, the weight of each parameter can be obtained;

[0042] The fourth step is to obtain the scores of various parameters measured on site; given the optimal value and national standard limit of each parameter, the optimal value of each parameter can be set as 100 points, and the national standard limit can be set as 60 points. For each parameter, the linear relationship between the score and the parameter value can be calculated. The score is regarded as y, and the initial measurement value and the national standard value are regarded as x. Then, according to the binary linear formula, the linear coefficients a and b of each parameter can be calculated;

[0043] y=ax+b

[0044] After knowing the linear coefficients a and b of each parameter, the actual measured parameter values ​​can be substituted into the formula to calculate the scores of each measured parameter;

[0045] The fifth step is to obtain the overall status of the grounding grid. According to the weights of each parameter obtained in the third step and the scores of the individual parameters obtained in the fourth step, the scores of each parameter are multiplied by their respective weights to obtain a comprehensive score, and the current status of the hydropower station can be calculated. In order to make the displayed results more obvious, the status of the grounding grid is divided into four levels according to "unqualified, serious, general, and good".

[0046] Since the results of field measurement data vary greatly, the software sets an overflow algorithm based on the characteristics of the grounding grid; the overflow algorithm is expressed as follows: compare the relationship between each indicator and the standard value separately. If one item exceeds the standard, no comprehensive evaluation will be performed, and the exceeded parameters will be displayed in the output opinion, and the grounding grid status will be prompted to be unqualified; when the indicators do not exceed the standard, compare the relationship between each indicator and the initial measurement value of the hydropower station. If one item is better than the initial measurement value, the parameter will be full marks.

[0047] Preferably, the step 4 specifically includes the following process:

[0048] First, the layout parameters of the grounding grid are obtained, including the type of grounding material, material specifications, grounding grid design drawings, height offset, and XY spacing of the grounding grid. Then, based on the obtained grounding grid design drawings and layout parameters, the grounding grid is modeled using 3D modeling software. In the modeling process, the geometric shape of the grounding grid, material properties, and the location and connection method of the grounding electrode are considered.

[0049] Draw the linear layout of the grounding grid area according to the parameters and generate a three-dimensional model of the grounding grid, including a horizontal grounding body model, a vertical grounding body model, a grounding element model, and a grounding grid scene model;

[0050] Add grounding electrode: arrange grounding electrodes on the generated three-dimensional model of the grounding grid, generate real-time grounding electrode parameters, calculate and generate grounding calculation report according to the layout parameters of the grounding grid and the grounding electrode parameters, including contact voltage, allowable value of step voltage, maximum contact potential difference, maximum step potential difference, contact potential, step potential and thermal stability verification value;

[0051] Finally, add the grounding trunk line: draw the grounding trunk line on the three-dimensional model of the grounding grid with grounding electrodes, generate a three-dimensional grounding trunk line model, and connect the equipment to the grounding trunk line;

[0052] Based on the grounding grid design data, the 3D model of each component of the grounding conductor is constructed through the mainstream 3D modeling algorithm or software system, and the grounding grid information display platform is constructed using spatial geographic information technology and 3D visualization technology to realize the visualization and interaction of the 3D model of the grounding grid system. At the same time, it is compatible with the conductivity monitoring data between the access area ground grids, the local ground grid corrosion status monitoring data and the grounding grid operation status monitoring historical data and applies them to the 3D visualization scene to realize the 3D visualization comprehensive display of the grounding grid;

[0053] The grounding grid information display platform can intuitively display the layout, connection method and relationship between the grounding grid and other equipment.

[0054] Beneficial effects of the present invention:

[0055] 1. Based on the measured test values ​​of all parameters such as grounding impedance, contact potential difference, step potential difference, and grounding grid conductivity of the hydropower station since its initial construction, the present invention proposes a grounding grid status evaluation and three-dimensional visualization method based on historical data comparison; it can accurately express the reasonable safety status of the grounding grid, intuitively show the real spatial position of the grounding system, and further ensure the safe and stable operation of power station equipment and facilities and the personal safety of personnel.

