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CN107992713B - Combined air gap breakdown voltage prediction method - Google Patents

Combined air gap breakdown voltage prediction method Download PDF

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CN107992713B
CN107992713B CN201810070447.4A CN201810070447A CN107992713B CN 107992713 B CN107992713 B CN 107992713B CN 201810070447 A CN201810070447 A CN 201810070447A CN 107992713 B CN107992713 B CN 107992713B
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邱志斌
阮江军
金颀
王学宗
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Wuhan University WHU
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Abstract

The invention relates to a high voltage and insulation technology, in particular to a combined air gap breakdown voltage prediction method, which comprises the steps of defining an air gap between a high-voltage electrode and a suspension conductor as a first gap, defining an air gap between the suspension conductor and a grounding electrode as a second gap, establishing a three-dimensional model of the combined air gap, calculating electrostatic field distribution by adopting a finite element method, extracting a set of electric field characteristics on the shortest path of the first gap and the second gap from the electrostatic field distribution, taking the set of electric field characteristics as an input parameter of SVR (space vector regression), and determining a breakdown gap and a breakdown voltage value thereof through breakdown voltage one-time prediction; performing electrostatic field secondary calculation, electric field feature set extraction and breakdown voltage secondary prediction according to the potential change condition of the suspended conductor after breakdown, and determining the breakdown voltage value of the breakdown gap; and comparing the two breakdown voltage values, and taking the larger value as the predicted value of the overall breakdown voltage of the combined air gap. The method is beneficial to reducing the test quantity and provides theoretical guidance for the optimization of the combined air gap structure.

Description

Combined air gap breakdown voltage prediction method
Technical Field
The invention belongs to the technical field of high voltage and insulation, and particularly relates to a combined air gap breakdown voltage prediction method.
Background
The combined air gap is a metal conductor with a certain size between the high-voltage electrode and the low-voltage electrode, and the electric field distribution between the original gaps is greatly influenced, so that the high-voltage electrode, the metal conductor and the low-voltage electrode form the combined air gap, and the metal conductor presents a suspension potential. The combined air gap widely exists in power systems, such as a suspended conductor in live-line work of a power transmission line, foreign matters such as bird droppings and the like falling on the power transmission line, birds close to the power transmission line and the like. The rod, the ball and the plate are typical electrodes for researching the air gap discharge characteristics, and the research on the combined air gap formed by the electrodes is helpful for understanding the combined gap discharge mechanism and lays a foundation for researching more complex combined gaps.
Combined air gap insulation breakdown with suspended potential conductors is a complex physical process that involves the mating of two single gap insulation breakdowns. For a combined air gap of different structures, it is uncertain which gap breaks down first. Under the applied voltage, when a certain gap breaks down, the potential of the suspension conductor changes, and the combined gap can be equivalent to a single gap; the other gap breaks down immediately or does not break down at the current voltage, and breakdown occurs after boosting continues.
At present, the Breakdown voltage of the combined air gap is mainly obtained through a discharge test at home and abroad, and due to the problems of high cost and long period of the test research, part of researchers have developed the research on the discharge mechanism of the combined air gap for live working, and have proposed some discharge voltage calculation models, the most representative of which is the Rizk model ("Effect of flowing generating connecting object on critical switching impact of air insulation", IEEE Transactions on Power Delivery, 1995, volume 10, phase 3) and the modification form thereof. The Rizk model is a semi-empirical model obtained based on a discharge mechanism and some simplifying assumptions, has limited applicability, and is difficult to calculate and obtain the breakdown voltage of air gaps of various engineering structure combinations.
Therefore, the combined air gap breakdown voltage prediction research is developed, an effective prediction method is provided, the test workload and the test cost are reduced, a foundation can be laid for developing the combined air gap breakdown voltage prediction of the engineering structure, the combined gap configuration in the practical engineering application is guided, and the method has important engineering significance.
Disclosure of Invention
The invention aims to provide a method for obtaining the breakdown voltage of a combined air gap formed by different high-voltage electrodes, a suspension conductor and a grounding electrode through simulation calculation and intelligent prediction alternative discharge tests.
