Method and system for calculating critical distance of hot thin combustible ignited by fault arc

Abstract

The invention discloses a critical distance calculation method and system for igniting a hot thin combustible material by a fault arc, and relates to the technical field of electrical fire safety, and the method comprises the steps: building a heat transfer model between the fault arc and the hot thin combustible material based on a lumped heat capacity method, and determining an energy balance equation of a heat transfer process based on the heat transfer model; the heat transfer model comprises a fault arc of an equivalent spherical radiation source, an electrode high-temperature area and a wafer infinitesimal located in the center of a hot thin combustible; based on the current value and the voltage value of the fault arc, determining the radiation power of the fault arc and the electrode high-temperature area as an overall heat source; based on the energy balance equation and the radiation power, constructing a critical angle coefficient equation when the wafer infinitesimal reaches the critical ignition temperature; and based on the critical angle coefficient equation, calculating the critical distance of igniting the hot thin combustible material by the fault arc. The technical problem that the safety distance between the combustible and the potential fault arc generation position cannot be determined in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of electrical fire safety, and in particular to a method and system for calculating a critical distance for a fault arc to ignite a hot and thin combustible object. Background Art

[0002] In recent years, the situation of electrical fires in my country has been severe. The frequency of electrical fires and the loss of life and property caused by them rank first among all types of fires. As one of the important factors leading to electrical fires, the temperature of the fault arc can reach thousands of degrees Celsius, which can not only ignite the insulation layer of the electrical line, but also ignite nearby combustibles, and the fire risk is extremely high.

[0003] At present, research on fault arcs mainly focuses on the development of identification technology and related detection products. Although the application of related results has reduced the probability of fires caused by fault arcs to a certain extent, the reliability of its detection technology still needs to be improved, especially for series fault arcs, whose discharge and heating may continue for a long time without triggering an alarm, causing the insulation layer of the wire and surrounding combustibles to be ignited, and eventually leading to fires. Due to the lack of a method to calculate the distance range of combustibles ignited by fault arcs, it is impossible to determine the safe distance between combustibles and the location of potential fault arcs, and it is impossible to scientifically guide the prevention measures of fault arc fires. Summary of the invention

[0004] In order to solve the above technical problems existing in the prior art, the embodiment of the present invention provides a method and system for calculating the critical distance of a fault arc igniting a hot and thin combustible material. The technical solution is as follows:

[0005] On the one hand, a method for calculating the critical distance at which a fault arc ignites a thermally thin combustible material is provided, the method comprising: establishing a heat transfer model between the fault arc and the thermally thin combustible material based on the lumped heat capacity method, and determining an energy balance equation for the heat transfer process based on the heat transfer model; the heat transfer model comprises a fault arc and an electrode high temperature region of an equivalent spherical radiation source and a disk microelement located at the center of the thermally thin combustible material; determining the radiation power of the fault arc and the electrode high temperature region as an overall heat source based on the current value and voltage value of the fault arc; constructing a critical angle coefficient equation when the disk microelement reaches a critical ignition temperature based on the energy balance equation and the radiation power; and calculating the critical distance at which the fault arc ignites the thermally thin combustible material based on the critical angle coefficient equation.

[0006] Furthermore, the heat transfer model is a model in which one side of the disc microelement receives radiant heat from a heat source, both sides undergo convective heat exchange with the surrounding air, and simultaneously emits radiation to the surrounding environment, and conducts heat from the disc microelement to the periphery of the thermally thin combustible material.

[0007] Furthermore, the energy balance equation includes:

[0008]

[0009] Wherein, a and ε are the absorptivity and emissivity of the micro-element of the disc, respectively, τ is the thickness of the micro-element of the disc, ρ is the density of the micro-element of the disc, c is the specific heat capacity of the micro-element of the disc, σ is the Stefan-Boltzmann constant, is the net heat flux received by the surface of the disk microelement, T is the temperature, and t is the time;

[0010] The radiation power includes:

[0011]

[0012]

[0013] P arc (t) = V arc (t)·I circuit (t)

[0014] In the formula, is the average power of the fault arc during the period from time t1 to time t2, that is, the radiation power, I circuit (t) and V arc (t) are the current value and voltage value of the fault arc respectively.