[0056] 2. The three-dimensional grounding network management mode has a unique advantage in dealing with the shortcomings of the two-dimensional management mode mentioned above. By performing three-dimensional visualization operations on the grounding system data, the buried grounding conductors and related equipment are displayed to users in the form of three-dimensional models, and users can have an intuitive understanding of the complex spatial distribution of the underground grounding network. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The figure is a flow chart of a grounding grid status evaluation and three-dimensional visualization method based on historical data comparison. DETAILED DESCRIPTION

[0058] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0059] Example 1: Figure 1 As shown, a grounding grid status evaluation and three-dimensional visualization method based on historical data comparison includes the following steps:

[0060] Step 1: Intelligent collection of key parameters of the grounding grid, including grounding impedance, contact potential difference, step potential difference and other parameters, for online monitoring and data collection. The three-pole test principle is used to intelligently collect grounding impedance. The specific method is to install a different frequency test power supply between the online system equipment in the hydropower station as an online monitoring power supply for grounding impedance. The diagonal length D of the hydropower station grounding grid is generally several thousand meters, and the geographical location of the power station is mountainous. The present invention adopts a short-distance wiring method to measure and correct the grounding impedance, and the pole line length is about 1D~2D, and the current pole and voltage maximum angle wiring method are adopted. Similarly, an external test power supply can only collect the contact potential difference and step potential difference, and the grounding impedance test power supply and the return current pole are used to build an electrical model of the grounding grid of a large hydropower station, and the contact potential difference and step potential difference of the risk area are calculated. At the same time, the area with higher potential difference is selected, and the voltage difference sensor is arranged in three directions to monitor the potential difference online in the high-risk area. Since the current line wiring is short, there is a certain deviation between the return current and the actual test current. The present invention will also use simulation calculations to propose a correction method for the contact potential difference and step potential difference monitoring results.

[0061] In this step, the current I flows in from the grounding device E and flows back from the auxiliary current electrode C to form a closed loop. The test resistance is derived by electrostatic theory:

[0062]

[0063] In the formula, is the actual grounding resistance of the grounding device; is the mutual resistance between auxiliary voltage and current electrodes; is the mutual resistance between the grounding device and the auxiliary voltage pole; is the mutual resistance between the grounding device and the auxiliary current electrode, where ρ is the resistivity, S PC is the auxiliary voltage and current inter-electrode radius, S EP S is the radius between the grounding device and the auxiliary voltage pole, EC is the radius between the grounding device and the auxiliary current electrode, and r is the actual radius of the grounding device.

[0064] Step 2: Online monitoring and data collection of the grounding grid conductivity. Generally, the grounding grid of a hydropower station can be divided into the following five parts: (1) dam body grounding grid; (2) diversion tunnel grounding grid; (3) underground powerhouse grounding grid; (4) outgoing line field / switch station grounding grid; (5) various tunnel grounding grids within the hub. Therefore, the monitoring of the grounding grid conductivity of a hydropower station can be divided into the following multiple parts of the grounding system conductivity test and the reliability of multiple grounding points within the same grounding system. According to the field survey and actual measurement of the grounding system of the hydropower station, a reliable grounding point is selected as the reference point for the conductivity test, and the area with poor conductivity and the important equipment area are selected as the monitoring area. The voltage pole is pre-buried at the reference point and the monitoring point, and the different frequency power supply is used as the test power supply to regularly monitor the conductivity of the grounding system. When measuring, first determine a grounding lead of a device that is well connected to the main grounding grid as the reference point, and then measure the DC resistance between the grounding part of the surrounding electrical equipment and the reference point; if the conductivity test results of many measured points and the reference point are poor, it is advisable to consider replacing the reference point and re-measure.

