An electromagnetic interference test method for a typical DCS signal transmission loop of a nuclear power plant
By using electromagnetic interference testing methods for the DCS signal transmission loop of nuclear power plants, analog signals were screened, interference sources were calibrated and grounding methods were determined, and frequency injection and frequency sweep tests were conducted. This solved the problem of the disconnect between laboratory testing and on-site operating conditions, enabled accurate assessment of composite interference sources and determination of safe operating distances, and improved the operational safety of nuclear power plants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CNNC FUJIAN FUQING NUCLEAR POWER
- Filing Date
- 2025-09-16
- Publication Date
- 2026-07-10
AI Technical Summary
Existing electromagnetic interference testing methods cannot effectively assess the specific impact on the DCS signal transmission loop of nuclear power plants, especially the impact of composite interference sources on the DCS signal transmission loop in the field. Furthermore, laboratory testing is disconnected from field operating conditions, making it impossible to accurately assess the degree of interference with weak signals and determine safe operating distances.
By screening analog signals in the DCS signal transmission loop system of nuclear power plants, interference sources are calibrated, typical spectrum and intensity are determined, the grounding method of the DCS signal on site is determined, frequency injection and frequency sweep tests are performed, the sensitivity thresholds of conducted, electric, and magnetic field interference are determined, and equivalent injection tests are performed using signal generators and other equipment. The safe operating distance is calculated in combination with electromagnetic theory.
It enables accurate assessment of complex interference sources at nuclear power plants, determines safe operating distances, improves the working efficiency and operational safety of nuclear power plants, and avoids unexpected shutdowns and reactor stoppages.
Smart Images
Figure CN121114587B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of electromagnetic testing technology for DCS signal transmission loops, and particularly relates to an electromagnetic interference testing method for typical DCS signal transmission loops in nuclear power plants. Background Technology
[0002] Electromagnetic interference refers to the adverse effects of electromagnetic waves on electronic equipment and circuits. When electromagnetic energy exceeds the normal range, it may lead to decreased equipment performance, signal distortion, or even system failure.
[0003] In nuclear power plants, the distributed control system (DCS) is responsible for real-time data acquisition, status monitoring, and precise control of core equipment such as the reactor and cooling system. Its stability directly determines the safety and reliability of the unit's operation. The DCS system relies on the collaborative work of numerous sensors and control modules, making it susceptible to electromagnetic interference from equipment such as welding machines in industrial settings. This interference can lead to signal transmission distortion and subsequent equipment malfunctions, posing a potential threat to the safe and stable operation of the nuclear power plant.
[0004] A typical DCS signal transmission loop consists of primary measurement elements, corresponding typical DCS cards, and corresponding measurement cables. Local equipment parameters (such as temperature and pressure) are acquired by sensors, transmitted via measurement cables, and processed by the DCS cards to achieve accurate data acquisition and real-time control of the production process. However, equipment such as welding machines and electric drills operating on-site can generate complex forms of electromagnetic interference. This interference can cause signal fluctuations in the DCS transmission loop, potentially leading to equipment malfunctions or even unplanned shutdowns, posing a significant threat to production safety and continuity.
[0005] Existing electromagnetic interference testing methods mainly measure the electromagnetic compatibility characteristics of industrial products, but they do not conduct interference tests on DCS signal transmission circuits at nuclear power plant sites. In particular, they cannot effectively assess the specific impact of combined interference sources such as welding machines, electric drills, angle grinders, magnetic drills, electric hammers, and walkie-talkies on DCS signal transmission circuits at the site, and thus cannot determine the safe operating distance of interference source equipment.
[0006] In addition, the current electromagnetic interference test of DCS signal transmission circuits mainly uses surge generators, radio frequency signal generators and other equipment in the laboratory to test their electromagnetic compatibility characteristics. This has obvious drawbacks, such as the significant differences between laboratory grounding systems (e.g., single-point grounding), cable layout and complex grounding in the field (mixed single / double-end grounding), and dense cable tray environment, which leads to the interference coupling path being out of touch with the actual working conditions. Summary of the Invention
[0007] The main objective of this application is to provide an electromagnetic interference testing method for typical DCS signal transmission loops in nuclear power plants. This method overcomes the difficulties of scene distortion, coarse evaluation, and difficulty in injecting and quantifying interference signals in traditional testing. It also addresses the safety risks of directly using strong interference sources on-site in nuclear power plants and the disconnect between traditional laboratory testing and on-site operating conditions. This method provides an effective standard for on-site interference testing in nuclear power plants, accurately assesses the degree of interference with weak signals, clarifies safe distances for on-site operations, improves the working efficiency and operational safety of nuclear power plants, and avoids unexpected shutdowns and reactor stoppages caused by electromagnetic interference.
