Electret electric stress dispersion high-voltage heat-shrinkable cable accessory and preparation method

Abstract

This invention relates to the field of cable accessory technology, and more particularly to an electret-type high-voltage heat-shrinkable cable accessory for dissipating electrical stress and its manufacturing method. The method includes obtaining the actual electric field strength at the stress cone interface to determine whether the initial stress cone thickness range needs adjustment; for cases where adjustment of the initial stress cone thickness range is not required, verifying the adaptability of the thickness range by simulating the maximum electric field strength; after successful verification, detecting the surface temperature data of the stress cone under stable power transmission conditions and adjusting the local thickness according to the temperature growth rate; if verification fails, detecting abnormal temperature fluctuation values ​​under fluctuating power transmission conditions and adjusting the adjustment value of the stress cone thickness range according to the abnormal temperature fluctuation values, wherein the initial thickness range is set based on the historical highest power transmission. This invention precisely adjusts the stress cone thickness used in wind power generation by considering the ratio of abnormal change areas, the number of abnormal change regions, and the temperature growth rate.

Description

Technical Field

[0001] This invention relates to the field of cable accessories technology, and in particular to an electret-type high-voltage heat-shrinkable cable accessory for dissipating electrical stress and its preparation method. Background Technology

[0002] High-voltage cable accessories are critical components in power transmission systems, primarily used for connecting cable terminals and intermediate joints. Their performance directly impacts the safety and stability of the power system. Traditional heat-shrinkable cable accessories still have shortcomings in areas such as electric field stress control, partial discharge suppression, high-temperature resistance, and aging resistance. Especially in harsh environments such as high humidity, strong electric fields, and mechanical vibration, they are prone to insulation degradation and exacerbated partial discharge. Cable accessories typically use multi-layer solid dielectrics to restore the cable's insulation structure, which makes them susceptible to interface defects and creates weak points during cable operation. In power generation utilizing 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 cases, whether the cable accessories, especially the stress cones at the cable connections, can withstand the safety hazards posed by the current instability of the transmission line is a pressing issue. In recent years, power outages caused by cable accessories have frequently occurred, attracting significant attention from the power industry and society at large. To address the problem of partial discharge at weak points in cable accessory insulation, leading to insulation failure, special electric field stress control structures are incorporated into the cable accessories to limit concentrated electric field stress.

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

[0004] It is evident that the existing technology has the following problems: during wind power generation, the current changes significantly with the wind speed, making it impossible to accurately adjust the overall thickness of the stress cone based on the ratio of abnormal change areas, the number of abnormal change regions, and the rate of temperature increase. Summary of the Invention

[0005] To address this issue, the present invention provides an electret-type high-voltage heat-shrinkable cable accessory and its preparation method, which overcomes the problem in the prior art where the current changes significantly with wind speed during wind power generation, making it impossible to precisely adjust the overall thickness of the stress cone according to the ratio of abnormal change areas, the number of abnormal change regions, and the rate of temperature increase.

[0006] To achieve the above objectives, the present invention provides a method for preparing electret-type high-voltage heat-shrinkable cable accessories, comprising the following steps:

[0007] Obtain the actual electric field strength at the interface under the operating environment of the stress cone, and determine whether to adjust the preset initial stress cone thickness range based on the actual electric field strength;

[0008] In response to not changing the preset 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 variation requirements;

[0009] Obtain the verification results and obtain the state that meets the requirements of electric field intensity change based on the verification results. Detect the actual temperature data set of several detection points on the outer surface of the stress cone under stable power transmission state. Analyze the temperature growth rate of the actual temperature data set and determine whether to adjust the thickness of the stress cone corresponding to each detection point based on the temperature growth rate.

[0010] For situations that do not meet the requirements for electric field strength changes, the temperature data of the outer surface of the stress cone under fluctuating power transmission is detected to obtain abnormal temperature data, and the thickness adjustment value is determined based on the abnormal temperature fluctuation value of the abnormal temperature data.

[0011] The initial stress cone thickness range is determined based on the highest historical transmission power value; the stable transmission state is a transmission state in which both the actual electric field strength of the stress cone and the temperature fluctuation amplitude of the outer surface of the stress cone are less than the preset fluctuation amplitude; the fluctuating transmission state is a transmission state in which both the electric field strength and the temperature fluctuation amplitude of the outer surface of the stress cone are greater than the preset fluctuation amplitude; and the thickness adjustment value is a phased adjustment value of the actual electric field strength on the initial stress cone thickness range.

