JPH09153314A - Oil-filled bushing for direct current - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve not only the fixing method of a barrier and also the potential distribution, to reduce weight, and to improve remarkably the direct current withstand voltage. SOLUTION: This bushing is used as a lead-out from a direct current oil-filled apparatus and is constituted such that a center conductor whose outer circumference is covered with insulating paper is inserted through within a porcelain tube 1a and that an annular shield 7 for relaxing electric field is connected electrically and mechanically to an end part of a bushing proper 1 in which insulation oil is filled. In this event, first barriers 10a, 10b are respectively provided on the outer circumference side of the shield 7 concentrically with the shield 7 in order to improve electric potential distribution in the longitudinal direction of the bushing proper 1 and to prevent electric field concentration on the shield 7, and disc-shaped second barriers 14a, 14b are provided which contact with the first barriers 10a, 10b and the porcelain tube 1a, close an upper opening part of each of the first barriers, and fix and support the first barriers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current oil-filled bushing used for leading out leads of direct current electrical equipment such as transformers for direct current transmission and direct current reactors.

[0002]

2. Description of the Related Art In recent years, in long-distance power transmission, interconnection of different frequencies, etc., DC power transmission, which has many advantages in system operation, has been applied in various fields. Generally, in a DC power transmission system, an AC / DC converter is installed at a line end, and a converter that converts AC into DC at the power transmitting end and converts DC into AC at the power receiving end is provided at the AC / DC converting station.

Further, a transformer for transformer, a smoothing reactor, a lightning arrester, a thyristor valve, etc. are installed at the AC / DC converter. These transformers for transformers and smoothing reactors are of the oil insulation type, which has a long history of operation, and the air insulation type is often used for lightning arresters and thyristor valves. For this reason, not all devices can be stored in a single insulating oil container, and a large number of drawer bushings are required.

FIG. 5 is a block diagram of a general DC bushing conventionally used. Note that FIG. 5 shows the shield in oil at the end of the bushing and the periphery of the insulating lead. FIG.
In FIG. 1, reference numeral 1 denotes a bushing main body which is provided in an insulating oil 2 in a grounding tank 3 of a DC electric device and which is attached to an appropriate place on a wall surface of the grounding tank via a support metal fitting 4 provided in an attaching portion. A central conductor, the outer periphery of which is covered with insulating paper, is inserted inside, and further insulating oil is filled.

Reference numeral 5 denotes a terminal attached to the end of the bushing body 1, to which an insulating lead 6 is connected and which is formed in a ring shape around the connecting portion with the insulating lead 6. Shield 7 is mounting leg 7a
It is fixed by a mounting bolt 8 via.

The shield 6 is insulated by an insulating paper 9, and a cylindrical barrel 10 is attached to the outer periphery of the shield 6.
These are immersed in the insulating oil 2 in the device. Generally, this insulating paper 9 has a resistivity 10 to 300 times that of insulating oil.

In the oil-filled bushing having such a structure, when a DC voltage is applied, as shown in FIG.
Almost the potential 11 is concentrated on. When the potential is concentrated on the shield 7, the electric fields 12 and 13 of the bolt 8 and the terminal 5 inside the shield become large as shown in FIG. 6, and the dielectric breakdown is likely to occur along the path 14 shown in FIG. Further, since the electric potential is attracted to the shield 7, the electric potential distribution in the bushing axial direction is also biased to the bushing end portion.

Therefore, in the conventional DC oil-filled bushing, as described above, the cylindrical barrier 10 is provided coaxially with the shield 7 to reduce the shield insulation thickness and improve the potential distribution. In this case, the barrier 10 is tightly fixed to the shield 7.

As described above, in the conventional oil-filled bushing for direct current, the shield is provided with the barrier and the opening of the shield is closed to improve the potential distribution. Has a tendency to increase in voltage, and in particular, a larger DC voltage is applied to the bushing as well, so it is necessary to take further measures against it.

[0010]

Therefore, if the shielding of the shield is simply strengthened without improving the potential distribution in the axial direction of the bushing in preparation for the high voltage of the bushing for DC, the bushing is caused by the uneven voltage distribution in the axial direction of the bushing. Body 1
Dielectric breakdown occurs on the surface of the porcelain insulator that constitutes the.

Further, in order to increase the voltage of the DC bushing, it is necessary not only to strengthen the insulation of the shield 7 but also to improve the potential distribution in the axial direction of the bushing. Further, in order to improve the withstand voltage, increasing the distance between the tank and the effective length of the porcelain tube makes little sense. This is because even if the size of the insulating material having a large difference in resistivity is increased, the influence on the potential distribution is small.

Therefore, if an insulating material having a high resistivity is provided in a place other than the shield, especially on the outside of the porcelain tube, the electric potential is attracted to this material and concentration on the shield can be prevented.

