Superconducting cable device with liquid nitrogen communication vessel and method of operation

Abstract

The application belongs to the technical field of superconducting cables, and discloses a superconducting cable device containing a liquid nitrogen communication device and a working method. The terminal comprises a superconducting cable conductor, two terminal bodies, and the two terminal bodies are connected to two ends of the superconducting cable conductor. The terminal body comprises an outer Dewar for accommodating liquid nitrogen and the superconducting cable conductor. The outer Dewars of the two terminal bodies are connected to each other in a sealed manner through a cable conductor Dewar pipeline. The superconducting cable conductor extends along a preset laying path and has a height difference in different sections. The liquid nitrogen communication device is arranged at the cable terminal, the cable Dewar pipeline along the line, and the interval or the height difference change point. The traditional liquid nitrogen circulation mode faces challenges when the superconducting cable conductor has a drop along the laying path. In view of the characteristics, the core structure design of the terminal body, the liquid nitrogen communication device, and the gas-liquid double communication pipeline fundamentally solves the technical pain points of slow exhaust, difficult liquid supplement, and large pressure fluctuation when the existing superconducting cable device loses superconductivity.

Description

Technical Field

[0001] This invention belongs to the field of superconducting cable technology, and specifically relates to a superconducting cable device and its working method containing a liquid nitrogen communicator. Background Technology

[0002] Superconducting cables are a type of cable made using superconductors. They utilize the property of superconducting materials that their resistance disappears at low temperatures to achieve efficient power transmission. With their significant advantages such as large capacity, low loss, and environmental friendliness, superconducting cables have become an important development direction for next-generation urban power grid expansion and efficient power transmission technology. Their normal operation depends on a cryogenic environment maintained by supercooled liquid nitrogen.

[0003] Due to limitations imposed by terrain and urban planning, the paths of superconducting cables are often not horizontal, meaning there is a vertical height difference along the cable's laying direction. In cable systems with significant height differences, the circulation of liquid nitrogen faces severe challenges.

[0004] Bubble buildup problem: Liquid nitrogen absorbs heat and produces gaseous nitrogen. In pipelines flowing from low to high, especially in the ascending section, buoyancy causes bubbles to easily accumulate at the highest points of the pipeline, forming "airlocks." Airlocks obstruct the normal flow of liquid nitrogen, reduce cooling efficiency, and prevent heat from being carried away in a timely manner in that area.

[0005] Local pressure and temperature changes: According to the principles of fluid statics, the static pressure of liquid nitrogen is higher at the lowest point of the cable and lower at the highest point. The decrease in static pressure leads to a decrease in the boiling point of liquid nitrogen, making it easier for the liquid nitrogen at the higher point to vaporize and exacerbating the formation of bubbles.

[0006] In existing technologies, forced circulation pumps are typically used to drive liquid nitrogen. However, simply increasing the pump power cannot effectively solve the problems of bubble accumulation at high points and uneven static pressure distribution. For some complex circuits, multiple independent cooling loops may be required, but this would significantly increase the system's complexity and cost.

[0007] Therefore, there is an urgent need for a solution specifically designed for superconducting cable systems with significant height differences, which can effectively dissipate air bubbles, balance static pressure, and ensure the uniformity and reliability of cooling throughout the cable line. Summary of the Invention

[0008] The purpose of this invention is to provide a superconducting cable device and its working method containing a liquid nitrogen connector, so as to solve the technical problems of existing superconducting cable systems being unable to effectively dissipate air bubbles and replenish liquid in a timely manner; it can also further solve the problems of high-point venting and static pressure balancing for superconducting cable systems with height differences.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a superconducting cable device containing a liquid nitrogen communicating vessel, comprising: The conductor of the superconducting cable is made of high-temperature superconducting material, extends along a predetermined laying path, and has height differences in different sections; Two terminal bodies, each terminal body including an outer Dewar for containing liquid nitrogen and a superconducting cable conductor; the outer Dewars of the two terminal bodies are sealed to each other through cable conductor Dewar pipes; the two terminal bodies are connected to both ends of a superconducting cable conductor; the internal space of the terminal body is divided into a top gas chamber and a liquid chamber from top to bottom, the liquid chamber being used to contain supercooled liquid nitrogen to cool the superconducting cable conductor therein; an outer interlayer of cable system insulation is provided on the outside of the outer Dewar; Several liquid nitrogen connectors, each comprising an upper gas phase space and a lower liquid phase space; the several liquid nitrogen connectors are divided into a first liquid nitrogen connector connected to the terminal body and a second liquid nitrogen connector connected to the cable conductor Dewar pipe; The gas connection pipeline is divided into a first gas connection pipeline connected to the first liquid nitrogen connector and a second gas connection pipeline connected to the second liquid nitrogen connector; one end of the first gas connection pipeline is connected to the top gas cavity of the corresponding terminal body, and the other end is connected to the upper gas phase space of the corresponding first liquid nitrogen connector, so that the corresponding pair of terminal bodies and the gas phase pressure in the first liquid nitrogen connector are kept consistent. The liquid connection pipeline is divided into a first liquid connection pipeline connected to the terminal body and a second liquid connection pipeline connected to the cable conductor Dewar pipe. One end of the first liquid connection pipeline is connected to the liquid cavity of the corresponding terminal body, and the other end is connected to the lower liquid phase space of the corresponding first liquid nitrogen connector, so that the liquid nitrogen in the corresponding pair of terminal bodies and the first liquid nitrogen connector can flow to each other. One end of the second liquid connection pipeline is connected to the cable conductor Dewar pipe, and the other end is connected to the lower liquid phase space of the corresponding second liquid nitrogen connector, so that the liquid nitrogen in the cable conductor Dewar pipe and the second liquid nitrogen connector can flow to each other. Several liquid nitrogen supply systems are connected to corresponding liquid nitrogen communication devices.

