High-voltage cable arc fault risk assessment method and device built based on dynamic fire source and cable pyrolysis combustion model

Abstract

The invention provides a high-voltage cable arc fault risk assessment method and device constructed based on a dynamic fire source and a cable pyrolysis combustion model, and the method comprises the steps: firstly constructing an electric characteristic calculation model of an overhead line-cable mixed line arc fault; acquiring voltage and current characteristic data of the cable arc fault under different relay protection strategies; secondly, constructing a cable arc fault model, obtaining a change relation of arc temperature along with time based on characteristic data simulation, and constructing a time-varying arc fire source; then testing thermal and chemical parameters of the cable material sample to obtain material test data; building a pyrolysis model of the cable material based on material test data, and balancing a combustion chemical equation; integrating the obtained model and data, and constructing a fault risk assessment model; and finally, calculating characteristic parameters representing the combustion intensity of the cable by using the model, and judging the risk level of the cable ignited by the electric arc. According to the invention, the electric arc fault ignition risk of the cable can be accurately determined.

Description

Technical Field

[0001] This invention belongs to the field of power system safety technology, specifically relating to a method and device for risk assessment of high-voltage cable arc faults based on a dynamic fire source and a cable pyrolysis combustion model. Background Technology

[0002] With the acceleration of urbanization, in the field of power transmission, overhead-cable hybrid transmission lines are gradually replacing pure overhead lines due to their advantages of ensuring efficient power transmission while reducing the occupation of urban ground space and improving urban aesthetics. This change in line structure has presented new requirements and challenges to related technologies in the power system.

[0003] For overhead-cable hybrid lines, fault handling places more stringent requirements on the reclosing technology of relay protection. In the event of an overhead line fault, reclosing must be enabled to quickly restore power, while in the event of a cable fault, reclosing should be disabled to prevent reignition at the fault point and jeopardize system safety. However, adaptive reclosing technology for this type of line is currently still in the research stage, and a complete theoretical framework and mature adaptive reclosing device have not yet been developed.

[0004] When an arcing ground fault occurs in a cable, due to the imperfections of adaptive reclosing technology, the transmission system relay protection may still perform reclosing operations, causing secondary arcing at the fault location and subsequently igniting the cable. Furthermore, the large number of cables in tunnels, close to each other, allows the fire to spread rapidly along the passage, potentially causing simultaneous damage to multiple circuits and even large-scale power outages, resulting in severe economic losses and safety hazards. Simultaneously, existing fire risk assessment methods are mostly based on static heat source or material ignition experiment data, neglecting transient temperature changes and dynamic heat source input during the arcing fault process, as well as the material evolution process during cable ignition. This leads to significant discrepancies between assessment results and actual conditions, making it difficult to provide accurate basis for adaptive reclosing and cable fire protection design. Moreover, given that actual cable tunnels can be tens of kilometers long, conducting on-site experiments to explore fire mechanisms presents enormous challenges. In the field of cable combustion simulation, a complete method for constructing high-voltage cable arcing fault models based on dynamic fire sources and cable pyrolysis combustion models has not yet been established, making it difficult to accurately determine the risk of cable arcing faults using fire dynamics simulation tools. Summary of the Invention

[0005] In view of this, the present invention provides a method and apparatus for risk assessment of high-voltage cable arc faults based on dynamic fire source and cable pyrolysis combustion model, aiming to solve the problem that the assessment results of existing fire risk assessment methods differ greatly from the actual situation.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a method for risk assessment of arc faults in high-voltage cables based on a dynamic ignition source and a cable pyrolysis combustion model, comprising the following steps: An electrical characteristic calculation model for arc faults in overhead-cable hybrid lines was constructed, and voltage and current characteristic data of cable arc faults under different relay protection strategies were obtained using the electrical characteristic calculation model. A cable arc fault model was constructed, and voltage and current characteristic data were used as input parameters. The relationship between cable arc temperature and time under different relay protection strategies was obtained through model simulation, and a time-varying arc source was constructed based on the relationship. Obtain cable material samples that match the simulation object, and perform thermal and chemical parameter tests on the cable material samples to obtain material test data; Based on the material test data, relevant parameters of pyrolysis and gas phase products were extracted, a pyrolysis model of cable material was constructed, and the combustion chemical equations of combustible gas phase products in the pyrolysis model were balanced. By integrating time-varying arc ignition sources, pyrolysis models, combustion chemical equations, and material test data, a fault risk assessment model for high-voltage cable arcs was constructed. Using a fault risk assessment model, characteristic parameters characterizing the intensity of cable combustion are calculated, and the risk level of cable ignition by electric arc is determined based on these characteristic parameters.

[0007] Furthermore, an electrical characteristic calculation model for arc faults in overhead-cable hybrid lines is constructed. This model is used to obtain voltage and current characteristic data for cable arc faults under different relay protection strategies, including: A basic model of an overhead line-cable hybrid line is constructed, and a short-circuit arc model and a latent arc model are introduced into the basic model to obtain an electrical characteristic calculation model. The short-circuit arc model and the latent arc model have a pre-set correspondence between the opening and closing states of the line circuit breaker and the control priority of the variable resistor. The correspondence is adapted to the action logic of different relay protection strategies. Based on the correspondence, the control priority of the variable resistor is automatically switched according to the actual opening and closing state of the circuit breaker, and the simulation of cable arc fault under different relay protection strategies is carried out to obtain voltage characteristic data and current characteristic data.

[0008] Furthermore, a cable arc fault model was constructed, and voltage and current characteristic data were used as input parameters. Through model simulation, the relationship between cable arc temperature and time under different relay protection strategies was obtained, including: Based on the magnetohydrodynamic model, a cable arc fault model matching the actual voltage level, size and structural parameters of high-voltage cables is constructed. In the cable arc fault model, a penetrating defect is set in the insulation layer of the middle section of the cable as an arcing channel, and open holes are set in the metal sheath and outer sheath of the cable to simulate the air arcing environment of latent arcing. Voltage characteristic data and current characteristic data are imported as input parameters into the cable arc fault model; For each relay protection strategy, simulations were performed using a cable arc fault model to obtain the relationship between cable arc temperature and time under the corresponding strategy.

[0009] Furthermore, cable material samples matching the simulation object are obtained, and thermal and chemical parameters of the cable material samples are tested to obtain material test data, including: Select a sample whose high-voltage cable material is exactly the same as that of the simulation object as the cable material sample; the sample shall contain at least the cable insulation layer material and the outer sheath layer material. Thermogravimetric analysis was performed on the cable material samples. The number of pyrolysis reactions, the percentage of remaining mass after each pyrolysis reaction, the start and end temperatures of the pyrolysis reaction, and the reference temperature corresponding to the point of maximum pyrolysis reaction rate for each reaction were recorded. Gas phase product tests were performed on cable material samples at a reference temperature to obtain the composition and corresponding peak area of ​​the gas phase products generated by pyrolysis at the reference temperature. By integrating the results of thermogravimetric analysis and gas phase product testing, material testing data were obtained.

