AC flashover voltage prediction method and terminal

Abstract

The invention provides an alternating current flashover voltage prediction method and a terminal, and the method comprises the steps: calculating an initial value of each circuit parameter according to a simulation parameter and an equivalent circuit, and recalculating a new leakage current under the initial value of the circuit parameter through employing an obtained result; the development of the local electric arc is distinguished by utilizing the electric arc development criterion; if the electric arc development criterion is met, the electric arc development speed is calculated, the electric arc length is updated, the circuit parameters and the leakage current value are updated, and then the alternating-current electric arc reignition condition is judged; and the steps are continuously and circularly repeated until the arc penetrating condition is met, and the corresponding first voltage is the predicted value of the flashover voltage. The method can consider the influence of the environment temperature, the water band resistance and other factors on each parameter in the dynamic development process of the alternating-current arc, and can predict the alternating-current flashover voltage in the wet and dirty scene more simply, efficiently and accurately.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of insulation aging, in particular to an alternating current flashover voltage prediction method and terminal. BACKGROUND

[0002] The partial discharge problem induced by special operating environments such as high humidity, high salt fog, heavy contamination, and easy condensation brings great challenges to the operation reliability of electrical equipment. In the humid and hot climate environment, some local areas also have large diurnal temperature difference and serious pollution. In particular, in the coastal application environment, the gas-solid interface of the insulation part of high-voltage equipment is a relatively weak link, and the partial discharge caused by condensation and contamination is the main form of insulation breakdown of electrical equipment under wet and contaminated conditions. However, the existing research on the mechanism of partial discharge of wet and contaminated insulation materials is not perfect, and the accuracy of the discharge prediction model is insufficient, which makes it difficult to effectively guide the insulation coordination.

[0003] At present, due to the complexity of the development of the wet and contaminated insulation surface flashover process, it is difficult to construct a pollution flashover model that fully considers the actual situation. Although some achievements have been made in the related research on the insulation surface flashover model under wet and contaminated conditions at home and abroad in recent years, the existing model is too simplified. In addition, the existing model pays more attention to the influence of discrete water droplets on the flashover process, and does not fully consider the coexistence of dry band, local arc, water droplets and wet and contaminated layer in the actual discharge development process. Overall, the partial discharge model of the insulation part of electrical equipment under wet and contaminated conditions is still in the experimental exploration stage, and there is still a lack of complete theoretical support and effective models suitable for engineering practice. SUMMARY

[0004] The technical problem to be solved by the present application is to provide an alternating current flashover voltage prediction method and terminal, which can simply, efficiently and accurately predict the flashover voltage.

[0005] An alternating current flashover voltage prediction method, the method comprising: calculating circuit parameters of an equivalent circuit corresponding to a to-be-tested insulation surface according to a first arc length, a first leakage current and a first voltage of a previous moment of a current moment; calculating a current leakage current of the current moment according to the first voltage and the circuit parameters; judging whether an arc development criterion is met according to the current leakage current and the first leakage current, if yes, updating the first arc length to obtain a first current arc length of the current moment, and judging whether an arc reignition condition is met; if the arc development criterion is not met, increasing the first voltage, and returning to execute the step of calculating the circuit parameters of the equivalent circuit corresponding to the to-be-tested insulation surface with the increased first voltage; If the arc reignition condition is met, it is judged whether the current arc length is greater than the creepage distance of the insulation surface to be tested, and if yes, the first voltage is output as the flashover voltage; If the current arc length is less than the creepage distance, the arc length at the current time is returned to execute the step of calculating the circuit parameter of the equivalent circuit corresponding to the insulation surface to be tested.