[0010] A further improvement of the present invention is that at least one pressure relief valve is provided at the connection point between the first air connection pipeline and the corresponding terminal body, and in the air cavity at the top of the terminal body.

[0011] A further improvement of the present invention is that: the second gas connection pipeline connected to the second liquid nitrogen connector is connected to the outer interlayer of the cable system insulation layer through a pressure relief valve; an outer interlayer pressure relief valve is provided on the outer interlayer of the cable system insulation layer; the outer interlayer of the cable system insulation layer is connected to the external atmosphere through the outer interlayer pressure relief valve.

[0012] A further improvement of the present invention is that the volume of the lower liquid phase space of the first liquid nitrogen connector is 10-30% of the volume of the corresponding terminal body liquid cavity.

[0013] A further improvement of the present invention is that the first liquid nitrogen communication device is fixed to the corresponding terminal body by a support frame.

[0014] A further improvement of the present invention is that the terminal body further includes a refrigerator, the cooling end of which extends into the liquid cavity to regulate the temperature of the liquid nitrogen in the liquid cavity.

[0015] A further improvement of the present invention is that the outer shells of both the terminal body and the liquid nitrogen connector are made of cryogenic Dewar that can withstand supercooled liquid nitrogen.

[0016] A further improvement of the present invention is that: along the laying path of the superconducting cable conductor, a second liquid nitrogen connector is provided, which is connected to the Dewar pipe of the cable conductor, according to the principle of equal spacing or at the point of change of height difference.

[0017] A further improvement of the present invention is that the minimum volume of each second liquid nitrogen communicating vessel is... The relationship between the height difference and the vertical drop is expressed as follows:

[0018] Where K is the safety factor, K ≥ 1.2; A is the equivalent cross-sectional area of ​​the liquid nitrogen flow channel inside the Dewar tube of the cable conductor; β is the average volumetric expansion coefficient of liquid nitrogen within its operating temperature range; ΔH is the maximum height difference within the section of the superconducting cable conductor laid along the second liquid nitrogen connector.

[0019] A further improvement of this invention is that the initial liquid nitrogen level in the liquid nitrogen connector and terminal body is set above the conductor portion of the superconducting cable. This design ensures that in the event of liquid nitrogen evaporation loss, the liquid level has sufficient buffer height before dropping to the exposed conductor, thereby maintaining the conductor continuously immersed in liquid nitrogen under most operating conditions and ensuring stable cooling.

[0020] A further improvement of this invention lies in that the cross-sectional area of ​​the liquid nitrogen connector is designed to be significantly larger than that of the liquid nitrogen pipeline at the top of the terminal body. Under the condition that both maintain gas-liquid communication and consistent liquid surface pressure, this cross-sectional difference allows the liquid nitrogen connector to form a liquid level buffer. Based on the principle of communicating vessels, when liquid nitrogen evaporation causes changes in the liquid volume within the smaller cross-sectional pipeline, the larger cross-sectional connector can maintain a stable overall liquid level in the system, thereby significantly suppressing the disturbance of the liquid surface caused by evaporation. Specifically, "significantly larger" means that the cross-sectional area of ​​the liquid nitrogen connector is twice or more than twice the cross-sectional area of ​​the liquid nitrogen pipeline at the top of the terminal body.

[0021] In a second aspect, the present invention provides a method for operating a superconducting cable device containing a liquid nitrogen communicator, comprising: The liquid nitrogen level in the terminal body and the first liquid nitrogen connector is kept at the same height by the combined action of the first gas connection pipeline and the first liquid connection pipeline; the terminal is in a state of static pressure balance. Alternatively, the heat generated by the superconducting cable losing its quench causes the liquid nitrogen in the terminal body's liquid chamber to boil violently, producing bubbles. These bubbles rise to the top gas chamber, and the high-pressure gas-liquid mixture enters the upper gas phase space of the first liquid nitrogen connector through the first gas connection pipeline. As the liquid nitrogen vaporizes, the liquid level in the terminal body begins to drop, and the liquid nitrogen in the lower liquid phase space, under the action of static pressure difference, automatically flows to the terminal body through the first liquid connection pipeline, achieving rapid emergency liquid replenishment. As the terminal pressure gradually returns to normal, the liquid nitrogen replenishment system replenishes liquid nitrogen into the first liquid nitrogen connector, and then restores the liquid level in the terminal body to normal through the first liquid connection pipeline. Alternatively, bubbles generated in the cable conductor Dewar pipe enter the top gas chamber of the second liquid nitrogen connector through the second liquid connection pipeline; the high-pressure gas-liquid mixture passes through the pressure relief valve at one end of the second gas connection pipeline to the second liquid nitrogen connector; and the pressure regulating device connected to the second liquid nitrogen connector maintains the liquid surface pressure consistent with the terminal body pressure, so that the gas phase pressure in the terminal body and the multiple second liquid nitrogen connectors are consistent.

