CN110401046B - Method for reducing alternating current loss of superconducting cable in CICC superconducting conductor joint box - Google Patents

Abstract

The invention discloses a method for reducing the AC loss of a superconducting cable in a CICC superconducting conductor splice box. AC loss and energy loss caused by cross-current between sub-cables. These two losses not only consume the energy to drive the superconducting magnet, but also generate heat, causing temperature changes inside the superconducting joint, resulting in unstable performance of the superconducting joint. The sub-cable shielding operation completely interrupts the current loop by insulating and shielding a part of the current loop, eliminating the AC loss between the superconducting cable and the copper surface. The resistance between the sub-cables is restored to the original state of the superconducting cable by inserting the barrier sheet between the sub-cables, so as to ensure that the loss caused by the cross-current between the sub-cables is reduced to an acceptable range. The structural feature of the invention is that the energy loss inside the superconducting joint is reduced to the greatest extent, and the electrical performance of the superconducting joint is improved.

Description

Method for reducing AC loss of superconducting cable in CICC superconducting conductor splice box

technical field

The invention relates to the field of superconducting joint boxes for nuclear fusion, in particular to a method for reducing the AC loss of superconducting cables in a CICC superconducting conductor joint box.

Background technique

Thermonuclear fusion will provide mankind with inexhaustible clean energy, and the International Thermonuclear Experimental Reactor (ITER) program will be built within the next decade. The superconducting joint is not only responsible for the series connection inside the superconducting magnet, but also for connecting the external feeder system, so the electrical performance of the superconducting joint directly limits the performance of the overall superconducting magnet. As shown in Figure 1, the superconducting cable of the superconducting joint in the prior art nuclear fusion device is composed of the following structures: 316L stainless steel armor 7 with an outer square and an inner circle, a superconducting cable 8 with a circular cross-section, and a stainless steel flower bag for the superconducting cable Band 9 composition. The superconducting cable 2 is made of six sub-cables 1-6 helically twisted, and the outer surface of each sub-cable is wrapped with a sub-cable stainless steel flower wrap 10, and the six sub-cables surround a central solenoid 11 (providing liquid helium cooling circuit).

Since the superconducting magnet works under AC conditions, the alternating magnetic field will cause a current loop between the superconducting cable in the superconducting splice box and the copper bottom surface of the splice box, resulting in AC loss and energy loss. At the same time, in the process of manufacturing the superconducting cable, it is necessary to remove the stainless steel tapes of the sub-cables of the superconducting cable, so that the resistance between the sub-cables of the superconducting cable is greatly reduced, and the AC loss generated between the sub-cables increases. Both of these conditions adversely affect the performance of superconducting joints, and methods must be taken to eliminate or reduce them.

SUMMARY OF THE INVENTION The purpose of the present invention is to provide a method for reducing the AC loss of the superconducting cable in the CICC superconducting conductor splice box, so as to solve the problem of large loss of the superconducting cable in the superconducting joint box of the prior art, and realize the improvement of the performance of the superconducting joint and energy consumption reduction.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The method for reducing the AC loss of superconducting cables in a CICC superconducting conductor splice box is characterized by comprising the following steps:

(1) Sub-cable shielding treatment:

First, confirm the contact position where the surface of the superconducting cable and the copper surface in the superconducting splice box are in contact with each other, and remove the stainless steel tape at the contact position to expose multiple sub-cables in the superconducting cable; For the two sub-cables, compare the areas of the two-occurring parts of the sub-cables that appear twice, and select the part with the smaller area as the shielding area; finally, use polyimide tape to wrap the shielding area;

(2) Inter-cable barrier treatment:

In step (1), between the two adjacent sub-cables at the contact position, a non-completely insulating barrier sheet is respectively inserted, so as to improve the resistance between the sub-cables and ensure that the sub-cables are not completely insulated.

The method for reducing the AC loss of a superconducting cable in a CICC superconducting conductor splice box is characterized in that: in step (1), an auxiliary mold is used to find the contact position, and the auxiliary mold is a rectangular body with a central through hole, wherein the center The diameter of the through hole is consistent with the diameter of the superconducting cable, the size of the rectangular body is consistent with the size of the copper surface in the superconducting cable splice box, the rectangular body is sleeved on the superconducting cable through the central through hole, and the side of the rectangular body is provided with a superconducting cable. The mold window exposed by the cable, the part displayed by the mold window is the part where the surface of the superconducting cable is in contact with the copper surface in the superconducting splice box.

