JPS60193316A - Direct current oil filled electric apparatus - Google Patents

Abstract

PURPOSE:To improve withstand voltage by enveloping a connecting part with three layer cylindrical insulation barriers which are gradually lower in height from the external layer and have a through hole at the bottom surface for a lead wire when an insulated high voltage lead wire is connected to the lower terminal of a bushing in a bushing pocket. CONSTITUTION:A bushing pocket 12 is welded on the grounded tank of a direct current oil filled transformer, a bushing 13 is penetrated in the pocket, the lower terminal 14 of the bushing is projected in the pocket 12 where insulation oil connected to within the tank is filled. A winding housed in the tank and the terminal 14 are connected with an insulated high voltage lead wire 16 consisting of a lead wire 16a covered with an insulation layer 16b and the connecting part is enveloped with an insulation shield 15. Then, the connecting part is enveloped with cylindrical three layer insulation barriers 18a-18c and the barriers are made gradually lower in height from the external layer. Insulation bottom plates 19a-19c with through holes each for the lead wire 16 are also provided at the bottom and circular insulation plates 21a and 21b are further fixed on the lead wire 16 between the bottom plates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to DC oil-filled electrical equipment, and more particularly to an improvement in the insulation structure near the connection portion with an insulated high-voltage lead wire in the lower part of the bushing.

[Technical background of the invention and its problems]

Recently, the development of DC power transmission has been progressing due to its advantages such as low construction cost and advantageous for transmitting large amounts of power over long distances.

Among these DC power transmission equipment, many DC oil-filled electric devices, such as transformers for DC power transmission, have an oil-filled and insulated structure. Such an oil-filled insulated structure is designed based on a transformer for AC power transmission, while solving the insulation problem peculiar to a transformer for DC power transmission.

However, in recent years, there has been an increase in DC transmission voltage and power transmission capacity, and in order to cope with these problems, high-voltage, large-capacity transformers are being considered for DC power transmission transformers. ing. In this case, a major problem is that of DC withstand voltage as the voltage increases.

As is well known, the voltage distribution of DC voltage is determined by the insulation resistivity of the material. This results in a large difference in voltage distribution compared to cases where the voltage distribution is determined by the dielectric constant of the material, such as with AC voltage. In terms of material strength, insulating oil is extremely weak compared to oil-impregnated paper in the case of DC voltage. On the other hand, in the case of AC voltage, the insulating oil and oil-impregnated paper are about the same in tl, or the oil-impregnated paper exhibits slightly stronger characteristics.

The DC withstand voltage of insulating oil is lower than the AC withstand voltage, and the DC withstand voltage of oil-impregnated paper is several times higher than the AC withstand voltage. For this reason, DC insulation structures that take advantage of the characteristics of insulating materials and potential distribution have been devised and put into practical use.

However, the insulation structure of transformers for AC power transmission, which did not pose any problems above, may become a problem in transformers for DC power transmission. In the transformer,
This is the connection between the insulated high-voltage lead wire connected to the coil of the transformer body and the oil-filled bushing, or the area around the insulation shield of the oil-filled bushing. In these parts, the first
As shown in the figure, the oil-filled side of the oil-immersed pusher, that is, the lower terminal 2, is connected to the insulated high-voltage lead wire 3 derived from the transformer main body coil (not shown), and the electric field around this connection part 4 is alleviated. Insulating shield 5 to lower terminal 2
Connect to. Further, the oil-filled bushing accommodates a center conductor 7 having an insulating core 7a inside the lower insulator tube 6, and is filled with insulating oil 8. In the electric field distribution 9 near the connection portion 4, there is a significant concentration of the DC electric field as shown by the dotted line, and there is a problem that needs to be resolved in terms of insulation.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and an object thereof is to provide a DC oil-filled electric device having an excellent DC withstand voltage and a simple 14ff structure.

[Summary of the invention]

In order to achieve this object, the present invention provides a plurality of insulating barriers so as to cover the connection portion between the insulated high-voltage lead wire led out from the coil of the electrical equipment main body and the lower end of the oil submerged side of the bushing. are arranged concentrically around the bushing, and these insulating barriers are arranged in such a way that the height of the outer insulating barrier in the axial direction relative to the bushing is adjusted in order, and an insulating bottom plate with four high voltage lead wires inserted through each insulating barrier is installed. The present invention is characterized in that it has an excellent DC needle's pressure and a simple structure by sequentially providing an insulating plate through which an insulated high-voltage lead wire is closely attached and penetrated between each insulating bottom plate.

$a11! It is preferable that the insulating plates are fixed so that the insulated high-voltage lead wires closely penetrate through the respective insulating bottom plates of the insulating barrier (i) at a position approximately halfway between the respective insulating bottom plates of the insulating barrier (i) and are perpendicular to each other.

It is preferable that the diameter of each insulating plate is approximately equal to the diameter of each insulating bottom plate located on the lower end side of the bushing.

