CN114496457A - Horizontal Dewar high-temperature superconducting current lead structure and design method - Google Patents

Horizontal Dewar high-temperature superconducting current lead structure and design method Download PDF

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CN114496457A
CN114496457A CN202210225123.XA CN202210225123A CN114496457A CN 114496457 A CN114496457 A CN 114496457A CN 202210225123 A CN202210225123 A CN 202210225123A CN 114496457 A CN114496457 A CN 114496457A
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dewar
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voltage lead
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voltage
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CN114496457B (en
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方进
赵鑫
王金浩
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Beijing Jiaotong University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
    • H01F6/065—Feed-through bushings, terminals and joints
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

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Abstract

The invention discloses a horizontal Dewar high-temperature superconducting current lead structure and a design method, belonging to the technical field of superconducting power application, comprising the following steps: a dewar end cap mounted on the transformer; a high-voltage lead section and a low-voltage lead section are arranged on the Dewar end cover; the first end of the high-voltage lead segment is connected with the transformer through a first high-low voltage lead, the second end of the high-voltage lead segment is connected with a first high-temperature super-lead segment, and the first high-temperature super-lead segment is placed in liquid nitrogen of a liquid nitrogen cooler; the first end of the low-voltage lead segment is connected with the transformer through a second high-low voltage lead, the second end of the low-voltage lead segment is connected with a second high-temperature super-lead segment, and the second high-temperature super-lead segment is arranged in liquid nitrogen of a liquid nitrogen cooler. The invention has simple structure, excellent heat conductivity, insulating property and heat dissipation performance, obviously optimizes the distribution of a thermal field, realizes the aim of reducing the heat leakage of the current lead by optimizing an objective function, and provides reliable support for the subsequent current lead design.

Description

Horizontal Dewar high-temperature superconducting current lead structure and design method
Technical Field
The invention belongs to the technical field of superconducting power application, and particularly relates to a horizontal Dewar high-temperature superconducting current lead structure and a design method.
Background
The high-temperature superconducting current lead has the advantages of large transmission power, high current density, low loss, environmental friendliness and the like, and is mainly used for supplying power to a superconducting magnet working in a low-temperature environment. Compared with the conventional copper current lead, the high-temperature superconducting section of the high-temperature superconducting current lead has no ohmic heat, the heat conductivity of the high-temperature superconducting section is much smaller than that of copper, and the heat leakage through the conduction of the high-temperature superconducting section is very small.
In the prior art, the current leads are often designed in a heat exchanger-like manner in order to minimize the heat leakage through the current leads to the cryogenic vessel, the current leads being made of different materials with different minimum heat leakages. At present, no current lead structure and design method which can enable the heat leakage of the lead to be close to the minimum value by changing the size of the current lead on the basis of given materials exist.
Disclosure of Invention
In order to solve the technical problem, the invention adopts the following technical scheme:
a horizontal Dewar high temperature superconducting current lead structure for a coaxial horizontal transformer, the horizontal Dewar high temperature superconducting current lead structure comprising:
a dewar end cap mounted on the transformer;
the Dewar end cover is provided with a high-voltage lead section and a low-voltage lead section;
the first end of the high-voltage lead section is connected with the transformer through a first high-voltage lead and a first low-voltage lead, the second end of the high-voltage lead section is connected with a first high-temperature super-lead section, and the first high-temperature super-lead section is placed in liquid nitrogen of a liquid nitrogen cooler;
the first end of the low-voltage lead section is connected with the transformer through a second high-low voltage lead, the second end of the low-voltage lead section is connected with a second high-temperature super-lead section, and the second high-temperature super-lead section is placed in liquid nitrogen of a liquid nitrogen cooler.
Further, the high-voltage lead section comprises a Dewar high-voltage lead, a Dewar high-voltage lead sleeve and a Dewar lead adapter, the Dewar lead adapter is sleeved outside the Dewar high-voltage lead sleeve, a first end of the Dewar lead adapter is fixedly connected with a non-end part of the Dewar high-voltage lead sleeve in a sealing manner, and a second end of the Dewar lead adapter extends to the outside of the first end of the Dewar high-voltage lead sleeve; a glass fiber reinforced plastic plug is arranged at the second end of the Dewar type lead connecting pipe, and a sealing joint is arranged at the second end of the Dewar type high-voltage lead bushing, so that a first closed space is formed in the Dewar type lead connecting pipe and the Dewar type high-voltage lead bushing; the Dewar high-voltage lead is positioned in the Dewar high-voltage lead sleeve, and two ends of the Dewar high-voltage lead respectively extend to the outer sides of the glass fiber reinforced plastic plug and the sealing joint to form two connecting ends; a first vacuumizing assembly is arranged on the outer side of the Dewar lead connecting pipe and communicated with the first closed space; dewar high pressure lead flange is equipped with to Dewar lead pipe outside cover, Dewar high pressure lead flange be used for with Dewar end cover fixed connection.