[0065] Step 3: Use the fuzzy hierarchical analysis method to conduct a comprehensive assessment of the grounding grid status by combining the conductivity monitoring data between the grounding grids in the access area, the local grounding grid corrosion status monitoring data, and the grounding grid operation status monitoring historical data. First, the assessment results of the grounding grid status are divided into five levels: very safe, unsafe, etc. The corresponding scores and specific descriptions of each level are as follows:

[0066] (1) Very safe (85-100): indicates that the grounding grid is in good condition and all performance indicators are almost unchanged;

[0067] (2) Safer (70-85): Indicates that the grounding grid is currently in good operating condition. Some grounding conductors may be slightly corroded. The electrical performance of the grounding grid is slightly reduced. The possibility of failure is low, and the maintenance period can be appropriately extended.

[0068] (3) Safe (60-70): Indicates that the grounding grid is operating safely. Some key electrical performance indicators may increase significantly, but are still within safety limits. The grounding conductor may be moderately corroded. Regular maintenance of the grounding grid should be ensured.

[0069] (4) Less safe (40-60): This indicates that the grounding grid has a high safety risk in operation. Due to long operation years or harsh operating environment, the conductor corrosion is serious and some key electrical performance indicators have declined significantly. The key electrical parameters should be retested in time to further confirm the safety status. If there is indeed a high safety risk, rectification and maintenance should be carried out.

[0070] (5) Unsafe (<40): This indicates that the grounding grid has a high safety risk in its operation. The key electrical performance of the grounding grid has been greatly reduced. The grounding conductor may have been seriously corroded. When the ground current is high, there is a high possibility of safety accidents. The grounding grid should be rectified and repaired.

[0071] According to the historical data and online data obtained by monitoring in step one and step two, the comprehensive evaluation parameters of the grounding grid status can be determined as follows: grounding impedance Z, on-resistance R, step voltage Us, and contact voltage UT; then, the initial value and the measured value are combined to construct a judgment matrix of key parameters for the safety status assessment of the grounding grid, and the consistency of the judgment matrix is ​​tested. The eigenvector corresponding to the maximum eigenvalue of the judgment matrix is ​​obtained and the eigenvector is normalized to obtain the weight of each key parameter for the status assessment. Finally, the weight of the key parameter for the safety status assessment of the grounding grid is determined by the hierarchical analysis method (AHP). The score items of each factor can be calculated according to the following formula:

[0072] P i =100K(CM) / (CO) (1)

[0073] Where:

[0074] O——initial value;

[0075] C——safety limit;

[0076] M——measurement value;

[0077] K – weight.

[0078] After obtaining the total score of the grounding grid status assessment, the safety level is divided according to the total score S, which can directly give the level of the assessed grounding grid condition and provide a basis for grounding grid fault diagnosis.

[0079]

[0080] The specific operation process is as follows:

[0081] Step 1: Establish a pairwise comparison matrix A of each parameter, whose eigenvector is the corresponding weight of each parameter. The four parameters in the matrix A are: contact voltage, step voltage, ground impedance, and on-resistance. Establish a pairwise comparison matrix of the four parameters;

[0082] The second step is to compare and judge the advantages and disadvantages of the evaluation schemes. For the four parameters, the five schemes are set up in pairs. B1, B2, B3, and B4 are the comparison matrices of the five schemes under contact voltage, step voltage, ground impedance, and on-resistance, respectively. The meaning of the B matrix is ​​that its eigenvector represents the advantages and disadvantages of the five schemes for a certain parameter;

[0083] The third step is to find the weight coefficients of each parameter, that is, to find the values ​​of the unknowns in the A matrix; first set the initial values: x = 1, y = 1, a = 1, b = 1, c = 1, d = 1, and get the A and B matrices. Then, according to the following formula, find the eigenvectors of A and B1, B2, B3, B4:

[0084]

[0085] Let the eigenvector of A be U', and the eigenvectors of B1, B2, B3, and B4 be ω(B1), ω(B2), ω(B3), ω(B4), ω(B5);

