CN111725771A - A zigzag design of the end part of the explosion-proof device of a 220kV metal type high-voltage cable joint - Google Patents

Abstract

The invention discloses a fold-line design for the end portion of an explosion-proof device of a 220kV metal type high-voltage cable joint. Using the finite element calculation method, based on the principle of electromagnetic-heat and stress field coupling, the stress on the inner wall of the end of the explosion-proof shell of the 220kV metal type high-voltage cable joint under different structures is calculated. Through the simulation calculation, the relationship between different deflection angles and the maximum stress value is obtained. Combined with the practicability and economy of the protection device, the deflection angle of the broken line at the end of the explosion-proof device of the 220kV metal type high-voltage cable joint is 60°; The height and thickness of the flange are optimized at the connection with the shell, so that the stress distribution at the vertex of the end polyline can be balanced. Through simulation calculation, the optimized flange height and thickness are 20mm and 50mm respectively. In the present invention, by comparing the folded-line end structure and the radian-shaped end structure, it is believed that the folded-line end structure has better economic benefits under the same technical conditions.

Description

A zigzag design of the end part of the explosion-proof device of a 220kV metal type high-voltage cable joint

technical field

The invention relates to the field of 220kV high-voltage cable joint protection, in particular to a broken-line design of an end portion of a 220kV metal-type high-voltage cable joint protection device.

Background technique

Due to the complex structure, on-site installation and uneven installation process, the high-voltage cable joint has become a weak link in the operation of high-voltage power cables. According to statistics, more than 70% of cable faults occur at the joints. When the insulation breakdown fault occurs in the high-voltage cable joint, the arc will release huge energy in the insulation breakdown channel, causing the cable joint to burn and explode. The shock wave or debris released by the explosion of the cable joint will cause huge damage to other surrounding power facilities and operation and maintenance personnel. Therefore, it is necessary to install an explosion-proof device at the high-voltage cable joint to avoid secondary damage caused by the explosion of the cable joint.

At present, a series of high-voltage cable joint explosion-proof devices have been developed on the market to reduce the harm caused by this explosion accident. However, these explosion-proof devices, especially at their ends, have the problem of unbalanced internal pressure. When the cable joint explodes, the impact force distribution of the huge arc energy on the inside of the protection device will be distorted at the end, causing the impact stress on some parts of the end to be much greater than other parts, making the end part easier be exploded, thus affecting the explosion-proof effect of the protective device. Tests were carried out on the common explosion-proof casings of cable joints in the current market. The results showed that after the explosion of the cable joints, the main part of the joint protection device was still relatively intact, while the end parts were severely damaged, and debris splashed. Therefore, it is necessary to reasonably design the shape of the end portion of the explosion-proof device to balance the impact stress inside the device during explosion.

Due to the larger energy of the short-circuit arc, metal casings (mostly aluminum-magnesium alloys) are generally used for high-voltage cable joint explosion-proof devices of transmission voltage levels, and they are segmented structures, that is, including the middle body part and the end parts at both ends. At present, most of the structure of the end part of the explosion-proof device of the high-voltage cable joint is designed only by the experience of the manufacturer, and there is no measure to balance the shock wave pressure distribution on the inner wall of the end part. It is usually necessary to increase the thickness of the end of the explosion-proof device to achieve the explosion-proof effect. It is an effective way to equalize the internal stress distribution of the device by adopting the shape of the end head with a certain bending arc. However, for the high-voltage cable joint explosion-proof device, the use of radian design will significantly increase the difficulty and manufacturing cost in the processing process. In addition, the arc design will increase the length of the end part, which may be limited by the actual installation conditions of the explosion-proof device, and the feasibility is low.

From the above analysis, it can be seen that the arc design of the end part has problems in processing, use and cost; the polyline design must have a vertex, and the pressure distribution will be concentrated at this point. However, the use of flange connection at the apex of the chamfer is equivalent to local strengthening of the structure, which will reduce the stress value at this point. Therefore, by designing the deflection angle of the broken line at the end and the height and wall thickness of the flange connected to the protective device body, the problem that the pressure distribution of the inner wall of the broken line design is concentrated at the corner can be solved.

SUMMARY OF THE INVENTION

The invention provides a fold-line design of the end portion of a 220kV metal type high-voltage cable joint protection device, which is used to solve the problems of processing, use and cost of the arc-shaped design of the end portion of the existing 220kV high-voltage cable joint protection device. And the problem that the stress distribution of the inner wall of the polyline design is concentrated at the corners.

