Electret type electric stress evacuation high-voltage thermal shrinkage cable accessory and preparation method thereof

Abstract

The invention relates to the technical field of cable accessories, in particular to an electret electric stress evacuation high-voltage thermal shrinkage cable accessory and a preparation method. The method includes: acquiring actual electric field intensity at a stress cone interface, and accordingly judging whether an initial stress cone thickness range needs to be adjusted; for the condition that the thickness range of the initial stress cone does not need to be adjusted, verifying the adaptability of the thickness range by simulating the maximum electric field intensity; after verification is passed, stress cone surface temperature data in a stable power transmission state are detected, and the local thickness is adjusted according to the temperature increasing rate; when verification is not passed, the temperature fluctuation abnormal value of the abnormal temperature data of the fluctuating power transmission state is detected, the adjustment value of the thickness range of the stress cone is adjusted according to the temperature fluctuation abnormal value, and the initial thickness range is set based on the historical maximum power transmission power. According to the method, the thickness of the stress cone applied to wind power generation is accurately adjusted through the abnormal change area ratio, the number of abnormal change areas and the temperature increasing rate.

Description

Technical Field

[0001] The present invention relates to the technical field of cable accessories, and in particular to an electret electric stress evacuation high-voltage heat shrink cable accessory and a preparation method thereof. Background Art

[0002] High-voltage cable accessories are critical components in power transmission systems, primarily used for connecting cable terminals and intermediate connectors. Their performance directly impacts the safety and stability of power systems. Traditional heat-shrink cable accessories still have shortcomings in terms of electric field stress control, partial discharge suppression, high temperature resistance, and aging resistance. In particular, they are prone to insulation degradation and increased partial discharge in harsh environments such as high humidity, strong electric fields, and mechanical vibration. Cable accessories typically utilize multiple layers of solid dielectric to restore the cable's insulation structure, which can lead to interface defects and become a weak link in cable operation. In the process of generating electricity from natural resources, such as wind power, severe weather and strong winds can sometimes affect the voltage and current during power generation and transmission. In such situations, the ability of cable accessories, particularly the stress cones at cable connections, to withstand the safety hazards posed by current instability in the transmission line, is an urgent issue. In recent years, frequent power outages caused by cable accessories have garnered significant attention from the power industry and society at large. To address the problem of partial discharge at weak points in the insulation of cable accessories, which can lead to insulation failure, cable accessories incorporate specialized electric field stress control structures to limit concentrated electric field stress.

[0003] Chinese Patent Publication No.: CN113035449A discloses a method for preparing a stress cone and a nonlinear composite material for a cable accessory. The nonlinear composite material is used to prepare the stress cone of the cable accessory. Nonlinear inorganic fillers with different filler contents, namely, ethylene propylene rubber / silicon carbide / diisopropylbenzene peroxide composite materials, are made into a wrapped tape. The internal conductivity nonlinear parameters of the tape are different, and the gradient distribution is used to suppress the conductivity loss and ensure the effective regulation of the electrical stress. The method provided in this application solves the problem that traditional cable accessories using nonlinear resistance materials generate heat in situations with heavy harmonics and are prone to electrical breakdown when external overvoltage occurs.

[0004] It can be seen that the existing technology has the following problems: since the current will be significantly affected by changes in wind speed during wind power generation, the overall thickness of the stress cone cannot be accurately adjusted according to the abnormal change area ratio, the number of abnormal change areas and the temperature growth rate. Summary of the Invention

[0005] To this end, the present invention provides an electret electric stress evacuation high-voltage heat shrink cable accessory and a preparation method, which is used to overcome the problem in the prior art that during wind power generation, the current will be significantly affected by changes in wind speed, resulting in the inability to accurately adjust the overall thickness of the stress cone according to the abnormal change area ratio, the number of abnormal change areas and the temperature growth rate.

[0006] To achieve the above object, the present invention provides a method for preparing an electret type electric stress evacuation high-voltage heat shrink cable accessory, comprising the following steps: Acquiring an actual electric field strength at the interface under the stress cone use environment, and determining whether to adjust a preset initial stress cone thickness range based on the actual electric field strength; In response to not changing the preset initial stress cone thickness range, simulating applying a maximum theoretical electric field strength to verify whether the initial stress cone thickness range meets the electric field strength change requirement; Obtaining verification results and obtaining a state that meets the electric field intensity change requirement based on the verification results, detecting actual temperature data sets at multiple detection points on the outer surface of the stress cone under a stable power transmission state, analyzing the temperature growth rate of the actual temperature data sets, and determining whether to adjust the stress cone thickness corresponding to each detection point based on the temperature growth rate; For situations that do not meet the requirements of electric field intensity change, the temperature data of the outer surface of the stress cone under the fluctuating power transmission state is detected to obtain abnormal temperature data, and whether to adjust the thickness adjustment value is determined according to the temperature fluctuation abnormal value of the abnormal temperature data; Among them, the initial stress cone thickness range is determined according to the highest historical power transmission power; the stable power transmission state is a power transmission state in which the actual electric field strength of the stress cone and the temperature fluctuation amplitude of the outer surface of the stress cone are both less than the preset fluctuation amplitude; the fluctuating power transmission state is a power transmission state in which the electric field strength and the temperature fluctuation amplitude of the outer surface of the stress cone are both greater than the preset fluctuation amplitude, and the thickness adjustment value is a stage-by-stage adjustment value of the actual electric field strength to the initial stress cone thickness range.