[0022] Compared with the prior art, the present invention has the following unexpected beneficial effects: This invention provides a superconducting cable device containing liquid nitrogen connectors, comprising: a superconducting cable conductor made of high-temperature superconducting material, extending along a predetermined laying path and having height differences in different sections; two terminal bodies, each terminal body including an outer Dewar for accommodating liquid nitrogen and the superconducting cable conductor; the outer Dewars of the two terminal bodies are mutually sealed and connected through cable conductor Dewar pipes; the two terminal bodies are connected to both ends of a superconducting cable conductor; the internal space of the terminal body is divided from top to bottom into a top gas chamber and a liquid chamber, the liquid chamber being used to contain supercooled liquid nitrogen to cool the superconducting cable conductor therein; a plurality of liquid nitrogen connectors, each including an upper gas phase space and a lower liquid phase space; the plurality of liquid nitrogen connectors are divided into a first liquid nitrogen connector connected to the terminal body and a second liquid nitrogen connector connected to the cable conductor Dewar pipe; a gas connection pipeline, divided into a first gas connection pipeline connected to the first liquid nitrogen connector and a second gas connection pipeline connected to the second liquid nitrogen connector. One end of the first gas-connecting conduit is connected to the top gas cavity of the corresponding terminal body, and the other end is connected to the upper gas phase space of the corresponding first liquid nitrogen connector, so that the gas phase pressure of the corresponding pair of terminal bodies is consistent with that of the first liquid nitrogen connector; the liquid-connecting conduit is divided into a first liquid-connecting conduit connected to the terminal body and a second liquid-connecting conduit connected to the cable conductor Dewar conduit; one end of the first liquid-connecting conduit is connected to the liquid cavity of the corresponding terminal body, and the other end is connected to the lower liquid phase space of the corresponding first liquid nitrogen connector, so that the liquid nitrogen in the corresponding pair of terminal bodies and the first liquid nitrogen connector can flow to each other; one end of the second liquid-connecting conduit is connected to the cable conductor Dewar conduit, and the other end is connected to the lower liquid phase space of the corresponding second liquid nitrogen connector, so that the liquid nitrogen in the cable conductor Dewar conduit and the second liquid nitrogen connector can flow to each other; several liquid nitrogen replenishment systems are connected to the corresponding liquid nitrogen connectors. This invention fundamentally solves the technical pain points of existing superconducting cable terminals during quench failures—namely, slow venting, difficult liquid replenishment, and large pressure fluctuations—through the core structural design of the terminal body, liquid nitrogen connector, cable conductor Dewar, and gas-liquid dual-connection pipeline. During normal operation, the gas-liquid connection pipeline maintains static pressure balance between the terminal and the connector, ensuring a stable cryogenic environment. In the event of a quench failure, the gas connection pipeline provides a low-resistance, directional drainage channel for the bubbles generated by vaporization, preventing bubble accumulation in weak insulation areas and ensuring insulation strength. The liquid connection pipeline utilizes the static pressure difference to achieve rapid emergency liquid nitrogen replenishment, preventing the loss of the cryogenic environment inside the terminal. Simultaneously, the additional volume of the liquid nitrogen connector absorbs pressure shocks, reducing mechanical stress on the terminal body. The entire mechanism requires no external energy source, achieving simultaneous optimization of venting, liquid replenishment, and pressure buffering through a passive response, significantly improving the fault robustness and operational safety of the superconducting cable system.

[0023] Furthermore, this invention optimizes the bubble discharge path by placing both ends of the gas-connecting pipeline in the top region: the top of the gas chamber at the top of the terminal body is the core area where bubbles naturally accumulate; opening a port here allows for direct capture of the high-pressure gas-liquid mixture, reducing the residence time of bubbles inside the terminal; the top port of the upper gas phase space of the liquid nitrogen connector avoids obstruction of exhaust by the liquid nitrogen inside the connector, ensuring unobstructed exhaust channels throughout. This design improves bubble discharge efficiency, effectively avoids pressure superposition caused by obstructed exhaust paths, and further protects insulating components from bubble corrosion.

[0024] Furthermore, the port of the liquid-connected pipeline of the present invention is located in the bottom region, which can make maximum use of the gravity and static pressure difference characteristics of liquid nitrogen. This design ensures stable flow and sufficient replenishment during emergency liquid replenishment, avoids the low-temperature blind zone of "partial liquid absence" in the terminal liquid chamber, ensures that the superconducting cable conductor is in a low-temperature superconducting state throughout the process, and improves the rapid recovery capability after system failure.

[0025] Furthermore, this invention incorporates a pressure relief valve at the connection point of the gas-connected pipeline or in the top gas chamber, achieving dual protection of "active guidance + passive pressure relief": when a fault causes a sudden pressure surge, the pressure relief valve can open quickly, reducing the flow resistance of the gas-liquid mixture and guiding bubbles to be discharged preferentially through the connecting pipeline, preventing bubbles from diffusing into other areas inside the terminal; simultaneously, the pressure relief valve can limit the maximum safe pressure, preventing structural deformation or sealing failure of the terminal body due to excessive pressure. This design further optimizes the exhaust response speed, reduces pressure peaks, and improves the safety and service life of the terminal structure.

