A method and apparatus for rapid degassing of the insulated core of a long submarine cable

Abstract

The application discloses a method and device for quick degassing of a large-length submarine cable insulating core, comprising the following steps: S1, sealing one end of the insulating core and connecting the sealed end with a gas guide pipe; S2, connecting two ends of the insulating core with a direct current power supply; S3, determining the degassing insulating core meterage, measuring the initial direct current resistance, and calibrating; S4, inputting the conductor direct current resistance value reaching the specified temperature through a direct current power supply control page; S5, selecting the current or voltage rising speed; S6, when the temperature of the conductor rises to the degassing setting temperature, disconnecting the power supply and switching to a hot air heating circulation system; S7, passing the hot air heated to the specified temperature into a degassing room, and placing a thermocouple in the degassing room to monitor the temperature in real time until the specified degassing temperature is reached and maintained. According to the application, the time required for the large-length submarine cable insulating core to reach the degassing temperature specified by the process is greatly shortened, the production efficiency is high, the investment in the submarine cable insulating core degassing equipment is reduced, and the submarine cable production cost is lowered.

Description

Technical Field

[0001] This invention relates to the technical field of cables, and in particular to a method and apparatus for rapidly degassing the insulated core of a long submarine cable. Background Technology

[0002] As a primary component of offshore wind power transmission equipment, the annual demand for submarine cables continues to grow with the increase in installed offshore wind power capacity. Currently, submarine cable insulation mainly uses cross-linked polyethylene (XLPE). During the production of the insulated core, the polyethylene undergoes a cross-linking reaction under the action of peroxides, which generates some small-molecule byproducts. Some of these byproducts are discharged into the cross-linking pipeline under pressure and temperature, but some remain in the cooled insulated core. To ensure good radial water resistance, most submarine cables have an extruded lead sheath around the insulated core. If a large length of submarine cable has a high concentration of low-molecular-weight cross-linking byproducts in the insulated core, these byproducts will gradually precipitate as gas under temperature during use. However, because the lead sheath acts as a sealant, excessive gas can cause cable accessories to malfunction. Furthermore, excessive residual cross-linking byproducts can lead to localized electric field distortion during cable operation, making the cable insulation more susceptible to breakdown. All of these factors severely affect the reliability of cable operation. Therefore, after the submarine cable insulation core is produced, it needs to be placed in a constant temperature environment of approximately 70°C for a certain period of time to remove most of the residual low-molecular-weight byproducts. The commonly used method is to store the submarine cable insulation core in a long cable storage reel, using insulation material to isolate the reel from the surrounding environment; continuously blow circulating hot air into the reel from below, gradually increasing the temperature of the submarine cable insulation core until it stabilizes at the specified process temperature of approximately 70°C; after a certain period, most of the residual low-molecular-weight byproducts in the submarine cable insulation core precipitate out, reaching the required level for the process, and then cool it before further processing.

[0003] The existing technology has shortcomings and deficiencies in the degassing process of long-length submarine cable insulation cores due to the following factors: (1) the insulation cores have many layers and small gaps between adjacent cores, resulting in poor hot air circulation; (2) the heat transfer efficiency of air heating is inherently low; (3) the thermal conductivity of cable insulation and semi-conductive shielding materials is poor; (4) the submarine cable insulation cores are heavy and have high heat capacity, requiring a lot of heat to fully reach the degassing temperature specified in the process, thus the constant-temperature degassing time for submarine cable insulation cores is usually long. The degassing time for medium-voltage submarine cable insulation cores is generally at least 15 days, and for high-voltage submarine cable insulation cores it is generally at least 25 days, and may exceed 45 days in special cases. This greatly reduces the production efficiency of submarine cables and significantly increases the investment in insulation core degassing equipment for submarine cable manufacturers. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a device for rapid degassing of the insulated cores of long-length submarine cables. This device significantly shortens the time required for the insulated cores of long-length submarine cables to reach the degassing temperature specified in the process, resulting in high production efficiency, reduced investment in degassing equipment for submarine cable insulated cores, and lower production costs for submarine cables. To achieve the above-mentioned objectives and other advantages of this invention, a device for rapid degassing of the insulated cores of long-length submarine cables is provided, comprising:

[0005] S1. Place the required length of insulated wire core in the degassing chamber, seal one end of the insulated wire core and connect it to the gas duct.