Conventionally, the bushing body 1 has a barrier 1
Although 0 is arranged coaxially to improve the potential distribution, when the bushing body 1 becomes large due to the high voltage, the barrier 10 must be large and thick. However, since the weight of the barrier 10 increases in proportion to the thickness thereof and in proportion to the square of the radius thereof, it becomes difficult to fix the increased weight of the barrier 10 due to high voltage.

The present invention not only improves the method of fixing the barrier, but further improves the potential distribution by the fixing insulator, which not only reduces the weight but also significantly improves the DC withstand voltage. Intended to provide bushings.

[0015]

In order to solve the above-mentioned problems, the present invention comprises an oil-filled bushing for direct current by the following means. The invention corresponding to claim 1 is:
Used as a lead-out for DC oil-filled electrical equipment, a central conductor whose outer periphery is covered with insulating paper is inserted inside the porcelain tube, and an annular shield that relaxes the electric field at one end of the bushing body in which insulating oil is sealed. In an oil-filled bushing for direct current which is electrically and mechanically coupled to each other, a cylindrical first barrier is provided coaxially with the shield on the outer peripheral side of the shield, and the first barrier and the insulator tube are And closes the upper opening of the first barrier,
A disc-shaped second barrier for fixing and supporting the first barrier is provided.

According to a second aspect of the present invention, in the DC oil-filled bushing of the first aspect of the invention, a plurality of first barriers are provided coaxially with the shield, and the upper openings thereof are provided. A plurality of second barriers are provided that close and support the corresponding first barriers.

The invention corresponding to claim 3 is the oil-filled bushing for direct current according to claim 1 or claim 2, wherein a plurality of radial screw holes are provided in the second barrier, and each of these screw holes is provided. Insulating bolts are screwed in to fix the first barrier to the second barrier.

According to a fourth aspect of the invention, in the DC oil-filled bushing according to the first aspect of the invention, a plurality of fixing bolt holes are provided on the plate surface of the second barrier, and the fixing bolt is attached to the shield. It is fixed to the stud made of an insulator with a nut.

The invention corresponding to claim 5 is the oil-filled bushing for direct current according to claim 1 or 2, wherein the first barrier is made of a material having a resistivity higher than that of the insulating oil, and the second barrier is used. Is made of a material having a higher resistivity than the first barrier.

Therefore, in the DC oil-filled bushing according to the inventions corresponding to claims 1 and 2, the equipotential lines pass from the conductor inside the bushing body to the second barrier and to the first barrier. Since it escapes, the equipotential lines can be sequentially brought closer to the barrier, and the potential distribution can be further improved. In addition, the electric field on the shield surface is
Insulation breakdown from metal parts such as bolts inside the shield is prevented by the second barrier that functions as a closing lid, so damage from bolts inside the shield does not occur and bushing does not occur. The potential distribution in the axial direction of the body can also be improved.

In the oil-filled bushing for direct current of the invention according to claim 3, the first barrier is fixed to the second barrier with an insulating bolt, in addition to the same effects as the above. As compared with the case where the first barrier is tightly fixed to the shield, the deviation need not be considered.

In the oil-filled bushing for direct current of the invention according to claim 4, in addition to the same effect as the above, the second barrier is not fixed to the porcelain pipe, so that it depends on the diameter tolerance of the porcelain pipe. The position of the second barrier does not move back and forth.

In the oil-filled bushing for direct current of the invention according to claim 5, the material of the first barrier is a material having a resistivity sufficiently higher than that of the insulating oil in order to attract the equipotential lines. , The second barrier is expensive, but if a material having a higher resistivity than the first barrier is used, the equipotential lines are strongly attracted to the second barrier,
Since it flows from the second barrier to the first barrier, it is possible to further reduce the concentration of electric potential without increasing the cost significantly.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of a DC oil-filled bushing according to the present invention. The same parts as those in FIG.

In FIG. 1, reference numeral 1 denotes a bushing main body which is provided in an insulating oil 2 in a grounding tank 3 of a DC electric device, and which is attached to an appropriate place on a wall surface of the grounding tank through a support metal fitting 4 provided in an attaching portion. The bushing body 1 has a central conductor, the outer periphery of which is covered with insulating paper, inserted therein and further has insulating oil sealed therein.

Reference numeral 5 denotes a terminal attached to the end of the bushing body 1, and a terminal terminal 5a of this terminal 5 is connected to a lead terminal 6a derived from an insulating lead 6 via a lead barrier 6b. , An annular shield 7 centered on the central axis of the bushing body 1
Are fixed by mounting bolts 8 via mounting legs 7a.