[0010] Furthermore, based on material testing data, relevant parameters of pyrolysis and gaseous products are extracted to construct a pyrolysis model for the cable material, including: Based on the peak area of ​​the gaseous products, the molar percentage of each gaseous product is calculated. The gaseous products are divided into long-chain hydrocarbons and short-chain hydrocarbons. Long-chain hydrocarbons are gases with more than 15 carbon atoms and exist in the form of flue gas. Select the top five gaseous products from short-chain hydrocarbons by molar percentage. The mass percentages of the top five short-chain hydrocarbon gaseous products, the flue gas corresponding to long-chain hydrocarbons, and the solid residues after pyrolysis were normalized to obtain the percentage of each product in the pyrolysis model. Based on the percentage of each product, a pyrolysis model of cable materials containing pyrolysis gaseous products, flue gas, and solid residues was constructed.

[0011] Furthermore, the combustion chemical equations for the combustible gas phase products in the balanced pyrolysis model include: Obtain the chemical and combustion parameters of the top five short-chain hydrocarbon gaseous products; Based on the volume fractions of oxygen, nitrogen, moisture, and carbon dioxide in the background gas, and combined with the molar percentages, balance the combustion chemical equations of the top five short-chain hydrocarbon gaseous products in the background gas.

[0012] Furthermore, after balancing the combustion chemical equations for the combustible gas phase products in the pyrolysis model, it also includes: The thermal conductivity and specific heat capacity of the cable material sample were measured at different temperature points before the pyrolysis reaction to obtain the temperature change parameters. Temperature change parameters are integrated into material test data to build a fault risk assessment model for high-voltage cable arcing.

[0013] Secondly, the present invention provides a high-voltage cable arc fault risk assessment device based on a dynamic ignition source and a cable pyrolysis combustion model, comprising: The electrical parameter acquisition module is used to construct an electrical characteristic calculation model for arc faults in overhead-cable hybrid lines, and to obtain voltage and current characteristic data of cable arc faults under different relay protection strategies using the electrical characteristic calculation model. The dynamic arc source construction module is used to construct a cable arc fault model. It takes voltage characteristic data and current characteristic data as input parameters, obtains the relationship between cable arc temperature and time under different relay protection strategies through model simulation, and constructs a time-varying arc source based on the relationship. The test data acquisition module is used to acquire cable material samples that match the simulation object, and to test the thermal and chemical parameters of the cable material samples to obtain material test data. The pyrolysis model construction and combustion equation balancing module is used to extract relevant parameters of pyrolysis and gaseous products based on material test data, construct a pyrolysis model of cable materials, and balance the combustion chemical equations of combustible gaseous products in the pyrolysis model. The risk assessment model construction module is used to integrate time-varying arc ignition sources, pyrolysis models, combustion chemical equations, and material test data to construct a fault risk assessment model for high-voltage cable arcs. The arc fault risk assessment module is used to calculate characteristic parameters that characterize the intensity of cable combustion using a fault risk assessment model, and to determine the risk level of the cable being ignited by an electric arc based on the characteristic parameters.

[0014] Thirdly, the present invention provides a computer device, the device including a processor and a memory: The memory is used to store computer programs and send the instructions of the computer programs to the processor; The processor executes instructions from a computer program, such as the first aspect, a method for assessing the risk of arc faults in high-voltage cables based on a dynamic fire source and a cable pyrolysis combustion model.

[0015] Fourthly, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements a high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model, as described in the first aspect.

[0016] In summary, this invention provides a method and apparatus for risk assessment of high-voltage cable arc faults based on a dynamic ignition source and a cable pyrolysis combustion model. The method includes the following steps: constructing an electrical characteristic calculation model for arc faults in overhead line-cable hybrid lines; using the electrical characteristic calculation model to obtain voltage and current characteristic data of cable arc faults under different relay protection strategies; constructing a cable arc fault model, using the voltage and current characteristic data as input parameters; obtaining the time-varying relationship of cable arc temperature under different relay protection strategies through model simulation; and constructing a time-varying arc ignition source based on this relationship. This invention involves acquiring cable material samples matching the simulation object and conducting thermal and chemical parameter tests on the samples to obtain material test data. Based on the material test data, relevant parameters of pyrolysis and gaseous products are extracted to construct a pyrolysis model of the cable material, and the combustion chemical equations of combustible gaseous products in the pyrolysis model are balanced. A fault risk assessment model for high-voltage cable arcs is constructed by integrating a time-varying arc source, the pyrolysis model, the combustion chemical equations, and the material test data. Using the fault risk assessment model, characteristic parameters characterizing the intensity of cable combustion are calculated, and the risk level of cable ignition by arc is determined based on these characteristic parameters. This invention solves the problem of significant discrepancies between existing assessment methods and actual conditions caused by the use of static heat sources and neglect of material evolution processes. It can accurately determine the risk of cable arc ignition, providing a reliable basis for adaptive reclosing optimization and cable fire protection design. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of a high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model is provided for embodiments of the present invention. Figure 2A flowchart illustrating the risk assessment method for high-voltage cable arc faults under four protection strategies provided in this embodiment of the invention; Figure 3 This invention provides a single-phase arc grounding fault model for a 220kV parallel hybrid line cable section. Figure 4 Arc voltage waveform diagram provided for this invention; Figure 5 The arc current waveform diagram provided for this invention; Figure 6 A graph showing the relationship between the arc temperature of a cable under single-phase reclosing and time, provided by the present invention. Figure 7 Thermogravimetric analysis results of cable main insulation material provided for this invention; Figure 8 The thermal conductivity curve of the main insulation material of the cable provided by this invention; Figure 9 The specific heat capacity curve of the cable main insulation material provided by the present invention; Figure 10 Longitudinal temperature slice diagram of cable combustion process under single-phase reclosing condition when the main protection action is activated, provided by the present invention; Figure 11 The present invention provides HRR curves for cable combustion under four different relay protection strategies. Figure 12 A block diagram of a high-voltage cable arc fault risk assessment device based on a dynamic fire source and a cable pyrolysis combustion model provided in this embodiment of the invention; Figure 13 This is a block diagram of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] Please see Figure 1 This embodiment provides a method for assessing the risk of arc faults in high-voltage cables based on a dynamic ignition source and a cable pyrolysis combustion model, including the following steps: S11: Construct an electrical characteristic calculation model for arc faults in overhead-cable hybrid lines, and use the electrical characteristic calculation model to obtain voltage and current characteristic data of cable arc faults under different relay protection strategies.

[0021] It should be noted that overhead line-cable hybrid lines refer to transmission lines composed of overhead transmission lines and underground cable lines; the electrical characteristic calculation model for arc faults is a mathematical model used to simulate and calculate the changes in electrical parameters such as voltage and current in the line when an arc fault occurs; relay protection strategies refer to the protection action schemes set in the power system to deal with faults (such as short circuits and arc faults); voltage characteristic data and current characteristic data refer to the time-series data of voltage and current changes over time at the fault point and key nodes of the line after an arc fault occurs.

[0022] Arc faults are essentially electrical discharge phenomena. Their thermal characteristics, such as combustion intensity and temperature changes, are directly determined by electrical parameters. Furthermore, different relay protection strategies (such as whether reclosing is initiated and the length of the initiation delay) alter the duration and energy input intensity of the arc. Therefore, this step first constructs a calculation model of the electrical characteristics of arc faults covering overhead line-cable hybrid line structures. This model needs to consider factors such as changes in line impedance, distributed capacitance, and arc resistance over time. Then, this model is used to simulate the fault process under different relay protection strategies, extracting the corresponding voltage and current characteristic data.

