Analysis method and system for common cause failure of electrical system

Abstract

The present invention discloses an analysis method and system for common cause failures in electrical systems, the method comprising the following steps: S11: determining the common cause failure risks of multiple electrical systems caused by the same electrical equipment through engineering analysis, and using this as input for accident analysis; S12: determining the accident consequences of common cause failures in electrical systems through accident analysis; S13: determining diversified adjustment plans for electrical equipment based on the accident consequences of common cause failures in electrical systems. The equipment independence analysis step determines a diversified analysis method for electrical equipment, filling a gap in the nuclear power industry at home and abroad.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power plant electrical system design, and in particular to an analysis method and system for common cause failures of an electrical system. Background Art

[0002] In the past, the single failure criterion was mainly used in the accident analysis of nuclear power plants, that is, a single event or failure was used as the analysis object to conduct consequence analysis and design of response plans. In system design, the principles of redundancy and in-depth defense are mainly used to provide multi-level barriers for accident response. Common cause failure is the functional failure of multiple systems, structures and components caused by the same reason. It may cause multiple redundant systems or multiple in-depth defense level systems to fail at the same time, which will cause a breakthrough in the original safety design system and may cause accident conditions that were not considered in the original safety analysis system, creating new challenges for the design of safety systems.

[0003] At present, there is no analysis method applicable to the electrical system of nuclear power plants at home and abroad. The only one with a high relevance is the diversified design guidelines for instrumentation and control systems given in the document NUREG / CR-7007 "Diversification Strategy for Nuclear Power Plant Instrumentation and Control Systems" of the US Nuclear Regulatory Commission.

[0004] This guideline is mainly applicable to the design of the I&C system of nuclear power plants. It clarifies the degree of diversity of I&C systems that need to deal with common cause failures, and points out that the difference in technical solutions is the aspect that contributes the most to the diversity of system design. This guideline divides the parts of system design that may have common cause failures into seven aspects: function, design, equipment manufacturing, logic processing equipment, signal, logic, and human factors. Through the diversification of these seven aspects, the purpose of reducing the risk of common cause failures and improving the safety of I&C systems is achieved.

[0005] The main object of analysis of the above technical solution is the instrumentation and control system. Since there are large differences in structure and function between the electrical system and the instrumentation and control system, this solution is not applicable to the electrical system.

[0006] For electrical system analysis, this solution has the following main defects:

[0007] 1) The solution only focuses on the design of the system, lacks analysis of the supporting system and environment, and is not complete and comprehensive;

[0008] 2) The main focus of this solution is on logic signals, which corresponds to the characteristics of the instrumentation and control system, but the logic signals of the electrical system are not the key points of its common cause failures.

[0009] This plan is mainly used to analyze and judge the degree of diversity of system design. It does not take into account the overall design, construction, progress, cost and other aspects of the nuclear power plant and cannot be directly used for the final plan decision. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a method and system for analyzing common cause failures of an electrical system in view of at least one defect in the prior art.

[0011] The technical solution adopted by the present invention to solve the technical problem is: constructing an analysis method for common cause failures of an electrical system, including the steps of equipment independence analysis:

[0012] S11: Determine the risk of common cause failures in multiple electrical systems caused by the same electrical equipment through engineering analysis and use it as input for accident analysis;

[0013] S12: Determine the consequences of common cause failures in electrical systems through accident analysis;

[0014] S13: Determine diversified adjustment plans for electrical equipment based on the accident consequences of common cause failures in the electrical system.

[0015] Preferably, in the method for analyzing common cause failures of an electrical system of the present invention, the method further comprises a human factor related independence analysis step:

[0016] S21: Through experience feedback, determine the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment, and determine diversified adjustment plans for personnel.

[0017] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, the method further comprises a functional independence analysis step:

[0018] S31: By analyzing the failure of the support system of the electrical system, determine the common cause failure risk of multiple electrical systems caused by the support system;

[0019] S32: Determine diversified adjustment plans for the support system based on the risk of common cause failures in multiple electrical systems caused by the support system;

[0020] S33: Determine the risk of common cause failures in multiple electrical systems caused by electrical failures by analyzing the failures of multiple electrical systems caused by electrical failures themselves;

[0021] S34: Determine the independence adjustment plan of the electrical systems based on the risk of common cause failures in multiple electrical systems caused by electrical factors.

[0022] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, the method further comprises a spatial independence analysis step:

[0023] S41: Determine the risk of common cause failures in multiple electrical systems caused by space through analysis of multiple electrical system failures caused by nuclear power plant disasters;

[0024] S42: Determine the adjustment plan for space independence based on the risk of common cause failures of multiple electrical systems caused by the space.

[0025] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, step S11 comprises:

[0026] By performing failure mode and failure consequence analysis on electrical equipment in the electrical system, the key electrical equipment that can directly cause failure of the electrical system and the use of the key electrical equipment in multiple electrical systems are determined, and then the common cause failure risk of multiple electrical systems caused by the same key electrical equipment is determined, and one or more common cause failure groups are set according to the key electrical equipment as input for accident analysis;

[0027] Step S12 includes:

[0028] Using the common cause failure groups determined by the engineering analysis as input, an analysis of support system failures caused by the key electrical equipment is performed to determine the accident consequences of common cause failures of the electrical system.

[0029] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, the device independence analysis step further comprises:

[0030] S14: Taking the high-frequency accidents in the accident consequences as the starting point and the safe state of the nuclear power plant as the goal, analyze the main defense line and diversified defense line systems required in the process, and determine the diversified adjustment plans for the electrical systems that power the main defense line and diversified defense line systems.