In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

A folded-line structure at the end of a 220kV metal type high-voltage cable joint protection device, comprising:

In the explosion-proof device of 220kV high-voltage cable joints, the folded-line structure with deflection angle is selected at the end part, and the flange connection is adopted at the apex of the folded corner, which is equivalent to the local strengthening of the structure, so that the degree of stress distortion at the apex is decline.

Preferably, when the 220kV metal type high-voltage cable joint fails, the energy released by the short-circuit arc acts on the explosion-proof casing through the airflow, and generates stress on the casing. The position where the maximum stress value and the most obvious stress distortion appear on the inner wall of the explosion-proof casing is the protection device. The connection between the end and the body, that is, at the apex of the corner.

Preferably, for the calculation of stress distribution at the end of the explosion-proof device for 220kV metal type high-voltage cable joints, finite element software is used to establish a simulation model of the explosion process of the explosion-proof device for 220kV metal type high-voltage cable joints, through thermal-fluid-stress multi-physical field coupling According to the principle of calculating the impact stress distribution of the explosion shock wave generated by the short-circuit arc on the explosion-proof device, the maximum stress value of the shell and the average stress value of the shell are obtained.

Preferably, the maximum stress value at the apex of the folding angle can be changed by selecting the most suitable folding line deflection angle α.

Preferably, the stress on the shell of the explosion-proof device of the 220kV metal type high-voltage cable joint is related to the impact force of the airflow, and a thickened flange is used at the vertex of the broken line of the shell, which can relieve the stress distribution inside the shell.

Preferably, the deflection angle of the broken line at different end parts and the thickness h and height L of the flange connected to the protection device body are designed, and the optimal deflection angle of the broken line and the flange thickness and height are obtained through simulation calculation.

Preferably, the deflection angle of the broken line of the end structure of the explosion-proof device of the 220kV metal type high-voltage cable joint is determined to be 60°, the thickness of the connecting flange at the vertex of the broken line is determined to be 20mm, the height is 50mm, and the stress distortion coefficient k in the cavity is reduced to 1.48.

The present invention has the following beneficial effects:

The broken-line structure of the end portion of the 220kV metal type high-voltage cable joint protection device of the present invention can make the stress distortion coefficient of the inner wall of the protection device from the initial 4.72 by comparing the initial and optimizing the broken-line end portion and the arc-shaped end structure. When it dropped to 1.48, it is considered that the optimized zigzag end has a lower stress distortion coefficient and better explosion-proof performance; under the same technical conditions, the optimized zigzag end structure has better economic benefits.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the accompanying drawings.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

Fig. 1 is the coupling action form diagram between multi-physics fields of the preferred embodiment of the present invention;

2 is a simulation model diagram of a high-voltage cable joint protection device according to a preferred embodiment of the present invention;

Fig. 3 is the structure diagram of the broken-line end portion of the high-voltage cable joint protection device according to the preferred embodiment of the present invention;

4 is a schematic diagram of stress distribution of a three-dimensional protection device according to a preferred embodiment of the present invention;

Figure 5 is a physical diagram of the protection device of the preferred embodiment of the present invention;

FIG. 6 is a process diagram of air pressure change at the upper cover plate of the energy release hole of the explosion-proof device according to the preferred embodiment of the present invention;

Fig. 7 is the relationship curve between the deflection angle of the broken line and the maximum stress value of the end portion of the explosion-proof device according to the preferred embodiment of the present invention;

Fig. 8 is the stress characteristic value of the lower end portion of different flange structures according to the preferred embodiment of the present invention;

Fig. 9 is the structure diagram of the zigzag-shaped terminal of the preferred embodiment of the present invention;

Fig. 10 is the schematic diagram before explosion of the high-voltage cable joint protection device of the preferred embodiment of the present invention;

Fig. 11 is the installation schematic diagram and the physical diagram of the strain rosette of the preferred embodiment of the present invention;

FIG. 12 is a typical strain waveform diagram of the test process and test measurement of the preferred embodiment of the present invention;

FIG. 13 is a structural diagram of a curved end head according to a preferred embodiment of the present invention;

Detailed ways

The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

Referring to Figure 1, the core of the explosion caused by the short-circuit arc of the cable joint is the result of the interaction of the temperature field, the fluid field and the stress field. Due to the temperature increase caused by the arc explosion, the gas expands and impacts the explosion-proof casing. The stress is generated on the shell, and the interaction between the coupling between the multiphysics in the cable joint simulation is summarized by analysis.

