Conductor preheating method and preheating system in a cable crosslinking process

Abstract

The application discloses a conductor preheating method and a preheating system in a cable crosslinking process, wherein the conductor preheating method in the cable crosslinking process comprises the following steps: 1) conducting first preheating before the conductor enters an extruding machine, so that the first preheating temperature T1 of the conductor after the first preheating is controlled to be 90-100 DEG C; and 2) conducting second preheating to the conductor after the conductor exits the extruding machine, setting a second preheating temperature T2, and setting the heating power y of the second preheating according to the second preheating temperature T2; the second preheating temperature T2 is controlled to be 140-170 DEG C. The application preheats the conductor twice, controls the two heating temperatures, and makes the conductor reach a preset temperature, so that the heat dissipation amount from inside to outside during extrusion is reduced, the radiation heating device in the crosslinked insulation pipeline is matched, the temperature difference in the radial direction of the cable insulation layer is reduced, the crosslinking quality is improved, the twice preheating is effective, the crosslinking efficiency is improved, and the production time is greatly saved.

Description

Technical Field

[0001] This invention relates to the field of cable manufacturing, and in particular to a conductor preheating method and preheating system in the cable cross-linking process. Background Technology

[0002] With the development of science and technology, the advent of cross-linked polyethylene (XLPE) in the 1960s accelerated the development of extruded organic polymer insulated cables. Due to its chemical cross-linked network structure, XLPE possesses excellent electrical, mechanical, and heat resistance properties, and also improves the operating temperature of low-density polyethylene. Because of these advantages, XLPE has gradually become the preferred material for the main insulation of extruded power cables and has been widely used in high-voltage power cables. With the continuous development of cross-linking processes and polyethylene base material production technology, XLPE has achieved a dominant position in the high-voltage cable field. XLPE extruded insulated high-voltage cables face many choices and challenges in engineering applications. In terms of insulation processing technology, cable insulation extrusion employs simultaneous extrusion of the conductor shielding layer, insulation layer, and insulation / shielding layer, commonly referred to as three-layer co-extrusion. Organic peroxides are used as initiators in the cross-linking process, added to the raw materials at the insulation material factory. Inside the extruder head, the raw materials are extruded and coated onto the conductor. The cross-linking reaction occurs in a high-temperature, high-pressure pipeline containing inert gas after the extruder head, i.e., the cross-linking vulcanization pipeline. The crosslinking process design is based on factors such as the extrusion rate of the extruder, the cooling level of the insulated wire core, and the temperature of the insulated wire core in the heating section of the crosslinking tube. For continuous vulcanization production systems, the high-temperature vulcanization crosslinking pipeline is very long to allow sufficient time for crosslinking to complete. However, due to the excessive length of the crosslinking pipeline, the extrusion pressure is relatively low, and the wire core temperature is relatively low. Current high-pressure vertical crosslinking vulcanization production lines suffer from long vulcanization times, low vulcanization efficiency, resource waste, and insufficient capacity.

[0003] Especially in the production of XLPE insulated high-voltage cables of 110kV and above, standards stipulate that the insulation layer thickness for different voltage levels and conductor cross-sections should be distributed between 16-31mm. Insulation vulcanization occurs within the vulcanization pipe, where the inert gas inside the pipe is heated to 200-400℃ via radiation. This high temperature is then conducted radially from the outside inwards. Therefore, the large insulation layer thickness of 16-31mm will result in radial temperature differences during the cross-linking process. Temperature is a necessary condition for the cross-linking and vulcanization of XLPE insulation, and these temperature differences will inevitably lead to varying degrees of cross-linking along the radial direction. When using equipment such as VCV (vertical cross-linking production line) and CCV (cab cross-linking production line) in the cross-linking and vulcanization process of XLPE insulated high-voltage cables, conductor preheating is a feasible and effective technical method in the industry to improve the uniformity of cross-linking in the radial direction of the XLPE insulation during vulcanization. Conductor preheating can reduce the temperature difference between the inside and outside of the insulation along the diameter direction, improve the uniformity of vulcanization, and enhance product quality. In existing technologies, conductor preheating is performed before the conductor enters the extruder head, with the conductor protruding outside the head, allowing for real-time temperature measurement. Therefore, this preheating method is widely used. Other heating methods are largely abandoned because they cannot measure conductor temperature. However, this preheating method suffers from insufficient radial temperature of the cable insulation layer, resulting in inadequate cross-linking and affecting cable quality.

[0004] Therefore, those skilled in the art are dedicated to developing a conductor preheating method and preheating system for the cable cross-linking process to improve the quality of cross-linking vulcanization. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a conductor preheating method in the cross-linking process of cables to improve the efficiency of cross-linking vulcanization.