[0012] Furthermore, the process of obtaining the actual electric field strength at the interface under the operating environment of the stress cone includes,

[0013] Several field strength sensors are set along the axial direction of the cable where the stress cone is located. The distribution density of the field strength sensors is determined according to the electric field strength level of the corresponding historical period. The electric field strength level includes the initial electric field strength level, the intermediate electric field strength level, and the high-level electric field strength level.

[0014] Furthermore, the process of determining whether to adjust the preset initial stress cone thickness range based on the actual electric field strength includes,

[0015] The thickness of the first stress cone is obtained based on the actual electric field strength. The thickness of the first stress cone is compared with the initial stress cone thickness range to obtain the first stress cone thickness comparison result. Based on the first stress cone thickness comparison result, it is determined whether to adjust the initial stress cone thickness range.

[0016] Furthermore, the process of detecting the actual temperature data set of several detection points on the outer surface of the stress cone under stable power transmission conditions includes,

[0017] The actual temperature data set is fitted according to the location of each set detection point to obtain a three-dimensional spatial temperature distribution map. The three-dimensional spatial temperature distribution map is then converted into a two-dimensional spatial temperature distribution map and divided into several regions. The temperature changes of each region are compared, and an abnormal region is selected in which the temperature difference between any region and the temperature of the adjacent region is greater than the preset standard temperature difference. The temperature growth rate of the abnormal region is then detected.

[0018] The standard temperature difference is a threshold value set based on the thermal stability of the material.

[0019] Furthermore, the process of determining whether to adjust the thickness of the stress cone corresponding to each detection point based on the temperature increase rate includes,

[0020] The detection temperature growth rate of each detection point in the abnormal two-dimensional spatial temperature distribution map is detected. The detection temperature growth rate is compared with the standard temperature growth rate range to obtain the first temperature growth rate comparison result. Based on the first temperature growth rate comparison result, it is determined whether to adjust the stress cone thickness corresponding to the detection point.

[0021] The abnormal two-dimensional spatial temperature distribution map refers to the spatial region where the temperature growth rate is abnormal within the two-dimensional spatial temperature distribution map.

[0022] Furthermore, the process of determining whether to adjust the thickness of the stress cone corresponding to the detection point based on the comparison result of the first temperature increase rate includes,

[0023] For cases where the temperature increase rate is within the standard temperature increase rate range, the original stress cone thickness is maintained.

[0024] If the detected temperature increase rate is less than the minimum value of the standard temperature increase rate range, the stress cone thickness is reduced based on the difference between the minimum value of the standard temperature increase rate range and the detected temperature increase rate.

[0025] For cases where the detected temperature increase rate is greater than the maximum value of the standard temperature increase rate range, the stress cone thickness is increased based on the difference between the maximum value of the standard temperature increase rate range and the detected temperature increase rate.

[0026] Furthermore, the process of obtaining abnormal temperature data by detecting the temperature data of the outer surface of the stress cone under fluctuating power transmission conditions includes,

[0027] The abnormal temperature change area is determined by an infrared detection device, and the abnormal change area ratio and the number of abnormal change areas are recorded. Based on the abnormal change area ratio and the number of abnormal change areas, it is determined whether the abnormal temperature fluctuation value of the outer surface of the stress cone under the fluctuating power transmission state is normal.

[0028] Wherein, 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; the number of abnormal change regions is the number of abnormal temperature change regions.

[0029] Furthermore, the process of determining whether the abnormal temperature fluctuation value on the outer surface of the stress cone under fluctuating power transmission conditions is normal based on the ratio of abnormal change areas and the number of abnormal change regions includes,

[0030] For cases where the abnormal area ratio is within the standard area ratio range, the abnormal temperature fluctuation value is judged to be normal based on the comparison between the number of abnormal areas and the number of standard ranges.

[0031] If the abnormal change area ratio is less than the minimum value of the standard change area ratio range, the abnormal temperature fluctuation value is determined to be normal, and the original thickness adjustment value is maintained.

[0032] When the abnormal change area ratio is greater than the maximum value of the standard change area ratio range, there is no need to compare the number of abnormal change areas with the number of standard change ranges to determine that the abnormal temperature fluctuation value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio range and the abnormal change area ratio.

[0033] Furthermore, the process of determining whether abnormal temperature fluctuation values ​​are normal based on the comparison between the number of abnormal change areas and the number of standard change intervals includes:

[0034] By 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, the abnormal temperature fluctuation value is determined to be normal, and no adjustment of the thickness adjustment value is required. The process of determining whether the abnormal temperature fluctuation value is normal based on the comparison result of the number of abnormal change areas and the number of standard change intervals includes...

[0035] 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, the abnormal temperature fluctuation value is considered normal and no adjustment of the thickness adjustment value is required.

