CN117951968A - Power equipment disaster influence assessment method and system based on environmental factor analysis - Google Patents
Power equipment disaster influence assessment method and system based on environmental factor analysis Download PDFInfo
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Abstract
The invention provides a disaster influence assessment method and system for power equipment based on environmental factor analysis, and belongs to the technical field of disaster influence assessment of power equipment; the technical problems to be solved are as follows: providing a disaster influence assessment method and system for power equipment based on environmental factor analysis; the technical scheme adopted for solving the technical problems is as follows: constructing a two-dimensional hydrodynamic model based on rainfall elements; by measuring the influence possibly suffered by the environmental humidity evaluation equipment, the tolerance capacity of the air insulation index evaluation equipment in a humid environment is adopted, and an air breakdown characteristic model is built based on humidity elements; establishing a three-dimensional model of the dry-type transformer, calculating an electromagnetic field, a temperature field and a fluid field of the three-dimensional model to obtain temperature field distribution of the dry-type transformer, and constructing a heat dissipation model; the method is applied to disaster influence assessment of the power equipment.
Description
Technical Field
The invention provides a disaster influence assessment method and system for power equipment based on environmental factor analysis, and belongs to the technical field of disaster influence assessment of power equipment.
Background
At present, with the continuous investment and construction of a new energy power system, wind power and photovoltaic power generation systems gradually become the main body of a power supply system in the future, but the adopted wind power, photovoltaic power generation modes and the like are greatly influenced by weather conditions, and if storm, long-time overcast and rainy weather and flood and waterlogging disasters all cause operation faults of the new energy power system, so that evaluation analysis of natural disaster factors and evaluation of disaster influence on power equipment become keys for normal operation of the new energy power system.
At present, a special monitoring and early warning platform is provided for monitoring natural weather disasters of a power grid, but the following defects and shortcomings still exist in the use process: the weather forecast data are mainly given by weather departments, and the forecast mainly aims at fixed town areas, lacks quantitative analysis forecast on the hazard influence degree of different areas and different power equipment (different power transmission lines, power transformation equipment and power distribution equipment), has weak pertinence and guidance of forecast information, and can lead to disaster early warning misuse of the position of the equipment and cause unnecessary power failure; in addition, the analysis dimension of the influence on the power equipment caused by the natural disasters is less at present, only preliminary weather risk assessment is involved, assessment judgment is not made on potential influence caused by the fact that the specific power equipment is wet and winded, and weather simulation and analysis deletion of specific parts of the power equipment can lead to low accuracy and poor objectivity of the assessment of the influence on the power equipment caused by the disasters.
Disclosure of Invention
The invention provides an improvement of a power equipment disaster influence assessment method and system based on environmental factor analysis, aiming at solving the technical problems of low accuracy and poor objectivity of equipment disaster influence assessment caused by weather simulation and analysis deficiency of specific parts of the power equipment, wherein the pertinence and the guidance of forecast information for the power equipment disaster influence assessment are weak, and the analysis dimension of influence assessment is small.
In order to solve the technical problems, the invention adopts the following technical scheme: an evaluation method for disaster impact of power equipment based on environmental factor analysis comprises the following impact evaluation steps:
step one: constructing a two-dimensional hydrodynamic model based on rainfall elements;
step two: evaluating the possible influence of the power equipment by measuring the ambient humidity, adopting the air insulation index to evaluate the tolerance of the equipment in the humid environment, and constructing an air breakdown characteristic model based on the humidity element;
Step three: establishing a three-dimensional model of the dry-type transformer, calculating an electromagnetic field, a temperature field and a fluid field of the three-dimensional model to obtain temperature field distribution of the dry-type transformer, and constructing a heat dissipation model;
based on a heat dissipation model of the dry-type transformer, performing fault simulation aiming at the position of the dry-type transformer, which is easy to have hot spots, under the current meteorological conditions, acquiring an equipment overheat index, and performing dynamic early warning on overheat risk of the transformer;
Step four: and comprehensively evaluating the disaster influence of the power equipment by combining a two-dimensional hydrodynamic model, an air breakdown characteristic model and a heat dissipation model of the dry-type transformer, and giving an evaluation report.
The specific method for constructing the two-dimensional hydrodynamic model in the first step comprises the following steps:
Step 1.1: collecting three-dimensional topographic data, hydrological data, basic data of a transformer substation and drainage data in an area, and generating a data file through software analysis and processing;
Step 1.2: importing the data file generated in the step 1.1 into MIKE software to generate a basic numerical model of a simulation area, performing grid division on the basic numerical model of the simulation area, performing grid smoothing, terrain elevation interpolation and manual check correction on the basic numerical model after grid division, and setting a water blocking boundary, a dry and wet dynamic boundary, bottom resistance parameters and a solving format in the basic numerical model to obtain a two-dimensional unsteady flow numerical model of the simulation area;
step 1.3: determining a solving format, and selecting a low-order precision format and a quick algorithm for analog calculation;
Step 1.4: determining parameters in the two-dimensional unsteady flow numerical model, and verifying and correcting the parameters of the obtained two-dimensional unsteady flow numerical model according to the actual submerged water depth data recorded by the flow and the history;
Step 1.5: according to the weather precipitation intensity level standard, traversing and carrying the weather precipitation intensity level standard into the established two-dimensional hydrodynamic model to obtain submerged water depth data of the transformer substation under different precipitation levels, obtaining a transformer substation ponding index by integrating transformer substation engineering data, obtaining a power distribution equipment waterlogging index by integrating power distribution equipment related parameters in the station, and completing model construction.
The specific method for analyzing and processing the acquired data to generate the data file in the step 1.1 is as follows:
converting the terrain, topography, land feature, water body and water conservancy condition parameters in the simulation area into a vector topography map containing the terrain, topography, land feature, water body and water conservancy condition information in the simulation area through CAD software;
And outputting the vector topography obtained above as a data file in the. Xyz format supported by MIKE software toolkit, and converting the data file in the. Xyz format into a. Mesh data file capable of running in MIKE software by MIKE software toolkit.