[0023] S12: Construct a cable arc fault model, and use voltage characteristic data and current characteristic data as input parameters. Through model simulation, obtain the relationship between cable arc temperature and time under different relay protection strategies, and construct a time-varying arc source based on the relationship.

[0024] It should be noted that the cable arc fault model is a simulation model that integrates the electrical and thermal characteristics of an arc, used to describe the transformation of electrical parameters into thermal parameters during the occurrence and development of an arc fault. The time-varying arc source model is an arc source model in which parameters such as temperature and thermal power dynamically change over time.

[0025] The temperature change of an electric arc directly depends on the consumption of electrical energy, which is determined by voltage and current characteristics. This step uses voltage and current characteristic data as input to construct a cable arc fault model. This model uses electromagnetic-thermal coupling simulation to convert electrical parameters into thermal parameters and calculates the dynamic change curve of arc temperature over time under different relay protection strategies. Based on this dynamic change curve, the time-series characteristics of the ignition source temperature and the time-series characteristics of thermal radiation intensity are extracted to construct a time-varying arc ignition source.

[0026] S13: Obtain a cable material sample that matches the simulation object, and perform thermal and chemical parameter tests on the cable material sample to obtain material test data.

[0027] It should be noted that the cable material sample is a small material specimen cut from a cable with the same material and structure as the simulation object (target high-voltage cable); thermal and chemical parameter testing refers to the thermal and chemical performance tests conducted on the cable material sample. Thermal parameters include specific heat capacity, thermal conductivity, thermal diffusivity, pyrolysis temperature, etc., while chemical parameters include elemental composition, composition and content of pyrolysis products, heat of combustion, etc. The material test data are the raw and derived data characterizing the thermal and chemical properties of the cable material obtained through the above tests.

[0028] The process of a cable being ignited by an electric arc is essentially a chain reaction in which the material undergoes pyrolysis at high temperatures, producing combustible gases, which then burn. This process is directly related to the thermal and chemical properties of the cable material. This step first selects a cable material sample matching the simulation object to ensure the representativeness of the test data. Then, using specialized equipment such as a simultaneous thermal analyzer, STA-FTIR-GC / MS (simultaneous thermal analysis infrared gas chromatography-mass spectrometry), and a laser thermal conductivity meter, thermal and chemical parameter tests are conducted to obtain the thermal response and chemical change patterns of the material at different temperatures.

[0029] S14: Extract relevant parameters of pyrolysis and gaseous products based on material test data, construct a pyrolysis model of cable materials, and balance the combustion chemical equations of combustible gaseous products in the pyrolysis model.

[0030] It should be noted that the pyrolysis parameters include the number of pyrolysis reactions, the percentage of remaining mass after each pyrolysis reaction, the start and end temperatures of the pyrolysis reaction, and the reference temperature corresponding to the point of maximum pyrolysis reaction rate. These parameters are used to describe the stage characteristics of the material pyrolysis process, the change in remaining mass, and key temperature nodes. The gas phase product parameters include the types, contents, and classification information of gases produced by pyrolysis.

[0031] The pyrolysis model of cable materials is a mathematical model built based on the pyrolysis mechanism of materials and test data. It is used to simulate the process of thermal decomposition of cable materials and generation of gaseous products under high temperature environment.

[0032] Balancing combustion chemical equations involves adjusting the stoichiometric coefficients of reactants and products in the combustion reaction equation of combustible gases according to the law of conservation of mass, so that the number of atoms of each element is equal before and after the reaction, thus ensuring the accuracy of the stoichiometric relationship in the combustion process.

[0033] The pyrolysis process of cable materials is a crucial step connecting the electric arc heat source with cable combustion, and existing evaluation methods suffer from bias due to neglecting this process. This step first extracts parameters such as pyrolysis rate, types and quantities of gaseous products from material test data; then, based on these parameters, constructs a pyrolysis model of the cable material that includes pyrolysis gaseous products, flue gas, and solid residues; finally, analyzes the combustion reaction mechanism of the combustible gas mixture produced by pyrolysis, balances the corresponding combustion chemical equations, and clarifies the energy release and product formation patterns during combustion.

[0034] S15: Integrating time-varying arc ignition sources, pyrolysis models, combustion chemical equations, and material test data, a fault risk assessment model for high-voltage cable arcs is constructed.

[0035] It should be noted that the fault risk assessment model for high-voltage cable arcs is a comprehensive simulation model that integrates dynamic fire sources, material pyrolysis, combustion reactions, and material properties. It can realize dynamic simulation of the entire process from the occurrence of arc faults to cable ignition and quantitatively assess fault risks.

[0036] This step can use a time-varying electric arc source as a heat source input, a pyrolysis model as a material evolution module, and a balanced combustion chemical equation as a reaction rule for the combustion of combustible gases. At the same time, material test data (such as specific heat capacity, thermal conductivity, etc.) are incorporated as the basic parameters of the model. Through multi-physics coupling (electromagnetic-thermal-chemical coupling) technology, the various parts are integrated to form a fault risk assessment model for high-voltage cable arcs.

[0037] S16: Using a fault risk assessment model, calculate characteristic parameters that characterize the intensity of cable combustion, and determine the risk level of the cable being ignited by an electric arc based on the characteristic parameters.

[0038] It should be noted that the characteristic parameters are parameters used to quantitatively describe the burning intensity of the cable, including burning rate, maximum burning temperature, heat release rate, peak combustible gas production, and burning duration.

[0039] Risk level refers to the degree of risk of a cable being ignited by an electric arc, classified according to the numerical range of characteristic parameters (such as low risk, medium risk, high risk, and extremely high risk).

[0040] This step utilizes a fault risk assessment model to simulate the entire process of a cable from contact with an electric arc to combustion under different relay protection strategies. It can calculate characteristic parameters that characterize the intensity of combustion, such as combustion rate, maximum combustion temperature, and heat release rate. Then, based on actual engineering needs, risk thresholds for each characteristic parameter are set (e.g., if the maximum combustion temperature exceeds a certain value, it is judged as high risk). Based on these thresholds, the risk level of the cable being ignited by the electric arc is determined.

[0041] This embodiment provides a risk assessment method for high-voltage cable arc faults based on a dynamic ignition source and a cable pyrolysis combustion model. This method overcomes the limitations of existing assessment methods that use static heat sources. By constructing an electrical characteristic calculation model, electrical parameters are transformed into dynamic temperature change relationships. It innovatively constructs a time-varying arc ignition source to accurately reflect the transient temperature changes and dynamic heat source input characteristics of arc faults. Secondly, the pyrolysis combustion process of cable materials is systematically integrated into the risk assessment. By obtaining the thermal and chemical parameters of the materials through actual measurements, an accurate pyrolysis model of the cable materials is constructed and the combustion chemical equation is balanced. This restores the material evolution law during the cable ignition process and solves the problem of large assessment deviations caused by neglecting material evolution in existing methods.