[0008] To achieve the above objectives, the technical solution adopted in this application is as follows:
[0009] An electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant includes:
[0010] S1. Select the analog signals that are subject to interference in the DCS signal transmission loop system of the nuclear power plant as the test objects;
[0011] S2. Conduct interference source calibration and determine typical spectrum and intensity;
[0012] S3. Determine the grounding method for the DCS signals on site;
[0013] S4. Frequency injection determines the sensitivity threshold for conducted interference;
[0014] S5. Conduct frequency sweep test for electric field radiation interference;
[0015] S6. Conduct a frequency sweep test for magnetic field radiation interference.
[0016] S7. Perform conducted interference frequency sweep test;
[0017] S8. Determine the safe operating distance for interference at different frequencies.
[0018] As one feasible approach, in S1, the analog signal includes a low-energy-level signal.
[0019] As an feasible approach, in S2, conducted, magnetic field, and electric field emission tests are conducted on different devices among the selected interference sources to determine the typical interference source characteristics of different devices at different frequency bands and distances.
[0020] As an feasible approach, in S3, the shielded cable is disconnected inside the local control box, and an ohmmeter is used to measure the resistance to ground of the shielding layer on the DCS cabinet side and the local equipment side to determine the grounding method.
[0021] As an feasible approach, grounding methods include single-ended grounding, double-ended grounding, multi-ended mixed grounding, and floating ground.
[0022] As an feasible approach, in S4, based on the interference calibration data obtained in S2, the largest amplitude value in the data is selected, and interference is applied to the shielded cable of the selected signal. The injected interference power is continuously adjusted according to the principle of increasing amplitude, and the signal port data on the DCS is monitored in real time until abnormal fluctuations occur in the data. At this point, the current injected interference intensity is maintained and no further adjustment is made.
[0023] As an feasible approach, in S5, interference is applied starting from the shortest distance calibrated from the antenna to the device under test. The amplitude of the applied interference is selected according to the interference test calibration data of various tools and equipment. The signal under test is recorded, and the signal at the test point is checked for fluctuation.
[0024] As an feasible approach, in S6, interference is applied by arranging the antenna at the closest distance to the device under test as specified in the calibration test. The amplitude of the interference is determined by the data obtained from the calibration test and using the calibration value. The signal under test is recorded, and the signal at the test point is checked for fluctuations. The results of the magnetic field radiation emission test are then summarized.
[0025] As an feasible approach, in S7, an interference signal is injected into the cable under test, and a monitoring probe is used to read the test signal on the test cable, perform corresponding waveform recording, and monitor whether the basic performance parameters of the signal at the test point fluctuate or exceed the rated requirements.
[0026] As an feasible approach, in S8, the safe operating distance of the test object tool at the test signal point is calculated by using the test frequency and test amplitude obtained in the experiment.
[0027] Compared with existing technologies, the electromagnetic interference testing method for typical DCS signal transmission loops in nuclear power plants provided in this application has the following advantages:
[0028] This application, taking into account the reality that nuclear power DCS systems are widely used on-site and susceptible to interference, applies laboratory electromagnetic interference testing technology to the field. It achieves equivalent simulation of typical DCS signal transmission loops by combined interference sources such as welding machines, electric drills, angle grinders, magnetic drills, electric hammers, and walkie-talkies, confirming the impact of related interference on DCS signal transmission loops and the safe operating distance to avoid interference, thus providing a strong basis for the effective management of electromagnetic interference in nuclear power plants in the future.
[0029] Furthermore, this application calibrates the interference source through a third-party laboratory, generates characteristic interference signals containing typical spectra and intensities, and uses equipment such as signal generators, power amplifiers, and injection calipers to replace real tools for equivalent injection in field testing. This avoids the safety risks of directly using strong interference sources, solves the problem of disconnect between traditional testing and field conditions, and improves the realism of interference simulation.
[0030] This application proposes a method for determining the sensitivity threshold. Interference power is applied in an increasing gradient according to a typical frequency calibrated on-site, and DCS signal port data is monitored in real time. The critical amplitude of the first abnormal fluctuation is recorded as the sensitivity threshold. This method avoids the influence of many factors such as low interference coupling efficiency and diverse on-site environmental layouts, and can test the impact of the most extreme signal interference on the DCS signal transmission loop.