[0015] Further, based on the energy balance equation and the radiation power, constructing a critical angle coefficient equation when the disc microelement reaches a critical ignition temperature includes: based on the energy balance equation, determining a critical energy balance equation when the disc microelement reaches a critical ignition temperature; wherein the critical energy balance equation includes:

[0016]

[0017] Based on the radiation power, a critical incident heat flux when the wafer microelement reaches a critical ignition temperature is determined; wherein the critical incident heat flux includes:

[0018]

[0019] Based on the critical energy balance equation and the critical incident heat flux, a critical angle coefficient equation is constructed when the disc microelement reaches the critical ignition temperature; wherein the critical angle coefficient equation includes:

[0020]

[0021] Where, T ig is the critical ignition temperature, is the critical incident heat flux, r is the radius of the disk element, F 12，cr is the critical angle coefficient.

[0022] Further, calculating the critical distance for the fault arc to ignite the thermally thin combustible material includes:

[0023]

[0024] Where, d ct is the critical distance.

[0025] Furthermore, the heat transfer model is a model in which one side of the disc microelement receives radiant heat from a heat source, the other side is insulated, one side undergoes convective heat exchange with the surrounding air, and simultaneously emits radiation to the surrounding environment, and conducts heat from the disc microelement to the periphery of the thermally thin combustible material.

[0026] Furthermore, the energy balance equation includes:

[0027]

[0028] Wherein, a and ε are the absorptivity and emissivity of the micro-element of the disc, respectively, τ is the thickness of the micro-element of the disc, ρ is the density of the micro-element of the disc, c is the specific heat capacity of the micro-element of the disc, σ is the Stefan-Boltzmann constant, is the net heat flux received by the surface of the disk microelement, T is the temperature, and t is the time;

[0029] The critical angle coefficient equation includes:

[0030]

[0031] Where, T ig is the critical ignition temperature, is the critical incident heat flux, r is the radius of the disk element, F 12，cr is the critical angle coefficient, is the radiation power;

[0032] The critical distance includes:

[0033]

[0034] Where, d cr is the critical distance.

[0035] On the other hand, a critical distance calculation system for a fault arc to ignite a thermally thin combustible material is also provided, the system comprising: a first determination module, a second determination module, a construction module and a calculation module; wherein the first determination module is used to establish a heat transfer model between the fault arc and the thermally thin combustible material based on the lumped heat capacity method, and determine the energy balance equation of the heat transfer process based on the heat transfer model; the heat transfer model includes the fault arc and the electrode high temperature area of ​​an equivalent spherical radiation source and a disc microelement located at the center of the thermally thin combustible material; the second determination module is used to determine the radiation power of the fault arc and the electrode high temperature area as a whole heat source based on the current value and voltage value of the fault arc; the construction module is used to construct a critical angle coefficient equation when the disc microelement reaches the critical ignition temperature based on the energy balance equation and the radiation power; the calculation module is used to calculate the critical distance of the fault arc to ignite the thermally thin combustible material based on the critical angle coefficient equation.

[0036] On the other hand, an electronic device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method provided in the embodiment of the present invention when executing the computer program.

[0037] On the other hand, a computer-readable storage medium is provided, in which a program code is stored. The program code can be called by a processor to execute the method provided in the embodiment of the present invention.

[0038] The embodiment of the present invention provides a method and system for calculating the critical distance of a fault arc igniting a thermally thin combustible. Based on the surface temperature distribution of the material obtained by heating the thermally thin combustible by the fault arc, the fault arc and the high temperature area of ​​the electrode are simplified into a spherical radiation source. The average value of the product of the fault arc voltage and current over the arcing period is used as the radiation power of the spherical radiation source. By calculating the angular coefficient of the spherical radiation source, the radiation flux obtained by the thermally thin combustible microelement at a certain distance is derived. According to the critical ignition temperature of the combustible and the lumped heat capacity method, the critical distance that can ignite the combustible is obtained. The present invention can be used to determine the safe distance at which a fault arc may ignite combustibles in the surrounding environment under specific conditions, and provide a scientific basis for effectively preventing electrical fires caused by fault arcs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 It is a flow chart of a method for calculating a critical distance for a fault arc to ignite a hot and thin combustible material provided by an embodiment of the present invention;