[0042] In one embodiment of the present invention, an electrical characteristic calculation model for arc faults in overhead line-cable hybrid lines is constructed. This model is used to obtain voltage and current characteristic data of cable arc faults under different relay protection strategies, including: S21: Construct a basic model of an overhead line-cable hybrid line, and introduce a short-circuit arc model and a latent arc model into the basic model to obtain an electrical characteristic calculation model; the short-circuit arc model and the latent arc model have a pre-set correspondence between the opening and closing states of the line circuit breaker and the control priority of the variable resistor, and the correspondence is adapted to the action logic of different relay protection strategies.

[0043] This step involves building a basic model of an overhead-cable hybrid line using circuit simulation software. The basic model must accurately match the actual line's topology, line parameters (such as impedance and distributed capacitance), and the voltage level and specifications of the high-voltage cable. Then, two custom components, a "short-circuit arc model" and a "latent arc model," are introduced into this basic model to obtain the electrical characteristic calculation model. When introducing these two arc models, the correspondence between the circuit breaker's opening and closing states and the control priority of the variable resistor must be pre-defined. For example, it can be set that "when the circuit breaker is closed, the variable resistor corresponding to the short-circuit arc model is controlled first; when the circuit breaker is open, the variable resistor corresponding to the latent arc model is controlled first." This correspondence must be compatible with the action logic of different relay protection strategies (such as single-phase reclosing, three-phase reclosing, etc.) to ensure that the model can respond to the circuit breaker action sequence under different protection strategies.

[0044] S22: Based on the correspondence, the control priority of the variable resistor is automatically switched according to the actual opening and closing state of the line circuit breaker to simulate cable arc faults under different relay protection strategies, and obtain voltage characteristic data and current characteristic data.

[0045] This step first calls the above correspondence to monitor the actual opening and closing status of the circuit breaker in real time (e.g., through the status monitoring module of the simulation software). Based on the monitored actual opening and closing status, the model will automatically switch the control priority of the variable resistor in the short-circuit arc model and the latent arc model. For example, when the circuit breaker is detected to be closed due to a short-circuit fault, the variable resistor of the short-circuit arc model is switched to priority control to simulate the short-circuit arc fault process. When the circuit breaker is detected to be open and entering the reclosing gap, the variable resistor of the latent arc model is switched to priority control to simulate the latent arc fault process. Based on the above priority switching logic, the cable arc fault process under each relay protection strategy is simulated. After the simulation is completed, the voltage and current curves of the fault point and key nodes of the line during the fault process are extracted through the data output module of the simulation software. Then, the voltage characteristic data and current characteristic data corresponding to different relay protection strategies are obtained.

[0046] This embodiment can simulate the fault process of short-circuit arc and latent arc under different protection strategies. The obtained voltage characteristic data and current characteristic data can be used to construct a time-varying arc source.

[0047] In one embodiment of the present invention, a cable arc fault model is constructed, and voltage characteristic data and current characteristic data are used as input parameters. The model simulation is used to obtain the relationship between cable arc temperature and time under different relay protection strategies, including: S31: Based on the magnetohydrodynamic model, construct a cable arc fault model that matches the actual voltage level, size and structural parameters of high-voltage cables.

[0048] This step is based on magnetohydrodynamics (MHD) theory and uses multiphysics simulation software as the modeling tool. During the modeling process, the parameters of the actual high-voltage cable must be strictly matched, including the cable's voltage level (such as 220kV, 110kV, etc.), specific dimensional parameters (such as insulation layer thickness, outer diameter of the metal sheath, outer sheath thickness, etc.), and structural parameters (such as the hierarchical distribution of conductor, insulation layer, metal sheath, and outer sheath) to ensure that the model can truly reflect the physical characteristics of the actual cable.

[0049] S32: In the cable arc fault model, a penetrating defect is set in the insulation layer of the middle section of the cable as an arcing channel, and open holes are set in the metal sheath and outer sheath of the cable to simulate the latent arcing air arcing environment.

[0050] This step first involves locating the insulation layer area in the middle section of the cable within the constructed cable arc fault model. A penetrating defect with a radius of 2mm can be set, which serves as the arcing channel for the arc fault, simulating the physical space generated by the arc after the actual cable insulation layer is damaged. Subsequently, open holes are set at the locations corresponding to the arcing channel in the cable's metal sheath and outer sheath. The diameter of the holes can be determined according to 0.5 times the width of one cycle of air gap. The function of these holes is to simulate the opening structure formed when the metal sheath is melted by a short-circuit arc in actual working conditions, thereby providing an arcing environment in contact with air for the latent arc.

[0051] S33: Import voltage characteristic data and current characteristic data as input parameters into the cable arc fault model.

[0052] This step first extracts voltage and current characteristic data (such as voltage-time curves, current-time curves, and other time-series data); then, through the data import interface of the multiphysics simulation software, the above voltage and current characteristic data are used as electrical excitation parameters and imported into the corresponding ports of the cable arc fault model (such as the electrical interfaces at both ends of the cable conductor) to ensure that the input parameters can directly drive the model to perform electromagnetic-thermal coupling simulation of arc faults.

[0053] S34: For each relay protection strategy, simulations are performed using a cable arc fault model to obtain the relationship between the cable arc temperature and time under the corresponding strategy.

[0054] This step involves simulating the cable arc fault model for each relay protection strategy. During the simulation, the model uses magnetohydrodynamic coupling calculations based on the input voltage and current characteristic data to obtain the time-series temperature change data of the arc at the fault location. After the simulation, the software's data output module extracts the temperature-time correspondence data for each strategy (which can be exported as a table or curve), ultimately yielding the relationship between cable arc temperature and time under different relay protection strategies.

[0055] This embodiment constructs a realistic cable arc fault model based on magnetohydrodynamics theory. By setting up an arc channel and a potential arc environment, and importing real arc electrical characteristic data, it realizes the simulation of the cable arc temperature change process under different relay protection strategies. The obtained arc temperature change relationship with time can be used to construct a time-varying arc source.

[0056] In one embodiment of the present invention, a cable material sample matching the simulation object is obtained, and thermal and chemical parameters of the cable material sample are tested to obtain material test data, including: S41: Select a sample whose high-voltage cable material is completely identical to that of the simulation object as the cable material sample; the sample shall contain at least the cable insulation layer material and the outer sheath layer material.

[0057] This step first clarifies the specific information of the high-voltage cable being simulated, including voltage level, size specifications, manufacturer, and materials of each structural layer (e.g., the insulation layer is cross-linked polyethylene, and the outer sheath layer is polyvinyl chloride). Then, a sample is taken from a cable with the same material formula and manufacturing process as the simulation object, serving as the cable material sample. During the sampling process, it is essential to ensure that the sample retains all major structural layers, including at least the insulation and outer sheath materials, to avoid deviations in pyrolysis combustion characteristic testing due to material differences, thus ensuring the accuracy of subsequent model input parameters from the outset.

[0058] S42: Perform thermogravimetric analysis on the cable material sample, and record the number of pyrolysis reactions, the percentage of remaining mass after each pyrolysis reaction, the start and end temperatures of the pyrolysis reaction, and the reference temperature corresponding to the point of maximum pyrolysis reaction rate for each reaction.

