Grounding method for suppressing electromagnetic interference of nuclear power instrument control cable based on Cidson law

Abstract

The invention relates to the technical field of electromagnetic interference, in particular to a grounding method for suppressing electromagnetic interference of a nuclear power instrument control cable based on a Cidson law. The method comprises the following steps: S1, evaluating an electromagnetic environment around the instrument control cable of the nuclear power station through a spectral analysis method, and determining a main interference source and an affected equipment position; s2, optimizing the design of the grounding network based on the electromagnetic environment according to a Souderson law, and enabling the grounding resistance in the grounding network to be kept in a safe range; and S3, after the grounding network is actually installed in the instrument control cable system of the nuclear power station according to the planning and design requirements, verifying the effectiveness of the grounding network through grounding resistance measurement. According to the design of the invention, through detailed electromagnetic environment evaluation and spectrum analysis, the method can accurately identify a main interference source and an influence range thereof. The ground resistance can be effectively controlled by optimizing the design of the ground network by means of the Cibson law.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-energy dispatching of integrated energy systems, and in particular to a grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law. Background Art

[0002] Electricity, with its clean, efficient, economical, and reliable advantages, has become the primary form of energy transmission. Substations effectively reduce losses during power transmission. Substation wires and cables are primarily used for power transmission, control, computers, instrumentation, and numerical control. These cables all pass through the substation's electrical plant during installation. During substation operation, medium-voltage power cables within the electrical building generate electromagnetic fields, which interfere with adjacent instrument cables and cause transmitted signal distortion, leading to false alarms and missed alarms. This poses a serious threat to the safe and stable operation of the substation and the safety of maintenance personnel. When using multi-core twisted instrument cables, electromagnetic interference from the power cable to the instrument cable cannot be completely avoided due to production difficulties in achieving completely symmetrical core distribution within a unit lay length, and the inability to ensure that the parallel length of the instrument cable and power cable is an integer multiple of the lay length when the instrument cable is laid parallel to the power cable. When grounding the power cable shield and the instrument cable shield, the grounding resistance is greater than 0Ω and ages over time. When the high-frequency electric field in the power cable couples to the power cable shield, the potential of the shield cannot be quickly reduced. Furthermore, the power cable shield and the instrument cable shield are electrically connected, allowing the high-frequency electric field to couple to the instrument cable core through the instrument cable shield, causing interference to the instrument cable. In summary, a grounding method based on the Peterson law is provided to suppress electromagnetic interference in nuclear power instrumentation cables. Summary of the Invention

[0003] The object of the present invention is to provide a grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law, so as to solve the problem of lack of reliable standards for suppressing electromagnetic interference proposed in the above background technology.

[0004] To achieve the above object, the present invention provides a grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law, comprising the following steps: S1. Evaluate the electromagnetic environment around the instrumentation and control cables of the nuclear power plant using spectrum analysis methods to identify the main interference sources and the locations of the affected equipment. S2. According to Peterson's law, optimize the design of the grounding network based on the electromagnetic environment so that the grounding resistance in the grounding network is kept within a safe range. In the process of calculating and designing the grounding network parameters according to Peterson's law, soil heterogeneity parameters, frequency response parameters, and soil salinity parameters are introduced; S3. After the grounding network has been actually installed in the instrumentation and control cable system of the nuclear power plant in accordance with the planning and design requirements, the effectiveness of the grounding network is verified by grounding resistance measurement.

[0005] As a further improvement of this technical solution, in S1, evaluating the electromagnetic environment around the instrumentation and control cables of the nuclear power plant and determining the main interference sources and the locations of the affected equipment include the following steps: S1.1. Use electromagnetic radiation detectors to collect basic data on the on-site electromagnetic environment; S1.2. Determine the location of equipment affected by electromagnetic interference by spectrum analysis methods; S1.3. Organize the collected basic data and analyze the interference pattern using time series analysis methods.