[0007] Furthermore, the process of obtaining the actual electric field strength at the interface under the stress cone use environment includes: Several field strength sensors are set in the axial direction of the cable where the stress cone is located, and the distribution density of the field strength sensors is determined according to the electric field strength level of the corresponding historical period, wherein the electric field strength level includes the initial electric field strength level, the intermediate electric field strength level and the advanced electric field strength level.

[0008] Furthermore, the process of determining whether to adjust the preset initial stress cone thickness range according to the actual electric field strength includes: A first stress cone thickness of the corresponding stress cone is obtained according to the actual electric field strength, and a first stress cone thickness comparison result is obtained by comparing the first stress cone thickness with the initial stress cone thickness range. It is determined whether to adjust the initial stress cone thickness range according to the first stress cone thickness comparison result.

[0009] Furthermore, the process of detecting the actual temperature data set of a plurality of detection points on the outer surface of the stress cone under a steady power transmission state includes: Fitting the actual temperature data set according to the positions of the set detection points to obtain a three-dimensional spatial temperature distribution map, converting the three-dimensional spatial temperature distribution map into a two-dimensional spatial temperature distribution map and dividing it into several regions, comparing the temperature changes in each region, selecting abnormal regions where the difference between the temperature of any region and the temperature of the adjacent region is greater than a preset standard temperature difference, and detecting the temperature growth rate of the abnormal region; The standard temperature difference is a threshold value set according to the thermal stability of the material.

[0010] Furthermore, the process of determining whether to adjust the stress cone thickness corresponding to each detection point according to the temperature growth rate includes: detecting a detected temperature growth rate corresponding to each detection point in a temperature distribution diagram of an abnormal two-dimensional spatial region, comparing the detected temperature growth rate with a standard temperature growth rate interval to obtain a first temperature growth rate comparison result, and determining whether to adjust a stress cone thickness corresponding to the corresponding detection point based on the first temperature growth rate comparison result; The abnormal two-dimensional spatial region temperature distribution diagram is a spatial region in which the temperature growth rate shows abnormality within the two-dimensional spatial temperature distribution diagram.

[0011] Furthermore, the process of determining whether to adjust the stress cone thickness corresponding to the corresponding detection point according to the first temperature growth rate comparison result includes: When the test temperature growth rate is within the standard temperature growth rate range, the original stress cone thickness is maintained; When the detection temperature growth rate is less than the minimum value of the standard temperature growth rate interval, the stress cone thickness is reduced according to the difference between the minimum value of the standard temperature growth rate interval and the detection temperature growth rate; When the detection temperature growth rate is greater than the maximum value of the standard temperature growth rate interval, the stress cone thickness is increased according to the difference between the maximum value of the standard temperature growth rate interval and the detection temperature growth rate.

[0012] Furthermore, the process of detecting the temperature data of the outer surface of the stress cone under the fluctuating power transmission state to obtain abnormal temperature data includes: determining abnormal temperature change areas by an infrared detection device, recording the abnormal temperature change area ratio and the number of abnormal temperature change areas, and determining whether the temperature fluctuation abnormal value of the outer surface of the stress cone under the fluctuating power transmission state is normal based on the abnormal temperature change area ratio and the number of abnormal temperature change areas; The abnormal change area ratio is the ratio of the area of ​​the temperature change region to the area of ​​the outer surface of the stress cone; and the number of abnormal change regions is the number of abnormal temperature change regions.

[0013] Furthermore, the process of determining whether the temperature fluctuation abnormal value of the outer surface of the stress cone under the fluctuating power transmission state is normal based on the abnormal change area ratio and the number of abnormal change regions includes: For the case where the abnormal change area ratio is within the standard change area ratio range, the comparison result of the number of abnormal change areas and the number of standard change ranges is used to determine whether the temperature fluctuation abnormal value is normal; If the abnormal change area ratio is less than the minimum value of the standard change area ratio, the temperature fluctuation abnormal value is determined to be normal and the original thickness adjustment value is maintained; For the case where the abnormal change area ratio is greater than the maximum value of the standard change area ratio interval, there is no need to compare the number of abnormal change areas and the number of standard change intervals to determine that the temperature fluctuation abnormal value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio interval and the abnormal change area ratio.

[0014] Furthermore, the process of judging whether the temperature fluctuation abnormal value is normal based on the comparison result of the number of abnormal change areas and the number of standard change intervals includes: Comparing the number of abnormal change areas with the number of standard change intervals, if the number of abnormal change areas is less than the number of standard change intervals, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value. The process of judging whether the temperature fluctuation abnormal value is normal based on the comparison result of the number of abnormal change areas and the number of standard change intervals includes: Compare the number of abnormal change areas with the number of standard change intervals. If the number of abnormal change areas is less than or equal to the number of standard change intervals, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value. The number of abnormal change areas is compared with the number of standard change intervals. If the number of abnormal change areas is greater than the number of standard change intervals, the thickness adjustment value is adjusted according to the difference between the number of abnormal change areas and the number of standard change intervals.