[0031] This application proposes that when the test signal does not exhibit sensitive issues after the injection of the closest and strongest interference, further testing at more distant locations and injection of lower amplitude interference will not be conducted. It is equivalent to assuming that the simulated tool and equipment with interference intensity lower than that tool will not affect the test equipment and signal, and this distance is equivalent to assuming that the distance is the minimum safe distance.
[0032] This application utilizes frequency sweep testing and electromagnetic theory calculations, combined with safety margin design, to determine the safe distance between the interference source and the signal under test, thereby quantifying the safe operating distance while ensuring the safety margin. Attached Figure Description
[0033] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the technical description will be briefly introduced below.
[0034] Figure 1 A flowchart of the electromagnetic interference test method for a typical DCS signal transmission loop in a nuclear power plant provided in this application;
[0035] Figure 2 The field sensitivity threshold test configuration diagram provided for this application;
[0036] Figure 3 The configuration diagram for the field electric field radiation injection test provided in this application;
[0037] Figure 4 The diagram showing the configuration of the field magnetic field radiation injection test provided in this application;
[0038] Figure 5 The diagram shows the configuration of the field conducted interference injection test provided in this application. Detailed Implementation
[0039] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0040] like Figure 1 As shown, this application provides an electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant, comprising the following steps:
[0041] S1: Determine the targets for interference testing. Select analog signals in the nuclear power plant's DCS signal transmission loop system that are susceptible to interference as test targets, including low-energy signals (milliampere / millivolt level) such as temperature, pressure, and vibration, as well as their corresponding DCS cards. The selection of measurement cables includes twisted-pair cables and coaxial cables, essentially covering the entire range of instrumentation and control measurement cables used in nuclear power plants.
[0042] Step S1 includes local primary measurement elements, corresponding typical DCS cards, and corresponding measurement cables. The measurement objects of the nuclear power plant instrumentation and control system are switching and analog quantities. Since switching signals are strong signals and not easily interfered with, the test objects mainly include local primary measurement elements for analog quantities such as temperature / pressure / flow / frequency / displacement / vibration / current measurements. Regarding the corresponding DCS cards, although there are significant differences in the circuitry of DCS cards provided to the field by different manufacturers, the types of measurement signals mainly include thermocouples / absolute vibration / relative vibration / frequency / milliampere current / thermal resistance / voltage / microcurrent, etc. Considering that most of the above signal variations are at the milliampere, millivolt, or even lower energy levels, the above-mentioned low-voltage signal cards are mostly selected for signal testing. The selection of measurement cables includes twisted-pair cables and coaxial cables, basically covering the entire range of instrumentation and control measurement cables in nuclear power plants.
[0043] S2: Conduct interference source calibration to determine typical spectrum and intensity. Send field interference sources such as welding machines, walkie-talkies, and magnetic drills to a third-party laboratory for conducted emission, electric field radiation, and magnetic field radiation tests to extract typical frequency bands and maximum interference amplitudes for each source. Generate characteristic interference signals based on the measured data and use them to replace the actual tools in the test circuit.
[0044] Step S2 involves calibrating the interference source by sending the selected interference source to a third-party laboratory to conduct conducted, magnetic field, and electric field emission tests on different devices. This process identifies the typical interference source characteristics of different devices at different frequency bands and distances, making it possible to conduct simulated interference source tests on-site.
[0045] Taking the introduction of interference sources from tools and equipment in nuclear power plants as an example, the interference forms mainly include electric field radiation, magnetic field radiation, and conducted emission. Reverse interference can be injected into the electrical equipment cables and probes in the test channel to verify the impact of various tools and equipment on various electrical equipment at the nuclear power plant site. Ultimately, interference calibration data for various tools and equipment can be obtained, including the name of the tested equipment, equipment model, test frequency, test item, test distance, typical interference frequency, and typical interference frequency amplitude.
[0046] S3: Determine the grounding method of the DCS signal on site. Disconnect the shielded cable inside the local control box, and use a high-precision ohmmeter to measure the resistance to ground of the shielding layer on the DCS cabinet side and the local equipment side to determine typical grounding types such as single-ended grounding, double-ended grounding, and floating ground.