[0006] As a further improvement of the present technical solution, in S1.2, determining the location of the device affected by electromagnetic interference by a spectrum analysis method includes the following steps: S1.21. Acquire electromagnetic field intensity data and preprocess the electromagnetic field intensity data; S1.22. Use the discrete Fourier transform to convert electromagnetic signals in the time domain into frequency domain signals, generate a spectrum, analyze the spectrum, identify the main frequency components and their corresponding amplitudes, and introduce frequency resolution compensation factors, gain compensation factors, and dynamic range compression compensation factors into the discrete Fourier transform. After introducing the frequency resolution compensation factors, gain compensation factors, and dynamic range compression compensation factors, further optimize the discrete Fourier transform by considering issues such as excessive dynamic range compression, spectrum leakage, and electromagnetic signal multipath. S1.23. Mark the significant frequencies in the spectrum graph and record the frequency values. Analyze the amplitude of each frequency peak to determine the interference intensity. S1.24. Compare the spectrum graphs of different test points to find common frequency components. Combined with the location information of the test points, the location of the interference source can be inferred.

[0007] As a further improvement of the present technical solution, in S1.22, the discrete Fourier transform is specifically: ; Introducing frequency resolution compensation factor, gain compensation factor and dynamic range compression compensation factor into discrete Fourier transform: ; Considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath, the discrete Fourier transform is further optimized as follows: ; in, represents the frequency domain signal; The time domain signal samples; Indicates the signal length; represents the frequency index; Represents a time index; represents an imaginary unit; Indicates the length of the signal after zero padding; represents the dynamic range compression factor; represents the gain compensation factor; represents the signal after zero padding; Represents the frequency domain signal after being processed by the frequency resolution compensation factor, the gain compensation factor, and the dynamic range compression compensation factor; It represents the frequency domain signal after processing considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath; Represents a window function; represents a nonlinear function; Represents the steepness parameter of the nonlinear function; Indicates the offset of the nonlinear function.

[0008] As a further improvement of the present technical solution, in S2, according to Peterson's law, optimizing the design of the grounding network based on the electromagnetic environment includes the following steps: S2.1. Inspect existing grounding facilities, collect grounding data, and determine the technical specifications that the grounding network must meet based on the sensitivity of the equipment and the requirements of the electromagnetic environment. S2.2. Select grounding materials based on soil characteristics and cost-effectiveness, and plan the layout of the grounding network; S2.3. Calculate and design the grounding network parameters and plan the grounding path for the instrumentation and control cables according to Peterson's law. S2.4. For critical instrumentation and control cables, use shielding layers to further reduce interference from external electromagnetic fields, and properly connect the shielding layers to form a shielding network.

[0009] As a further improvement of the present technical solution, in S2.3, the calculation and design of the parameters of the grounding network according to Peterson's law includes the following steps: S2.31. Determine the maximum allowable grounding resistance value for the entire grounding network. Use a soil resistivity tester to obtain the soil resistivity. Use the grounding resistance calculation formula, combined with the size and shape of the selected grounding material, to estimate whether the grounding resistance of the grounding device meets the requirements. Incorporate soil heterogeneity parameters, frequency response parameters, and soil salinity parameters into the grounding resistance calculation formula. S2.32. The grounding network is designed to be in the form of a grid. S2.33. Calculate the current distribution according to Peterson's law and adjust the grounding network design based on the actual current distribution.

[0010] As a further improvement of this technical solution, in S2.31, the grounding resistance calculation formula is: ; Introducing soil heterogeneity parameters, frequency response parameters, and soil salinity parameters into the ground resistance calculation formula: ; in, Indicates ground resistance; Indicates the resistivity of the soil; Indicates the length of the grounding body; Indicates the equivalent diameter of the grounding body; It represents the grounding resistance after introducing soil heterogeneity parameters, frequency response parameters and soil salinity parameters; represents the average soil resistivity under frequency response; Indicates frequency; Indicates the influence coefficient of soil salt content on resistivity.

[0011] As a further improvement of this technical solution, in S2.3, the current distribution is calculated according to Peterson's law as follows: ; in, Indicates the flow into The current of each branch; Indicates the total current; Indicates the The resistance of each branch; Indicates the total ground resistance; Indicates the index of a branch.

[0012] As a further improvement of this technical solution, in S2.3, planning the grounding path of the instrumentation and control cable includes the following steps: S2.34. Draw an I&C cable wiring diagram that includes all cable paths, connection points, and equipment locations. Identify the locations of all equipment and instruments that require grounding. S2.35. Design the main grounding grid and determine the connection method; S2.36. Plan the shortest and lowest impedance path for each I&C cable, and avoid forming large loops. S2.37. Install grounding conductors according to the designed I&C cable wiring diagram and connect the equipment to the nearest ground connection point; S2.38. Connect the shield of the instrumentation cable to the ground conductor and use a shield connector. S2.39. Use a ground resistance tester to measure the ground resistance of the grounding network and a voltmeter to measure the voltage drop at key points. Adjust the cable path and ground connection points based on the test results.