[0006] To solve the above technical problems, another technical solution adopted by the present application is: A terminal comprises a memory, a processor and a computer program stored on the memory and running on the processor, and the processor implements the following steps when executing the computer program: According to the first arc length, the first leakage current and the first voltage at the previous time of the current time, the circuit parameter of the equivalent circuit corresponding to the insulation surface to be tested is calculated; According to the first voltage and the circuit parameter, the current leakage current at the current time is calculated; According to the current leakage current and the first leakage current, it is judged whether the arc development criterion is met, and if yes, the first arc length is updated to obtain the first current arc length at the current time, and it is judged whether the arc reignition condition is met; If the arc development criterion is not met, the first voltage is increased, and the step of calculating the circuit parameter of the equivalent circuit corresponding to the insulation surface to be tested is executed again with the increased first voltage; If the arc reignition condition is met, it is judged whether the current arc length is greater than the creepage distance of the insulation surface to be tested, and if yes, the first voltage is output as the flashover voltage; If the current arc length is less than the creepage distance, the arc length at the current time is returned to execute the step of calculating the circuit parameter of the equivalent circuit corresponding to the insulation surface to be tested.

[0007] The present application has the beneficial effects that the arc length, the leakage current and the voltage are used to calculate the circuit parameter of the equivalent circuit, the leakage current is updated according to the circuit parameter, it is judged whether the arc development criterion and the arc reignition condition are met, the arc length is updated according to the judgment result to simulate the arc development process, and finally it is judged whether the arc length is greater than the creepage distance to obtain the voltage at the insulation breakdown, i.e. the flashover voltage, which can consider the influence of various parameters in the dynamic development process of the alternating current arc, and can more simply, efficiently and accurately predict the alternating current flashover voltage. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 A step flow chart of an alternating current flashover voltage prediction method provided for the embodiment of the present application; Figure 2An application scene schematic diagram of an AC flashover voltage prediction method provided by the embodiment of the present application is provided. Figure 3 An equivalent circuit schematic diagram provided by the embodiment of the present application is provided. Figure 4 Another flow schematic diagram of an AC flashover voltage prediction method provided by the embodiment of the present application is provided. Figure 5 An actual application effect schematic diagram of an AC flashover voltage prediction method of the embodiment of the present application is provided. Figure 6 A structure schematic diagram of an AC flashover voltage prediction terminal provided by the embodiment of the present application is provided. Label description: 1. An AC flashover voltage prediction terminal; 2. A processor; 3. A memory. DETAILED DESCRIPTION

[0009] In order to explain the technical content, the achieved purposes and effects of the present application in detail, the following will be explained in combination with the embodiments and the accompanying drawings.

[0010] Please refer to Figure 1 An AC flashover voltage prediction method, characterized in that the method comprises: According to the first arc length, the first leakage current and the first voltage of the previous moment of the current moment, the circuit parameters of the equivalent circuit corresponding to the tested insulation surface are calculated; According to the first voltage and the circuit parameters, the current leakage current of the current moment is calculated; According to the current leakage current and the first leakage current, it is judged whether the arc development criterion is met, if yes, the first arc length is updated to obtain the first current arc length of the current moment, and it is judged whether the arc reignition condition is met; If the arc development criterion is not met, the first voltage is increased, and the first voltage after the increase is returned to execute the step of calculating the circuit parameters of the equivalent circuit corresponding to the tested insulation surface; If the arc reignition condition is met, it is judged whether the current arc length is greater than the creepage distance of the tested insulation surface, if yes, the first voltage is output as the flashover voltage; If the current arc length is less than the creepage distance, the arc length of the current moment is returned to execute the step of calculating the circuit parameters of the equivalent circuit corresponding to the tested insulation surface.

[0011] From the above description, the beneficial effects of the present application are that: the circuit parameters corresponding to the equivalent circuit are calculated by the arc length, the leakage current and the voltage, and then the leakage current is updated by the circuit parameters, whether the arc development criterion and the arc reignition condition are satisfied is judged, the arc length is updated according to the judgment result to simulate the arc development process, and finally whether the arc length is greater than the creepage distance is judged to obtain the voltage at the time of insulation breakdown, that is, the flashover voltage, which can consider the influence of each parameter in the dynamic development process of the alternating current arc, and can more simply, efficiently and accurately predict the alternating current flashover voltage.

