CN102103905B - Defect eliminating method for main insulation of cold insulation superconducting cable and system structure for realizing method - Google Patents

Abstract

A method for eliminating defects in the main insulation of a cold-insulated superconducting cable is as follows: assemble to form a cable body, and seal and connect both ends of the cable body to a cable terminal or a cable head; connect the conductor that runs through the cable body to an external power source through a set of current leads and heat it by electricity, so that the heating temperature of the heated cable body is within the range of 50-180°C; evacuate and detect the vacuum degree; keep the heating temperature stable until the absolute vacuum degree in the cable cavity reaches below the order of ^10-1 Pa, fill the cable cavity with inert gas, make the absolute vacuum degree reach above 0.1Mpa, and maintain it for 2-24 hours; repeat the previous steps in a cycle to complete gas replacement; keep the seal, continue to fill with inert gas, make the gas pressure in the cable cavity higher than the atmospheric pressure, and complete the elimination of the main insulation of the cable. A system structure for implementing the above method includes a superconducting cable core, a cryostat, a cable terminal or a cable-specific head, and a set of gas inlets and outlets in the cable cavity composed of the cable terminal or the cable-specific head and the cryostat.

Description

A method for eliminating gaps in the main insulation of cold-insulated superconducting cables and a system structure for realizing the method

technical field

The invention belongs to the application field of superconducting power technology, and in particular relates to a method for eliminating defects of a cold-insulated superconducting cable and a system structure for realizing the method. the

Background technique

The cable core of the cold insulated superconducting cable has an independent and complete power transmission structure, including an inner support tube, a superconducting conductor, an insulating layer and a shielding layer, and its working low temperature environment is provided by a thermostat. When the cold-insulated superconducting cable is in operation, its main insulation is in a low-temperature liquid nitrogen environment (about 77K). Since insulating materials such as rubber and cross-linked polyethylene (XLPE) cannot be used at liquid nitrogen temperatures, the main insulation of cold-insulated superconducting cables cannot be made of such materials, and therefore the overall insulation cannot be made by extrusion. At present, the main insulation of cold-insulated superconducting cables is usually made of insulating paper tape, which is made of paper-wrapped insulation. the

Paper-wrapped insulation refers to the method of spirally winding an insulating paper tape of a certain width layer by layer to make a cable main insulation layer with a certain thickness, which has been widely used in oil-immersed cables. Since the main insulation made by this method is not an integral insulation structure, a large number of air gaps are inevitably left in the insulating layer during processing. At the same time, the insulating paper tape contains wood fibers, has a high porosity, easily absorbs water, and is seriously affected by the external environment. The air gap and moisture in the main insulation are important factors that cause partial discharge and accelerate insulation aging. Therefore, after the winding of the cable insulation layer is completed, a series of processes must be passed to eliminate insulation defects such as air gaps and moisture in the insulation layer. the

In the production of conventional oil-immersed cables, processes such as drying and insulating oil impregnation are used, and a large-scale vacuum drying and impregnating furnace is used to complete the elimination of the main insulation of the cable. Firstly, heat, dry and dehydrate the insulation-wound cable in a vacuum environment, and then use insulating oil for vacuum impregnation, which can remove air gaps and moisture in the insulation layer. Thereafter, the outer protective layer of the cable is made under the condition of isolating the air, and the production of the oil-immersed cable is completed. the