[0006] S2. Connect both ends of the insulated wire core to a DC power supply;

[0007] S3. Determine the length of degassed insulated wire core, measure the initial DC resistance of the insulated wire core conductor, and perform calibration by measuring the DC resistance of the conductor at 20℃ using a DC bridge and theoretical calculations.

[0008] S4. Input the DC resistance value of the conductor to reach the specified temperature through the DC power supply control page;

[0009] S5. Increase the current or voltage at a rate of 5-20A / min or 5-20V / min. Select the rate of increase of current or voltage according to the length of the degassed core, the conductor cross-section, and the heat and heating time required to reach the specified temperature.

[0010] S6. When the temperature of the conductor rises to the degassing set temperature, disconnect the power supply and switch to the hot air heating circulation system;

[0011] S7. Introduce hot air heated to the specified temperature into the degassing chamber. Place thermocouples in the degassing chamber to monitor the temperature in real time until the specified degassing temperature is reached and maintained. Continuously monitor the concentration of degassing byproducts. When the concentration drops to the specified value, shut down the hot air heating circulation system and allow it to cool naturally for 48 hours before proceeding to the next step.

[0012] Preferably, the formula for calculating the resistance of the insulated conductor core at a specified temperature in step S3 is as follows: R t =R 20 ×[1+α(t-20)],

[0013] Where R 20 R is the conductor resistance at 20℃; α is the temperature coefficient of conductor resistance, that is, the factor by which the conductor resistance increases for every 1℃ increase in temperature; t Let be the conductor resistance at temperature t, where t is the specified temperature, and the range of the specified temperature is 60 to 80℃.

[0014] A device for rapid degassing of the insulated core of a long submarine cable includes a degassing chamber, a hot air heating and circulation system connected to the degassing chamber, an insulated core placed in the degassing chamber, a DC power supply connected to the insulated core, a degassing byproduct monitoring device, and a control system.

[0015] Preferably, the degassing chamber and the sealed cable storage tray are all made of heat-insulating and sealing materials, and are equipped with a heat-insulating and sealing cover plate and an air-suction device on top.

[0016] Preferably, the degassing chamber has two outlet and inlet holes on the side, and the bottom of the degassing chamber has an independent space with an air inlet for connecting to the hot air heating circulation system. An air outlet is provided above the air inlet.

[0017] Compared with existing technologies, the advantages of this invention are as follows: Heating is achieved by applying electricity to the cable conductor. The insulated core of a long submarine cable is stored in a sealed, insulated cable reel, with both ends of the cable connected to a DC power supply. After the DC power supply is turned on, the output voltage (or current) is slowly increased to a set value and automatically kept constant. The conductor is directly heated, and the heat is conducted to the inner shield, insulation, and outer shield. The conductor resistance is monitored online in real time, and the power is cut off when the conductor resistance reaches a specified value. This heating method results in uniform heat generation throughout the cable conductor and high efficiency in heat dissipation through conduction. Therefore, the entire cable heats up quickly, significantly reducing the time required for the insulated core of a long submarine cable to reach the degassing temperature specified in the process.

[0018] The insulated core of the submarine cable is kept at a constant temperature by circulating heated gas. After the conductor temperature of the insulated core reaches the degassing temperature specified in the process, the output voltage (or current) of the DC power supply is slowly reduced until it reaches zero. Then, the DC power supply is turned off and disconnected from the conductor of the insulated core. Circulating hot air is continuously blown into the sealed space below the cable storage reel, keeping the insulated core of the submarine cable at a constant temperature for a certain period of time until the content of residual cross-linking byproducts inside meets the requirements. Attached Figure Description

[0019] Figure 1 A flowchart illustrating the method for rapid degassing of the insulated core of a long submarine cable according to the present invention;

[0020] Figure 2 This is a schematic diagram of the device for rapid degassing of the insulated core of a long submarine cable according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Reference Figure 1-2 A method for rapid degassing of the insulated core of a long submarine cable includes: S1, placing the insulated core of the required length in a degassing chamber, sealing one end of the insulated core and connecting it to a gas duct;

[0023] S2. Connect both ends of the insulated wire core to a DC power supply;

[0024] S3. Determine the length of degassed insulated wire core, measure the initial DC resistance of the insulated wire core conductor, and perform calibration by measuring the DC resistance of the conductor at 20℃ using a DC bridge and theoretical calculations.