In order to achieve the purpose, the invention adopts the technical scheme that: a combined air gap breakdown voltage prediction method comprises the following steps:
step 1, defining an air gap between a high-voltage electrode and a suspension conductor as a first gap, defining an air gap between the suspension conductor and a grounding electrode as a second gap, and establishing a three-dimensional model of a combined air gap;
step 2, performing primary calculation on an electrostatic field by adopting a finite element method, extracting a set of electric field characteristics on the shortest path of a first gap and a second gap from a calculation result, taking the set of electric field characteristics as an input parameter of a support vector regression, and determining a breakdown gap and a breakdown voltage value thereof through primary prediction of breakdown voltage;
step 3, performing electrostatic field secondary calculation, electric field feature set extraction and breakdown voltage secondary prediction according to the potential change condition of the suspended conductor after breakdown, and determining the breakdown voltage value of the breakdown gap;
and 4, comparing the breakdown voltage values of the first breakdown gap and the second breakdown gap to obtain the predicted value of the overall breakdown voltage of the combined air gap.
In the above combined air gap breakdown voltage prediction method, the implementation of the voltage prediction method comprises the following steps:
step 2.1, performing primary electrostatic field calculation and electric field feature set extraction, establishing a three-dimensional simulation model of the combined air gap by adopting finite element analysis software, loading high potential on a high-voltage electrode, loading zero potential on a grounding electrode and a cut air boundary, performing potential freedom degree coupling on a suspended conductor, and performing primary electrostatic field calculation; extracting an electric field characteristic set on the shortest path of the first gap and the second gap according to the calculation result, and carrying out normalization processing on each characteristic quantity;
step 2.2, performing one-time breakdown voltage prediction, establishing a prediction model by adopting a support vector regression machine, selecting an air gap with a similar structure and a known breakdown voltage as a training sample according to the structural characteristics of the first gap and the second gap, and training the support vector regression model; respectively inputting the electric field characteristic sets on the shortest paths of the first gap and the second gap into a trained support vector regression model, outputting breakdown voltage predicted values of the first gap and the second gap, comparing the breakdown voltage predicted values, determining the gap which is broken down first, and recording the breakdown voltage predicted value U1；
Step 2.3, performing electrostatic field secondary calculation and electric field feature set extraction, after a certain gap is broken down, regarding the suspended conductor as being equal in potential to the other electrode of the gap, performing electrostatic field secondary calculation according to the potential change condition, loading high potential to a high-voltage electrode, loading zero potential to a grounding electrode and a cut air boundary, if the first gap is broken down first, loading high potential to the suspended conductor, and if the second gap is broken down first, loading zero potential to the suspended conductor; and extracting the shortest path characteristic set of the non-breakdown gap from the secondary calculation result of the electrostatic field, and performing normalization processing on each characteristic quantity.
Step 2.4, secondary prediction of breakdown voltage, namely inputting the electric field characteristic set extracted in the step 2.3 into a support vector regression model, secondarily predicting the breakdown voltage of the gap without breakdown, and recording the predicted value U of the breakdown voltage2Will U is2And U in step 2.21Making a comparison if U1＞U2The predicted value of the breakdown voltage of the combined air gap is U1(ii) a If U is2＞U1It is shown that after the first gap breaks down, the second gap has not broken down yet and the voltage still needs to be raised to U2The combined gap can be completely broken down, and the predicted value of the breakdown voltage is U2。
In the above-described combined air gap breakdown voltage prediction method, the shortest path of the first gap is a straight path having the shortest distance between the high-voltage electrode and the floating conductor, and the shortest path of the second gap is a straight path having the shortest distance between the floating conductor and the ground electrode.
In the method for predicting breakdown voltage of combined air gap, the characteristic set of the electric field includes electric field strength, electric field gradient, electric field square, electric field integral and electric field non-uniformity.
In the combined air gap breakdown voltage prediction method, the voltage prediction method is suitable for various air gap structures containing suspended potential conductors.
