JPS61179512A - Gas-insulated transformer - Google Patents

Abstract

PURPOSE:To enable the circulation of a refrigerant to be reversed for preventing the accumulation of air bubbles, by providing a motor for driving a pump with a changeover switch for changing over the rotating direction of the motor or with a means for reversing the circulating direction of the refrigerant. CONSTITUTION:A motor 20 driving a pump 7 for circulating a refrigerant is provided with a changeover switch 22 for switching the rotating direction of the motor. Constructing a transformer in this manner, the rotating direction of the motor 20 can be reversed by changing over the switch 22 provided on the motor 20 for driving the pump 7, whereby the circulating direction of the refrigerant also can be reversed. Accordingly, even if microbubbles are accumulated in a refrigerant flow path or in a filter as a result of temporary over-load operation of the transformer, these microbubbles can be removed by reversing the circulating direction of the refrigerant. Therefore, the flow of the refrigerant will not be inhibited and the cooling efficiency will not be reduced.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention uses SF6 as an insulating medium, such as a foil-wound transformer.
The present invention relates to a gas insulated transformer that uses an insulating gas such as gas and has a cooling circulation system separated from the insulating gas.

[Technical Background of the Invention] Foil-wound transformers have a good winding space factor and are characterized by being small and lightweight. It has already been put into practical use in relatively low voltage, small capacity transformers such as aKV and several hundred KVA. In recent years, research has been carried out to expand its application to higher voltage and larger capacity transformers, such as 275KV and 300MVA class transformers. Can the winding have it?
It depends on whether it can withstand the radial mechanical force in the event of a short circuit accident. Such high-voltage, large-capacity transformers have not yet been put to practical use, but as shown in Figure 3, a cooling duct is built into the windings, and a refrigerant with insulating properties is fed into the cooling ducts to A heat pipe type foil-wound transformer, which cools the heat generated from line loss by using the latent heat of vaporization of the refrigerant, is promising.

That is, in this foil-wound transformer, a low-voltage winding 4 and a high-voltage winding 5, which are made by overlapping metal sheets 2 and insulating sheets 1-3, are wound around a leg 1 of an iron core, and the inside of these windings is has a built-in hollow cooling duct 6.

In the thin gap in the hollow part of the cooling duct 6, fluorocarbon R11
It is filled with refrigerants such as 3 and Fluorinert FC75.
The refrigerant is circulated by a pump 7, and the heat generated in the windings is removed by the latent heat of vaporization of the refrigerant, and the vapor is cooled and condensed through a cooling water pipe in a condenser 8. A cooling system is constructed in which the liquefied refrigerant is stored in a refrigerant tank 10 and further fed into the windings by a pump 7.

The liquid guide pipe 11 constituting the cold fJI system is made of metal such as stainless steel, and the liquid guide pipe 11 and the cooling duct 6 are connected via an insulating pipe 12 made of Teflon resin or the like. This liquid guide pipe 11 is also connected to the ground potential of the tank 13, etc. On the other hand, since the cooling duct 6 is built into the winding, it is electrically connected to the same potential as the adjacent winding. Further, insulation of each part of the winding is ensured by an insulating gas such as SF6 gas sealed in the tank 13.

[Problems with Background Art] By the way, in the various foil-wound transformers as described above, the low-voltage winding 4 and the high-voltage winding 5 are formed by overlapping and winding the thin metal sheet 2 and the insulating sheet 3. As a result, the winding space factor within the core window increases, but on the other hand, there are the following problems.

That is, in the foil-wound transformer as described above, by circulating the refrigerant in the cooling duct 6 that constitutes the cooling system,
Since the method uses convective heat transfer to cool down the heat generated in the windings, bubbles will not be generated in the cooling duct 6, but there may be temporary overload operation when the transformer 1 is operating. At that time, there was a possibility that microbubbles could be generated.

There is a possibility that the microbubbles may be trapped in the corners of the cooling duct 6, the connection part of the liquid guide pipe 11, etc., and the flow rate of the refrigerant is thereby slowed down, and there is a possibility that the cooling efficiency will be significantly reduced.

In addition, the long 1111 operation of the transformer tends to cause deterioration of the refrigerant material, and it is extremely difficult to remove the resulting products using only a filter or trapper installed in the refrigerant circulation system. Therefore, there was a risk that the particles would be trapped in the corners of the cooling duct 6, the connecting portions of the liquid guide pipes 11, and the like. As a result, the circulation of the refrigerant was significantly hindered, causing a drop in cooling efficiency. Similar problems exist in various gas insulated transformers in which the cooling system is separated.