[0031] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, the device independence analysis step further comprises:

[0032] S15: Based on the determined diversified adjustment plans for the electrical equipment, with reference to the experience feedback data, comparison is performed to arrive at the optimal adjustment plan.

[0033] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, the device independence analysis step further comprises:

[0034] S16: Through the probabilistic analysis method, the common cause failure of a single electrical equipment in the optimal adjustment plan is taken as the modeling object, and its common cause failure probability is calculated to provide a reference for the diversification requirements of the electrical equipment.

[0035] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, the device independence analysis step further comprises:

[0036] S17: Through ALARP analysis, technical and economic comparisons are made to clarify the impact of each option on the nuclear power plant and all related systems in many aspects, and then determine the option that reduces the overall common cause failure risk to as low as reasonably practicable (ALARP).

[0037] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, step S31 comprises:

[0038] Analyze the impact of the failure of a single or multiple shared support systems, obtain the operating condition changes of the affected multiple electrical systems, and compare them with the current nuclear power plant accident conditions to identify the conditions that cannot be covered by the current nuclear power plant accident conditions, and then determine the common cause failure risks of multiple electrical systems caused by the support system.

[0039] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, step S33 comprises:

[0040] Analyze the transients, faults and coordination between different protection devices of the electrical system to obtain the relevant electrical system operating status and protection device action status under each transient and fault condition, identify the conditions that may cause multiple electrical system failures, or the defects in the coordination design between different protection devices that cannot meet the protection requirements of the electrical system, and then determine the common cause failure risks of multiple electrical systems caused by electrical failures.

[0041] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, step S41 comprises:

[0042] According to the characteristics of different types of internal and external disasters in nuclear power plants, one or more rooms in the plant are used as spatial analysis units to analyze the impact of different types of disasters on electrical equipment and electrical systems in multiple rooms, identify the scope and consequences of the disasters, and compare them with the current nuclear power plant accident conditions to identify the scope and consequences of the disasters that cannot be covered by the current nuclear power plant accident conditions, and then determine the common cause failure risks of multiple electrical systems caused by space.

[0043] Preferably, in the method for analyzing common cause failures of an electrical system according to the present invention, step S42 comprises:

[0044] Based on the risk of common cause failures in multiple electrical systems caused by space, determine how to increase the independence between different electrical equipment and different electrical systems through isolation solutions; and / or, determine how to improve the ability of electrical equipment to resist disasters by increasing the requirements for electrical equipment identification.

[0045] The present invention also constructs an analysis system for common cause failures of an electrical system, including an equipment independence analysis module, which includes:

[0046] The engineering analysis unit is used to determine the risk of common cause failures in multiple electrical systems caused by the same electrical equipment through engineering analysis, and to serve as input for accident analysis;

[0047] An accident analysis unit is used to determine the accident consequences of common cause failures in the electrical system through accident analysis;

[0048] The equipment adjustment unit is used to determine diversified adjustment plans for electrical equipment based on the accident consequences of common cause failures in the electrical system.

[0049] By implementing the present invention, the following beneficial effects are achieved:

[0050] The analysis method of common cause failures of electrical systems disclosed in the present invention includes an equipment independence analysis step, which determines a diversified analysis method for electrical equipment and fills a gap in the nuclear power industry at home and abroad.

[0051] At the same time, it also includes at least one of the steps of human-related independence analysis, functional independence analysis and spatial independence analysis, so that the common cause failure risks existing in the electrical system design can be completely and comprehensively identified from all aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0053] Figure 1 It is a schematic diagram of the analysis method of common cause failure of an electrical system of the present invention;

[0054] Figure 2 It is a module block diagram of the analysis system for common cause failures of electrical systems of the present invention. DETAILED DESCRIPTION

[0055] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0056] It should be noted that the flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor do they have to be executed in the order described. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0057] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0058] Definitions of Abbreviations and Key Terms:

[0059] Nuclear power plant: NPP (Nuclear Power Plant), a power plant that uses and converts nuclear energy to produce electricity.

[0060] Defense in Depth: During the design process of a nuclear power plant, through the configuration of different systems at multiple levels, multiple levels of protection barriers are provided for the safe operation and accident handling of the nuclear power plant to ensure the safety of the nuclear power plant and personnel.

[0061] Electrical system: EPS (Electrical Power System), a power system that provides power and control power to medium-voltage and low-voltage equipment in a power plant through the conversion, storage and distribution of electrical energy.

[0062] Common Cause Failure: CCF (Common Cause Failure) is a failure in which several systems, structures and components fail to function due to a specific single event or cause.

[0063] Diversity: Diversity is a method of reducing the possibility of common cause failures between systems and improving system safety by adopting different design solutions for various aspects of common cause failure risks in the system design of different systems.

[0064] Deterministic analysis: Based on engineering experience, it takes assumed common cause failures as the analysis object, determines the safety consequences and response methods of each common cause failure, and thus identifies possible weak links in the existing design.

[0065] Probabilistic analysis: Probabilistic analysis uses probabilistic analysis tools to determine the probability of common cause failures in different systems and equipment, thereby providing data support for the selection of strategies to deal with different common cause failures.

[0066] As Low As Reasonably Possible (ALARP) comprehensively considers the impact of technology, safety, economy and other aspects, and reduces the risk to the lowest possible level through reasonable scheme comparison.