[0059] This step involves pre-treating the cable material sample (e.g., cutting it into uniform small pieces, drying and removing impurities), then placing the sample into the test chamber of the synchronous thermal analyzer; setting a reasonable heating program (e.g., uniform heating, inert atmosphere protection to prevent sample oxidation during testing), and starting the instrument for thermogravimetric analysis; during the test, key data must be recorded, including the number of pyrolysis reactions during the material heating process, the remaining mass percentage after each pyrolysis reaction, the start and end temperatures of each pyrolysis reaction, and the reference temperature, i.e., the temperature corresponding to the maximum pyrolysis reaction rate for each reaction (the pyrolysis reaction rate is calculated by differentiating the remaining mass percentage of the pyrolysis reaction with respect to temperature); if the material undergoes multiple pyrolysis reactions, the reference temperature for each reaction must be recorded separately.

[0060] S43: Perform gas phase product testing on cable material samples at the reference temperature to obtain the composition and corresponding peak area of ​​the gas phase products generated by pyrolysis at the reference temperature.

[0061] This step begins by retrieving reference temperatures and placing the pretreated cable material sample into the simultaneous thermal analysis module of the coupled instrument. The instrument is set to STA-FTIR-GC / MS mode, and the temperature is increased according to the aforementioned heating program. When the sample temperature reaches a certain reference temperature, the gaseous products generated by pyrolysis are controlled to enter the Fourier transform infrared absorption spectrometer for spectral scanning to preliminarily identify the product types. Subsequently, the instrument is switched to offline gas chromatography-mass spectrometry (GC-MS) mode, allowing the gaseous products at that reference temperature to be separated by a gas chromatography column and then detected by the mass spectrometer. After the test, the main components of the gaseous products retrieved by the mass spectrometer and the peak areas left by each component on the gas chromatography column are recorded to characterize the relative content of each gaseous product. The gaseous product tests at all reference temperature points are completed sequentially according to the above procedure, significantly improving the effectiveness and relevance of the data.

[0062] S44: Integrate thermogravimetric analysis results and gas phase product test results to obtain material test data.

[0063] This step organizes the data obtained from thermogravimetric analysis, such as the number of pyrolysis reactions, percentage of remaining mass, pyrolysis start and end temperatures, and reference temperatures, into a thermal parameter table; and organizes the data obtained from gas phase product testing, such as product composition and corresponding peak area at each reference temperature, into a chemical parameter table; then, the two types of parameter tables are linked and integrated (e.g., matching thermal parameters and gas phase product parameters according to reference temperatures) to form complete material testing data.

[0064] This innovative step involves first obtaining the reference temperature through thermogravimetric analysis, and then conducting targeted gaseous product testing, which solves the problems of poor targeting and low data validity in traditional gaseous testing. At the same time, the sampling principle of being completely consistent with the material of the simulation object ensures the authenticity of the data from the source.

[0065] In a further embodiment of the present invention, a pyrolysis model of the cable material is constructed by extracting relevant parameters of pyrolysis and gaseous products based on material test data, including: S51: Calculate the molar percentage of each gaseous product based on the peak area of ​​the gaseous product.

[0066] The pyrolysis of cable materials produces a wide variety of gaseous products, leaving dozens of peaks on a gas chromatography column. Considering the computational limitations of fire simulation software, this embodiment innovatively uses a portion of the gaseous products with a relatively large molar percentage as the representative gaseous products of the material pyrolysis. Since the peak areas measured on the STA-FTIR-GC / MS gas chromatography column are typically the mass percentages of each component of the gaseous product, a conversion is necessary. The specific conversion formula is as follows:

[0067] in: For the first i Mass percentage of the gaseous products; For the first i Peak areas of the gaseous products on the gas chromatographic column in a STA-FTIR-GC / MS system; k For mass spectrometers retrieved in the STA-FTIR-GC / MS system k There are several gaseous products. Assuming the total mass of all gaseous products from pyrolysis is 100g, then the following can be calculated: k The molar ratio of the gaseous products:

[0068] in: The first in 100g of gaseous products i The amount of substance of the gaseous product; For the first i The molar mass of the gaseous product; The first gaseous product of cable material pyrolysis i species Molar percentage of gaseous products.

[0069] S52: The gaseous products are divided into long-chain hydrocarbons and short-chain hydrocarbons, of which long-chain hydrocarbons are gases with more than 15 carbon atoms and exist in the form of flue gas.

[0070] All calculations were obtained k After determining the molar percentage of the pyrolysis products of the cable material, the gaseous products are sorted according to the molar percentage. This embodiment innovatively classifies long-chain hydrocarbons and short-chain hydrocarbons in the gaseous products of cable material pyrolysis. Long-chain hydrocarbons are defined as gases with a carbon atom content of more than 15. These gases are difficult to burn in the low-oxygen environment of tunnels and generally exist in the form of flue gas.

[0071] S53: Select the top five gaseous products from short-chain hydrocarbons by molar percentage.

[0072] Select the top five pyrolysis gaseous products a-e from short-chain hydrocarbons by their molar percentage.

[0073] S54: Normalize the mass percentages of the top five short-chain hydrocarbon gaseous products, the flue gas corresponding to long-chain hydrocarbons, and the solid residues after pyrolysis to obtain the percentage of each product in the pyrolysis model.

[0074] Since the pyrolysis model in fire simulation software uses mass percentages, when constructing a cable pyrolysis model, it is also necessary to normalize the mass percentages of the remaining solid products after material pyrolysis, long-chain hydrocarbons existing in the form of flue gas, and the five pyrolysis gaseous products a-e with the highest molar percentages, as follows:

[0075] in: and These represent the mass percentages of long-chain and short-chain hydrocarbons in the gaseous products of cable material pyrolysis. The percentage by mass of gaseous product a in the total pyrolysis gaseous products of the cable materials. Normalized mass percentage of the top five pyrolysis gaseous products a-e, ranked by the percentage of substance of gaseous product a. is the percentage of gaseous product a in the cable material pyrolysis model in the fire simulation software; the other four gaseous products be are calculated in the same way. This represents the mass percentage of pyrolysis solid residue (ash) of the cable material during thermogravimetric analysis, and also the percentage of pyrolysis solid residue (ash) in the cable material pyrolysis model in fire simulation software. This represents the percentage of long-chain hydrocarbons existing in the form of flue gas in the pyrolysis model of cable materials in fire simulation software.

[0076] S55: Based on the percentage of each product, a pyrolysis model of cable material containing pyrolysis gaseous products, flue gas, and solid residues is constructed.

[0077] The constructed pyrolysis model of the cable material is shown in Table 1: Table 1. Pyrolysis Model of Cable Materials in FDS

[0078] This embodiment constructs a cable material pyrolysis model adapted to fire simulation software; by adopting a product classification and screening strategy, it not only solves the problem of insufficient calculation performance of fire simulation software due to too many types of products in traditional models, but also ensures the representativeness of core combustible gas phase products.

[0079] In a further embodiment of the present invention, the combustion chemical equation for the combustible gas phase products in the balanced pyrolysis model includes: S61: Obtain the chemical and combustion parameters of the top five short-chain hydrocarbon gaseous products.

[0080] For chemical parameters, the chemical formula (either the simplest formula or the experimental formula) and relative molecular mass of each product need to be obtained. This can be confirmed by consulting chemical handbooks, standard databases, or experimental determination. For combustion parameters, collect five core parameters for each product: auto-ignition point, combustion product ID, smoke production rate in the background gas, CO production rate in the background gas, and heat of combustion in the background gas. The parameter sources should preferably be measured data that match the simulation scenario (such as a cable tunnel environment) to ensure that the parameters can truly reflect the combustion characteristics of the product under actual working conditions.

