JPH02296309A - Superconductive transformer - Google Patents

Abstract

PURPOSE:To obtain a superconductive transformer which is high in reliability from the viewpoint of accident prevention, light, and also excellent in insulating capacity by filling refrigerant such as liquid nitrogen, etc., in a heat insulating vessel so as to cool winding, and filling gas at normal temperature such as nitrogen gas, etc., in a tank outside the heat insulating vessel, and for cooling of an iron core, performing it with a cooling system in other line such as a cooling panel inserted in the iron core. CONSTITUTION:The wall face of a heat insulating vessel 4 is constituted of double vessels 41 and 42 of FRP, and a conductive layer 44 made by metallic deposition, etc., is provided at the face on the side of a vacuum layer, and this conductive layer 44 is connected to grounding potential. And high and low voltage windings 2 and 3 constituted of oxide superconductors are stored in the heat insulating vessel 4, and a pressure release valve 12, which operates at internal pressure rise in an accident, is attached to the top of the heat insulating vessel 4. Furthermore, gas 8 such as nitrogen gas, etc., is charged in the air outside the heat insulating vessel 4 and inside a transformer tank 7, and a cooling panel 9 is interposed between iron core pulling-out plate layers inside the iron core 1. Hereby, enlargement of an accident inside the winding can be suppressed to the minimum, and reliability can be elevated.

Description

[Detailed description of the invention] [Purpose of the invention] (Field of industrial use) The present invention relates to a superconducting transformer using a superconducting conductor.

(Conventional technology) The application of superconductors to power equipment has been studied for a relatively long time, and recently, along with the development of AC superconducting wires, research into the application of superconductors to AC electrical equipment such as transformers has also begun. It's progressing. However, there are various technical problems in putting it into practical use.

This requires equipment using conventional superconducting materials such as NbTi, N, and b3Sn, which are premised on cooling with liquid helium, or the extreme technology of freezing at extremely low temperatures. One of the major factors was that reliability was an obstacle to practical application. However, recently, the development of oxide-based high-temperature superconductors has progressed rapidly, and YBa2Cu
The discovery of materials such as 307-x that exhibit the characteristics of superconductors, such as zero electrical resistance and complete diamagnetic properties above liquid nitrogen temperature, has been reported in various places. When such high-temperature superconducting materials are used, liquid nitrogen can be used as a refrigerant, so
Not only will the cost of the refrigerant itself be reduced, but refrigeration technology will become much easier, making it possible to obtain equipment that is not only economical but also highly reliable, and it is expected that its application to power equipment will rapidly advance.

When superconducting conductors are applied to transformers, very efficient transformers can be obtained, especially since winding losses are eliminated.

FIG. 3 shows a schematic diagram of a conventional superconducting transformer.

In FIG. 3, reference numeral 1 denotes an iron core, and a high voltage winding 2 and a low voltage winding 3 concentrically wound around the iron core 1 are housed in a heat insulating container 4. A refrigerant 5 such as liquid nitrogen or liquid helium is sealed in the heat insulating container 4, and a device body consisting of the iron core 1 and the windings 2 and 3 is housed in a tank 7 outside the heat insulating container 4, as well as insulating oil 6. Or fulfilled. and,
The winding conductor is maintained in a superconducting state by the coolant 5 in the heat insulating container 4. The insulating oil 6 outside the heat insulating container 4 is in a room temperature space and plays the role of extracting the heat generated from the iron core 1 to the outside and also the role of insulating between the windings 2.3 and grounded objects such as the iron core 1 and the tank 7. There is.

Storing only the windings 2 and 3 in a heat insulating container 4 and placing the iron core 1 in a room temperature space is possible by immersing the iron core 1 and the like in a refrigerant 5 such as liquid nitrogen or liquid helium and cooling the iron core 1 with the refrigerant 5. This is because a large amount of electric power is required to power the refrigerator, and the advantage of low loss of the superconducting transformer is lost. This is because the refrigerator requires about 10 times more power at liquid nitrogen temperature and about 500 times more power at liquid helium temperature in terms of temperature in order to cool down the heat generated in a low-temperature space. Furthermore, by filling the outside of the insulation container 4 with insulating oil 6, the insulation between the windings 2 and 3 and grounded objects such as the iron core 1 and the tank 7 is maintained in a good condition, and the insulation container 4 is not an insulator. I don't mind.

(Problems to be Solved by the Invention) However, such conventional superconducting transformers have the following problems. In other words, if the superconducting conductor quenches for some reason or a dielectric breakdown accident occurs inside the winding, a large amount of energy is consumed in the heat insulating container 4 due to the arc generated by heat generation and dielectric breakdown of the conductor, and the refrigerant 5
The instantaneous evaporation of the oil increases the pressure inside the insulating container 4, and in the worst case, serious disasters such as damage to the insulating container 4 and even a fire in the transformer due to ignition of the insulating oil 6 are expected. It was necessary to take all possible precautions against accidents.

The present invention was made to solve these problems, and aims to minimize the spread of accidents inside the windings, improve reliability, and obtain a superconducting transformer with high cooling efficiency. shall be.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, in the present invention, a conductive layer is provided inside the wall surface of the heat insulating container for storing the winding, this conductive layer is connected to ground potential, and the heat insulating container is A refrigerant such as liquid nitrogen is sealed inside, and the insulated container is equipped with a pressure relief valve. Then, the transformer tank outside the insulation container is filled with nitrogen gas.
The core is cooled by a cooling panel inserted into the core.

