Electrical fire risk assessment method and system suitable for low-voltage cable in long and narrow space

Abstract

The invention discloses an electrical fire risk assessment method and system suitable for a low-voltage cable in a long and narrow space. The method comprises the following steps: determining risk factors influencing the electrical fire of the low-voltage cable in the long and narrow space; constructing a fire risk assessment index system, determining the weight of the index system, and obtaining the influence degree of the assessment index on the electrical fire risk; setting initial parameters; constructing a probability model of fire occurrence as a fitness function; according to the direction of the narrow and long space low-voltage cable, the fire risk optimization is continuously repeated until the target fitness and stability are achieved, the convergence condition is achieved, the evaluation index corresponding to the optimal electrical fire state is obtained, the evaluation index with the high numerical value is the most dangerous electrical fire factor, and the evaluation accuracy and comprehensiveness can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical fire in narrow and long spaces, and specifically provides a method and system for evaluating the electrical fire risk of low-voltage cables in narrow and long spaces. Background Art

[0002] In narrow and long spaces, such as traffic tunnels, urban utility tunnels, and underground pedestrian passages, due to space limitations and increasing electricity demand, the safe operation of low-voltage distribution systems is particularly important. However, various factors such as harmonic problems, short circuits, and leakage in low-voltage distribution systems can all trigger electrical fires, causing huge losses to the lives and property of the country and the people. Once a fire occurs in a narrow and confined space, it is difficult to evacuate internally, and it is extremely easy to cause mass casualty fire accidents.

[0003] Due to the complex and variable nature of electrical fires, there are currently many advanced warning systems. For example, although the early fire warning algorithm based on deep learning has high accuracy, its design and implementation process are relatively complex, the technical implementation difficulty is large, and it requires a large amount of data support and complex calculation models. For example, the electrical fire warning system based on the CAN bus has the advantages of strong anti-interference ability and good real-time performance, but its initial investment is large, and the design and implementation complexity of the system is relatively high. The artificial fish swarm algorithm has significant advantages in the evaluation of electrical fires in low-voltage cables. Its global search ability, flexibility, simplicity of code structure and easy extensibility, as well as high solution accuracy and optimization success rate, make it an effective tool for solving complex electrical fire problems.

[0004] In the prior art, the invention patent with the publication number CN105138857A discloses a method for evaluating the explosion risk of liquefied gas storage tanks in a fire environment. In this patent, when the fisherman's fishing operation moves and searches, several points are randomly selected in the optimization space, and then cubes are constructed with each point as the center. The global optimal solution can be obtained through independent movement and contraction searches. However, this blind search takes a long time and is not applicable to electrical fires in low-voltage cables in narrow and long spaces. Fires in narrow and long spaces start quickly, and in this patent, the coupling between fire risk factors in the search is not considered. The occurrence of electrical fires does not exist alone, and the occurrence of multiple risk factors will lead to more serious accidents. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for evaluating the electrical fire risk of low-voltage cables in narrow and long spaces.

[0006] To solve the above technical problem, the present invention provides the following technical solutions: A method for evaluating the electrical fire risk of low-voltage cables in narrow and long spaces, including: S123. Determine the risk factors affecting the electrical fire of low-voltage cables in narrow spaces; S40. Construct a fire risk assessment index system, determine the weights of the index system, and obtain the influence degree of the assessment indexes on the electrical fire risk; S50. Set initial parameters, determine the number of risk factors, set the value range of the assessment indexes, and the moving step size; S60. Construct a probability model of fire occurrence as a fitness function to measure the quality of the electrical fire risk state; S70. Conduct a directional search according to the low-voltage cable layout in the narrow space, including: finding fire risk factors, within the value range of the assessment indexes, finding a state with a higher fitness value, moving towards this state as the risk center point; judging the relevance with surrounding positions, when comparing the fitness value of this risk center point with other risk center points within the surrounding range is higher, then move towards this risk center point; comparing the risk levels, when comparing the fitness value of this risk center point with other points within the surrounding range is the highest, then move towards this point; S80. Continuously repeat step S70 until the target fitness is reached and stabilized, reaching the convergence condition, obtaining the assessment indexes corresponding to the optimal electrical fire state, and the assessment indexes with higher values are the most dangerous electrical fire factors.

[0007] In an embodiment of the present invention, in step S40, constructing a fire risk assessment index system includes setting electrical equipment indexes, installation environment indexes, and narrow space indexes, and scoring the electrical equipment indexes, installation environment indexes, and narrow space indexes; wherein, the electrical equipment indexes include the degree of insulation aging of low-voltage cables, the degree of damage to the insulation layer of low-voltage cables, the overload risk coefficient of low-voltage cables, and the probability of overheating of low-voltage cable joints; the installation environment indexes include environmental temperature and environmental humidity; the narrow space indexes include the aspect ratio coefficient of the narrow space, the height-to-width ratio of the narrow space, and the failure of the ventilation system in the narrow space.

