JPH02299108A - Superconducting cable - Google Patents

Abstract

PURPOSE:To make the outer diameter of a cable thin and reduce the pressure loss by using a superconductor for cable cores, and arranging uncorrugated metal pipes forming coolant passages in a heat insulating conduit. CONSTITUTION:A protective metal pipe 4 is arranged around a metal 1 forming a coolant passage 2 via a heat insulator layer 3, and an anticorrosive layer 5 on the outermost layer to obtain the pipe 1 forming the passage 2 of a heat insulating conduit 6. Cylindrical superconductors 10 are provided around metal pipes 8 forming coolant passages 9 in cores, electric insulating layers 11 are provided around these conductors 10, and the desired number of superconducting cable cores 7 provided with shielding superconductors 12 are arranged around the layers 11. The desired number of uncorrugated metal pipes 14 forming coolant passages 13 are arranged in the pipe 1 forming the passage 2 of the conduit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a superconducting cable with a small outer diameter (and low pressure loss).

(Prior Art) Superconducting cables have been around for a long time, and their structure is as shown in FIG. A desired number of superconducting cable cores 7 are disposed within the metal pipe 1 of the heat insulating conduit 6, in which a corrosion-resistant material layer 5 is provided on the outermost layer.

This superconducting cable core 7 is provided with a tubular superconducting four conductor 10 on the outer periphery of a metal tube 8 forming a core coolant flow path 9, and an electrical insulating layer 11 is provided on the outer periphery of the superconducting conductor 10. A shielding superconducting conductor 12 is provided around the outer periphery of the insulating layer 11.

The energizing superconducting conductor 10 and the shielding superconducting conductor 12 are as follows:
For example, bismuth, strontium, calcium, fIA
It is composed of a composite tape in which an oxide superconductor such as an oxide of yttrium, barium, or copper is bonded to a stabilizing layer made of, for example, copper or aluminum.

By the way, in the conventional superconducting cable, in order to maintain both the current-carrying superconducting conductor IO and the shielding superconducting conductor 12 (hereinafter simply referred to as superconducting conductors) in a temperature range where the required superconducting current can be passed, the conductors are It is necessary to remove the heat generated from the heat insulator and the insulator, and the heat that enters the heat insulating pipe line 6 from the outside. For this reason, in the conventional superconducting cable, liquid nitrogen is flowed as a coolant into the coolant flow path 2 in the heat insulating pipe line 6 and the core coolant flow path 9 in the cable core.

The liquid nitrogen flowing through these coolant channels 2.9 is impregnated into the Mi conductive cable core 7 so as to also serve as electrical insulation.

Furthermore, the liquid nitrogen flowed into the two coolant channels 2 and 9 must be strong enough to completely remove the total amount of heat mentioned above, and must have enough pressure to exhibit sufficient electrical insulation properties. Incidentally, if the flow rate of liquid nitrogen is insufficient, the temperature of the superconducting cable core 7 will rise too much, breaking the superconducting state and making power transmission impossible. Furthermore, if the pressure is insufficient, bubbles will be generated in the liquid nitrogen, reducing the electrical insulation properties and causing dielectric breakdown of the cable.

In addition, liquid nitrogen flowing in the coolant channel 2.9 experiences a pressure loss, which increases in proportion to the flow rate and inversely as the fifth power of the diameter of the uncorrugated channel tube. do. This pressure loss also increases when the metal pipe 1 constituting the heat insulating pipe 6 and the protective metal pipe 4 are corrugated in order to bend the heat insulating pipe, as the resistance to the flowing liquid nitrogen increases. Become. If this pressure loss becomes large, there is a risk that the cable will suffer dielectric breakdown due to insufficient pressure, or the liquid nitrogen will no longer flow throughout the cooling section and the cable will not be sufficiently cooled. For this reason - the permissible pressure loss in the cooling section must be below a certain maximum permissible value.

For this purpose, it is necessary to ensure that the cross-sectional area of the liquid nitrogen flow path is larger than a certain area.

Also, even if the pressure + i loss does not exceed the maximum allowable value, the greater the pressure loss, the greater the electrical
Since mechanical loads are applied, it is necessary to increase the strength of the design, and stability and reliability during cable operation are also impaired.

(Problems to be Solved by the Invention) However, in order to reduce pressure loss and improve reliability, the cross-sectional area of the liquid nitrogen flow path is increased (this increases the outermost diameter of the cable).

For example, transmission voltage 66kv, transmission capacity 100100O,
Critical current density of superconducting layer lX10'A/cm", outer diameter 4
40mm thick with 3 built-in 0mm cable cores
In the case of a conventional superconducting cable having a conduit with a heat insulation layer of

However, in this cable, when liquid nitrogen is circulated back and forth in one cooling section length of 2.5 km, the pressure loss becomes about 10 atm, so even if the pressure is maintained at 15 atm at the point where the cable enters from the liquid nitrogen cooler, the cable At the exit, the pressure drops to about 5 atmospheres.