Furthermore, the low-voltage lead section comprises a Dewar low-voltage lead, a Dewar low-voltage lead sleeve, a Dewar low-voltage lead inner tube and a Dewar low-voltage lead outer tube, wherein the Dewar low-voltage lead inner tube is sleeved outside the Dewar low-voltage lead sleeve, two ends of the Dewar low-voltage lead inner tube and two ends of the Dewar low-voltage lead sleeve are respectively provided with a Dewar low-voltage lead flange and a Dewar low-voltage lead plug, a second closed space is formed among the Dewar low-voltage lead flange, the Dewar low-voltage lead plug, the Dewar low-voltage lead inner tube and the Dewar low-voltage lead sleeve, a second vacuumizing assembly is arranged outside the Dewar low-voltage lead inner tube, and the second vacuumizing assembly is communicated with the second closed space; the outer Dewar low-voltage lead pipe is sleeved outside the inner Dewar low-voltage lead pipe; two ends of the outer Dewar low-voltage lead pipe are fixedly connected with the inner Dewar low-voltage lead pipe through a single-sided flange of the Dewar low-voltage lead pipe, and a third closed space is formed; a third vacuumizing assembly is arranged on the outer side of the outer tube of the Dewar low-voltage lead and is communicated with the third closed space; the second closed space and the third closed space are independently arranged; the Dewar low-voltage lead is positioned in the Dewar low-voltage lead sleeve, and two ends of the Dewar low-voltage lead respectively extend to the outer sides of a Dewar low-voltage lead flange and a Dewar low-voltage lead pipe plug to form two connecting ends; the outer side of the outer pipe of the Dewar low-voltage lead is provided with a low-voltage lead screw joint, and the low-voltage lead screw joint is used for being fixedly connected with the Dewar end cover.
The design method of the horizontal Dewar high-temperature superconducting current lead structure comprises the following steps:
s10, determining the lengths of the Dewar high-voltage lead and the Dewar low-voltage lead;
s20, measuring the outer diameters of the Dewar high-voltage lead and the Dewar low-voltage lead, and determining the inner diameters of the Dewar high-voltage lead and the Dewar low-voltage lead according to the known rated current; meanwhile, the radiuses and the lengths of the Dewar high-voltage lead and the Dewar low-voltage lead are optimized to obtain the optimal length-diameter ratio so as to realize the minimum heat leakage.
Further, the specific steps of optimizing the radii and lengths of the dewar high-voltage lead and the dewar low-voltage lead in step S20 to obtain the optimal aspect ratio are as follows:
s21, according to the requirements of conductivity and heat conductivity, copper is used as a unitary current lead to reduce the Joule heat caused by the heat transfer current, and a Dewar type sleeve is used for cooling to achieve the purpose of reducing heat leakage;
s22, because the length is far larger than the radius of the cross section of the Dewar type heat collector, and meanwhile, if no temperature difference exists on the cross section, the radius is adopted as an invariant, and the lengths of the Dewar type high-voltage lead and the Dewar type low-voltage lead are changed to analyze heat leakage; theoretical analysis was performed by the following formula:
Figure BDA0003535379630000031
Figure BDA0003535379630000032
where ρ and κ are the thermal conductivity and resistivity of the copper lead, respectively;
is derived from
Figure BDA0003535379630000033
The length to section ratio at this time is known from the minimum heat leakageIs composed of
Figure BDA0003535379630000034
When T isj＝77K ThWhen the temperature is 300K, the length-cut ratio with the minimum heat leakage is obtained;
in the formula, QgenJoule heat, Q heat transfer, (Q)2)minFor minimum heat conduction, L is the length of the lead, A is the cross-sectional area of the lead, ThIs the temperature at the upper end of the lead, TjIs the cold end temperature;
wherein the current density is usually 5-6A/mm2(ii) a And the Dewar high-voltage lead and the Dewar low-voltage lead are designed into a thread type according to the heat conduction principle in the rib wall.
Further, the method also comprises the design steps of the high-temperature superconducting lead, and the specific steps are as follows:
s31, determining a high-temperature superconducting material of the high-temperature superconducting wire section, wherein the high-temperature superconducting material selects a YBCO superconducting tape;
s32, spreading a superconducting tape outside the metal rod, and fixing the high-temperature superconducting current lead section by using a clamping device to prevent shrinkage in the cooling process;
s33, arranging two ends of the high-temperature super-lead wire segment into a flat shape, and performing insulation protection on the outer side of the high-temperature super-lead wire segment by using an epoxy insulation cylinder;
s34, the thermal field model of the high-temperature super-guide line section satisfies the following relational expression:
Figure BDA0003535379630000041
wherein rho is the density of the high-temperature super-guide line section material;
cp is the constant pressure heat capacity of the high-temperature superconductive wire section material;
mu is the flow speed of the fluid outside the high-temperature superconducting lead section;
q is the heat flux of the high temperature superconductive wire section;
k is the thermal conductivity of the high-temperature superconductive wire section material;
Figure BDA0003535379630000042
is a gradient operator;
t is the temperature of the high-temperature superconductive wire section;
qe is the joule heating loss of the current lead;
s35, the electric field model of the high-temperature super-guide line section satisfies the following relational expression:
J＝σE+Je
Figure BDA0003535379630000043
Qe＝J·E
j is the current density of the high temperature superconducting wire segment;
Jethe ratio of the current of the high-temperature super-lead wire section to the lead wire section;
e is the electric field density of the high-temperature super-guide line section;
v is the potential of the high temperature superconductive wire section;
sigma is the conductivity of the high-temperature super-guide line section material;
Qejoule heating loss for high temperature over-leader segments;
s36, based on the coupling model of the thermal field and the electric field of the high-temperature superconducting wire segment, determining the length-diameter ratio of the high-temperature superconducting segment according to the simulation structure by adopting a simulation means and taking the minimum heat leakage of the current lead as an objective function, so as to optimize the length-diameter ratios of the Dewar high-voltage lead, the Dewar low-voltage lead and the high-temperature superconducting lead.