[0041] Figure 2 It is a schematic diagram of the surface temperature distribution of a thermally thin combustible under different current and distance test conditions provided by an embodiment of the present invention, and the icon represents the current-distance used in the test;

[0042] Figure 3 It is a schematic diagram of a heat transfer model between a fault arc and a thermally thin combustible material provided by an embodiment of the present invention;

[0043] Figure 4 is a schematic diagram of an angle coefficient from a spherical radiation source to a finite coaxial circular surface provided by an embodiment of the present invention;

[0044] Figure 5 It is a current and voltage waveform diagram of a fault arc during the ignition process of printing paper provided by an embodiment of the present invention;

[0045] Figure 6 A fault arc energy waveform diagram during the ignition process of printing paper provided by an embodiment of the present invention;

[0046] Figure 7 It is a schematic diagram of a critical distance calculation system for a fault arc igniting a hot and thin combustible material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0048] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0049] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0050] Embodiment 1

[0051] Figure 1 1 is a flow chart of a method for calculating the critical distance of a fault arc igniting a hot and thin combustible material according to an embodiment of the present invention. Figure 1 As shown, the method specifically comprises the following steps:

[0052] Step S102, based on the lumped heat capacity method, a heat transfer model between the fault arc and the thermally thin combustible is established, and the energy balance equation of the heat transfer process is determined based on the heat transfer model. The heat transfer model includes the fault arc of the equivalent spherical radiation source and the high temperature area of ​​the electrode and the disc microelement located at the center of the thermally thin combustible.

[0053] Step S104, based on the current value and voltage value of the fault arc, determine the radiation power of the fault arc and the high temperature area of ​​the electrode as an overall heat source.

[0054] Step S106, constructing a critical angle coefficient equation when the wafer microelement reaches a critical ignition temperature based on the energy balance equation and the radiation power.

[0055] Step S108, based on the critical angle coefficient equation, calculate the critical distance for the fault arc to ignite the thermally thin combustible material.

[0056] Specifically, when a fault arc occurs, the temperature and emissivity of the fault arc are unknown, and the temperature distribution of the high temperature area of ​​the electrode (for example, wire joints, switch contacts, socket terminals, connection points, etc.) is uneven, which makes it difficult to accurately determine the radiation power and radiation distribution of the fault arc and the high temperature area of ​​the electrode. In order to simplify the heat transfer analysis, the present invention regards the fault arc and the high temperature area of ​​the electrode as an integral heat source. It can be obtained from the experimental data of the fault arc ignition that when the center of the surrounding combustible surface is facing the center of the fault arc, the contour lines of the combustible surface temperature distribution diagram are circular or elliptical, such as Figure 2 As shown, based on this, the heat transfer model of the fault arc and thermally thin combustible material in the present invention assumes that the fault arc and the high-temperature area of ​​the electrode as a whole are a spherical radiation source, and then selects a circular microelement with a radius of r and a height of τ located at the center of the thermally thin combustible material sample for heat transfer analysis.

[0057] Figure 3 FIG. 1 is a schematic diagram of a heat transfer model between a fault arc and a thermally thin combustible material provided according to an embodiment of the present invention. Figure 3 As shown, the model includes two cases:

[0058] Case 1: One side of the disk microelement receives radiant heat from the heat source, and both sides undergo convective heat exchange with the surrounding air. At the same time, it emits radiation to the surrounding environment and conducts heat from the disk microelement to the periphery of the thermally thin combustible material.

[0059] Case 2: One side of the disk element receives radiant heat from the heat source, while the other side is insulated. Convection heat exchange occurs on one side with the surrounding air, while radiation is emitted to the surrounding environment, and heat is conducted from the disk element to the periphery of the thermally thin combustible material.