[0086] The score is calculated as follows:

[0087]

[0088] Since Scheme I is the original data of the hydropower station, that is, the best case of various data indicators measured under the same conditions, its final score, that is, P1, is 100 points; Schemes II, III, IV and V are respectively based on the 110kV hydropower station, and a single data exceeds the standard, so their scores are no more than 60 points, which is taken as 60 here; according to this theory, the elements in the matrix A and B1, B2, B3, B4 are modified in turn, and finally P1≈100, P2≈60, P3≈60, P4≈60, P5≈60 are made. After calculating x and y in the A matrix, the eigenvector of the A matrix can be obtained, that is, the weight of each parameter can be obtained;

[0089] The fourth step is to obtain the scores of various parameters measured on site; given the optimal value (initial measurement value) and national standard limit value of each parameter, the optimal value of each parameter can be set as 100 points, and the national standard limit value can be set as 60 points. For each parameter, the linear relationship between the score and the parameter value can be calculated. The score is regarded as y, and the initial measurement value and the national standard value are regarded as x. Then, according to the binary linear formula, the linear coefficients a and b of each parameter can be calculated;

[0090] y=ax+b

[0091] After knowing the linear coefficients a and b of each parameter, the actual measured parameter values ​​can be substituted into the formula to calculate the scores of each measured parameter;

[0092] The fifth step is to obtain the overall status of the grounding grid; according to the weights of each parameter obtained in the third step and the scores of the individual parameters obtained in the fourth step, multiply the scores of each parameter by their respective weights to obtain a comprehensive score, and then the current status of the hydropower station can be calculated; in order to make the displayed results more obvious, the status of the grounding grid is divided into four levels according to "unqualified, serious, general, and good".

[0093] Since the results of field measurement data vary greatly, the software sets an overflow algorithm based on the characteristics of the grounding grid; the overflow algorithm is expressed as follows: compare the relationship between each indicator and the standard value separately. If one item exceeds the standard, no comprehensive evaluation will be performed, and the exceeded parameters will be displayed in the output opinion, and the grounding grid status will be prompted to be unqualified; when the indicators do not exceed the standard, compare the relationship between each indicator and the initial measurement value of the hydropower station. If one item is better than the initial measurement value (that is, the value is smaller), then the parameter is full marks.

[0094] Step 4: Combine the key parameter test values ​​measured in steps 1 and 2 and the safety assessment results obtained in step 3 to establish a three-dimensional model of the grounding grid and conduct a preliminary visual assessment. The specific method is to first obtain the layout parameters of the grounding grid: including the type of grounding material, material specifications, grounding grid design drawings, height offset and grounding grid XY spacing, etc., and then use the three-dimensional modeling software to model the grounding grid based on the obtained grounding grid design drawings and layout parameters. In the modeling process, factors such as the geometry of the grounding grid, material properties, and the location and connection method of the grounding electrode need to be considered. According to the parameters, the linear layout of the grounding grid area is drawn to generate a three-dimensional model of the grounding grid, including a horizontal grounding body model, a vertical grounding body model, a grounding element model, a grounding grid scene model, etc.; further, grounding electrodes are added: grounding electrodes are arranged on the generated three-dimensional model of the grounding grid, and real-time grounding electrode parameters are generated. According to the layout parameters of the grounding grid and the grounding electrode parameters, a grounding calculation report is calculated and generated, including contact voltage, allowable value of step voltage, maximum contact potential difference, maximum step potential difference, contact potential, step potential and thermal stability verification value, etc.; finally, a grounding trunk line is added: a grounding trunk line is drawn on the three-dimensional model of the grounding grid with grounding electrodes arranged thereon, a three-dimensional grounding trunk line model is generated, and the equipment is connected to the grounding trunk line. Based on the grounding grid design data, the three-dimensional model of each component of the grounding conductor is constructed through the mainstream three-dimensional modeling algorithm or software system, and the grounding grid information display platform is constructed using spatial geographic information technology, three-dimensional visualization technology, etc. to realize the visualization and interaction of the three-dimensional model of the grounding grid system. At the same time, it is compatible with the conductivity monitoring data between the access area ground grids, the local ground grid corrosion status monitoring data, and the grounding grid operation status monitoring historical data and other related data, and can be applied to the three-dimensional visualization scene to realize the three-dimensional visualization of the grounding grid. The grounding grid information display platform can intuitively display the layout of the grounding grid, the connection method and the relationship with other equipment.