[0015] The present invention also provides an electret type electric stress evacuation high-voltage heat shrink cable accessory, comprising: A silicone rubber stress cone having an interference fit with the cable; The outer cover of the silicone rubber stress cone is provided with a protective composite umbrella skirt.

[0016] Compared with the prior art, the beneficial effect of the present invention is that, by detecting and adjusting the thickness of the stress cone, it can ensure that it maintains stable performance under various electric field strengths, thereby effectively preventing power transmission accidents caused by excessive electric field strength or excessive temperature. Adjusting the stress cone thickness according to the actual electric field strength and temperature data can make the stress cone more consistent with actual operating requirements, avoid the increase in operating costs caused by the stress cone being too thick or too thin, and improve the economy and practicality of the stress cone. By reasonably adjusting the thickness of the stress cone, its thermal stress and electrical stress during operation can be reduced, thereby reducing the aging rate and extending the service life. The optimized stress cone can better adapt to different transmission states, reduce energy loss, and improve transmission efficiency.

[0017] Furthermore, in the case where the thickness of the first stress cone is not within the range of the initial stress cone thickness, the temperature data of the outer surface of the stress cone under the fluctuating power transmission state is detected to obtain abnormal temperature data. By comparing the results, it is determined whether the thickness of the stress cone should be reduced to increase the heat dissipation capacity of the stress cone or to increase the thickness of the stress cone to avoid the stress cone being too thin and causing breakdown.

[0018] Furthermore, by adjusting the thickness of the corresponding stress cone by comparing the detected temperature growth rate with the standard temperature growth rate interval under a stable power transmission state, the stress cone thickness can be more finely adjusted to meet the requirements of the stress cone in actual use. If the detected temperature growth rate is less than the minimum value of the standard temperature growth rate interval, the reduced stress cone thickness is determined based on the initial stress cone thickness and the product of the difference between the minimum value of the standard temperature growth rate interval (1 minus the thickness) and the detected temperature growth rate divided by the minimum value of the standard temperature growth rate interval. This can reduce the thickness of the stress cone to accelerate the heat dissipation rate when the current changes. If the detected temperature growth rate is greater than the maximum value of the standard temperature growth rate interval, the increased stress cone thickness is determined based on the product of the initial stress cone thickness and the difference between the maximum value of the standard temperature growth rate interval (1 plus the detected temperature growth rate) and the standard temperature growth rate interval divided by the maximum value of the standard temperature growth rate interval. This can increase the thickness of the corresponding stress cone position to avoid the stress cone being punctured due to excessive local electric field in the stress cone. It is possible to better select the area of ​​the stress cone that does not conform to the change of the cable electric field strength and adjust its stress cone thickness separately, thereby increasing the rationality of the overall thickness and local thickness of the stress cone. It is also possible to adjust the overall thickness of the stress cone for the purpose of uniform distribution of the electric field strength on the surface of the stress cone so that the gradient design of the stress cone thickness is more in line with the actual application scenarios of the actual cable.

[0019] Furthermore, for abnormal temperature change areas, by detecting the abnormal change area ratio and the number of abnormal change areas, it is determined whether to adjust the thickness adjustment value to adjust the initial stress cone thickness range, which can meet the adjustment of the initial stress cone thickness range in different situations. Among them, setting the influence weight of the abnormal change area ratio on the adjustment value of the initial stress cone thickness range to be greater than the influence weight of the number of abnormal change areas on the adjustment value of the initial stress cone thickness range can avoid the waste of time caused by replacing the stress cone due to abnormal temperature fluctuations in individual areas, thereby reducing transmission efficiency. For the case where the abnormal change area ratio is greater than the maximum value of the standard change area ratio interval, there is no need to compare the number of abnormal change areas with the number of standard change intervals to determine that the temperature fluctuation abnormality value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio interval and the abnormal change area ratio. In this case, it is determined that the initial stress cone thickness cannot meet the transmission line requirements based on a large area, so there is no need to determine the number of abnormal change areas, thereby reducing determination time, increasing the speed of replacing stress cones, and improving transmission efficiency. Comparing the number of abnormal change areas with the number of standard change intervals, if the number of abnormal change areas is less than or equal to the number of standard change intervals, the temperature fluctuation abnormality is determined to be normal and no adjustment of the thickness adjustment value is required. Comparing the number of abnormal change areas with the number of standard change intervals, if the number of abnormal change areas is greater than the number of standard change intervals, the thickness adjustment value is adjusted based on the difference between the number of abnormal change areas and the number of standard change intervals. When the number of abnormal change areas is greater than the number of standard change intervals, adjusting the thickness adjustment value based on the difference between the number of abnormal change areas and the number of standard change intervals can more accurately adjust the thickness of the stress cone, making the electric field strength distribution more uniform and reducing the risk of stress cone breakdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flowchart of a method for preparing an electret type electrical stress relief high voltage heat shrink cable accessory in an embodiment; Figure 2 A flowchart showing a stress cone thickness comparison process of a method for preparing an electret type electric stress relief high-voltage heat shrinkable cable accessory in an embodiment; Figure 3 A flowchart of the process of adjusting the thickness of the stress cone in the method for preparing the electret type electric stress relief high-voltage heat shrink cable accessory in the embodiment; Figure 4 A process flow chart of adjusting the thickness adjustment value of the method for preparing the electret type electric stress relief high-voltage heat shrinkable cable accessory in the embodiment; Figure 5 Schematic diagram of the structure of the electret type electric stress relief high-voltage heat shrink cable accessory in the embodiment. DETAILED DESCRIPTION