[0012] Further, it further comprises: obtaining the creepage distance corresponding to the to-be-tested insulation surface and the unit voltage of the to-be-tested insulation surface; initializing the initial voltage and the initial arc length at the initial time; calculating the initial leakage current as the leakage current at the 0th moment according to the creepage distance, the initial voltage and the initial arc length.

[0013] From the above description, when the parameters in the equivalent circuit at the initial time are unknown, the leakage current is calculated through the initial voltage and the initial arc length, and then the parameters in the equivalent circuit are determined according to the leakage current, and the leakage current is recalculated after the parameters in the equivalent circuit are updated, so as to realize the iterative update of the leakage current and simulate the development process of the arc.

[0014] Further, the circuit parameters include arc resistance, residual wet pollution layer resistance, residual wet pollution layer capacitance and water belt resistance.

[0015] From the above description, the calculation of the arc resistance, the residual wet pollution layer resistance, the residual wet pollution layer capacitance and the water belt resistance includes the most important factors affecting the development of the arc, so as to improve the accuracy of the arc development simulation.

[0016] Further, the calculation of the arc resistance, the residual wet pollution layer resistance, the residual wet pollution layer capacitance and the water belt resistance includes the most important factors affecting the development of the arc, so as to improve the accuracy of the arc development simulation. calculating the arc resistance ; In the formula, p arc is the resistivity of the local arc path, r arc is the equivalent radius of the arc head, s arc is the cross-sectional area of the local arc; x is the first arc length; calculating the residual wet pollution layer resistance ; calculating the residual wet pollution layer capacitance ; In the formula,r rest is the linear resistance of the residual wet pollution layer; S is a constant, a is the electrode width, i is the first leakage current; p rest is the resistivity of the residual wet pollution layer; c rest is the linear capacitance of the residual wet pollution layer; e rest is the relative dielectric constant of the residual wet pollution layer; s rest is the cross-sectional area of the residual wet pollution layer on the surface of the silicone rubber; L is the creepage distance; calculating the resistance of the water hose ; In the formula, p s is the resistivity of the water hose, V s is the volume of the water hose.

[0017] As can be seen from the above description, by simulating each type of resistance according to the generation principle of the resistance in the equivalent circuit, the simulation of the arc development in the equivalent circuit is realized, thereby improving the accuracy of the calculated flashover voltage.

[0018] Further, the calculating the current leakage at the current moment according to the first voltage and the circuit parameter comprises: ; In the formula, U is the first voltage; I is the current leakage; / / represents a parallel relationship; ω is an angular frequency, and j is an imaginary unit.

[0019] As can be seen from the above description, after the circuit parameter in the equivalent circuit is calculated, because the voltage is gradually obtained by iteration from the initial voltage and is a known quantity, the current leakage can be obtained according to the equation relationship among the voltage, the current and the resistance in the circuit after the resistance parameter in the equivalent circuit is obtained, so as to realize the prediction of the current leakage.

[0020] Further, the judging whether the arc development criterion is met according to the current leakage and the first leakage current comprises: calculating a judging parameter n= ; In the formula, d| I L | represents the difference between the current leakage and the first leakage current; dx represents the difference between the arc lengths at the last two times; if n>0, the arc development criterion is met.

[0021] From the above description, it can be seen that whether the arc is further developed is determined according to the change amount of the leakage current and the change amount of the current length, which conforms to the characteristics of the arc development, thereby improving the accuracy of the arc development prediction.

[0022] Further, the updating of the first arc length to obtain a first current arc length at the current moment comprises: x1=x+ ; ; In the formula, x1 represents the first current arc length after updating, and x represents the first arc length before updating. v d ( t ) represents the arc development speed, and q is the average charge in the unit length current, which is a constant.

[0023] From the above description, it can be seen that after the arc meets the arc development criterion, the arc length is updated according to the development characteristics of the arc length, thereby realizing the dynamic simulation of the arc evolution.

[0024] Further, the judging whether the arc reignition condition is met comprises: If the arc reignition condition is not met, the first current arc length is updated to obtain a second current arc length, and the step of judging whether the current arc length is greater than the creepage distance of the to-be-tested insulating surface is performed.