The specific method for modeling the two-dimensional unsteady flow value of the simulation area in the step 1.2 is as follows:
Step 1.2.1: importing the processed data file into MIKE software to form a basic numerical model of the simulation area, and carrying out grid division on the basic numerical model of the simulation area by utilizing MIKE software, wherein unstructured triangle forms are adopted during grid division;
step 1.2.2: carrying out grid smoothing, terrain elevation interpolation and manual checking correction on the basic numerical model subjected to grid division by utilizing MIKE software;
Step 1.2.3: setting a water blocking boundary in the simulation area;
Step 1.2.4: when land flood is simulated in MIKE software, starting dry-wet dynamic boundary setting for the area with the dry-wet side alternating area;
Step 1.2.5: and determining a bottom resistance parameter reflecting the ground water blocking condition by adopting Manning value expression.
The specific method for verifying the digital model and correcting the parameters in the step 1.4 is as follows:
Step 1.4.1: modifying the topography, landform and feature conditions in the established two-dimensional unsteady flow numerical model into topography, landform and feature conditions under historical conditions;
Step 1.4.2: inputting the inflow condition, the outflow condition and the duration recorded in the historical data into a modified two-dimensional unsteady flow numerical model to obtain a simulated submerged water depth under the recorded condition of the historical data;
Step 1.4.3: and comparing the simulated submerged water depth with the actual submerged water depth recorded by the historical data, controlling the error of the simulated submerged water depth and the actual submerged water depth recorded by the historical data, and if the simulated submerged water depth is not satisfied with the precision requirement compared with the actual submerged water depth recorded by the historical data, correcting the parameters in the two-dimensional unsteady flow numerical model and adjusting the parameters until the simulation result satisfies the precision requirement.
The specific method for constructing the air breakdown characteristic model in the second step comprises the following steps:
Step 2.1: calculating the relation between the air insulation strength and the absolute humidity, wherein the expression of the relation between the air insulation strength and the absolute humidity is as follows:
Ufr=Uf0(1+rk)；
wherein U f0 is the discharge voltage in the case of absolute humidity 0, i.e. complete drying, U fr is the discharge voltage of air when the absolute humidity is r, r is the absolute humidity of air, and k is a coefficient;
Satisfying r=11 g/m 3 under standard atmospheric conditions, the discharge voltage of air insulation at this time is U fN, and the calculation formula is:
UfN=Uf0(1+11k)；
The relation expression of the above formula, the air insulation strength and the absolute humidity is deduced to obtain:
；
where k is a constant, the above formula is simplified as:
；
Wherein K 1 is the humidity correction coefficient of the air insulation discharge voltage, and is found out according to the r value;
If the atmospheric condition is different from the standard atmospheric condition in the test, the air pressure is P, the air temperature is t, and the absolute humidity is r, the atmospheric condition after the test is corrected, and the calculation formula of the test voltage is as follows:
；
Wherein U S is a test voltage externally insulated under standard atmospheric conditions specified by a standard; delta t is the relative density of air in the state that the air temperature is t;
step 2.2: and solving ionization and adsorption coefficients by adopting a Boltzmann equation, wherein the calculation formula is as follows:
；
Wherein: v is the electron velocity; e is the electron charge amount; m e is electron mass; an operator that is a velocity gradient; f is a velocity distribution function; e is an electron charge; t is time; c is a collision term related to f;
The electron energy distribution function is obtained by solving the Boltzmann equation, and the ionization reaction coefficient and the adsorption reaction coefficient are respectively obtained by the electron energy distribution function, wherein the calculation formula is as follows:
；
wherein: alpha and eta are ionization and adsorption coefficients, electron energy epsilon= (v/gamma) 2, f (epsilon) is an electron energy distribution function, and sigma α(ε)、ση (epsilon) is an ionization section and an adsorption section;
Step 2.3: solving the critical electric field intensity:
The reaction coefficient is solved by utilizing the Boltzmann equation, the difference between the ionization reaction coefficient and the adsorption reaction coefficient is the net increase rate of electrons, namely the effective ionization rate alpha eff, and the calculation formula is as follows:
αeff=α-η；
when the effective ionization coefficient is equal to 0, the corresponding electric field intensity is the critical electric field intensity;
Step 2.4: solving a Boltzmann equation by utilizing a plasma module in Comsol software, and solving to obtain ionization reaction coefficients of dry air and wet air at different temperatures;
step 2.5: and selecting a test transformer, inputting temperature, humidity and air pressure values according to the air breakdown characteristic model and microclimate prediction data, and calculating the critical breakdown field intensity of air to be extracted as an air insulation index.
The specific method for constructing the heat dissipation model in the third step comprises the following steps:
Step 3.1: according to structural data of a dry type transformer, building a three-dimensional coordinate system with a geometric center of a solid part of the dry type transformer as an origin of coordinates, setting a fluid area according to forced air cooling heat dissipation conditions, adopting forced convection heat dissipation for the dry type transformer, setting an upper boundary of the model as a pressure outlet, setting surface pressure as 0, setting a lower boundary of the model as a speed inlet, and then converting wind speed and wind quantity, wherein a calculation formula is as follows:
Q=3600·F·v；
wherein: q is the air quantity, F is the ventilation area of the air port, and v is the measured average air speed of the air port;
Step 3.2: the upper part of the dry type transformer can change temperature under the influence of hot air, radiation is larger as the temperature is higher, at the moment, the temperature field distribution of the dry type transformer is modeled, and the accuracy of the model is analyzed and verified;
Step 3.3: under the condition of the same boundary condition, setting the inlet wind speed to be zero, namely performing simulation calculation on the temperature fluid coupling field under the condition of natural cooling;
Establishing a heat radiation model of the dry-type transformer through finite element analysis, performing simulation analysis on temperature fluid coupling fields under different inlet wind speeds to obtain the distribution condition of a temperature field of a dry-type transformer body and the distribution condition of a flow field in a box body of the dry-type transformer, finding out the position of the dry-type transformer which is easy to overheat, obtaining the influence degree of different temperatures and wind speeds on the heat radiation efficiency of the transformer, extracting an equipment overheat index, and performing dynamic early warning on the overheat risk of the transformer by combining weather forecast;
step 3.4: based on a microclimate monitoring model, accurate ambient temperature and wind speed are obtained, equipment operation parameters and an equipment heat dissipation model are comprehensively considered, internal and external temperatures of the dry-type transformer are calculated, anomalies of heat dissipation of the transformer under certain temperature and wind speed conditions are obtained through analysis, equipment overheat indexes are extracted based on the meteorological conditions, and dynamic early warning is carried out on overheat risks of the transformer.