The method for reducing the AC loss of the superconducting cable in the CICC superconducting conductor splice box is characterized in that: in step (1), the polyimide tape is wrapped in the shielding area by a 50% half-stacking method.

The method for reducing the AC loss of a superconducting cable in a CICC superconducting conductor splice box is characterized in that: the barrier sheet is a stainless steel barrier sheet, the stainless steel barrier sheet is inserted deep into the gap between two adjacent sub-cables, and the stainless steel barrier The sheet is completely buried between the two sub-cables and is not exposed.

The method for reducing the AC loss of the superconducting cable in the CICC superconducting conductor joint is characterized in that: the plane shape of the stainless steel barrier sheet is a fan shape, and the thickness of the stainless steel barrier sheet is consistent with the thickness of the stainless steel flower wrapping tape of the sub-cable .

In the present invention, an auxiliary mold specially customized according to the diameter of the superconducting cable and the size of the copper surface in the splice box is used to cover the surface of the superconducting cable, and the part displayed in the mold window is the superconducting cable and the copper surface in the splice box. Therefore, the precise position of the secondary contact with the copper surface on the superconducting cable can be accurately measured for the subsequent sub-cable shielding operation.

In the present invention, the sub-cable that is in secondary contact with the copper surface on the superconducting cable selects the part with a smaller area for insulation treatment, thereby cutting off the current loop between the superconducting cable and the copper bottom surface, eliminating the AC loss of this part, At the same time, the larger part of the sub-cable is kept in contact with the copper surface, and the electrical conductivity of the superconducting cable is preserved to the greatest extent.

In the present invention, the part of the sub-cable that needs to be insulated is wrapped with a 50% half-packed polyimide tape. Such an insulation treatment method is firm and wear-resistant, and even if some areas are damaged, the overall insulation will not fail.

In the present invention, the stainless steel barrier sheet is inserted into the gap between the sub-cables of the superconducting cable to increase the resistance between the sub-cables, thereby reducing the AC loss to an acceptable range, and at the same time, the sub-cables are not completely Insulation, to ensure that the superconducting cable still has a certain shunt capacity between the sub-cables after the quench phenomenon occurs in some sub-cables.

In the present invention, the thickness of the stainless steel barrier sheet is 0.1 mm, the plane shape is fan-shaped, and the length is about 150 mm to 200 mm. The thickness of the barrier sheet is the same as the thickness of the stainless steel tape of the sub-cable, so as to ensure that the insertion of the barrier sheet will not cause the change of the cross-sectional dimension of the ultra-short cable, and the barrier effect is consistent with the original stainless steel tape. The plane shape is fan-shaped, because the sub-cable gap of the superconducting cable is a spatial spiral, and only the fan-shaped barrier sheet specially made according to the size of the superconducting cable can be inserted into the gap between the sub-cables. The length of the barrier sheet is 150mm~200mm, because the length of the barrier sheet is too short, it will easily fall out from the gap of the superconducting cable, and if the length is too long, it will be difficult to insert due to the local irregularity of the gap between the sub-cables.

The present invention reduces the AC loss of the superconducting joint through two special operations. In fact, all the superconducting joints using the multi-level stranded superconducting cable under the AC working condition can apply the two operations in the present invention. method. The invention has good application value in the field of fusion reactor magnet manufacture and superconductivity.

The advantages of the present invention are:

The processing method of the invention is simple, clear and easy to operate, which can ensure the maximum reduction of AC loss inside the superconducting joint, reduce energy consumption, improve the current-carrying capacity of the superconducting joint, and at the same time ensure the safety and performance of the superconducting joint. stability.

Description of drawings

Figure 1 is a schematic diagram of the structure of the superconducting cable

FIG. 2 is a schematic diagram of the principle of sub-cable shielding.

FIG. 3 is a schematic diagram of inserting a barrier sheet between sub-cables.

Fig. 4 is a schematic diagram of the structure and use method of the auxiliary mold, wherein: Fig. a is a front view, and Fig. b is a top view.

Detailed ways

As shown in Figure 2, the sub-cable shielding operation:

First, confirm the position where the surface of the superconducting cable will contact the copper surface of the superconducting splice box, and place the auxiliary mold on the position. The structure and usage of the auxiliary mold are shown in Figure 4. The auxiliary mold is a rectangular body with a central through hole. 12. The diameter of the central through hole is consistent with the diameter of the superconducting cable 8, the size of the rectangular body 12 is consistent with the size of the copper surface in the splice box of the superconducting cable 8, and the rectangular body 12 is sleeved on the superconducting cable 8 through the central through hole , the side of the rectangular body 12 is provided with a mold window 13 for exposing the superconducting cable. Through the window 13 on the auxiliary mold, count the number of sub-cables of the superconducting cable from one end, and mark the sub-cables as 1, 2, 3...6 in sequence. The superconducting cable used in the present invention has only six sub-cables, so the seventh sub-cable that appears is sub-cable 1, the eighth sub-cable is sub-cable 2, and so on.