[0008] In an embodiment of the present invention, determining the weights of the index system includes: Establish a hierarchical structure model: regard the assessment of electrical fire risk as the target layer, regard electrical equipment factors, installation environment factors, and narrow space factors as the criterion layer, and each factor index as the index layer; Construct a judgment matrix: through expert scoring, compare the importance of each factor in the same layer with respect to a certain factor in the upper layer pairwise, and construct a judgment matrix; Calculate the weight vector: by calculating the maximum eigenvalue and the corresponding eigenvector of the judgment matrix, obtain the weight vector of each layer factor with respect to the upper layer factor; Consistency test: calculate the consistency index and the consistency ratio, and conduct a consistency test to ensure the rationality of the judgment matrix; Calculate the comprehensive evaluation value according to the scores and weights of the electrical equipment indicators, installation environment indicators, and narrow and long space indicators, and determine the electrical fire risk level of the low-voltage cable in the narrow and long space according to the size of the comprehensive evaluation value.

[0009] In an embodiment of the present invention, the formula for the comprehensive evaluation value is as follows:

[0010] In the formula, is the comprehensive evaluation value, is the score of the th electrical equipment indicator, is the weight of the th electrical equipment indicator, is the score of the th installation environment indicator, is the weight of the th installation environment indicator, is the score of the th narrow and long space indicator, is the weight of the th narrow and long space indicator.

[0011] In an embodiment of the present invention, the probability model of fire occurrence is the following formula: ; In the formula, is the probability of fire occurrence, is the comprehensive evaluation value, is the natural constant.

[0012] In an embodiment of the present invention, finding fire risk factors includes: Set as the fitness function of the position ; The current position of the th risk factor, randomly generate a new position within the value range of the evaluation index, and construct an information matrix E for the new position, denoted by ; and simultaneously record the information matrix of the positions it has searched; where is the information of the installation environment risk factor and the narrow and long space risk factor; If the fitness value of the new position is greater than the fitness value of the initial position, then the risk factor with fire risk is found; If the above conditions are not met, then according to the information in the information matrix, preferentially conduct a directional search towards the previously searched high-fitness value area and in line with the fire risk factor propagation direction; Define the directional search direction vector , set the search step size as , starting from the current position , search in the direction of . After each search, calculate the fitness value of the new position , and update the information matrix E until the search in this area ends, obtaining the point with the highest fitness value in this area , which is used as the danger center point, and this point is the risk factor in this area.

[0013] In an embodiment of the present invention, judging the relevance with surrounding positions includes: Taking the th risk factor as the center, determine the radius of the circular area according to the number of risk factors existing in each evaluation partition . Within the search range, identify and collect other risk factors and their corresponding fitness values; If it is found that the fitness value of the central position of other risk factors within the circular area is higher than the current risk factor, automatically expand the search range, and the current risk factor moves closer to the central position of other risk factors.

[0014] In an embodiment of the present invention, the radius is obtained through the following formula: ; In the formula, is the basic coefficient, is the number of risk factors existing in the evaluation partition, is the length of the narrow space, is the width of the narrow space, is the total length of the low-voltage cable, is the reference cable length.

[0015] In an embodiment of the present invention, automatically expanding the search range includes: Assume that there exists a certain such that P , then expand the search range by β, and the new radius , and update the search area ; where β is the expansion coefficient, 0 < β < 1; The moving method for the current risk factor to move closer to the central position of other risk factors is ; where is the approaching coefficient, .

[0016] The present invention also provides a low-voltage cable electrical fire risk assessment system applicable to narrow and long spaces, which applies the low-voltage cable electrical fire risk assessment method applicable to narrow and long spaces as described above, and includes: A risk factor module for determining the risk factors affecting the electrical fire of low-voltage cables in narrow and long spaces; An index system module for constructing a fire risk assessment index system, determining the weights of the index system, and obtaining the influence degree of the assessment index on the electrical fire risk; An initial module for setting initial parameters, determining the number of risk factors, setting the value range of the assessment index, and setting the search radius; A fitness module for constructing a probability model of fire occurrence as a fitness function to measure the quality of the electrical fire risk state; An electrical fire risk optimization module for directional search according to the low-voltage cable layout in narrow and long spaces, including: searching for fire risk factors, finding a state with a higher fitness value within the value range of the assessment index, and moving towards this state as the risk center point; judging the relevance with surrounding positions, and moving towards this risk center point when the fitness value of this risk center point is higher than that of other risk center points within the surrounding range; comparing the risk levels, and moving towards this point when the fitness value of this risk center point is the highest among other points within the surrounding range; An electrical fire factor module for continuously repeating the steps in the electrical fire risk optimization module until the target fitness is reached and stabilized, reaching the convergence condition, obtaining the assessment index corresponding to the optimal electrical fire state, and the assessment index with a higher value is the most dangerous electrical fire factor.