[0095] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A grounding grid status evaluation and three-dimensional visualization method based on historical data comparison, characterized in that: The following steps are involved: Step 1: Intelligently collect key parameters of the grounding grid: including online monitoring and data collection of grounding impedance, contact potential difference, and step potential difference parameters; Step 2: Online monitoring and data collection of grounding grid conductivity; Step 3: Use fuzzy hierarchical analysis method to compare the conductivity monitoring data between the access area ground grids, the local ground grid corrosion status monitoring data and the ground grid operation status monitoring historical data to achieve a comprehensive assessment of the ground grid status; Step 4: Based on the key parameter test values ​​measured in steps 1 and 2 and the safety assessment results obtained in step 3, a three-dimensional model of the grounding grid is established and visualized in three dimensions.

2. The method for evaluating and three-dimensionally visualizing grounding grid status based on historical data comparison according to claim 1 is characterized in that: The step 1 specifically includes the following process: The three-pole test principle is used to intelligently collect ground impedance. The ground impedance is used to test the power supply and return current poles, and an electrical model of the grounding grid of a large hydropower station is built. The contact potential difference and step potential difference of the risk area are calculated. At the same time, areas with higher potential differences are selected, and voltage difference sensors are arranged in three directions to monitor the potential difference online in high-risk areas. The current I flows in from the grounding device E and flows back from the auxiliary current electrode C to form a closed loop. The test resistance is derived by electrostatic theory: In the formula, is the actual grounding resistance of the grounding device; is the mutual resistance between auxiliary voltage and current electrodes; is the mutual resistance between the grounding device and the auxiliary voltage pole; is the mutual resistance between the grounding device and the auxiliary current electrode, where ρ is the resistivity, S PC is the auxiliary voltage and current inter-electrode radius, S EP S is the radius between the grounding device and the auxiliary voltage pole, EC is the radius between the grounding device and the auxiliary current electrode, and r is the actual radius of the grounding device.

3. The method for evaluating and three-dimensionally visualizing grounding grid status based on historical data comparison according to claim 1 is characterized in that: The step 2 specifically includes the following processes: the grounding grid of the hydropower station is divided into the following five parts: (1) the dam body grounding grid; (2) the diversion tunnel grounding grid; (3) the underground plant grounding grid; (4) the outgoing line field / switch station grounding grid; (5) various tunnel grounding grids within the hub; therefore, the monitoring of the conductivity of the hydropower station grounding grid is divided into the following multiple parts: the conductivity test between the grounding systems and the reliability of multiple grounding points within the same part of the grounding system; according to the field investigation and actual measurement of the hydropower station grounding system, a reliable grounding point is selected as the reference point for the conductivity test, and the area with poor conductivity and the important equipment area are selected as the monitoring area, and voltage poles are pre-buried at the reference point and the monitoring point, and a heterodyne power supply is used as the test power supply to regularly monitor the conductivity of the grounding system; when measuring, first determine a grounding lead of a device that is well connected to the main grounding grid as the reference point, and then measure the DC resistance between the grounding part of the surrounding electrical equipment and the reference point; if the conductivity test results of more measured points and the reference point are poor, it is advisable to consider replacing the reference point and re-measuring.

