JPS5850106B2 - High voltage AC/DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-voltage AC/DC converter, and particularly to an insulating structure such as an oil-cooled silicate valve having a DC high-voltage charging section.

Figure 1 shows the conventional structure of an oil-cooled syrisk valve as a high-voltage oil-filled AC/DC converter.

In this figure, a tank 1 is filled with insulating oil, and a pedestal (stage) 3 in which a series connection of high-voltage, large-current thyristors 2 is attached is supported by a support 4.

Further, a bushing 5 is installed above the tank 1 for connection with external equipment.

By the way, high DC voltages, AC voltages, and impulse voltages with complex waveforms are applied to the area surrounded by the broken line in Figure 1. In this insulation structure, the area surrounded by the broken line is insulated only with insulating oil. It is covered.

For this reason, (1) as the operating voltage increases, the distance between the pedestal 3 and the tank 1 must be lengthened due to the withstand voltage of the insulating oil; There are concerns about the effect of dust on the withstand voltage, and there are drawbacks such as a lack of insulation stability.

In particular, due to the drawback of item (1), it is inevitable that the shape of the tank 1 will become larger, which will lead to an increase in the amount of oil.
Transportation methods are limited and there is also the problem of increased costs.

The structure shown in FIG. 2 can be considered as a solution to these problems.

In this figure, a paper-wrapped shield 10 (a conductor wrapped with oil-impregnated paper) is provided between the pedestal 3 and the tank 1.

If this structure is adopted, the potential distribution will be 3 degrees as shown by the dotted line.In other words, since the DC potential distribution is determined by the resistance of the insulator, the paper roll shield 1, which has a higher resistivity than the insulating oil,
The potential is concentrated on the oil-impregnated paper at 0.

Therefore, the electric field applied to the insulating oil between the tank 1 and the pedestal 3 should be relaxed.

However, due to the influence of potential concentration on the oil-impregnated paper of the paper-wrapped shield 10, potential concentration also occurs in the insulating oil between the paper-wrap shields 10, so the oil, which has a lower withstand voltage than the oil-impregnated paper, partially breaks down. Furthermore, in the case shown by arrow 11, there is a risk that the entire path will be destroyed.

The present invention aims to eliminate the above-mentioned drawbacks and provide an insulating structure for a high-voltage AC/DC converter that makes it possible to downsize the tank.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 3, a molded press pod 20 is attached to the end of each pedestal 3, and a paper roll shield 10 is attached to this press pod 20 via an insulated cross arm 21.

°And the presspod 20 and armrest 21 are insulated bolts 22
This allows it to be attached to the pedestal 3.

At this time, the paper roll shield 10 is provided above the top pedestal 3, below the bottom pedestal 3, and between each pedestal 3 in order to insulate it from the tank 1. Two paper roll shields 1 are placed on the bottom pedestal 3 as shown in the figure.
0, one paper roll shield 10 will be attached to each of the other frames 3.

In this way, the paper-wrapped shield 10 and the molded press pods 20 are arranged at equal intervals on the opposite side of the tank.
During a DC withstand voltage test (all stages of the pedestal 3 have the same potential), the potential distribution between all shields becomes the same.

Note that the other details are the same as in FIG. 1.

When a device with such an insulating structure is placed in a tank 1 similar to that shown in FIG. 1 and subjected to a DC withstand voltage test, the potential distribution becomes as shown by the equipotential lines shown by dotted lines in FIG. 4.

(60% and 100% in the figure indicate the potential level of each equipotential line, and 0 is the ground level).

In other words, the pedestal 3, armrest 21, and paper shield 10 are at equal potential, and the DC potential distribution is determined by the resistance of the insulator. This is limited to the oil-impregnated paper on the side of the paper-wrapped shield 10 facing the tank 1 and the molded presspod 20 at the tip of the pedestal 3 (on the side facing the tank 1).

Therefore, the potential is not very concentrated in the oil between the respective paper-wrapped shields 10 and between the paper-wrapped shields 10 and the molded presspod 20.

Here, since the oil-impregnated paper and presspod have a higher DC withstand voltage than the insulating oil, they can sufficiently withstand even if the electric potential concentrates on the oil-impregnated paper of the paper-wrapped shield 10 and the molded presspod 20 as described above.

As a result, the gradient of the potential in the insulating oil between the tank 1 and the pedestal 3 is relatively reduced (the distance between the equipotential lines becomes larger), so the DC withstand voltage strength between the tank 1 and the pedestal 3 is improved. do.

Therefore, the tank 1 and the frame 3 can be brought closer to each other, so that the tank 1 can be made smaller.

Furthermore, for alternating current and impulse voltages, the potential is determined by the inverse ratio of the permittivity of each insulator, so the potential is not concentrated unilaterally on the oil-impregnated paper, the molded presspod 20, and the oil, and the paper-wrapped shield 10 It has good insulation properties due to the effect of

As explained above, according to the above embodiment, the insulation distance between the mount 3 and the tank 1 of the oil-cooled silice valve can be greatly reduced compared to the case where insulation is performed only with insulating oil.

Therefore, it is possible to reduce the shape of the tank 1 and the amount of oil in the tank, which is advantageous for transportation and reduces costs.

Further, by providing the paper-wrapped shield 10, the movement of dust in the insulating oil can be reduced, so that the influence of dust on the withstand pressure can also be alleviated.

Note that a shield insulated with synthetic resin such as epoxy may be used instead of the paper-wrapped shield 10, and a molded article made of synthetic resin such as epoxy may be used instead of the molded press pod.

Furthermore, the present invention is similarly applicable to the case where an insulating gas such as SF6 gas is used instead of insulating oil.

As described above, according to the present invention, an insulating structure for a high voltage AC/DC converter is obtained that allows the size of the tank to be reduced.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the insulation structure of a conventional oil-cooled syrisk valve, Fig. 2 is a sectional view showing the voltage distribution of an oil-cooled syrisk valve when a conventional paper-wrapped shield is installed, and Fig. 3 is a sectional view showing the insulation structure of a conventional oil-cooled syrisk valve. FIG. 4 is a sectional view showing an embodiment of the insulation structure of the high voltage AC/DC converter according to the invention, and FIG. 4 is a sectional view showing the potential distribution in the embodiment. 1...tank, 2...cyrisk, 3
... Frame, 4... Support, 5...
・Bushing, 10...Paper shield, 20・
...Molded press pod, 21... Bracelet.

Claims (1)

[Scope of Claims] 1. A high-voltage AC/DC converter that includes a high-voltage charging section with multi-tiered pedestals housed in a tank filled with insulating oil or gas, wherein each part of the pedestal facing the tank is insulated. In addition to attaching the cover, insulating-coated shields are placed above the top mount, below the bottom mount, and between each mount on the side facing the tank of the high voltage charging section, and these shields are A high-voltage AC/DC converter characterized in that each is maintained at the same potential as one of the nearby frames.