[0081] S62: Based on the volume fractions of oxygen, nitrogen, moisture, and carbon dioxide in the background gas, and combined with the molar percentages, balance the combustion chemical equations of the first five short-chain hydrocarbon gaseous products in the background gas.

[0082] This step first clarifies the composition and volume fraction of the background combustion gas corresponding to the simulation, focusing on determining the specific volume fractions of the four core components: oxygen, nitrogen, moisture, and carbon dioxide. Then, the molar percentages of the first five short-chain hydrocarbon gaseous products are retrieved. Based on the laws of conservation of mass and atoms, and combined with the volume fractions of each component in the background gas, the reaction ratio of each short-chain hydrocarbon with oxygen in the background gas is adjusted one by one. Simultaneously, the inert / coexisting components such as nitrogen, moisture, and carbon dioxide are taken into account, as they do not participate in the combustion reaction. Finally, the stoichiometric coefficients of the reactants (short-chain hydrocarbons, oxygen) and products (carbon dioxide, water, a small amount of CO, flue gas, etc.) are determined, and the combustion chemical equation is balanced. After balancing, it is necessary to verify whether the total number of atoms of each element (C, H, O, etc.) is equal before and after the reaction to ensure the accuracy of the balancing result.

[0083] This embodiment incorporates the volume fractions of components such as oxygen and nitrogen in the actual combustion environment, ensuring the consistency between the combustion equation and real working conditions. The balanced combustion chemical equation provides accurate combustion reaction rules for fire simulation software, ensuring the realism of the cable combustion process simulation.

[0084] In a further embodiment of the present invention, after balancing the combustion chemical equations of the combustible gas phase products in the pyrolysis model, the method further includes: S71: Measure the thermal conductivity and specific heat capacity of the cable material sample at different temperature points before the pyrolysis reaction to obtain temperature change parameters.

[0085] This step can use an LFA447 laser thermal conductivity analyzer as the testing tool. First, select a cable material sample consistent with the one tested previously and pre-treat it (e.g., cut it into a uniform sample that meets the instrument's testing specifications, dry it to remove impurities and moisture to avoid affecting the testing accuracy). Then, define the test temperature range, i.e., only cover the temperature range before the cable material undergoes pyrolysis, and select several typical temperature points within this range. Place the pre-treated sample on the test stage of the LFA447 laser thermal conductivity analyzer, set the instrument's test parameters, and measure the thermal conductivity and specific heat capacity at each temperature point in sequence. After the test is completed, record the corresponding thermal conductivity and specific heat capacity values ​​for each temperature point.

[0086] S72: Integrate temperature change parameters into material test data to build a fault risk assessment model for high-voltage cable arcing.

[0087] This step integrates temperature change parameters with existing data to form a unified structured material test dataset. The integrated material test data can be directly used as the basic input parameters for the subsequent construction of a high-voltage cable arc fault risk assessment model.

[0088] This embodiment integrates temperature change parameters into the material test data, making the dataset more comprehensively cover the core thermal and chemical properties of cable materials.

[0089] Please see Figure 2 , Figure 2 This paper presents a detailed implementation process for a high-voltage cable arc fault risk assessment method under four protection strategies. The process aims to assess the ignition risk of high-voltage cable arc faults. First, a cable arc fault simulation model is built, using the arc voltage and current under four relay protection strategies as excitation. On one hand, the arc temperature change is obtained through a 220kV cable arc fault magnetohydrodynamic model, thus constructing a dynamic arc ignition source model. On the other hand, thermogravimetric analysis, pyrolysis gaseous product analysis, and thermal conductivity and specific heat parameter measurements are conducted on the insulation layer and outer sheath materials of the 220kV XLPE cable. Based on these tests, a high-voltage cable pyrolysis combustion model incorporating solid pyrolysis is constructed. Finally, the dynamic arc ignition source and the pyrolysis combustion model are integrated into a cable arc ignition calculation model under the four protection strategies. By calculating parameters such as the combustion flame temperature distribution and heat release rate, it is determined whether the cable has been ignited, thus completing the arc fault ignition risk assessment for overhead line-cable hybrid line sections.

[0090] The implementation of the present invention will be described in detail below with reference to an example.

[0091] Taking a typical scenario as a double-circuit 220kV overhead-cable hybrid line equipped with an automatic reclosing device, a cable arc fault simulation model was built in circuit simulation software. Figure 3 As shown.

[0092] Taking single-phase reclosing as an example, the arc voltage and current waveforms obtained through the above model simulation are as follows: Figure 4 and Figure 5 As shown.

[0093] The arc voltage and current waveforms from 0ms to 3000ms under single-phase reclosing were fitted using piecewise functions. The fitting results are shown in the following equation:

[0094] Subsequently, based on MHD theory, a simulation model of arc fault in a 220kV high-voltage cable was established in a multiphysics field. Using the above-mentioned fitting results of cable arc voltage and current under single-phase single reclosing as input, the simulation obtained the relationship between the temperature at the location of the cable arc fault and time under single-phase single reclosing, as follows: Figure 6 As shown, the relationship between cable arc and temperature is used as a dynamic ignition source to further propose a method for assessing the risk of fire caused by cable arc faults.

[0095] Next, a cable pyrolysis combustion model was constructed, taking the insulation layer of a 220kV power cable as an example. The main material of this layer is cross-linked polyethylene (XLPE). After obtaining cable material samples, thermogravimetric analysis was performed on the material samples using a simultaneous thermal analyzer. The measurement results are as follows: Figure 7 As shown, the remaining mass percentage after the pyrolysis reaction The value is 0.008, and the reference temperature is 486.5℃. The following table shows the gaseous products generated by the material sample at the pyrolysis temperature (reference temperature) using a STA-FTIR-GC / MS instrument.

[0096] Table 2. Results of offline gas chromatography-mass spectrometry (GC-MS) analysis of cable main insulation materials.

[0097] According to the thermogravimetric analysis method of the foregoing embodiments, the total mass percentage of long-chain hydrocarbons classified and sorted is... The value is 0.23434; the top five gaseous products by molar percentage are: 1-hexene, 1-pentene, 1-heptene, n-heptane, and 1-octene. The following pyrolysis models of the main cable insulation material in FDS can be obtained through calculation, as shown in Table 3: Table 3. Pyrolysis Model of Cable Main Insulation Material in FDS

[0098] Assuming the background gas is air, the volume fractions of oxygen, nitrogen, moisture, and carbon dioxide in the background gas are shown in Table 4 below: Table 4. Volume fraction of combustion background gases

[0099] The chemical and combustion parameters of the five pyrolysis gaseous products are shown in Table 5: Table 5 Chemical and combustion parameters of five gaseous products

[0100] Based on the above parameters, the combustion reaction equations for the five pyrolysis gaseous products are balanced as shown in Table 6: Table 6 Combustion reaction equations for pyrolysis gaseous products

[0101] The thermal conductivity and specific heat capacity of cable materials at different temperatures before pyrolysis were measured using an LFA447 laser thermal conductivity analyzer. Figure 8 and Figure 9 As shown.