[0025] From the above description, it can be seen that if the arc reignition condition is not met, the arc length will change, so the arc length is updated before the size judgment of the arc length and the creepage distance is performed, thereby improving the accuracy of the finally determined flashover voltage.

[0026] Further, the updating of the first current arc length to obtain a second current arc length comprises: The updating of the first current arc length to obtain a second current arc length comprises: x2=x- ; In the formula, x2 represents the second current arc length, and x represents the first current arc length.

[0027] From the above description, it can be seen that when the arc reignition condition is not met, the arc length is reduced, thereby simulating the characteristics that the arc will increase and decrease with the change of the parameters in the equivalent circuit under the real conditions, thereby improving the accuracy of the finally obtained flashover voltage.

[0028] Please refer to Figure 6The application discloses an alternating current flashover voltage prediction terminal, and relates to the technical field of alternating current flashover voltage prediction.

[0029] The alternating current flashover voltage prediction method and terminal can be applied to the prediction of the flashover voltage of an insulator surface, especially the prediction of the flashover voltage in a wet pollution scenario. Figure 2 FIG. 1 is a schematic diagram of a model of an application scenario of the application.

[0030] FIG. 2 is a schematic diagram of an application scenario of the application. Figures 1 to 5 Embodiment one of the application is as follows: An alternating current flashover voltage prediction method comprises the following steps: S1, calculating circuit parameters of an equivalent circuit corresponding to a to-be-measured insulator surface according to a first arc length, a first leakage current and a first voltage of a previous moment of a current moment. Figure 3 FIG. 3 is an equivalent circuit diagram provided by the application.

[0031] In an optional embodiment, S1 is further preceded by S01-S03.

[0032] S01, obtaining a creepage distance corresponding to the to-be-measured insulator surface and a unit voltage of the to-be-measured insulator surface, and further obtaining simulation parameters, wherein the simulation parameters comprise equivalent salt deposit density (ESDD), non-soluble deposit density (NSDD), electrode spacing (creepage distance), pollution degree and environmental temperature of a wet pollution layer of an insulator material of the insulator surface. s rest .

[0033] S02, initializing an initial voltage U0 and an initial arc length x0 of an initial moment.

[0034] S03, calculating an initial leakage current as a leakage current of the 0th moment according to the creepage distance, the initial voltage and the initial arc length. I 0= U 0 / ( r rest L That is, in the case that there is no previous moment in the current moment, the initial method is used to construct a basic numerical value for subsequent iterative calculation, thereby providing a basic parameter for the subsequent iterative process.

[0035] In the above formula, rrest is the linear resistance of the remaining wet contamination layer.

[0036] ; wherein, a is the electrode width, d rest is the conductance of the remaining wet contamination layer, d rest related to the ambient temperature, the equivalent salt deposit density of the wet contamination layer, and the equivalent grey density, and the calculation formula is as follows: ; wherein, p ESDD represents the resistivity of the wet contamination layer under the ESDD; B, C, and D all represent preset constants, for example, B is 1.1278; C is 0.001895 ℃ -1 ; and D is 88.93; d represents a preset constant, for example, 0.877, q represents the ambient temperature; Since the arc resistance R arc ( x ), the remaining wet contamination layer resistance R rest ( x ), and other parameters will change with the leakage current, the initial leakage current needs to be calculated first. The initial length of the arc is set to x = L / 100, the initial voltage is U0=100 V, and the initial time is considered to be short and can be ignored, and only the remaining wet contamination layer resistance exists in the circuit, so the initial time t rest = U rest R , the initial value of the leakage current is r rest L I arc U L ). The initial value of the leakage current is used to calculate the corresponding arc resistance R rest ( x ) and the remaining wet contamination layer resistance R rest ( x ), the remaining wet contamination layer capacitance C rest ( x ​​​​and other parameters, the values of which are unknown at the initial time, and the initial value of the leakage current can also be understood as an approximate value that can be solved first. The calculation formula of the initial value of the leakage current is I 0= U 0 / ( r rest L ), and the calculation formula for recalculating the leakage current using these parameters is formula (1), which is used to obtain the leakage current corresponding to the new circuit parameters.