[0067] like Figure 1 As shown, this embodiment discloses a method for analyzing common cause failures of an electrical system, including the steps of analyzing device independence:

[0068] S11: Determine the risk of common cause failures in multiple electrical systems caused by the same electrical equipment through engineering analysis and use it as input for accident analysis;

[0069] S12: Determine the consequences of common cause failures in electrical systems through accident analysis;

[0070] S13: Determine diversified adjustment plans for electrical equipment based on the accident consequences of common cause failures in the electrical system.

[0071] This embodiment determines a diversified analysis method for electrical equipment, filling a gap in the nuclear power industry at home and abroad.

[0072] Based on the above embodiment, the method further includes a human factor-related independence analysis step:

[0073] S21: Through experience feedback, determine the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment, and determine the diversification adjustment plan for personnel. For example, through domestic and foreign experience feedback, determine the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment. Since human-related independence issues are often closely related to electrical equipment, this part of the content will be carried out together with the diversification analysis of electrical equipment, mainly by reducing the application of the same components or electrical equipment in different electrical systems, or adding different operators to reduce the risk of common cause failures.

[0074] Specifically, the independence of equipment and human factors are related to the entire design, production, installation, commissioning, and operation and maintenance of the equipment, so issues in these two aspects can be considered comprehensively.

[0075] The problem of equipment independence is mainly due to the application of the same components or electrical equipment in multiple electrical systems, so that the failure of these components or electrical equipment due to the same reason may cause the failure of multiple electrical systems at the same time.

[0076] The problem of human-related independence is also related to the same components or equipment. When the same operator operates the same component or electrical equipment, the same operating error may cause multiple electrical systems to fail at the same time.

[0077] The main body of equipment and human-related independence analysis is the design of electrical equipment and electrical systems, which is the focus and key part of the common cause failure analysis of electrical systems. Its analysis method follows the principle of As Low As Reasonably Possible (ALARP), and finally evaluates the overall design of the electrical system according to the above equipment independence analysis steps and human-related independence analysis steps.

[0078] Furthermore, step S11 includes:

[0079] By conducting failure mode and failure consequence analysis on electrical equipment in the electrical system, the key components or key electrical equipment that can directly cause the failure of the electrical system and the use of key components or key electrical equipment in multiple electrical systems are determined. For electrical systems with the same key components or key electrical equipment, it is considered that there is a risk of common cause failure, that is, the risk of common cause failure in multiple electrical systems caused by the same key electrical equipment is further determined, and one or more common cause failure groups are set according to the key components or key electrical equipment as input for accident analysis;

[0080] Step S12 includes:

[0081] Taking the common cause failure group determined by engineering analysis as input, the support system failure caused by key electrical equipment is analyzed to determine the accident consequences of common cause failure of electrical system. The analysis of support system failure includes analyzing the impact of failure of single or multiple common support systems, obtaining the accident consequences of multiple affected electrical systems, and comparing them with the current nuclear power plant accident conditions to identify accident consequences that cannot be covered by the current nuclear power plant accident conditions.

[0082] For common cause failures in electrical systems where the consequences of the accident cannot be contained and there are no mitigation measures, it is necessary to modify the design plan through diversified means of key electrical equipment to reduce the risk of this common cause failure and avoid unmitigated accident consequences.

[0083] Accordingly, the device independence analysis step also includes:

[0084] S14: Taking the high frequency accidents in the accident consequences as the starting point and the safety status of the nuclear power plant as the goal, analyze the main defense line and diversified defense line systems required in the process, and determine the diversified adjustment schemes of the electrical systems that power the main defense line and diversified defense line systems, that is, it is necessary to make diversified improvements to the electrical system or modify the distribution design. Among them, the main defense line is the system that directly responds to the corresponding accidents, and the diversified defense line can be regarded as the backup of the main defense line.

[0085] In some embodiments, there may be multiple diversified adjustment schemes for the electrical equipment determined in step S13, and as many as possible, for use in scheme comparison.

[0086] Therefore, the device independence analysis steps also include:

[0087] S15: Based on the determined diversified adjustment schemes for electrical equipment, with reference to the experience feedback data, a comparison is made to obtain the optimal adjustment scheme. Among them, the comparison can be made in five aspects, namely, equipment design diversity, equipment manufacturing diversity, life cycle diversity, logic diversity, and signal diversity, to compare the degree of diversity of each scheme. The higher the score, the higher the degree of diversity. However, in the process of scheme comparison, the maturity and feasibility of the scheme should also be considered. If there are major problems with the maturity and feasibility of a certain scheme, it will not be used as an alternative even if its degree of diversity is high.

[0088] The comparison table of various electrical equipment schemes is shown below. The scheme numbered 1 is generally the original design scheme, which serves as the baseline for scheme comparison.

[0089] Table 1 Comparison of diversified solutions for electrical equipment

[0090]

[0091] In some embodiments, the device independence analysis step further comprises:

[0092] S16: Through the probability analysis method, the common cause failure of a single electrical equipment in the optimal adjustment scheme is used as the modeling object, and its common cause failure probability is calculated to provide a reference for the diversification requirements of electrical equipment. For electrical equipment with a higher probability of failure, a higher diversity needs to be considered to reduce the probability of failure; for electrical equipment with a lower probability of failure, a balanced choice can be considered among multiple schemes.

[0093] In some embodiments, the device independence analysis step further comprises:

[0094] S17: Through ALARP analysis, technical and economic comparisons are made to clarify the impact of various options on the nuclear power plant and all related systems in many aspects, so as to determine the option that reduces the overall common cause failure risk to as low as reasonably practicable (ALARP), that is, the optimal option.