[0017] Compared with the prior art, the beneficial effects of the present invention are: During the search for fire risk factors, directional search is carried out according to the low-voltage cable layout, avoiding the time of blind search and the constraints of searching for specific scenarios in narrow and long spaces. At the same time, an information matrix is constructed to record the information of each search, so that subsequent searches are more targeted. During the process of searching for fire risk factors, a directional matrix search method is set according to the characteristics of narrow and long spaces, and the search method is more in line with this specific scenario of narrow and long spaces.

[0018] During the search, the coupling of fire risk factors is emphasized. Since the occurrence of electrical fires does not exist alone, the occurrence of multiple risk factors will lead to more serious accidents. In the associated analysis of surrounding risk factors, when determining the search radius, specific factors of narrow and long spaces are considered to correct the search radius. At the same time, a formula for judging mutual influence is established. When there are high-fitness risk factors around, the search range can be automatically expanded and the risk factors can be made to approach each other to accurately find out the factors that jointly affect the electrical fire risk.

[0019] When setting parameters, in combination with the previous identification of electrical fire risk factors, the search range is adjusted according to the different risk factors existing in different evaluation zones, so as to more accurately identify the risk factors existing in each zone.

[0020] Through the numerical value of the most dangerous factor or the comprehensive numerical value of multiple factors identified in each evaluation zone, compare the numerical values of each zone, identify the most dangerous zone in the entire cable zone for implementing later preventive measures, and at the same time carry out targeted prevention for the coupled risk factors existing in each zone. Brief Description of the Drawings

[0021] Figure 1 It is a flowchart of a method for evaluating the electrical fire risk of low-voltage cables in a narrow and long space according to an embodiment of the present invention.

[0022] Figure 2 It is a flowchart block diagram of a method for evaluating the electrical fire risk of low-voltage cables in a narrow and long space according to an embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram of a narrow and long space according to an embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram of a perspective narrow and long space according to an embodiment of the present invention.

[0025] Figure 5 It is a block diagram of a system for evaluating the electrical fire risk of low-voltage cables in a narrow and long space according to an embodiment of the present invention. Detailed Embodiments

[0026] To facilitate the understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will be further described below with reference to the accompanying drawings of the specification.

[0027] The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more, unless otherwise specifically defined.

[0028] Please refer to Figure 1 and Figure 2 As shown, the present invention provides a method for evaluating the electrical fire risk of low-voltage cables in a narrow and long space, including: S123, determining the risk factors affecting the electrical fire of low-voltage cables in the narrow and long space.

[0029] In this embodiment, determining the risk factors affecting the electrical fire of low-voltage cables in the narrow and long space includes steps S10 to S30.

[0030] In this embodiment, S10: Obtain the basic information of the narrow space and the low-voltage cable information within the narrow space.

[0031] Please refer to Figure 3 and Figure 4 As shown, in an embodiment of the present invention, measure the total length , width and height of the narrow space 10 to ensure accurate data and provide a basis for reasonably dividing the evaluation zones. Figure 4 The reference numerals 11, 12, 13, 14, and 15 in [[ ]] represent multiple evaluation zones. Determine the type, specification, and length of the low-voltage cable 20. According to detection devices such as current transformers, monitor the operating status and environmental parameters of the low-voltage cable in real time, and record the load conditions of the low-voltage cable 20, including information such as the current magnitude and load power at present. Use the temperature sensor 31 and humidity sensor 32 to measure the temperature and humidity within the narrow space 10, and check the performance of the ventilation port 40 facilities to evaluate the ventilation situation.

[0032] S20: Evenly divide the low-voltage cables within the narrow space into several evaluation zones according to the total length of the narrow space.

[0033] S30: Conduct a comprehensive inspection of each link in the several evaluation zones and classify the risk factors.

[0034] In an embodiment of the present invention, identification of electrical fire risk factors for low-voltage cables in narrow spaces: For the low-voltage cables in each evaluation zone, conduct a comprehensive inspection of each of its links. Check the type of electrical equipment and record its operating status, whether there are phenomena such as abnormal heating and noise. Consider the installation environment and check whether there are situations such as dampness and corrosion. Focus on potential risk factors such as wire aging, overload operation, short-circuit faults, poor grounding, and high-temperature environments. Also, consider the situation of the narrow space itself, and classify the risk factors including electrical risk factors, installation environment risk factors, and narrow space risk factors S40: Construct a fire risk assessment index system, determine the weights of the index system, and obtain the influence degree of the evaluation index on the electrical fire risk.

[0035] In an embodiment of the present invention, in combination with the classification of risk factors, construct a fire risk assessment index system, including: setting electrical equipment indicators, installation environment indicators, and narrow space indicators, and score the electrical equipment indicators, installation environment indicators, and narrow space indicators.