[0036] Compare 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, adjust the thickness adjustment value according to the difference between the number of abnormal change areas and the number of standard change intervals.

[0037] The present invention also provides an electret-type high-voltage heat-shrinkable cable accessory for electrical stress relief, comprising,

[0038] A silicone rubber stress cone, wherein the silicone rubber stress cone is interference-fitted with the cable;

[0039] The silicone rubber stress cone is covered with a protective composite umbrella skirt.

[0040] Compared with existing technologies, the beneficial effects of this invention are that by detecting and adjusting the thickness of the stress cone, its stable performance under various electric field strengths can be ensured, thereby effectively preventing transmission accidents caused by excessively high electric field strength or temperature. Adjusting the stress cone thickness according to actual electric field strength and temperature data makes the stress cone more suitable for actual operating requirements, avoiding increased operating costs due to excessively thick or thin stress cones, and improving the economy and practicality of the stress cone. By reasonably adjusting the stress cone thickness, thermal and electrical stresses during operation can be reduced, thereby slowing down the aging rate and extending the service life. The optimized stress cone can better adapt to different transmission conditions, reduce energy loss, and improve transmission efficiency.

[0041] Furthermore, for cases 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 fluctuating power transmission conditions is detected to obtain abnormal temperature data. By comparing the results, it is determined whether to reduce the thickness of the stress cone to increase its heat dissipation capacity or to increase the thickness of the stress cone to avoid the stress cone being too thin and thus being broken down.

[0042] Furthermore, by adjusting the thickness of the corresponding stress cone under stable power transmission conditions by comparing the detected temperature increase rate with the standard temperature increase rate range, the thickness of the stress cone can be adjusted more precisely to meet the requirements of the stress cone in actual use. If the detected temperature increase rate is less than the minimum value of the standard temperature increase rate range, the reduced stress cone thickness is determined by multiplying the initial stress cone thickness by the product of the difference between the minimum value of the standard temperature increase rate range and the detected temperature increase rate (1 minus the thickness) and the minimum value of the standard temperature increase rate range. This allows the reduced stress cone thickness to accelerate the heat dissipation rate when the current changes. If the detected temperature increase rate is greater than the maximum value of the standard temperature increase rate range, the increased stress cone thickness is determined by multiplying the initial stress cone thickness by the product of the difference between the detected temperature increase rate and the maximum value of the standard temperature increase rate range (1 plus the thickness) and the maximum value of the standard temperature increase rate range. This increases the thickness at the corresponding stress cone position to prevent the stress cone from being broken down due to excessive local electric field. It can better select the areas of stress cones that do not conform to the changes in electric field strength of the cable and adjust their thickness separately, which increases the rationality of the overall and local thickness of the stress cone. It can also adjust the overall thickness of the stress cone to improve the uniformity of the distribution of electric field strength on the surface of the stress cone, making the gradient design of the stress cone thickness more in line with the actual application scenarios of the cable.

[0043] Furthermore, for areas with abnormal temperature changes, the determination of whether to adjust the thickness adjustment value to adjust the initial stress cone thickness range is made by detecting the ratio of abnormal change areas and the number of abnormal change areas. This can meet the adjustment of the initial stress cone thickness range under different conditions. Specifically, setting the influence weight of the ratio of abnormal change areas 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 adjusting the initial stress cone thickness range and replacing the stress cone due to abnormal temperature fluctuations in individual areas, thus reducing transmission efficiency. When the ratio of abnormal change areas is greater than the maximum value of the standard change area ratio range, there is no need to compare the number of abnormal change areas with the number of standard change ranges to determine that the abnormal temperature fluctuation value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio range and the ratio of abnormal change areas. In this case, the judgment is based on the situation that the initial stress cone thickness cannot meet the requirements of the transmission line over a large area. Therefore, it is not necessary to determine the number of abnormal change areas, reducing the judgment time, increasing the speed of stress cone replacement, and increasing transmission efficiency. By comparing the number of abnormal variation areas with the number of standard variation intervals, if the number of abnormal variation areas is less than or equal to the number of standard variation intervals, the abnormal temperature fluctuation is considered normal, and no adjustment of the thickness adjustment value is required. If the number of abnormal variation areas exceeds the number of standard variation intervals, the thickness adjustment value is adjusted based on the difference between these two values. Adjusting the thickness based on this difference allows for more precise adjustment of the stress cone thickness, resulting in a more uniform electric field distribution and reducing the risk of stress cone breakdown. Attached Figure Description

[0044] Figure 1 This is a flowchart of the method for preparing electret-type electrical stress relief high-voltage heat-shrinkable cable accessories in the embodiments;

[0045] Figure 2 This is a flowchart illustrating the stress cone thickness comparison process in the preparation method of electret-type electrical stress relief high-voltage heat-shrinkable cable accessories in the embodiments.

