JPS61179511A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To minimize the increase in temperature of windings even if a pump has a trouble, by providing a plurality of units each consisting of a condenser, a refrigerant tank and a pump arranged in series, connecting them to each other by a common duct and connecting them to coils in a tank. CONSTITUTION:In a three-phase and three-leg foil-wound transformer, three sets of units each consisting of a pump 7, a condenser 8 and a refrigerant tank 10 arranged in series are connected to each other by means of a common duct 20 and are connected to three sets of coils 21, 22 and 23 within a tank 13. According to this construction, even if one of the pumps 7 is stopped by some problem, the other two pumps will continue to operate so that the amount of the refrigerant flowing through the three sets of coils 21, 22 and 23 within the tank 13 is reduced to 2/3 but not to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of 5'e Akira] The present invention relates to a foil-wound transformer in which a cooling duct is built into a winding formed by overlappingly wound a metal sheet and an insulating sheet.

[Technical front of the invention] A foil-wound transformer equipped with a foil winding has a good winding space factor;
Because it has characteristics that allow it to be made smaller and lighter, it has already been put into practical use and widely used in relatively low voltage, small capacity transformers of several KV or several hundred KVA.

Recently, in view of the excellent advantages of such foil-wound transformers, higher voltage and larger capacity transformers, such as 275KV and 300MV, have been developed.
Research is underway to expand its application to A-class transformers, but the biggest technical issue is how to improve the cooling capacity of the windings.
The issue is whether the winding can have high insulation capacity.

Although it has not yet been put to practical use in such high-voltage, large-capacity transformers, the cold W method for windings in foil-wound transformers incorporates cooling ducts within the windings to improve insulation properties. A so-called heat pipe type is being considered, which directly cools the heat generated from winding loss by feeding a high quality refrigerant.

FIG. 2 shows an example of a conventionally known foil-wound transformer of this type.

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 3, are wound around a leg 1 of an iron core. A hollow cooling duct 6 is built-in.

In the thin gap in the hollow part of the cold lug duct 6, fluorocarbon R-
A refrigerant such as 113 or Fluorinert FC75 is sealed in the refrigerant, which is circulated by the pump 7, and the heat generated within the winding is absorbed by the latent heat of evaporation of the refrigerant, and the vapor is cooled and condensed through the cooling water pipe in the condenser 8. ing. 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 cooling 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 vibrator 12 made of Teflon resin or the like. The liquid guide pipe 11 is also connected to the ground potential of the tank 13 and the like. 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. Furthermore, the insulation of each part of the winding is provided by the tank 13.
This is ensured by an insulating gas such as SF6 gas sealed inside.

The conventional foil-wound transformer described above is generally called a separate foil-wound transformer because the cooling system in which the refrigerant circulates and the insulating gas of the winding are completely separated.

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

That is, in the conventional foil-wound transformer as shown in Fig. 2, when the pump 7 stops due to a failure or the like, the refrigerant flowing in the thin gap of the cold section duct 6 stagnates due to convection, etc. As a result, the self-cooling capacity is significantly insufficient and the heat generated by winding loss cannot be cooled down, causing the temperature of the windings to rise and potentially causing serious damage to the transformer itself.

[Object of the Invention] The present invention was proposed in order to eliminate the drawbacks of conventional foil-wound transformers such as those described above. The object of the present invention is to provide a highly reliable foil-wound transformer that can minimize voltage rise.

[Summary of the Invention] The foil-wrapped transformer of the present invention has multiple units each consisting of a condenser, a refrigerant tank, and a pump connected in series, and is connected to each other by a common pipe. By connecting the refrigerant to the coil, even if one of the pumps fails, the refrigerant can be supplied by the other pump.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be specifically described based on FIG. Note that the same parts as those of the conventional foil-wound transformer shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, three sets of units in which a pump 7, a condenser 8, and a refrigerant tank 10 are arranged in series are connected to three sets of three separate foil-wound transformers with three legs through a common pipe 20. are connected to three sets of coils 21, 22, and 23.

In the foil-wound transformer of this embodiment configured in this way,
When one of the three pumps 7 breaks down and stops, the other two pumps are operating, so the three pumps in the tank 13
The flow rate of the refrigerant flowing through the coils 21, 22, 23 of the set does not become zero, but only needs to be reduced to 2/3. Generally, in substations where separate foil-wound transformers are used,
Since transformers are rarely operated with 100% load, even if the flow layer of refrigerant flowing through the coils is reduced to 2/3, the winding temperature may rise excessively and cause serious damage to the transformer. The risk of failure is extremely low.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but if an on-off valve is provided at the inlet or outlet of the pump 7, and the on-off valve is configured to close when the pump stops due to a failure or the like, Since the flow of refrigerant produced by other pumps is no longer bypassed through the stopped pump, the refrigerant can efficiently flow through the coil, increasing the cooling efficiency of the windings.

Furthermore, in the present invention, a plurality of pump units may be connected by a common pipe not only when there is a plurality of coils in the tank as shown in FIG. 1, but also when there is one coil.

[Effects of the Invention] As described above, according to the present invention, by connecting a plurality of condensers, refrigerant tanks, and pump units to the coil in the tank through common piping, even in the event of a pump failure, one winding can be used. This has the effect of providing a highly reliable foil-wound transformer that minimizes temperature rise and maintains high cooling efficiency.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the foil-wound transformer of the present invention;
FIG. 2 is a sectional view showing the structure of a conventional foil-wound 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, 7... Pump, 8... Condenser, 9
... Cooling water pipe, 10 ... Refrigerant tank, 11 ... Liquid guide pipe, 12 ... Insulated pipe, 13 ... Tank, 20
...Common piping, 21.22.23...Coil.

Claims (3)

[Claims] (1) A cooling duct is arranged inside a coil made by overlapping and winding a metal sheet and an insulating sheet, and a pump installed outside the tank circulates a refrigerant inside the cooling duct to cool the coil. The transformer is characterized in that a plurality of units are arranged in which the pump, the condenser, and the refrigerant tank are connected in series, and these units are connected to each other through common piping and connected to a coil inside the tank. Foil-wound transformer. (2) The foil-wound transformer according to claim 1, wherein a plurality of coils are disposed inside the tank. (3) The foil-wound transformer according to claims 1 and 2, wherein an on-off valve is provided at the inlet or outlet of the pump.