[0013] As a further improvement of the present technical solution, in S2.4, a shielding layer is used to further reduce interference from external electromagnetic fields, including the following steps: S2.41. Select a combination of metal braid and metal foil as shielded cable; S2.42. If the cable is short and the interference source mainly comes from one side, choose single-point grounding. For long cables, use multi-point grounding. S2.43. Ground the shield on one side at the power supply end and leave the other side floating. Ground the shield at both ends of the cable and at any intermediate connection points. S2.44. Remove a certain length g of the outer insulation layer at both ends of the cable and at the point where it is to be connected, exposing the shield layer, and wrap the shield layer around the grounding bar; S2.45. Connect the shield to the ground bar using a terminal connector. S2.46. After the connection is completed, use test equipment to check the continuity and shielding effectiveness of the shielding layer.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This Peterson-based grounding method for suppressing electromagnetic interference in nuclear power instrumentation and control cables accurately identifies the primary interference sources and their impact areas through detailed electromagnetic environment assessment and spectrum analysis. By optimizing grounding network design based on the Peterson principle, grounding resistance can be effectively controlled, reducing the risk of misoperation or equipment damage caused by electromagnetic interference, thereby improving the overall reliability and stability of nuclear power plant control systems.

[0015] 2. This Peterson-based grounding method for suppressing electromagnetic interference from nuclear power plant instrumentation and control cables takes into account factors such as soil heterogeneity, frequency response characteristics, and soil salinity. This method not only enhances the design rationality of the grounding network but also improves the accuracy of traditional discrete Fourier transforms by introducing multiple compensation factors. Furthermore, rational cable routing and the use of shielding techniques effectively reduce interference from external electromagnetic fields on instrumentation and control cables, ensuring the normal operation of nuclear power plant instrumentation and control systems. This approach makes grounding design more realistic and provides stable grounding performance under a variety of conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure is a flow chart of the overall method of the present invention. DETAILED DESCRIPTION