The evaluation system used for realizing the power equipment disaster influence evaluation method based on environmental factor analysis comprises an acquisition computer for acquiring three-dimensional topographic data and hydrological data in an area, basic data of a transformer substation and drainage data, an analysis processing server for constructing an air breakdown characteristic model, and an early warning server for constructing a heat dissipation model and performing fault simulation for a dry-type transformer.
Compared with the prior art, the invention has the following beneficial effects: according to the method, the disaster influence of the power equipment is evaluated, the disaster influence is analyzed and judged mainly by constructing a two-dimensional hydrodynamic model, an air breakdown characteristic model and a dry-type transformer heat dissipation model by comprehensively considering corresponding environmental factors, a judging rule of weather disaster risk is formed, key indexes of the disaster risk of the power equipment are extracted, and an automation technology is combined, so that customized power weather service for different operation and maintenance requirements of a power grid is realized, and further, the accuracy and the intellectualization of weather disaster early warning of the power equipment are realized.
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a flow chart of the calculation of critical electric field strength according to the present invention;
FIG. 2 is a graph showing the effect of the present invention on the ionization reaction coefficient contrast of dry air and humid air;
FIG. 3 is a schematic diagram of a dry-type transformer according to the present invention;
FIG. 4 is a schematic diagram of the internal fluid velocity distribution of the dry-type transformer of the present invention;
FIG. 5 is a schematic diagram of the temperature distribution of the dry-type transformer according to the present invention;
FIG. 6 is a graph showing the effect of temperature distribution of windings in the axial direction in a forced heat dissipation mode according to the present invention;
FIG. 7 is a temperature cloud of the various parts of the transformer at an inlet wind speed of 0 in accordance with the present invention;
FIG. 8 is a temperature cloud of the various parts of the transformer at an inlet wind speed of 1m/s according to the invention.
Detailed Description
The invention provides a disaster influence assessment method for power equipment, which is mainly used for analyzing and assessing the comprehensive influence of temperature, humidity and wind speed in environmental factors on the power equipment and relates to the study of a key index system for meteorological disaster risk of the power equipment.
The invention firstly builds a two-dimensional hydrodynamic model by analyzing rainfall elements, and particularly predicts the changes of water flow, water level and the like by carrying out numerical simulation on hydrodynamic processes such as water flow and the like based on a two-dimensional hydrodynamic equation, and adopts the two-dimensional hydrodynamic model to be used for predicting the changes of environmental parameters such as water level, water flow speed, water flow direction and the like, and the method comprises the following specific steps:
Step 1.1: data preparation:
The topographic map data includes: three-dimensional terrain data in the region refers to standard ground object classification and Manning value;
Engineering building parameters: basic data and drainage data of a certain transformer substation;
Hydrologic data: measuring water level, flow rate, time measuring water level, flow rate and flow speed data along the flood of a certain time period, and measuring a water level and flow rate relation curve, (new and old) drainage curve of a certain transformer substation; when the data preprocessing is carried out: converting parameters such as topography, land feature, water body, water conservancy conditions and the like in the simulation area into a vector topography map containing information of topography, land feature, water body, water conservancy conditions in the simulation area through CAD software;
The vector topography obtained above is then output as a data file in the. Xyz format supported by the MIKE software package, and the data file in the. Xyz format is converted by the MIKE software package into a. Mesh data file that can be run in the MIKE software.
Step 1.2: model design:
Importing the data file generated in the steps into MIKE software to generate a basic numerical model of the simulation area, carrying out grid division on the basic numerical model of the simulation area, carrying out grid smoothing treatment, terrain elevation interpolation and manual check correction on the basic numerical model after grid division, setting a water blocking boundary, a dry and wet dynamic boundary, bottom resistance parameters and a solving format in the basic numerical model, and obtaining a two-dimensional unsteady flow numerical model of the simulation area.
In an embodiment of the present disclosure, a specific modeling method includes the following steps:
Step 1.2.1: dividing grids:
Opening MIKE software, and importing the processed data file into MIKE software to form a basic numerical model of the simulation area; performing grid division on a basic numerical model of the simulation area by MIKE software, wherein an unstructured triangle form is adopted during grid division; unstructured grids refer to grids in which the inner points in the grid area do not have the same adjacent units, namely the number of grids connected with different inner points in the grid splitting area is different, and for other forms of grids, the grid form of the unstructured triangle has higher precision and accuracy when calculating a model with complex boundaries encountered in the embodiment.
Step 1.2.2: grid processing:
Then carrying out grid smoothing, terrain elevation interpolation and manual checking correction on the basic numerical model after grid division by utilizing the function of MIKE software; in order to improve the design precision, grid partition encryption processing is carried out on the four preliminarily selected sites.
Step 1.2.3: setting a water blocking boundary:
The water-blocking boundary in the simulation area comprises railways, highways, buildings higher than the ground, river dikes and the like, the water-blocking boundary can play a role in blocking flood, special consideration needs to be taken into account in the model, and when the water level is higher than the roads and the dikes, the flood can overflow and cross the water-blocking boundary.