[0046] Figure 3 This is a flowchart illustrating the process of adjusting the thickness of the stress cone in the preparation method of the electret-type electric stress relief high-voltage heat-shrinkable cable accessory in the embodiment.

[0047] Figure 4 This is a flowchart illustrating the process of adjusting the thickness adjustment value in the preparation method of the electret-type electric stress relief high-voltage heat-shrinkable cable accessory in the embodiment.

[0048] Figure 5 This is a schematic diagram of the electret-type high-voltage heat-shrinkable cable accessory used in the embodiment. Detailed Implementation

[0049] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0050] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0051] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate 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 is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0052] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] Please see Figures 1-4 As shown, Figure 1 This is a flowchart of the method for preparing electret-type electrical stress relief high-voltage heat-shrinkable cable accessories in the embodiments; Figure 2 This is a flowchart illustrating the stress cone thickness comparison process in the preparation method of electret-type electrical stress relief high-voltage heat-shrinkable cable accessories in the embodiments. Figure 3 This is a flowchart illustrating the process of adjusting the thickness of the stress cone in the preparation method of the electret-type electric stress relief high-voltage heat-shrinkable cable accessory in the embodiment. Figure 4 This is a flowchart illustrating the process of adjusting the thickness adjustment value in the preparation method of the electret-type electric stress relief high-voltage heat-shrinkable cable accessory in the embodiment.

[0054] This embodiment provides a method for preparing electret-type high-voltage heat-shrinkable cable accessories with electrical stress relief, including the following steps:

[0055] Step S1: Obtain the actual electric field strength at the interface under the operating environment of the stress cone, and determine whether to adjust the preset initial stress cone thickness range based on the actual electric field strength.

[0056] Step S2: In response to not changing the preset initial stress cone thickness range, simulate applying the maximum theoretical electric field strength to verify whether the initial stress cone thickness range meets the electric field strength change requirements;

[0057] Step S3: Obtain the verification results and obtain the state that meets the requirements of electric field strength change based on the verification results. Detect the actual temperature data set of several detection points on the outer surface of the stress cone under stable power transmission state, analyze the temperature growth rate of the actual temperature data set, and determine whether to adjust the thickness of the stress cone corresponding to each detection point based on the temperature growth rate.

[0058] Step S4: For cases that do not meet the requirements for electric field strength change, detect the temperature data of the outer surface of the stress cone under fluctuating power transmission state to obtain abnormal temperature data, and determine whether to adjust the thickness adjustment value based on the abnormal temperature fluctuation value of the abnormal temperature data.

[0059] The initial stress cone thickness range is determined based on the highest historical transmission power value; the stable transmission state is a transmission state in which both the actual electric field strength of the stress cone and the temperature fluctuation amplitude of the outer surface of the stress cone are less than the preset fluctuation amplitude; the fluctuating transmission state is a transmission state in which both the electric field strength and the temperature fluctuation amplitude of the outer surface of the stress cone are greater than the preset fluctuation amplitude; and the thickness adjustment value is a phased adjustment value of the actual electric field strength on the initial stress cone thickness range.

[0060] By detecting and adjusting the thickness of the stress cone, stable performance can be ensured under various electric field strengths, effectively preventing transmission accidents caused by excessively high electric field strength or temperature. Adjusting the stress cone thickness based on actual electric field strength and temperature data makes the stress cone more suitable for actual operating requirements, avoiding increased operating costs due to excessively thick or thin stress cones, and improving the economy and practicality of the stress cone. Reasonable adjustment of the stress cone thickness can reduce thermal and electrical stresses during operation, thereby slowing down aging and extending service life. Optimized stress cones can better adapt to different transmission conditions, reducing energy loss and improving transmission efficiency.

[0061] Specifically, the process of obtaining the actual electric field strength at the interface under the operating environment of the stress cone includes,

[0062] Several field strength sensors are set along the axial direction of the cable where the stress cone is located. The distribution density of the field strength sensors is determined according to the electric field strength level of the corresponding historical period. The electric field strength level includes the initial electric field strength level, the intermediate electric field strength level, and the high-level electric field strength level.

[0063] Specifically, the process of determining whether to adjust the preset initial stress cone thickness range based on the actual electric field strength includes,

[0064] The thickness of the first stress cone is obtained based on the actual electric field strength. The thickness of the first stress cone is compared with the initial stress cone thickness range to obtain the first stress cone thickness comparison result. Based on the first stress cone thickness comparison result, it is determined whether to adjust the initial stress cone thickness range.