Referring to Figure 2, taking the explosion-proof device of the 220kV metal type high-voltage cable joint as the main application object, the design method of the broken line at the end part is given. According to the relevant literature at home and abroad and the geometric parameters of each part of the 220kV XLPE insulated high-voltage AC cable accessories in the project, referring to the prototypes of accessories produced by domestic accessory manufacturers and the electric field strength of the materials, a two-dimensional model was established in the COMSOL Multiphysics simulation software according to the ratio of 1:1. Axisymmetric simulation model. The metal type explosion-proof device is made of 5 series aluminum-magnesium alloy material. The length of the explosion-proof device is 2200mm, the inner wall thickness is 460mm, and the wall thickness is 8mm. In the previous research and simulation, the equivalent heat loss of the high-current arc generated by the insulation breakdown of the 220kV high-voltage cable joint was obtained. Therefore, the arc generated by the insulation breakdown of the 220kV high-voltage cable joint is equivalent to a radius of 4.4mm, which is located at the center of the axis. For the heat source sphere, the selected arc energy heat loss density is 7×10 ¹⁵ W/m ³ . Since the present invention studies the stress distribution at the end portion, the energy leakage hole on the shell is omitted when the model is built, and a two-dimensional axisymmetric model is established.

Referring to Figures 3 and 4, the most obvious position of stress distortion on the inner wall of the explosion-proof casing is the connection between the end of the protection device and the body, that is, the connection point M. The maximum stress value PM also appears at the connection point M, and the maximum stress value PM reaches 33296 N/m ² . Through simulation calculation, the average stress value P _avg of the explosion-proof casing is similar to the stress value at the point N in Fig. 4. Therefore, it is considered that the stress value at the end point near the cable outlet can reflect the stress value of the explosion-proof casing. The average stress value, the average stress value P _avg , was 7051 N/m ² . The ratio of the maximum stress value _{PM to the average stress value P avg of} the casing is defined as the distortion coefficient k of the stress, and the stress distortion coefficient k=4.72 of the explosion-proof casing can be obtained. In order to reduce the stress distortion coefficient, it is necessary to carry out the optimal design of the broken-line structure.

1. The broken line design of the end part of the explosion-proof shell of the 220kV cable joint

1.1 The optimal design method of the end structure of the broken-line explosion-proof shell

Based on the analysis of the structural characteristics of the explosion-proof device for 220kV high-voltage cable joints and the stress variation characteristics of the shell, a broken-line design that optimizes the stress distribution at the end is proposed for the problem of stress concentration at the corner of the broken-line structure of the end. The design points and design methods are as follows:

(1) The deflection angle α of the broken line at the end of the explosion-proof device.

By selecting different broken line angles α, according to the finite element simulation method of multi-physics coupling, it is concluded that under the same arc energy, the stress distribution of the inner wall of the end of the explosion-proof device is obtained, and the maximum stress value is extracted; the deflection is obtained through data processing. The relationship curve between the angle and the maximum stress value at the end of the explosion-proof shell; the optimal deflection angle α is obtained by combining the stress distribution results of the shell and the requirements of actual conditions.

(2) The thickness h and width L of the flange at the connection point M between the end of the explosion-proof device and the intermediate casing.

The use of thickened flanges at the connection point M can effectively alleviate the stress concentration there. Because the explosion-proof device adopts a segmented structure, under the actual structure, the body flange and the end flange at the connection point M are connected by bolts. Under the condition of ensuring sufficient bolt connection strength, the two flanges can be regarded as a whole in the simulation.

According to the structure of the connecting flange, by designing different flange thicknesses h and widths L, the simulations are carried out respectively; Flange construction for the most balanced stress distribution.

At present, metal type explosion-proof devices are equipped with energy relief holes and corresponding opening methods. Taking the double-sided opening type explosion-proof device as an example, the project team designed a spring tensioned energy relief hole, as shown in Figure 5.

The cover plate of the vent hole is tensioned by the spring, which plays the role of waterproofing and reducing explosive splashes. When a short-circuit arc occurs, when the internal pressure of the protection device reaches a certain level, the cover plate of the spring tensioned energy relief hole is punched open, and the energy relief hole begins to discharge energy, reducing the internal pressure of the device. Through the simulation calculation, after the short-circuit arc of the cable joint occurs, the gas pressure at the upper cover plate of the cavity energy discharge hole changes with time as shown in Figure 6. It can be seen from Figure 6 that when t=40ms, the cover plate of the spring tensioned energy relief hole of the protection device is punched open, the energy relief hole begins to discharge energy, and the internal pressure of the device drops rapidly. That is, until the energy relief hole is punched open, the gas pressure in the casing reaches the maximum. In order to leave a certain margin, the time that the casing is kept sealed is set to 70ms, that is, the stress value on the casing of the protection device when the simulation time point is t=70ms is taken as the basis for the device design.