[0006] To achieve the above objectives, the present invention provides a conductor preheating method in the cable cross-linking process, comprising the following steps:

[0007] 1) The conductor is preheated for the first time before entering the extruder, so that the first preheating temperature T1 of the conductor after the first preheating is controlled at 90-100℃, preferably 95℃;

[0008] 2) After the conductor exits the extruder, the foreign material is preheated a second time, and a second preheating temperature T2 is set. The heating power y for the second preheating is set according to the second preheating temperature T2.

[0009] The second preheating temperature T2 is controlled between 140 and 170°C, preferably 160°C.

[0010] Preferably, the heating power y is calculated using the following formula:

[0011]

[0012] Where x1 is the preheating power, that is, the heating power required to increase the temperature by one unit when the conductor is preheated for the first time;

[0013] T0 is the temperature of the conductor before the first preheating.

[0014] Preferably, the heating power y is calculated using the following formula:

[0015] y = x²(T² - T¹)

[0016] Where x2 is the measured value;

[0017] The measured value x2 was obtained using the following method:

[0018] Cool the vulcanized pipe to room temperature, stop the extruder, heat the conductor at the extruder outlet, and run the conductor in the opposite direction. Measure the conductor temperature at the extruder inlet and record the heating power required to increase the temperature by one unit. This heating power is the measured value multiplied by 2.

[0019] Preferably, the heating power y is obtained by the following method:

[0020] 21) Open the vulcanization pipe and cool it to room temperature. Stop the extruder and run the conductor in the positive direction. Heat the conductor to the first preheating temperature T1 at the first preheating device before it enters the extruder.

[0021] 22) After the conductor has traveled 2 to 3 meters, reverse the direction of the line and run the line in the opposite direction at the same speed. Turn on the second preheating device at the outlet of the extruder to heat it, and open the opening at the end of the vulcanizing pipe connected to the extruder. Measure the conductor temperature at this point, which is the test temperature.

[0022] 23) Adjust the power of the second preheating device and repeat steps 21) and 22) until the test temperature reaches the second preheating temperature T2. Record the set power of the preheating device after the conductor at this time. This set power is the heating power y.

[0023] The present invention also provides a conductor preheating system in the cross-linking process of cables, including a first preheating device and a second preheating device, wherein the first preheating device is installed at the inlet of the extruder and the second preheating device is installed in the cross-linking vulcanization pipe at the outlet of the extruder.

[0024] Preferably, an infrared thermometer is installed on the side between the first preheating device and the extruder.

[0025] Preferably, the first preheating device and the second preheating device are induction coil electromagnetic heating devices.

[0026] The beneficial effects of this invention are as follows: This invention preheats the conductor twice, before and after insulation extrusion. By controlling the temperature of the two heating cycles, the conductor reaches a preset temperature. This reduces the heat loss from the inside to the outside during extrusion. In conjunction with the radiant heating device in the cross-linking insulation pipe, this reduces the radial temperature difference of the cable insulation layer, improves the cross-linking quality, and the effective two preheating cycles also improve the cross-linking efficiency, greatly saving production time. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of Embodiment 4 of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that in the description of the present invention, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific manner. Therefore, they should not be construed as limitations on the present invention. Terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] Example 1

[0030] A conductor preheating method in a cable cross-linking process includes the following steps:

[0031] 1) The conductor is preheated for the first time before entering the extruder, so that the first preheating temperature T1 of the conductor after the first preheating is controlled at 90-100℃.

[0032] 2) After the conductor exits the extruder, the foreign material is preheated a second time, and a second preheating temperature T2 is set. The heating power y is set according to the second preheating temperature T2, and the second preheating temperature T2 is controlled between 140 and 170°C.

[0033] This application preheats the cable conductor twice before formal cross-linking and controls the preheating temperature. This not only avoids the conductor temperature from becoming too high during the first heating, which would affect the conductor performance, but also allows the conductor to reach a higher temperature after the second preheating. During cross-linking, this reduces the radial temperature difference of the cable insulation layer, improves the uniformity of cross-linking, and thus improves the quality of the cable.

[0034] In existing technologies, heating devices are only installed at the cable inlet. However, it takes several minutes for the conductor heated at this point to travel to the extruded insulation coating. The greater the temperature difference between the conductor and the environment, the greater the energy loss and the higher the energy consumption within the same time. This application overcomes the problem of high energy loss in existing technologies by using a low first preheating temperature and a high second preheating temperature. Furthermore, the two preheating and temperature control of the conductor before and after extrusion in this application effectively improves the crosslinking quality and efficiency of the cable.

[0035] Furthermore, in existing technologies, the distance between the cable inlet of the extruder head and the wire feeding device cannot be too long, resulting in limited space for the conductor before it enters the extruder head, thus restricting the heating power. In this application, however, the first preheating temperature is not high, and a large distance and space between the cable inlet of the extruder head and the wire feeding device are not required, thus significantly saving space. Simultaneously, controlling the first preheating temperature at 90–100°C avoids the risk of burns to workers due to excessively high temperatures.