[0017] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0018] See also Figure 1 As shown, this embodiment provides a grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law, comprising the following steps: S1. Evaluate the electromagnetic environment around the instrumentation and control cables of the nuclear power plant using spectrum analysis methods to identify the main interference sources and the locations of the affected equipment. In this embodiment, the electromagnetic environment around the instrumentation and control cables of a nuclear power plant is evaluated to determine the main interference sources and the locations of the affected equipment, including the following steps: S1.1. Use an electromagnetic radiation detector to collect basic data on the on-site electromagnetic environment, including electromagnetic field intensity data, electrical equipment type, power, operating status, etc. S1.2. Determine the location of equipment affected by electromagnetic interference by spectrum analysis methods; Spectrum analysis can identify the signal strength of specific frequencies. By comparing spectrum graphs at different locations, locations with the same frequency components can be found, allowing the location of the interference source to be inferred. Spectrum analysis reveals the frequency components and relative strengths of electromagnetic signals, which is crucial for understanding interference patterns (such as periodic or random interference). This helps distinguish interference generated by different types of equipment, providing targeted information for resolving interference issues. Traditional troubleshooting methods may require significant time and resources to test potential interference sources one by one, while spectrum analysis can scan a wide frequency range in a short period of time, quickly identifying the main interfering frequencies and saving troubleshooting time. Determining the location of devices affected by electromagnetic interference using spectrum analysis involves the following steps: S1.21. Acquire electromagnetic field intensity data and preprocess the electromagnetic field intensity data; S1.22. Use the discrete Fourier transform to convert electromagnetic signals in the time domain into frequency domain signals, generate a spectrum, analyze the spectrum, identify the main frequency components and their corresponding amplitudes, and introduce frequency resolution compensation factors, gain compensation factors, and dynamic range compression compensation factors into the discrete Fourier transform. After introducing the frequency resolution compensation factors, gain compensation factors, and dynamic range compression compensation factors, further optimize the discrete Fourier transform by considering issues such as excessive dynamic range compression, spectrum leakage, and electromagnetic signal multipath. Furthermore, the discrete Fourier transform can decompose complex time-domain signals into their constituent frequency components, allowing us to intuitively see which frequency components are the main sources of interference. This decomposition is very important for identifying the signal characteristics of specific devices, especially in complex electromagnetic environments. The discrete Fourier transform is specifically: ; The frequency resolution compensation factor can improve the frequency resolution of the discrete Fourier transform, which means that even if two frequency components are very close, they can be distinguished more accurately. This is especially important for identifying interference sources with similar frequencies but different sources. In the case of high-frequency signals or narrow-band signals, improving the frequency resolution allows analysts to better capture subtle changes in the signal and thus more accurately locate the interference source; the dynamic range compression compensation factor can make the weaker signal components in the spectrum more obvious, which is very important for detecting interference sources that are masked by stronger signals. In actual electromagnetic environments, signal strengths may vary greatly. The dynamic range compression compensation factor can help balance this difference so that all frequency components can be displayed within a suitable range for comprehensive analysis. Through proper dynamic range control, strong signals can be avoided from overwhelming weak signals. situation, thereby better extracting useful signal information and improving the signal-to-noise ratio. Proper dynamic range management can ensure that the signal will neither lose details due to overvoltage nor be overwhelmed by noise due to undervoltage, which makes it possible to better observe the full picture of the signal during analysis; using the window function can reduce spectrum leakage, making the spectrum peak more concentrated and easier to identify the main frequency components of the signal. Reducing spectrum leakage can reduce the interference of strong signals on adjacent frequencies, making weak signals easier to detect; processing multipath effects can reduce false spectrum peaks caused by reflection and refraction, making spectrum analysis more accurate. Processing multipath effects can make signals from different paths easier to distinguish, thereby improving signal separation capabilities, especially in complex electromagnetic environments; introducing frequency resolution compensation factors, gain compensation factors and dynamic range compression compensation factors in discrete Fourier transform: ; Considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath, the discrete Fourier transform is further optimized as follows: ; in, represents the frequency domain signal; The time domain signal samples; Indicates the signal length; represents the frequency index; Represents a time index; represents an imaginary unit; Indicates the length of the signal after zero padding; represents the dynamic range compression factor; represents the gain compensation factor; represents the signal after zero padding; Represents the frequency domain signal after being processed by the frequency resolution compensation factor, the gain compensation factor, and the dynamic range compression compensation factor; It represents the frequency domain signal after processing considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath; represents the window function (Hamming window); represents a nonlinear function; Represents the steepness parameter of the nonlinear function; Represents the offset of the nonlinear function; S1.23. Mark the significant frequencies in the spectrum graph and record the frequency values. Analyze the amplitude of each frequency peak to determine the interference intensity. S1.24. Compare the spectrograms at different test points to identify common frequency components. Combined with the location information of the test points, infer the location of the interference source. The test points are used to measure the specific locations of electromagnetic field strength. If the spectrograms of multiple test points have the same significant frequency components, then these frequency components are likely generated by the same interference source. If a frequency component exists at multiple test points, the approximate direction and distance of the interference source can be estimated based on the location information of these test points and the intensity trend of the frequency component. S1.3. Organize the collected basic data and analyze the interference pattern using time series analysis methods. Interference patterns include periodic interference, random interference, etc. A time series refers to a data set arranged in chronological order, and each data item is associated with a timestamp. In electromagnetic interference analysis, a time series usually contains electromagnetic field strength data that changes over time.