[0021] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0022] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0024] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0025] See also Figure 1-Figure 4 As shown, Figure 1 Flowchart of a method for preparing an electret type electrical stress relief high voltage heat shrink cable accessory in an embodiment; Figure 2 A flowchart showing a stress cone thickness comparison process of a method for preparing an electret type electric stress relief high-voltage heat shrinkable cable accessory in an embodiment; Figure 3 A flowchart of the process of adjusting the thickness of the stress cone in the method for preparing the electret type electric stress relief high-voltage heat shrink cable accessory in the embodiment; Figure 4 This is a process flow chart of adjusting the thickness adjustment value of the method for preparing the electret electric stress relief high-voltage heat shrink cable accessory in the embodiment.

[0026] This embodiment provides a method for preparing an electret type electric stress relief high-voltage heat shrink cable accessory, comprising the following steps: Step S1, obtaining the actual electric field strength at the interface under the stress cone use environment, and determining whether to adjust the preset initial stress cone thickness range according to the actual electric field strength; Step S2, in response to not changing the preset initial stress cone thickness range, simulating applying a maximum theoretical electric field strength to verify whether the initial stress cone thickness range meets the electric field strength change requirement; Step S3, obtaining a verification result and obtaining a state that meets the electric field intensity change requirement based on the verification result, detecting a set of actual temperature data at a plurality of detection points on the outer surface of the stress cone under a stable power transmission state, analyzing a temperature growth rate of the actual temperature data set, and determining whether to adjust the stress cone thickness corresponding to each detection point based on the temperature growth rate; Step S4: For a case where the electric field intensity variation requirement is not met, the temperature data of the outer surface of the stress cone under the fluctuating power transmission state is detected to obtain abnormal temperature data, and whether to adjust the thickness adjustment value is determined according to the temperature fluctuation abnormality value of the abnormal temperature data; Among them, the initial stress cone thickness range is determined according to the highest historical power transmission power; the stable power transmission state is a power transmission state in which the actual electric field strength of the stress cone and the temperature fluctuation amplitude of the outer surface of the stress cone are both less than the preset fluctuation amplitude; the fluctuating power transmission state is a power transmission state in which the electric field strength and the temperature fluctuation amplitude of the outer surface of the stress cone are both greater than the preset fluctuation amplitude, and the thickness adjustment value is a stage-by-stage adjustment value of the actual electric field strength to the initial stress cone thickness range.

[0027] By monitoring and adjusting the thickness of the stress cone, stable performance can be ensured across a wide range of electric field intensities, effectively preventing transmission accidents caused by excessive electric field strength or temperature. Adjusting the stress cone thickness based on actual electric field strength and temperature data ensures that the stress cone more closely matches actual operational requirements, avoiding the increased operating costs associated with excessively thick or thin cones and improving their cost-effectiveness and practicality. Properly adjusting the stress cone thickness can reduce thermal and electrical stresses during operation, thereby slowing aging and extending its service life. The optimized stress cone can better adapt to varying transmission conditions, reduce energy loss, and improve transmission efficiency.

[0028] Specifically, the process of obtaining the actual electric field strength at the interface under the stress cone use environment includes: Several field strength sensors are set in the axial direction of the cable where the stress cone is located, and the distribution density of the field strength sensors is determined according to the electric field strength level of the corresponding historical period, wherein the electric field strength level includes the initial electric field strength level, the intermediate electric field strength level and the advanced electric field strength level.

[0029] Specifically, the process of determining whether to adjust the preset initial stress cone thickness range according to the actual electric field strength includes: A first stress cone thickness of the corresponding stress cone is obtained according to the actual electric field strength, and a first stress cone thickness comparison result is obtained by comparing the first stress cone thickness with the initial stress cone thickness range. It is determined whether to adjust the initial stress cone thickness range according to the first stress cone thickness comparison result.

[0030] In step S1, historical data shows that the electric field strength of the 110kV cable during normal operation ranges from 2.0 to 3.5kV / mm. In this embodiment, this is assumed to be the initial electric field strength level. According to the grade standard, the field intensity sensor distribution density is set to 1 sensor every 50 mm, with a total of 10 sensors, covering a 500 mm stress cone length; The electric field strength of this 220kV DC cable reaches 4.0-6.0kV / mm when fully loaded, which is a medium electric field strength level. The distribution density of field strength sensors has been increased to one per 30mm, with a total of 15 sensors covering a length of 450mm. Flexible DC cables have high-frequency voltage oscillations, and the electric field strength can reach 8.0-12.0 kV / mm, which belongs to the advanced electric field strength level. The field strength sensor distribution density is set to 1 per 10 mm, with a total of 60 sensors, covering a length of 600 mm.