The invention has the beneficial effects that: the breakdown voltage of the combined air gap is obtained through prediction by combining electric field simulation calculation and machine learning, so that the test workload is reduced; can provide theoretical guidance for optimizing and combining the air gap structure, has wide applicability and is beneficial to engineering application.
Drawings
FIG. 1 is a flow chart of a combined air gap breakdown voltage prediction according to one embodiment of the present invention;
FIG. 2 is a diagram illustrating an exemplary structure and shortest path of a combined air gap according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a combination gap A according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a combined gap B according to an embodiment of the present invention;
FIG. 5 shows the result of one calculation of the electric field of the combined gap A according to one embodiment of the present invention;
FIG. 6 shows the result of one calculation of the electric field of the combined gap B according to one embodiment of the present invention;
FIG. 7 shows the electric field quadratic calculation of the combined gap A according to one embodiment of the present invention;
FIG. 8 shows the second calculation of the electric field of the combined gap B according to one embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The embodiment is realized by adopting the following technical scheme that a combined air gap breakdown voltage prediction method is characterized in that an air gap between a high-voltage electrode and a suspension conductor is defined as a first gap 1, an air gap between the suspension conductor and a grounding electrode is defined as a second gap 2, a three-dimensional model of the combined air gap is established, the electrostatic field distribution of the combined air gap is calculated by adopting a finite element method, an electric field characteristic set on the shortest path of the first gap 1 and the second gap 2 is extracted from a calculation result and is used as an input parameter of a Support Vector Regression (SVR), and the first breakdown gap and a breakdown voltage value thereof are determined through breakdown voltage one-time prediction; performing electrostatic field secondary calculation, electric field feature set extraction and breakdown voltage secondary prediction according to the potential change condition of the suspended conductor after breakdown, and determining the breakdown voltage value of the breakdown gap; and obtaining the predicted value of the overall breakdown voltage of the combined air gap by comparing the breakdown voltage values of the first and the second breakdown gaps.
The specific implementation comprises the following steps:
1. and (4) performing primary calculation of an electric field and extracting characteristics. Establishing a three-dimensional simulation model of the combined air gap by adopting finite element analysis software, loading high potential on a high-voltage electrode, loading zero potential on a ground electrode and an intercepted air boundary, coupling potential freedom degrees of a suspended conductor, and performing primary electrostatic field calculation; and extracting the electric field characteristic set on the shortest path of the first gap 1 and the second gap 2 according to the calculation result, and carrying out normalization processing on each characteristic quantity.
2. The breakdown voltage is predicted once. Establishing a prediction model by adopting a support vector regression machine, selecting an air gap with a similar structure and known breakdown voltage as a training sample according to the structural characteristics of the first gap 1 and the second gap 2, and training an SVR model; respectively inputting the electric field characteristic sets of the first gap 1 and the second gap 2 into the trained SVR model, outputting breakdown voltage predicted values of the first gap 1 and the second gap 2, comparing the sizes of the two, determining the gap which is broken down first, and recording the breakdown voltage predicted value U1。
3. And (4) electric field secondary calculation and feature extraction. After a certain gap is broken down, the suspended conductor and the other electrode of the gap are considered to be equipotential, electric field secondary calculation is carried out according to the potential change condition, high potential is loaded on a high-voltage electrode, zero potential is loaded on a grounded electrode and a cut air boundary, if the gap 1 is broken down first, high potential is loaded on the suspended conductor, and if the gap 2 is broken down first, zero potential is loaded on the suspended conductor. And extracting the shortest path characteristic set of the non-breakdown gap from the electric field secondary calculation result, and carrying out normalization processing on each characteristic quantity.
4. And (5) secondarily predicting the breakdown voltage. Inputting the electric field characteristic set extracted in the step 3 into an SVR model, secondarily predicting the breakdown voltage of the gap without breakdown, and recording the predicted value U of the breakdown voltage2Will U is2And U in step 21Making a comparison if U1＞U2After the breakdown of the first gap, the second gap is broken down immediately, and the predicted value of the breakdown voltage of the combined air gap is U1(ii) a If U is2＞U1After the first gap breaks down, the second gap is not broken down, and the voltage is still required to be increased to U2The combined gap is completely broken down, i.e. the predicted value of breakdown voltage is U2。
The shortest path of the first gap 1 is a straight path having the shortest distance between the high-voltage electrode and the floating conductor, and the shortest path of the second gap 2 is a straight path having the shortest distance between the floating conductor and the ground electrode.