However, the same process cannot be used for the fabrication of the main insulation of cold-insulated superconducting cables. First of all, there is a cryostat outside the core of the cold-insulated superconducting cable, which not only plays the role of circulating liquid nitrogen to provide a low-temperature working environment for the cable, but also plays the role of a cable protective layer. The cryostat is made of two bellows inside and outside, and the interlayer is vacuum, which plays the role of heat insulation. Because the structure of the cryostat is very complicated, whether it is extruded in situ on the cable core, or the cable core is assembled through the tube after the cryostat is fabricated, the cable core will inevitably be In contact with the atmosphere, the insulating layer will absorb moisture in the air, resulting in deterioration of insulation performance. Secondly, insulating oil cannot be used in a liquid nitrogen environment. This is because the insulating oil will solidify at low temperatures. Even if the cable is impregnated, a new air gap will be left in the insulation due to the shrinkage of the insulating oil. Moreover, when the cable is in normal operation, the insulating oil cannot be replenished and the newly formed insulating air gap cannot be filled. To sum up, after the insulation layer of the cold insulated superconducting cable is wound, it cannot be dried and impregnated according to the conventional oil-immersed cable defect elimination process, so as to remove the air gap and moisture in the main insulation that seriously affect the insulation capacity of the cable. defect. the

Contents of the invention

The object of the present invention is to provide a method for eliminating defects in the main insulation of cold-insulated superconducting cables. the

Another object of the present invention is to provide a system structure of a method for eliminating gaps in the main insulation of a cold-insulated superconducting cable. the

To achieve the above object, the present invention takes the following design scheme:

A method for eliminating gaps in the main insulation of a cold-insulated superconducting cable, the method steps are as follows:

1) Assemble the superconducting cable core with the cryostat after the main insulation winding to form the cable body;

2) The two ends of the cable body are sealed and connected to the cable terminal or a special cable head, and the cryostat and the terminal or cable head form a cable cavity, and the cable core is sealed in the cable cavity; among them, at the cable terminal 1. At least one vacuum nozzle and at least one gas delivery port, or at least one set of gas ports are independently or separately provided on any one or more parts of the special head and the cryostat;

3) Connect the conductor running through the cable body with the external power supply through a set of current leads;

4) Heating with electricity, so that the heating temperature of the heated cable body is within the range of 50-180°C; at the same time, use at least one vacuum pump to vacuum the cable cavity through a vacuum nozzle or a gas interface, and detect the temperature in the cable cavity. the degree of vacuum;

5) Keep the heating temperature stable until the absolute vacuum in the cable cavity reaches the order of 10 ^-1 ·Pa or lower, and maintain it for more than 2 hours without large fluctuations;

6) Fill the cable cavity with an inert gas with a purity of 99.9% or above, so that the absolute vacuum in the cable cavity reaches above 0.1Mpa, and maintain it for 2-24 hours;

7) Recirculate and repeat steps 4) to 6) 2-10 times to achieve the purpose of replacing the gas contained in the main insulating layer of the cable with nitrogen or other inert gases, and complete the gas replacement;

8) On the premise of maintaining the airtightness of the cable cavity, continue to fill the cable cavity with an inert gas with a purity of 99.9% or above, and make the internal gas pressure higher than atmospheric pressure;

9) Complete the elimination of the main insulation of the cable. the

The conductor that runs through the cable body is the cable conductor in the cable core; or the metal inner support tube; or the metal inner wall of the cryostat; or the metal outer wall of the cryostat. the

The two ends of the cable body are connected to the cable terminal to form the state of complete installation, then the in-situ elimination of the main insulation of the cable has been completed. As mentioned above, both ends of the cable body are connected to the cable head, and then the second in-situ treatment is performed when the terminal is assembled, and the above steps 4) and 5) are repeated until the in-situ elimination of the main insulation of the cable is completed. lack. the

A system structure for realizing the method for eliminating defects in the main insulation of cold-insulated superconducting cables, including a superconducting cable core and a cryostat for completing the winding of the main insulation, the two ends of the cable body and the cable terminals or special cable glands Sealed connection, the cryostat and the terminal or cable head form a cable cavity, and the cable core is sealed in the cable cavity; among them, on any one or more parts of the cable terminal, special head and cryostat At least one vacuum nozzle and at least one gas delivery port, or at least one gas interface are provided; and a set of current lead wires is used to connect the conductor passing through the cable body to an external power source. the