1.2 Determination of deflection angle α at the end of explosion-proof device

By selecting different polyline deflection angles α, and no flange is added at the connection point M, according to the finite element simulation method of multi-physics field coupling, the stress distribution of the inner wall of the end of the explosion-proof device under the same arc energy is calculated, and Extract its maximum stress value. It can be seen from the simulation results that the maximum stress occurs at the connection point M. The relationship curve between the deflection angle α of different broken lines and the maximum stress value at the end of the explosion-proof device (the stress value at the connection point M) is obtained by simulation, as shown in Figure 7. It can be seen from FIG. 7 that when the deflection angle α of the broken line at the end of the explosion-proof device is larger, the maximum stress value P is smaller. (1) When the deflection angle α of the broken line is less than 60°, the maximum stress P decreases with the increase of α, and the decline rate is obvious; (2) When the deflection angle α of the broken line is greater than 60°, with the increase of α, the maximum stress P decreases. With the continuous increase, the maximum stress P also decreases, but the decrease rate is slow.

According to the simulation results, when the deflection angles α are 55°, 60° and 65° respectively, the maximum stress values at the tip are 31948N/m ² , 24584N/m ² and 23776N/m ² , respectively. It can be seen that when the deflection angle α is 55°, the maximum stress value decreases by 23% when the deflection angle α is 60°, and the maximum stress value only decreases by 25.6% when the deflection angle α is 65°. It shows that when the deflection angle α of the broken line is greater than 60°, the effect of increasing α on improving the stress distribution will be extremely insignificant.

On the other hand, from the perspective of the actual application conditions and manufacturing costs of high-voltage cable joints, the end parts should not be designed to be too long. The larger the deflection angle α of the broken line, the longer the length of the end portion needs to be. Therefore, by comprehensively considering the practicability, safety and economy of the protection device, the bending angle α of the broken line at the end portion is finally selected to be 60°.

1.3 Structural design of the connection flange between the end and the body

In practical applications, when the wall thickness of the explosion-proof device of 220kV cable joint is 8mm, the thickness h of the connecting flange is usually between 15-20mm, and the width L is usually between 40-50mm. In order to achieve the optimal effect of reducing the shell stress, five groups of typical flange sizes are selected for calculation in the simulation, namely flange 1 (L=40mm, h=15mm), flange 2 (L=42.5mm, h =16.25mm), flange 3 (L=45mm, h=17.5mm), flange 4 (L=47.5mm, h=18.75mm) and flange 5 (L=50mm, h=20mm).

When t=70ms, according to the simulation method proposed in this paper, when the deflection angle α of the broken line is 60°, the maximum stress value P _M and the average stress value P of the shell corresponding to flanges of different sizes are obtained. _avg is shown in Figure 8. It can be seen from Figure 8 that the larger the flange size, the smaller the maximum stress PM at the end of the explosion-proof device, while the average stress value of the shell is basically unchanged. The ratio of the maximum stress value PM to the shell average stress value Pavg is defined as the distortion coefficient k of the stress, and the corresponding k values for flanges of different sizes are shown in Table 1.

Table 1 Stress characteristic values corresponding to flanges of different sizes

From Table 1, when flange 5 (L=50mm, h=20mm) is selected, the distortion coefficient k=1.48 of stress is the minimum value. Therefore, the final selection of flange thickness h=20mm, flange width L=50mm.

1.4 Optimum structure of broken-line end of 220kV high-voltage cable joint explosion-proof device

Through the deflection angle of the folded line and the design of the flange, the optimized structure of the folded-line end of the explosion-proof device of the 220kV high-voltage cable joint is finally determined, as shown in Figure 9.

The end structure finally adopted is that the deflection angle of the broken line is 60°, and the connecting flange at the vertex of the broken line adopts a thickness of 20mm and a height of 50mm. The stress distortion coefficient k in the cavity is reduced to 1.48.