Further, the method also comprises an assembly design method of the high-voltage lead section, and the method comprises the following specific steps:
s41, adopting a G10 thread design for the glass fiber reinforced plastic plug, screwing the glass fiber reinforced plastic plug and a Dewar high-voltage lead wire, and injecting low-temperature glue;
s42, sleeving an epoxy sleeve with the thickness of 6mm outside the Dewar high-voltage lead as the Dewar high-voltage lead sleeve for insulation protection;
s43, sleeving a first Dewar made of AiSi304 stainless steel materials outside the epoxy sleeve to serve as a Dewar lead connecting pipe, and nesting and fixing to reduce heat leakage;
s44, the first vacuum-pumping component consists of a KF25 vacuum nozzle seat and a vacuum nozzle cap made of stainless steel 304 and a DN12 vacuum plug made of S30408, the interior of the high-voltage lead segment is ensured to be in a vacuum state, and the first vacuum-pumping component is fixed on the Dewar high-voltage lead connecting pipe;
s45, fixing the Dewar high-pressure lead connecting pipe by a Dewar high-pressure lead flange designed by AiSi304 material, and simultaneously adopting a sealing ring and glue to perform better sealing and connection.
Further, the method also comprises an assembly design method of the low-voltage lead section, and the method comprises the following specific steps:
s51, the Dewar low-voltage lead is made of a copper material and is in a threaded shape, and one end of the Dewar low-voltage lead is in a flat shape so as to be fixedly connected with the high-temperature superconducting lead section;
s52, sleeving an epoxy sleeve with the thickness of 1-2 mm outside the Dewar low-voltage lead for insulation protection;
s53, sleeving a lead Dewar on the outer part of the epoxy sleeve, fixing one side close to the high-temperature super-lead segment by using a Dewar low-voltage lead pipe plug, and fixing and insulating the Dewar low-voltage lead by using a glass fiber reinforced plastic inner and outer threaded connector at the outlet end of the other side;
s54, nesting a lead Dewar and a Dewar low-voltage lead connecting pipe, wherein the Dewar low-voltage lead connecting pipe is respectively composed of an inner Dewar low-voltage lead pipe made of 316 stainless steel materials of AiSi type and an outer Dewar low-voltage lead pipe made of AiSi304 materials; because of different materials, the material is assembled in a nested manner;
s55, the glass fiber reinforced plastic internal and external threaded joints and the low-voltage lead inner tube are fixedly connected through a Dewar low-voltage lead flange made of AiSi 304; wherein, the Dewar low-pressure lead flange is a thread flange;
s56, connecting the Dewar low-voltage lead screw joint to the Dewar low-voltage lead outer tube;
the S57, the second vacuumizing assembly and the third vacuumizing assembly are composed of a KF25 vacuumizing nozzle seat and a vacuum nozzle cap made of stainless steel 304 and a DN12 vacuumizing plug made of S30408 material so as to ensure that the interior of the Dewar low-voltage lead and the inner and outer tubes of the Dewar low-voltage lead are in a vacuum state, and the second vacuumizing assembly and the third vacuumizing assembly are respectively welded on the inner tube of the Dewar low-voltage lead and the outer tube of the Dewar low-voltage lead.
Has the advantages that:
the horizontal Dewar high-temperature superconducting current lead structure and the design method provided by the invention have the advantages that the current lead adopts an internal hollow groove type structure, the structure is simple, the heat conductivity, the insulating property and the heat dissipation performance are excellent, the distribution of a thermal field is obviously optimized, the goal of reducing the heat leakage of the current lead is realized by optimizing an objective function, and the reliable support is provided for the subsequent current lead design; the current lead adopting the structure is easy to process, manufacture, install and overhaul and is beneficial to engineering popularization and application.