[0019] S2. According to Peterson's law, optimize the design of the grounding network based on the electromagnetic environment so that the grounding resistance in the grounding network is kept within a safe range. In the process of calculating and designing the grounding network parameters according to Peterson's law, soil heterogeneity parameters, frequency response parameters, and soil salinity parameters are introduced; In this embodiment, Peterson's law provides a guiding principle for how current is distributed in the grounding network. This helps optimize the design of the grounding network, ensuring that current is evenly distributed throughout the grounding network, thereby improving grounding efficiency. By optimizing the design of the grounding network, the reliability and stability of the grounding system can be ensured under various operating conditions, reducing equipment failures or system downtime caused by poor grounding. A good grounding design helps reduce electromagnetic interference (EMI), especially in complex electromagnetic environments such as nuclear power plants. Optimizing the grounding network can effectively reduce mutual interference between devices and improve the overall electromagnetic compatibility of the system. Optimizing the design of the grounding network based on the electromagnetic environment according to Peterson's law includes the following steps: S2.1. Inspect existing grounding facilities, including the structure, materials, and connection methods of the grounding network. Collect grounding data, including ground resistance measured by a ground resistance tester and soil resistivity measured by a soil resistivity tester. Based on the sensitivity of the equipment and the requirements of the electromagnetic environment, determine the technical indicators that the grounding network must meet, including ground resistance, soil resistivity, current distribution, and redundancy design. S2.2. Select grounding materials based on soil characteristics and cost-effectiveness. Grounding materials include copper, galvanized steel, etc. Plan the layout of the grounding network, including the main grounding grid, branch grounding grids, and their connection methods. Ensure that the grounding network has sufficient redundancy to cope with single point failures. If a grounding system needs to be installed near the nuclear power plant's instrumentation and control cables to reduce electromagnetic interference, the assessment results show that the main interference frequencies are concentrated in the range of 1kHz to 10MHz, and the soil resistivity is 100Ω·m. Considering high-frequency interference, a material with good high-frequency response characteristics is required. Copper was decided as the grounding material because of its excellent high-frequency conductivity and corrosion resistance. S2.3. Calculate and design the parameters of the grounding network according to Peterson's law to ensure that the grounding resistance is within the specified range. Plan the grounding path for the instrumentation and control cables. Whenever possible, avoid laying instrumentation and control cables parallel to power cables for extended distances. If this is unavoidable, increase the distance between them and take necessary isolation measures to ensure that all instrumentation and control cables can be grounded through a low-impedance path to reduce the voltage drop in the ground loop. The grounding network includes the main grounding grid, branch grounding grids, grounding bodies, grounding wires, grounding bars, connection methods, grounding resistance, and shield grounding. According to Peterson's law, the parameters of the grounding network are calculated and designed, including the following steps: S2.31. Determine the maximum allowable grounding resistance value for the entire grounding network. Use a soil resistivity tester to obtain the soil resistivity. Use the grounding resistance calculation formula, combined with the size and shape of the selected grounding material, to estimate whether the grounding resistance of the grounding device meets the requirements. Incorporate soil heterogeneity parameters, frequency response parameters, and soil salinity parameters into the grounding resistance calculation formula. Furthermore, the grounding resistance calculation formula is: ; Soil resistivity is not uniformly distributed; different soil layers have different resistivities. Introducing soil heterogeneity parameters can more accurately reflect the true condition of the soil, thereby improving the accuracy of ground resistance calculations. Soil conductivity changes with frequency. Introducing frequency response parameters can take into account changes in soil resistivity at different frequencies, making ground resistance calculations more realistic. Salt in the soil significantly affects its conductivity. Introducing soil salinity parameters can better simulate actual soil conditions, especially in special environments such as saline-alkali land. This is particularly important for accurately calculating ground resistance. Accurate ground resistance calculations help optimize grounding path design, reduce electromagnetic interference problems caused by poor grounding, and improve the electromagnetic compatibility of nuclear power instrumentation and control systems. Introducing soil heterogeneity parameters, frequency response parameters, and soil salinity parameters into the ground resistance calculation formula: ; ; ; ; in, Indicates ground resistance; Indicates the resistivity of the soil; Indicates the length of the grounding body; Indicates the equivalent diameter of the grounding body; It represents the grounding resistance after introducing soil heterogeneity parameters, frequency response parameters and soil salinity parameters; represents the average soil resistivity under frequency response; Indicates frequency; Indicates the influence coefficient of soil salt content on resistivity; Indicates the soil thickness of the layer; Indicates the number of soil layers; Indicates the Resistivity of the soil layer; An index indicating the number of soil layers; Indicates the average soil resistivity