[0036] In this embodiment, the electrical equipment indicators include the degree of low-voltage cable insulation aging, the degree of damage to the low-voltage cable insulation layer, the overload risk coefficient of the low-voltage cable, and the probability of overheating of the low-voltage cable joints. The installation environment indicators include the ambient temperature and the ambient humidity. The narrow space indicators include the aspect ratio coefficient of the narrow space, the ratio of the height to the width of the narrow space, and the failure of the ventilation system in the narrow space.

[0037] In this embodiment, S41, Degree of low-voltage cable insulation aging : Severe insulation aging will cause a significant decline in the insulation performance of the low-voltage cable. In a narrow space, the aging insulation layer is more likely to experience leakage, short circuit, etc., greatly increasing the risk of electrical fire. The heat of the aging low-voltage cable is not easily dissipated in a narrow space, which will greatly increase the risk of electrical fire.

[0038] Scoring criteria: The insulation state is good, without obvious aging signs, score 0 - 3 points, safe; Slight insulation aging appears in some areas, and the area ratio is less than 10%, score 4 - 7 points, there is a risk; Severe insulation aging appears in some areas, and the area exceeds 10%, score 8 - 10 points, dangerous.

[0039] S42, Degree of damage to the low-voltage cable insulation layer : After the insulation layer is damaged, the exposed conductor is directly exposed in the space, forming a short-circuit path. In a narrow space, the arc and high-temperature heat generated by the short circuit will quickly accumulate, and a fire may be triggered within a short time. The higher the degree of damage, the greater the possibility and danger of causing a fire.

[0040] Scoring criteria: The insulation layer has only slight damage, and the damaged area ratio is less than 5%: score 0 - 3 points, safe; The damaged area ratio of the insulation layer is between 5% - 10%: score 4 - 7 points, there is a risk; The damaged area ratio of the insulation layer is greater than 10%: score 8 - 10 points, dangerous.

[0041] S43, Overload risk coefficient of low-voltage cable ; In a narrow space, when the low-voltage cable is overloaded, due to the poor ventilation conditions in the space, the heat is difficult to dissipate quickly. The heat generated by the overload will continuously accumulate in the narrow space. The higher the overload risk coefficient, the easier it is to exceed the allowable temperature of the low-voltage cable, accelerating insulation aging and inducing fire, greatly increasing the danger of electrical fire.

[0042] Scoring criteria: The current in each area is within the rated load range, score 0 - 3 points, safe; There is slight overload in some areas, with the current exceeding the rated load by less than 10%, scoring 4 - 7 points, and there is a risk. There is severe overload in some areas, with the current exceeding the rated load by more than 10%, scoring 8 - 10 points, dangerous.

[0043] S44, Probability of overheating of low - voltage cable joints : The joint is a relatively weak link in the low - voltage cable. In a narrow space, the heat at the joint is difficult to dissipate, and the probability of overheating will increase significantly. Once the joint overheats, it is easy to cause damage to the insulation layer, triggering a fire in the low - voltage cable. Moreover, in a narrow space, the fire is likely to spread rapidly and is difficult to control.

[0044] Scoring criteria: The joint temperature is normal, with the temperature difference from the ambient temperature less than 10°C: scoring 0 - 3 points, safe; There are slight signs of overheating at the joint, with the temperature difference between 10 - 20°C: scoring 4 - 7 points, there is a risk; The joint is severely overheated, with the temperature difference greater than 20°C: scoring 8 - 10 points, dangerous.

[0045] S45, Ambient temperature index : When the ambient temperature is high, the temperature of the low - voltage cable itself will also rise. In a narrow space, the heat accumulation is more obvious. When the ambient temperature approaches or exceeds the allowable operating temperature of the low - voltage cable, it will accelerate the insulation aging and softening of the insulation layer, reduce the insulation performance, and increase the probability of fire.

[0046] Scoring criteria: The temperature is between the lower limit and 70% of the upper limit of the safe operating range of the equipment: scoring 0 - 3 points, safe; The temperature is between 70% and 90% of the upper limit of the safe operating range of the equipment: scoring 4 - 7 points, there is a risk; The temperature is above 90% of the upper limit of the safe operating range of the equipment: scoring 8 - 10 points, dangerous.

[0047] S46, Ambient humidity index : A high - humidity environment will affect the insulation performance of the low - voltage cable. In a narrow space, the wet insulation layer is more likely to have a leakage phenomenon. At the same time, moisture will accelerate the corrosion of the low - voltage cable, reducing its mechanical strength. When encountering overload, short - circuit and other situations, it is easy to trigger a fire.