The shield 7 is insulated by an insulating paper 9 and immersed in the insulating oil 2 in the equipment. Generally, this insulating paper 9 has a resistivity 10 to 300 times that of insulating oil. In the above-described configuration, in the first embodiment, the cylindrical first inner barrier 10a is tightly fixed to the outer surface of the shield 7 and also functions as a closing lid in the upper opening of the inner first barrier 10a. Disc-shaped second bar rear 14a
Is provided so as to be in contact with the first barrier 10a and the porcelain bushing 1a, and is held by the porcelain bushing 1a of the bushing body 1 to fix the inner first barrier 10a.

Further, an outer first barrier 10b is provided coaxially with the inner first barrier 10a, and a disc-shaped second barrier 14 which functions as a closing lid is provided in the upper opening thereof.
b is provided so as to be in contact with the first barrier 10b and the porcelain bushing 1a to be held by the bushing 1a of the bushing body 1, and the outer first barrier 10b is fixed.

Here, when a plurality of first barriers 10 (inner and outer two as in this example) are provided, the outer first barriers 10b need to be longer in consideration of the potential distribution. In this case, the inner first barrier 10a may be fixed near the shield 7, but the outer first barrier 10b must be fixed at a position away from the shield 7, so that the outer first barrier 10a must be fixed. It is effective to make them longer by about 10 bb and fix them by the second barriers 14a and 14b, respectively.

As the material of the barrier, it is effective to form the barrier with a material having a resistivity sufficiently higher than that of the insulating oil 2 in order to draw the equipotential lines. As a material with high resistivity, for example, pressboard is suitable,
Polymers such as Teflon and polyethylene may be used. In this case, the polymeric material is expensive, but the pressboard is inexpensive.

In the oil-filled bushing having such a structure, when a DC voltage is applied, as shown in FIG.
1 is a conductor inside the bushing body 1 and a second barrier 1
4a, 14b, the inner and outer first burria 10
Exit to a, 10b. That is, the second barriers 14a, 1
4b acts as a guide for the equipotential lines 11.

Therefore, by providing a plurality of second barriers (two in this example) 14a, 14b, the equipotential lines 11 can be brought closer to the barrier in sequence, so that the potential distribution can be further improved.

The electric field on the surface of the shield 7 is relaxed by the inner and outer first barriers 10a and 10b, and the dielectric breakdown from the metal portion such as the bolt 8 inside the shield 7 functions as a closing lid. This is prevented by the two barriers 14a and 14b.

Therefore, the bolt 8 inside the shield 7 is not broken, and the axial potential distribution of the bushing body 1 is also improved. Furthermore, the first barriers 10a, 1
0b is an inexpensive press board and is expensive as the second barriers 14a and 14b. However, if a polymer material having a higher resistivity than the press board is used, the equipotential lines will be the second barrier 14a. Since the second barrier 14 and the first barrier 10 flow toward each other, the concentration of electric potential is further alleviated without a large increase in cost.

On the other hand, the inner first barrier 10a is supported by the second barrier 14a close to the shield 7 and the outer second barrier 14a.
Barrier 10b is the second barrier 1 far from the shield
4b or these second barriers 14a, 14b, so that even a heavy barrier can be securely fixed.

FIG. 2 is a block diagram showing a second embodiment of an oil-filled bushing for direct current according to the present invention. The same parts as those in FIG. 5 are designated by the same reference numerals and their description is omitted. Will be described only.

In the second embodiment, as shown in FIG. 2, a cylindrical first barrier 10 is provided on the outer surface of the shield 7, and an annular second barrier 10 functioning as a closing lid is provided in the upper opening thereof. A barrier 14 is provided to be held by the porcelain bushing 1a of the bushing body 1, and a plurality of screw holes are provided in the second barrier 14 in the radial direction. Insulation bolts 17 are provided in these screw holes from the outer peripheral side of the first barrier 10. The first barrier 10 is fixed to the second barrier 14 by screwing.

In the oil-filled bushing having such a configuration, when a DC voltage is applied, as shown in FIG.
1 is a conductor inside the bushing body 1 and a second barrier 1
Pass through 4 to the first barrier 10. That is, the second barrier 14 acts as a guide for the equipotential line 11.

Therefore, by providing the second barrier 14, the equipotential lines 11 can be sequentially brought closer to the barrier, so that the potential distribution can be further improved. The electric field on the surface of the shield 7 is relaxed by the first barrier, and the dielectric breakdown from the metal portion such as the bolt 8 inside the shield 7 is
It is prevented by the second barrier 14 which functions as a closing lid.

Therefore, the breakage from the bolt 8 inside the shield 7 does not occur, and the potential distribution in the axial direction of the bushing body 1 is also improved. Further, in the second embodiment, the first barrier 10 is connected to the second barrier 1 by the insulating bolt 17.
Since the first barrier 10 is fixed to the shield 7, it is not necessary to consider the shift as compared with the case where the first barrier 10 is tightly fixed to the shield 7.