For this reason, the pressure necessary to prevent partial discharge from occurring in the electrical insulating layer 11 is extremely low, and the stability and reliability of operation are extremely low.

Incidentally, the pressure loss that occurs here does not occur in the core coolant flow path 9 inside the superconducting cable core 7, but rather in the coolant flow path 2 of the adiabatic pipe line 6, and the main The reason for this is that the shape of the coolant flow path 2 in the heat insulating pipe 6 is not circular and is also thinner than the coolant flow path 9 in the core, so the flow of the coolant is easily disturbed and frictional resistance increases. By doing.

Therefore, in the conventional superconducting cable mentioned above.

In order to prevent the pressure from dropping to around 5 atm, the outer diameter of the cable should be made larger than 170 mm to reduce pressure loss, or the inlet pressure should be increased to 20 atm and the cable outlet pressure should be around IO atm. It will be necessary to increase the design strength and chiller output. However, increasing the outer diameter of the cable increases manufacturing, transportation, and installation costs.

Increasing the design strength of the cable and the cooler output will result in higher costs, which in any case will result in higher costs.

As described above, conventional superconducting cables have problems such as increased pressure loss and increased cable outer diameter, which impairs reliability and economic efficiency.

(Object of the Invention) The superconducting cable of the present invention was developed to solve the above-mentioned problems, and its purpose is to provide a superconducting cable with a small outer diameter and low pressure loss. .

(Means for Solving the Problems) In the superconducting cable of the present invention, as shown in FIG. A metal pipe 8 forming the coolant flow path 9 in the core is provided in the metal pipe l forming the coolant flow path 2 of the heat insulating pipe line 6 which is provided with a corrosion-resistant material layer 5 on the outermost layer. A superconducting cable core 7 in which a tubular current-carrying superconducting conductor 10 is provided on the outer periphery of the superconducting cable core 7, an electrical insulating layer 11 is provided on the outer periphery of the superconducting conductor 10, and a shielding superconducting conductor 12 is provided on the outer periphery of the insulating layer 11. In a superconducting cable in which a desired number of wafers are arranged, an uncorrugated metal tube 14 that is not corrugated and that forms a coolant flow path 13 is placed inside the metal tube l that forms the coolant flow path 2 of the adiabatic pipe line 6. It is characterized in that a desired number of pieces are arranged.

The corrugated metal tube 14 forming the coolant flow path 13 in the present invention is made of a metal with high thermal conductivity, such as copper, so that the coolant flowing inside the tube can efficiently take in heat from the outside. It is being

When using the superconducting cable of the present invention, all or almost all of the coolant that was flowing into the metal pipe l forming the coolant flow path 2 in the heat-insulating pipe line 6 of the conventional superconducting cable is removed. It is preferable to flow the electrically insulating liquid nitrogen for impregnating the superconducting cable core 7 into the non-corrugated metal pipe 14 disposed in the heat-insulating conduit 6 of the superconducting cable of the present invention. It is used separately from the liquid nitrogen for heat removal flowing into the metal tube 14. In this way, unlike liquid nitrogen for heat removal, liquid nitrogen for electrical insulation does not need to be circulated within the cooling section, so there is no pressure loss, and the pressure remains constant throughout the section, making it even more reliable. High electrical insulation can be achieved.

In order to reduce the outer diameter and pressure loss of the superconducting cable of the present invention, the ratio RJ of the inner diameter of the insulated pipe line 6 and the outer diameter of the superconducting cable core 7 should be 2.1≦RJ≦2.5. It is desirable to do so.

(Function) The superconducting cable of the present invention has an uncorrugated metal pipe 14 that is not corrugated and forms a coolant flow path 13 in the metal pipe 1 of the heat insulating conduit 6, so that it is different from the conventional superconducting cable. By flowing all or almost all of the coolant that was flowing through the heat insulated pipe line 6 through the cable into the corrugated metal pipe 14 that forms the coolant flow path 13, the metal constituting the heat insulated pipe line 6 is removed. The pressure losses occurring in the tubes 1 and in the coolant channels 13 are significantly reduced.

(Example) Hereinafter, the superconducting cable of the present invention will be explained in detail with reference to Examples.

The power transmission standard of the superconducting cable of the present invention shown in Fig. 1 is 6.
The pressure loss P was determined under the conditions of 6 kv, 100,100 O, and a cable outer diameter of 170 mm. Pressure loss P is determined as follows.

P=R-M2 ・L/D' ・ ・ ・ ・ (
1) It's f-day.

R: flow resistance, M: coolant material 1 flow I, L: cooling section length.

D. Coolant channel diameter (or coolant channel equivalent diameter).

The coolant mass flow rate M is determined by the following equation.

M=W-L/(C・T)...(2)(Danshi.

Wltj? 'Amount of heat to be removed, C0 coolant heat capacity, T: Coolant temperature rise.

The amount of heat W to be removed consists of AC loss in the conductor, dielectric loss in the electrical insulator, and heat penetration.