Moreover, the electric field characteristic set includes physical quantities related to an electric field, such as electric field strength, electric field gradient, electric field square, electric field integral, electric field unevenness, and the like.
Moreover, the prediction method is suitable for various air gap structures containing the suspension potential conductor.
In this embodiment, the breakdown voltages of the combined air gaps of the two structures under the action of the positive polarity direct current voltage and the negative polarity direct current voltage are taken as objects, and the breakdown voltages are predicted by the prediction method of this embodiment and compared with the test result.
The two types of combined air gaps in this embodiment are referred to as "The effect of a flowing conductor on The breaking down string of a DC gap at sidewalls" (IEEE Power Engineering Society and Exposion in Africa, 2012), and are denoted as combined gap A and combined gap B, respectively.
Fig. 1 is a flowchart illustrating a breakdown voltage prediction of a combined air gap according to the present embodiment, taking a rod-sphere-plate combined air gap as an example, and fig. 2 is a schematic diagram illustrating a shortest path between a first gap 1 and a second gap 2.
Referring to fig. 1, the present embodiment includes the following steps:
firstly, calculating an electric field once and extracting characteristics.
The schematic structural diagrams of the combined gap A and the combined gap B are respectively shown in fig. 3 and fig. 4, wherein the high-voltage electrode is a 30-degree conical rod, the rod body is 0.5m long, and the diameter is 16 mm; the grounding electrode is a plate electrode with the length of 2.0m, the width of 1.2m and the thickness of 2 mm; the suspended conductor is a brass ball electrode with the diameter of 150mm, and the tail end of the suspended conductor is provided with a section of cylindrical flat-head rod with the length of 100mm and the diameter of 5 mm. The distance from the conical rod to the floating ball electrode is a first gap 1, and the distance from the floating ball electrode to the plate electrode is a gap 2. For the combined gap a, the suspended conductor is upright, as shown in fig. 3, the lengths of the first gap 1 and the second gap 2 are both 25cm, and the positive polarity direct current breakdown voltage test value of the combined gap a is 263.8 kV; as shown in fig. 4, the length of the first gap 1 was 4.375cm, the length of the second gap 2 was 13.125cm, and the negative polarity dc breakdown voltage test value of the combined gap B was 223.9 kV.
And respectively establishing a three-dimensional simulation model of the combined gap A and the combined gap B by adopting finite element analysis software ANSYS, loading unit potential 1V to the conical rod electrode, loading zero potential to the plate electrode and the cut air boundary, coupling the potential freedom degree of the suspension ball electrode, and performing primary electrostatic field calculation. The results of the first calculation of the electrostatic fields of the combined gap a and the combined gap B are shown in fig. 5 and 6, respectively. And extracting the electric field characteristic set on the shortest path of the first gap 1 and the second gap 2 according to the calculation result. For the combined gap A, the shortest path of the first gap 1 is a straight path from the tip of the conical rod to the suspension ball, and the second gap 2 is a straight path from the butt of the suspension ball to the plate electrode; for the combined gap B, the first gap 1 is a straight line path from the tip of the conical rod to the flat head rod at the tail end of the floating ball, and the second gap 2 is a straight line path from the floating ball to the plate electrode.
And for the combined gap A and the combined gap B, extracting a plurality of sampling points on the shortest paths of the first gap 1 and the second gap 2 respectively, extracting the electric field intensity and coordinate information of each sampling point, and calculating corresponding electric field characteristic quantities. The electric field characteristic includes physical quantities related to the electric field, such as electric field strength, electric field gradient, electric field square, electric field non-uniformity, etc., and table 1 shows a typical shortest path electric field characteristic set. Each feature quantity in table 1 obtained by calculation was normalized to the [0, 1] interval.