(Function) In a superconducting transformer with such a configuration, even if liquid nitrogen rapidly evaporates due to an accident inside the windings and the pressure inside the insulated container increases, liquid nitrogen will not be released from the pressure relief valve into the tank. Since the tank is filled with gas, the pressure increase is absorbed by this space and does not cause the tank to explode. Furthermore, since no insulating oil is used, there is no risk of serious disasters such as fire.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the same parts as the conventional one are indicated by the same symbols, and the explanation thereof will be omitted. In FIG. 1, high and low voltage windings 2 and 3 made of oxide superconductors are housed in a heat insulating container 4. The heat generated by AC loss in the winding conductor is taken away by the latent heat of vaporization of the refrigerant of liquid nitrogen 5, and the vaporized nitrogen is led from the insulated container 4 to the outside of the tank 7, which is made up of a nitrogen liquefier, etc. It is converted into lfk again by the freezing device 11 and fed into the winding from the lower part of the heat insulating container 4. In addition,
A pressure relief valve 12 is attached to the top of the heat insulating container 4, which operates when the internal pressure increases in the event of an accident. Furthermore, a heat insulating container 4
The air inside the outer transformer tank 7 is filled with a gas 8 such as nitrogen gas. A cooling panel 9 is sandwiched between core punched layers within the core 1, and a refrigerant such as Fluorinert cooled by a cooler 10 is fed into the cooling panel 9.

The wall surface of the heat insulating container 4 is FR
P double container 41. , 42, a vacuum is maintained between the double walls, and a heat insulating material 43 formed by stacking aluminum-deposited plastic films called super insulation is inserted, and the inside of the heat insulating container is A conductive layer 44 formed by metal vapor deposition or the like is provided on the surface of the FRP wall constituting the wall on the vacuum layer side, and this conductive layer 44 is connected to a ground potential.

In this embodiment configured in this way, the following effects occur.

(1) The high voltage parts such as the windings 2 and 3 are surrounded by the conductive layer 44 of the heat insulating container 4 connected to ground potential, and the insulation between them is maintained by liquid nitrogen 5, so the high voltage parts such as the windings 2 and 3 are surrounded by the conductive layer 44 of the heat insulating container 4, which is connected to the ground potential. 7, no electric field is applied to the space, and even if the space is filled with nitrogen gas 8 at atmospheric pressure, there is no problem with insulation, and there is no need to use insulating oil. Note that since the dielectric strength of liquid nitrogen 5 is about 14 times that of insulating oil, the insulation within the winding can be maintained well.

(2) Since the core 1 is cooled by the cooling panel 9, no insulating oil is required to cool the core 1.

(3) There is rapid evaporation of liquid nitrogen 5 in the heat insulating container 4,
When the pressure inside the container rises by 1, the pressure relief valve 12 attached to the insulated container 4 operates, and liquid nitrogen or nitrogen gas is released into the tank 7, causing the nitrogen gas in the tank 7 to evaporate due to the increased air pressure. Since the nitrogen gas is absorbed, the pressure increase in the tank 7 becomes gradual, and if the tank 7 is equipped with a pressure relief device, the pressure can be relieved before the interior of the tank 7 explodes. At this time, the nitrogen gas released into the tank 7 can be regenerated as liquid nitrogen without being consumed if it is guided to the liquefier of the cooling device 11 through another piping system.

(4) Since gas is used outside the heat insulating container 4, the transformer is lighter than when insulating oil is used.

(5) Since there is no need to use insulating oil, even in the unlikely event of an accident, it will not lead to a serious disaster such as a fire.

Another method for cooling the iron core is to insert a heat pipe inside the iron core.

〔Effect of the invention〕

As explained above, according to the present invention, by using a gas such as nitrogen gas outside the insulating container and using a separate cooling system for the core, it is possible to achieve high reliability, light weight, and excellent insulation performance for disaster prevention. A superconducting transformer can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a superconducting transformer showing an embodiment of the present invention, Fig. 2 is an enlarged view of a portion of the wall of an insulating container used in the transformer of Fig. 1, and Fig. 3 is a conventional superconducting transformer. It is a sectional view of a container. 1... Iron core 2... High voltage winding 3... Low voltage winding 4... Heat insulating container 5... Liquid nitrogen
6... Insulating oil 7... Tank 8...
Nitrogen gas 9...Cooling panel 10...Cooler 11
... Refrigerator 12 ... Pressure relief valves 41, 42.
・・FRP container 43・Insulating material 44・・Conductive layer agent Patent attorney Nori Chika Ken Yudo Daiko Maru Ken

Claims (1)

[Claims] In a superconducting transformer in which only the windings wound around the iron core are stored in an insulated container, and the contents consisting of the iron core and the windings are stored in a tank, a conductive layer is provided inside the wall of the insulated container, and this conductive layer is connected to the ground potential. The inside of the insulation container is filled with a refrigerant such as liquid nitrogen to cool the windings, and the tank outside the insulation container is filled with room temperature gas such as nitrogen gas. A superconducting transformer that operates using a separate cooling system such as a panel.