Step 1.2.4: setting a dry-wet dynamic boundary parameter:
when land flood is simulated in MIKE software, the problem of dry-wet edge alternation exists in most areas, and in order to avoid instability factors in the calculation process, dry-wet dynamic boundary setting needs to be started, and the dynamic boundary problem refers to the problem of determining the boundary line between the water-free area and the water-free area.
Step 1.2.5: determining a bottom resistance parameter:
The parameter is a comprehensive parameter reflecting the ground water blocking condition, and is comprehensively determined in a certain range according to the conditions of river channel conditions, crop compositions, village distribution, tree clusters, roads, cofferdam distribution and the like in a research area; in the embodiment, manning value expression is adopted, and in the first calculation, the Manning values of the forests and villages are considered according to 10, and the corresponding roughness is 0.1; the Manning values of rivers, farmlands and lands are considered as 20, and the corresponding roughness is 0.05.
Step 1.3: determining a solving format:
The simulation calculation can use a low-order (first-order precision) method or a high-order (second-order precision) method, the calculation of the low-order method is fast, the calculation result precision is poor, the calculation precision of the high-order method is high and the calculation speed is slow, and if convection is dominant in the simulation process, the high-order method is selected; if diffusion is dominant, the low-order method can meet the accuracy; in the embodiment, the analog calculation adopts a low-order precision format and a fast algorithm.
Step 1.4: model evaluation and correction:
the accuracy of parameters in a two-dimensional unsteady flow numerical model can directly influence the calculation of various hydraulic elements, and the parameters such as bottom resistance, vortex viscosity coefficient and the like are difficult to accurately determine at present and are required to be determined by a historical flood inverse solution method; when the parameters in the two-dimensional unsteady flow numerical model are determined, firstly, parameters such as bottom resistance, vortex viscosity coefficient and the like are assumed, and then, according to actual submerged water depth data recorded by flow and history, the two-dimensional unsteady flow numerical model is verified and parameter corrected, and the specific steps are as follows.
Step 1.4.1: modifying the topography, landform and feature conditions in the established two-dimensional unsteady flow numerical model into topography, landform and feature conditions under historical conditions;
Step 1.4.2: inputting the inflow condition, the outflow condition and the duration recorded in the historical data into a modified two-dimensional unsteady flow numerical model to obtain a simulated submerged water depth under the recorded condition of the historical data;
Step 1.4.3: comparing the simulated submerged depth with the actual submerged depth recorded in the historical data, wherein in the embodiment, the simulated submerged depth near the boundary area, the water inlet and the water outlet and the actual submerged depth error recorded in the historical data are controlled within 0.5m, and the simulated submerged depth in the internal area and the actual submerged depth error recorded in the historical data are controlled within 0.2 m; if the simulated submerged water depth is not satisfied with the precision requirement compared with the actual submerged water depth recorded by the historical data, the parameters in the two-dimensional unsteady flow numerical model are corrected, and the parameters to be adjusted have the maximum time step, the minimum time step, the dry and wet boundary parameters, the bottom resistance, the vortex viscosity coefficient and the like until the simulation result satisfies the precision requirement.
Finally simulating a historical flooding process through calculation and parameter correction; the data of calculated water level, flow velocity, flow direction, highest water level, submerged water depth and the like obtained by simulation calculation are basically consistent with the contents recorded in history, and the corrected parameter setting is considered to be reasonable through analysis and demonstration.
Step 1.5: aiming at the ponding index of the transformer substation, extracting the waterlogging index of the distribution equipment:
According to the weather precipitation intensity level standard, traversing and introducing the weather precipitation intensity level standard into the established two-dimensional hydrodynamic model to obtain the submerged water depth of the transformer substation under different precipitation levels, obtaining the transformer substation ponding index by integrating transformer substation engineering data, and obtaining the power distribution equipment waterlogging index by integrating the relevant parameters of the power distribution equipment in the station.
The invention needs to construct an air breakdown characteristic model aiming at humidity factors, the ambient humidity is an important factor for evaluating the damage of the electric equipment in a humid environment, and in the environment with high humidity, the electric equipment is easy to be affected by damp, electric leakage and the like, so that the influence possibly suffered by the equipment can be evaluated by measuring the ambient humidity, the air insulation index is an important parameter for measuring the insulation condition of the electric equipment, and the air breakdown characteristic model is generally used for evaluating the tolerance of the equipment in the humid environment, and comprises the following specific steps of:
step 2.1: calculating the relation between the air insulation strength and the absolute humidity:
The insulation strength of the air gap is related to the ambient atmospheric conditions, namely, the air pressure, the air temperature and the absolute humidity of the ambient air, and the relation between the air insulation strength and the absolute humidity is expressed as follows:
Ufr=Uf0(1+rk)；
Wherein: u f0 is the discharge voltage with absolute humidity of 0, i.e. in the case of complete drying;
U fr is the discharge voltage of air when the absolute humidity is r;
r is the absolute humidity (units) of air;
k is a coefficient;
At standard atmospheric conditions, r=11 g/m 3, where the air-insulated discharge voltage is U fN, there are:
UfN=Uf0(1+11k)；
The further derivations are:
；
The k-factor can be considered constant over a range, and the above equation can be reduced to:
；
Wherein K 1 is the humidity correction coefficient of the air insulation discharge voltage, which can be found out according to the value of r.
Therefore, if the atmospheric conditions at the time of the test are different from the standard atmospheric conditions, the air pressure is P, the air temperature is t, and the absolute humidity is r, the test voltage after correction according to the atmospheric conditions at the time of the test should be:
；
Wherein U S is a standard specified test voltage for external insulation under standard atmospheric conditions; delta t is the relative density of air at temperature t.