[Embodiment of the Invention] Hereinafter, an embodiment of the DC oil-filled electrical equipment of the present invention will be described with reference to FIGS. 2 to 5. DC oil-filled electrical equipment includes, for example, transformers, reactors, and bushings, and among these, the DC oil-filled transformer will be explained. In FIG. 2, a transformer main body, that is, a coil Ilb wound around an iron core 11a, is housed inside a transformer tank 11, a bushing 13 is attached to a bushing pocket 12 attached to the transformer tank 11, and a bushing 13 is attached to a bushing pocket 12 attached to the transformer tank 11. The tank 11 and the bushing pocket 12 are filled with insulating oil 11c.

The F end of the bushing 13, that is, the lower terminal 1 on the oil side
4 is attached with an insulating shield 15, and this lower terminal 1
4 and coil llb are connected by an insulated high voltage lead wire 1G. The vicinity of the connecting portion 17 between the insulated high-voltage lead fa16 and the lower terminal 14, the outer periphery of the insulating shield 15, and the oil side of the bushing 13 are provided so as to be surrounded by an insulating barrier 18, as will be described later.

In addition, in FIG. 3, the lower part of the bushing 13, that is, the oil-submerged side, houses a center conductor provided with an insulating core (not shown) inside the oil-submerged insulator tube 13a, and this center conductor is connected to the lower terminal 14. The inside of the lower insulator tube 13a is filled with insulating oil. The insulating shield 15 includes an insulating material layer 15b formed by wrapping an insulating material such as insulating paper around the outer periphery of the ring-shaped conductor 15a, and a mounting bracket 15c connected to the lower terminal 14 of the bushing 13 to the ring-shaped conductor 15a. Mounted via. Further, the insulated high-voltage lead wire 16 has an insulating layer 16b formed by winding, for example, oil-impregnated insulating paper around the lead wire 16a, and connects the coil (see FIG. 2) and the lower terminal 14 via the mounting fitting 14a.

The insulating purrier 18 is constructed by fixing insulating bottom plates to a plurality of cylindrical parts using a fibrous insulating material, for example, presspod, and providing insulating plates between the insulating bottom plates. In the illustrated example, three insulating purriers 18, that is, three layers will be explained.

In FIG. 3, the first layer, that is, the innermost insulating purrier 18-1 surrounding the connection portion 17 of the bushing 13
The cylindrical portion 18a and the insulating bottom plate 19a are separated. The cylindrical portion 18a is fixed to the outer periphery of the insulating shield 15 by winding a press rod, for example.

An insertion hole 2o is formed in the insulating bottom plate 19a, and this insertion hole 20
With the insulated high voltage lead wire 16 inserted through the cylindrical part 18
The insulating bottom plate 19a is fixed with adhesive or insulating bolts so as to close the lower side of the insulating bottom plate 19a in an oil-tight manner.

The second or intermediate insulating parrier 18-7 is composed of a cylindrical portion 18b and an insulating bottom plate 19b.

The cylindrical portion 18b can, for example, support a presspod (
(not shown) is wound and fixed, and this cylindrical part 18
The insulating bottom plate 19b is fixed with adhesive or insulating bolts so as to close the lower side of the insulating bottom plate 19b so as to make the periphery oil-tight. Further, an insertion hole 20 is formed in the insulating bottom plate 19b, and the insulated tooth lead wire 16 is inserted into the insertion hole 2o.

Furthermore, the third layer, that is, the outermost layer of insulating purrier 18-s
consists of a cylindrical portion 18c and an insulating plate 19c.

The cylindrical portion 18c is fixed by winding, for example, a press rod around the outside of the cylindrical portion 18b of the insulating purrier 18-7 via a spacer (not shown), and an insulating bottom plate is attached to close the lower side of the cylindrical portion 18c. 19c is fixed around the area with adhesive or insulating bolts so as to be oil-tight. Then, the insulated high voltage lead &! is inserted into the insertion hole 20 provided in the insulated bottom plate 19c. 16.

Then, on the insulated high voltage lead wire 16 attached in the direction along the central axis of the bushing 13, the insulated bottom plate 19a
An insulating plate 21a having approximately the same diameter as the insulating bottom plate 19a on the upper side, that is, the lower terminal 14 side, is provided at an intermediate position between the insulating bottom plate 19b and the insulating bottom plate 19b. The insulated high-voltage lead wire 16 is passed through the insulating plate 21a approximately at the center thereof, and the penetrating portion is fixed by wrapping an insulating tape 23, for example.

Further, an insulating plate 21b having a diameter approximately equal to that of the insulating bottom plate 19b on the upper side, that is, the lower terminal 14 side, is provided at a substantially central position between the insulating paper board 19b and the insulating bottom plate 19c.

An insulated high-voltage lead wire 16 is passed through the insulating plate 21h approximately at the center thereof, and the penetrating portion is fixed by wrapping an insulating tape 23, for example.

And insulating parliars 18-t, 18-t, 18
The cylindrical portions 18a, 18b, and 18c of the bushing 13 are sequentially increased in height in the axial direction toward the outside of the bushing 13, and the upper end of the cylindrical portion 18c is connected to the upper inner wall 12a of the bushing pocket portion 12. For example, it is fixed by tightening an insulating bolt (not shown).