[0026] Furthermore, this invention limits the volume of the liquid phase space at the bottom of the liquid nitrogen connector to 10-30% of the volume of the liquid cavity of the terminal body, achieving an optimal balance between replenishment capacity and structural compactness. This quantitative design ensures that the connector provides sufficient replenishment reserves within a limited space, while avoiding liquid nitrogen waste and cost increases caused by excessive volume, and is suitable for superconducting cable terminal application scenarios of different power levels.

[0027] Furthermore, in this invention, the cooling end of the cryostat extends into the liquid chamber, allowing for real-time adjustment of the liquid nitrogen temperature to maintain it in a supercooled state, ensuring the stability of the superconducting performance of the superconducting cable conductor. After a fault requiring liquid replenishment, the cryostat can quickly cool the replenished liquid nitrogen to the set temperature, shortening the system recovery time. This design, together with the liquid nitrogen connector, forms a synergistic mechanism of cryogenic maintenance and emergency replenishment, solving the liquid replenishment problem during faults while ensuring cryogenic stability during normal operation and after recovery, further enhancing the continuity and reliability of system operation.

[0028] Furthermore, the outer shell of the terminal body and the liquid nitrogen connector in this invention is made of cryogenic Dewar ware. This material possesses excellent vacuum insulation performance and low-temperature resistance: on the one hand, it reduces heat exchange between liquid nitrogen and the external environment, reduces liquid nitrogen evaporation loss, and saves operating costs; on the other hand, it prevents the outer shell from shrinking and deforming due to low temperatures, ensuring sealing performance and preventing liquid nitrogen leakage. This design solves the insulation and structural sealing problems of cryogenic equipment, ensuring that the terminal maintains a stable low-temperature environment during long-term operation, while improving the safety and environmental friendliness of the equipment.

[0029] Furthermore, this invention includes two terminal bodies; the outer Dewars of the two terminal bodies are mutually sealed; the two terminal bodies are connected to both ends of a superconducting cable conductor; the superconducting cable conductor has a vertical drop, so that the liquid chamber of one of the two terminal bodies is higher than that of the other; a liquid nitrogen connector connects the lower of the two liquid chambers. The top gas chamber structures of the two terminal bodies are identical, and both are equipped with pressure relief valves, which facilitate the timely discharge of accumulated gas at the higher points of the two terminal bodies, avoiding the formation of "gas locks". Combined with the real-time liquid replenishment by the liquid nitrogen connector, it also solves the problem of uneven static pressure distribution and easy vaporization at higher points, which leads to reduced liquid nitrogen and the generation of bubbles. This ensures that the superconducting cable conductor operates continuously in a liquid nitrogen environment.

[0030] Furthermore, the minimum volume of each second liquid nitrogen communicating vessel in this invention... The relationship between the height difference and the vertical drop is expressed as follows:

[0031] Where K is the safety factor, K ≥ 1.2; A is the equivalent cross-sectional area of ​​the liquid nitrogen flow channel inside the Dewar tube 600 of the cable conductor; β is the average volumetric expansion coefficient of liquid nitrogen within its operating temperature range; ΔH is the maximum height difference within the section of the superconducting cable conductor laid along the second liquid nitrogen connector.

[0032] Furthermore, the present invention provides a method for operating a superconducting cable device containing a liquid nitrogen connector, comprising: the liquid nitrogen level in the terminal body and the liquid nitrogen connector is kept at the same height under the action of the liquid connecting pipeline; the terminal is in a static pressure equilibrium state; or, the heat generated by the superconducting cable losing its quench causes the liquid nitrogen in the liquid cavity of the terminal body to boil violently, generating bubbles; the bubbles rise to the top gas cavity, and the high-pressure gas-liquid mixture enters the upper gas phase space of the liquid nitrogen connector through the gas connecting pipeline; as the liquid nitrogen vaporizes, the liquid level in the terminal body begins to drop, and the liquid nitrogen in the lower liquid phase space flows automatically to the terminal body through the liquid connecting pipeline under the action of static pressure difference, realizing rapid emergency liquid replenishment; the terminal pressure gradually returns to normal, the liquid nitrogen replenishment system replenishes liquid nitrogen into the liquid nitrogen connector, and then the liquid level in the terminal body is restored to normal through the liquid connecting pipeline. This working method, based on the principle of communicating vessels, achieves fully automated control of the entire process from normal operation to fault response and recovery: static pressure balance during normal operation ensures system stability; during faults, the venting and liquid replenishment processes require no manual intervention or external energy input, shortening response time; during the recovery phase, the liquid level is rapidly reset through the coordination of the liquid nitrogen replenishment system and the communicating vessels. This method solves the problems of existing terminal fault handling relying on manual operation and delayed response, enabling the system to have autonomous fault response capabilities, improving the convenience of operation and maintenance and the reliability of superconducting cable systems, and reducing power outage losses caused by faults. Attached Figure Description

[0033] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of a superconducting cable device containing a liquid nitrogen communicator, provided as an embodiment of the present invention. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0035] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0036] Please see Figure 1 As shown, an embodiment of the present invention provides a superconducting cable device containing liquid nitrogen connectors, including a terminal body 100, a cable conductor Dewar tube 600, and a plurality of liquid nitrogen connectors 200.