TABLE 1 electric field characteristics set for shortest path
Figure BDA0001558005080000081
Secondly, breakdown voltage is predicted once.
And (3) establishing a prediction model by adopting a support vector regression machine, and selecting an air gap with a similar structure and a known breakdown voltage as a training sample according to the structural characteristics of the first gap 1 and the second gap 2. For the combined gap A, a training sample set of the SVR model comprises a rod-plate gap with a rod diameter of 0.4cm and a gap of 8-9 cm and a rod-rod gap with a rod diameter of 0.2-0.4 cm and a distance of 50 cm; for the combined gap B, the training sample set of the SVR model comprises rod-plate gaps with the diameter of 0.4cm and the distance of 4-9 cm, plate-rod gaps with the rod length of 5cm, the diameter of 1-6 cm and the distance of 10cm, and plate-rod gaps with the rod length of 10cm, the diameter of 2-20 cm and the distance of 10 cm. The relevant test data of the above training samples are cited from "Breakwown process of a rod-to-plate gap in an underlying thermal air under dc voltage stress" (IEEE Transactions on Electrical Insulation, Vol. 26, No. 2, 1991), "DC Breakdown voltage characteristics of the rod-rod gap" (HV, No. 2, 1990), and "relationship between DC Breakdown voltage and corona morphology" (HV technique, No. 4, 1984).
And respectively establishing a finite element model of the training sample set to carry out electrostatic field calculation and electric field characteristic set extraction, and further training the SVR model to enable the SVR model to have generalization popularization capability. For the combined gap A and the combined gap B, the electric field characteristic sets of the first gap 1 and the second gap 2 are respectively input into the corresponding SVR models and outputThe breakdown voltage of the gap 1 and the gap 2 is predicted once. According to the one-time prediction result, for the combined gap a, the breakdown voltages of the first gap 1 and the second gap 2 are 221.67kV and 1561.13kV respectively, and the breakdown voltage of the second gap 2 is much larger than that of the first gap 1, so that the first gap 1 is broken down first under the loading voltage. For combined gap B, the breakdown voltages of first gap 1 and second gap 2 were 70.33kV and 608.55kV, respectively, and likewise, the breakdown voltage of second gap 2 was much greater than gap 1, indicating that first gap 1 broke down first. Recording the first gap 1 breakdown voltage one-time prediction results U of the combined gap A and the combined gap B respectively1A221.67kV and U1B＝70.33kV。
Thirdly, electric field secondary calculation and feature extraction.
After the first gap 1 is broken down, the electric arc voltage drop is ignored, the suspended conductor and the high-voltage electrode (conical rod) are considered to be equipotential, electric field secondary calculation is carried out according to the potential change condition, the conical rod and the suspended conductor are loaded with high potential, and zero potential is loaded on the plate electrode and the cut-off air boundary. The results of the electric field secondary calculation of the combined gap a and the combined gap B are shown in fig. 7 and 8, respectively. And extracting the shortest path characteristic set of the non-breakdown gap, namely the second gap 2, from the electric field secondary calculation result, and carrying out normalization processing on each characteristic quantity.
And fourthly, predicting breakdown voltage twice.
Respectively inputting the electric field characteristic set of the second gap 2 extracted in the third step into corresponding SVR models for the combined gap A and the combined gap B, secondarily predicting the breakdown voltage of the second gap 2, and recording the predicted value U of the breakdown voltage2AAnd U2BBased on the prediction, U2A＝254.46kV，U2B＝229.53kV。
Will U2AAnd U2BRespectively with U in the second step1AAnd U1BBy comparison, it can be seen that U2A＞U1A，U2B＞U1BFor the combined gap a and the combined gap B, after the first gap 1 breaks down, the second gap 2 is not broken down, and the voltage is still required to be increased to U2AAnd U2BThe combined gap is completeAnd (4) breakdown.