[0095] Specifically, the object of the scheme comparison in this stage is the overall design scheme of the electrical system. Each design scheme is a combination of feasible schemes of various electrical systems determined in the electrical equipment diversification analysis stage. Different combinations mainly represent different diversification levels. The scheme comparison uses ALARP analysis and a more comprehensive technical and economic comparison to clarify the impact of each scheme on the design, procurement, operation and other aspects of the nuclear power plant and all related systems, so as to determine the scheme that reduces the overall risk to a reasonable and feasible level and should consider the lowest (ALARP) for each related profession and each important technical and economic quantity.

[0096] The impact of the overall design scheme selection index of the electrical system, the evaluation items are mainly as follows:

[0097] Safety: Comprehensive consideration of multiple safety factors including nuclear safety, conventional safety and nuclear security;

[0098] Technology: including factors such as system performance, structure, interface, innovation and complexity, and equipment identification;

[0099] Good practices: Consider regulatory standards, experience feedback, reviewer opinions, and experience from previous GDA projects;

[0100] Cost: covers all cost impacts during the design, construction and operation phases.

[0101] Each of the above-mentioned major items needs to be scored according to the evaluation results of its various sub-items. In the process of comparing the overall design scheme of the electrical system, the weight of each evaluation item also needs to be determined, as shown in the following table.

[0102] Table 2 Scoring criteria for the selection and evaluation of the overall design scheme of the electrical system

[0103]

[0104] Through the above scheme comparison, the optimal scheme can be preliminarily determined. It is also necessary to conduct sensitivity analysis by reasonably adjusting the weights of the scores of each major project to determine whether the comparison results will change due to the adjustment of the weights. If the adjustment of the weights does not affect the comparison results, it means that the scheme comparison is not sensitive to the weights, and the optimal scheme can be determined; if the adjustment of the weights affects the comparison results, it is necessary to analyze the major projects that have a greater impact after the weight adjustment to determine whether they can be further optimized to eliminate the impact of the weights on the comparison results.

[0105] After the optimal solution is determined, the electrical system design can be improved based on the differences between the various systems and electrical equipment in the optimal solution and the original design. The scope of improvement may include electrical system structure, equipment selection and identification requirements, etc.

[0106] Based on any of the above embodiments, the method further includes a functional independence analysis step:

[0107] S31: By analyzing the failure of the support system of the electrical system, determine the common cause failure risk of multiple electrical systems caused by the support system;

[0108] S32: Determine diversified adjustment plans for the support system based on the risk of common cause failures in multiple electrical systems caused by the support system;

[0109] S33: Determine the risk of common cause failures in multiple electrical systems caused by electrical failures by analyzing the failures of multiple electrical systems caused by electrical failures themselves;

[0110] S34: Determine the independence adjustment plan of the electrical systems based on the risk of common cause failures in multiple electrical systems caused by electrical factors.

[0111] Specifically, problems with functional independence mainly refer to the failure of multiple electrical systems caused by the failure of the electrical system's support system or the failure of the electrical system itself, resulting in operating conditions that cannot be dealt with by existing accident handling means.

[0112] The identification of this problem mainly comes from two aspects of analysis: one is the analysis of the failure of the support system of the electrical system, and the other is the analysis of the failure of multiple electrical systems caused by the failure of the electrical system itself. The shared functional characteristics are manifested as shared HVAC or instrumentation systems in the support system, and as the same transient or accident characteristics in the electrical system analysis.

[0113] The support systems in a nuclear power plant mainly refer to electrical systems, instrumentation and control systems, HVAC systems, and various fluid systems, which do not directly perform safety functions, but provide various aspects of support to frontier systems that perform safety functions (such as reactor coolant systems, residual heat removal systems, etc.).

[0114] In some embodiments, step S31 further includes: analyzing the impact of the failure of a single or multiple common support systems, obtaining the operating condition changes of the affected multiple electrical systems, and comparing them with the current nuclear power plant accident conditions, identifying the conditions that cannot be covered by the current nuclear power plant accident conditions, and then determining the common cause failure risks of multiple electrical systems caused by the support system.

[0115] For the electrical system, its supporting systems are mainly the HVAC system that ensures environmental conditions and the instrumentation and control system that realizes remote monitoring. By analyzing the consequences of losing the HVAC system and the instrumentation and control system, the impact of their failure on the electrical system can be determined, and then the impact on the frontier system can be judged, so as to identify the conditions that cannot be covered by the existing accident conditions and lack corresponding mitigation measures. For the failure modes of the supporting systems corresponding to these conditions, it is necessary to determine the appropriate improvement plan through improvement item analysis, so as to reduce or eliminate the common cause failure risks brought by these failure modes.

[0116] Since there are electrical connections between electrical systems, when a transient or fault occurs in the external power grid or the plant power system, a single fault may affect multiple electrical systems through the electrical connections.

[0117] In some embodiments, step S33 further includes: analyzing the transient state, faults and coordination between different protection devices of the electrical system, obtaining the relevant electrical system operating state and protection device action status under each transient state and fault condition, identifying the conditions that may cause multiple electrical systems to fail, or the defects in the coordination design between different protection devices that cannot meet the protection requirements of the electrical system, and then determining the common cause failure risks of multiple electrical systems caused by electrical. After identifying these problems, the corresponding electrical system design needs to be improved to reduce or eliminate the common cause failure risks caused by these conditions.

[0118] Based on any of the above embodiments, the method further includes a spatial independence analysis step:

[0119] S41: Determine the risk of common cause failures in multiple electrical systems caused by space through analysis of multiple electrical system failures caused by nuclear power plant disasters;

[0120] S42: Determine the adjustment plan for space independence based on the risk of common cause failures of multiple electrical systems caused by the space.