[0037] The terminal body 100 is a cylindrical sealed structure, consisting of an outer Dewar 101, a room-temperature current lead 104, a superconducting cable conductor 105, a pressure relief valve 106, and a refrigerator 107. Its internal space is divided from top to bottom into a top gas chamber 102 and a liquid chamber 103. The superconducting cable conductor 105 is housed within the outer Dewar 101 and is electrically connected to conventional wires on the power grid side at the top of the terminal via the room-temperature current lead 104. The outer Dewar 101 of the terminal body 100 is filled with supercooled liquid nitrogen to ensure that the superconducting cable conductor 105 is in the low-temperature environment required for superconductivity. The refrigerator 107 is mounted on the outer Dewar 101, with its cooling end extending into the liquid chamber 103, and is used to regulate the temperature of the liquid nitrogen inside the outer Dewar 101.

[0038] The outer Dewar 101 of the two terminal bodies 100 and the cable conductor Dewar conduit 600 located in the middle are sealed to each other; the outer Dewar 101 of the two terminal bodies 100 and the cable conductor Dewar conduit 600 can be an integral sealing result, or sealed by mechanical or chemical means.

[0039] Two terminal bodies 100 share a single superconducting cable conductor 105. The internal space of each terminal body 100 is divided into a top gas chamber 102 and a bottom liquid chamber 103 from top to bottom. The bottom liquid chamber 103 is used to contain supercooled liquid nitrogen to cool the superconducting cable conductor 105. The superconducting cable conductor 105 has a drop along its laying path, and this embodiment can be applied to environments where a drop connection is required. A liquid nitrogen connector 200 connects the two bottom liquid chambers 103 at the lower elevation to ensure adequate liquid replenishment. The top gas chambers of the two terminal bodies 100 have identical structures and are equipped with pressure relief valves 106, which facilitate the timely discharge of accumulated gas at the higher points of the two terminal bodies 100, preventing the formation of "airlocks." Combined with the real-time liquid replenishment by the liquid nitrogen connector 200, this also solves the problem of uneven static pressure distribution and the tendency for vaporization at higher points to cause reduced liquid nitrogen and bubble formation, ensuring that the superconducting cable conductor 105 operates continuously in a liquid nitrogen environment.

[0040] The superconducting cable conductor 105 is made of high-temperature superconducting materials, such as YBCO (yttrium barium copper oxide) or BSCCO (bismuth strontium calcium copper oxide).

[0041] In this invention, the laying path of the superconducting cable conductor 105 has a drop in elevation, which further complicates the liquid replenishment process. In this embodiment, liquid nitrogen connectors 200, which are also equipped with Dewar pipes 600 connecting the cable conductor, are provided at equally spaced intervals or at points of height difference. The volume of the liquid nitrogen connector 200 connecting the cable conductor Dewar pipe 600 is determined based on the maximum height difference in its area. Through optimized design of the volume of the liquid nitrogen connector 200, the liquid nitrogen connector 200 provides protection for the entire cable section.

[0042] In one specific embodiment, the minimum volume of the liquid nitrogen connector 200 connecting the Dewar conduit 600 of the connecting cable conductor is... The relationship between the height difference and the vertical drop is expressed as follows:

[0043] Where K is the safety factor, K ≥ 1.2; A is the equivalent cross-sectional area of ​​the liquid nitrogen flow channel inside the Dewar tube 600 of the cable conductor; β is the average volumetric expansion coefficient of liquid nitrogen within its operating temperature range; ΔH is the maximum height difference within the section of the superconducting cable conductor laid along the second liquid nitrogen connector.

[0044] The liquid nitrogen connector 200 is connected to the terminal body 100: The liquid nitrogen connector 200 is fixedly installed on the outer side wall of the outer Dewar 101 of the terminal body 100. The liquid nitrogen connector 200 is also a cryogenic Dewar, which is divided into two chambers: the upper chamber 202 is a gas chamber and the lower chamber 203 is a liquid chamber.

[0045] Gas connection pipeline: One port 301 of the gas connection pipeline 300 is opened at the top of the top gas chamber 102 of the terminal body 100, and the other port 302 is opened at the top of the upper chamber 202 of the liquid nitrogen connector 200. The gas connection pipeline 300 ensures that the terminal body 100 and the upper gas phase space of the liquid nitrogen connector 200 are connected, and the pressure remains consistent at all times.

[0046] Liquid connection pipeline: One end of the liquid connection pipeline 500 is located at the bottom of the liquid cavity 103 of the terminal body 100, and the other end is located at the bottom of the liquid cavity 203 of the liquid nitrogen connector 200. The liquid connection pipeline 500 ensures communication between the lower liquid phase space of the terminal body 100 and the liquid nitrogen connector 200.

[0047] Liquid nitrogen connector 200 connected to cable conductor Dewar conduit 600: Gas phase connection pipeline: One end of the gas phase connection pipeline 300 is connected to the external atmosphere through the pressure relief valve 106, and the other end is connected to the upper gas phase space of the liquid nitrogen connector 200. Through the pressure regulating device, the liquid level pressure is kept consistent with the pressure of the terminal body 100, so that the gas phase pressure in the terminal body 100 and the multiple liquid nitrogen connectors 300 connected to the cable conductor Dewar pipes are all consistent.