F Purpose of the Invention The present invention was proposed in order to eliminate the drawbacks of the conventional gas insulated transformer as described above. An object of the present invention is to provide a highly reliable gas insulated transformer that maintains excellent cooling performance even when a gas insulated transformer occurs.

[Summary of the Invention] The gas insulated transformer of the present invention includes a motor for driving a pump that is provided with a changeover switch for switching the direction of rotation of the motor, or a liquid guide that is provided above and below the winding. A means for reversing the circulation direction of the refrigerant is provided, such as by arranging two pipes with switching valves between the pipes, so that the refrigerant can be reversed and the generation of bubbles can be prevented.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be explained in detail based on FIG. Note that the same parts as those of the conventional gas insulated transformer shown in FIG. 3 are designated by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 1, a motor 20 that drives a pump 7 for circulating refrigerant is provided with a changeover switch 22 for switching the rotation direction of the motor.

In the gas insulated transformer of this embodiment configured in this way, by switching the changeover switch 22 disposed on the motor 20 that drives the pump 7, the motor 20
The direction of rotation of the pump 7 can be reversed, thereby also reversing the direction of circulation of the refrigerant by the pump 7. As a result, even if microbubbles accumulate in the refrigerant flow path or filter after a temporary overload operation of the transformer, these microbubbles can be removed by reversing the direction of refrigerant circulation. −
Therefore, the flow of the refrigerant is not obstructed and the cooling efficiency is not reduced. Furthermore, even if the refrigerant deteriorates or decomposes due to long-term operation of the transformer and its products accumulate in the flow path or filter, it can be removed by reversing the direction of refrigerant circulation by similarly switching the changeover switch 22. can.

Note that the present invention is not limited to the above-mentioned embodiment, and as shown in FIG. In providing the main pipes 31 and 32, the flow direction of the refrigerant may be reversed. That is, the switching valves 30a and 30
When listening to b and closing 30C and 30d, the refrigerant sent out from the pump 7 passes through the lower liquid guide pipe 11, flows upward in the cooling duct 6, and further passes through the upper liquid guide @11 to the condenser. Sent to 8. On the contrary, the switching valves 30a and 3
When 0b is closed and 30G and 30d are opened, the refrigerant sent out from the pump 7 passes through the pipe 32 and flows into the upper liquid guide pipe 11.
, and flows downward in the cooling duct 6 to the lower liquid conduit 1.
1 and pipe 3.1 to the condenser. Also in this case, since the flow direction of the refrigerant can be reversed as in the above embodiment, excellent cooling efficiency can be maintained.

Note that the flow direction of the refrigerant may be reversed at regular intervals even after the transformer is overloaded.

[Effects of the Invention] As described above, according to the present invention, by making it possible to reverse the flow direction of the refrigerant, it is possible to prevent the cooling efficiency from decreasing due to overload operation or long-term operation of the transformer. This has the effect of providing a highly reliable gas insulated transformer that maintains excellent cooling performance.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the gas insulated transformer of the present invention, FIG. 2 is a sectional view showing another embodiment of the invention, and FIG.
The figure is a sectional view showing the configuration of a conventional gas insulated transformer. DESCRIPTION OF SYMBOLS 1... Leg of iron core, 2... Metal sheet, 3... Insulating sheet, 4... Low voltage winding, 5... High voltage winding, 6...
...Cooling duct 1~. 7...Pump, 8...Coagulant l1i
5 equipment, 9... cooling water pipe, 10... refrigerant tank, 11
...Liquid pipe, 12...Insulated pipe, 13...Tank, 20...Motor, 21...Power source, 22-...
Changeover switch, 30a, 30b, 30G, 30d...
・Switching valve, 31.32...Piping.

Claims (4)

[Claims] (1) In a gas insulated transformer that has a winding and an iron core built in a tank, an insulating gas such as SF_6 gas as an insulating medium, and a cooling circulation system separated from the insulating gas, the cooling circulation A gas insulated transformer characterized in that the system is provided with means for reversing the direction of refrigerant circulation. (2) A gas insulated transformer in which the winding is a foil-wound winding in which a sheet-like conductor and a sheet-like insulator are wound in an overlapping manner. (3) The gas insulation according to claim 1 or 2, wherein the means for reversing the circulation direction of the refrigerant is provided with a changeover switch for switching the rotation direction of the motor on the motor that drives the pump. transformer. (4) Claim 1, in which the means for reversing the circulation direction of the refrigerant is provided by two pipes each having a switching valve between the liquid guide pipes arranged above and below the windings. Or the gas insulated transformer according to item 2.