High-rise building transformer short circuit risk assessment method based on fault tree and risk matrix

Abstract

The invention belongs to the field of electrical risk assessment, and discloses a high-rise building transformer short circuit risk assessment method based on a fault tree and a risk matrix, and the method comprises the following steps: 1, constructing a fault tree with high-rise building transformer short circuit as a top event; step 2, inputting hidden danger probability data, performing quantitative analysis to obtain the occurrence probability of risk events, and performing qualitative analysis to obtain an importance degree result of each hidden danger event; and step 3, constructing a risk matrix model, and performing risk grading on the hidden danger events. By adopting the technical scheme, workers can be helped to accurately and quickly carry out hidden danger investigation and find out the hidden danger with the maximum risk, the hidden danger reasoning efficiency is improved, and according to the criticality result and the risk level of the hidden danger, the criticality result and the risk level can be used as the reference basis of the workers, and measures of different degrees can be taken in advance for all the hidden dangers to deal with the hidden dangers.

Description

Technical Field

[0001] The present invention relates to the field of electrical risk assessment, and particularly to a method for assessing the short - circuit risk of transformers in high - rise buildings based on fault trees and risk matrices. Background Technique

[0002] In recent years, with the continuous advancement of urbanization in China, high - rise buildings have gradually become the first choice for urban construction. Due to their dense population, large power density, and high requirements for power supply reliability, users of high - rise buildings have also become important targets for power grid companies to carry out investigations on potential electricity safety hazards and provide high - quality services. The electricity load of high - rise buildings has been growing rapidly, but the load - bearing capacity of the power distribution and utilization systems of some old high - rise buildings is limited. Coupled with insufficient attention to maintenance, there are many potential electricity safety hazards. Once power outages, fires, electric shocks and other electricity safety accidents occur in the public electrical facilities in high - rise buildings, serious consequences may be caused. At present, there is a lack of systematic classification research on potential hazards of key electrical facilities in high - rise buildings at home and abroad. As a widely used tool for system reliability analysis and safety evaluation, the fault tree analysis method can intuitively classify potential hazards and represent the relationship between potential hazards and risks. Based on the fault tree analysis method, a risk matrix is used to comprehensively evaluate potential hazards. This method can find out the most harmful potential hazards and help maintenance personnel evaluate and investigate safety hazards in all - round and multi - dimensional ways. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for assessing the short - circuit risk of transformers in high - rise buildings based on fault trees and risk matrices, which can find out the most serious potential hazards of electrical facilities, help staff improve the efficiency of handling potential hazards, and provide a basis for decision - makers to classify and grade potential hazard risks, facilitating the adoption of corresponding measures for potential hazards of different levels.

[0004] To achieve the above - mentioned purpose, the technical solution of the present invention is as follows:

[0005] A method for assessing the short - circuit risk of transformers in high - rise buildings based on fault trees and risk matrices, comprising the following steps:

[0006] Step 1: Construct a fault tree with "short - circuit of transformers in high - rise buildings" as the top event

[0007] For the fault tree with "short - circuit of transformers in high - rise buildings" as the top event, the transformer short - circuit is summarized into various potential hazard events including aging of insulating materials, failure, damage to insulation by external force factors, foreign objects falling into the transformer interior, influence of external environmental factors, deformation and instability of transformer windings. These potential hazard events are used as the bottom events of the fault tree. Based on this, a fault tree and a potential hazard event table are constructed. The event table is shown in Table 1:

[0008] Table 1 Potential Hazard Event Table

[0009]

[0010] Step 2: Input the hidden danger probability data. Through quantitative analysis, obtain the probability of the occurrence of the risk event, and through qualitative analysis, obtain the importance results of each hidden danger event;

[0011] According to the minimal cut sets of the hidden danger events, calculate the occurrence probability of the top event of transformer short circuit. The calculation formula is as follows:

[0012]

[0013] In the formula: n is the number of minimal cut sets; M i is the i-th minimal cut set, P(M i ) is the probability corresponding to the i-th minimal hidden danger cut set, and P(M i M j ) is the product of the occurrence probabilities of two adjacent minimal hidden danger cut sets;

[0014] The critical importance is an index to measure the contribution degree of the hidden danger event to the occurrence probability of the risk event. It can identify the most critical event leading to system failure. The critical importance formula is as follows:

[0015]

[0016] In the formula, qi is the occurrence probability of the i-th bottom event, and I pr (xi) represents the probability importance of the i-th hidden danger event;

[0017] The probability importance formula is as follows:

[0018]

[0019] In the formula, take the partial derivative of the occurrence probability qi of the i-th bottom event in the top event occurrence probability formula;

[0020] Step 3: Construct a risk matrix model to classify the risks of hidden danger events

[0021] Regarding the possibility L of the occurrence of the hidden danger and the severity S of the consequences of the hidden danger, use them as two dimensions to construct a 5×5 risk matrix. Through the relative magnitudes of the risk probabilities and critical importances of each hidden danger event and by consulting the opinions of relevant experts, divide the grade values of the occurrence probability and consequence severity of each hidden danger event. The value range is [0, 100]. According to their characteristics, make divisions within the range, and define the five divided intervals as five grades: Ⅰ, Ⅱ, Ⅲ, Ⅳ, and Ⅴ, as shown in Table 2:

[0022] Table 2 Grade Division Table of Hidden Danger Probability and Hidden Danger Consequence Severity

[0023]

[0024] Finally, based on the risk matrix, according to the formula: R = L×S, the risk level of the potential hazard event is obtained;

[0025] The risk matrix is shown in Table 3:

[0026] Table 3 Risk Matrix Level Division Table

[0027]

[0028] Furthermore, the minimum cut sets of potential hazards are: {X1}, {X2}, {X3}, {X4}, {X5}, {X6}, {X7}, {X8, X9}, {X10}, {X11}, {X12}.

[0029] Furthermore, potential hazards with medium and low risk levels need to be taken seriously, and corresponding measures should be taken to address them as early as possible; potential hazards with medium risk levels need to be investigated and eliminated in a timely manner; when potential hazards are at a major risk level, immediate measures should be taken to address them.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] 1) The high-rise building transformer short-circuit risk assessment method based on the fault tree and risk matrix. The fault tree model adopted can intuitively represent the logical relationship between the short-circuit potential hazards and risks of high-rise building transformers, and according to the results of qualitative and quantitative analyses, the efficiency of potential hazard investigation can be improved.

[0032] 2) The risk matrix model can effectively determine the risk level of potential hazards, and obtain the potential hazards with the greatest transformer short-circuit risk, which is convenient for staff to take corresponding measures according to potential hazards of different levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is the flow chart of the high-rise building transformer short-circuit risk assessment method;

[0034] Figure 2 is the transformer short-circuit fault tree model of the present invention;

[0035] Figure 3 is the comparison chart of the key importance of transformer short-circuit potential hazard events; DETAILED DESCRIPTION OF THE INVENTION

[0036] The following will describe in detail a method for risk assessment of high-rise building transformer short circuits based on fault trees and risk matrices in conjunction with the accompanying drawings and embodiments. However, the present invention is not limited to the examples described herein. These embodiments are provided to more fully disclose the present invention and to fully convey the scope of the present invention to those skilled in the relevant technical field. The terms in the exemplary embodiments shown in the accompanying drawings are not limitations on the present invention. Unless otherwise specified, the terms used herein (including technical terms) have the ordinary meaning understood by those skilled in the relevant technical field. Additionally, it can be understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant fields and should not be understood in an idealized or overly formal sense.

[0037] As Figure 1 shown is the flowchart of the risk assessment method for key power-consuming facilities in high-rise buildings based on fault trees and risk matrices.

[0038] Step 1: Construct a fault tree with "short circuit of high-rise building transformer" as the top event