[0102] Based on the cable pyrolysis model, the temperature variation parameters of material thermal conductivity and specific heat capacity, and the combustion equation of gaseous products, a cable pyrolysis combustion model is constructed: First, the composition of the background gas and the proportion of each component are defined. Then, the relevant characteristics of non-combustible solid materials and the characteristics of combustible solid materials, the thermal parameters that change with temperature, and the configuration of pyrolysis products are clarified. Finally, for various combustible pyrolysis gases, their basic properties are determined in turn, and corresponding rules such as the composition of combustion reaction products, reaction stoichiometry, heat of combustion, and auto-ignition point are set.

[0103] Finally, combining the dynamic fire source of the cable and the cable pyrolysis combustion model, a risk assessment method for high-voltage cable arc faults in FDS (Fire Dynamics Simulator) is proposed. The simulation yields the flame temperature distribution during cable combustion under single-phase single reclosing, as shown below. Figure 10 As shown, (a)-(f) are longitudinal temperature slices of the cable combustion process at 300ms, 600ms, 1000ms, 1700ms, 2400ms and 3000ms, respectively.

[0104] Research found that under a single-phase reclosing strategy, the cable short-circuit arc ended after 300ms, while the latent arc ignition lasted for two cycles. (See details...) Figure 5 At this point, the highest flame temperature above the faulty cable was 1686.5℃. After entering the latent arc ignition stage, although the latent arc ignition temperature was significantly lower than that of the short-circuit arc, the heat generated by the latent arc continued to accumulate, keeping the flame temperature above the fault location at a consistently high level. At the moment the latent arc extinguished, i.e., 600ms, the highest flame temperature above the cable was 1457.8℃. At 1000ms, the cable arc fault entered the reclosing latent arc ignition stage. At this time, the temperature above the cable was significantly higher than in the short-circuit arc stage, with the highest flame temperature reaching 2744.3℃, further intensifying the cable combustion trend. After the cable arc fault extinguished, the cable was already ignited by the arc, and the highest flame temperature above the cable consistently fluctuated around 2000.0℃.

[0105] To further assess the risk of cable ignition due to arc faults, the heat release rate (HRR), a parameter characterizing the amount of heat released during combustion, was selected as the basis for determining whether high-voltage cables are ignited by arc faults. The HRR variation curves during cable arc faults under four types of relay protection strategies are shown below. Figure 11 As shown.

[0106] Depend on Figure 11It is known that the arcing process of the short-circuit arc under all four protection strategies will cause the high-voltage cable to be instantly ignited, and the peak value of the initial heat release rate of the four protection strategies is almost the same, about 195.0 kW. However, the reclosing short-circuit arc caused by the two reclosing methods will cause the cable to be instantaneously ignited a second time. Furthermore, since the outer sheath material has undergone the first pyrolysis during the first short-circuit arc stage, the second HRR peak value generated at this time will be greater than the HRR peak value during the arcing of the short-circuit arc.

[0107] Based on the same inventive concept, this application also provides a high-voltage cable arc fault risk assessment device based on a dynamic fire source and a cable pyrolysis combustion model for implementing the high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model described above. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations in the embodiments of the high-voltage cable arc fault risk assessment device based on a dynamic fire source and a cable pyrolysis combustion model provided below can be found in the limitations of the high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model described above, and will not be repeated here.

[0108] Please see Figure 12 This invention also provides a high-voltage cable arc fault risk assessment device based on a dynamic fire source and a cable pyrolysis combustion model, comprising: The electrical parameter acquisition module is used to construct an electrical characteristic calculation model for arc faults in overhead-cable hybrid lines, and to obtain voltage and current characteristic data of cable arc faults under different relay protection strategies using the electrical characteristic calculation model. The dynamic arc source construction module is used to construct a cable arc fault model. It takes voltage characteristic data and current characteristic data as input parameters, obtains the relationship between cable arc temperature and time under different relay protection strategies through model simulation, and constructs a time-varying arc source based on the relationship. The test data acquisition module is used to acquire cable material samples that match the simulation object, and to test the thermal and chemical parameters of the cable material samples to obtain material test data. The pyrolysis model construction and combustion equation balancing module is used to extract relevant parameters of pyrolysis and gaseous products based on material test data, construct a pyrolysis model of cable materials, and balance the combustion chemical equations of combustible gaseous products in the pyrolysis model. The risk assessment model construction module is used to integrate time-varying arc ignition sources, pyrolysis models, combustion chemical equations, and material test data to construct a fault risk assessment model for high-voltage cable arcs. The arc fault risk assessment module is used to calculate characteristic parameters that characterize the intensity of cable combustion using a fault risk assessment model, and to determine the risk level of the cable being ignited by an electric arc based on the characteristic parameters.

[0109] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the system can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0110] Reference Figure 13 The present invention also provides a computer device, including: a memory and a processor, and a computer program stored in the memory. When the computer program is executed on the processor, it implements the high-voltage cable arc fault risk assessment method based on dynamic fire source and cable pyrolysis combustion model as described in any of the above methods.

[0111] The computer device may be a desktop computer, laptop, handheld computer, or cloud server, etc. This computer device may include, but is not limited to, a processor and memory. Those skilled in the art will understand that... Figure 13 The examples of computer devices are merely examples and do not constitute a limitation on computer devices. They may include more or fewer components than shown in the illustration, or combinations of certain components, or different components. For example, they may also include input / output devices, network access devices, etc.

[0112] The processor referred to can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0113] In some embodiments, the memory may be an internal storage unit of the computer device, such as a hard drive or RAM. In other embodiments, the memory may be an external storage device of the computer device, such as a plug-in hard drive, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, the memory may include both internal and external storage units of the computer device. The memory is used to store the operating system, applications, boot loader, data, and other programs, such as the program code of the computer program. The memory can also be used to temporarily store data that has been output or will be output.

[0114] This invention also provides a computer-readable storage medium storing a computer program thereon. When the computer program is run by a processor, it implements the high-voltage cable arc fault risk assessment method based on a dynamic fire source and cable pyrolysis combustion model as described in any of the above methods.

[0115] In this embodiment, if the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying computer program code to a photographing device / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electrical carrier signals or telecommunication signals.

[0116] This invention provides a computer program product, including a computer program that, when executed by a processor, implements a high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model, as described in any of the above methods.

[0117] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0118] Those skilled in the art will recognize that the units and algorithm steps of the various examples 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 implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0119] In the embodiments disclosed in this application, it should be understood that the disclosed devices / terminal equipment and methods can be implemented in other ways. For example, the device / terminal equipment embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0120] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A risk assessment method for high-voltage cable arc faults based on a dynamic ignition source and a cable pyrolysis combustion model, characterized in that, Includes the following steps: An electrical characteristic calculation model for arc faults in overhead-cable hybrid lines is constructed, and the voltage and current characteristic data of cable arc faults under different relay protection strategies are obtained using the electrical characteristic calculation model. A cable arc fault model is constructed, and the voltage characteristic data and the current characteristic data are used as input parameters. The relationship between cable arc temperature and time under different relay protection strategies is obtained through model simulation, and a time-varying arc source is constructed based on the relationship. Obtain cable material samples that match the simulation object, and perform thermal and chemical parameter tests on the cable material samples to obtain material test data; Based on the material test data, relevant parameters of pyrolysis and gaseous products are extracted, a pyrolysis model of the cable material is constructed, and the combustion chemical equations of combustible gaseous products in the pyrolysis model are balanced. By integrating the time-varying electric arc source, the pyrolysis model, the combustion chemical equation, and the material test data, a fault risk assessment model for high-voltage cable arcs is constructed. Using the aforementioned fault risk assessment model, characteristic parameters characterizing the intensity of cable combustion are calculated, and the risk level of the cable being ignited by an electric arc is determined based on these characteristic parameters.