Find the sub-cables that appear twice in the mold window, the number may be 1~3, compare the areas of the two parts of each sub-cable, select the part with the smaller area as the shielding area, and mark it on the superconducting cable.

Sub-cable shielding treatment: some sub-cables of the superconducting cable (there may be 1~3 sub-cables) will contact the copper bottom surface twice (as shown in Figure 2, sub-cable 1 and sub-cable 2 are both in contact with the copper surface twice ), there are two connection paths between the two contact areas, one is the superconducting cable itself, and the other is conduction through the copper bottom surface, so that a current loop is formed between the sub-cable and the copper bottom surface. The countermeasure is to select the smaller part of the two contact areas of the same sub-cable (as shown in Figure 2, the left part of sub-cable 1 and the right part of sub-cable 2), wrap it with polyimide tape to make it. Insulation from the copper bottom surface cuts off the path of the current loop;

Wrap the marked area with polyimide tape in a 50% half-stack. Restore the opened superconducting cable to its original shape. Put the auxiliary mold on the superconducting cable again, and re-test whether the area covered by the package is correct.

Inserting the barrier sheet between the sub-cables:

As shown in Figure 3, starting from one end of the superconducting cable, in the area where the stainless steel tapes of the sub-cables are removed, insert barrier sheets in the 6 sub-cable gaps in turn to ensure that the barrier sheets are inserted deep into the gaps and do not exceed the superconducting the surface of the cable.

Before the superconducting cable is introduced into the splice box, the stainless steel tape of the superconducting cable sub-cable needs to be removed, which leads to an increase in the contact resistance between the sub-cables, and there is a current loop between adjacent sub-cables, which reduces the contact resistance. lead to an increase in AC loss. Therefore, in the present invention, a fan-shaped stainless steel barrier sheet whose thickness and material are the same as the original tapes is inserted into the gaps between different sub-cables, so as to restore the contact resistance between different sub-cables to the level of the original superconducting cable, Not only reduces the AC loss to a suitable level, but also maintains the ability to split the current between the sub-cables.

Claims (4)

1. The method for reducing the alternating current loss of the superconducting cable in the CICC superconducting conductor joint box is characterized by comprising the following steps of: the method comprises the following steps: (1) and sub-cable shielding treatment: firstly, confirming the contact position of the surface of the superconducting cable and the copper surface in the superconducting joint box, and removing a stainless steel lace belt at the contact position to expose a plurality of sub-cables in the superconducting cable; then finding out the secondary cables appearing twice at the contact position, comparing the areas of the twice appearing parts of the secondary cables appearing twice, and selecting the part with smaller area as a shielding area; finally, wrapping the shielding area by using a polyimide belt; (2) and barrier treatment between sub cables: respectively inserting non-completely insulated barrier sheets between two adjacent sub-cables at the contact position in the step (1) to improve the resistance between the sub-cables and ensure that the sub-cables are not completely insulated;

the separation piece is a stainless steel separation piece, the stainless steel separation piece is inserted into the deep part of the gap between two adjacent sub-cables, and the stainless steel separation piece is completely embedded between the two sub-cables and is not exposed.

2. The method of reducing ac losses in a superconducting cable in a cic c superconducting conductor splice enclosure of claim 1, wherein: in the step (1), an auxiliary die is adopted to find a contact position, the auxiliary die is a rectangular body with a central through hole, the diameter of the central through hole is consistent with that of the superconducting cable, the size of the rectangular body is consistent with that of the copper surface in the superconducting cable joint box, the rectangular body is sleeved on the superconducting cable through the central through hole, a die window for exposing the superconducting cable is arranged on the side surface of the rectangular body, and the displayed part of the die window is the part of the surface of the superconducting cable in contact with the copper surface in the superconducting joint box.

3. The method of reducing ac losses in a superconducting cable in a cic c superconducting conductor splice enclosure of claim 1, wherein: in the step (1), a polyimide belt is wrapped in the shielding area in a 50% half-lap wrapping mode.

4. The method of claim 1, wherein the method comprises the following steps: the planar shape of the stainless steel blocking sheet is fan-shaped, and the thickness of the stainless steel blocking sheet is consistent with that of the sub-cable stainless steel patterned belt.

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