[0048] Scoring criteria: The humidity is between the lower limit and 60% of the upper limit of the safe operating range of the equipment: scoring 0 - 3 points, safe; The humidity is between 60% and 80% of the upper limit of the safe operating range of the equipment: scoring 4 - 7 points, there is a risk; Humidity is above 80% of the upper limit of the safe operating range of the equipment: Score 8 - 10 points, dangerous; S47, Aspect ratio coefficient index of narrow and long space : When the aspect ratio coefficient of the narrow and long space is relatively large, the heat dissipation path of the low-voltage cable is restricted, the heat is unevenly distributed in the space, and it is easy to accumulate in some parts, increasing the risk of local overheating of the low-voltage cable, thus increasing the risk of electrical fire.

[0049] Scoring criteria: When the aspect ratio is less than 2:1, the space ventilation and heat dissipation are good, and the equipment operates relatively safely. Score 0 - 3 points, safe; When the aspect ratio is between 2:1 and 3:1, the ventilation and heat dissipation will be affected to a certain extent, which may increase the burden and failure risk of equipment operation. Score 4 - 7 points, there is a risk; When the aspect ratio is greater than 3:1, the space ventilation and heat dissipation are seriously poor, and the equipment operation faces greater risks. Score 8 - 10 points, dangerous.

[0050] S48, Ratio of height to width of narrow and long space : In a narrow and long space with an unreasonable ratio of height to width, the air circulation and heat dissipation will be affected. If the ratio is small, the air circulation is not smooth, and the heat dissipated by the low-voltage cable is difficult to discharge, which will keep the low-voltage cable in a high-temperature state for a long time, increasing the fire risk.

[0051] When the ratio of height to width is greater than 0.5, the space is relatively open, which is conducive to the installation and operation of the equipment. Score 0 - 3 points, safe; When the ratio of height to width is between 0.3 and 0.5, the space is relatively narrow, which will have an adverse impact on aspects such as equipment heat dissipation and maintenance. Score 4 - 7 points, there is a risk; When the ratio of height to width is less than 0.3, the space is extremely narrow, and the equipment operating environment is extremely harsh. Score 8 - 10 points, dangerous.

[0052] S49, Failure of the ventilation system in narrow and long space : The ventilation system is an important way to discharge the heat generated during the operation of the low-voltage cable. In a narrow and long space, once the ventilation system fails, the heat cannot be discharged in time, the low-voltage cable will continue to heat up, accelerating the insulation aging, increasing the risk of electrical fire, and because the space is narrow, the smoke and toxic gases generated by the fire are also difficult to quickly discharge, which will pose a serious threat to the safety of personnel's lives.

[0053] Scoring criteria: The ventilation system operates normally without failure: 0 - 3 points, safe; The ventilation system occasionally fails and can be repaired in time: 4 - 7 points, there is a risk; The ventilation system frequently malfunctions and cannot ventilate effectively: 8 - 10 points, dangerous.

[0054] In an embodiment of the present invention, determining the weights of the index system includes: S410, establishing a hierarchical structure model: Regarding the electrical fire risk assessment as the target layer, regarding electrical equipment factors, installation environment factors, and narrow space factors as the criterion layer, and each factor index as the index layer.

[0055] In this embodiment, the electrical equipment factors are the degree of low - voltage cable insulation aging, the degree of damage to the low - voltage cable insulation layer, the overload risk coefficient of the low - voltage cable, and the probability of overheating of the low - voltage cable joints. The installation environment factors are the ambient temperature and ambient humidity, and the narrow space factors are the aspect ratio coefficient of the narrow space, the height - to - width ratio of the narrow space, and the ventilation system failure of the narrow space.

[0056] In this embodiment, the index layer is the scoring of electrical equipment factors, installation environment factors, and narrow space factors in steps S41 to S49.

[0057] S420, constructing a judgment matrix: Through expert scoring, compare the importance of each factor at the same level with respect to a certain factor at the upper level pairwise, and construct a judgment matrix.

[0058] In an embodiment of the present invention, a judgment matrix is constructed based on expert knowledge, experience, and understanding of the electrical fire occurrence mechanism. The 1 - 9 scale method is adopted, where: 1 indicates that two factors are equally important when compared; 3 indicates that one factor is slightly more important than the other when compared; 5 indicates that one factor is significantly more important than the other when compared; 7 indicates that one factor is strongly more important than the other when compared; 9 indicates that one factor is extremely more important than the other when compared; 2, 4, 6, 8 are the median values of the above - mentioned adjacent judgments.

[0059] S430, calculating the weight vector: By calculating the maximum eigenvalue and the corresponding eigenvector of the judgment matrix, obtain the weight vector of each layer factor with respect to the upper - layer factor.

[0060] S440, consistency check: Calculate the consistency index and consistency ratio, and conduct a consistency check to ensure the rationality of the judgment matrix.

[0061] S450, calculate the comprehensive evaluation value according to the scores and weights of each electrical equipment index, installation environment index, and narrow space index, and determine the electrical fire risk level of the low - voltage cable in the narrow space according to the size of the comprehensive evaluation value.