[0031] Determining the thickness of the first stress cone according to the actual electric field strength and the supplementary parameter of the influence of the actual electric field strength on the thickness of the first stress cone, wherein the thickness of the first stress cone is in direct proportion to the actual electric field strength, and the proportionality parameter of the first stress cone thickness to the actual electric field strength is determined according to a preset proportionality constant; If the comparison result of the first stress cone thickness shows that the first stress cone thickness is within the initial stress cone thickness range, the maximum theoretical electric field strength is simulated to verify whether the initial stress cone thickness range meets the electric field strength change requirement; When the comparison result of the first stress cone thickness shows that the first stress cone thickness is not within the initial stress cone thickness range, the temperature data of the outer surface of the stress cone under the fluctuating power transmission state is detected to obtain abnormal temperature data.

[0032] When the thickness of the first stress cone is not within the range of the initial stress cone thickness, the temperature data of the outer surface of the stress cone under the fluctuating power transmission state is detected to obtain abnormal temperature data. By comparing the results, it is determined whether the thickness of the stress cone should be reduced to increase the heat dissipation capacity of the stress cone or increased to avoid breakdown due to excessive thinning of the stress cone.

[0033] Specifically, the process of detecting the actual temperature data set of several detection points on the outer surface of the stress cone under a steady power transmission state includes: Fitting the actual temperature data set according to the positions of the set detection points to obtain a three-dimensional spatial temperature distribution map, converting the three-dimensional spatial temperature distribution map into a two-dimensional spatial temperature distribution map and dividing it into several regions, comparing the temperature changes in each region, selecting abnormal regions where the difference between the temperature of any region and the temperature of the adjacent region is greater than a preset standard temperature difference, and detecting the temperature growth rate of the abnormal region; The standard temperature difference is a threshold value set according to the thermal stability of the material.

[0034] Specifically, the process of determining whether to adjust the stress cone thickness corresponding to each detection point according to the temperature growth rate includes: detecting a detected temperature growth rate corresponding to each detection point in a temperature distribution diagram of an abnormal two-dimensional spatial region, comparing the detected temperature growth rate with a standard temperature growth rate interval to obtain a first temperature growth rate comparison result, and determining whether to adjust a stress cone thickness corresponding to the corresponding detection point based on the first temperature growth rate comparison result; The abnormal two-dimensional spatial region temperature distribution diagram is a spatial region in which the temperature growth rate shows abnormality within the two-dimensional spatial temperature distribution diagram.

[0035] Based on the distribution density of corresponding field strength sensors, several infrared thermal imagers are installed at corresponding positions on the outer surface of the stress cone to detect temperature data at corresponding positions. The temperature data of the detection positions and corresponding detection positions are fitted to obtain a two-dimensional spatial temperature distribution map. Abnormal areas where the difference between the temperature of a single area and the temperature of the adjacent areas is greater than the preset standard temperature difference are selected, and the temperature growth rate of the abnormal areas is detected.

[0036] Specifically, the process of determining whether to adjust the stress cone thickness corresponding to the corresponding detection point according to the first temperature growth rate comparison result includes: When the test temperature growth rate is within the standard temperature growth rate range, the original stress cone thickness is maintained; When the detection temperature growth rate is less than the minimum value of the standard temperature growth rate interval, the stress cone thickness is reduced according to the difference between the minimum value of the standard temperature growth rate interval and the detection temperature growth rate; When the detection temperature growth rate is greater than the maximum value of the standard temperature growth rate interval, the stress cone thickness is increased according to the difference between the maximum value of the standard temperature growth rate interval and the detection temperature growth rate.

[0037] If the test temperature growth rate is less than the minimum value of the standard temperature growth rate interval, the reduced stress cone thickness is determined based on the product of the initial stress cone thickness and the difference between the minimum value of the standard temperature growth rate interval minus the thickness and the test temperature growth rate, divided by the minimum value of the standard temperature growth rate interval for thickness; If the test temperature growth rate is greater than the maximum value of the standard temperature growth rate interval, the increased stress cone thickness is determined based on the initial stress cone thickness and the product of 1 plus the difference between the test temperature growth rate and the maximum value of the standard temperature growth rate interval divided by the maximum value of the standard temperature growth rate interval; If the detection temperature growth rate is within the standard temperature growth rate range, there is no need to adjust the stress cone thickness corresponding to the corresponding detection point; Among them, the standard temperature difference is set to 5°C.

[0038] For example: In this embodiment, the initial stress cone thickness is set to 5.0 mm, and the standard temperature growth rate range is [0.15, 0.30] ° C / min. The detection temperature growth rate is 0.12℃ / min, so the reduced stress cone thickness is 5×[1-(0.15-0.12) / 0.15]=4.0mm; The detection temperature growth rate is 0.35℃ / min, so the increased stress cone thickness is 5×[1+(0.35-0.3) / 0.30]≈5.83mm.