[0121] Specifically, the problem of spatial independence mainly refers to the failure of multiple electrical systems due to reasons such as electrical equipment layout and electrical equipment identification requirements when internal and external disasters occur, resulting in working conditions that cannot be dealt with by existing accident handling methods.

[0122] In some embodiments, step S41 further includes:

[0123] According to the characteristics of different types of internal and external disasters in nuclear power plants, one or more rooms in the plant are used as spatial analysis units to analyze the impact of different types of disasters on electrical equipment and electrical systems in multiple rooms, identify the scope and consequences of the disasters, and compare them with the current nuclear power plant accident conditions to identify the scope and consequences of the disasters that cannot be covered by the current nuclear power plant accident conditions, and then determine the common cause failure risks of multiple electrical systems caused by space.

[0124] Step S42 further includes:

[0125] Based on the risk of common cause failures in multiple electrical systems caused by space, determine whether to increase the independence of different electrical equipment and different electrical systems through isolation solutions, such as reducing the impact of internal fires by redividing fire partitions or adjusting the layout of electrical equipment; and / or, determine whether to improve the ability of electrical equipment to resist disasters by increasing the identification requirements for electrical equipment, such as increasing the identification requirements for EMI to ensure its availability in extreme space weather conditions.

[0126] It should be noted here that the above-mentioned equipment independence analysis steps, human-related independence analysis steps, functional independence analysis steps, and spatial independence analysis steps can be arbitrarily combined to fully and comprehensively identify the common cause failure risks existing in the electrical system design from all aspects, and the combination of the embodiments of each step will not be elaborated here.

[0127] like Figure 2 As shown, this embodiment also discloses an analysis system for common cause failures of an electrical system, including an equipment independence analysis module, which includes:

[0128] The engineering analysis unit is used to determine the risk of common cause failures in multiple electrical systems caused by the same electrical equipment through engineering analysis, and to serve as input for accident analysis;

[0129] An accident analysis unit is used to determine the accident consequences of common cause failures in the electrical system through accident analysis;

[0130] The equipment adjustment unit is used to determine diversified adjustment plans for electrical equipment based on the accident consequences of common cause failures in the electrical system.

[0131] This embodiment determines a diversified analysis method for electrical equipment, filling a gap in the nuclear power industry at home and abroad.

[0132] On the basis of the above-mentioned embodiments, the system also includes a human-related independence analysis module, which is used to determine the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment through experience feedback, and determine the diversified adjustment plan for personnel. For example, through domestic and foreign experience feedback, the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment is determined. Since human-related independence issues are often closely related to electrical equipment, this part of the content will be carried out together with the diversified analysis of electrical equipment, mainly by reducing the application of the same components or electrical equipment in different electrical systems, or increasing the number of different operators to reduce the risk of common cause failures.

[0133] Specifically, the independence of equipment and human factors are related to the entire design, production, installation, commissioning, and operation and maintenance of the equipment, so issues in these two aspects can be considered comprehensively.

[0134] The problem of equipment independence is mainly due to the application of the same components or electrical equipment in multiple electrical systems, so that the failure of these components or electrical equipment due to the same reason may cause the failure of multiple electrical systems at the same time.

[0135] The problem of human-related independence is also related to the same components or equipment. When the same operator operates the same component or electrical equipment, the same operating error may cause multiple electrical systems to fail at the same time.

[0136] The main body of equipment and human-related independence analysis is the design of electrical equipment and electrical systems, which is the focus and key part of the common cause failure analysis of electrical systems. Its analysis method follows the principle of As Low As Reasonably Possible (ALARP), and finally evaluates the overall design of the electrical system according to the above equipment independence analysis steps and human-related independence analysis steps.

[0137] Furthermore, the engineering analysis unit is further used to determine the key components or key electrical equipment that can directly cause the failure of the electrical system and the use of the key components or key electrical equipment in multiple electrical systems by performing failure mode and failure consequence analysis on the electrical equipment in the electrical system, and for electrical systems with the same key components or key electrical equipment, it is considered that there is a risk of common cause failure, that is, the risk of common cause failure in multiple electrical systems caused by the same key electrical equipment is further determined, and one or more common cause failure groups are set according to the key components or key electrical equipment as input for accident analysis;

[0138] The accident analysis unit is further used to analyze the failure of the support system caused by the key electrical equipment and determine the accident consequences of the common cause failure of the electrical system, taking the common cause failure group determined by the engineering analysis as input. The analysis of the failure of the support system includes analyzing the impact of the failure of a single or multiple common support systems, obtaining the accident consequences of the affected multiple electrical systems, and comparing them with the current nuclear power plant accident conditions to identify the accident consequences that cannot be covered by the current nuclear power plant accident conditions.

[0139] For common cause failures in electrical systems where the consequences of the accident cannot be contained and there are no mitigation measures, it is necessary to modify the design plan through diversified means of key electrical equipment to reduce the risk of this common cause failure and avoid unmitigated accident consequences.

[0140] Accordingly, the device independence analysis module also includes:

[0141] The electrical system adjustment unit of the defense line is used to analyze the main defense line and diversified defense line systems required in the process based on the high-frequency accidents in the accident consequences and the safety status of the nuclear power plant, and determine the diversified adjustment schemes of the electrical systems that power the main defense line and diversified defense line systems, that is, it is necessary to make diversified improvements to the electrical system or modify the distribution design. Among them, the main defense line is the system that directly responds to the corresponding accidents, and the diversified defense line can be regarded as the backup of the main defense line.

