JPS6241407B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dry type gas-filled transformer, and more particularly to a sulfur hexafluoride gas-filled transformer having a winding structure insulated with a composite insulating layer. In electrical equipment, especially gas-filled transformers, if moisture exceeds a certain amount due to thermal decomposition of internal insulation or gas leakage, the insulation will undergo hydrolysis, resulting in a rapid decline in electrical and mechanical properties. . Therefore, selection of insulating materials used in this type of equipment and moisture management of the materials become important issues in detecting abnormalities in electrical equipment and preventing major accidents. In general, gas-filled transformers, particularly sulfur hexafluoride gas-filled transformers, have a winding structure in which insulating paper or insulating film is used as the insulating material, and the coil conductor is insulated with either of these materials. The former is highly hygroscopic and has a significant effect on electrical properties such as dielectric strength and mechanical properties, and has the disadvantage that maintaining these properties requires an increase in size. In contrast, the latter has been used more frequently in recent years because of its superior properties. However, in the case of a winding insulation structure using an insulating film, the insulating layers of the coil are in close contact with each other, so the gas flow that should be convecting inside the transformer becomes stagnant, and the film insulating layer is not cooled enough. There was a risk that the temperature would rise and the insulation would deteriorate. This becomes more noticeable in proportion to the thickness of the insulating layer constituting the winding. The present invention eliminates these drawbacks, and the insulating layer of the coil conductor has a highly durable wound structure with excellent heat resistance and mechanical strength.Moreover, it has a hexafluoride structure that improves gas convection and can be made smaller and lighter. The purpose is to provide a sulfur gas filled transformer. Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a sulfur hexafluoride gas filled transformer. In the figure, a transformer tank 1 is provided with an iron core 2 fixed therein, a coil 3 is wound around the iron core 2, and a gas body 6 of sulfur hexafluoride is enclosed. A bushing 4 is provided at the top of the tank 1 to allow the terminals of the insulated windings to be drawn out of the tank, and the internal insulation of the transformer is cooled by a cooling device 5. FIG. 2 shows an example of a transformer winding constructed by winding the coil 3 shown in FIG. 1 and covering it with a composite insulating layer of synthetic resin film 7 and synthetic paper 8, which are thin film materials. be. Here, as the thin film insulating material, for example, the synthetic resin film 7 is a polyethylene terephthalate film (hereinafter referred to as polyester film) having a thickness of 12 to 50 μm, and the synthetic paper 8 is a polyethylene terephthalate film (hereinafter referred to as a polyester film) having a thickness of 10 to 75 μm.
The composite insulating layer can be constructed using commercially available aramid paper, such as synthetic paper of m. Comparing the mechanical strength of the insulating layer according to the present invention with that of the conventional one, it was found that the case of a single layer using polyester film as the conventional insulating film and the case of the above-mentioned composite insulating layer were sealed against sulfur hexafluoride gas. The following table shows changes in the mechanical properties of these insulators under long-term high-temperature conditions.

[Table] Therefore, this table shows the heat resistance of the tensile strength retention rate and elongation retention rate of the insulator depending on whether or not aramid paper, that is, synthetic paper is used together. Also, the thickness of the polyester film at this time is 25μ
It is m. As is clear from the table, at the same temperature, the mechanical strength of both samples is approximately the same depending on the length of the period. Next, when the condition temperature is increased, the rise in temperature of the coil conductor can be suppressed by the synthetic paper 8 serving as the upper layer in the composite insulating layer. Therefore, the actual mechanical strength of an insulator can be determined by considering a single layer at 140°C for 90 days and a composite insulating layer at 120°C for 90 days. As shown in the table, the results show that the composite insulating layer maintains higher mechanical strength than a single layer. According to more detailed measurements, the difference in mechanical strength between the two is remarkable, especially between the insulating layers where gas does not easily flow. This difference in properties between the two shows similar results when measuring the impulse breakdown voltage or AC breakdown voltage of the windings, and the composite insulating layer is a good insulator in terms of electrical properties as well. From the viewpoint of workability, the composite insulating layer protects the polyester film layer from wrinkles, scratches, etc. with the synthetic paper outer cover, and prevents deterioration of the electrical characteristics. In other embodiments of the above-mentioned composite insulating layer, the outer sheath of the polyester film is made of creped synthetic paper, polyester nonwoven fabric, or a laminate structure of heat-resistant insulating paper and creped insulating paper. constitute a composite insulating layer,
Even when similar measurements and characteristics studies are performed, results are obtained that fully satisfy the above-mentioned combination of synthetic paper. As described above, the present invention has a structure in which a synthetic resin film and synthetic paper, which are thin film materials, are selected as the insulating materials of a sulfur hexafluoride gas-filled transformer, and the coil conductor is insulated by these composite insulating layers. The transformer winding is highly heat resistant and has excellent mechanical and electrical properties, making it smaller and lighter.Furthermore, the gas convection between the insulation layers is improved, so the insulation is sufficiently cooled. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a gas-filled transformer according to the present invention, and FIG. 2 is a sectional view showing an embodiment of the transformer winding according to the present invention. 1... Transformer tank, 2... Iron core, 3... Coil, 4... Bushing, 5... Cooling device, 6...
Gas body of sulfur hexafluoride, 7...Synthetic resin film layer, 8...Synthetic paper layer.

Claims (1)

[Claims] 1 Gas can flow through a transformer tank filled with insulating gas, an iron core fixed in this tank, and a composite insulation layer made of thin film materials of synthetic resin film and synthetic paper wound around this iron core. a winding with an insulated coil conductor; a bushing that allows a terminal of the winding to be drawn out to the outside of the tank;
A sulfur hexafluoride gas filled transformer comprising a cooling device for cooling the heated insulating gas and the like.