Drawings
FIG. 1 is a schematic view of a horizontal Dewar high temperature superconducting current lead structure according to the present invention;
FIG. 2 is a schematic structural view of a Dewar end cap;
FIG. 3 is a schematic diagram of a high voltage lead segment;
FIG. 4 is a structural elevation view of a high voltage lead segment;
FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4;
FIG. 6 is a schematic diagram of a low voltage lead segment;
FIG. 7 is a structural elevation view of a low voltage lead segment;
FIG. 8 is a cross-sectional view taken along line B-B of FIG. 7;
FIG. 9 is a high and low voltage lead configuration view;
FIG. 10 is a view of a high temperature superconducting current lead;
FIG. 11 is an epoxy insulation can;
wherein, 1, a Dewar end cover; 2. a high voltage lead section; 21. a Dewar high voltage lead; 22. a Dewar high voltage lead bushing; 23. a Dewar lead adapter; 24. a glass fiber reinforced plastic plug; 25. sealing the joint; 26. a first sealed connection joint; 27. a dewar high voltage lead flange; 28. a first vacuum pumping assembly; 3. a low voltage lead segment; 31. a Dewar low voltage lead; 32. a Dewar low voltage lead bushing; 33. an inner tube of a Dewar low-voltage lead; 34. an outer Dewar low-voltage lead tube; 35. a Dewar low voltage lead flange; 36. a second sealed connection joint; 37. a third vacuum pumping assembly; 38. a single-sided flange of a Dewar low-voltage lead; 39. a Dewar low voltage lead plug; 310. a low voltage lead nipple; 311. a second vacuum pumping assembly; 4. a first high-low voltage lead; 5. a first high temperature superconductive wire section; 6. an epoxy insulating cylinder.
Detailed Description
Example 1
Referring to fig. 1 to 11, a horizontal type dewar high temperature superconducting current lead structure for a coaxial horizontal transformer, the horizontal type dewar high temperature superconducting current lead structure comprising:
a Dewar end cap 1 mounted on the transformer;
a high-voltage lead section 2 and a low-voltage lead section 3 are arranged on the Dewar end cover 1;
the first end of the high-voltage lead segment 2 is connected with the transformer through a first high-low voltage lead 4, the second end of the high-voltage lead segment 2 is connected with a first high-temperature super-lead segment 5, and the first high-temperature super-lead segment 5 is placed in liquid nitrogen of a liquid nitrogen cooler;
the first end of the low-voltage lead segment 3 is connected with the transformer through a second high-low voltage lead, the second end of the low-voltage lead segment 3 is connected with a second high-temperature super lead segment, and the second high-temperature super lead segment 5 is placed in liquid nitrogen of a liquid nitrogen cooler, wherein the second high-low voltage lead and the first high-low voltage lead 4 are consistent in structure; the second high temperature superconductive wire section is identical in structure to the first high temperature superconductive wire section 5.
In this embodiment, the high-voltage lead segment 2 includes a dewar high-voltage lead 21, a dewar high-voltage lead bushing 22 and a dewar lead adapter 23, the dewar lead adapter 23 is sleeved on the outside of the dewar high-voltage lead bushing 22, wherein a first end of the dewar lead adapter 23 is fixedly connected to a non-end portion of the dewar high-voltage lead bushing 22 in a sealing manner, and a second end of the dewar lead adapter 23 extends to the outside of the first end of the dewar high-voltage lead bushing 22; a glass fiber reinforced plastic plug 24 is arranged at the second end of the Dewar type lead connecting pipe 23 (a first sealing connecting joint 26 is arranged inside the glass fiber reinforced plastic plug 24), and a sealing joint 25 is arranged at the second end of the Dewar type high-voltage lead bushing 22, so that a first closed space is formed inside the Dewar type lead connecting pipe 23 and the Dewar type high-voltage lead bushing 22; the Dewar high-voltage lead 21 is positioned in the Dewar high-voltage lead sleeve 22, and two ends of the Dewar high-voltage lead 21 respectively extend to the outer sides of the glass fiber reinforced plastic plug 24 and the sealing joint 25 to form two connecting ends; a first vacuumizing assembly 28 is arranged on the outer side of the Dewar lead connecting pipe 23, and the first vacuumizing assembly 28 is communicated with the first closed space; a Dewar high-voltage lead flange 27 is sleeved on the outer side of the Dewar lead connecting pipe 23, and the Dewar high-voltage lead flange 27 is used for being fixedly connected with the Dewar end cover 1.
In this embodiment, the low-voltage lead segment 3 includes a dewar low-voltage lead 31, a dewar low-voltage lead bushing 32, a dewar low-voltage lead inner tube 33 and a dewar low-voltage lead outer tube 34, wherein the dewar low-voltage lead inner tube 33 is sleeved on the outside of the dewar low-voltage lead bushing 32, two ends of the dewar low-voltage lead inner tube 33 and the dewar low-voltage lead bushing 32 are respectively provided with a dewar low-voltage lead flange 35 and a dewar low-voltage lead plug 39, and wherein a second sealing connection joint is provided in the dewar low-voltage lead flange 35. A second closed space is formed among the Dewar low-voltage lead flange 35, the Dewar low-voltage lead pipe plug 39, the Dewar low-voltage lead inner pipe 33 and the Dewar low-voltage lead sleeve 32, a second vacuumizing assembly 311 is arranged on the outer side of the Dewar low-voltage lead inner pipe 33, and the second vacuumizing assembly 311 is communicated with the second closed space; the outer Dewar low-voltage lead tube 34 is sleeved outside the inner Dewar low-voltage lead tube 33; two ends of the outer Dewar low-voltage lead pipe 34 are fixedly connected with the inner Dewar low-voltage lead pipe 33 through a single-sided Dewar low-voltage lead flange 38, and a third closed space is formed; a third vacuumizing assembly 37 is arranged on the outer side of the outer Dewar low-voltage lead pipe 34, and the third vacuumizing assembly 37 is communicated with a third closed space; the second closed space and the third closed space are independently arranged; the Dewar low-voltage lead 31 is positioned in the Dewar low-voltage lead sleeve 32, and two ends of the Dewar low-voltage lead 31 respectively extend to the outer sides of a Dewar low-voltage lead flange 35 and a Dewar low-voltage lead pipe plug 39 to form two connecting ends; the outer side of the outer Dewar low-voltage lead pipe 34 is provided with a low-voltage lead screw joint 310, and the low-voltage lead screw joint 310 is used for being fixedly connected with the Dewar end cover 1.