[0060] Assuming that the temperature of the wafer element is uniformly distributed, the energy balance equation within the time interval dt can be expressed as:

[0061] Scenario 1:

[0062]

[0063] Scenario 2:

[0064]

[0065] In the formula, A c and A l are the circular surface area and lateral surface area of ​​the disk element, m 2 ; a and ε are absorptivity and emissivity respectively; τ is thickness, m; ρ is density, kg / m 3 ; c is specific heat capacity, J / (kg·K); k is thermal conductivity, W / (m·K); T a is the ambient temperature, K; σ is the Stefan-Boltzmann constant, 5.67×10 -8 W / (m 2 ·K 4 ); h is the convective heat transfer coefficient, W / (m 2 K); is the net heat flux received by the microelement surface, W / m 2 .

[0066] Since the volume of the fault arc is small, when heating the surrounding combustibles, the surface temperature distribution of the combustibles will be uneven, and its temperature gradient dT / dr is difficult to derive. At the same time, considering that the heat loss caused by convection and heat conduction is much smaller than the radiation heat loss, the convection and heat conduction terms are ignored in equations (1) and (2), and equations (1) and (2) are simplified to the following energy balance equations:

[0067]

[0068] To calculate the incident heat flux acting on the disk element First, determine the power of the heat source. To simplify the analysis, assume that the fault arc and the high temperature area of ​​the electrode are the overall heat source, and all heat is transferred by radiation. The radiation power is equal to the fault arc power, which can be calculated by the following equation:

[0069] P arc (t) = V arc (t)·I circuit (t) (5)

[0070] When using AC, the arc power will continue to fluctuate as the current changes. Therefore, the radiated power is expressed as the average power of the arc over time, that is, the average power of the arc This power can be calculated using the following formula, namely the radiated power, including:

[0071]

[0072]

[0073] In the formula, is the average power of the fault arc during the period from t1 to t2, i.e., the radiated power, I circuit (t) and V arc (t) are the current and voltage values ​​of the fault arc respectively.

[0074] Since the heat radiated by the heat source does not completely irradiate the surface of the microelement, in order to calculate the actual heat received by the microelement of the disk, it is necessary to determine the angular coefficient between the heat source and the surface of the microelement of the disk, such as Figure 4 As shown in the figure, when the heat source is assumed to be spherical, it can be proved that the angular coefficient from the spherical heat source to a finite coaxial circular surface is independent of the radius of the spherical source, and the angular coefficient (F 12 ) is:

[0075]

[0076] Where R is the relative radius, which represents the ratio of the circular radius to the distance:

[0077] R=r / d (9)

[0078] To determine the critical ignition distance, it is assumed that under this distance condition, when the wafer microelement temperature reaches the critical ignition temperature (T ig ), dT / dt=0. Therefore, based on equations (3) and (4), the energy balance equations under the critical distance conditions corresponding to case 1 and case 2 can be obtained as follows:

[0079]

[0080] Where, T ig is the critical ignition temperature, K; is the critical incident heat flux, W / m 2 , critical incident heat flux It can be expressed as:

[0081]

[0082] According to formula (10) and formula (12), the critical angle coefficient equation for case 1 with radiation heating on one side and non-insulation on the other side can be obtained:

[0083]

[0084] According to formula (11) and formula (12), the critical angle coefficient equation for case 2 with radiation heating on one side and insulation on the other side can be obtained:

[0085]

[0086] Finally, according to formula (8) and formula (13), it can be concluded that the critical distance for the fault arc to ignite the hot thin combustible material in case of single-side radiation heating and non-insulation on the other side in situation 1 is:

[0087]

[0088] Finally, according to formula (8) and formula (14), the critical distance for the fault arc to ignite the thin combustible material in case 2 with radiation heating on one side and insulation on the other side is:

[0089]

[0090] As can be seen from the above description, the embodiment of the present invention provides a method for calculating the critical distance of a fault arc igniting a thermally thin combustible. Based on the surface temperature distribution of the material obtained by heating the thermally thin combustible by the fault arc, the fault arc and the high temperature area of ​​the electrode are simplified into a spherical radiation source, and the average value of the product of the fault arc voltage and current over the arcing period is used as the radiation power of the spherical radiation source. By calculating the angular coefficient of the spherical radiation source, the radiation flux obtained by the thermally thin combustible microelement located at a certain distance is derived, and the critical distance that can ignite the combustible is obtained according to the critical ignition temperature of the combustible and the lumped heat capacity method. The present invention can be used to determine the safe distance at which a fault arc may ignite combustibles in the surrounding environment under specific conditions, and provide a scientific basis for effectively preventing electrical fires caused by fault arcs.