[0036] Secondly, because the cable outlet of the extruder head is directly connected to the cross-linking vulcanization pipe 4 in cable production, it is not possible to measure the temperature of ordinary cable conductors. Therefore, the heating power for the second preheating is very important. If the power is too low, the temperature of the insulation layer on the radial side close to the conductor will not be sufficient, which will also affect the cross-linking efficiency. If the power is too high, exceeding the necessary value for insulation cross-linking, it will inevitably affect the quality of the cable.

[0037] Therefore, it is necessary to estimate the heating power to achieve the heating temperature required in this application. In this embodiment, the heating power y is calculated using the following formula:

[0038]

[0039] Where x1 is the preheating power, that is, the heating power required to increase the temperature by one unit when the conductor is preheated for the first time.

[0040] T0 is the temperature of the conductor before the first preheating.

[0041] For example, producing 220kV 1×2500mm 2 Taking the insulation of a certain type of cable as an example, when the room temperature (T0) of the conductor before the first preheating is 30℃, the first preheating temperature T1 after the first preheating is 95℃, and the second preheating temperature T2 is set to 160℃, the power required for the first preheating of the conductor is measured to be 25kW. The heating power can be calculated using the above formula.

[0042]

[0043] Therefore, in this case, the heating power for the second heating is set to 25kW.

[0044] Verification has shown that this method can increase production efficiency by 10%, achieve a first-pass yield of 80%, and with continuous adjustments, the yield can be increased to 100%.

[0045] Example 2

[0046] The conductor preheating method in the cable cross-linking process of this embodiment is the same as that in Embodiment 1, except that the heating power y is calculated using the following formula:

[0047] y = x²(T² - T¹)

[0048] Where x2 is the measured value;

[0049] The measured value x2 was obtained using the following method:

[0050] Cool the vulcanized pipe to room temperature, stop the extruder, heat the conductor at the extruder outlet, and run the conductor in the opposite direction. Measure the conductor temperature at the extruder inlet and record the heating power required to increase the temperature by one unit. This heating power is the measured value multiplied by 2.

[0051] To improve accuracy, multiple experiments can be conducted according to the method of this embodiment to plot the power required for different temperature increases of conductors of different specifications. In actual production, the desired temperature increase value can be obtained by looking up the plotted curves in a table.

[0052] Similarly, for the production of 220kV, 1×2500mm 2 Taking the insulation of a certain type of cable as an example, when the room temperature T0 is 30℃, using the method of this embodiment, the required preheating power to raise the temperature to 60℃ is 14kW. Therefore, the power required to raise the temperature of this conductor by 1℃ during preheating can be calculated as 14 ÷ (60-30) = 0.467kW / ℃. Then, the power required to raise the temperature of the conductor to 160℃ T2 after the first heating to 95℃ (T1) can be calculated.

[0053] y = 0.467 × (160 - 95) = 30.4 kW

[0054] To improve accuracy, the method described in this embodiment can be used to repeatedly test and record the power required for conductors of different specifications to rise in temperature by different degrees. For example, record the power required to raise the temperature of a conductor from 95℃ to 160℃ by 1℃ x2, and then perform the calculation. This will help improve the accuracy of the measured value x2.

[0055] Verification has shown that this method can increase production efficiency by 10%, and the first-pass yield rate of products reaches 93%, which can be increased to 100% after continuous improvement.

[0056] Example 3

[0057] The conductor preheating method in the cable cross-linking process of this embodiment is the same as that in Embodiment 1, except that the heating power y is obtained by the following method:

[0058] 21) Open the vulcanization pipe and cool it to room temperature. Stop the extruder and run the conductor in the positive direction. Heat the conductor to the first preheating temperature T1 at the first preheating device 1 before it enters the extruder.

[0059] 22) After the conductor has traveled 2 to 3 meters, reverse the direction of the line and run the line in the opposite direction at the same speed. Turn on the second preheating device 2 at the outlet of the extruder to heat it, and open the opening at the end of the vulcanizing pipe connected to the extruder. Measure the conductor temperature at this point, which is the test temperature.

[0060] 23) Adjust the power of the second preheating device 2 and repeat steps 21) and 22) until the test temperature reaches the second preheating temperature T2. Record the set power of the preheating device after the conductor at this time. This set power is the heating power y.

[0061] Similarly, for the production of 220kV, 1×2500mm 2 Taking the insulation of a certain type of cable as an example, the heating power required to raise the conductor temperature from 95℃ to 160℃ using the second preheating device 2 is recorded as 32kW. Therefore, in subsequent production, if producing cables of the same specification and controlling the same production temperature, the second preheating device can be directly connected to adjust the main power to 32kW.