[0025] S4. Input the DC resistance value of the conductor to reach the specified temperature through the DC power supply control page;

[0026] S5. Increase the current or voltage at a rate of 5-20A / min or 5-20V / min. The rate of increase should be selected based on the length of the degassed conductor, the conductor cross-section, the heat required to reach the specified temperature, and the heating time. Currently, the selectable current range is 50A to 1000A, and the selectable voltage range is 50V to 1000V. The heat required for conductor heating can be calculated using the following formula:

[0027] W 所需热量 =ρ*g*((C_specified temperature - C_initial temperature) / 100)*t(J),

[0028] Where ρ is the specific heat capacity of copper, measured in J / (kg·℃).

[0029] g – the weight of copper, measured in kg.

[0030] t — time, in seconds (S)

[0031] S6. When the temperature of the conductor rises to the degassing set temperature, disconnect the power supply and switch to the hot air heating circulation system;

[0032] S7. Introduce hot air heated to the specified temperature into the degassing chamber. Place thermocouples in the degassing chamber to monitor the temperature in real time until the specified degassing temperature is reached and maintained. Continuously monitor the concentration of degassing byproducts. When the concentration drops to the specified value, shut down the hot air heating circulation system and allow it to cool naturally for 48 hours before proceeding to the next step.

[0033] Preferably, it includes a degassing chamber, a hot air heating circulation system connected to the degassing chamber, an insulated wire core placed in the degassing chamber, a DC power supply connected to the insulated wire core, a degassing byproduct monitoring device, and a control system.

[0034] Preferably, the degassing chamber and the sealed cable storage tray are all made of heat-insulating and sealing materials, and are equipped with a heat-insulating and sealing cover plate and an air-suction device on top.

[0035] Preferably, the degassing chamber has two pre-reserved outlet and inlet holes on its side, and the bottom of the degassing chamber has an independent space with an air inlet for connecting to the hot air heating circulation system. An air outlet is provided above the air inlet.

[0036] Furthermore, the formula for calculating the resistance of the insulated conductor core at a specified temperature in step S3 is as follows: R t =R 20 ×[1+α(t-20)],

[0037] Where R 20 R is the conductor resistance at 20℃; α is the temperature coefficient of conductor resistance, that is, the factor by which the conductor resistance increases for every 1℃ increase in temperature; t Let be the conductor resistance at temperature t, where t is the specified temperature, and the range of the specified temperature is 60 to 80℃.

[0038] A device for rapid degassing of the insulated cores of long submarine cables includes a degassing chamber, a hot air heating and circulation system connected to the degassing chamber, insulated cores placed in the degassing chamber, a DC power supply connected to the insulated cores, a degassing byproduct monitoring device, and a control system. The degassing chamber and the sealed cable storage reel are all surrounded by thermal insulation and sealing materials, and are topped with a thermal insulation and sealing cover and an air intake device. Two cable outlet and inlet holes are pre-drilled on the side of the degassing chamber. An independent space is provided at the bottom of the degassing chamber, with an air inlet connected to the hot air heating and circulation system. An air outlet is located above the air inlet. Specifically, when hot air passes through the densely arranged insulated cores and reaches the top, the air temperature decreases, and it is transported through the air outlet to the air heating device for reheating, before being sent back to the bottom of the degassing chamber through the air inlet to form a circulation. The structure of the entire degassing chamber is illustrated by this example, but the form is not limited to this; all insulated and sealed degassing chamber structures are within the scope of protection.