[0091] Embodiment 2

[0092] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0093] With the size of 5×5cm 2 , thickness is 0.00012m, density is 800kg / m 3 The printing paper was used as the ignition object, and the fault arc ignition experiment was carried out under two different currents (8A and 12A). In the experiment, the printing paper setting was consistent with the situation described in situation 1, and the initial distance between the fault arc and the printing paper was set to 5mm, and gradually increased in steps of 2.5mm until the maximum distance at which the printing paper could not be ignited was reached. Among them, the printing paper was considered to be unignitable if it failed to ignite for more than 5 minutes, so as to obtain the critical distance for igniting the printing paper. In the experiment, the fault arc current and voltage data during the ignition process were collected synchronously. The waveforms of the current and voltage under 8A conditions are shown in the figure below. Figure 5As shown, the energy waveform is as follows Figure 6 As shown, the average power of the fault arc is obtained As shown in Table 1:

[0094] Table 1 Different test conditions

[0095]

[0096] A circular microelement of r = 1 mm is cut from the center of the printing paper. The critical ignition temperature T ig The value is 708K, and the critical ignition distance is calculated using formula (15). The comparison between the experimental value and the predicted value is shown in Table 2, where the interpolation of the maximum ignition distance and the minimum unignited distance is used as the experimental value to calculate the error between the two. Obviously, when the current varies in the range of 8A to 12A, the theoretical critical ignition distance is quite close to the experimental result, and the prediction model is reasonable.

[0097] Table 2 d under different test conditions cr The experimental and predicted values ​​of

[0098]

[0099] Embodiment 3

[0100] Figure 7 1 is a schematic diagram of a critical distance calculation system for a fault arc igniting a hot and thin combustible material according to an embodiment of the present invention. Figure 7 As shown, the system includes: a first determination module 10 , a second determination module 20 , a construction module 30 and a calculation module 40 .

[0101] Specifically, the first determination module 10 is used to establish a heat transfer model between the fault arc and the thermally thin combustible material based on the lumped heat capacity method, and determine the energy balance equation of the heat transfer process based on the heat transfer model; the heat transfer model includes the fault arc of the equivalent spherical radiation source and the high temperature area of ​​the electrode and the disc microelement located at the center of the thermally thin combustible material;

[0102] A second determination module 20 is used to determine the radiation power of the fault arc and the high temperature area of ​​the electrode as an overall heat source based on the current value and voltage value of the fault arc;

[0103] A construction module 30 is used to construct a critical angle coefficient equation when the disc microelement reaches a critical ignition temperature based on an energy balance equation and radiation power;

[0104] The calculation module 40 is used to calculate the critical distance for the fault arc to ignite the thermally thin combustible material based on the critical angle coefficient equation.

[0105] The present invention further provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method provided in the embodiment of the present invention when executing the computer program.

[0106] The present invention further provides a computer-readable storage medium, in which program codes are stored. The program codes can be called by a processor to execute the method provided in the embodiment of the present invention.

[0107] It should be understood that the memory in the embodiments of the present invention may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM).

[0108] The above embodiments can be implemented in whole or in part by software, hardware (such as circuits), firmware or any other combination. When implemented by software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center by wired (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more available media sets. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a tape), an optical medium (for example, a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state hard disk.

[0109] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0110] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0111] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described equipment, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0112] In the several embodiments provided by the present invention, it should be understood that the disclosed devices, apparatuses and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0113] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0114] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0115] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0116] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for calculating the critical distance of a fault arc igniting a hot and thin combustible material, characterized in that: The method comprises: Based on the lumped heat capacity method, a heat transfer model between the fault arc and the thermally thin combustible is established, and the energy balance equation of the heat transfer process is determined based on the heat transfer model; the heat transfer model includes the fault arc of the equivalent spherical radiation source and the high temperature area of ​​the electrode and the disc microelement located at the center of the thermally thin combustible; Based on the current value and voltage value of the fault arc, determining the radiation power of the fault arc and the high temperature area of ​​the electrode as an overall heat source; Based on the energy balance equation and the radiation power, constructing a critical angle coefficient equation when the disc microelement reaches a critical ignition temperature; Based on the critical angle coefficient equation, a critical distance for the fault arc to ignite the thermally thin combustible material is calculated.