[0065] In step S1, historical data shows that the electric field strength of the 110kV cable during normal operation ranges from 2.0 to 3.5 kV / mm. In this embodiment, it is set to be the initial electric field strength level.

[0066] According to the grade standard, the field strength sensor distribution density is set to one sensor every 50 mm, for a total of 10 sensors, covering a stress cone length of 500 mm.

[0067] 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 field strength sensor distribution density has been increased to one sensor every 30mm, for a total of 15 sensors, covering a length of 450mm.

[0068] Flexible DC cables exhibit high-frequency voltage oscillations, with electric field strength reaching 8.0-12.0 kV / mm, which is classified as a high-level electric field strength. The field strength sensor distribution density is set to one sensor every 10 mm, for a total of 60 sensors, covering a length of 600 mm.

[0069] The thickness of the first stress cone is determined by supplementing parameters based on the actual electric field strength and its influence on the thickness of the first stress cone. The thickness of the first stress cone is directly proportional to the actual electric field strength, and the parameter for the direct proportionality between the thickness of the first stress cone and the actual electric field strength is determined based on a preset direct proportionality constant.

[0070] For cases where the first stress cone thickness comparison result is within the range of the initial stress cone thickness, the maximum theoretical electric field intensity is simulated to verify whether the range of the initial stress cone thickness meets the requirements of electric field intensity variation.

[0071] If the first stress cone thickness comparison result is that the first stress cone thickness is not within the range of the initial stress cone thickness, the temperature data of the outer surface of the stress cone under fluctuating power transmission state is detected to obtain abnormal temperature data.

[0072] If 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 fluctuating power transmission is detected to obtain abnormal temperature data. By comparing the results, it is determined whether to reduce the thickness of the stress cone to increase its heat dissipation capacity or to increase the thickness of the stress cone to avoid the stress cone being too thin and thus being broken down.

[0073] Specifically, the process of detecting the actual temperature data set of several detection points on the outer surface of the stress cone under stable power transmission conditions includes,

[0074] The actual temperature data set is fitted according to the location of each set detection point to obtain a three-dimensional spatial temperature distribution map. The three-dimensional spatial temperature distribution map is then converted into a two-dimensional spatial temperature distribution map and divided into several regions. The temperature changes of each region are compared, and an abnormal region is selected in which the temperature difference between any region and the temperature of the adjacent region is greater than the preset standard temperature difference. The temperature growth rate of the abnormal region is then detected.

[0075] The standard temperature difference is a threshold value set based on the thermal stability of the material.

[0076] Specifically, the process of determining whether to adjust the thickness of the stress cone corresponding to each detection point based on the temperature increase rate includes,

[0077] The detection temperature growth rate of each detection point in the abnormal two-dimensional spatial temperature distribution map is detected. The detection temperature growth rate is compared with the standard temperature growth rate range to obtain the first temperature growth rate comparison result. Based on the first temperature growth rate comparison result, it is determined whether to adjust the stress cone thickness corresponding to the detection point.

[0078] The abnormal two-dimensional spatial temperature distribution map refers to the spatial region where the temperature growth rate is abnormal within the two-dimensional spatial temperature distribution map.

[0079] Based on the corresponding field strength sensor distribution density, several infrared thermal imagers are installed at corresponding positions on the outer surface of the stress cone to detect the temperature data at the corresponding positions. The temperature data at the detected positions are fitted with the temperature data at the corresponding detection positions to obtain a two-dimensional spatial temperature distribution map. An abnormal region is selected where the temperature difference between a single region and the temperature of adjacent regions is greater than a preset standard temperature difference, and the temperature growth rate of the abnormal region is detected.

[0080] Specifically, the process of determining whether to adjust the stress cone thickness corresponding to the detection point based on the comparison result of the first temperature increase rate includes,

[0081] For cases where the temperature increase rate is within the standard temperature increase rate range, the original stress cone thickness is maintained.

[0082] If the detected temperature increase rate is less than the minimum value of the standard temperature increase rate range, the stress cone thickness is reduced based on the difference between the minimum value of the standard temperature increase rate range and the detected temperature increase rate.

[0083] For cases where the detected temperature increase rate is greater than the maximum value of the standard temperature increase rate range, the stress cone thickness is increased based on the difference between the maximum value of the standard temperature increase rate range and the detected temperature increase rate.

[0084] If the detected temperature increase rate is less than the minimum value of the standard temperature increase rate range, the reduced stress cone thickness is determined by dividing the difference between the initial stress cone thickness and the minimum value of the standard temperature increase rate range for thickness reduction by the minimum value of the standard temperature increase rate range for thickness by the product of the initial stress cone thickness and the detected temperature increase rate.