In the above equations (1) and (2), L = 2.5 km.

C = 2035 J/kg-, T = 15, and considering that W is mainly conductor AC loss, which is inversely proportional to the critical current density of the superconducting conductor, this current density is set to 1x.
10'A/cm''.

In this embodiment, 95% of the coolant flowing in the metal tube 1 forming the coolant flow path 2 constituting the heat-insulated conduit of a conventional superconducting cable is transferred to an uncorrugated metal tube that is not corrugated. 14, and the remaining 5% is poured into the metal pipe l that constitutes the insulated pipe line.
It was decided that it would be flushed to

In addition, regarding the ultra':M conductive cable of the present invention, the pressure loss can be measured both when the metal tube 1 constituting the insulated conduit 6 and the protective metal tube 4 are corrugated and when they are not corrugated. Calculated. We also have the same standard as that for comparison,
Similar calculations were performed for a conventional superconducting cable of the same size. The results are listed in Table 1 with the design values for both.

Table 1: Corrugated type: Metal pipe constituting an insulated pipe line 1. When the protective metal tube 4 is corrugated: Non-liquid type: When the metal tube l constituting the heat-insulating pipe line and the protective metal tube 4 are not corrugated.

As is clear from Table 1, the superconducting cable of the present invention enables large-capacity power transmission with a rated capacity of N10N10O0 using a thin cable with an outer diameter of 170 mm.

Furthermore, in the case of superconducting cables, the pressure loss is 3, 6, and 35 atmospheres, which are far below the maximum allowable amount of 10 atmospheres, both in the case of the corrugated type and in the case of the non-corrugated type. It can be seen from this that it has excellent economic efficiency, stability during operation, and reliability.

On the other hand, in the case of conventional superconducting cables having the same capacity and size as the superconducting cable of the present invention, the pressure loss was 1019 atm for the corrugated type and 8.7 atm for the non-corrugated type.

Therefore, in the comparative example, the operating conditions and design conditions are stricter than in the superconducting cable of the present invention, and the cost of the cable body, cooling device, etc. is high.

Furthermore, in order to achieve the same level of pressure loss as the cable of the present invention in the comparative example, it is necessary to increase the outer diameter of the cable, which also increases the cost.

(Effects of the Invention) In the superconducting cable of the present invention, a superconductor is used for the cable core 7, and a corrugated metal pipe 14 forming a coolant flow path 2 is disposed within the heat insulating pipe line 6, so that the following can be achieved. There is a similar effect.

■The superconducting cable has a thin outer diameter and low pressure loss, making it possible to transmit large amounts of power at low cost and with high reliability.

99 In the superconducting cable of the present invention, all of the coolant that was flowing into the heat insulating pipe line 6 of the conventional superconducting cable is flowed into the waveless metal pipe 14 separately arranged inside the heat insulating pipe line 6, and the superconducting cable core 7 Since liquid nitrogen for electric insulation is used separately from liquid nitrogen for heat removal flowing through the corrugated metal pipe 14, no pressure loss occurs, and sufficient pressure is maintained constant over the entire length of the cooling section. Since it is possible to carry out one type of electrical insulation, even more reliable electrical insulation can be achieved.

■Since liquid nitrogen for electrical insulation is not flowed into the metal pipe l of the heat insulating pipe line 6, impurities such as water may get mixed into the liquid nitrogen, which may damage the cable core and the heat insulating pipe line during the flow. Almost eliminates the risk.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of an oxide superconducting cable according to the present invention, and FIG. 2 is an explanatory diagram of a conventional oxide superconducting cable. 1 is a metal tube 2 is a coolant flow path 3 is a thermal insulator layer 4 is a protective metal tube 5 is a corrosion-resistant material layer 6 is a heat insulating conduit 7 is a superconducting cable core 8 is a metal tube 9 is a coolant flow path 10 is energized The electrical insulating layer 12 of the superconducting conductor 11 is Jl! In the superconducting conductor used for shielding, the coolant flow path 14 is a corrugated metal tube.

Claims (1)

[Claims] A thermal insulator layer 3 is provided on the outer periphery of the metal tube 1 forming the coolant flow path 2.
A metal tube 8 forming a core coolant flow path 9 in the metal tube 1 of the heat insulating conduit 6 having a protective metal tube 4 disposed therethrough and a corrosion-resistant material layer 5 provided on the outermost layer. A superconducting cable core 7 in which a tubular current-carrying superconducting conductor 10 is provided on the outer periphery of the superconducting cable core 7, an electrical insulating layer 11 is provided on the outer periphery of the superconducting conductor 10, and a shielding superconducting conductor 12 is provided on the outer periphery of the insulating layer 11. In a superconducting cable with a desired number of
A superconducting cable characterized in that a desired number of uncorrugated metal pipes 14 that are not corrugated and form a coolant flow path 13 are arranged in the metal pipe 1 of the heat insulating conduit 6.