of the foundation (resistivity at power frequency); represents the frequency response coefficient; Indicates frequency; Indicates the salt content in the soil; represents the salt influence coefficient; S2.32. Design the grounding network to have a grid-like geometry to ensure good current distribution. S2.33. Calculate current distribution according to Peterson's law and adjust the grounding network design based on the actual current distribution to ensure even current distribution and avoid local overheating or other problems. Furthermore, Peterson's law provides a method to calculate the distribution of current in the grounding network. By optimizing the current distribution, it is possible to ensure that the current flows more evenly in the grounding network, avoiding hot spots or overheating caused by localized excessive current. Uniform current distribution can reduce the risk of single-point failures caused by current concentration and improve the reliability and stability of the entire grounding system. This is particularly important for critical facilities such as nuclear power plants, where any single-point failure can have serious consequences. The current distribution calculated according to Peterson's law can be used to optimize the design of the grounding network, ensuring that all critical equipment can be grounded through a low-impedance path and reducing the voltage drop in the ground loop. The current distribution calculated according to Peterson's law is specifically as follows: ; in, Indicates the flow into The current of each branch; Indicates the total current; Indicates the The resistance of each branch; Indicates the total ground resistance; Indicates the index of the branch; Furthermore, planning the grounding path of the instrumentation and control cables includes the following steps: S2.34. Draw an I&C cable routing diagram that includes all cable paths, connection points, and equipment locations. Identify the locations of all equipment and instruments that require grounding and ensure that the cable routing covers all these locations. S2.35. Design a main grounding grid that covers the entire area and includes grounding connection points for all critical equipment. Determine the connection methods (use welded connections to connect the grounding bodies in the main grounding grid and the grounding wires in the branch grounding grids; use bolted connections to ensure a reliable connection between the equipment housing and the grounding bus; use shielded connectors or clamps to secure cable shields to ensure good contact between the shield and the grounding conductor; use welded connections or hydraulic crimping to connect the grounding conductors to ensure electrical continuity between the conductors); and ensure that the internal connections in the grounding grid are reliable. S2.36. Plan the shortest and lowest impedance path for each instrumentation cable, ensuring that the cable path is directly connected to the nearest ground connection point and avoiding large loops, as loops can induce large voltages in changing magnetic fields and introduce interference. S2.37. Install grounding conductors according to the designed instrumentation and control cable wiring diagram, ensuring that the connections between the conductors are firm and reliable, and connect the equipment to the nearest ground connection point to ensure good contact at the connection point; S2.38. Connect the shield of the instrumentation cable to the ground conductor and use a shield connector to ensure a secure connection. S2.39. Use a ground resistance tester to measure the ground resistance of the grounding network and a voltmeter to measure the voltage drop at key points. Adjust the cable routing and ground connection points based on the test results to ensure that all cables can be grounded through a low-impedance path. S2.4. For critical instrumentation and control cables, use shielding layers to further reduce interference from external electromagnetic fields, and properly connect the shielding layers to form a shielding network. Among them, the shielding layer can effectively block the interference of external electromagnetic fields on the internal signals of the cable, thereby improving the integrity and reliability of signal transmission, which is particularly important for environments with extremely high requirements for signal transmission, such as nuclear power plants; the shielding layer can reduce the induced voltage or current generated inside the cable due to changes in the external electromagnetic field, thereby reducing the risk of signal distortion and misoperation; the shielding layer can reduce the noise coupling into the cable and improve the signal-to-noise ratio of the signal, thereby ensuring the quality of signal transmission, which is especially important for sensitive control signals because any interference may cause system malfunction; using the shielding layer to further reduce the interference of external electromagnetic fields includes the following steps: S2.41. Select a combination of metal braid and metal foil as shielded cable; S2.42. If the cable is short and the interference source mainly comes from one side, choose single-point grounding. For long cables or when there are multiple interference sources, multi-point grounding can better reduce interference. S2.43. Ground the shield at one end of the power supply or receiving end, leaving the other end floating to avoid loops that could cause common-mode interference. Ground the shield at both ends of the cable and at any intermediate connection points to ensure a tight and reliable connection between the shield and the ground network. S2.44. Remove a certain length g of the outer insulation layer at both ends of the cable and at the point where it is to be connected, exposing the shield layer, and wrap the shield layer around the grounding bar; S2.45. Connect the shield to the ground bar using the terminal connector, ensuring good electrical contact between the shield and the terminal. S2.46. After the connection is completed, use a test device (continuity tester) to check the continuity and shielding effectiveness of the shielding layer.