[0085] If the detected temperature increase rate is greater than the maximum value of the standard temperature increase rate range, the increased stress cone thickness is determined by the product of the initial stress cone thickness and the difference between the detected temperature increase rate and the maximum value of the standard temperature increase rate range, divided by the maximum value of the standard temperature increase rate range.

[0086] If the detected temperature increase rate is within the standard temperature increase rate range, then there is no need to adjust the stress cone thickness corresponding to the detection point.

[0087] The standard temperature difference is set at 5℃.

[0088] For example:

[0089] 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.

[0090] If the temperature increase rate is 0.12℃ / min, then the reduced stress cone thickness is 5×[1-(0.15-0.12) / 0.15]=4.0mm;

[0091] If the temperature increase rate is 0.35℃ / min, then the increased stress cone thickness is 5×[1+(0.35-0.3) / 0.30]≈5.83mm.

[0092] By adjusting the thickness of the corresponding stress cone under stable power transmission conditions by comparing the detected temperature increase rate with the standard temperature increase rate range, the thickness of the stress cone can be more precisely adjusted to meet the requirements of the stress cone in actual use. If the detected temperature increase rate is less than the minimum value of the standard temperature increase rate range, the reduced stress cone thickness is determined by multiplying the initial stress cone thickness by the product of the difference between the minimum value of the standard temperature increase rate range and the detected temperature increase rate, and the minimum value of the standard temperature increase rate range. This allows the stress cone to reduce its thickness and accelerate the heat dissipation rate when the current changes. If the detected temperature increase rate is greater than the maximum value of the standard temperature increase rate range, the increased stress cone thickness is determined by multiplying the initial stress cone thickness by the product of the difference between the detected temperature increase rate and the maximum value of the standard temperature increase rate range, and the maximum value of the standard temperature increase rate range. This increases the thickness at the corresponding stress cone position to prevent the stress cone from being broken down due to excessive local electric field. It can better select the areas of stress cones that do not conform to the changes in electric field strength of the cable and adjust their thickness separately, which increases the rationality of the overall and local thickness of the stress cone. It can also adjust the overall thickness of the stress cone to improve the uniformity of the distribution of electric field strength on the surface of the stress cone, making the gradient design of the stress cone thickness more in line with the actual application scenarios of the cable.

[0093] Specifically, the process of detecting the temperature data of the outer surface of the stress cone under fluctuating power transmission conditions to obtain abnormal temperature data includes,

[0094] The abnormal temperature change area is determined by an infrared detection device, and the abnormal change area ratio and the number of abnormal change areas are recorded. Based on the abnormal change area ratio and the number of abnormal change areas, it is determined whether the abnormal temperature fluctuation value of the outer surface of the stress cone under the fluctuating power transmission state is normal.

[0095] Wherein, 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; the number of abnormal change regions is the number of abnormal temperature change regions.

[0096] Specifically, the process of determining whether the abnormal temperature fluctuation value on the outer surface of the stress cone under fluctuating power transmission conditions is normal based on the ratio of abnormal change areas and the number of abnormal change regions includes,

[0097] For cases where the abnormal area ratio is within the standard area ratio range, the abnormal temperature fluctuation value is judged to be normal based on the comparison between the number of abnormal areas and the number of standard ranges.

[0098] If the abnormal change area ratio is less than the minimum value of the standard change area ratio range, the abnormal temperature fluctuation value is determined to be normal, and the original thickness adjustment value is maintained.

[0099] When the abnormal change area ratio is greater than the maximum value of the standard change area ratio range, there is no need to compare the number of abnormal change areas with the number of standard change ranges to determine that the abnormal temperature fluctuation value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio range and the abnormal change area ratio.

[0100] Specifically, the process of determining whether abnormal temperature fluctuation values ​​are normal based on the comparison between the number of abnormal change areas and the number of standard change intervals includes:

[0101] 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, the abnormal temperature fluctuation value is considered normal and no adjustment of the thickness adjustment value is required.

[0102] Compare 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, adjust the thickness adjustment value according to the difference between the number of abnormal change areas and the number of standard change intervals.

[0103] In this embodiment, the standard variation area ratio range is set to [10%, 15%], the number of standard variation ranges is 3, the compensation parameter for the difference between the number of abnormal variation areas and the number of standard variation ranges 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.

[0104] For example:

[0105] When the abnormal change area ratio is 12% and the number of abnormal change areas is 2, the abnormal temperature fluctuation value is determined to be normal and no adjustment of the thickness adjustment value is required.