[0048] Liquid connection pipeline: One end of the liquid connection pipeline 500 is connected to the liquid cavity 103 of the corresponding terminal body 100, and the other end is connected to the lower liquid phase space of the corresponding liquid nitrogen communication device 200, so that the corresponding pair of terminal bodies 100 and the liquid nitrogen in the liquid nitrogen communication device 200 can flow to each other. In one specific embodiment, a one-way pressure relief valve 106 may be provided at the opening of the upper connecting pipe 301 within the terminal body 100, which is used to guide the air bubbles to be discharged to the outside of the outer Dewar 101 through the one-way pressure relief valve 106 first, thereby further optimizing the exhaust efficiency.

[0049] In one specific embodiment, an outer interlayer 700 for cable system insulation is provided on the outer side of the outer Dewar 101; the second gas connection pipeline connected to the second liquid nitrogen connector is connected to the outer interlayer 700 for cable system insulation via a pressure relief valve 106; an outer interlayer pressure relief valve 701 is provided on the outer interlayer 700 for cable system insulation; the outer interlayer 700 for cable system insulation is connected to the external atmosphere via the outer interlayer pressure relief valve 701. This invention introduces liquid nitrogen or cryogenic nitrogen gas ejected from the pressure relief valve 106 of the superconducting cable system into the outer interlayer 700 for superconducting cable system insulation, which helps to reduce the external temperature of the pipeline, reduce the temperature gradient inside and outside the vacuum tube, and reduce the overall cooling power of the system.

[0050] In one specific embodiment, the volume of the lower chamber 203 of the liquid nitrogen connector 200 is not less than 10-30% of the volume of the liquid chamber 104 of the terminal body 100, for example 10%, 20% or 30%, preferably 20%, to ensure sufficient emergency liquid replenishment capacity.

[0051] In summary, this embodiment provides a superconducting cable device with a liquid nitrogen connector. Through a cleverly designed liquid nitrogen connector, the insulation and thermal stability problems of superconducting cable terminals under fault conditions are efficiently solved in a completely passive manner without the need for external energy, significantly improving the reliability and safety of the system.

[0052] This invention discloses a superconducting cable device containing a liquid nitrogen communicating vessel, overcoming the shortcomings of existing superconducting cable terminals under fault conditions. Utilizing the communicating vessel principle, it enables the rapid and automatic discharge of air bubbles within the terminal, preventing bubble accumulation from compromising insulation strength. When the terminal experiences a sudden drop in liquid nitrogen due to quench loss, the communicating vessel allows for rapid replenishment of liquid nitrogen, preventing the loss of the cryogenic environment and protecting the terminal structure. This design effectively mitigates pressure fluctuations within the terminal during faults, enhancing the robustness and self-recovery capability of the superconducting cable system in the face of short-circuit faults.

[0053] This invention discloses a superconducting cable device containing a liquid nitrogen connector, which can actively vent gas and enhance insulation reliability: by setting up a dedicated pressure balance and venting channel, it can provide a low-resistance directional flow path for the bubbles when the superheat is lost and gas is generated, effectively preventing the bubbles from accumulating in the high-voltage electric field area, and fundamentally avoiding the problem of reduced insulation strength caused by bubbles.

[0054] This invention discloses a superconducting cable device containing a liquid nitrogen connector, which can quickly replenish liquid and maintain a low-temperature environment: when the liquid nitrogen at the bottom of the liquid nitrogen connector drops due to evaporation inside the terminal, liquid nitrogen can be quickly replenished to the terminal body by relying on the static pressure difference, ensuring that the core part of the superconducting cable is always immersed in the low-temperature medium and guaranteeing the system's rapid self-recovery capability.

[0055] This invention discloses a superconducting cable device containing a liquid nitrogen communicating vessel, which has a simple structure and a passive and reliable response: the entire mechanism is based on fluid mechanics and the principle of communicating vessels, requiring no additional active control components or external energy input, and is structurally reliable and responds quickly, perfectly meeting the stringent requirements for system robustness under fault conditions.

[0056] The present invention provides a superconducting cable device with a liquid nitrogen connector, which provides pressure buffering and improves system stability: the liquid nitrogen connector acts as an additional buffer volume, which can absorb and suppress pressure shocks generated during faults, reduce the instantaneous mechanical stress borne by the terminal body, and extend the equipment life.

[0057] This invention provides a method for operating a superconducting cable device containing a liquid nitrogen communicator, comprising the following steps: 1) During normal operation: The liquid nitrogen levels in the terminal body 100 and the liquid nitrogen communicating vessel 200 are maintained at the same height due to the communicating vessel principle. The system is in a state of static pressure equilibrium.

[0058] 2) When a fault overrun occurs: ① Exhaust Process: The large amount of heat generated by the superconducting cable losing its quench causes the liquid nitrogen in the liquid chamber 103 of the terminal body 100 to boil violently, generating bubbles. The bubbles rise to the top gas chamber 102, causing a sudden increase in pressure there. Because the gas-liquid connection pipe 300 provides a passage, the high-pressure gas-liquid mixture quickly enters the upper chamber 202 of the liquid nitrogen connector 200 through the gas-liquid connection pipe 300. This design provides the bubbles with a low-resistance exhaust path superior to the internal insulation surface of the terminal, effectively forcing the bubbles away from the weak insulation area and ensuring insulation strength.