In this embodiment, the first vacuum assembly 28, the second vacuum assembly 311 and the third vacuum assembly 37 are KF25 vacuum nozzle seats and vacuum nozzle caps.
In this embodiment, the dewar high-voltage lead 21 and the dewar low-voltage lead 31 are copper leads, and the high-temperature superconducting wire section is a superconducting lead made of YBCO material.
In this embodiment, an epoxy insulation tube 6 is used for insulation protection outside the high temperature superconductive wire section.
Wherein the first vacuum-pumping assembly 28, the second vacuum-pumping assembly 311 and the third vacuum-pumping assembly 37 should be located at the side far from the transformer when being installed for use.
Example 2
The embodiment is a method for designing a horizontal dewar high temperature superconducting current lead structure provided in embodiment 1, including the steps of:
s10, determining the lengths of the Dewar high-voltage lead and the Dewar low-voltage lead;
s20, measuring the outer diameters of the Dewar high-voltage lead and the Dewar low-voltage lead, and determining the inner diameters of the Dewar high-voltage lead and the Dewar low-voltage lead according to the known rated current; meanwhile, the radius and the length of the Dewar high-voltage lead and the Dewar low-voltage lead are optimized to obtain the optimal length-diameter ratio so as to realize the minimum heat leakage.
In this embodiment, the specific steps of optimizing the radii and lengths of the dewar high-voltage lead and the dewar low-voltage lead in step S20 to obtain the optimal aspect ratio are as follows:
s21, according to the requirements of conductivity and heat conductivity, copper is used as a unitary current lead to reduce the Joule heat caused by the heat transfer current, and a Dewar type sleeve is used for cooling to achieve the purpose of reducing heat leakage;
s22, because the length is far larger than the radius of the cross section of the Dewar type heat collector, and meanwhile, if no temperature difference exists on the cross section, the radius is adopted as an invariant, and the lengths of the Dewar type high-voltage lead and the Dewar type low-voltage lead are changed to analyze heat leakage; theoretical analysis was performed by the following formula:
Figure BDA0003535379630000091
Figure BDA0003535379630000092
where ρ and κ are the thermal conductivity and resistivity of the copper lead, respectively;
is derived from
Figure BDA0003535379630000093
The length-to-section ratio at this time is known from the minimum heat leakage
Figure BDA0003535379630000094
When T isj＝77K ThWhen the temperature is 300K, the length-cut ratio with the minimum heat leakage is obtained;
in the formula, QgenJoule heat, Q heat transfer, (Q)2)minFor minimum heat conduction, L is the length of the lead, A is the cross-sectional area of the lead, ThIs the temperature at the upper end of the lead, TjIs the cold end temperature;
wherein the current density is usually 5-6A/mm2(ii) a And the Dewar high-voltage lead and the Dewar low-voltage lead are designed into a thread type according to the heat conduction principle in the rib wall.
In this embodiment, the method further includes a step of designing the high-temperature superconducting lead, which includes the following steps:
s31, determining a high-temperature superconducting material of the high-temperature superconducting wire segment, wherein the high-temperature superconducting material selects a YBCO superconducting tape;
s32, spreading a superconducting tape outside the metal rod, and fixing the high-temperature superconducting current lead section by using a clamping device to prevent shrinkage in the cooling process;
s33, arranging two ends of the high-temperature super-lead wire segment into a flat shape, and performing insulation protection on the outer side of the high-temperature super-lead wire segment by using an epoxy insulation cylinder;
s34, the thermal field model of the high-temperature super-guide line section satisfies the following relational expression:
Figure BDA0003535379630000101
wherein rho is the density of the high-temperature super-guide line section material;
cp is the constant pressure heat capacity of the high-temperature superconductive wire section material;
mu is the flow speed of the fluid outside the high-temperature superconducting lead section;
q is the heat flux of the high temperature super-lead segment;
k is the thermal conductivity of the high-temperature superconductive wire section material;
^ is a gradient operator;
t is the temperature of the high-temperature superconductive wire section;
qe is the joule heating loss of the current lead;
s35, the electric field model of the high-temperature super-guide line section satisfies the following relational expression:
J＝σE+Je
Figure BDA0003535379630000102
Qe＝J·E
j is the current density of the high temperature superconducting wire segment;
Jethe ratio of the current of the high-temperature super-lead wire section to the lead wire section;
e is the electric field density of the high-temperature super-guide line section;
v is the potential of the high temperature superconductive wire section;
sigma is the conductivity of the high-temperature super-guide line section material;
Qejoule heating loss for high temperature over-leader segments;
s36, determining the length-diameter ratio of the high-temperature superconducting section according to the simulation structure by adopting a simulation means and taking the minimum heat leakage of the current lead as an objective function based on the coupling model of the thermal field and the electric field of the high-temperature superconducting section, so as to optimize the length-diameter ratios of the Dewar high-voltage lead, the Dewar low-voltage lead and the high-temperature superconducting lead.