[0106] When the abnormal change area ratio is 12% and the number of abnormal change areas is 4, the thickness adjustment value is adjusted by adding the product of the difference between the number of abnormal change areas and the number of standard change intervals and the effect 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. Then 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 [4.5 + 3.4, 4.8 + 3.4] mm. The final adjusted initial stress cone thickness range is [7.9, 8.2] mm.

[0107] When the abnormal change area ratio is 8%, the abnormal temperature fluctuation value is determined to be normal, and there is no need to adjust the thickness adjustment value.

[0108] When the abnormal change area ratio is 18%, the abnormal temperature fluctuation value is determined to be abnormal. The thickness adjustment value is adjusted according to the product of the initial adjustment value and 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. Then 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 [4.5+3.6, 4.8+3.6]mm. The final adjusted initial stress cone thickness range is [8.1, 8.4]mm.

[0109] For areas with abnormal temperature changes, the decision to adjust the initial stress cone thickness range is made by detecting the ratio and number of abnormal change areas. This approach can meet the adjustment needs of the initial stress cone thickness range under different circumstances. Specifically, setting the weight of the ratio of abnormal change areas on the adjustment value of the initial stress cone thickness range greater than the weight of the number of abnormal change areas avoids wasting time and reducing transmission efficiency by adjusting the initial stress cone thickness range and replacing the stress cone simply because of abnormal temperature fluctuations in individual areas. When the ratio of abnormal change areas is greater than the maximum value of the standard ratio of change areas, there is no need to compare the number of abnormal change areas with the number of standard change intervals to determine that the abnormal temperature fluctuation is abnormal. The thickness adjustment value is adjusted based on the difference between the maximum value of the standard ratio of change areas and the ratio of abnormal change areas. In this case, the initial stress cone thickness is deemed insufficient for the transmission line over a large area, thus eliminating the need to determine the number of abnormal change areas, reducing determination time, increasing the speed of stress cone replacement, and improving transmission efficiency. By comparing the number of abnormal variation areas with the number of standard variation intervals, if the number of abnormal variation areas is less than or equal to the number of standard variation intervals, the abnormal temperature fluctuation is considered normal, and no adjustment of the thickness adjustment value is required. If the number of abnormal variation areas exceeds the number of standard variation intervals, the thickness adjustment value is adjusted based on the difference between these two values. Adjusting the thickness based on this difference allows for more precise adjustment of the stress cone thickness, resulting in a more uniform electric field distribution and reducing the risk of stress cone breakdown.

[0110] Please see Figure 5 As shown, it is a structural schematic diagram of the electret-type high-voltage heat-shrinkable 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 environment of use; 5 is the stress cone gradient formed by adjusting the thickness area of ​​the corresponding stress cone according to the temperature growth rate of the detected single area temperature; 6 is the silicone rubber stress cone with a protective composite umbrella skirt.

[0111] This embodiment also provides an electret-type high-voltage heat-shrinkable cable accessory for electrical stress relief, including,

[0112] A silicone rubber stress cone, wherein the silicone rubber stress cone is interference-fitted with the cable;

[0113] The silicone rubber stress cone is covered with a protective composite umbrella skirt.

[0114] The technical solution of the present invention has been described above with reference to 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 can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing electret-type high-voltage heat-shrinkable cable accessories, characterized in that, Includes the following steps, Obtain the actual electric field strength at the interface under the operating environment of the stress cone, and determine whether to adjust the 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, the maximum theoretical electric field strength is simulated to verify whether the initial stress cone thickness range meets the electric field strength variation requirements; Obtain the verification results and obtain the state that meets the requirements of electric field intensity change based on the verification results. Detect the actual temperature data set of several detection points on the outer surface of the stress cone under stable power transmission state. Analyze the temperature growth rate of the actual temperature data set and determine whether to adjust the thickness of the stress cone corresponding to each detection point based on the temperature growth rate. For situations that do not meet the requirements for electric field strength changes, the temperature data of the outer surface of the stress cone under fluctuating power transmission is detected to obtain abnormal temperature data, and the thickness adjustment value is determined based on the abnormal temperature fluctuation value of the abnormal temperature data. The initial stress cone thickness range is determined based on the highest historical transmission power value; the stable transmission state is a transmission state in which both the actual electric field strength of the stress cone and the temperature fluctuation amplitude of the outer surface of the stress cone are less than the preset fluctuation amplitude; the fluctuating transmission state is a transmission state in which both the electric field strength and the temperature fluctuation amplitude of the outer surface of the stress cone are greater than the preset fluctuation amplitude; and the thickness adjustment value is a phased adjustment value of the actual electric field strength on the initial stress cone thickness range.