FIG. 4 is a block diagram showing the third embodiment of the oil-filled bushing for direct current according to the present invention. The same parts as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted. Will be described only.

In the third embodiment, as shown in FIG. 4, the outer surface of the shield 7 is tightly fixed to the cylindrical first barrier 10 and the upper opening thereof has an annular shape which functions as a closing lid. The second barrier 14 is provided, the insulator stud 15 is inserted through the bolt holes provided in the second barrier 14 and the mounting leg 7a of the shield 7, respectively, and the insulator nut 16 is fastened to the second barrier 14. 14 is fixed to the mounting leg 7a of the shield 7.

With the oil-filled bushing having such a configuration, the second barrier 14 acts as a guide for equipotential lines, and thus the same effects as those of the second embodiment can be obtained, as a matter of course. The second barrier 14 due to the diameter tolerance of the insulator 1a is not fixed to the insulator 1a.
The position of does not move back and forth.

[0044]

As described above, according to the present invention, not only the fixing method of the barrier can be improved but also the potential distribution can be improved, and not only the weight reduction but also the DC withstand voltage is remarkably improved. It is possible to provide an oil-filled bushing for direct current.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining a first embodiment of a DC oil-filled bushing according to the present invention.

FIG. 2 is a configuration diagram for explaining a second embodiment of a DC oil-filled bushing according to the present invention.

FIG. 3 is an explanatory diagram showing equipotential lines in the second embodiment.

FIG. 4 is a configuration diagram for explaining a third embodiment of a DC oil-filled bushing according to the present invention.

FIG. 5 is a configuration diagram for explaining an example of a conventional DC oil-filled bushing.

FIG. 6 is an explanatory diagram of DC electric field strength in the oil-filled bushing for DC.

FIG. 7 is an explanatory view of a discharge path in the DC oil-filled bushing.

[Explanation of symbols]

1 ... Bushing body, 1a ... Insulator pipe, 2 ... Insulating oil,
3 ... Ground tank, 4 ... Support metal fitting, 5 ... Terminal, 5a ... Terminal terminal, 6 ... Insulation lead, 6a
...... Lead bar rear, 6b ...... Lead terminal, 7 ...... Shield, 7a ...... Mounting leg, 8 ...... Mounting bolt, 9 ...... Insulating paper 10,10a, 10b ...... First barrier, 14,
14a, 14b ... Second barrier, 15 ... Insulator stud, 17 ... Insulation bolt.

Front Page Continuation (72) Inventor Makoto Tanaka 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Inventor Hiroshi Sugihara 2-5 Marunouchi, Takamatsu City, Kagawa Shikoku Electric Power Co., Ltd. (72) Inventor Yoshinori Makino 6-15-1, Ginza, Chuo-ku, Tokyo Power source development Co., Ltd. (72) Inventor Harutoshi Wada 2-1-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Toshiba Corporation Hamakawasaki Plant (72) Inventor Shigeru Mogi 2-1-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Toshiba Hamakawasaki Plant Co., Ltd. (72) In-house Yasuhiko Taniguchi 2-1-1, Ukishima-cho, Kawasaki-ku, Kawasaki, Kanagawa Toshiba Hamakawasaki Plant, Toshiba Within

Claims (5)

[Claims] 1. A center conductor used for lead-out of a DC electric oil-filled device, the outer periphery of which is covered with insulating paper is inserted into the porcelain tube, and an electric field is applied to one end of a bushing body in which insulating oil is sealed. In a DC oil-filled bushing in which a relaxing annular shield is electrically and mechanically coupled, a cylindrical first barrier is provided coaxially with the shield on the outer peripheral side of the shield. Oil for direct current, which is in contact with the porcelain bushing and which closes the upper opening of the first barrier, and which is provided with a disc-shaped second barrier for fixing and supporting the first barrier. Input bushing. 2. A plurality of second barriers which are provided coaxially with the shield, close the upper openings of the first barriers, and fix and support the corresponding first barriers. 2. The oil-filled bushing for direct current according to claim 1, further comprising a barrier. 3. The second barrier is provided with a plurality of screw holes in the radial direction, and an insulating bolt is screwed into each of these screw holes to fix the first barrier to the second barrier. The oil-filled bushing for direct current according to claim 1 or 2. 4. The plate surface of the second barrier is provided with a plurality of fixing bolt holes, and is fixed to a stud made of an insulator attached to the shield via a nut. Item 1. The oil-filled bushing for direct current according to Item 1. 5. The first barrier is made of a material having a resistivity higher than that of insulating oil, and the second barrier is made of a material having a resistivity higher than that of the first barrier. Item 3. The oil-filled bushing for direct current according to Item 2.