[0039] By comparing the detected temperature growth rate with the standard temperature growth rate interval under a stable power transmission state to adjust the thickness of the corresponding stress cone, the stress cone thickness can be adjusted more finely to meet the requirements of the stress cone in actual use. If the detected temperature growth rate is less than the minimum value of the standard temperature growth rate interval, the reduced stress cone thickness is determined based on the initial stress cone thickness and the product of the difference between the minimum value of the standard temperature growth rate interval (1 minus the thickness) and the detected temperature growth rate divided by the minimum value of the standard temperature growth rate interval. This can reduce the thickness of the stress cone to accelerate the heat dissipation rate when the current changes. If the detected temperature growth rate is greater than the maximum value of the standard temperature growth rate interval, the increased stress cone thickness is determined based on the product of the initial stress cone thickness and the difference between the maximum value of the standard temperature growth rate interval (1 plus the detected temperature growth rate) and the standard temperature growth rate interval divided by the maximum value of the standard temperature growth rate interval. This can increase the thickness of the corresponding stress cone position to avoid the stress cone being punctured due to excessive local electric field in the stress cone. It is possible to better select the area of ​​the stress cone that does not conform to the change of the cable electric field strength and adjust its stress cone thickness separately, thereby increasing the rationality of the overall thickness and local thickness of the stress cone. It is also possible to adjust the overall thickness of the stress cone for the purpose of uniform distribution of the electric field strength on the surface of the stress cone so that the gradient design of the stress cone thickness is more in line with the actual application scenarios of the actual cable.

[0040] Specifically, the process of detecting the temperature data of the outer surface of the stress cone under the fluctuating power transmission state to obtain abnormal temperature data includes: determining abnormal temperature change areas by an infrared detection device, recording the abnormal temperature change area ratio and the number of abnormal temperature change areas, and determining whether the temperature fluctuation abnormal value of the outer surface of the stress cone under the fluctuating power transmission state is normal based on the abnormal temperature change area ratio and the number of abnormal temperature change areas; The abnormal change area ratio is the ratio of the area of ​​the temperature change region to the area of ​​the outer surface of the stress cone; and the number of abnormal change regions is the number of abnormal temperature change regions.

[0041] Specifically, the process of determining whether the temperature fluctuation abnormal value of the outer surface of the stress cone under the fluctuating power transmission state is normal based on the abnormal change area ratio and the number of abnormal change regions includes: For the case where the abnormal change area ratio is within the standard change area ratio range, the comparison result of the number of abnormal change areas and the number of standard change ranges is used to determine whether the temperature fluctuation abnormal value is normal; If the abnormal change area ratio is less than the minimum value of the standard change area ratio, the temperature fluctuation abnormal value is determined to be normal and the original thickness adjustment value is maintained; For the case where the abnormal change area ratio is greater than the maximum value of the standard change area ratio interval, there is no need to compare the number of abnormal change areas and the number of standard change intervals to determine that the temperature fluctuation abnormal value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio interval and the abnormal change area ratio.

[0042] Specifically, the process of judging whether the temperature fluctuation abnormal value is normal based on the comparison result of the number of abnormal change areas and the number of standard change intervals includes: Compare the number of abnormal change areas with the number of standard change intervals. If the number of abnormal change areas is less than or equal to the number of standard change intervals, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value. The number of abnormal change areas is compared with the number of standard change intervals. If the number of abnormal change areas is greater than the number of standard change intervals, the thickness adjustment value is adjusted according to the difference between the number of abnormal change areas and the number of standard change intervals.

[0043] In this embodiment, the standard change area ratio interval is set to [10%, 15%], the number of standard change intervals is 3, the compensation parameter for the influence of the difference between the number of abnormal change areas and the number of standard change intervals on the thickness adjustment value is 0.4, the initial adjustment value is 3, and the initial stress cone thickness range is set to [4.5, 4.8] mm. For example: When the abnormal change area ratio is 12% and the number of abnormal change areas is 2, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value; When the abnormal change area ratio is 12% and the number of abnormal change areas is 4, the thickness adjustment value is adjusted according to the product of the initial adjustment value plus the difference between the number of abnormal change areas and the number of standard change intervals and the compensation parameter for the influence of the difference between the number of abnormal change areas and the number of standard change intervals on the thickness adjustment value. The increased thickness adjustment value is 3+(4-3)×0.4=3.4, and the adjusted initial stress cone thickness range is the initial stress cone thickness range plus the corresponding increased thickness adjustment value, that is, the adjusted initial stress cone thickness range is adjusted to [4.5+3.4, 4.8+3.4] mm, and the final adjusted initial stress cone thickness range is [7.9, 8.2] mm. When the abnormal change area ratio is 8%, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value; When the abnormal change area ratio is 18%, the temperature fluctuation abnormal value is determined to be abnormal. The thickness adjustment value is adjusted according to the initial adjustment value and the product of 1 plus the difference between the maximum value of the standard change area ratio interval and the abnormal change area ratio divided by the maximum value of the standard change area ratio interval. The increased thickness adjustment value is 3×[1+(18-15) / 15]=3.6. The adjusted initial stress cone thickness range is the initial stress cone thickness range plus the corresponding increased thickness adjustment value, that is, the adjusted initial stress cone thickness range is adjusted to [4.5+3.6, 4.8+3.6] mm. The final adjusted initial stress cone thickness range is [8.1, 8.4] mm.