Next, the effects of the present invention will be explained. By providing a plurality of insulating parriers 18-*, 18-t, 18-s, and insulating plates 21a and 21b at their respective intermediate positions, as in the present invention, it is possible to improve (See Figure 1) The bias in the DC potential distribution is eliminated. Further, the DC withstand voltage can be significantly improved.

Such an improvement in DC withstand voltage can be estimated from the creeping DC withstand voltage, ie, the results of a DC dielectric breakdown test, as shown in FIGS. 4 and 5.

FIG. 4 shows a case where there is no barrier as an insulating barrier between the upper electrode in the form of a flat disk and the lower electrode 8 which is considered to be in the shape of a wide flat plate. ,−, ,25−
, .

In this test, 25-5 were sequentially provided, a DC voltage was applied to the upper electrode A and the lower electrode B1, and the DC breakdown voltage was measured.

The test results are shown in FIG. In Fig. 5, the vertical axis shows the DC breakdown voltage ratio compared with the DC breakdown voltage when there is no barrier at all, and the horizontal axis shows the DC breakdown voltage ratio in order of zero, that is, no barrier, one barrier, two barriers, and three. Sheet,
If we take the number of pariahs as 4 and 5, the result will be as shown in the curve work. That is, as shown in the curved line, as the number of purriers increases, the DC breakdown voltage ratio increases. As described above, the effect that the barrier has on the DC withstand voltage is remarkable, and with five barrier layers, it is possible to obtain the effect that the DC breakdown voltage is approximately 1.8 times higher than that with zero barrier, that is, with no barrier.

As described above, according to the present invention, it is possible to improve the DC potential distribution and the DC withstand voltage at the lower end of the bushing on the oil side.

In addition, although the number of insulating purriers was explained as three,
The number of layers, that is, the number of layers is not limited, and similar effects can be obtained with other numbers of layers.

[Effects of the Invention] As explained above, according to the present invention, a plurality of insulating barriers are provided on the outer periphery so as to surround the lower end of the oil side of the bushing and the connection portion of the insulated high voltage lead wire, and the oil side of the bushing. By providing an insulating plate between the insulating bottom plates of the insulating barrier, it is possible to provide a DC oil-filled electrical device that can improve the DC potential distribution and the DC withstand voltage.

[Brief explanation of drawings]

Fig. 1 is a partially sectional front view and electric field distribution diagram showing the bushing connection part of a conventional DC oil-immersed transformer, Fig. 2 is a partially sectional side view of the DC oil-immersed transformer of the present invention, and Fig. 3 is Figure 2 is a sectional view of the bushing in oil, Figure 4 is an explanatory diagram showing the electrode arrangement in a DC dielectric breakdown test to see the effect of the insulating purrier of the present invention, and Figure 5 is the insulation in the electrode arrangement of Figure 4. FIG. 3 is a diagram showing a DC breakdown voltage ratio depending on the number of purriers. 11...Transformer tank, 11a゛iron core, 11b
・Coil, lie...Insulating oil, 12...Bushing pocket part, 13...Bushing, 14...Lower terminal, 15
... Insulating shield, 15a... Insulating layer, 16 ・
...Insulated high voltage lead wire, 16a...Lead wire, 16b
- insulating layer, 17... connection part, 18... insulating purrier, 18-+, 18-2, 18-a... cylindrical part, 19
-1.19-2, 19-s...Insulating bottom plate, 21a,
211) -insulating plate, 25-+, 25-2, 25-3, 25-, ,
25-,... Barrier, A. Upper type, To starvation, 13.
...lower electrode. Agent Patent Attorney Mr. Inoue Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) In DC oil-immersed electrical equipment that has a connection between the oil-immersed lower end of the bushing attached to the bushing pocket and the insulated high-voltage lead wire derived from the coil of the electrical equipment body, A plurality of insulating barriers are provided concentrically at a distance from each other around the bushing so as to cover the middle side and the periphery of the connection between the lower end portion and the insulated high voltage lead wire, and the plurality of insulating barriers are Each of the cylindrical portions is formed with a cylindrical portion and an insulating bottom plate, and each of the cylindrical portions is formed so that the height of the cylindrical portion located on the outside is JIIR higher than the bushing. The DC oil-filled DC oil-filled device is characterized in that the insulated bottom plates into which the insulated high voltage lead wires are inserted are fixed to each other, and insulating plates are provided between the insulated bottom plates in such a way that the insulated high voltage lead wires are passed through the insulated bottom plates in close contact with each other. electrical equipment. (2) The DC oil-filled electrical equipment according to claim 1, wherein the insulating plate is located approximately at the center between the insulating bottom plates and is provided approximately orthogonally to the insulated high voltage lead wire. (3) The DC oil-filled electrical equipment according to claim 1 or 2, wherein the diameter of the insulating plate is approximately equal to the diameter of the insulating bottom plate closer to the lower end of the bushing.