[0142] In some embodiments, the diversified adjustment schemes for the electrical equipment determined in the equipment adjustment unit may be multiple, and as many as possible, for use in scheme comparison.

[0143] Therefore, the device independence analysis module also includes:

[0144] The comparison unit is used to compare and select the diversified adjustment schemes of the determined electrical equipment with reference to the experience feedback data to obtain the preferred adjustment scheme. Among them, the comparison can be carried out through five aspects, namely, equipment design diversity, equipment manufacturing diversity, life cycle diversity, logic diversity, and signal diversity, to compare the degree of diversity of each scheme. The higher the score, the higher the degree of diversity. However, in the process of scheme comparison, the maturity and feasibility of the scheme should also be considered. If there are major problems with the maturity and feasibility of a certain scheme, it will not be used as an alternative scheme even if its degree of diversity is high.

[0145] The comparison table of various electrical equipment schemes is shown below. The scheme numbered 1 is generally the original design scheme, which serves as the baseline for scheme comparison.

[0146] Table 1 Comparison of diversified solutions for electrical equipment

[0147]

[0148] In some embodiments, the device independence analysis module further includes:

[0149] The probability analysis unit is used to use the probability analysis method to model the common cause failure of a single electrical device in the optimal adjustment scheme, calculate its common cause failure probability, and provide a reference for the diversification requirements of electrical equipment. For electrical equipment with a higher probability of failure, a higher diversity needs to be considered to reduce the probability of failure; for electrical equipment with a lower probability of failure, a balanced choice can be considered among multiple schemes.

[0150] In some embodiments, the device independence analysis module further includes:

[0151] The optimal solution determination unit is used to make technical and economic comparisons through ALARP analysis to clarify the impact of various solutions on the nuclear power plant and all related systems in many aspects, so as to determine the solution that reduces the overall common cause failure risk to as low as reasonably practicable (ALARP), that is, the optimal solution.

[0152] Specifically, the object of the scheme comparison in this stage is the overall design scheme of the electrical system. Each design scheme is a combination of feasible schemes of various electrical systems determined in the electrical equipment diversification analysis stage. Different combinations mainly represent different diversification levels. The scheme comparison uses ALARP analysis and a more comprehensive technical and economic comparison to clarify the impact of each scheme on the design, procurement, operation and other aspects of the nuclear power plant and all related systems, so as to determine the scheme that reduces the overall risk to a reasonable and feasible level and should consider the lowest (ALARP) for each related profession and each important technical and economic quantity.

[0153] The impact of the overall design scheme selection index of the electrical system, the evaluation items are mainly as follows:

[0154] Safety: Comprehensive consideration of multiple safety factors including nuclear safety, conventional safety and nuclear security;

[0155] Technology: including factors such as system performance, structure, interface, innovation and complexity, and equipment identification;

[0156] Good practices: Consider regulatory standards, experience feedback, reviewer opinions, and experience from previous GDA projects;

[0157] Cost: covers all cost impacts during the design, construction and operation phases.

[0158] Each of the above-mentioned major items needs to be scored according to the evaluation results of its various sub-items. In the process of comparing the overall design scheme of the electrical system, the weight of each evaluation item also needs to be determined, as shown in the following table.

[0159] Table 2 Scoring criteria for the selection and evaluation of the overall design scheme of the electrical system

[0160]

[0161]

[0162] Through the above scheme comparison, the optimal scheme can be preliminarily determined. It is also necessary to conduct sensitivity analysis by reasonably adjusting the weights of the scores of each major project to determine whether the comparison results will change due to the adjustment of the weights. If the adjustment of the weights does not affect the comparison results, it means that the scheme comparison is not sensitive to the weights, and the optimal scheme can be determined; if the adjustment of the weights affects the comparison results, it is necessary to analyze the major projects that have a greater impact after the weight adjustment to determine whether they can be further optimized to eliminate the impact of the weights on the comparison results.

[0163] After the optimal solution is determined, the electrical system design can be improved based on the differences between the various systems and electrical equipment in the optimal solution and the original design. The scope of improvement may include electrical system structure, equipment selection and identification requirements, etc.

[0164] Based on any of the above embodiments, the system further includes a functional independence analysis module, which includes:

[0165] A support system analysis unit, used to determine the common cause failure risk of multiple electrical systems caused by the support system by analyzing the failure of the support system of the electrical system;

[0166] A support system adjustment unit, used for determining diversified adjustment schemes of the support system according to the common cause failure risks existing in multiple electrical systems caused by the support system;

[0167] An electrical system analysis unit, used to determine the risk of common cause failures of multiple electrical systems caused by electrical failures by analyzing the failures of multiple electrical systems caused by the electrical system itself;

[0168] The electrical system adjustment unit is used to determine the independence adjustment plan of the electrical system according to the common cause failure risk existing in multiple electrical systems caused by electrical factors.

[0169] Specifically, problems with functional independence mainly refer to the failure of multiple electrical systems caused by the failure of the electrical system's support system or the failure of the electrical system itself, resulting in operating conditions that cannot be dealt with by existing accident handling means.

[0170] The identification of this problem mainly comes from two aspects of analysis: one is the analysis of the failure of the support system of the electrical system, and the other is the analysis of the failure of multiple electrical systems caused by the failure of the electrical system itself. The shared functional characteristics are manifested as shared HVAC or instrumentation systems in the support system, and as the same transient or accident characteristics in the electrical system analysis.

[0171] The support systems in a nuclear power plant mainly refer to electrical systems, instrumentation and control systems, HVAC systems, and various fluid systems, which do not directly perform safety functions, but provide various aspects of support to frontier systems that perform safety functions (such as reactor coolant systems, residual heat removal systems, etc.).