[0059] ② Liquid replenishment and pressure buffering process: As liquid nitrogen vaporizes, the liquid level inside the terminal body 100 begins to drop. At this time, under the action of static pressure difference, the liquid nitrogen in the lower chamber 203 of the liquid nitrogen connector 200 automatically flows to the terminal body 100 through the liquid connector pipeline 500, achieving rapid emergency liquid replenishment. Simultaneously, the entire internal space of the liquid nitrogen connector 200 acts as an additional buffer volume, effectively absorbing pressure shocks and preventing the terminal body 100 from experiencing excessive mechanical stress.

[0060] ③ After the fault is cleared: The system pressure gradually returns to normal, and the vaporized nitrogen can be slowly discharged through the pressure relief valve 106 preset on the terminal body 100 or the communicating vessel. The liquid nitrogen supply system 400 starts to work, first replenishing liquid nitrogen into the liquid nitrogen communicating vessel 200, and then restoring the liquid level of the terminal body 100 to normal through the principle of the communicating vessel.

[0061] The present invention discloses a method for operating a superconducting cable device containing a liquid nitrogen connector. When bubbles are generated inside the terminal due to quench loss, a liquid nitrogen connector connected to the gas phase space at the top of the terminal provides a drainage path for the bubbles that is preferred over the internal insulation surface of the terminal, thereby forcing the bubbles to be discharged.

[0062] The present invention discloses a method for operating a superconducting cable device containing a liquid nitrogen connector. When the liquid level inside the terminal drops, liquid nitrogen is automatically replenished into the terminal based on the static pressure difference through a liquid nitrogen connector that is connected to the liquid phase space at the bottom of the terminal.

[0063] The present invention discloses a working method for a superconducting cable device containing a liquid nitrogen communicating vessel, which utilizes the principle of communicating vessels to passively and synchronously achieve directional discharge of bubbles and emergency replenishment of liquid nitrogen through the same device.

[0064] Compared with existing technologies, the superconducting cable device containing a liquid nitrogen connector of this invention demonstrates significant differences and substantial progress in both structural design and functional implementation. Specifically, the superconducting cable system disclosed in existing technologies CN112350267A and the paper "Design and Analysis of Four Different Current Leads for Superconducting DCEnergy Pipeline" (published in IEEE Transactions on Applied Superconductivity, Vol. 30, No. 4, June 2020) has its liquid nitrogen chamber designed to be connected to a liquid nitrogen interlayer located near the cable terminal. However, this interlayer essentially only serves as a closed storage space and is not connected to the core liquid nitrogen flow area of ​​the superconducting cable system—namely, the terminal and the cable conductor Dewar conduit. Under this structure, liquid nitrogen cannot flow or exchange throughout the system, and can only play a role in static insulation and local cooling. It cannot rapidly replenish liquid nitrogen to critical areas (such as the terminal and conductor) to restore the cryogenic environment when the superconducting cable loses its quench or faces other emergency conditions.

[0065] In contrast, the superconducting cable device with a liquid nitrogen connector proposed in this invention features significantly optimized design and enhanced functionality. The liquid nitrogen chamber of this invention is directly connected to the superconducting cable terminal and the cable conductor Dewar conduit via a specially designed connecting pipe, thus constructing a complete liquid nitrogen flow loop. This structure allows liquid nitrogen to circulate continuously throughout the entire superconducting cable system. In the event of quench failure or an emergency, liquid nitrogen can be rapidly delivered to the affected area, effectively suppressing temperature rise, ensuring the safe operation of the superconducting tape, and significantly enhancing the system's thermal stability and emergency response capabilities. In contrast, the closed liquid nitrogen chamber in existing technology CN112350267A and the paper "Design and Analysis of Four Different Current Leads for Superconducting DC Energy Pipeline" is completely isolated from the main liquid nitrogen flow area, unable to support dynamic liquid nitrogen exchange, and therefore lacks the aforementioned emergency liquid replenishment function. This significantly limits the system's adaptability and safety in the face of sudden heat loads.

[0066] Furthermore, the structure of this invention is particularly suitable for superconducting cable systems with significant height differences. In traditional enclosed designs, height differences often obstruct the natural convection of liquid nitrogen, affecting cooling performance. This invention, by connecting the liquid nitrogen chamber to the liquid nitrogen flow area, establishes a pressure-driven liquid nitrogen flow mechanism. Even in complex terrain or long-distance laying conditions, it can maintain stable circulation and rapid replenishment of liquid nitrogen, thereby further enhancing the system's adaptability and reliability in practical engineering environments.