In this embodiment, the method further includes an assembly design method of the high-voltage lead segment, and the method includes the following steps:
s41, adopting a G10 thread design for the glass fiber reinforced plastic plug, screwing the glass fiber reinforced plastic plug and a Dewar high-voltage lead wire, and injecting low-temperature glue;
s42, sleeving an epoxy sleeve with the thickness of 6mm outside the Dewar high-voltage lead as the Dewar high-voltage lead sleeve for insulation protection;
s43, sleeving a first Dewar made of AiSi304 stainless steel materials outside the epoxy sleeve to serve as a Dewar lead connecting pipe, and nesting and fixing to reduce heat leakage;
s44, the first vacuum-pumping component consists of a KF25 vacuum nozzle seat and a vacuum nozzle cap made of stainless steel 304 and a DN12 vacuum plug made of S30408, the interior of the high-voltage lead segment is ensured to be in a vacuum state, and the first vacuum-pumping component is fixed on the Dewar high-voltage lead connecting pipe;
s45, fixing the Dewar high-pressure lead connecting pipe by a Dewar high-pressure lead flange designed by AiSi304 material, and simultaneously adopting a sealing ring and glue to perform better sealing and connection.
In this embodiment, the method further includes an assembly design method of the low-voltage lead segment, and the specific steps are as follows:
s51, the Dewar low-voltage lead is made of copper materials and is in a thread shape, and one end of the Dewar low-voltage lead is in a flat shape so as to be fixedly connected with the high-temperature superconducting lead section;
s52, sleeving an epoxy sleeve with the thickness of 1-2 mm outside the Dewar low-voltage lead for insulation protection;
s53, sleeving a lead Dewar on the outer part of the epoxy sleeve, fixing one side close to the high-temperature super-lead segment by using a Dewar low-voltage lead pipe plug, and fixing and insulating the Dewar low-voltage lead by using a glass fiber reinforced plastic inner and outer threaded connector at the outlet end of the other side;
s54, nesting a lead Dewar and a Dewar low-voltage lead connecting pipe, wherein the Dewar low-voltage lead connecting pipe is respectively composed of an inner Dewar low-voltage lead pipe made of 316 stainless steel materials of AiSi type and an outer Dewar low-voltage lead pipe made of AiSi304 materials; because of different materials, the material is assembled in a nested manner;
s55, the glass fiber reinforced plastic internal and external threaded joints and the low-voltage lead inner tube are fixedly connected through a Dewar low-voltage lead flange made of AiSi 304; wherein, the Dewar low-pressure lead flange is a thread flange;
s56, connecting the Dewar low-voltage lead screw joint to the Dewar low-voltage lead outer tube;
the S57, the second vacuumizing assembly and the third vacuumizing assembly are composed of a KF25 vacuumizing nozzle seat and a vacuum nozzle cap made of stainless steel 304 and a DN12 vacuumizing plug made of S30408 material so as to ensure that the interior of the Dewar low-voltage lead and the inner and outer tubes of the Dewar low-voltage lead are in a vacuum state, and the second vacuumizing assembly and the third vacuumizing assembly are respectively welded on the inner tube of the Dewar low-voltage lead and the outer tube of the Dewar low-voltage lead.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the technical scope of the present invention.

Claims (8)

1. A horizontal type Dewar high-temperature superconducting current lead structure is used for a coaxial horizontal transformer and is characterized in that the horizontal type Dewar high-temperature superconducting current lead structure comprises:
a dewar end cap mounted on the transformer;
the Dewar end cover is provided with a high-voltage lead section and a low-voltage lead section;
the first end of the high-voltage lead section is connected with the transformer through a first high-voltage lead and a first low-voltage lead, the second end of the high-voltage lead section is connected with a first high-temperature super-lead section, and the first high-temperature super-lead section is placed in liquid nitrogen of a liquid nitrogen cooler;
the first end of the low-voltage lead section is connected with the transformer through a second high-low voltage lead, the second end of the low-voltage lead section is connected with a second high-temperature super-lead section, and the second high-temperature super-lead section is placed in liquid nitrogen of a liquid nitrogen cooler.