An important index for measuring the electrical breakdown characteristics of a gas is the critical electric field strength, which refers to the electric field strength corresponding to the time when the electron collapse in the gas is in a critical state of continuing to develop and gradually disappear; when the external electric field intensity is higher than the critical electric field intensity, the electron collapse can be rapidly developed, and the gas is possibly broken down, so that the maximum field intensity which can be born by the gas gap is lower than the critical electric field intensity in practical insulation design.
According to the method, the Boltzmann analysis method is adopted to solve the electric breakdown characteristic of the moist air, so that the influence of humidity on the electric breakdown characteristic of the air is analyzed; under normal atmospheric conditions, the maximum partial pressure ratio of water vapor does not exceed 8%. In the calculation analysis of the present invention, the moisture content of the humid air was set to 8%.
Step 2.2: solving ionization and adsorption coefficients:
Firstly, solving ionization and adsorption coefficients by adopting a method for solving a Boltzmann equation, wherein a calculation formula is as follows:
；
Wherein: v is the electron velocity; e is the electron charge amount; m e is electron mass; an operator that is a velocity gradient; f is a velocity distribution function; e is an electron charge; t is time; c is a collision term related to f.
The Boltzmann equation is solved to obtain an Electron Energy Distribution Function (EEDF), and the ionization reaction coefficient and the adsorption reaction coefficient can be respectively obtained by EEDF, wherein the calculation formula is as follows:
；
Wherein: alpha and eta are ionization and adsorption coefficients;
Electron energy: epsilon= (v/gamma) 2;
f (epsilon) is an electron energy distribution function;
σ α(ε)、ση (ε) is the ionization cross-section and adsorption cross-section;
The boltzmann equation was solved using a plasma module in COMSOL4.3 software. Due to the limited source of data, the following assumptions are used: first, the effect of the excited states of all particles is ignored; second, after ionization occurs, the secondary electrons and the newly generated electrons have the same energy; third, since the ion concentration is relatively low and the ionization degree is small, the three-body collision and coulomb interaction are not considered.
Step 2.3: solving the critical electric field intensity:
Since the ionization reaction increases the number of electrons exponentially and the adsorption reaction decreases the number of electrons exponentially, the difference between the ionization reaction coefficient and the adsorption reaction coefficient is the net increase rate of electrons, i.e., the calculation formula of the effective ionization rate α eff is:
αeff=α-η；
when the effective ionization coefficient is equal to 0, the corresponding electric field intensity is the critical electric field intensity.
The calculation flow for obtaining the critical electric field intensity by solving the reaction coefficient by using the boltzmann equation is shown in fig. 1.
Step 2.4: calculation results and analysis:
According to the invention, the Boltzmann equation is solved by using Comsol, and the ionization reaction coefficient relation between dry air and moist air (8% water-92% air) at different temperatures is obtained by solving as shown in figure 2, and based on the figure, it can be known that:
as the electric field strength increases, the ionization coefficient of the gas also gradually increases; the greater the electric field strength, the faster the ionization coefficient increases. Humidity can also have a large influence on the ionization coefficient of air; the ionization coefficient of the wet air is larger than that of the dry air at the same temperature, and the critical breakdown field strength of the wet air is higher than that of the dry air at the same temperature.
Step 2.5: obtaining an air insulation index:
The moisture in the air is attached to the surface of the insulating material, so that the insulation resistance of the electrical equipment is reduced, and particularly, the equipment with longer service life is lower, and the moisture is adsorbed by dust accumulation in the equipment, so that the moisture degree is more serious, and the insulation resistance is lower; therefore, a test transformer is selected, according to an air breakdown characteristic model, according to microclimate prediction data, a temperature value, a humidity value and an air pressure value are input, and the critical breakdown field intensity of air is calculated and is extracted as an air insulation index.
Then, the invention also needs to construct a heat dissipation model of the distribution equipment based on temperature and wind speed factors, the service life of the dry type transformer often depends on the service life of the insulating layer, and the factor affecting the insulating material most is the temperature, once the temperature exceeds the heat resistance value, the insulating layer can be damaged, and the transformer can not work normally. Transformer overheating faults are one of the most common faults that pose a serious threat to the safe operation and life of the transformer. The fault reasons of various dry transformers are comprehensively analyzed, and a great part of fault reasons are insulation failures caused by local overheating of the dry transformers. In a period of time before and after the occurrence of a fault, the temperature field generates different changes along with the occurrence of the fault, in order to solve the changes of the temperature field, a three-dimensional model of the dry-type transformer is established by utilizing finite element analysis, the electromagnetic field, the temperature field and the fluid field of the model are calculated to obtain the temperature field distribution of the dry-type transformer, and finally the position where the dry-type transformer is easy to have hot spots is required to be analyzed through the temperature field of the dry-type transformer, the fault simulation is carried out on the position, and the equipment overheat index is acquired, wherein the method comprises the following specific steps:
Step 3.1: modeling of the dry type transformer and simulation calculation of the fluid field:
in the embodiment of the present disclosure, 1 dry-type transformer of 10KV is selected as a study object, a model is constructed according to structural data of the dry-type transformer, a three-dimensional coordinate system with a geometric center of a solid portion of the dry-type transformer as an origin of coordinates is established, a fluid region is set according to actual conditions during forced air cooling heat dissipation, namely, a lower half portion of the fluid region is required to follow the height of a lower end face of a winding and an iron core from the ground and the position of a side-blowing type heat dissipation fan, an upper half portion of the fluid region is required to have a proper height, and an upper surface of the fluid region can be set as an outlet to simulate infinite boundary conditions in actual conditions when the fluid boundary is set.
The solid part is exemplified by a dry type transformer with the model of SCB10-400 kV.A/10 kV and the insulation grade of F, the parameters are shown in the following table, and the structure is shown in figure 3:
In order to obtain the temperature field distribution characteristics of the dry-type transformer which can meet the actual requirements of engineering and not consume too much calculation cost, the following assumptions are also made when building a three-dimensional model of the dry-type transformer: the main structure of the model is iron core, three-phase winding, insulating cylinder, heat dissipation air passage and air domain, which retains the insulation of winding end, the insulation between the sections of high-voltage winding and the encapsulation insulation, and omits the structures of inter-turn insulation, clamping piece, air passage stay, etc.