[0047] There are four main typical grounding methods for various signals at nuclear power plant sites: single-ended grounding, double-ended grounding, multi-ended hybrid grounding, and floating ground. The anti-interference capabilities of these grounding methods differ across frequency bands. Therefore, the grounding method for DCS signals should be determined without altering the original grounding design to ensure that test results are completely consistent with those at the nuclear power plant site and to analyze the advantages and disadvantages of different grounding methods.
[0048] S4: Frequency injection determines the sensitivity threshold for conducted interference.
[0049] By setting up a field test system including power amplifiers, power meters, signal generators, injection calipers, monitoring calipers, field strength probes, etc., Figure 2 As shown, the received bit signal has reached a stable working state, and stable signal data can be seen on the DCS display screen.
[0050] Based on the interference calibration data of various tools obtained in step S2, select the largest amplitude value in the data. For example, select the typical interference frequencies measured during the calibration test of the welding machine and the magnetic drill. Use an injection clamp to apply interference to the shielded cable of the selected signal, and continuously adjust the injected interference power according to the principle of increasing the amplitude. Monitor the signal port data on the DCS in real time until abnormal fluctuations occur in the data, then maintain the current injected interference intensity without further adjustment. If the test signal data does not fluctuate when the power amplifier outputs maximum power, stop adjusting the amplitude of the injected interference at the maximum power output. Monitor the spatial interference of the test cable at the test frequency point through the field strength probe, and record the field strength data monitored by the field strength probe at the sensitive threshold moment or the moment when the power amplifier outputs maximum power. Change the test frequency point, repeat the above operation steps, and record the test data at each frequency point to obtain the sensitive threshold test data for each signal point.
[0051] Based on the interference test calibration data of various tools and equipment, the typical test distance and test amplitude of magnetic drills and welding machines in the calibration test can be obtained. Combined with the interference test calibration data of various tools and equipment, the sensitivity threshold test data of each signal point, and according to the near-field continuity equation formula, the intensity of interference is inversely proportional to the cube of the distance, the safe operating distance of the tools and equipment at the test signal point can be calculated. In order to avoid safety hazards caused by measurement errors, a certain safety margin is considered, and the different safe operating distances at different frequency points can be confirmed.
[0052] Due to limitations of the power amplifier used in on-site testing, the maximum input power could not be determined for sensitive threshold values when conducting reverse injection interference tests on some signals. However, based on the near-field continuity equation, the intensity of interference is inversely proportional to the cube of the distance. Therefore, the usable distance of the tool at the test signal location when the input power is at its maximum can be calculated. Although this distance is not the minimum safe distance, it can be determined that using the tool at a distance greater than this will not affect the signal at the test location. Thus, the safe usable distance for non-sensitive equipment at different frequency locations can be derived.
[0053] S5: Electric field radiation interference sweep frequency test.
[0054] By setting up an on-site testing system including power amplifiers, power meters, signal generators, RF antennas, monitoring calipers, field strength probes, etc., such as... Figure 3 As shown, the received bit signal has reached a stable working state, and stable signal data can be seen on the DCS display screen.
[0055] Start by setting up the antenna at the shortest distance from the device under test (DUT) and apply interference. Select the interference amplitude according to the interference test calibration data of various tools and equipment. Use an oscilloscope with a current clamp to record the waveform of the signal under test (if the DUT cannot record the waveform, observe the fluctuation trend of the DCS measurement channel) and check whether the signal at the test point fluctuates.
[0056] By varying the distance from the antenna to the test point, tests are conducted sequentially from near to far. If no sensitive issues are observed with the test signal at close range, further tests at more distant points are discontinued. This is equivalent to assuming that the simulated instrument will not affect the tested equipment and signal through spatial radiation. Considering the potential lack of suitable placement conditions for various test distances on-site and the uncertainty of the antenna at close range, tests can be conducted at a fixed distance. Simultaneously, the interference intensity applied by the antenna is adjusted to ensure that the interference received by the test point is equivalent to the intensity applied at different distances.
[0057] At each selected signal point, based on the arrangement of the point sensors, junction boxes, and cables, and in accordance with electromagnetic compatibility testing theory, typical electromagnetic interference electric field injection locations are selected, and interference injection is completed. The results of electric field radiation interference injection tests at each point are then summarized.
[0058] S6: Magnetic field radiation interference sweep frequency test.