2. The high-voltage cable arc fault risk assessment method based on a dynamic ignition source and cable pyrolysis combustion model as described in claim 1, characterized in that, An electrical characteristic calculation model for arc faults in overhead-cable hybrid lines is constructed. This model is used to obtain voltage and current characteristic data for cable arc faults under different relay protection strategies, including: A basic model of an overhead line-cable hybrid line is constructed, and a short-circuit arc model and a latent arc model are introduced into the basic model to obtain the electrical characteristic calculation model. The short-circuit arc model and the latent arc model are preset with a correspondence between the opening and closing state of the line circuit breaker and the control priority of the variable resistor. The correspondence is adapted to the action logic of different relay protection strategies. Based on the aforementioned correspondence, the control priority of the variable resistor is automatically switched according to the actual opening and closing state of the circuit breaker, and the simulation of cable arc faults under different relay protection strategies is performed to obtain the voltage characteristic data and the current characteristic data.

3. The high-voltage cable arc fault risk assessment method based on a dynamic ignition source and cable pyrolysis combustion model as described in claim 1, characterized in that, A cable arc fault model is constructed, and the voltage characteristic data and current characteristic data are used as input parameters. The model simulation yields the relationship between cable arc temperature and time under different relay protection strategies, including: Based on the magnetohydrodynamic model, a cable arc fault model matching the actual voltage level, size and structural parameters of high-voltage cables is constructed. In the cable arc fault model, a penetrating defect is set in the insulation layer of the middle section of the cable as an arcing channel, and open holes are set in the metal sheath and outer sheath of the cable to simulate the latent arcing air arcing environment. The voltage characteristic data and the current characteristic data are imported as input parameters into the cable arc fault model; For each relay protection strategy, the cable arc fault model is used for simulation to obtain the relationship between the cable arc temperature and time under the corresponding strategy.

4. The high-voltage cable arc fault risk assessment method based on a dynamic ignition source and cable pyrolysis combustion model as described in claim 1, characterized in that, Obtain cable material samples that match the simulation object, and perform thermal and chemical parameter tests on the cable material samples to obtain material test data, including: A sample with the same high-voltage cable material as the simulation object is selected as the cable material sample; the sample contains at least the cable insulation layer material and the outer sheath layer material. Thermogravimetric analysis was performed on the cable material sample, and the number of pyrolysis reactions, the percentage of remaining mass after each pyrolysis reaction, the start and end temperatures of the pyrolysis reaction, and the reference temperature corresponding to the point of maximum pyrolysis reaction rate for each reaction were recorded. A gas phase product test was performed on a cable material sample at the reference temperature to obtain the composition and corresponding peak area of ​​the gas phase products generated by pyrolysis at the reference temperature. By integrating the thermogravimetric analysis results and the gas phase product test results, the test data of the material were obtained.

5. The high-voltage cable arc fault risk assessment method based on a dynamic ignition source and cable pyrolysis combustion model as described in claim 4, characterized in that, Based on the material test data, relevant parameters of pyrolysis and gaseous products are extracted, and a pyrolysis model of the cable material is constructed, including: Based on the peak area of ​​the gaseous products, the molar percentage of each gaseous product is calculated. The gaseous products are divided into long-chain hydrocarbons and short-chain hydrocarbons, wherein the long-chain hydrocarbons are gases with more than 15 carbon atoms, and the long-chain hydrocarbons exist in the form of flue gas. Select the top five gaseous products from the short-chain hydrocarbons by molar percentage. The mass percentages of the top five short-chain hydrocarbon gaseous products, the flue gas corresponding to long-chain hydrocarbons, and the solid residues after pyrolysis were normalized to obtain the percentage of each product in the pyrolysis model. Based on the percentage of each product, a pyrolysis model of cable materials containing pyrolysis gaseous products, flue gas, and solid residues was constructed.

6. The high-voltage cable arc fault risk assessment method based on a dynamic ignition source and cable pyrolysis combustion model as described in claim 5, characterized in that, Balance the combustion chemical equations for the combustible gas phase products in the pyrolysis model, including: Obtain the chemical and combustion parameters of the gaseous products of the first five short-chain hydrocarbons; Based on the volume fractions of oxygen, nitrogen, moisture, and carbon dioxide in the background gas, and in conjunction with the molar percentages of the substances, balance the combustion chemical equations of the first five short-chain hydrocarbon gaseous products in the background gas.

7. The high-voltage cable arc fault risk assessment method based on a dynamic ignition source and cable pyrolysis combustion model as described in claim 5, characterized in that, After balancing the combustion chemical equations for the combustible gas phase products in the pyrolysis model, the process also includes: The thermal conductivity and specific heat capacity of the cable material sample were measured at different temperature points before the pyrolysis reaction to obtain temperature change parameters. The temperature change parameters are integrated into the material test data to construct a fault risk assessment model for the high-voltage cable arc.

8. A high-voltage cable arc fault risk assessment device based on a dynamic ignition source and a cable pyrolysis combustion model, characterized in that, include: The electrical parameter acquisition module is used to construct an electrical characteristic calculation model for arc faults in overhead line-cable hybrid lines, and to use the electrical characteristic calculation model to obtain voltage characteristic data and current characteristic data of cable arc faults under different relay protection strategies. The dynamic arc source construction module is used to construct a cable arc fault model. It takes the voltage characteristic data and the current characteristic data as input parameters, obtains the relationship between the cable arc temperature and time under different relay protection strategies through model simulation, and constructs a time-varying arc source based on the relationship. The test data acquisition module is used to acquire cable material samples that match the simulation object, and to test the thermal and chemical parameters of the cable material samples to obtain material test data. The pyrolysis model construction and combustion equation balancing module is used to extract relevant parameters of pyrolysis and gas phase products based on the material test data, construct a pyrolysis model of the cable material, and balance the combustion chemical equations of the combustible gas phase products in the pyrolysis model. The risk assessment model construction module is used to integrate the time-varying electric arc source, the pyrolysis model, the combustion chemical equation, and the material test data to construct a fault risk assessment model for high-voltage cable arcs. The arc fault risk assessment module is used to calculate characteristic parameters that characterize the intensity of cable combustion using the fault risk assessment model, and to determine the risk level of the cable being ignited by an electric arc based on the characteristic parameters.

9. A computer device, characterized in that, The device includes a processor and a memory: The memory is used to store computer programs and send the instructions of the computer programs to the processor; The processor executes, according to the instructions of the computer program, a high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements a high-voltage cable arc fault risk assessment method based on a dynamic fire source and a cable pyrolysis combustion model as described in any one of claims 1-7.

Images