[0039] For the fault tree with "short circuit of high-rise building transformer" as the top event, the main reason for the transformer short circuit is the problem of insulation performance. The possible reasons are as follows: (1) Aging of insulation materials will cause slight overheating and partial discharge inside the transformer. As time goes by, the insulation will be further damaged, leading to a short circuit in the internal winding of the transformer; (2) External force damage (such as rats biting through the insulation material) may also cause a short circuit between windings; (3) Influence of external environmental factors (such as moisture, pollution, etc.). When the moisture in the environment is too high, a chemical reaction with impurities will form corrosive substances, further damaging the insulation. If the desiccant cannot function at this time, the moisture inside the transformer body will increase, making it extremely easy to cause a short circuit; (4) For situations such as deformation and instability of the transformer winding, the wires are very likely to be affected by electromagnetic force and vibrate at this time, and then rub against each other to cut through the insulation and cause a short circuit; (5) After foreign objects fall into the transformer, they may directly contact the wires with damaged insulation, causing the wires to come into direct contact with each other and resulting in a short circuit. These possible reasons are counted as hidden danger events. The hidden danger events are used as the bottom events of the fault tree. Based on this, a fault tree and a hidden danger event table are constructed. The probability of the appearance of hidden dangers refers to the results of the hidden danger investigation and statistics of a certain city's power association for the communities in the city. The event table is shown in Table 1:

[0040] Table 1 Hidden danger event table

[0041]

[0042] Use the fault tree analysis method to represent the logical relationship between the transformer short circuit and each hidden danger event, construct a fault tree model, and classify the hidden dangers, as Figure 2 shown.

[0043] InFigure 2 Based on the transformer short - circuit fault tree model, the minimum cut sets are obtained by the downward method. In the cut sets, if one of the basic events does not occur, the top event will not occur. The minimum cut sets are: {X1}, {X2}, {X3}, {X4}, {X5}, {X6}, {X7}, {X8, X9}, {X10}, {X11}, {X12}.

[0044] Step 2: Input the hidden danger probability data, obtain the probability of the risk event occurring through quantitative analysis, and obtain the importance results of each hidden danger event through qualitative analysis;

[0045] According to the minimum cut sets of the hidden danger events, calculate the occurrence probability of the top - event transformer short - circuit. The calculation formula is as follows:

[0046]

[0047] In the formula: n is the number of minimum cut sets; M i is the i - th minimum cut set, P(M i ) is the probability corresponding to the i - th minimum hidden - danger cut set, and P(M i M j ) is the product of the occurrence probabilities of two adjacent minimum hidden - danger cut sets;

[0048] The calculated occurrence probability of the transformer short - circuit is 0.0035.

[0049] Then, according to the above formula, calculate the probability importance of each hidden danger event. The probability importance is an index to measure the influence degree of the basic event on the occurrence probability of the top - layer event. The formula is:

[0050]

[0051] In the formula, it represents taking the partial derivative of the occurrence probability qi of the i - th bottom event in the top - event occurrence probability formula.

[0052] Then, according to the above probability degree formula, calculate the critical importance. The critical importance is an index to measure the contribution degree of the basic event to the occurrence probability of the top - event. It can identify the most critical hidden - danger events leading to the occurrence of the top - event, so that the staff can formulate effective prevention and control measures. The critical importance is shown in the following formula.

[0053]

[0054] In the formula: i represents the i - th bottom event, P(T) represents the occurrence probability of the top - event, and I pr (xi) represents the probability importance of the i - th basic event.

[0055] 3. Construct a risk matrix model to classify the risks of hidden - danger events

[0056] Comprehensively considering the possibility L of potential hazards occurring and the severity S of the consequences of potential hazards, a 5×5 risk matrix is constructed with these two dimensions. By analyzing real-world cases and consulting relevant expert opinions, and combining the aspects of casualties and economic losses, the grade values of the possibility of potential hazards and the severity of the consequences of potential hazards are divided. The value range is [0, 100]. According to their characteristics, the division is carried out within this range, and the five divided intervals are respectively defined as five grades: Ⅰ, Ⅱ, Ⅲ, Ⅳ, and Ⅴ, as shown in Table 2.

[0057] Table 2 Grade Division Table of Potential Hazard Probability and Severity of Potential Hazard Consequences

[0058]

[0059] Finally, based on the risk matrix, according to the formula: R = L×S, the risk level of the potential hazard event is obtained;

[0060] The risk matrix is shown in Table 3:

[0061] Table 3 Risk Matrix Level Division Table

[0062]

[0063]

[0064] According to the occurrence probability and key importance results of potential hazard events, through expert consultation and evaluation, the potential hazard probability L and the severity of consequences S are evaluated and quantified according to Table 2. Corresponding to the risk matrix in Table 3, according to the formula: R = L×S, the final risk levels of each potential hazard event are obtained, as shown in Table 4 below.