[0037] In an optional embodiment, the circuit parameters include arc resistance R arc ( x ), arc inductance G arc ( x ), residual wet pollution layer resistance R rest ( x ), residual wet pollution layer capacitance C rest ( x ), and hose resistance R s ( x ), and S1 includes S11 to S13. The value of the arc inductance is very small, so the arc inductance can be omitted in the corresponding calculation process.

[0038] S11, the arc resistance ; In the formula, p arc is the resistivity of the local arc path, r arc is the equivalent radius of the arc horn, s arc is the cross-sectional area of the local arc; and x is the first arc length.

[0039] In an optional embodiment, the dynamic changes of the arc burning environment are considered when calculating the arc resistance, and the arc feature dynamic parameters A and n are used to calculate the arc path resistivity p arc , as follows.

[0040] ; In the formula, T arc is the initial temperature of the arc, which is 3000K, l ( T arc is the thermal conductivity of the arc at the initial temperature, s restthe conductivity of the remaining wet pollution layer, e rest the relative permittivity of the remaining wet pollution layer; E arc the electric field intensity in the arc channel; J the arc channel current density, i represents the first leakage current; k and a are intermediate parameters built for simplifying the expression, whose expansion has been explained in the above formula.

[0041] S12, calculating the resistance of the remaining wet pollution layer ; calculating the capacitance of the remaining wet pollution layer ; wherein, r rest the linear resistance of the remaining wet pollution layer; S =1.45A / cm 2 , a the electrode width, i the first leakage current; p rest the resistivity of the remaining wet pollution layer; c rest the linear capacitance of the remaining wet pollution layer; e rest the relative permittivity of the remaining wet pollution layer; s rest the cross-sectional area of the remaining wet pollution layer; L the creepage distance.

[0042] S13, calculating the resistance of the water hose ; wherein, p s the resistivity of the water hose, V s the volume of the water hose.

[0043] S2, calculating the current leakage current at the current time according to the first voltage and the circuit parameters.

[0044] In an alternative embodiment, S2 comprises: (1); wherein, U is the first voltage; I is the current leakage current; / / represents a parallel relationship; ω is the angular frequency, which can be regarded as a constant in the formula, w =2π f , f the frequency, f= 50 Hz. j is the imaginary unit. The flashover development path of the wet contaminated silicone rubber surface is simulated as a series circuit of local arc and residual contamination layer, and the water belt resistance and the residual wet contamination layer resistance are in parallel, and the equivalent circuit is obtained. The electrical equation of the equivalent circuit is formula (1).

[0045] S3, judging whether the arc development criterion is met according to the current leakage current and the first leakage current, if yes, updating the first arc length to obtain a first current arc length at the current time, and judging whether the arc reignition condition is met.

[0046] In an optional embodiment, if the arc development criterion is met, the first arc length is updated to obtain a first current arc length at the current time, and the circuit parameters are recalculated according to the first current arc length and the updated current leakage current is obtained, and the current leakage current used in the subsequent steps is the updated current leakage current.

[0047] In an optional embodiment, the judging whether the arc development criterion is met according to the current leakage current and the first leakage current comprises: calculating a judgment parameter n = i - i0 / d ; In the formula, d I L | represents the difference between the current leakage current and the first leakage current; if it is the initial time, it is i - i0; if n > 0, the arc development criterion is met.

[0048] At the initial time t0, x0 = L / 100, and the arc development speed at the initial time is v0, then dx = v0 × dt × 10 -3 At the remaining time, the difference between the arc lengths at the two nearest times can be directly calculated.

[0049] In an optional embodiment, the updating the first arc length to obtain a first current arc length at the current time comprises: x1 = x + ; ; In the formula, x1 represents the updated first current arc length, which is used as the new first arc length for subsequent calculation, and x represents the first arc length before updating; v d ( t ) represents the arc development speed at t, q is the average charge in unit length current, which is treated as a constant in calculation, and represents the arc charge per unit length; i(t) represents the leakage current at t. It can be known that the arc development speed v d ( t) in the initial stage, and will increase with the development of the discharge, and will reach several kilometers per second at the moment of flashover. v d ( t ) will rise rapidly, and may reach several kilometers per second at the highest.