The present invention utilizes the characteristics of the cold insulated superconducting cable's own structure and manufacturing process, and after the assembly of the cold insulated superconducting cable is completed, the main insulation of the cable is eliminated. Insulation elimination. the

The advantages of the present invention are:

1. The method of the present invention can effectively solve the problem of absorption of the insulating material caused by the contact between the main insulation and air during the preparation process of the cold-insulated superconducting cable by improving the cavity structure of the assembled cable and the improvement of the implemented process. Moisture problem, solving the problem of impregnation with insulating oil to eliminate the porosity in the main insulation. the

2. Since the use of large-scale vacuum drying and impregnation equipment is avoided, the process is simplified, so the cost of cable production is greatly reduced, and a low-cost and convenient process plan is provided for the elimination of the main insulation of cold-insulated superconducting cables , which is of great significance to the fabrication of cold-insulated superconducting cables. the

Description of drawings

Fig. 1 is a schematic diagram of the assembly structure of the cold insulated superconducting cable of the present invention. the

Fig. 2 is a schematic diagram of the assembly structure of the cold insulated superconducting cable body with a special cable head according to the present invention. the

Below in conjunction with accompanying drawing and specific embodiment the invention is described in further detail:

Detailed ways

In order to realize the method for eliminating defects in the main insulation of the cold-insulated superconducting cable of the present invention, at first the assembly structure of the cold-insulated superconducting cable should be newly designed, as shown in Fig. The connection between the main body (consisting of the superconducting cable core 1 and the cable cryostat 2) and the cable terminal 3 (including the sealing flange 4 for the cable terminal), the cable terminal 3 and the cable cryostat 2 are connected through a sealing flange 4 , forming a sealed cable cavity. When the superconducting cable is running, the cable cavity is a liquid nitrogen flow channel, which provides a low temperature environment for the cable core. the

In addition to being connected to the cable terminal, the cable body can also be connected to a special cable head 5 and a current lead to seal the cable core in the cable cryostat, as shown in FIG. 2 . the

Compared with the cold insulated superconducting cable in the past, the cold insulated superconducting cable disclosed by the present invention has a At least one group of gas inlets and outlets; this group of gas inlets and outlets can be a combination of at least one vacuum nozzle 6 and at least one gas delivery port 7, or have at least one gas interface that can be used for both vacuuming and input gas (simultaneously Replaces a set of vacuum nozzles and air ports). After the cold insulated cable is assembled, the cable cavity can be evacuated or filled with gas. The vacuum nozzle, gas delivery port or gas interface can be separately or independently set on the cable terminal, special head and cryostat. According to the volume of the cable cavity and the speed requirements of vacuuming and inflation, one or more vacuum nozzles, gas delivery ports or gas interfaces can be set. the

In order to further implement the method for eliminating defects of the main insulation of the cold insulated superconducting cable of the present invention, the cable body of the present invention is connected with a set of current leads 9, and the current leads can be connected with the conductors in the cable body, or can be connected with the conductors penetrating the cable body. Connect to other conductors, such as metal support tubes in cable cores, metal inner or outer walls of cryostats and other conductors. A current lead can be one energized line or multiple energized lines. The current lead is connected to an external power supply, and the external power supply provides AC or DC power. At room temperature, a certain AC or DC power is passed into the conductor in the cable body to generate Joule heat to heat the cable body and dry the main insulation. the

Using the above-mentioned assembly structure design, it is possible to realize the defect elimination treatment of the main insulation of the cold-insulated superconducting cable core. The specific implementation method steps are as follows: 

1) Complete the assembly of the superconducting cable core wound by the main insulation and the cryostat to form the cable body. the

2) Connect both ends of the cable body to the cable terminal or a dedicated cable head. The cryostat and the terminal (or cable head) form a cable cavity, and the cable core is sealed in the cable cavity, wherein any one or more parts on the cable terminal, the special head and the cryostat are independent Or at least one vacuum nozzle, at least one gas delivery port, or at least one gas connection are provided respectively. (One or more vacuum nozzles, gas delivery ports or gas ports can be independently installed on any part of the cable terminal, special head and cryostat, or can be installed on the cable terminal, special head and cryostat at the same time. The thermostat is equipped with a vacuum nozzle, gas delivery port or gas interface, and the form is not limited, as long as the overall assembly structure has at least a vacuum nozzle, gas delivery port or gas interface.) 