4. The method for evaluating and three-dimensionally visualizing grounding grid status based on historical data comparison according to claim 1 is characterized in that: The step three specifically includes the following process: Step 3.1: Divide the evaluation results of the grounding grid into five levels: very safe - unsafe - safe - relatively unsafe - unsafe; the corresponding scores and specific descriptions of each level are as follows: (1) Very safe (85-100): indicates that the grounding grid is in good condition and all performance indicators are almost unchanged; (2) Safer (70-85): Indicates that the grounding grid is currently in good operating condition. Some grounding conductors may be slightly corroded. The electrical performance of the grounding grid is slightly reduced. The possibility of failure is low, and the maintenance period can be appropriately extended. (3) Safe (60-70): Indicates that the grounding grid is operating safely. Some key electrical performance indicators may increase significantly, but are still within safety limits. The grounding conductor may be moderately corroded. Regular maintenance of the grounding grid should be ensured. (4) Less safe (40-60): This indicates that the grounding grid has a high safety risk in operation. Due to long operation years or harsh operating environment, the conductor corrosion is serious and some key electrical performance indicators have declined significantly. The key electrical parameters should be retested in time to further confirm the safety status. If there is indeed a high safety risk, rectification and maintenance should be carried out. (5) Unsafe (<40): This indicates that the grounding grid has a high safety risk in operation. The key electrical performance of the grounding grid has been greatly reduced. The grounding conductor may have been seriously corroded. When the ground current is high, there is a high possibility of safety accidents. The grounding grid should be rectified and repaired. Step 3.2: According to the historical data and online data obtained by monitoring in step 1 and step 2, the comprehensive evaluation parameters of the grounding grid status are determined as follows: grounding impedance Z, on-resistance R, step voltage Us, and contact voltage UT; then, the judgment matrix of the key parameters for the safety status evaluation of the grounding grid is constructed by combining the initial value and the measured value, and the consistency test of the judgment matrix is ​​performed to obtain the eigenvector corresponding to the maximum eigenvalue of the judgment matrix, and the eigenvector is normalized to obtain the weight of each key parameter for the status evaluation. Finally, the weight of the key parameters for the safety status evaluation of the grounding grid is determined by the hierarchical analysis method; the score items of each factor can be calculated according to the following formula: P i =100K(C-M) / (C-O) Where: O——initial value; C——safety limit; M——measurement value; K – weight; After obtaining the total score of the grounding grid status assessment, the safety level is divided according to the total score P, which can directly give the level of the assessed grounding grid status and provide a basis for grounding grid fault diagnosis; 5. The method for grounding grid status evaluation and three-dimensional visualization based on historical data comparison according to claim 4 is characterized in that: The specific operation process of step 3.2 is as follows: Step 1: Establish a pairwise comparison matrix A of each parameter, whose eigenvector is the corresponding weight of each parameter. The four parameters in the matrix A are: contact voltage, step voltage, ground impedance, and on-resistance. Establish a pairwise comparison matrix of the four parameters; The second step is to compare and judge the advantages and disadvantages of the evaluation schemes. For the four parameters, the five schemes are set up in pairs. B1, B2, B3, and B4 are the comparison matrices of the five schemes under contact voltage, step voltage, ground impedance, and on-resistance respectively. The meaning of the B matrix is ​​that its eigenvector represents the advantages and disadvantages of the five schemes for a certain parameter. The third step is to find the weight coefficients of each parameter, that is, to find the values ​​of the unknowns in the A matrix; first set the initial values: x = 1, y = 1, a = 1, b = 1, c = 1, d = 1, and get the A and B matrices. Then, according to the following formula, find the eigenvectors of A and B1, B2, B3, B4: Let the eigenvector of A be U', and the eigenvectors of B1, B2, B3, and B4 be ω(B1), ω(B2), ω(B3), ω(B4), ω(B5); The score is calculated as follows: Since Scheme I is the original data of the hydropower station, that is, the best case of various data indicators measured under the same conditions, its final score, that is, P1, is 100 points; Schemes II, III, IV and V are respectively based on the 110kV hydropower station, and a single data exceeds the standard, so their scores are no more than 60 points, which is taken as 60 here; according to this theory, the elements in the matrix A and B1, B2, B3, B4 are modified in turn, and finally P1≈100, P2≈60, P3≈60, P4≈60, P5≈60 are made. After calculating x and y in the A matrix, the eigenvector of the A matrix can be obtained, that is, the weight of each parameter can be obtained; The fourth step is to obtain the scores of various parameters measured on site; given the optimal value and national standard limit of each parameter, the optimal value of each parameter can be set as 100 points, and the national standard limit can be set as 60 points. For each parameter, the linear relationship between the score and the parameter value can be calculated. The score is regarded as y, and the initial measurement value and the national standard value are regarded as x. Then, according to the binary linear formula, the linear coefficients a and b of each parameter can be calculated; y=ax+b After knowing the linear coefficients a and b of each parameter, the actual measured parameter values ​​can be substituted into the formula to calculate the scores of each measured parameter; The fifth step is to obtain the overall status of the grounding grid. According to the weights of each parameter obtained in the third step and the scores of the individual parameters obtained in the fourth step, the scores of each parameter are multiplied by their respective weights to obtain a comprehensive score, and the current status of the hydropower station can be calculated. In order to make the displayed results more obvious, the status of the grounding grid is divided into four levels according to "unqualified, serious, general, and good"; Since the results of field measurement data vary greatly, the software sets an overflow algorithm based on the characteristics of the grounding grid; the overflow algorithm is expressed as follows: compare the relationship between each indicator and the standard value separately. If one item exceeds the standard, no comprehensive evaluation will be performed, and the exceeded parameters will be displayed in the output opinion, and the grounding grid status will be prompted to be unqualified; when the indicators do not exceed the standard, compare the relationship between each indicator and the initial measurement value of the hydropower station. If one item is better than the initial measurement value, the parameter will be full marks.