[0062] In an embodiment of the present invention, the formula for the comprehensive evaluation value is as follows:

[0063] In the formula, is the comprehensive evaluation value, is the score of the th electrical equipment index, is the weight of the th electrical equipment index, is the score of the th installation environment index, is the weight of the th installation environment index, is the score of the th narrow space index, is the weight of the th narrow space index.

[0064] S50. Set initial parameters, determine the number of risk factors, set the value range of evaluation indicators, and set the moving step size.

[0065] In an embodiment of the present invention, the number of risk factors in each evaluation partition is determined and unified according to the actual situation. The value range of the evaluation indicators can be determined according to the actual meaning of the indicators and empirical data. The moving step size can be adjusted according to the convergence speed and accuracy requirements of the algorithm. The moving step size represents the moving speed during the search for danger.

[0066] In this embodiment, for the initial parameters, the number of risk factors is set to 30 - 50, and the value range of the evaluation indicators is set to 10% - 20%.

[0067] S60. Construct a probability model of fire occurrence as a fitness function to measure the quality of the electrical fire danger state.

[0068] In an embodiment of the present invention, the probability model of fire occurrence is: ; In the formula, is the probability of fire occurrence, is the comprehensive evaluation value, is the natural constant.

[0069] S70. Directionally search according to the low-voltage cable route in the narrow space, including: finding fire risk factors, within the value range of the evaluation indicators, finding a state with a higher fitness value and moving towards this state as the danger center point; judging the relevance with the surrounding positions, if the fitness value of this danger center point is higher than that of other danger center points within the surrounding range, then move towards this danger center point; comparing the magnitude of danger, if the fitness value of this danger center point is the highest among other points within the surrounding range, then move towards this point.

[0070] In an embodiment of the present invention, the optimization of the electrical fire risk mainly includes three parts: finding fire risk factors, judging the relevance to the surrounding positions, and comparing the magnitudes of risks. Judging the relevance to the surrounding positions focuses on the mutual influence and positional relationship among multiple risk factors, and pays attention to the combined effect of different risk points. Comparing the magnitudes of risks focuses on comparing the risks of surrounding points one by one, and directly selecting the points with higher risks for optimization.

[0071] In this embodiment, finding the fire risk factors includes: S711, setting as the fitness function of the position .

[0072] In this embodiment, it is used to measure the degree of risk of the risk factors at this position.

[0073] S712, for the current position of the th risk factor, a new position is randomly generated within the value range of the evaluation index , and an information matrix E is constructed for the new position, denoted by , and the information matrix of the positions it has searched through is recorded simultaneously; where is the information on the installation environment risk factors and the narrow space risk factors.

[0074] In this embodiment, represents a specific point related to the information of the th risk factor. Combining the installation environment risk factors and the narrow space risk factors can comprehensively and deeply reflect the impact of the environmental conditions at this position on the degree of fire risk.

[0075] S713, if the fitness value of the new position is greater than the fitness value of the initial position, then a risk factor with fire risk is found.

[0076] S714, if the above conditions are not met, then according to the information in the information matrix, a directional search is preferentially conducted towards the previously searched high - fitness - value area and in line with the propagation direction of the fire risk factors.

[0077] S715, define the directional search direction vector , set the search step size as , starting from the current position , search in the direction of , calculate the fitness value of the new position after each search, and update the information matrix E until the search of this area ends, and obtain the point with the highest fitness value in this area , as the danger center point, this point is a risk factor in this area.

[0078] In this embodiment, judging the relevance with surrounding positions reflects that the combined action of multiple risk factors may lead to a higher risk factor of electrical fire, including: S721, centered on the th risk factor, determine the radius of the circular area according to the number of risk factors existing in each evaluation partition , within the search range, identify and collect other risk factors and their corresponding fitness values.

[0079] In an embodiment of the present invention, assume that the number of risk factors existing in the evaluation partition is , set the basic coefficient , >0, the initial radius is: ; Let the length of the narrow space be l , the width be w , the total cable length Z, the correction coefficient between the length and width , the correction coefficient of the total length Z of the low-voltage cable , where, , .

[0080] When the space is more narrow and long, this coefficient is smaller, and the correction of the radius is more conservative, then . , is a reference cable length constant, which means that the longer the low-voltage cable, the smaller this coefficient, and the radius is relatively smaller, avoiding situations such as an unreasonable increase in the calculation amount due to an overly large search range.

[0081] Then, after correcting the initial radius, then ; that is ; S722, when it is found that the fitness value of the central position of other risk factors within the circular area is higher than the current risk factor, automatically expand the search range, and the current risk factor approaches the central position of other risk factors. This indicates that the current risk factor and other risk factors interact with each other and jointly determine the risk of electrical fire, and find out the risk factors that jointly affect the risk of electrical fire.

[0082] In an embodiment of the present invention, automatically expanding the search range includes: assuming that there is a certain such that P , then expand the search range according to β, and the new radius , and update the search area . Among them, β is the expansion coefficient, and 0 < β < 1.