[0039] During implementation, the conductor of the insulated core is first heated by applying electricity. The long-length submarine cable insulated core is stored in a sealed, insulated degassing chamber, with the exposed conductors at both ends connected to a DC power supply. After the DC power supply is turned on, the output voltage (or current) is slowly increased to the set value and automatically controlled to remain constant. The conductor is directly heated, and the heat is conducted to the inner shield, insulation, and outer shield. The conductor resistance is monitored online in real time, and the power is cut off when the conductor resistance reaches the specified value. This heating method results in uniform heat generation throughout the conductor and high efficiency in heat dissipation through conduction. Therefore, the entire degassed insulated core heats up quickly, significantly reducing the time required for the long-length submarine cable insulated core to reach the specified degassing temperature.

[0040] The insulated core of the submarine cable is kept at a constant temperature by circulating heated gas. Power supply is stopped once the insulated core reaches the degassing temperature specified in the process. The DC power supply is turned off and disconnected from the insulated core. Circulating hot air is continuously blown into the enclosed space from below the degassing chamber, maintaining the insulated core at the specified process temperature for a certain period until the content of residual cross-linking byproducts inside meets the requirements.

[0041] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be apparent to those skilled in the art.

[0042] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method of rapid degassing of a large length submarine cable insulation core, characterized in that, The method comprises the following steps: S1, placing the insulation wire core of the required length in a degassing room, sealing one end of the insulation wire core and connecting it with a gas guide pipe; S2, connecting the two ends of the insulation wire core with a direct current power supply; S3, determining the degassing insulation wire core meterage, measuring the initial direct current resistance of the insulation wire core conductor, calibrating through the direct current bridge measurement of the conductor direct current resistance at 20℃ and theoretical calculation; S4, inputting the conductor direct current resistance value reaching the specified temperature through the direct current power supply control page; S5, increasing the current or voltage at a speed of 5-20 A / min or 5-20 V / min, and selecting the current or voltage increasing speed according to the length of the degassing wire core, the conductor cross section and the heat required to rise to the specified temperature and the heating time; S6, when the temperature of the conductor rises to the degassing setting temperature, disconnecting the power supply and switching to the hot air heating circulation system; 2. A method of rapid degassing of a large length submarine cable insulating core as claimed in claim 1, characterized in that, S7, passing the hot air heated to the specified temperature into the degassing room, placing a thermocouple in the degassing room to monitor the temperature in real time, until the specified degassing temperature is reached and maintained, continuously monitoring the concentration of the degassing byproduct, when it is reduced to the specified value, closing the hot air heating circulation system, naturally cooling for 48 hours, and performing the next process. R t = R 20 x [1 + a (t - 20)], wherein R 20 is the resistance of the conductor at 20°C; α is the temperature coefficient of the resistance of the conductor, i.e. the factor by which the resistance of the conductor increases for each 1°C increase in temperature; R t is the resistance of the conductor at temperature t, where t is the specified temperature and the specified temperature has a range value of 60 to 80°C.

3. A device for rapid degassing of an insulated core of a long submarine cable, which uses the method for rapid degassing of an insulated core of a long submarine cable according to any of claims 1-2, characterized in that, The formula for calculating the resistance of the insulation wire core conductor at the specified temperature in step S3 is as follows:

4. A device for rapid degassing of a large length submarine cable insulation core as claimed in claim 3, characterized in that, The degassing room, the hot air heating circulation system connected with the degassing room, the insulation wire core placed in the degassing room, the direct current power supply connected with the insulation wire core, the degassing byproduct monitoring device and the control system are included.

5. A device for rapid degassing of a large length submarine cable insulation core as claimed in claim 4, characterized in that, The degassing room and the sealing cable storage reel are surrounded by heat preservation sealing materials, and a heat preservation sealing cover plate and an air suction device are arranged above the degassing room. Two outgoing and incoming line holes are reserved on the side of the degassing room, and an independent space is arranged at the bottom of the degassing room, the space is provided with an air inlet connected with the hot air heating circulation system, and an air outlet is arranged above the air inlet.

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