[0044] For abnormal temperature change areas, the thickness adjustment value is determined to adjust the initial stress cone thickness range by detecting the abnormal change area ratio and the number of abnormal change areas, which can meet the adjustment requirements of the initial stress cone thickness range in different situations. Among them, setting the influence weight of the abnormal change area ratio on the adjustment value of the initial stress cone thickness range to be greater than the influence weight of the number of abnormal change areas on the adjustment value of the initial stress cone thickness range can avoid wasting time replacing the stress cone due to abnormal temperature fluctuations in individual areas due to adjustment of the initial stress cone thickness range, thereby reducing transmission efficiency. For the case where the abnormal change area ratio is greater than the maximum value of the standard change area ratio interval, there is no need to compare the number of abnormal change areas with the number of standard change intervals to determine that the temperature fluctuation abnormality value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio interval and the abnormal change area ratio. In this case, it is determined that the initial stress cone thickness cannot meet the transmission line requirements based on a large area, so there is no need to determine the number of abnormal change areas, thereby reducing determination time, increasing the speed of replacing stress cones, and improving transmission efficiency. Comparing the number of abnormal change areas with the number of standard change intervals, if the number of abnormal change areas is less than or equal to the number of standard change intervals, the temperature fluctuation abnormality is determined to be normal and no adjustment of the thickness adjustment value is required. Comparing the number of abnormal change areas with the number of standard change intervals, if the number of abnormal change areas is greater than the number of standard change intervals, the thickness adjustment value is adjusted based on the difference between the number of abnormal change areas and the number of standard change intervals. When the number of abnormal change areas is greater than the number of standard change intervals, adjusting the thickness adjustment value based on the difference between the number of abnormal change areas and the number of standard change intervals can more accurately adjust the thickness of the stress cone, making the electric field strength distribution more uniform and reducing the risk of stress cone breakdown.

[0045] See also Figure 5As shown, it is a structural schematic diagram of the electret electric stress evacuation high-voltage heat shrink cable accessory in the embodiment, wherein 1 is the cable; 2 is the silicone rubber stress cone; 4 is the interface of the stress cone under the use environment; 5 is the stress cone gradient formed by adjusting the corresponding stress cone thickness area according to the temperature growth rate of the temperature of a single area detected; 6 is the outer cover of the silicone rubber stress cone with a protective composite umbrella skirt.

[0046] This embodiment also provides an electret type electrical stress relief high voltage heat shrink cable accessory, comprising: A silicone rubber stress cone having an interference fit with the cable; The outer cover of the silicone rubber stress cone is provided with a protective composite umbrella skirt.

[0047] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0048] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an electret type electric stress evacuation high voltage heat shrink cable accessory, characterized in that: The following steps are included: Acquiring an actual electric field strength at the interface under the stress cone use environment, and determining whether to adjust a preset initial stress cone thickness range based on the actual electric field strength; In response to not changing the preset initial stress cone thickness range, simulating applying a maximum theoretical electric field strength to verify whether the initial stress cone thickness range meets the electric field strength change requirement; Obtaining verification results and obtaining a state that meets the electric field intensity change requirement based on the verification results, detecting actual temperature data sets at multiple detection points on the outer surface of the stress cone under a stable power transmission state, analyzing the temperature growth rate of the actual temperature data sets, and determining whether to adjust the stress cone thickness corresponding to each detection point based on the temperature growth rate; For situations that do not meet the requirements of electric field intensity change, the temperature data of the outer surface of the stress cone under the fluctuating power transmission state is detected to obtain abnormal temperature data, and whether to adjust the thickness adjustment value is determined according to the temperature fluctuation abnormal value of the abnormal temperature data; Among them, the initial stress cone thickness range is determined according to the highest historical power transmission power; the stable power transmission state is a power transmission state in which the actual electric field strength of the stress cone and the temperature fluctuation amplitude of the outer surface of the stress cone are both less than the preset fluctuation amplitude; the fluctuating power transmission state is a power transmission state in which the electric field strength and the temperature fluctuation amplitude of the outer surface of the stress cone are both greater than the preset fluctuation amplitude, and the thickness adjustment value is a stage-by-stage adjustment value of the actual electric field strength to the initial stress cone thickness range.

2. The method for preparing an electret type electric stress relief high voltage heat shrinkable cable accessory according to claim 1, characterized in that: The process of obtaining the actual electric field strength at the interface in the stress cone use environment includes: Several field strength sensors are set in the axial direction of the cable where the stress cone is located, and the distribution density of the field strength sensors is determined according to the electric field strength level of the corresponding historical period, wherein the electric field strength level includes the initial electric field strength level, the intermediate electric field strength level and the advanced electric field strength level.

3. The method for preparing an electret type electric stress relief high voltage heat shrinkable cable accessory according to claim 2, characterized in that: The process of determining whether to adjust the preset initial stress cone thickness range according to the actual electric field strength includes: A first stress cone thickness of the corresponding stress cone is obtained according to the actual electric field strength, and a first stress cone thickness comparison result is obtained by comparing the first stress cone thickness with the initial stress cone thickness range. It is determined whether to adjust the initial stress cone thickness range according to the first stress cone thickness comparison result.

