JPS6212645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In general, the primary coil of an oil-immersed high voltage current transformer is composed of a multilayer capacitor cone for insulation, so as to maintain an appropriate potential distribution. In the present invention, an oil layer is provided between the layers of the capacitor cone, through which insulating oil flows by convection, and the heat dissipation effect of the primary coil is obtained by the flow of this insulating oil.

Figure 1 shows an example of the basic configuration of an upright high-voltage, large-current oil-immersed current transformer that has been commonly used in the past.
is a primary coil, 2 is an annular iron core, and 3 is a secondary coil wound around the iron core 2.

Here, the primary coil 1 consists of a linear lead-out conductor 4, a coil-part conductor 5 wound in one turn, and an insulating layer 6 covering these conductors, and the lead-out conductor 4 is arranged coaxially in double layers. The coil part conductor 5 is also made of a tubular conductor. The insulating oil flows by convection from between the inner and outer tubular conductors 41 and 42 of the drawer section to the coil section tubular conductor 5 and then again to the inner tubular conductor 41 of the drawer section to cool the primary coil.

On the other hand, the insulating layer 6 is made of a capacitor cone as described above, and FIG. 2 shows a longitudinal cross-sectional view of the lead-out portion of the primary coil 1, and FIG. As can be seen, the insulating layer 6 has multiple layers, three in the case shown
1, 62, and 63, and electrodes 71, 72, and 73 provided between each insulating layer and outside the outermost insulating layer, respectively. Note that the outermost layer electrode 73 is grounded by providing a lead wire (not shown).
These insulators, electrodes, and the tubular conductor 42 on the outside of the lead-out part form a plurality of capacitors connected in series with each other, and the voltage between the primary conductor and the ground is divided by the capacitor partial voltage, and each insulating layer shares its share. This is done to equalize the voltages applied and to make the potential distribution of each part appropriate.

Note that in FIG. 3, the insulating layers are shown in a circular shape in which the central tubular conductor 5 is sequentially offset, but this is due to the following circumstances. That is, in the manufacturing process of the primary coil, a tape-shaped insulating paper of a constant width is sequentially wound around the conductor 5 to form an insulating layer. On the side A (in the figure), the insulating paper is stacked in multiple layers and has a larger thickness than on the outside (side B in the figure), resulting in a structure in which the thickness of the insulating layer is uneven as shown in the figure. Note that the thickness of the insulating layer necessary for insulating the primary coil is such that the thickness on the outer B side is, of course, sufficient. The same applies to FIG. 5, which will be described later.

In this case, the heat generated in the primary coil is diffused and cooled by the aforementioned convection of the insulating oil and heat conduction through the insulating layer of the capacitor cone. However, as the insulation class increases, the number of insulation layers also increases, and the thickness of each insulation layer also increases. Therefore, even if the current value is the same, if the insulation class is higher,
For primary coils of the same structure and dimensions, the heat dissipation effect due to convection of insulating oil is almost the same;
Since the heat dissipation effect due to heat conduction through the insulating layer decreases in inverse proportion to the thickness of the insulating layer, the temperature increase value increases.

Therefore, in order to suppress the temperature rise within the specified value,
It is necessary to take measures such as increasing the cross-sectional area of the conductor of the primary coil and lowering the resistance value to reduce the amount of heat generated, or providing a heat sink, which significantly increases manufacturing costs. Furthermore, if the cross-sectional area of the conductor of the primary coil is increased, the outer diameter becomes large, which causes problems such as it cannot be accommodated in a standard-sized insulator tube, and a special-sized insulator tube is required.

The present invention eliminates these drawbacks and provides a primary coil with a structure that increases the heat dissipation effect, which will be explained below.

In the present invention, a gap is provided around the conductor of the primary coil and between the insulating layers, and the insulating oil is made to flow through this gap by thermal convection, so that effective heat dissipation is performed by this oil layer. Make it. However, simply providing an oil layer disturbs the potential distribution due to the capacitor partial pressure. That is,
The oil-impregnated paper, which is an insulator, and the insulating oil flowing through the gap have different dielectric constants, and because the dielectric constant of the insulating oil is small, the potential gradient in the oil layer increases, which may cause partial discharge within the oil layer. be. This may lead to dielectric breakdown, and the reliability of the insulation will drop significantly.

Therefore, in the present invention, the outside and inside of the oil layer are respectively covered with electrodes, and both electrodes are connected to each other to have the same potential. That is, the oil layer is sandwiched between electrodes having the same potential. By doing this, the oil layer does not have any effect on the potential distribution,
The potential distribution remains the same as without the oil layer.

4 and 5 show embodiments of the present invention,
A longitudinal cross-sectional view of the linear lead-out portion and a cross-sectional view corresponding to the AA' cutting line of the coil portion in FIG. 1 are shown, respectively.