The dry-type transformer adopts forced convection heat dissipation, the upper boundary of a model is set as a pressure outlet, the surface pressure is set as 0, the lower boundary is set as a speed inlet, and a conversion formula of wind speed and wind quantity is as follows:
Q=3600·F·v；
Wherein: q is the air volume (unit: m 3/h) F is the tuyere ventilation area (unit: m 2), and v is the measured average tuyere wind speed (unit: m/s). The air volume of the heat radiation fan is larger than 750m 3/h, the air speed is larger than 2.66m/s, and the speed is set to be 3m/s in consideration of actual efficiency.
As shown in fig. 4, which is a front view and a side view of the air domain fluid velocity distribution of the dry-type transformer, the cooling fan blows air upwards from the lower surfaces of the two sides of the transformer core at an angle of 45 degrees with respect to the horizontal direction, and the air flow rates at different axial positions and radial positions of the transformer are different. The air flow rate on the outer surface of the high-voltage winding is larger, the convection heat dissipation capacity of the surface of the high-voltage winding is enhanced, but the internal heat dissipation air passage is narrower, the air flow rate is smaller, particularly, the air flow passage on the upper part of the iron core window is blocked by the iron yoke, the air flow rate is rapidly reduced, the convection heat dissipation capacity of the surface of the low-voltage winding is weakened, and meanwhile, the radiation heat transfer capacity between the high-voltage winding and the low-voltage winding is enhanced due to the increase of the temperature difference between the high-voltage winding and the low-voltage winding.
Step 3.2: for dry transformer temperature field distribution and analysis:
Fig. 5 shows a temperature distribution diagram of the dry-type transformer in a rated operating state in a forced heat dissipation mode; when the hot air rises, the mass volume can be increased, the upstream air of the dry type transformer can be increased continuously, and when the air near the top flow is close to the top flow, the air around the transformer can collide with the air in the air passage, and the main factor is that when the heating of the air is increased continuously, the volume can be increased continuously, and the air moves along the air passage and the surface of the transformer. During the flow of the air, the change of the air passage is affected due to the viscosity problem in the air, thereby affecting the flow rate. The faster the flow rate will act when closer to the ground, and vice versa; when the contact surface stagnates with the air flow, the formed thermal film will influence the internal movement of the air flow after the contact resistance. The heat exchange resistance reduces the heat exchange coefficient under the influence of the thickness of the thermal thin layer, the temperature can be continuously increased, the viscosity coefficient in the air can be continuously increased, and the flow rate is reduced; the upper part of the dry-type transformer changes the temperature under the influence of hot air, the higher the temperature is, the greater the radiation is,
As shown in FIG. 6, the hottest spot temperatures of the high voltage winding and the low voltage winding were 91.64℃and 97.32 ℃respectively, and the position coordinates thereof were (15.40, -2.70, 17.75) and (8.70, -0.61, 25.00) (unit: cm) respectively. Compared with the factory temperature rise test data 88 ℃ and 107 ℃ of the high-voltage winding and the low-voltage winding of the transformer, the hot spot temperature of the low-voltage winding is slightly smaller than that of the test data, because structural members such as an air passage stay, a clamping piece and the like and errors of forced convection heat dissipation wind speed have a certain influence on heat dissipation capacity, the hot spot temperature of the high-voltage winding is basically consistent with the test data, and the accuracy of the finite element model is verified.
Temperature field distribution and analysis under different wind speed conditions for a dry-type transformer:
under the condition of the same boundary condition, the inlet wind speed is set to be 0, namely, the temperature-fluid coupling field under the natural cooling condition is subjected to simulation calculation, and the temperature distribution of each part of the transformer is shown in fig. 7:
According to the calculation result, when the dry-type transformer is cooled by natural air, because the heat dissipation effect of the inner-layer low-voltage coil is poor, a hot spot is positioned at the upper-section low-voltage winding, the temperature of the hot spot is 166.821 ℃, and the temperature rise is 121.821 ℃; the highest temperature of the iron core is positioned at the upper section of the iron core, the temperature is 117.828 ℃, and the temperature rise is 72.828 ℃; the highest temperature value of the low-voltage winding at the lower section is positioned at the upper end of the middle winding, the temperature value is 107.827 ℃, the highest temperature value of the high-voltage winding is 142.935 ℃, and the highest temperature value is positioned at the uppermost end of the high-voltage winding.
As shown in fig. 8, as shown in the calculation result, the ventilation effect of the inner low-voltage coil is improved when the inlet wind speed is 1m/s, but because the end insulation at the upper end of the high-voltage winding blocks the ventilation at the uppermost end of the winding, a hot spot is positioned at the upper end winding of the high-voltage winding, the hot spot temperature is 140.866 ℃, and the temperature rise is 95.866 ℃; the highest temperature of the iron core is positioned at the upper section of the iron core, the temperature is 90.061 ℃, and the temperature rise is 45.061 ℃; the maximum temperature of the lower low-voltage winding is positioned at the upper end of the winding, the temperature value is 82.031 ℃, the maximum temperature of the upper low-voltage winding is positioned at the upper end of a winding wire, and the temperature value is 116.459 ℃.
Step 3.3: based on the embodiment data, the invention establishes the heat dissipation simulation of the dry type transformer through finite element analysis, models one dry type transformer, and carries out temperature-fluid coupling field simulation analysis under different inlet wind speeds to obtain the distribution condition of the temperature field of the dry type transformer body and the distribution condition of the flow field in the box body of the dry type transformer, finds out the position where the dry type transformer is easy to overheat, obtains the influence degree of different temperatures and wind speeds on the heat dissipation efficiency of the transformer, extracts the overheat index of equipment, combines weather forecast, and carries out dynamic early warning on the overheat risk of the transformer. When naturally cooling (when the inlet wind speed is 0), the whole hot spot of the transformer appears at the upper end of the low-voltage winding, and the maximum temperature rise is 166.821 ℃. When the inlet wind speed is 1m/s, the integral hot spot of the transformer appears at the upper end of the high-voltage winding near the end insulation, and the maximum temperature rise is 140.866 ℃. When the inlet wind speed is 3m/s, the integral hot spot of the transformer appears at the upper end of the low-voltage winding near the end insulation, and the maximum temperature rise is 97.32 ℃.