3) Use a set of current leads to connect the conductor running through the cable body with the external power supply to form a heatable circuit. the

4) Heating with electricity, the heating temperature takes the highest temperature that will not cause thermal damage to the cable body as the temperature upper limit, and is set within the range of 50-180°C; while energizing and heating the cable body, use at least one vacuum pump to pass through the vacuum nozzle or The gas interface evacuates the cable cavity, and uses a vacuum gauge to detect the vacuum in the cable cavity. the

5) When the heating temperature is stable, the absolute vacuum degree in the cable cavity reaches the order of 10 ^-1 ·Pa or lower, and maintains for more than 2 hours without large fluctuations. It can be considered that the main insulation of the cable has been dried and dehydrated.

6) Fill the cable cavity with nitrogen or other inert gases with a purity of 99.9% or more, such as helium, neon, argon, etc., so that the absolute vacuum in the cable cavity reaches or slightly exceeds 0.1MPa (that is, 1 atmospheric pressure ), maintained for 2-24 hours;

7) Carry out steps 4 and 5 again. After 2-10 repetitions of steps 4 and 5, the purpose of replacing the gas contained in the main insulating layer of the cable with nitrogen or other inert gases is achieved. the

8) After completing the gas replacement, fill the cable cavity with nitrogen or other inert gas with a purity of 99.9% or higher. Keep the airtightness of the cable cavity and make the internal gas pressure higher than the atmospheric pressure to ensure that the outside air does not enter the cable cavity. the

If the cold insulated superconducting cable has been installed, according to steps 4-6, the main insulation of the cable can be eliminated in situ, and then it can be put into use. If the cable body is only connected to the head due to storage, transportation or other reasons, the main insulation of the cable can also be eliminated through steps 4-6. During the assembly process of the cable body and the terminal, the cable core will be in contact with the air for a short time. Therefore, after the installation is completed, a second in-situ treatment is required. the

The present invention is further described below in conjunction with specific embodiment:

Perform in-situ defect elimination on the main insulation of a single-phase 3m, 10kV/1500A cold insulated superconducting cable. There is a gas interface designed on the cable terminal, which can be used for vacuuming and inputting a certain pressure of gas. The specific operation steps are as follows: 

1. Assemble the 3m-long superconducting cable core that has completed the main insulation winding with the cryostat to form the cable body. the

2. Connect both ends of the cable body to the cable terminal. The cryostat and the cable terminal form a cable cavity, and the cable core is sealed in the cable cavity. the

3. The two current leads are respectively connected to the superconducting conductor layer and the superconducting shielding layer in the core of the superconducting cable. The external power supply provides 0~15A DC to the superconducting conductor layer and the superconducting shielding layer respectively through the current lead, and heats the cable body evenly to achieve the purpose of drying the main insulation. The heating process should be slow, and the temperature should be kept constant for several hours in the temperature zone where the gas is concentrated and released, so as to ensure that the gas in the insulating layer is released slowly and evenly, and bubbles will not be formed in the insulating layer due to excessive gas generation, which will damage the insulating structure. The maximum heating temperature is set at 120-150°C. the

4. While energizing and heating, use a mechanical vacuum pump to evacuate the cable cavity through the vacuum nozzle, and use a vacuum gauge to detect the vacuum degree in the cable cavity. When the heating temperature is stabilized at 120°C, the absolute vacuum in the cable cavity reaches below 5×10 ^-1 ·Pa and remains unchanged for 2 hours. It can be considered that the main insulation of the cable has been dried and dehydrated.