[0065] Table 4 Results of Potential Hazard Risk Levels

[0066]

[0067] When the potential hazard is at medium or low risk level, attention should be paid and countermeasures should be taken to the potential hazard as soon as possible. When the potential hazard is mainly at high risk level, measures should be taken in time to investigate and eliminate it. When the potential hazard is mainly at major risk level, measures should be taken immediately to deal with it.

[0068] From Figure 3 the sorting results of the key importance of each potential hazard event, it can be seen that the events of insulation material aging and failure and the event of external force factor damaging the insulation have the greatest impact on the occurrence probability of the top event, and should be investigated preferentially; most of the potential hazards leading to transformer short - circuit in this community belong to high and medium level risks, and the major risk potential hazard is "overload", which requires attention to the on - line monitoring of the actual operation of the transformer and timely taking countermeasures.

[0069] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Through practical applications, the above method provides a reference basis for inspection and decision-making personnel, enabling them to take timely and accurate measures to detect potential hazards, and formulate corresponding countermeasures according to the level of risk.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that modifications or equivalent replacements can still be made to the specific embodiments of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A method for evaluating the short - circuit risk of high - rise building transformers based on a fault tree and a risk matrix, characterized in that, It includes the following steps: Step 1: Construct a fault tree with "short circuit of high-rise building transformer" as the top event For the fault tree with "short circuit of high-rise building transformer" as the top event, the transformer short circuit is summarized into various potential hazard events including insulation material aging, failure, external force factor damaging insulation, foreign objects falling into the transformer interior, external environmental factor influence, transformer winding deformation, and instability. These potential hazard events serve as the bottom events of the fault tree. Based on this, a fault tree and a potential hazard event table are constructed. The event table is shown in Table 1: Table 1 Potential Hazard Event Table Step 2: Input the potential hazard probability data, obtain the probability of the risk event occurring through quantitative analysis, and obtain the importance results of each potential hazard event through qualitative analysis; According to the minimal cut sets of the potential hazard events, calculate the occurrence probability of the top event transformer short circuit. The calculation formula is as follows: Where: n is the number of minimum cut sets, M i is the i-th minimum cut set, P(M i ) is the probability corresponding to the i-th minimum hidden danger cut set, P(M i M j ) is the product of the occurrence probabilities of two adjacent minimum hidden danger cut sets; The critical importance is an index to measure the contribution degree of the potential hazard event to the occurrence probability of the top event. The critical importance formula is shown as follows: where qi is the occurrence probability of the i-th basic event, and I pr (xi) represents the probability importance degree of the i-th hidden danger event; The probability importance formula is shown as follows: In the formula, take the partial derivative of the occurrence probability qi of the i-th bottom event of the occurrence probability of the top event; Step 3: Construct a risk matrix model to conduct risk grading for the potential hazard events For the possibility L of the potential hazard occurrence and the severity S of the potential hazard consequence, use them as two dimensions to construct a 5×5 risk matrix. The value range is [0, 100], and five intervals are divided and defined as five levels: I, II, III, IV, and V respectively, as shown in Table 2: Table 2 Classification Table of Potential Hazard Probability and Potential Hazard Consequence Severity Finally, based on the risk matrix, according to R = L×S, obtain the final risk levels of each potential hazard event.

2. The method for evaluating the short - circuit risk of a high - rise building transformer based on a fault tree and a risk matrix according to claim 1, wherein, The minimal potential hazard cut sets are: {X1}, {X2}, {X3}, {X4}, {X5}, {X6}, {X7}, {X8, X9}, {X10}, {X11}, {X12}.

3. The method for evaluating the short - circuit risk of a high - rise building transformer based on a fault tree and a risk matrix according to claim 1, wherein, The risk matrix is shown in Table 3: Table 3 Risk Matrix Level Classification Table 4. The high-rise building transformer short-circuit risk assessment method based on a fault tree and a risk matrix according to claim 3, wherein, When it is at medium and low risk levels, attention needs to be paid and countermeasures for potential hazards should be taken as early as possible; when it is at high risk level, measures need to be taken in time for investigation; when it is at major risk level, measures need to be taken immediately to deal with it.

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