[0062] It has been verified that this method can increase production efficiency by 10%, and the first-pass yield of products can reach 100%.

[0063] Example 4

[0064] like Figure 1 As shown, the present invention also provides a conductor preheating system for the cable cross-linking process, used for the execution of the above method, including a first preheating device 1 and a second preheating device 2. The first preheating device 1 is installed at the inlet of the extruder 3, and the second preheating device 2 is installed in the cross-linking vulcanization pipe 4 at the outlet of the extruder 3. An infrared thermometer 5 is installed on the side between the first preheating device 1 and the extruder 3. The first preheating device 1 and the second preheating device 2 are induction coil electromagnetic heating devices.

[0065] The first preheating device 1 is used to preheat the conductor for the first time before extrusion, and the second preheating device is used to preheat the conductor for the second time after extrusion. The induction coil electromagnetic heating device can heat only the conductor without affecting the cable insulation. It does not affect the original heating of the insulation layer within the cross-linking pipe. The infrared thermometer 5 can detect the first preheating temperature in real time, thereby adjusting the power of the first preheating device. It can also be used in Examples 1 and 2 to obtain the heating power y, the preheating power x1, and the measured value x2, to detect the cable temperature at the extruder inlet.

[0066] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A conductor preheating method in a cable cross-linking process, characterized in that, Includes the following steps: 1) Perform a first preheating before the conductor enters the extruder, so that the first preheating temperature T1 of the conductor after the first preheating is controlled at 90-100℃; 2) After the conductor exits the extruder, the conductor is preheated a second time, and a second preheating temperature T2 is set. The heating power y for the second preheating is set according to the second preheating temperature T2. The second preheating temperature T2 is controlled between 140 and 170°C; The heating power y is calculated using the following formula: y = x²(T² - T¹) Where x2 is the measured value; The measured value x2 was obtained using the following method: Cool the vulcanized pipe to room temperature, stop the extruder, heat the conductor at the extruder outlet, and run the conductor in the opposite direction. Measure the conductor temperature at the extruder inlet and record the heating power required to increase the temperature by one unit. This heating power is the measured value multiplied by 2.

2. A conductor preheating method in a cable cross-linking process, characterized in that, Includes the following steps: 1) Perform a first preheating before the conductor enters the extruder, so that the first preheating temperature T1 of the conductor after the first preheating is controlled at 90-100℃; 2) After the conductor exits the extruder, the conductor is preheated a second time, and a second preheating temperature T2 is set. The heating power y for the second preheating is set according to the second preheating temperature T2. The second preheating temperature T2 is controlled between 140 and 170°C; The heating power y is calculated using the following formula: ； Where x1 is the preheating power, that is, the heating power required to increase the temperature by a unit when the conductor is preheated for the first time; T0 is the temperature of the conductor before the first preheating.

3. A conductor preheating method in a cable cross-linking process, characterized in that, Includes the following steps: 1) Perform a first preheating before the conductor enters the extruder, so that the first preheating temperature T1 of the conductor after the first preheating is controlled at 90-100℃; 2) After the conductor exits the extruder, the conductor is preheated a second time, and a second preheating temperature T2 is set. The heating power y for the second preheating is set according to the second preheating temperature T2. The second preheating temperature T2 is controlled between 140 and 170°C; The heating power y is obtained by the following method: 21) Open the vulcanization pipe and cool it to room temperature. Stop the extruder and run the conductor in the positive direction. Heat the conductor to the first preheating temperature T1 at the first preheating device (1) before it enters the extruder. 22) After the conductor has traveled 2 to 3 meters, reverse the direction of the line and run the line in the opposite direction at the same speed. Turn on the second preheating device (2) at the outlet of the extruder to heat the conductor, and open the opening at the end of the vulcanizing pipe connected to the extruder. Measure the conductor temperature at this point to determine the test temperature. 23) Adjust the power of the second preheating device (2) and repeat steps 21) and 22) until the test temperature reaches the second preheating temperature T2. Record the set power of the conductor preheating device at this time. This set power is the heating power y.

4. A conductor preheating system for performing a conductor preheating method in the cable crosslinking process as described in any one of claims 1-3, characterized in that: It includes a first preheating device (1) and a second preheating device (2). The first preheating device (1) is installed at the inlet of the extruder (3), and the second preheating device (2) is installed in the cross-linking vulcanization pipe (4) at the outlet of the extruder (3).

5. The conductor preheating system in the cable cross-linking process as described in claim 4, characterized in that: An infrared thermometer (5) is installed on the side between the first preheating device (1) and the extruder (3).

6. The conductor preheating system in the cable cross-linking process as described in claim 4, characterized in that: The first preheating device (1) and the second preheating device (2) are induction coil electromagnetic heating devices.

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