[0050] In an optional embodiment, the judging whether the arc reignition condition is satisfied comprises: ; wherein, U m represents the first voltage peak, U cx represents the arc reignition voltage peak, U d represents the minimum breakdown voltage of the residual arc column. When U m > U cx , it is recorded as satisfying the arc reignition condition, otherwise, it does not satisfy the arc reignition condition.

[0051] U d the calculation method of U d the value of U d : ; wherein, U da is the air breakdown voltage strength, S 0 is the heat flux at the initial arc temperature, i.e. T arc =3000K S 0=350.8J / (m·s), S b is the heat flux at the ambient temperature, is a fitting constant, , β is a fitting constant, β =1.778, r b is the arc boundary radius, t d is the time when the AC waveform reaches the peak, t d =1 / (4 f ), T is the ambient temperature.

[0052] In an alternative embodiment, the judging whether the arc reignition condition is satisfied comprises: if the arc reignition condition is not satisfied, updating the first current arc length to obtain a second current arc length, and performing the judging whether the current arc length is greater than the creepage distance of the insulation surface under test.

[0053] In an alternative embodiment, the updating the first current arc length to obtain a second current arc length comprises: x2=x- ; wherein x2 represents the second current arc length, and x represents the first current arc length.

[0054] S4, if the arc development criterion is not satisfied, increasing the first voltage, and returning to perform the calculating the circuit parameters of the equivalent circuit corresponding to the insulation surface under test step S1 with the increased first voltage.

[0055] In an alternative embodiment, the first voltage is increased by a step of 10 kV, and the arc length is returned to perform S1.

[0056] S5, if the arc reignition condition is satisfied, judging whether the current arc length is greater than the creepage distance of the insulation surface under test, and outputting the first voltage as the flashover voltage if yes. If the arc length is greater than the creepage distance of the insulation surface under test, it indicates that the arc has developed into a through arc connecting the electrodes at both ends of the insulation surface, and the voltage in the corresponding equivalent circuit at this time is the flashover voltage.

[0057] S6, if the current arc length is less than the creepage distance, returning to perform the calculating the circuit parameters of the equivalent circuit corresponding to the insulation surface under test step S1 with the arc length at the current time. Specifically, the arc resistance R arc ( x ), the residual wet pollution layer resistance R rest ( x ), the residual wet pollution layer capacitance C rest ( x ), and the water resistance R s ( x ) are recalculated according to the updated arc length x; and the updated leakage current is obtained according to formula (1), and the next round of iteration process is entered.

[0058] Please refer to Figure 4 , which is another flowchart of the AC flashover voltage prediction method of the present application, and the iteration process of the steps in the present application can be more directly observed.

[0059] In an alternative embodiment, the prediction step described above can be implemented by programming in MATLAB software.

[0060] In an alternative embodiment, the constants in the present specification are fixed values directly taken according to different environments, and for the convenience of description, the corresponding formulas are represented by letters in the formulas.

[0061] Please refer to Figure 5 , the second embodiment of the present application is: The present application provides a prediction process of applying the AC flashover voltage prediction method of the present application in a specific scenario, Figure 5 for comparison of the final prediction result and the actual result. It can be seen that the prediction result has high accuracy and small error.

[0062] Next, the present model is used to predict the flashover voltage of silicone rubber based on L 16 (4 4 ) orthogonal table, and the prediction result of the flashover test of the wet contaminated silicone rubber is taken as an example to further illustrate the beneficial effects of the present application.