According to the results, the predicted value of the breakdown voltage of the combined gap A under the action of the positive polarity direct current voltage is 254.46kV, and the relative error is-3.5% compared with the tested value of 263.8 kV; the predicted breakdown voltage of the combined gap B under the action of the negative polarity dc voltage was 229.53kV, and the relative error was 2.5% compared to the test value of 223.9 kV. The error result is small, and the effectiveness of the combined air gap breakdown voltage prediction method provided by the invention is verified.
Therefore, by the prediction method provided by the embodiment, the breakdown voltage of the combined air gap can be predicted by combining electric field simulation calculation and SVR machine learning, so that a discharge test is replaced, the test workload is reduced, and theoretical guidance can be provided for researching a combined gap discharge mechanism and optimizing a combined gap structure.
It should be understood that parts of the specification not set forth in detail are well within the prior art.
Although specific embodiments of the present invention have been described above with reference to the accompanying drawings, it will be appreciated by those skilled in the art that these are merely illustrative and that various changes or modifications may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is only limited by the appended claims.

Claims (4)

1.一种组合空气间隙击穿电压预测方法，其特征是，包括以下步骤：1. a combined air gap breakdown voltage prediction method, is characterized in that, comprises the following steps: 步骤1、将高压电极与悬浮导体之间的空气间隙定义为第一间隙，将悬浮导体与接地电极之间的空气间隙定义为第二间隙，建立组合空气间隙的三维模型；Step 1. Define the air gap between the high-voltage electrode and the suspension conductor as the first gap, define the air gap between the suspension conductor and the ground electrode as the second gap, and establish a three-dimensional model of the combined air gap; 步骤2、采用有限元法进行静电场一次计算，从计算结果中提取第一间隙和第二间隙最短路径上的电场特征集，将其作为支持向量回归机的输入参量，通过击穿电压一次预测，确定先击穿间隙及其击穿电压值；Step 2. Use the finite element method to perform a primary calculation of the electrostatic field, extract the electric field feature set on the shortest path of the first gap and the second gap from the calculation result, use it as the input parameter of the support vector regression machine, and predict the breakdown voltage once , determine the first breakdown gap and its breakdown voltage value; 步骤3、根据击穿后悬浮导体的电位变化情况进行静电场二次计算、电场特征集提取及击穿电压二次预测，确定后击穿间隙的击穿电压值；Step 3. Perform secondary calculation of electrostatic field, extraction of electric field feature set and secondary prediction of breakdown voltage according to the potential change of the suspended conductor after breakdown, to determine the breakdown voltage value of the rear breakdown gap; 步骤4、通过比较先、后击穿两个间隙的击穿电压值，得到组合空气间隙的整体击穿电压预测值；Step 4. Obtain the predicted value of the overall breakdown voltage of the combined air gap by comparing the breakdown voltage values of the first and second gaps; 电压预测方法的实现包括以下步骤：The implementation of the voltage prediction method includes the following steps: 步骤2.1、静电场一次计算及电场特征集提取，采用有限元分析软件建立组合空气间隙的三维仿真模型，对高压电极加载高电位，对接地电极和截断空气边界加载零电位，对悬浮导体进行电位自由度耦合，进行静电场一次计算；根据计算结果，提取第一间隙和第二间隙最短路径上的电场特征集，对各个特征量进行归一化处理；Step 2.1, one-time calculation of electrostatic field and extraction of electric field feature set, use finite element analysis software to establish a three-dimensional simulation model of combined air gap, load high potential on high voltage electrode, load zero potential on ground electrode and truncated air boundary, and conduct potential on floating conductor. The degree of freedom coupling is used to calculate the electrostatic field once; according to the calculation result, the electric field feature set on the shortest path of the first gap and the second gap is extracted, and each feature quantity is normalized; 