2. The horizontal type dewar high temperature superconducting current lead structure according to claim 1, wherein the high voltage lead section comprises a dewar high voltage lead, a dewar high voltage lead bushing and a dewar lead adapter, the dewar lead adapter is sleeved outside the dewar high voltage lead bushing, wherein a first end of the dewar lead adapter is fixedly connected with a non-end part of the dewar high voltage lead bushing in a sealing manner, and a second end of the dewar lead adapter extends to the outside of the first end of the dewar high voltage lead bushing; a glass fiber reinforced plastic plug is arranged at the second end of the Dewar type lead connecting pipe, and a sealing joint is arranged at the second end of the Dewar type high-voltage lead bushing, so that a first closed space is formed in the Dewar type lead connecting pipe and the Dewar type high-voltage lead bushing; the Dewar high-voltage lead is positioned in the Dewar high-voltage lead sleeve, and two ends of the Dewar high-voltage lead respectively extend to the outer sides of the glass fiber reinforced plastic plug and the sealing joint to form two connecting ends; a first vacuumizing assembly is arranged on the outer side of the Dewar lead connecting pipe and communicated with the first closed space; dewar high pressure lead flange is equipped with to Dewar lead pipe outside cover, Dewar high pressure lead flange be used for with Dewar end cover fixed connection.
3. The horizontal type dewar high-temperature superconducting current lead structure according to claim 1, wherein the low-voltage lead section comprises a dewar low-voltage lead, a dewar low-voltage lead sleeve, a dewar low-voltage lead inner tube and a dewar low-voltage lead outer tube, wherein the dewar low-voltage lead inner tube is sleeved outside the dewar low-voltage lead sleeve, two ends of the dewar low-voltage lead inner tube and the dewar low-voltage lead sleeve are respectively provided with a dewar low-voltage lead flange and a dewar low-voltage lead plug, a second closed space is formed among the dewar low-voltage lead flange, the dewar low-voltage lead plug, the dewar low-voltage lead inner tube and the dewar low-voltage lead sleeve, a second vacuumizing assembly is arranged outside the dewar low-voltage lead inner tube, and the second vacuumizing assembly is communicated with the second closed space; the outer Dewar low-voltage lead pipe is sleeved outside the inner Dewar low-voltage lead pipe; two ends of the outer Dewar low-voltage lead pipe are fixedly connected with the inner Dewar low-voltage lead pipe through a single-sided flange of the Dewar low-voltage lead pipe, and a third closed space is formed; a third vacuumizing assembly is arranged on the outer side of the outer tube of the Dewar low-voltage lead and is communicated with the third closed space; the second closed space and the third closed space are independently arranged; the Dewar low-voltage lead is positioned in the Dewar low-voltage lead sleeve, and two ends of the Dewar low-voltage lead respectively extend to the outer sides of a Dewar low-voltage lead flange and a Dewar low-voltage lead pipe plug to form two connecting ends; the outer side of the outer pipe of the Dewar low-voltage lead is provided with a low-voltage lead screw joint, and the low-voltage lead screw joint is used for being fixedly connected with the Dewar end cover.
4. The design method of the horizontal type Dewar high temperature superconducting current lead structure according to any of claims 1 to 3, characterized by comprising the steps of:
s10, determining the lengths of the Dewar high-voltage lead and the Dewar low-voltage lead;
s20, measuring the outer diameters of the Dewar high-voltage lead and the Dewar low-voltage lead, and determining the inner diameters of the Dewar high-voltage lead and the Dewar low-voltage lead according to the known rated current; meanwhile, the radiuses and the lengths of the Dewar high-voltage lead and the Dewar low-voltage lead are optimized to obtain the optimal length-diameter ratio so as to realize the minimum heat leakage.
5. The design method of the horizontal type dewar high temperature superconducting current lead structure according to claim 4, wherein the specific steps of optimizing the radius and length of the dewar high voltage lead and the dewar low voltage lead in step S20 to obtain the optimal length-diameter ratio are as follows:
s21, according to the requirements of conductivity and heat conductivity, copper is used as a unitary current lead to reduce the Joule heat caused by the heat transfer current, and a Dewar type sleeve is used for cooling to achieve the purpose of reducing heat leakage;
s22, because the length is far larger than the radius of the cross section of the Dewar type heat collector, and meanwhile, if no temperature difference exists on the cross section, the radius is adopted as an invariant, and the lengths of the Dewar type high-voltage lead and the Dewar type low-voltage lead are changed to analyze heat leakage; theoretical analysis was performed by the following formula:
Figure FDA0003535379620000021
Figure FDA0003535379620000031
where ρ and κ are the thermal conductivity and resistivity of the copper lead, respectively;
is derived from
Figure FDA0003535379620000032
The length-to-section ratio at this time is known from the minimum heat leakage
Figure FDA0003535379620000033
When T isj＝77K ThWhen the temperature is 300K, the length-cut ratio with the minimum heat leakage is obtained;
in the formula, QgenJoule's heat, Q conduction heat, (Q)2)minFor minimum heat conduction, L is the length of the lead, A is the cross-sectional area of the lead, ThIs the temperature at the upper end of the lead, TjIs the cold end temperature;
wherein the current density is usually 5-6A/mm2(ii) a And the Dewar high-voltage lead and the Dewar low-voltage lead are designed into a thread type according to the heat conduction principle in the rib wall.