Step 3.4: extraction equipment overheat index:
The embodiment still selects a typical dry-type transformer for analysis, obtains accurate ambient temperature and wind speed based on a microclimate monitoring model according to meteorological monitoring data, comprehensively considers equipment operation parameters and an equipment heat dissipation model, calculates the internal and external temperatures of the transformer, analyzes to obtain abnormal heat dissipation of the transformer under certain temperature and wind speed conditions, extracts the meteorological conditions as an equipment overheat index, and dynamically early warns the overheat risk of the transformer.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (8)
1. An evaluation method for disaster influence of power equipment based on environmental factor analysis is characterized by comprising the following steps: the method comprises the following influence evaluation steps:
step one: constructing a two-dimensional hydrodynamic model based on rainfall elements;
step two: evaluating the possible influence of the power equipment by measuring the ambient humidity, adopting the air insulation index to evaluate the tolerance of the equipment in the humid environment, and constructing an air breakdown characteristic model based on the humidity element;
Step three: establishing a three-dimensional model of the dry-type transformer, calculating an electromagnetic field, a temperature field and a fluid field of the three-dimensional model to obtain temperature field distribution of the dry-type transformer, and constructing a heat dissipation model;
based on a heat dissipation model of the dry-type transformer, performing fault simulation aiming at the position of the dry-type transformer, which is easy to have hot spots, under the current meteorological conditions, acquiring an equipment overheat index, and performing dynamic early warning on overheat risk of the transformer;
Step four: and comprehensively evaluating the disaster influence of the power equipment by combining a two-dimensional hydrodynamic model, an air breakdown characteristic model and a heat dissipation model of the dry-type transformer, and giving an evaluation report.
2. The method for evaluating disaster impact of power equipment based on environmental factor analysis according to claim 1, wherein the method comprises the steps of: the specific method for constructing the two-dimensional hydrodynamic model in the first step comprises the following steps:
Step 1.1: collecting three-dimensional topographic data, hydrological data, basic data of a transformer substation and drainage data in an area, and generating a data file through software analysis and processing;
Step 1.2: importing the data file generated in the step 1.1 into MIKE software to generate a basic numerical model of a simulation area, performing grid division on the basic numerical model of the simulation area, performing grid smoothing, terrain elevation interpolation and manual check correction on the basic numerical model after grid division, and setting a water blocking boundary, a dry and wet dynamic boundary, bottom resistance parameters and a solving format in the basic numerical model to obtain a two-dimensional unsteady flow numerical model of the simulation area;
step 1.3: determining a solving format, and selecting a low-order precision format and a quick algorithm for analog calculation;
Step 1.4: determining parameters in the two-dimensional unsteady flow numerical model, and verifying and correcting the parameters of the obtained two-dimensional unsteady flow numerical model according to the actual submerged water depth data recorded by the flow and the history;
Step 1.5: according to the weather precipitation intensity level standard, traversing and carrying the weather precipitation intensity level standard into the established two-dimensional hydrodynamic model to obtain submerged water depth data of the transformer substation under different precipitation levels, obtaining a transformer substation ponding index by integrating transformer substation engineering data, obtaining a power distribution equipment waterlogging index by integrating power distribution equipment related parameters in the station, and completing model construction.
3. The method for evaluating disaster impact of electric power equipment based on environmental factor analysis according to claim 2, wherein: the specific method for analyzing and processing the acquired data to generate the data file in the step 1.1 is as follows:
converting the terrain, topography, land feature, water body and water conservancy condition parameters in the simulation area into a vector topography map containing the terrain, topography, land feature, water body and water conservancy condition information in the simulation area through CAD software;
And outputting the vector topography obtained above as a data file in the. Xyz format supported by MIKE software toolkit, and converting the data file in the. Xyz format into a. Mesh data file capable of running in MIKE software by MIKE software toolkit.
4. A method for evaluating disaster impact of electrical equipment based on environmental factor analysis according to claim 3, wherein: the specific method for modeling the two-dimensional unsteady flow value of the simulation area in the step 1.2 is as follows:
Step 1.2.1: importing the processed data file into MIKE software to form a basic numerical model of the simulation area, and carrying out grid division on the basic numerical model of the simulation area by utilizing MIKE software, wherein unstructured triangle forms are adopted during grid division;
step 1.2.2: carrying out grid smoothing, terrain elevation interpolation and manual checking correction on the basic numerical model subjected to grid division by utilizing MIKE software;
Step 1.2.3: setting a water blocking boundary in the simulation area;
Step 1.2.4: when land flood is simulated in MIKE software, starting dry-wet dynamic boundary setting for the area with the dry-wet side alternating area;
Step 1.2.5: and determining a bottom resistance parameter reflecting the ground water blocking condition by adopting Manning value expression.
5. The method for evaluating disaster impact of electric power equipment based on environmental factor analysis according to claim 4, wherein: the specific method for verifying the digital model and correcting the parameters in the step 1.4 is as follows:
Step 1.4.1: modifying the topography, landform and feature conditions in the established two-dimensional unsteady flow numerical model into topography, landform and feature conditions under historical conditions;
Step 1.4.2: inputting the inflow condition, the outflow condition and the duration recorded in the historical data into a modified two-dimensional unsteady flow numerical model to obtain a simulated submerged water depth under the recorded condition of the historical data;
Step 1.4.3: and comparing the simulated submerged water depth with the actual submerged water depth recorded by the historical data, controlling the error of the simulated submerged water depth and the actual submerged water depth recorded by the historical data, and if the simulated submerged water depth is not satisfied with the precision requirement compared with the actual submerged water depth recorded by the historical data, correcting the parameters in the two-dimensional unsteady flow numerical model and adjusting the parameters until the simulation result satisfies the precision requirement.