步骤2.2、击穿电压一次预测，采用支持向量回归机建立预测模型，根据第一间隙和第二间隙的结构特点，选取具有相似结构、已知击穿电压的空气间隙作为训练样本，对支持向量回归机模型进行训练；将第一间隙和第二间隙最短路径上的电场特征集分别输入至训练后的支持向量回归机模型，输出第一间隙和第二间隙的击穿电压预测值，比较两者大小，确定先击穿的间隙，并记录其击穿电压预测值U1；Step 2.2. The breakdown voltage is predicted once, and the support vector regression machine is used to establish a prediction model. According to the structural characteristics of the first gap and the second gap, air gaps with similar structures and known breakdown voltages are selected as training samples. The regression machine model is trained; the electric field feature sets on the shortest path of the first gap and the second gap are respectively input into the trained support vector regression machine model, and the breakdown voltage prediction value of the first gap and the second gap is output, and the two are compared. Determine the gap that breaks down first, and record the predicted value U 1 of its breakdown voltage; 步骤2.3、静电场二次计算及电场特征集提取，当某一间隙击穿后，视为悬浮导体与该间隙另一电极等电位，根据电位变化情况进行静电场二次计算，对高压电极加载高电位，对接地电极和截断空气边界加载零电位，若第一间隙先击穿，则对悬浮导体加载高电位，若第二间隙先击穿，则对悬浮导体加载零电位；从静电场二次计算结果中提取未击穿间隙的最短路径特征集，并对各个特征量进行归一化处理，Step 2.3. Secondary calculation of electrostatic field and extraction of electric field feature set. When a certain gap is broken down, it is regarded as equipotential between the suspended conductor and the other electrode of the gap, and the secondary calculation of electrostatic field is carried out according to the change of potential, and the high voltage electrode is loaded. High potential, zero potential is applied to the grounding electrode and the cut-off air boundary. If the first gap breaks down first, then a high potential is applied to the suspended conductor. If the second gap breaks down first, zero potential is applied to the suspended conductor; from the electrostatic field two Extract the shortest path feature set without breakdown gap from the calculation result, and normalize each feature amount, 步骤2.4、击穿电压二次预测，将步骤2.3中提取的电场特征集输入至支持向量回归机模型，对未击穿间隙的击穿电压进行二次预测，并记录其击穿电压预测值U2，将U2与步骤2.2中的U1进行比较，若U1＞U2，表明第一个间隙击穿后，第二个间隙会立刻击穿，组合空气间隙的击穿电压预测值为U1；若U2＞U1，表明第一个间隙击穿后，第二个间隙尚未击穿，仍需继续升高电压至U2，组合间隙才会完全击穿，击穿电压预测值为U2。Step 2.4, secondary prediction of breakdown voltage, input the electric field feature set extracted in step 2.3 into the support vector regression machine model, perform secondary prediction on the breakdown voltage of the unbroken gap, and record the predicted value of breakdown voltage U 2. Compare U 2 with U 1 in step 2.2. If U 1 > U 2 , it means that after the first gap breaks down, the second gap will break down immediately. U 1 ; if U 2 >U 1 , it means that after the first gap breaks down, the second gap has not yet broken down, and it is necessary to continue to increase the voltage to U 2 , and the combined gap will break down completely. The predicted value of breakdown voltage is U 2 . 2.如权利要求1所述的组合空气间隙击穿电压预测方法，其特征是，第一间隙的最短路径为高压电极与悬浮导体之间具有最短距离的直线路径，第二间隙的最短路径为悬浮导体与接地电极之间具有最短距离的直线路径。2. combined air gap breakdown voltage prediction method as claimed in claim 1 is characterized in that, the shortest path of the first gap is the straight line path with the shortest distance between the high voltage electrode and the suspended conductor, and the shortest path of the second gap is The straight path with the shortest distance between the suspended conductor and the ground electrode. 3.如权利要求1所述的组合空气间隙击穿电压预测方法，其特征是，电场特征集包括电场强度、电场梯度、电场平方、电场积分、电场不均匀度。3 . The combined air gap breakdown voltage prediction method according to claim 1 , wherein the electric field feature set includes electric field strength, electric field gradient, electric field square, electric field integral, and electric field unevenness. 4 . 4.如权利要求1所述的组合空气间隙击穿电压预测方法，其特征是，电压预测方法适用于含悬浮电位导体的各类空气间隙结构。4 . The combined air gap breakdown voltage prediction method according to claim 1 , wherein the voltage prediction method is applicable to various air gap structures containing suspended potential conductors. 5 .
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