[0059] A loop antenna is used instead of an electric field antenna; the remaining test procedures are the same as for electric field radiation. Figure 4 As shown, by setting up a field test system including power amplifier, power meter, signal generator, loop antenna, monitoring caliper and other equipment, it was confirmed that the signal of the test position reached a stable working state and stable signal data could be seen on the DCS display screen.
[0060] Arrange the antenna at the shortest distance specified from the device under test (DUT) and apply interference. The interference amplitude should be determined based on data obtained from the calibration test and the values calibrated in the laboratory. Use an oscilloscope with current clamps to record the signal under test (if the DUT cannot record, observe the fluctuation trend of the DCS measurement channel). Check for signal fluctuations at the test point. Summarize the results to obtain the magnetic field radiation emission test results.
[0061] S7: Conducted interference frequency sweep test.
[0062] By setting up a field test system, including equipment such as power amplifiers, power meters, signal generators, injection calipers, and monitoring calipers, etc., Figure 5 As shown, confirm that the pilot bit signal has reached a stable working state, and view the stable signal data on the DCS display screen.
[0063] The interference test method is largely the same as the threshold test method in step S4. An interference signal is injected into the cable under test using an injection clamp, and then a monitoring probe is used to read the signal on the test cable, recording the waveform and monitoring whether the basic performance parameters of the signal at the test point fluctuate or exceed the rated requirements. However, the test frequency is different. Conducted interference is injected using a frequency sweep, and the amplitude of the interference is based on the interference test calibration data of various tools and equipment. The sensitivity threshold method uses fixed frequencies and continuously increases the amplitude during injection.
[0064] S8: Determine the safe operating distance for interference at different frequencies.
[0065] Based on the principle of antenna reciprocity, the radiation field strength distribution and radiation pattern of an antenna when it acts as a transmitter are strictly consistent with its receiving sensitivity and polarization characteristics when it acts as a receiver. Therefore, in a third-party laboratory, interference sources such as walkie-talkies and welding machines can be used as "transmitting antennas," and their near-field radiation field strength can be measured using a standard receiving antenna. Subsequently, in on-site testing, by adjusting the antenna's transmitting power, the field strength value of the test equipment calibrated in the laboratory can be reproduced, allowing it to directly replace the actual equipment for testing the DCS system.
[0066] Furthermore, since the interference amplitude is inversely proportional to the cube of the distance to the test signal, the safe operating distance of the test object at the test signal point can be calculated by using the test frequency and test amplitude obtained in the experiment.
[0067] Considering the sensitivity and frequency response error of the field strength probe, in order to ensure the safety and effectiveness of the calculation results in guiding the safe use of the tested object, the calculated distance value is relaxed by a certain percentage as a reference, and the safe use distance of the tested object under the interference source is finally determined.
[0068] This application proposes a method for determining safe distance based on electromagnetic theory. By utilizing the principle of antenna reciprocity and Maxwell's equations, a quantitative relationship between interference amplitude and distance is established. In addition, a safety margin is set in combination with the uncertainty of the on-site environment to generate minimum safe distance parameters for interference sources such as welding machines and walkie-talkies, thus clarifying the safe operating distance for on-site interference-related operations.
[0069] This application overcomes the shortcomings of traditional testing, such as scenario distortion and rough assessment, by adopting the process of "object screening - test tool calibration - grounding method determination - interference injection - safety distance assessment". It provides a scientific basis for safety prediction and protection measure optimization for interference-related operations at nuclear power plants, and significantly improves the practicality and effectiveness of the electromagnetic interference management system.
[0070] This application involves sending on-site interference sources, such as walkie-talkies, electric hammers, magnetic drills, hot air guns, angle grinders, and welding machines, to a third-party laboratory for conducted conduction, magnetic field, and electric field radiation emission tests. The spectrum and intensity parameters of typical interferences are extracted. Then, injection equipment such as signal generators, power amplifiers, calipers, field strength controllers, and various RF antennas are used to replace the actual interference sources for on-site testing. This method solves the safety risks of directly using strong interference sources and the problem of the disconnect between traditional laboratory testing and on-site operating conditions, achieving an equivalent simulation of complex interferences at nuclear power plant sites.
[0071] This application proposes a method for determining the conducted interference sensitivity threshold. Specifically, a typical frequency signal calibrated on-site is injected through the shield of a signal cable, and the DCS signal port data is dynamically monitored. The critical amplitude at which the signal first becomes abnormal is recorded as the conducted interference sensitivity threshold. This method solves the problems of difficulty in injecting and quantifying interference signals in traditional testing, enabling a quantitative assessment of the interference impact of different types of DCS channel loops at different interference frequencies.