2 Explosion stress test of 220kV metal type high-voltage cable joint protection device folding line terminal design

2.1 Test device and test method

In order to check whether the optimal design of the broken line shape of the 220kV high-voltage cable joint protection device is reasonable, the processing is carried out according to the structure of the end part designed in Figure 9. The 220kV high-voltage cable joint protection device is made of 5-series aluminum-magnesium alloy material, and the protection device has a built-in 220kV cable with a cross-section of 2500mm2 and a complete set of cable joint devices. The layout of the test site is shown in Figure 10. The pressure distribution test at the end, using explosive blasting to measure the impact stress on the shell. The test was carried out in the field test site of Jiangsu Xuyi 925 Factory. The test explosion source is 100g of bulk 8701 explosive. In the test, strain rosettes were used to measure the dynamic strain of the protective device under the action of explosion, and the piezoelectric shock wave pressure sensor was used to measure the shock wave pressure generated by the explosion. Figure 11 shows the schematic diagram of the installation of strain rosettes and the actual installation diagram. Point 1 is the maximum stress distribution position of the shell, and point 2 is the average stress distribution position of the shell.

2.2 Test process and results

The main phenomena observed in the blasting test of the high-voltage cable protection device are: under the action of 100g8701 explosive, the protection device can discharge energy normally, and the shell is not damaged after the explosion shock wave. The test process captured by the high-speed camera and the typical strain waveform measured by the test are shown in Figure 12. In general, the strain rosette can measure the strain in three directions of the stress-tested part. Therefore, the measured stress results of the explosion impact of 100g8701 explosive on points 1 and 2 on the shell and the calculated stress distortion coefficient k are shown in Table 2.

Table 2 Typical point strain test results of the end

Measurement point Axial strain (P_a) Hoop strain (P_a) 45° oblique direction (P_a) 1 3502.33 11271.65 466.71 2 2350.56 7773.55 317.49 Distortion coefficient k 1.49 1.45 1.47

It can be seen from the data in Table 2 that after adopting the broken-line terminal structure designed by the present invention, the stress distortion coefficient obtained by the test is basically consistent with the simulation result. It is proved that the present invention is reliable for the optimized fold-line design of the end portion of the 220kV high-voltage cable joint protection device.

3 Comparison of technical and economic benefits

3.1 Techno-economic comparison of the optimized zigzag end and the original zigzag end

According to the initial design of the 220kV high-voltage cable joint protection device (deflection angle α is 45°, L at the connecting flange is 40mm, h is 15mm), as obtained in Section 1.1, the stress distortion coefficient of the shell is 4.72. The optimized end design of the 220kV high-voltage cable joint protection device (deflection angle α is 60°, L at the connecting flange is 50mm, h is 20mm), and the stress distortion coefficient of the shell is 1.48. It can be seen that the explosion-proof performance of the technically optimized end design has been significantly improved.

In terms of economy, the length of the contracted part of the end part of the initial structure is 76mm shorter than the optimized one, which is 2600mm relative to the length of the body of the 220kV high-voltage cable joint protection device (the distance between the end flanges on both sides, this design is 2600mm) ) is very small; the dimensions of the connecting flanges vary slightly. It can be seen that the end structure of the initial structure does not have a great advantage in economic cost, but the optimized end structure has significantly improved the explosion-proof performance. Therefore, the optimized terminal structure has obvious comprehensive technical and economic advantages.

3.2 Technological and economical comparison of optimized polyline and radian end structures

Compared with the folded-line design, the arc-shaped design at the end of the protective device lies in the design of a circular arc at the connection point M. According to the document "Optimized Design of the End Structure of High-voltage Cable Joint Explosion-Proof Device Based on Multi-Physical Field Coupling", the radian end structure is shown in Figure 13. If the connection point M is designed as a radian structure, the key lies in Determines the optimal radius of curvature in radians. At this time, the end flange and the body flange are directly butted together, and there is no angle problem, so there is no stress distortion problem at the flange connection. It is found by calculation that when the radius of curvature is greater than 0.3m, the maximum stress value of the inner wall of the cavity decreases to a very small degree. Therefore, the radius of curvature of the end part is taken as 0.3m.

For further comparison and analysis, according to the models and parameters shown in the above literature, the maximum stress value, average stress value and stress distortion coefficient k of the inner wall of the protection device cavity under different arc curvature radii were calculated. The calculation results are shown in Table 2. .

Table 3 Stress characteristic values corresponding to arcs with different curvature radii

It can be seen from the data in Table 2 that when the arc structure with a curvature radius of 0.3 m is adopted at the connection point M, the stress distortion coefficient k of the inner wall of the cavity is reduced to 1.42. Continue to increase the radius of curvature, the decrease of the distortion coefficient k is not obvious.