[0083] The moving method for the current risk factor to approach the central position of other risk factors is ; among them is the approaching coefficient, .

[0084] In this embodiment, comparing the magnitudes of risks includes: when the th risk factor finds that the fitness value of other risk factors in the surrounding range is the highest, and the fitness value of this risk factor is greater than the th risk factor's fitness value, this risk factor is the risk factor that should be most concerned about.

[0085] S80. Continuously repeat step S70 until the target fitness is reached and stabilized, the convergence condition is met, and the evaluation index corresponding to the optimal electrical fire state is obtained. The evaluation index with a higher value is the most dangerous electrical fire factor.

[0086] In an embodiment of the present invention, algorithm iteration and convergence: Continuously repeat the electrical fire optimization process until the value of the fitness function is the target fitness and no longer changes significantly and is stable, which means the convergence condition is reached. At the same time, record the state with the highest electrical fire risk during each iteration.

[0087] Output the determined most dangerous electrical fire factor: When the algorithm converges, analyze the numerical value of the evaluation index corresponding to the optimal electrical fire state. The index with a higher numerical value is the most dangerous electrical fire factor.

[0088] Furthermore, it is also possible to compare the index numerical values of each evaluation partition to obtain the evaluation partition with the largest index numerical value.

[0089] Please refer to Figures 1 to 5 as shown. The present invention also provides a low-voltage cable electrical fire risk assessment system applicable to narrow spaces, applying the above-mentioned low-voltage cable electrical fire risk assessment method applicable to narrow spaces, including: The basic information module is used to obtain the basic information of the narrow space and the low-voltage cable information in the narrow space.

[0090] The evaluation partition module is used to equally divide the low-voltage cables in the narrow space into several evaluation partitions according to the total length of the narrow space.

[0091] The risk factor module is used to comprehensively check each link in several evaluation partitions and classify risk factors.

[0092] The index system module is used to construct a fire risk assessment index system, determine the weights of the index system, and obtain the influence degree of the evaluation indexes on the electrical fire risk.

[0093] The initial module is used to set initial parameters, determine the number of risk factors, set the value range of evaluation indexes, and set the search radius.

[0094] The fitness module constructs a probability model of fire occurrence as a fitness function to measure the quality of the electrical fire risk state.

[0095] The electrical fire risk optimization module conducts directional search according to the low-voltage cable layout in a narrow space, including: searching for fire risk factors, within the value range of evaluation indexes, searching for a state with a higher fitness value and moving towards this state as the risk center point; judging the relevance with surrounding positions, and moving towards this risk center point when the fitness value of this risk center point is higher than that of other risk center points within the surrounding range; comparing the risk levels, and moving towards the point with the highest fitness value among this risk center point and other points within the surrounding range.

[0096] The electrical fire factor module continuously repeats the steps in the electrical fire risk optimization module until the target fitness is reached and stabilized, meeting the convergence condition, obtaining the evaluation indexes corresponding to the optimal electrical fire state, and the evaluation index with a higher value is the most dangerous electrical fire factor.

[0097] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0098] The above-described embodiments only represent the implementation manners of the invention. The protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces, characterized in that: include: S123, determine the risk factors affecting low-voltage cable electrical fires in narrow and long spaces; S40, constructing a fire hazard assessment index system, determining the index system weights, and obtaining the degree of influence of the assessment index on the electrical fire hazard; S50, setting initial parameters, determining the number of risk factors, setting the value range of evaluation indicators, and the moving step length; S60, constructing a probability model of fire occurrence as a fitness function to measure the quality of the electrical fire hazard state; S70, directional search according to the direction of the low-voltage cable in the narrow and long space, including: finding fire risk factors, within the range of evaluation index values, finding a state with a higher fitness value, and moving to the state as the danger center point; Determine the correlation with the surrounding positions. If the fitness value of the dangerous center point is higher than that of other dangerous center points in the surrounding range, move to this dangerous center point; compare the size of the dangerousness. If the fitness value of the dangerous center point is the highest compared with other points in the surrounding range, move to this point; S80, continuously repeating step S70 until the target fitness is reached and stabilized, and the convergence condition is met, and the evaluation index corresponding to the optimal electrical fire state is obtained. The evaluation index with a high value is the most dangerous electrical fire factor.

2. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 1 is characterized in that: Step S40, constructing a fire hazard assessment index system, including setting electrical equipment indicators, installation environment indicators and narrow and long space indicators, and scoring the electrical equipment indicators, installation environment indicators and narrow and long space indicators; wherein the electrical equipment indicators include the degree of aging of low-voltage cable insulation, the degree of damage to the low-voltage cable insulation layer, the low-voltage cable overload risk factor, and the probability of overheating of the low-voltage cable connector; the installation environment indicators include ambient temperature and ambient humidity; the narrow and long space indicators include the narrow space length-to-width ratio coefficient, the narrow space height-to-width ratio, and the narrow space ventilation system failure.

3. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 2 is characterized in that: Determine the weight of the indicator system, including: Establish a hierarchical model: take the electrical fire hazard assessment as the target layer, the electrical equipment factor, the installation environment factor, and the narrow space factor as the criterion layer, and the indicators of each factor as the indicator layer; Constructing a judgment matrix: Through expert scoring, the importance of each factor at the same level relative to a factor at the previous level is compared pairwise to construct a judgment matrix; Calculate the weight vector: by calculating the maximum eigenvalue and corresponding eigenvector of the judgment matrix, the weight vector of each level factor relative to the previous level factor is obtained; Consistency test: calculate the consistency index and consistency ratio, conduct consistency test, and ensure the rationality of the judgment matrix; A comprehensive evaluation value is calculated based on the scores and weights of various electrical equipment indicators, installation environment indicators, and narrow and long space indicators. The electrical fire hazard level of low-voltage cables in narrow and long spaces is determined based on the size of the comprehensive evaluation value.

4. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 3 is characterized in that: The formula for the comprehensive evaluation value is as follows: In the formula, is the comprehensive evaluation value, For the The rating of electrical equipment indicators, For the The weight of each electrical equipment indicator, For the The score of the installation environment index, For the The weight of the installation environment indicator, For the The score of the narrow space indicator, For the The weight of the narrow space indicator.

5. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 1 is characterized in that: The probability model of fire occurrence is as follows: ； In the formula, is the probability of fire occurrence, is the comprehensive evaluation value, is a natural constant.

6. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 1 is characterized in that: Fire hazard factors to look for include: set up For location The fitness function of No. Current location of risk factors , , a new position is randomly generated within the evaluation index value range , and construct an information matrix E for the new position, using Represents; and at the same time records the information matrix of the searched position; where, Provide information on installation environment hazards and narrow space hazards; If the fitness value of the new position is greater than the fitness value of the initial position, the dangerous factor with fire hazard is found; If the above conditions are not met, then based on the information in the information matrix, a directional search is preferentially performed towards the previously searched areas with high fitness values ​​and in line with the propagation direction of fire hazard factors; Defines the directional search direction vector , let the search step be , from the current location Start by following The direction is searched, and the fitness value of the new position is calculated after each search. , and update the information matrix E until the search in this area is completed, and the point with the highest fitness value in this area is obtained , as the dangerous center point, this point is the dangerous factor of the area.

7. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 1 is characterized in that: Determine the relevance to surrounding locations, including: First The radius is determined according to the number of risk factors in each evaluation zone. The circular area , in the search scope, identify and collect other risk factors and their corresponding fitness values; Find the circular area If the fitness value of the center position of other risk factors in the search is higher than that of the current risk factor, the search range will be automatically expanded, and the current risk factor will move closer to the center position of other risk factors.

8. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 7 is characterized in that: radius Obtained by the following formula: ； In the formula, is the basic coefficient, is the number of risk factors in the evaluation zone, is the length of the narrow space, is the width of the narrow space, is the total length of the low voltage cable, is the reference cable length.

9. The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces according to claim 7 is characterized in that: Automatically expand your search to include: Assume that there is a Make P , then expand the search range by β, and the new radius , and update the search area ; Where β is the expansion coefficient, 0<β<1; The current risk factor moves closer to the center of other risk factors in the following way: ;in is the proximity coefficient, .

10. A low-voltage cable electrical fire hazard assessment system suitable for narrow and long spaces, characterized in that: The method for assessing the electrical fire hazard of low-voltage cables in narrow and long spaces as described in any one of claims 1 to 9 comprises: Hazard factor module, used to determine the risk factors affecting low-voltage cable electrical fires in narrow spaces; The indicator system module is used to construct a fire hazard assessment indicator system, determine the indicator system weights, and obtain the impact of the assessment indicators on the electrical fire hazard; The initial module is used to set initial parameters, determine the number of risk factors, set the value range of evaluation indicators, and set the search radius; The fitness module builds a probability model of fire occurrence as a fitness function to measure the quality of the electrical fire hazard status; The electrical fire risk optimization module conducts a directional search based on the direction of low-voltage cables in narrow and long spaces, including: finding fire hazard factors, within the range of evaluation index values, finding a state with a higher fitness value, moving to that state as the danger center point; judging the correlation with the surrounding positions, and moving to this danger center point when the fitness value is higher than that of other danger center points in the surrounding range; comparing the size of the danger, and moving to this point when the fitness value of the danger center point is the highest compared with other points in the surrounding range; The electrical fire factor module continuously repeats the steps in the electrical fire risk optimization module until the target fitness is reached and stabilized, and the convergence conditions are met to obtain the evaluation index corresponding to the optimal electrical fire state. The evaluation index with a high value is the most dangerous electrical fire factor.

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