[0020] S3. After the grounding network has been actually installed in the instrumentation and control cable system of the nuclear power plant according to the planning and design requirements, the effectiveness of the grounding network is verified by ground resistance measurement; In this embodiment, to help optimize the grounding material and layout, this embodiment randomizes some of the uncertain parameters in the above variables: soil resistivity , frequency response parameters and soil salinity , and use a large number of random samples to perform multiple calculations, and finally optimize the grounding network design based on the results; First set the soil resistivity , frequency response parameters and soil salinity The distribution of , set the number of random sampling N, each simulation, randomly extract a parameter value from these distributions. Generate random ,use , generate random ,use , generate random ,use , in each simulation, the average soil resistivity is calculated based on the generated random values , ,in The average soil resistivity based on the ground (measured at power frequency), is the frequency of the interference signal. Calculate the soil salinity influence coefficient, , where 𝛽 is the salt influence coefficient. The grounding resistance is calculated according to the optimized formula. .

[0021] Perform the above steps N times, and get a different ground resistance value each time Statistical analysis is performed on the 𝑁th simulation results to obtain the grounding resistance The mean and variance of the results are then optimized.

[0022] In this embodiment, the effectiveness of the grounding network is verified by measuring the grounding resistance as follows: prepare a grounding resistance tester, a clamp-type grounding resistance tester, a four-pole test device, etc., and ensure that the test equipment is calibrated and within the validity period; select test points, which should cover the key positions of the entire grounding network, including the main grounding network, branch grounding networks, and grounding connection points of key equipment; before conducting the test, ensure that all power supplies that may affect the test results are disconnected to ensure safety during the test; clean the test points and ensure that the grounding connection points are clean, free of rust and debris for accurate measurement; connect the test line of the test equipment to the selected test point. If the four-pole method is used to test the soil resistivity, it is necessary to Place the current electrode and voltage electrode at the specified distance; start the test equipment according to the operating manual of the test equipment to measure the ground resistance, and be sure to record the ground resistance value of each test point; repeat the above steps at multiple test points to ensure that the important parts of the entire grounding network are covered; analyze the test data and compare the test results with the design requirements for consistency. If it is found that the grounding resistance of a certain test point exceeds the design requirements, it is necessary to find the cause and make corrections; based on the test results, adjust the parts that do not meet the requirements. For example, if the grounding resistance of a certain area is found to be too high, it may be necessary to add grounding bodies or improve soil conditions; after adjustment, test again to ensure that all grounding resistance values ​​meet the design requirements.

[0023] The basic principles, main features, and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention claimed.

Claims

1. A grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law, characterized in that: The following steps are involved: S1. Evaluate the electromagnetic environment around the instrumentation and control cables of the nuclear power plant through spectrum analysis to determine the main interference sources and the locations of the affected equipment; S2. According to Peterson's law, optimize the design of the grounding network based on the electromagnetic environment, so that the grounding resistance in the grounding network is kept within a safe range, and introduce soil heterogeneity parameters, frequency response parameters and soil salinity parameters in the process of calculating and designing the parameters of the grounding network according to Peterson's law; S3. After the grounding network has been actually installed in the instrumentation and control cable system of the nuclear power plant in accordance with the planning and design requirements, the effectiveness of the grounding network is verified by grounding resistance measurement.

2. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 1 is characterized in that: In S1, the electromagnetic environment around the instrumentation and control cables of the nuclear power plant is evaluated to determine the main interference sources and the locations of the affected equipment, including the following steps: S1.

1. Use electromagnetic radiation detector to collect basic data of on-site electromagnetic environment; S1.

2. Determine the location of equipment affected by electromagnetic interference by spectrum analysis method; S1.

3. Organize the collected basic data and analyze the interference pattern by time series analysis method.

3. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 2 is characterized in that: In S1.2, determining the location of the device affected by electromagnetic interference by a spectrum analysis method includes the following steps: S1.

21. Acquire electromagnetic field strength data and pre-process the electromagnetic field strength data; S1.

22. Use discrete Fourier transform to convert electromagnetic signals in the time domain into frequency domain signals, generate a spectrum diagram, analyze the spectrum diagram, identify the main frequency components and their corresponding amplitudes, and introduce frequency resolution compensation factors, gain compensation factors and dynamic range compression compensation factors into discrete Fourier transform. After introducing the frequency resolution compensation factors, gain compensation factors and dynamic range compression compensation factors, the discrete Fourier transform is further optimized by considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath; S1.

23. Mark the significant frequencies in the spectrum graph and record the frequency values, analyze the amplitude of each frequency peak, and determine the interference intensity; S1.

24. Compare the spectrum diagrams of different test points, find the common frequency components, and combine the location information of the test points to infer the location of the interference source.

4. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 3 is characterized in that: In S1.22, the discrete Fourier transform is specifically: ； Introduce frequency resolution compensation factor, gain compensation factor and dynamic range compression compensation factor in discrete Fourier transform: ； Considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath, the discrete Fourier transform is further optimized as follows: ； in, represents a frequency domain signal; Represents the time domain signal samples; Indicates the signal length; represents the frequency index; Represents a time index; represents an imaginary unit; Indicates the length of the signal after zero padding; represents the dynamic range compression factor; represents the gain compensation factor; represents the signal after zero padding; represents the frequency domain signal processed by the frequency resolution compensation factor, the gain compensation factor and the dynamic range compression compensation factor; It represents the frequency domain signal after processing considering the problems of excessive dynamic range compression, spectrum leakage and electromagnetic signal multipath; Represents a window function; represents a nonlinear function; Represents the steepness parameter of the nonlinear function; Indicates the offset of the nonlinear function.

5. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 1 is characterized in that: In S2, according to Peterson's law, the design of the grounding network based on the electromagnetic environment is optimized, including the following steps: S2.

1. Check the existing grounding facilities, collect grounding data, and determine the technical indicators that the grounding network needs to meet based on the sensitivity of the equipment and the requirements of the electromagnetic environment; S2.

2. Select grounding materials based on soil characteristics and cost-effectiveness, and plan the layout of the grounding network; S2.

3. Calculate and design the parameters of the grounding network and plan the grounding path of the instrumentation and control cables according to Peterson's law; S2.

4. For critical instrumentation and control cables, use shielding layers to further reduce interference from external electromagnetic fields, and properly connect the shielding layers to form a shielding network.

6. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 5 is characterized in that: In S2.3, according to Peterson's rule, the parameters of the grounding network are calculated and designed, including the following steps: S2.

31. Determine the maximum allowable grounding resistance value of the entire grounding network, obtain the soil resistivity through a soil resistivity tester, use the grounding resistance calculation formula, combined with the size and shape of the selected grounding material, estimate whether the grounding resistance of the grounding device meets the requirements, and introduce soil non-uniformity parameters, frequency response parameters and soil salinity parameters into the grounding resistance calculation formula; S2.

32. The geometry of the designed grounding network is a grid; S2.

33. Calculate the current distribution according to Peterson's law and adjust the design of the grounding network according to the actual distribution of current.

7. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 6 is characterized in that: In S2.31, the grounding resistance calculation formula is: ； Introduce soil heterogeneity parameters, frequency response parameters and soil salinity parameters into the ground resistance calculation formula: ； in, Indicates ground resistance; Indicates the resistivity of soil; Indicates the length of the grounding body; Indicates the equivalent diameter of the grounding body; It represents the grounding resistance after introducing soil heterogeneity parameters, frequency response parameters and soil salinity parameters; represents the average soil resistivity under frequency response; Indicates frequency; It represents the influence coefficient of soil salt content on resistivity.

8. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 5 is characterized in that: In S2.3, the current distribution is calculated according to Peterson's law as follows: ； in, Indicates the flow into The current of each branch; Indicates the total current; Indicates The resistance of each branch; Indicates the total ground resistance; Indicates the index of a branch.

9. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 5 is characterized in that: In S2.3, planning the grounding path of the instrumentation and control cable includes the following steps: S2.

34. Draw the I&C cable wiring diagram, which includes the paths, connection points and equipment locations of all cables, and determines the locations of all equipment and instruments that need to be grounded; S2.

35. Design the main grounding grid and determine the connection method; S2.

36. Plan the shortest path with the lowest impedance for each I&C cable and avoid forming large loops; S2.

37. Install grounding conductors according to the designed I&C cable wiring diagram and connect the equipment to the nearest ground connection point; S2.

38. Connect the shield of the instrumentation cable to the ground conductor and use a shield connector; S2.

39. Use a ground resistance tester to measure the ground resistance of the grounding network, use a voltmeter to measure the voltage drop at key points, and adjust the cable path and ground connection points based on the test results.

10. The grounding method for suppressing electromagnetic interference of nuclear power instrumentation and control cables based on Peterson's law according to claim 5 is characterized in that: In S2.4, a shielding layer is used to further reduce the interference of external electromagnetic fields, including the following steps: S2.

41. Select a combination of metal braid and metal foil as the shielded cable; S2.

42. If the cable is short and the interference source mainly comes from one side, choose single-point grounding. For long cables, use multi-point grounding. S2.

43. Ground the shield at one side of the power supply end and keep the other side floating, and ground it at both ends of the cable and any intermediate connection points; S2.

44. Remove a certain length g of the outer insulation layer at both ends of the cable and where it needs to be connected, expose the shielding layer, and wrap the shielding layer around the grounding bar; S2.

45. Connect the shield to the ground bar using a terminal connector; S2.

46. After the connection is completed, use the test equipment to check the continuity and shielding effectiveness of the shielding layer.

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