5. Fill the cable cavity with nitrogen with a purity of 99.9% or above, so that the absolute vacuum in the cable cavity reaches or slightly exceeds 0.1Mpa. Go to steps 3 and 4 again. After 2 repetitions of steps 3-5, the gas replacement in the main insulation of the cable is completed with nitrogen. the

6. Fill the cable cavity with nitrogen gas with a purity of 99.9%. Keep the airtightness of the cable cavity and make the internal gas pressure higher than the atmospheric pressure to ensure that the outside air does not enter the cable cavity. the

After the above steps, the main insulation of the single-phase 3m, 10kV/1500A cold insulated superconducting cable has been completed in situ. the

Claims (6)

1. the scarce method that disappears of a cold insulation hyperconductive cable main insulation is characterized in that method step is following:

1) hyperconductive cable cable core and the cryostat that will accomplish the main insulation coiling assemble, and form cable body;

2) two ends with cable body are tightly connected with cable termination or special-purpose cable end socket simultaneously, and cryostat and cable termination or cable end socket have formed the cable cavity, and cable conductor is sealed in the cable cavity; Wherein, independence or be respectively provided to few one group of gas inlet-outlet on any or the plural parts on cable termination, special-purpose end socket and the cryostat;

The electric conductor that 3) will run through cable body through one group of current feed is connected with external power;

4) energising heating makes heated cable body heating-up temperature in 50-180 ℃ scope; Simultaneously, use at least one vacuum pump the cable cavity to be vacuumized through vacuum pumping mouth or gas interface, and the vacuum degree in the detection streamer cavity;

5) keep the stable of heating-up temperature, the absolute vacuum degree reaches 10 in the cable cavity ^-1Below the Pa order of magnitude, and keep fluctuation did not take place more than 2 hours;

6) in the cable cavity, charge into purity be 99.9% and more than inert gas, make that the absolute vacuum degree reaches more than the 0.1Mpa in the cable cavity, kept 2-24 hour;

7) the recirculation repeating step 4) to 6) 2-10 time, reach the purpose of the contained gas of cable main insulating layer being replaced with nitrogen or other inert gases, accomplish gas displacement;

8) under the prerequisite that keeps cable cavity sealing, continue with purity be 99.9% and above inert gas charge in the cable cavity, and make its internal gas pressure be higher than atmospheric pressure;

9) it is scarce to accomplish disappearing of cable main insulation.

2. the scarce method that disappears of cold insulation hyperconductive cable main insulation according to claim 1 is characterized in that: the two ends of described cable body are to be connected with cable termination and to form the state of accomplish installing, and the original position of then having accomplished cable main insulation disappears scarce.

3. the scarce method that disappears of cold insulation hyperconductive cable main insulation according to claim 1; It is characterized in that: the two ends of described cable body all are connected with the cable end socket; Carry out secondary in-situ treatment, recirculation repeating step 4 when then assembling with the terminal again), step 5) disappears scarce until the original position of accomplishing cable main insulation.

4. the scarce method that disappears of cold insulation hyperconductive cable main insulation according to claim 1 is characterized in that: described inert gas is nitrogen, helium, neon or argon gas.

5. the scarce method that disappears of cold insulation hyperconductive cable main insulation according to claim 1 is characterized in that: the said electric conductor that runs through cable body is the cable conductor in the cable conductor, or is stay pipe in the metal; Or be the metal inner surface of cryostat; Or be the metal outer wall of cryostat.

6. the scarce method that disappears of cold insulation hyperconductive cable main insulation according to claim 1 is characterized in that: said one group of gas inlet-outlet is at least one vacuum pumping mouth and at least one blowing mouth; Or gas interface that not only can be used for vacuumizing but also can be used for importing gas.

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