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

3. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 2, characterized in that, The process of determining whether to adjust the preset initial stress cone thickness range based on the actual electric field strength includes, The thickness of the first stress cone is obtained based on the actual electric field strength. The thickness of the first stress cone is compared with the initial stress cone thickness range to obtain the first stress cone thickness comparison result. Based on the first stress cone thickness comparison result, it is determined whether to adjust the initial stress cone thickness range.

4. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 3, characterized in that, The process of collecting actual temperature data at several detection points on the outer surface of the stress cone under stable power transmission conditions includes: The actual temperature data set is fitted according to the location of each set detection point to obtain a three-dimensional spatial temperature distribution map. The three-dimensional spatial temperature distribution map is then converted into a two-dimensional spatial temperature distribution map and divided into several regions. The temperature changes of each region are compared, and an abnormal region is selected in which the temperature difference between any region and the temperature of the adjacent region is greater than the preset standard temperature difference. The temperature growth rate of the abnormal region is then detected. The standard temperature difference is a threshold value set based on the thermal stability of the material.

5. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 4, characterized in that, The process of determining whether to adjust the thickness of the stress cone corresponding to each detection point based on the temperature increase rate includes... The detection temperature growth rate of each detection point in the abnormal two-dimensional spatial temperature distribution map is detected. The detection temperature growth rate is compared with the standard temperature growth rate range to obtain the first temperature growth rate comparison result. Based on the first temperature growth rate comparison result, it is determined whether to adjust the stress cone thickness corresponding to the detection point. The abnormal two-dimensional spatial temperature distribution map refers to the spatial region where the temperature growth rate is abnormal within the two-dimensional spatial temperature distribution map.

6. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 5, characterized in that, The process of determining whether to adjust the thickness of the stress cone corresponding to the detection point based on the comparison result of the first temperature increase rate includes... For cases where the temperature increase rate is within the standard temperature increase rate range, the original stress cone thickness is maintained. If the detected temperature increase rate is less than the minimum value of the standard temperature increase rate range, the stress cone thickness is reduced based on the difference between the minimum value of the standard temperature increase rate range and the detected temperature increase rate. For cases where the detected temperature increase rate is greater than the maximum value of the standard temperature increase rate range, the stress cone thickness is increased based on the difference between the maximum value of the standard temperature increase rate range and the detected temperature increase rate.

7. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 6, characterized in that, The process of obtaining abnormal temperature data by detecting the temperature data of the outer surface of the stress cone under fluctuating power transmission conditions includes the following steps: The abnormal temperature change area is determined by an infrared detection device, and the abnormal change area ratio and the number of abnormal change areas are recorded. Based on the abnormal change area ratio and the number of abnormal change areas, it is determined whether the abnormal temperature fluctuation value of the outer surface of the stress cone under the fluctuating power transmission state is normal. Wherein, 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; the number of abnormal change regions is the number of abnormal temperature change regions.

8. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 7, characterized in that, The process of determining whether the abnormal temperature fluctuation value on the outer surface of the stress cone under fluctuating power transmission conditions is normal based on the ratio of abnormal change areas and the number of abnormal change regions includes: For cases where the abnormal area ratio is within the standard area ratio range, the abnormal temperature fluctuation value is judged to be normal based on the comparison between the number of abnormal areas and the number of standard ranges. If the abnormal change area ratio is less than the minimum value of the standard change area ratio range, the abnormal temperature fluctuation value is determined to be normal, and the original thickness adjustment value is maintained. When the abnormal change area ratio is greater than the maximum value of the standard change area ratio range, there is no need to compare the number of abnormal change areas with the number of standard change ranges to determine that the abnormal temperature fluctuation value is abnormal. The thickness adjustment value is adjusted according to the difference between the maximum value of the standard change area ratio range and the abnormal change area ratio.

9. The method for preparing electret-type high-voltage heat-shrinkable cable accessories according to claim 8, characterized in that, The process of determining whether abnormal temperature fluctuation values ​​are normal based on the comparison between the number of abnormal change areas and the number of standard change intervals includes: By 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, the abnormal temperature fluctuation value is determined to be normal, and no adjustment of the thickness adjustment value is required. The process of determining whether the abnormal temperature fluctuation 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, the abnormal temperature fluctuation value is considered normal and no adjustment of the thickness adjustment value is required. Compare 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, adjust the thickness adjustment value according to the difference between the number of abnormal change areas and the number of standard change intervals.

10. An electret-type high-voltage heat-shrinkable cable accessory for electrical stress relief, based on the method for preparing an electret-type high-voltage heat-shrinkable cable accessory according to any one of claims 1-9, characterized in that, include, A silicone rubber stress cone, wherein the silicone rubber stress cone is interference-fitted with the cable; The silicone rubber stress cone is covered with a protective composite umbrella skirt.

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