6. The method for evaluating and three-dimensionally visualizing grounding grid status based on historical data comparison according to claim 1 is characterized in that: The step 4 specifically includes the following process: First, the layout parameters of the grounding grid are obtained, including the type of grounding material, material specifications, grounding grid design drawings, height offset, and XY spacing of the grounding grid. Then, based on the obtained grounding grid design drawings and layout parameters, the grounding grid is modeled using 3D modeling software. In the modeling process, factors such as the geometry of the grounding grid, material properties, and the location and connection of the grounding electrodes are considered; Draw the linear layout of the grounding grid area according to the parameters and generate a three-dimensional model of the grounding grid, including a horizontal grounding body model, a vertical grounding body model, a grounding element model, and a grounding grid scene model; Add grounding electrode: arrange grounding electrodes on the generated three-dimensional model of the grounding grid, generate real-time grounding electrode parameters, calculate and generate grounding calculation report according to the layout parameters of the grounding grid and the grounding electrode parameters, including contact voltage, allowable value of step voltage, maximum contact potential difference, maximum step potential difference, contact potential, step potential and thermal stability verification value; Finally, add the grounding trunk line: draw the grounding trunk line on the three-dimensional model of the grounding grid with grounding electrodes, generate a three-dimensional grounding trunk line model, and connect the equipment to the grounding trunk line; Based on the grounding grid design data, the 3D model of each component of the grounding conductor is constructed through the mainstream 3D modeling algorithm or software system, and the grounding grid information display platform is constructed using spatial geographic information technology and 3D visualization technology to realize the visualization and interaction of the 3D model of the grounding grid system. At the same time, it is compatible with the conductivity monitoring data between the access area ground grids, the local ground grid corrosion status monitoring data and the grounding grid operation status monitoring historical data and applies them to the 3D visualization scene to realize the 3D visualization comprehensive display of the grounding grid; The grounding grid information display platform can intuitively display the layout, connection method and relationship between the grounding grid and other equipment.

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