[0072] This application proposes a method for determining safe distances based on electromagnetic theory. Utilizing the principle of antenna reciprocity and Maxwell's equations, a quantitative relationship between interference amplitude and distance is established. Furthermore, a safety margin is set considering uncertainties in the field environment to determine the minimum safe distance between the interference source and the measured signal. This mechanism provides a quantifiable safety boundary for interference-related operations at nuclear power plants, improving on-site feasibility.
[0073] This application proposes a method for determining the safe distance when the DCS test channel is still insensitive to maximum power injection interference. Due to the power limitations of the power amplifier used in on-site testing, the sensitivity threshold cannot be determined when conducting reverse injection interference tests on some signals, and the field strength value at this time is recorded. According to the near-field continuity equation, the intensity of the interference is inversely proportional to the cube of the distance. The operating distance of the tool at the test signal point when the input power is maximum can be calculated. Although this distance is not the minimum safe distance, it can be determined that using the tool at a distance greater than this will not affect the DCS signal. Therefore, this distance is approximately considered as the minimum safe distance between this type of interference source and the signal under test.
[0074] This application proposes a graded illumination test method for radio frequency antennas, enabling multi-dimensional and accurate evaluation of the immunity of DCS cards under complex radiation environments. For example, caliper injection is used for conducted interference, electric field radio frequency antennas are used for electric field interference, and loop antennas are used for magnetic fields.
[0075] This application proposes to test at a fixed distance by adjusting the antenna to apply different interference intensities, ensuring that the interference to the DCS under test is equivalent to the intensity applied at different distances, thereby solving the problems of not being able to adjust the test distance on-site and not being able to place test equipment at close range.
[0076] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.
Claims
1. A method for testing electromagnetic interference in a typical DCS signal transmission loop of a nuclear power plant, characterized in that, include: S1. Select analog signals in the DCS signal transmission loop system of nuclear power plants that are susceptible to interference as test objects; S2. Conduct interference source calibration and determine typical spectrum and intensity; S3. Determine the grounding method for the DCS signals on site; S4. Frequency injection determines the sensitivity threshold for conducted interference; S5. Conduct frequency sweep test for electric field radiation interference. S6. Conduct a frequency sweep test for magnetic field radiation interference. S7. Perform conducted interference frequency sweep test; S8. Determine the safe operating distance for interference at different frequencies.
2. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S1, the analog signal includes low-energy-level signals.
3. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S2, conducted, magnetic field, and electric field emission tests are conducted on different devices among the selected interference sources to determine the typical interference source characteristics of different devices at different frequency bands and distances.
4. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S3, disconnect the shielded cable inside the local control box, use an ohmmeter to measure the resistance to ground of the shielding layer on the DCS cabinet side and the local equipment side, and determine the grounding method.
5. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1 or 4, characterized in that, Grounding methods include single-ended grounding, double-ended grounding, multi-ended mixed grounding, and floating ground.
6. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S4, based on the interference calibration data obtained in S2, the largest amplitude value in the data is selected, and interference is applied to the shielded cable of the selected signal. The injected interference power is continuously adjusted according to the principle of increasing amplitude, and the signal port data on the DCS is monitored in real time until abnormal fluctuations occur in the data. Then, the current injected interference intensity is maintained and no further adjustment is made.
7. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S5, the antenna is arranged and interference is applied starting from the shortest distance calibrated from the device under test. The amplitude of the applied interference is selected according to the interference test calibration data of various tools and equipment. The waveform of the signal under test is recorded, and the signal at the test point is checked for fluctuation.
8. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S6, the antenna is arranged at the shortest distance from the device under test as specified in the calibration test, and interference is applied. The amplitude of the interference is determined according to the data obtained from the calibration test and the calibration value is used. The signal under test is recorded, and the signal at the test point is checked for fluctuation. The results of the magnetic field radiation emission test are then obtained.
9. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S7, an interference signal is injected into the cable under test, and a monitoring probe is used to read the test signal on the test cable, perform corresponding waveform recording, and monitor whether the basic performance parameters of the signal at the test point fluctuate or exceed the rated requirements.
10. The electromagnetic interference testing method for a typical DCS signal transmission loop in a nuclear power plant according to claim 1, characterized in that, In S8, the safe operating distance of the test object tool at the test signal point is calculated based on the test frequency and test amplitude obtained in the experiment.