[0067] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A superconducting cable device containing a liquid nitrogen communicating vessel, characterized in that, include: The superconducting cable conductor (105) is made of high-temperature superconducting material, extends along a predetermined laying path and has height differences in different sections; Two terminal bodies (100) are provided, each including an outer Dewar (101) for containing liquid nitrogen and a superconducting cable conductor (105); the outer Dewars (101) of the two terminal bodies (100) are sealed to each other through a cable conductor Dewar tube (600); the two terminal bodies (100) are connected to both ends of a superconducting cable conductor (105); the internal space of the terminal body (100) is divided from top to bottom into a top air chamber (102) and a liquid chamber (103), the liquid chamber (103) being used to contain supercooled liquid nitrogen to cool the superconducting cable conductor (105) therein; an outer interlayer (700) for cable system insulation is provided on the outside of the outer Dewar (101); A plurality of liquid nitrogen connectors (200) are provided, each comprising an upper gas phase space and a lower liquid phase space. The plurality of liquid nitrogen connectors (200) are divided into a first liquid nitrogen connector connected to a terminal body (100) and a second liquid nitrogen connector connected to a cable conductor Dewar pipe (600). The gas connection pipeline (300) is divided into a first gas connection pipeline connected to the first liquid nitrogen connector and a second gas connection pipeline connected to the second liquid nitrogen connector; one end of the first gas connection pipeline is connected to the top gas cavity (102) of the corresponding terminal body (100), and the other end is connected to the upper gas phase space of the corresponding first liquid nitrogen connector, so that the corresponding pair of terminal bodies (100) and the gas phase pressure in the first liquid nitrogen connector are kept consistent; The liquid connection pipeline (500) is divided into a first liquid connection pipeline connected to the terminal body (100) and a second liquid connection pipeline connected to the cable conductor Dewar pipe (600). One end of the first liquid connection pipeline is connected to the liquid cavity (103) of the corresponding terminal body (100), and the other end is connected to the lower liquid phase space of the corresponding first liquid nitrogen connector, so that the corresponding pair of terminal bodies (100) and the liquid nitrogen in the first liquid nitrogen connector can flow to each other. One end of the second liquid connection pipeline is connected to the cable conductor Dewar pipe (600), and the other end is connected to the lower liquid phase space of the corresponding second liquid nitrogen connector, so that the cable conductor Dewar pipe (600) and the liquid nitrogen in the second liquid nitrogen connector can flow to each other. Several liquid nitrogen supply systems (400) are connected to corresponding liquid nitrogen connectors (200).

2. The superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: At the connection point between the first air connection pipeline and the corresponding terminal body (100), and in the top air chamber (102) of the terminal body (100), at least one pressure relief valve (106) is provided.

3. The superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: The second gas connection pipeline connected to the second liquid nitrogen connector is connected to the outer interlayer (700) of the cable system insulation layer through a pressure relief valve (106); the outer interlayer (700) of the cable system insulation layer is provided with an outer interlayer pressure relief valve (701); the outer interlayer (700) of the cable system insulation layer is connected to the external atmosphere through the outer interlayer pressure relief valve (701).

4. The superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: The volume of the lower liquid phase space of the first liquid nitrogen connector is 10-30% of the volume of the liquid cavity (103) of the corresponding terminal body (100).

5. A superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: The first liquid nitrogen connector is fixed to the corresponding terminal body (100) by a support frame.

6. The superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: The terminal body (100) also includes a refrigerator (107), the cooling end of which extends into the liquid chamber (103) to regulate the temperature of liquid nitrogen in the liquid chamber (103).

7. A superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: The outer shells of the terminal body (100) and the liquid nitrogen connector (200) are both made of cryogenic Dewar that can withstand supercooled liquid nitrogen.

8. A superconducting cable device containing a liquid nitrogen communicating vessel according to claim 1, characterized in that: Along the laying path of the superconducting cable conductor (105), a second liquid nitrogen connector is provided, which is connected to the cable conductor Dewar pipe (600), according to the principle of equal spacing or at the point of change of height difference.

9. A superconducting cable device containing a liquid nitrogen communicating vessel according to claim 8, characterized in that: Minimum volume of each second liquid nitrogen communicating vessel The relationship between the height difference and the vertical drop is expressed as follows: Where K is the safety factor, K ≥ 1.2; A is the equivalent cross-sectional area of ​​the liquid nitrogen flow channel inside the Dewar tube (600) of the cable conductor; β is the average volumetric expansion coefficient of liquid nitrogen within its operating temperature range; ΔH is the maximum height difference within the laying path section of the superconducting cable conductor (105) connected to the second liquid nitrogen connector.

10. A method of operating a superconducting cable device containing a liquid nitrogen communicator according to any one of claims 1 to 9, characterized in that, include: The terminal body (100) and the liquid nitrogen level in the first liquid nitrogen connector are kept at the same height under the combined action of the first gas connection pipeline and the first liquid connection pipeline; the terminal is in a static pressure balance state. Alternatively, the heat generated by the superconducting cable quenching causes the liquid nitrogen in the liquid chamber (103) of the terminal body (100) to boil violently, generating bubbles; the bubbles rise to the top gas chamber (102), and the high-pressure gas-liquid mixture enters the upper gas phase space of the first liquid nitrogen connector through the first gas connection pipeline; as the liquid nitrogen vaporizes, the liquid level in the terminal body (100) begins to drop, and the liquid nitrogen in the lower liquid phase space flows automatically to the terminal body (100) through the first liquid connection pipeline under the action of static pressure difference, realizing rapid emergency liquid replenishment; the terminal pressure gradually returns to normal, and the liquid nitrogen replenishment system replenishes liquid nitrogen into the first liquid nitrogen connector, and then restores the liquid level of the terminal body (100) to normal through the first liquid connection pipeline; Alternatively, the air bubbles generated in the cable conductor Dewar pipe (600) enter the top gas chamber (102) of the second liquid nitrogen connector through the second liquid connection pipe; the high-pressure gas-liquid mixture passes through the pressure relief valve (106) at one end of the second gas connection pipe to the second liquid nitrogen connector; through the pressure regulating device connecting the second liquid nitrogen connector, the liquid surface pressure is kept consistent with the pressure of the terminal body (100), so that the gas phase pressure in the terminal body (100) and the plurality of second liquid nitrogen connectors (300) are consistent.

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