[0172] In some embodiments, the support system analysis unit is further used to analyze the impact of the failure of a single or multiple common support systems, obtain the operating condition changes of the affected multiple electrical systems, and compare them with the current nuclear power plant accident conditions, identify the conditions that cannot be covered by the current nuclear power plant accident conditions, and then determine the common cause failure risks of multiple electrical systems caused by the support system.

[0173] For the electrical system, its supporting systems are mainly the HVAC system that ensures environmental conditions and the instrumentation and control system that realizes remote monitoring. By analyzing the consequences of losing the HVAC system and the instrumentation and control system, the impact of their failure on the electrical system can be determined, and then the impact on the frontier system can be judged, so as to identify the conditions that cannot be covered by the existing accident conditions and lack corresponding mitigation measures. For the failure modes of the supporting systems corresponding to these conditions, it is necessary to determine the appropriate improvement plan through improvement item analysis, so as to reduce or eliminate the common cause failure risks brought by these failure modes.

[0174] Since there are electrical connections between electrical systems, when a transient or fault occurs in the external power grid or the plant power system, a single fault may affect multiple electrical systems through the electrical connections.

[0175] In some embodiments, the electrical system analysis unit is further used to analyze the transient state, faults and coordination between different protection devices of the electrical system, obtain the relevant electrical system operating state and protection device action status under each transient state and fault condition, identify the conditions that may cause multiple electrical systems to fail, or the defects in the coordination design between different protection devices that cannot meet the electrical system protection requirements, and then determine the common cause failure risks of multiple electrical systems caused by electrical. After identifying these problems, the corresponding electrical system design needs to be improved to reduce or eliminate the common cause failure risks caused by these conditions.

[0176] Based on any of the above embodiments, the system further includes a spatial independence analysis module, which includes:

[0177] A spatial analysis unit, which is used to determine the risk of common cause failures of multiple electrical systems caused by space through analysis of multiple electrical system failures caused by nuclear power plant disasters;

[0178] The space adjustment unit is used to determine an adjustment plan for space independence according to the common cause failure risk existing in multiple electrical systems caused by the space.

[0179] Specifically, the problem of spatial independence mainly refers to the failure of multiple electrical systems due to reasons such as electrical equipment layout and electrical equipment identification requirements when internal and external disasters occur, resulting in working conditions that cannot be dealt with by existing accident handling methods.

[0180] In some embodiments, the spatial analysis unit is further used to analyze the impact of different types of disasters on electrical equipment and electrical systems in multiple rooms based on the characteristics of different types of internal and external disasters in the nuclear power plant, using one or more rooms in the plant as spatial analysis units, identifying the scope and consequences of the disasters, and comparing them with the current nuclear power plant accident conditions, identifying the scope and consequences of the disasters that cannot be covered by the current nuclear power plant accident conditions, and then determining the common cause failure risks of multiple electrical systems caused by space.

[0181] The space adjustment unit is further used to determine, based on the risk of common cause failures in multiple electrical systems caused by the space, to increase the independence between different electrical equipment and different electrical systems through isolation schemes, such as reducing the impact of internal fires by redividing fire partitions or adjusting the layout of electrical equipment; and / or, to determine to improve the ability of electrical equipment to resist disasters by increasing the identification requirements for electrical equipment, such as increasing the identification requirements for EMI to ensure its availability in extreme space weather conditions.

[0182] It should be noted here that the above-mentioned equipment independence analysis module, human factor-related independence analysis module, functional independence analysis module, and spatial independence analysis module can be arbitrarily combined to fully and comprehensively identify the common cause failure risks existing in the electrical system design from all aspects, and the combination of the embodiments of each module will not be elaborated here.

[0183] By implementing the present invention, the following beneficial effects are achieved:

[0184] The analysis method of common cause failures of electrical systems disclosed in the present invention includes an equipment independence analysis step, which determines a diversified analysis method for electrical equipment and fills a gap in the nuclear power industry at home and abroad.

[0185] At the same time, it also includes at least one of the steps of human-related independence analysis, functional independence analysis and spatial independence analysis, so that the common cause failure risks existing in the electrical system design can be completely and comprehensively identified from all aspects.

[0186] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A method for analyzing common cause failures in an electrical system, characterized in that: The equipment independence analysis steps include: S11: Determine the risk of common cause failures in multiple electrical systems caused by the same electrical equipment through engineering analysis and use it as input for accident analysis; S12: Determine the consequences of common cause failures in electrical systems through accident analysis; S13: Determine diversified adjustment plans for electrical equipment based on the accident consequences of common cause failures in the electrical system; Wherein, step S11 comprises: By performing failure mode and failure consequence analysis on electrical equipment in the electrical system, the key electrical equipment that can directly cause failure of the electrical system and the use of the key electrical equipment in multiple electrical systems are determined, and then the common cause failure risk of multiple electrical systems caused by the same key electrical equipment is determined, and one or more common cause failure groups are set according to the key electrical equipment as input for accident analysis; Step S12 includes: Using the common cause failure groups determined by the engineering analysis as input, analyze the failure of the support system caused by the key electrical equipment to determine the accident consequences of the common cause failure of the electrical system; This method also includes the steps of human-related independence analysis: S21: Determine the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment through experience feedback, and determine the diversified adjustment plan for personnel; The method also includes a functional independence analysis step: S31: By analyzing the failure of the support system of the electrical system, determine the common cause failure risk of multiple electrical systems caused by the support system; S32: Determine diversified adjustment plans for the support system based on the risk of common cause failures in multiple electrical systems caused by the support system; S33: Determine the risk of common cause failures in multiple electrical systems caused by electrical failures by analyzing the failures of multiple electrical systems caused by electrical failures themselves; S34: Determine the independence adjustment plan of the electrical system based on the common cause failure risk of multiple electrical systems caused by electrical failure; This method also includes a spatial independence analysis step: S41: Determine the risk of common cause failures in multiple electrical systems caused by space through analysis of multiple electrical system failures caused by nuclear power plant disasters; S42: Determine the adjustment plan for space independence based on the risk of common cause failures of multiple electrical systems caused by the space.

2. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: The device independence analysis step further includes: S14: Taking the high-frequency accidents in the accident consequences as the starting point and the safe state of the nuclear power plant as the goal, analyze the main defense line and diversified defense line systems required in the process, and determine the diversified adjustment plans for the electrical systems that power the main defense line and diversified defense line systems.

3. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: The device independence analysis step further comprises: S15: Based on the determined diversified adjustment plans for the electrical equipment, with reference to the experience feedback data, comparison is performed to arrive at the optimal adjustment plan.

4. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: The device independence analysis step further includes: S16: Through the probabilistic analysis method, the common cause failure of a single electrical equipment in the optimal adjustment plan is taken as the modeling object, and its common cause failure probability is calculated to provide a reference for the diversification requirements of the electrical equipment.

5. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: The device independence analysis step further includes: S17: Through ALARP analysis, technical and economic comparisons are made to clarify the impact of each option on the nuclear power plant and all related systems in many aspects, and then determine the option that reduces the overall common cause failure risk to as low as reasonably practicable (ALARP).

6. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: Step S31 includes: Analyze the impact of the failure of a single or multiple shared support systems, obtain the operating condition changes of the affected multiple electrical systems, and compare them with the current nuclear power plant accident conditions to identify the conditions that cannot be covered by the current nuclear power plant accident conditions, and then determine the common cause failure risks of multiple electrical systems caused by the support system.

7. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: Step S33 includes: Analyze the transients, faults and coordination between different protection devices of the electrical system to obtain the relevant electrical system operating status and protection device action status under each transient and fault condition, identify the conditions that may cause multiple electrical system failures, or the defects in the coordination design between different protection devices that cannot meet the protection requirements of the electrical system, and then determine the common cause failure risks of multiple electrical systems caused by electrical failures.

8. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: Step S41 includes: According to the characteristics of different types of internal and external disasters in nuclear power plants, one or more rooms in the plant are used as spatial analysis units to analyze the impact of different types of disasters on electrical equipment and electrical systems in multiple rooms, identify the scope and consequences of the disasters, and compare them with the current nuclear power plant accident conditions to identify the scope and consequences of the disasters that cannot be covered by the current nuclear power plant accident conditions, and then determine the common cause failure risks of multiple electrical systems caused by space.

9. The method for analyzing common cause failures of an electrical system according to claim 1, characterized in that: Step S42 includes: Based on the risk of common cause failures in multiple electrical systems caused by space, determine how to increase the independence between different electrical equipment and different electrical systems through isolation; and / or, determine how to improve the ability of electrical equipment to resist disasters by increasing the requirements for electrical equipment identification.

10. An analysis system for common cause failures in electrical systems, characterized in that: Includes a device independence analysis module, which includes: The engineering analysis unit is used to determine the risk of common cause failures in multiple electrical systems caused by the same electrical equipment through engineering analysis, and to serve as input for accident analysis; An accident analysis unit is used to determine the accident consequences of common cause failures in the electrical system through accident analysis; Equipment adjustment unit, used to determine diversified adjustment plans for electrical equipment according to the accident consequences of common cause failures in the electrical system; The engineering analysis unit is further used to determine the key electrical equipment that can directly cause the failure of the electrical system and the use of the key electrical equipment in multiple electrical systems by performing failure mode and failure consequence analysis on the electrical equipment in the electrical system, thereby determining the common cause failure risk of multiple electrical systems caused by the same key electrical equipment, and setting one or more common cause failure groups according to the key electrical equipment as input for accident analysis; The accident analysis unit is further used to analyze the failure of the support system caused by the key electrical equipment using the common cause failure group determined by the engineering analysis as input, and determine the accident consequences of the common cause failure of the electrical system; The system also includes a human-related independence analysis module, which is used to determine the role of human factors in the risk of common cause failures in multiple electrical systems caused by the same equipment through experience feedback, and to determine the diversified adjustment plan for personnel; The system also includes a functional independence analysis module, which includes: A support system analysis unit, used to determine the common cause failure risk of multiple electrical systems caused by the support system by analyzing the failure of the support system of the electrical system; A support system adjustment unit, used for determining diversified adjustment schemes of the support system according to the common cause failure risks existing in multiple electrical systems caused by the support system; An electrical system analysis unit, used to determine the risk of common cause failures of multiple electrical systems caused by electrical failures by analyzing the failures of multiple electrical systems caused by the electrical system itself; An electrical system adjustment unit, used to determine an independent adjustment plan for the electrical system according to the risk of common cause failures existing in multiple electrical systems caused by electrical failures; The system also includes a spatial independence analysis module, which includes: A spatial analysis unit, which is used to determine the risk of common cause failures of multiple electrical systems caused by space through analysis of multiple electrical system failures caused by nuclear power plant disasters; The space adjustment unit is used to determine an adjustment plan for space independence according to the common cause failure risk existing in multiple electrical systems caused by the space.

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