6. The method for evaluating disaster impact of electric power equipment based on environmental factor analysis according to claim 5, wherein: the specific method for constructing the air breakdown characteristic model in the second step comprises the following steps:
Step 2.1: calculating the relation between the air insulation strength and the absolute humidity, wherein the expression of the relation between the air insulation strength and the absolute humidity is as follows:
Ufr=Uf0(1+rk)；
wherein U f0 is the discharge voltage in the case of absolute humidity 0, i.e. complete drying, U fr is the discharge voltage of air when the absolute humidity is r, r is the absolute humidity of air, and k is a coefficient;
Satisfying r=11 g/m 3 under standard atmospheric conditions, the discharge voltage of air insulation at this time is U fN, and the calculation formula is:
UfN=Uf0(1+11k)；
The relation expression of the above formula, the air insulation strength and the absolute humidity is deduced to obtain:
；
where k is a constant, the above formula is simplified as:
；
Wherein K 1 is the humidity correction coefficient of the air insulation discharge voltage, and is found out according to the r value;
If the atmospheric condition is different from the standard atmospheric condition in the test, the air pressure is P, the air temperature is t, and the absolute humidity is r, the atmospheric condition after the test is corrected, and the calculation formula of the test voltage is as follows:
；
Wherein U S is a test voltage externally insulated under standard atmospheric conditions specified by a standard; delta t is the relative density of air in the state that the air temperature is t;
step 2.2: and solving ionization and adsorption coefficients by adopting a Boltzmann equation, wherein the calculation formula is as follows:
；
Wherein: v is the electron velocity; e is the electron charge amount; m e is electron mass; an operator that is a velocity gradient; f is a velocity distribution function; e is an electron charge; t is time; c is a collision term related to f;
The electron energy distribution function is obtained by solving the Boltzmann equation, and the ionization reaction coefficient and the adsorption reaction coefficient are respectively obtained by the electron energy distribution function, wherein the calculation formula is as follows:
；
wherein: alpha and eta are ionization and adsorption coefficients, electron energy epsilon= (v/gamma) 2, f (epsilon) is an electron energy distribution function, and sigma α(ε)、ση (epsilon) is an ionization section and an adsorption section;
Step 2.3: solving the critical electric field intensity:
The reaction coefficient is solved by utilizing the Boltzmann equation, the difference between the ionization reaction coefficient and the adsorption reaction coefficient is the net increase rate of electrons, namely the effective ionization rate alpha eff, and the calculation formula is as follows:
αeff=α-η；
when the effective ionization coefficient is equal to 0, the corresponding electric field intensity is the critical electric field intensity;
Step 2.4: solving a Boltzmann equation by utilizing a plasma module in Comsol software, and solving to obtain ionization reaction coefficients of dry air and wet air at different temperatures;
step 2.5: and selecting a test transformer, inputting temperature, humidity and air pressure values according to the air breakdown characteristic model and microclimate prediction data, and calculating the critical breakdown field intensity of air to be extracted as an air insulation index.
7. The method for evaluating disaster impact of electric power equipment based on environmental factor analysis according to claim 6, wherein: the specific method for constructing the heat dissipation model in the third step comprises the following steps:
Step 3.1: according to structural data of a dry type transformer, building a three-dimensional coordinate system with a geometric center of a solid part of the dry type transformer as an origin of coordinates, setting a fluid area according to forced air cooling heat dissipation conditions, adopting forced convection heat dissipation for the dry type transformer, setting an upper boundary of the model as a pressure outlet, setting surface pressure as 0, setting a lower boundary of the model as a speed inlet, and then converting wind speed and wind quantity, wherein a calculation formula is as follows:
Q=3600·F·v；
wherein: q is the air quantity, F is the ventilation area of the air port, and v is the measured average air speed of the air port;
Step 3.2: the upper part of the dry type transformer can change temperature under the influence of hot air, radiation is larger as the temperature is higher, at the moment, the temperature field distribution of the dry type transformer is modeled, and the accuracy of the model is analyzed and verified;
Step 3.3: under the condition of the same boundary condition, setting the inlet wind speed to be zero, namely performing simulation calculation on the temperature fluid coupling field under the condition of natural cooling;
Establishing a heat radiation model of the dry-type transformer through finite element analysis, performing simulation analysis on temperature fluid coupling fields under different inlet wind speeds to obtain the distribution condition of a temperature field of a dry-type transformer body and the distribution condition of a flow field in a box body of the dry-type transformer, finding out the position of the dry-type transformer which is easy to overheat, obtaining the influence degree of different temperatures and wind speeds on the heat radiation efficiency of the transformer, extracting an equipment overheat index, and performing dynamic early warning on the overheat risk of the transformer by combining weather forecast;
step 3.4: based on a microclimate monitoring model, accurate ambient temperature and wind speed are obtained, equipment operation parameters and an equipment heat dissipation model are comprehensively considered, internal and external temperatures of the dry-type transformer are calculated, anomalies of heat dissipation of the transformer under certain temperature and wind speed conditions are obtained through analysis, equipment overheat indexes are extracted based on the meteorological conditions, and dynamic early warning is carried out on overheat risks of the transformer.
8. An evaluation system for implementing the environmental factor analysis-based power equipment disaster impact evaluation method according to claim 1, characterized in that: the system comprises an acquisition computer for acquiring three-dimensional topographic data and hydrological data in an area, basic data of a transformer substation and drainage data, an analysis processing server for constructing an air breakdown characteristic model, and an early warning server for constructing a heat dissipation model and performing fault simulation for a dry transformer.
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