6. The design method of the horizontal type Dewar high-temperature superconducting current lead structure according to claim 5, characterized by further comprising the steps of designing the high-temperature superconducting lead, which comprises the following specific steps:
s31, determining a high-temperature superconducting material of the high-temperature superconducting wire section, wherein the high-temperature superconducting material selects a YBCO superconducting tape;
s32, spreading a superconducting tape outside the metal rod, and fixing the high-temperature superconducting current lead section by using a clamping device to prevent shrinkage in the cooling process;
s33, arranging two ends of the high-temperature super-lead wire segment into a flat shape, and performing insulation protection on the outer side of the high-temperature super-lead wire segment by using an epoxy insulation cylinder;
s34, the thermal field model of the high-temperature super-guide line section satisfies the following relational expression:
Figure FDA0003535379620000034
wherein rho is the density of the high-temperature super-guide line section material;
cp is the constant pressure heat capacity of the high-temperature superconductive wire section material;
mu is the flow speed of the fluid outside the high-temperature superconducting lead section;
q is the heat flux of the high temperature superconductive wire section;
k is the thermal conductivity of the high-temperature superconductive wire section material;
Figure FDA0003535379620000041
is a gradient operator;
t is the temperature of the high-temperature superconductive wire section;
qe is the joule heating loss of the current lead;
s35, the electric field model of the high-temperature super-guide line section satisfies the following relational expression:
J＝σE+Je
Figure FDA0003535379620000042
Qe＝J·E
j is the current density of the high temperature superconducting wire segment;
Jethe ratio of the current of the high-temperature super-lead wire section to the lead wire section;
e is the electric field density of the high-temperature super-guide line section;
v is the potential of the high temperature superconductive wire section;
sigma is the conductivity of the high-temperature super-guide line section material;
Qejoule heating loss for high temperature over-leader segments;
s36, based on the coupling model of the thermal field and the electric field of the high-temperature superconducting wire segment, determining the length-diameter ratio of the high-temperature superconducting segment according to the simulation structure by adopting a simulation means and taking the minimum heat leakage of the current lead as an objective function, so as to optimize the length-diameter ratios of the Dewar high-voltage lead, the Dewar low-voltage lead and the high-temperature superconducting lead.
7. The design method of the horizontal type Dewar high-temperature superconducting current lead structure according to claim 6, characterized by further comprising an assembly design method of a high-voltage lead section, and the specific steps are as follows:
s41, adopting a G10 thread design for the glass fiber reinforced plastic plug, screwing the glass fiber reinforced plastic plug with a Dewar high-voltage lead wire, and injecting low-temperature glue;
s42, sleeving an epoxy sleeve with the thickness of 6mm outside the Dewar high-voltage lead as the Dewar high-voltage lead sleeve for insulation protection;
s43, sleeving a first line Dewar made of AiSi304 stainless steel material outside the epoxy sleeve to serve as a Dewar lead connecting pipe, and nesting and fixing to reduce heat leakage;
s44, the first vacuum-pumping component consists of a KF25 vacuum nozzle seat and a vacuum nozzle cap made of stainless steel 304 and a DN12 vacuum plug made of S30408, the interior of the high-voltage lead segment is ensured to be in a vacuum state, and the first vacuum-pumping component is fixed on the Dewar high-voltage lead connecting pipe;
s45, fixing the Dewar high-pressure lead connecting pipe by a Dewar high-pressure lead flange designed by AiSi304 material, and simultaneously adopting a sealing ring and glue to perform better sealing and connection.
8. The design method of the horizontal type Dewar high-temperature superconducting current lead structure according to claim 7, characterized by further comprising an assembly design method of a low-voltage lead section, and the specific steps are as follows:
s51, the Dewar low-voltage lead is made of a copper material and is in a threaded shape, and one end of the Dewar low-voltage lead is in a flat shape so as to be fixedly connected with the high-temperature superconducting lead section;
s52, sleeving an epoxy sleeve with the thickness of 1-2 mm outside the Dewar low-voltage lead for insulation protection;
s53, sleeving a lead Dewar on the outer part of the epoxy sleeve, fixing one side close to the high-temperature super-lead segment by using a Dewar low-voltage lead pipe plug, and fixing and insulating the Dewar low-voltage lead by using a glass fiber reinforced plastic inner and outer threaded connector at the outlet end of the other side;
s54, nesting a lead Dewar and a Dewar low-voltage lead connecting pipe, wherein the Dewar low-voltage lead connecting pipe is respectively composed of an inner Dewar low-voltage lead pipe made of 316 stainless steel materials of AiSi type and an outer Dewar low-voltage lead pipe made of AiSi304 materials; because of different materials, the material is assembled in a nested manner;
s55, the glass fiber reinforced plastic internal and external screwed joints and the low-voltage lead inner tube are connected and fixed through a Dewar low-voltage lead flange made of AiSi 304; wherein, the Dewar low-voltage lead flange is a thread flange;
s56, connecting the Dewar low-voltage lead screw joint to the Dewar low-voltage lead outer tube;
the S57, the second vacuumizing assembly and the third vacuumizing assembly are composed of a KF25 vacuumizing nozzle seat and a vacuum nozzle cap made of stainless steel 304 and a DN12 vacuumizing plug made of S30408 material so as to ensure that the interior of the Dewar low-voltage lead and the inner and outer tubes of the Dewar low-voltage lead are in a vacuum state, and the second vacuumizing assembly and the third vacuumizing assembly are respectively welded on the inner tube of the Dewar low-voltage lead and the outer tube of the Dewar low-voltage lead.
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