[0063] 1) Select the flashover voltage as the test index, and the temperature difference between the environment and the surface of the insulating material, the relative humidity, the ESDD, and the NSDD as the test factors. The number of levels of each factor is 4, and the specific values are shown in Table 1. According to the actual operation conditions of silicone rubber insulation and the preliminary test results, the temperature in the environmental chamber is controlled at 25℃, and the level value range of the temperature difference is set to 10℃ to 20℃, and the level value range of the relative humidity is set to 65% to 80%. According to the pollution level of insulators in IEC-60815 standard, the level value range of the ESDD on the surface of the silicone rubber is set to 0mg / cm 2 -0.08mg / cm 2 , and the level value range of the NSDD is set to 0mg / cm 2 -0.48mg / cm 2 .

[0064] Table 1 Test factors and levels

[0065] According to the test factors and levels selected above, based on the principle of "uniform dispersion and uniform comparability" of orthogonal test, a four-factor and four-level orthogonal test table is designed L 16 (4 4 ), a total of 16 groups of tests, and the orthogonal test results are shown in Table 2. In order to reduce the random error caused by single test and enhance the reliability of test results, each test is repeated for 3 times, the factor level value is controlled within the acceptable error range, and the average value of 3 flashover voltages is taken as the test index value.

[0066] Table 2L 16 (4 4 )orthogonal test results

[0067] 2) based on table 2( L 16 (4 4 )orthogonal table), the corresponding flashover voltage of 16 groups of orthogonal tests is predicted by using the model, and the prediction results are shown in Figure 4 Figure 4 It can be seen from that the predicted value of the flashover voltage model of the wet contaminated silicone rubber surface is in good agreement with the test value, and the absolute value of the relative error of the 16 groups of flashover voltage is less than 15%, and the average absolute value of the relative error is 5.96%.

[0068] In order to more scientifically and reasonably evaluate the prediction accuracy of the model, the mean absolute percentage error (MAPE), root mean square error (RMSE) and mean square percentage error (MSPE) of the flashover voltage prediction results are analyzed, and the specific calculation formula is as follows:

[0069]

[0070]

[0071] Among them, U ft is the flashover voltage test value; U fp is the flashover voltage prediction value; n is the number of test groups, n = 16.

[0072] The mean absolute percentage error MAPE of the model prediction result is 0.0596, the root mean square error RMSE is 1.0375, and the mean square percentage error MSPE is 0.0186, so the flashover voltage prediction result of the model has high accuracy, and the reliability of the model is fully proved.

[0073] Please refer to Figure 6 , the third embodiment of the present application is: An alternating current flashover voltage prediction terminal 1 comprises a memory 3, a processor 2 and a computer program stored on the memory 3 and running on the processor 2, and the processor 2 implements each step in embodiment one or embodiment two when the computer program is executed, and the beneficial effects are the same as the above-mentioned alternating current flashover voltage prediction method, which will not be repeated here.

[0074] In summary, the present application provides an alternating current flashover voltage prediction method and terminal, which fully considers the influence of environmental temperature, water resistance and other factors on each parameter in the dynamic development process of alternating current arc, can make up for the inherent defects of the insulation pollution flashover static model, and obtain more accurate wet pollution insulation alternating current flashover voltage prediction. And it can be realized based on MATLAB software programming, and the algorithm construction considers the time-varying nature of arc characteristic parameters, residual wet pollution layer resistance and other circuit parameters in the local arc development process under different environmental temperatures, and can simulate the dynamic process of arc and dry area development at the moment of flashover. This prediction method based on the physical process of insulation wet pollution flashover can more comprehensively simulate the actual flashover situation, and can obtain more accurate and effective flashover voltage prediction results. The prediction results obtained by the present application can provide reference for the explanation of wet pollution insulation material surface flashover mechanism and the improvement of discharge model.

[0075] The above is only an embodiment of the present application, and does not limit the patent range of the present application, and any equivalent transformation or direct or indirect application in related technical fields based on the content of the specification and drawings of the present application is also included in the patent protection range of the present application.

