JPS60730B2 - oil-filled bushing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil-filled bushing, and more particularly to an improved oil-filled bushing that has a high withstand voltage against DC voltage.

For example, the structure of general oil-filled bushings, which are used for parts that penetrate from the atmosphere into the oil in a tank, such as transformer bushings, is to wrap multiple layers of insulating paper and metal foil alternately around a central conductor. A cylindrical support metal fitting that is grounded is placed, air is removed from above and below, the pipe and oil are removed, the pipe is covered, and the inside is filled with insulating oil.

Each layer of metal foil forms the same cylindrical capacitor cone, and the length of the foil is sequentially varied in the axial direction so that each layer has approximately the same capacitance, thereby equalizing the stress applied to each layer of insulating paper. , it has the required voltage resistance characteristics with respect to the applied voltage. In recent years, with the practical application of DC power transmission, oil-filled pushers for use in DC lines have become necessary as bushings for conversion transformers and smoothing reactors.

However, in general, AC voltage is distributed according to the inverse ratio of the dielectric constant of the material, whereas DC voltage is distributed according to the resistance ratio of the material, so even in structures with insulating creepage, such as bushings, the voltage distribution is different between AC and DC. occurs. Therefore, due to this difference in voltage distribution, the dielectric strength of conventional oil-filled bushings used in DC lines decreases significantly, and they cannot be used as is. The present invention has been made in view of the above points, and an object of the present invention is to provide a fine-insulated bushing that has a high withstand voltage not only for alternating current voltage but also for direct current voltage and has stable insulation performance.

Embodiments of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a tank filled with insulating oil, and 11 is an oil-filled bushing that is attached to the tank 1 and penetrates from the atmosphere into the oil in the tank. Although not shown in the drawings, the oil-filled bushing 11 has a capacitor cone formed by alternately wrapping insulating paper layers and metal foil around the center conductor in multiple layers, and has a ground cone fixed to the tank 1 on the outside. The potential mounting bracket 12 and its top and bottom are vented, the tube 13 is drained with oil, the tube 14 is installed and sealed, the air is vented, and the inside is filled with insulating oil from the conservator 15 provided at the top of the tube 13. be done. The upper part of the center conductor (not shown) is connected to an external terminal 16 provided on the conservator 15, and the lower part of the center conductor is connected to an inner end 17. The above structure is the same as that of a conventional general oil-filled bushing, but in the present invention, as shown in the figure, it is further submerged in oil, and cap-shaped barriers 21, 22 of different diameters, each made of an oil-immersed press board, are placed on the outside of the pipe 14. 23 is provided with a diameter of 0', its head is submerged in oil, and is inserted and fixed between the pipe 14 and the fitting 12, and each barrier 21, 22, 23 is
The cylindrical length of the barrier 21 on the innermost side, that is, on the high-pressure side is the longest, and the barriers 22 and 23 on the outside thereof are sequentially shortened. In such a configuration, when a DC voltage is applied, the resistance ratio between the oil-immersed barrier and the insulating oil is 50 to 100.
Since this is extremely large, most of the applied voltage will be applied to the barrier, but the dielectric strength of the barrier (100 to 13 plates V' side) is greater than the dielectric strength of the insulating oil (3 to 5 KV/side).
is significantly high, improving the overall dielectric strength.

Furthermore, by making each barrier longer on the inner side (higher voltage side), the potential distribution becomes more uniform and the insulation creeping distance becomes longer, so that the dielectric strength can be further increased. The inventor experimentally determined the potential distribution of a DC voltage using the Bushing model shown in FIGS. 2a and 2b.

Figure a shows a capacitor cone 102 around the center conductor 101.
The potential distribution when a DC voltage is applied when the end of the bushing model with the Figure b shows the potential distribution without the barrier. Experimental results using this model revealed that by providing a barrier, the DC withstand voltage was approximately twice as high as that without the barrier.

Note that the impulse withstand voltage was improved by about 30%, although there was no significant effect as in the case of the DC voltage. As described above, according to the present invention, the oil-filled bushing is submerged in oil, and by providing a plurality of cap-shaped barriers concentrically on the outside of the pipe, the DC withstand voltage is significantly improved, making it stable as an oil-filled bushing for use in DC lines. This has the effect of providing excellent insulation performance.

[Brief explanation of the drawing]

FIG. 1 is an overall view showing an embodiment of an oil-filled bushing according to the present invention, and FIGS. 2A and 2B are explanatory diagrams showing DC voltage distributions according to models of an oil-filled pushing of the present invention and a general oil-filled pushing. 11...Oil-filled bushing, 12...Mounting bracket,
14... Oil drainer, pipe, 21, 22, 23...
Barya. Figure 2 Figure 1

Claims (1)

[Claims] 1. In an oil-filled bushing that penetrates from the atmosphere into the oil in a tank, a plurality of cap-shaped barriers of different diameters are provided concentrically surrounding the oil-filled bushing from the end of the mounting bracket of the oil-filled bushing to the oil-filled insulator pipe. The oil-filled bushing is characterized in that the head of the barrier is interposed between the insulator pipe and the fitting, and the cylindrical portion of the barrier is formed such that the innermost portion is longer and the outermost portions are sequentially shorter.