4. The method for preparing an electret type electrical stress relief high voltage heat shrinkable cable accessory according to claim 3, characterized in that: The process of detecting the actual temperature data set of several detection points on the outer surface of the stress cone under the steady power transmission state includes: Fitting the actual temperature data set according to the positions of the set detection points to obtain a three-dimensional spatial temperature distribution map, converting the three-dimensional spatial temperature distribution map into a two-dimensional spatial temperature distribution map and dividing it into several regions, comparing the temperature changes in each region, selecting abnormal regions where the difference between the temperature of any region and the temperature of the adjacent region is greater than a preset standard temperature difference, and detecting the temperature growth rate of the abnormal region; The standard temperature difference is a threshold value set according to the thermal stability of the material.

5. The method for preparing an electret type electric stress relief high voltage heat shrinkable cable accessory according to claim 4, characterized in that: The process of determining whether to adjust the stress cone thickness corresponding to each detection point according to the temperature growth rate includes: detecting a detected temperature growth rate corresponding to each detection point in a temperature distribution diagram of an abnormal two-dimensional spatial region, comparing the detected temperature growth rate with a standard temperature growth rate interval to obtain a first temperature growth rate comparison result, and determining whether to adjust a stress cone thickness corresponding to the corresponding detection point based on the first temperature growth rate comparison result; The abnormal two-dimensional spatial region temperature distribution diagram is a spatial region in which the temperature growth rate shows abnormality within the two-dimensional spatial temperature distribution diagram.

6. The method for preparing an electret type electrical stress relief high voltage heat shrinkable cable accessory according to claim 5, characterized in that: The process of determining whether to adjust the stress cone thickness corresponding to the corresponding detection point according to the first temperature growth rate comparison result includes: When the test temperature growth rate is within the standard temperature growth rate range, the original stress cone thickness is maintained; When the detection temperature growth rate is less than the minimum value of the standard temperature growth rate interval, the stress cone thickness is reduced according to the difference between the minimum value of the standard temperature growth rate interval and the detection temperature growth rate; When the detection temperature growth rate is greater than the maximum value of the standard temperature growth rate interval, the stress cone thickness is increased according to the difference between the maximum value of the standard temperature growth rate interval and the detection temperature growth rate.

7. The method for preparing an electret type electrical stress relief high voltage heat shrinkable cable accessory according to claim 6, characterized in that: The process of detecting the temperature data of the outer surface of the stress cone under the fluctuating power transmission state to obtain abnormal temperature data includes: determining abnormal temperature change areas by an infrared detection device, recording the abnormal temperature change area ratio and the number of abnormal temperature change areas, and determining whether the temperature fluctuation abnormal value of the outer surface of the stress cone under the fluctuating power transmission state is normal based on the abnormal temperature change area ratio and the number of abnormal temperature change areas; The abnormal change area ratio is the ratio of the area of ​​the temperature change region to the area of ​​the outer surface of the stress cone; and the number of abnormal change regions is the number of abnormal temperature change regions.

8. The method for preparing an electret type electrical stress relief high voltage heat shrinkable cable accessory according to claim 7, characterized in that: The process of determining whether the temperature fluctuation abnormal value of the outer surface of the stress cone under the fluctuating power transmission state is normal according to the abnormal change area ratio and the number of abnormal change regions includes: For the case where the abnormal change area ratio is within the standard change area ratio range, the comparison result of the number of abnormal change areas and the number of standard change ranges is used to determine whether the temperature fluctuation abnormal value is normal; If the abnormal change area ratio is less than the minimum value of the standard change area ratio, the temperature fluctuation abnormal value is determined to be normal and the original thickness adjustment value is maintained; For the case where the abnormal change area ratio is greater than the maximum value of the standard change area ratio interval, there is no need to compare the number of abnormal change areas and the number of standard change intervals to determine that the temperature fluctuation abnormal value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio interval and the abnormal change area ratio.

9. The method for preparing an electret type electrical stress relief high voltage heat shrinkable cable accessory according to claim 8, characterized in that: The process of judging whether the temperature fluctuation abnormal value is normal based on the comparison result of the number of abnormal change areas and the number of standard change intervals includes: Comparing the number of abnormal change areas with the number of standard change intervals, if the number of abnormal change areas is less than the number of standard change intervals, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value. The process of judging whether the temperature fluctuation abnormal value is normal based on the comparison result of the number of abnormal change areas and the number of standard change intervals includes: Compare the number of abnormal change areas with the number of standard change intervals. If the number of abnormal change areas is less than or equal to the number of standard change intervals, it is determined that the temperature fluctuation abnormal value is normal and there is no need to adjust the thickness adjustment value. The number of abnormal change areas is compared with the number of standard change intervals. If the number of abnormal change areas is greater than the number of standard change intervals, the thickness adjustment value is adjusted according to the difference between the number of abnormal change areas and the number of standard change intervals.

10. An electret type electric stress relief high voltage heat shrink cable accessory, based on the method for preparing the electret type electric stress relief high voltage heat shrink cable accessory according to any one of claims 1 to 9, characterized in that: include, A silicone rubber stress cone having an interference fit with the cable; The outer cover of the silicone rubber stress cone is provided with a protective composite umbrella skirt.

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