2. The method according to claim 1, characterized in that The heat transfer model is a model in which one side of the disk microelement receives radiant heat from a heat source, both sides undergo convection heat exchange with the surrounding air, and simultaneously emits radiation to the surrounding environment, and conducts heat from the disk microelement to the periphery of the thermally thin combustible material.

3. The method according to claim 2, characterized in that The energy balance equation includes: Wherein, a and ε are the absorptivity and emissivity of the micro-element of the disc, respectively, τ is the thickness of the micro-element of the disc, ρ is the density of the micro-element of the disc, c is the specific heat capacity of the micro-element of the disc, σ is the Stefan-Boltzmann constant, is the net heat flux received by the surface of the disk microelement, T is the temperature, and t is the time; The radiation power includes: P arc (t)=V arc (t)·I circuit (t) In the formula, is the average power of the fault arc during the period from time t1 to time t2, that is, the radiation power, I circuit (t) and V arc (t) are the current value and voltage value of the fault arc respectively.

4. The method according to claim 3, characterized in that: Based on the energy balance equation and the radiation power, a critical angle coefficient equation when the disc microelement reaches the critical ignition temperature is constructed, including: Based on the energy balance equation, a critical energy balance equation when the wafer microelement reaches a critical ignition temperature is determined; wherein the critical energy balance equation includes: Based on the radiation power, a critical incident heat flux when the wafer microelement reaches a critical ignition temperature is determined; wherein the critical incident heat flux includes: Based on the critical energy balance equation and the critical incident heat flux, a critical angle coefficient equation is constructed when the disc microelement reaches the critical ignition temperature; wherein the critical angle coefficient equation includes: Where, T ig is the critical ignition temperature, is the critical incident heat flux, r is the radius of the disk element, F 12,cr is the critical angle coefficient.

5. The method according to claim 4, characterized in that Calculating the critical distance for the fault arc to ignite the thermally thin combustible material comprises: Where, d cr is the critical distance.

6. The method according to claim 1, characterized in that The heat transfer model is a model in which one side of the disc microelement receives radiant heat from a heat source, the other side is insulated, one side undergoes convective heat exchange with the surrounding air, and simultaneously emits radiation to the surrounding environment, and conducts heat from the disc microelement to the periphery of the thermally thin combustible material.

7. The method according to claim 6, characterized in that The energy balance equation includes: Wherein, a and ε are the absorptivity and emissivity of the micro-element of the disc, respectively, τ is the thickness of the micro-element of the disc, ρ is the density of the micro-element of the disc, c is the specific heat capacity of the micro-element of the disc, σ is the Stefan-Boltzmann constant, is the net heat flux received by the surface of the disk microelement, T is the temperature, and t is the time; The critical angle coefficient equation includes: Where, T ig is the critical ignition temperature, is the critical incident heat flux, r is the radius of the disk element, F 12,cr is the critical angle coefficient, is the radiation power; The critical distance includes: Where, d cr is the critical distance.

8. A critical distance calculation system for fault arc ignition of hot and thin combustible materials, characterized in that: The system comprises: a first determining module, a second determining module, a building module and a calculating module; wherein, The first determination module is used to establish a heat transfer model between the fault arc and the thermally thin combustible material based on the lumped heat capacity method, and determine the energy balance equation of the heat transfer process based on the heat transfer model; the heat transfer model includes the fault arc of the equivalent spherical radiation source and the high temperature area of ​​the electrode and the disk microelement located at the center of the thermally thin combustible material; The second determination module is used to determine the radiation power of the fault arc and the electrode high temperature area as an overall heat source based on the current value and voltage value of the fault arc; The construction module is used to construct a critical angle coefficient equation when the wafer microelement reaches a critical ignition temperature based on the energy balance equation and the radiation power; The calculation module is used to calculate the critical distance for the fault arc to ignite the thermally thin combustible material based on the critical angle coefficient equation.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program codes, which can be called by a processor to execute the method according to any one of claims 1 to 7.

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