In both figures, gaps 81, 82, and 83 are provided between the innermost insulating layer 61 and the tubular conductor 42 and coil conductor 5 of the drawer section, and between the insulating layers 61, 62, and 63, respectively.
Further, electrodes 91, 92, 93, 94, and 95 are provided to respectively cover the inner surface of the innermost insulating layer 61, the outer surface of the insulating layer 61, the inner surface of the insulating layer 62, and the outer surface of the insulating layer 62 and the inner surface of the insulating layer 63. establish. Incidentally, on the surface of the outermost insulating layer 63, an electrode 73 having a conventional capacitor cone structure, that is, the same as in the case of FIG. 3, is provided and grounded. Next, conductor 42 or 5 and electrode 91, electrodes 92 and 9
3, and electrodes 94 and 95 are connected to each other by lead wires or the like to have the same potential. In this way, an oil layer can be formed without fear of disturbing the potential distribution.
The heat dissipation effect can be enhanced.

Various methods can be considered as means for providing gaps for forming an oil layer. In other words, a gap is created by inserting a spacer between the layers of the insulating material, and this spacer can be achieved by, for example, using a string or wire and winding it at appropriate intervals. You can also do that. Note that this spacer can be made of either an insulator or a conductor depending on the situation.

It should be noted that these gaps do not necessarily have to be provided between the innermost insulating layer and the conductor and between all the insulating layers, but are provided in appropriate portions, and electrodes as capacitor cones are provided in other areas. In this case, it is of course effective for heat dissipation to provide the gap close to the conductors 42 and 5.

By providing the oil layer in this way, the primary coil is effectively cooled, and the temperature rise in each part is extremely reduced. Therefore, the outer shape of the primary coil can be made almost the same size as the conventional one.

In this way, by providing a gap around the conductor of the primary coil and in the insulating layer to allow the insulating oil to flow, and by sandwiching the inside and outside of this oil layer with electrodes of the same potential, it is possible to prevent the potential distribution from being disturbed. Effective heat dissipation by the insulating oil can be performed without fear. Therefore, even if the insulation class becomes higher, there is no need to increase the cross-sectional area of the conductor to reduce the amount of heat generated due to the decrease in thermal conductivity caused by thickening the insulation layer as described above. The cross-sectional area remains the same and it can be housed in a standard-sized insulator tube.

In addition, the reason why the insulating layer has a sequentially uneven shape with respect to the central conductor 5 in FIG. 5 is because the insulating layer is constructed by winding a tape-shaped insulating paper with a constant width, as described above. This is because the insulating paper is wound in multiple layers on the center side of the next coil, deeper than on the outside. For this reason, the center side of the primary coil, that is, the portion on the A side shown in the figure, has an excessive insulation thickness compared to the outer side, that is, the B side, so there is a possibility that the temperature rise will be large. Therefore, by providing the oil layer according to the present invention to enhance the heat dissipation effect, it is possible to prevent an excessive rise in temperature.

Furthermore, in the above description, the linear lead-out portion of the primary coil is made of a coaxially arranged double tubular conductor, and the coil portion conductor is also a tubular conductor. Regardless of the structure and the shape of the coil portion conductor, the present invention can be applied to any structure of the lead-out portion and the coil portion conductor.

As detailed above, in a capacitor cone primary coil, an oil layer is appropriately provided between the insulation layers, and the inner and outer sides of the oil layer are sandwiched between electrodes of the same potential, thereby achieving a large heat dissipation effect without disturbing the potential distribution. In particular, it can be applied to high-voltage, large-current current transformers to obtain great effects.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the basic structure of this type of current transformer, Fig. 2 is a longitudinal sectional view showing an example of the conventional structure of the linear lead-out portion of the primary coil, and Fig. 3 is a sectional view showing the basic structure of this type of current transformer.
FIG. 4 is a longitudinal cross-sectional view of a linear lead-out portion of a current transformer according to an embodiment of the present invention, and FIG. FIG. 3 is a cross-sectional view showing the structure of a coil portion according to an embodiment of the present invention taken along cutting line AA' in the figure. 1...Primary coil, 2...Iron core, 3...Secondary coil,
4... Drawer part conductor, 41, 42... Tubular conductor, 5...
Coil part conductor, 6, 61, 62, 63...insulating layer,
71, 72, 73, 91, 92, 93, 94, 9
5... Electrode, 81, 82, 83... Gap.

Claims (1)

[Claims] 1 A gap is provided at least around the conductor or between the insulating layers of the condenser cone-shaped primary coil to allow insulating oil to flow, and the inner and outer surfaces of the oil layer formed in the gap are covered with electrodes having the same potential. current transformer.