Comparing the data in Table 1 and Table 3, it can be seen that the maximum stress value, average stress value and stress distortion coefficient of the inner wall of the cavity are similar to the optimized broken-line structure, and the same effect is achieved technically.

However, comparing the structure of the broken-line type end head and the arc type end head structure shown in Figure 9 and Figure 13, (1) in the same protective device body, end shrinkage diameter (200mm) and end wall thickness (8mm) ), the length of the broken-line end is 225.17mm, the length of the arc-shaped end is 338.95mm, and the arc-shaped end is 50.53% longer than the broken-line end, which increases the amount of material; (2) The end portion is designed to be arc-shaped It will obviously increase the difficulty and cost of processing. Therefore, from the analysis of economic benefits, the broken-line terminal designed in this paper has better economic benefits.

To sum up, the present invention selects the folded line deflection angle α of the end portion to be 60° through the folded-line end structure, and adds a flange (L=50mm, h=20mm) at the connection between the end and the shell, which can protect the The stress distortion coefficient of the inner wall of the device is reduced to 1.48, which effectively reduces the stress on the shell. The stress change at the end portion during the blasting process is measured and designed through the blasting test. The test results show that the optimal design of the broken-line end is accurate and reliable. By comparing the initial and optimized polyline-shaped end structure and the radian-shaped end structure, it is considered that the optimized polyline-shaped end part has a lower stress distortion coefficient and better explosion-proof performance. Under the same technical conditions, the optimized polyline-shaped end The structure has better economic benefits.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. a 220kV metal type high-voltage cable joint explosion-proof device end portion of the broken line structure design, is characterized in that, comprises: When the 220kV metal type high-voltage cable joint fails, the energy released by the short-circuit arc acts on the explosion-proof casing through the airflow, and generates stress on the casing. The position where the maximum stress value and the most obvious stress distortion appear on the inner wall of the explosion-proof casing is the protection device. The connection between the end and the body, that is, at the apex of the corner. In the explosion-proof device for 220kV high-voltage cable joints, the folded-line structure with a specific deflection angle is optimally selected for the end part, and the flange connection with optimized size is adopted at the connection between the end and the body (at the apex of the folded angle), so that the The degree of stress distortion at the vertex is alleviated. 2. The degree of stress distortion at the end portion of the explosion-proof device of 220kV metal type high-voltage cable joint according to claim 1, it is characterized in that, described adopting finite element software, establishes the simulation of explosion process of 220kV metal type high-voltage cable joint explosion-proof device The model, through the principle of thermal-fluid-stress multi-physical field coupling, calculates the impact stress generated by the explosion shock wave generated by the short-circuit arc on the explosion-proof device, and obtains the ratio of the maximum stress value of the shell to the average stress value of the shell, which is called is the stress distortion coefficient. 3. The zigzag structure of the end portion of the explosion-proof device of a 220kV metal type high-voltage cable joint according to claim 1, characterized in that, the size of the stress on the shell is divided by the airflow impact force and the shell material and local thickness In addition, designing a reasonable deflection angle of the broken line at the end part can play a role in balancing the internal stress distribution of the shell. 4. The design of the bending angle design of the folded line structure of the end portion of the explosion-proof device of the 220kV metal type high-voltage cable joint according to claim 3 is characterized in that, the described can be selected according to different folded line angles α, according to the multi-physics field. The coupled finite element simulation method, under the same arc energy, obtains the inner wall stress distribution at the end of the explosion-proof device, and extracts its maximum stress value; through data processing, the deflection angle and the maximum stress value at the end of the explosion-proof shell are obtained. Relationship lines. Combined with economic and practical indicators, the optimal deflection angle α is selected. 5. The optimized design of the connecting flange of the zigzag structure at the end of the explosion-proof device of the 220kV metal type high-voltage cable joint according to claim 1, characterized in that, the flange structure can be set by setting different flange thickness h and width L, and simulate respectively; obtain the maximum stress value at the connection between the protection device end and the body and the average stress value of the inner wall of the end part, and select the optimal flange thickness and width with the minimum stress distortion coefficient as the index . 6. The zigzag structure of the end portion of the explosion-proof device of a 220kV metal type high-voltage cable joint according to claims 4 and 5, wherein the fold line deflection angle of the end structure is 60°, and the apex of the fold line is connected to the thickness of the flange It is 20mm and the height is 50mm, which can reduce the stress distortion coefficient in the cavity to 1.48.

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