Claims

1. A method for predicting AC flashover voltage, characterized in that, The method includes: The circuit parameters of the equivalent circuit corresponding to the insulation surface under test are calculated based on the first arc length, first leakage current, and first voltage of the previous moment at the current moment. Calculate the current leakage current at the current moment based on the first voltage and the circuit parameters; Based on the current leakage current and the first leakage current, determine whether the arc development criterion is met. If so, update the first arc length to obtain the first current arc length at the current moment, and determine whether the arc reignition condition is met. If the arc development criterion is not met, the first voltage is increased, and the process returns to the step of calculating the circuit parameters of the equivalent circuit corresponding to the insulation surface under test with the increased first voltage. If the arc reignition condition is met, determine whether the current arc length is greater than the creepage distance of the insulation surface to be tested. If so, output the first voltage as the flashover voltage. If the current arc length is less than the creepage distance, then return to the step of calculating the circuit parameters of the equivalent circuit corresponding to the insulation surface under test, based on the current arc length.

2. The AC flashover voltage prediction method according to claim 1, characterized in that, Also includes: Obtain the creepage distance corresponding to the insulation surface under test and the unit voltage of the insulation surface under test; Initialize the initial voltage and initial arc length at the initial moment; The initial leakage current is calculated based on the creepage distance, initial voltage, and initial arc length as the leakage current at time 0.

3. The AC flashover voltage prediction method according to claim 1, characterized in that, The circuit parameters include arc resistance, residual wet sludge layer resistance, residual wet sludge layer capacitance, and water tape resistance.

4. The AC flashover voltage prediction method according to claim 3, characterized in that, The calculation of the circuit parameters of the equivalent circuit corresponding to the insulating surface under test based on the first arc length, first leakage current, and first voltage of the previous moment includes: Calculate arc resistance ; In the formula, ρ arc The resistivity of the local arc path, r arc The equivalent radius of the arc head. s arc This refers to the local arc cross-sectional area; x The length of the first electric arc; Calculate the resistance of the remaining wet sludge layer ; Calculate the capacitance of the remaining wet sludge layer ; In the formula, r rest The linear resistance of the remaining wet sludge layer; S is a constant. a For electrode width, i This is the first leakage current; ρ rest The resistivity of the remaining wet contaminant layer; c rest The linear capacitance of the remaining wet sludge layer; ε rest The relative permittivity of the remaining wet contaminant layer; s rest This represents the cross-sectional area of ​​the remaining wet contaminant layer on the silicone rubber surface. L Creepage distance; Calculate water resistance ; In the formula, ρ s The resistivity of the water belt. V s This represents the volume of the water strip.

5. The AC flashover voltage prediction method according to claim 4, characterized in that, The calculation of the current leakage current at the current moment based on the first voltage and the circuit parameters includes: ； In the formula, U is the first voltage; I is the current leakage current; / / indicates parallel relationship; ω is the angular frequency; and j is the imaginary unit.

6. The AC flashover voltage prediction method according to claim 1, characterized in that, The step of determining whether the arc development criterion is met based on the current leakage current and the first leakage current includes: Calculate the judgment parameter n= ; In the formula, d| I L | represents the difference between the current leakage current and the first leakage current; dx represents the difference between the two most recent arc lengths; if n > 0, then the arc development criterion is satisfied.

7. The AC flashover voltage prediction method according to claim 1, characterized in that, The step of updating the first arc length to obtain the first current arc length at the current moment includes: x1=x+ ; ； In the formula, x1 represents the updated first current arc length, and x represents the first arc length before the update; v d ( t ) represents the arc propagation speed at time t, and q is the average charge per unit length of current, which is a constant.

8. The AC flashover voltage prediction method according to claim 1, characterized in that, The determination of whether the arc reignition condition is met includes: If the arc reignition condition is not met, the first current arc length is updated to obtain the second current arc length, and the step of determining whether the current arc length is greater than the creepage distance of the insulation surface to be tested is executed.

9. The AC flashover voltage prediction method according to claim 8, characterized in that, The step of updating the first current arc length to obtain the second current arc length includes: x2=x- ; In the formula, x2 represents the second current arc length, and x represents the first current arc length.

10. An AC flashover voltage prediction terminal, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program to implement the various steps of the AC flashover voltage prediction method according to any one of claims 1-9.

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