CN1027024C - Gas Insulated Electrical Equipment - Google Patents

Abstract

A gas-insulated electrical device comprising: a metal tube in which an insulating gas is sealed; a conductor supported by an insulating support member in the metal tube; and an insulating layer on the inner wall of the metal tube mixed with a strong insulating substance so that Its dielectric constant is equal to or greater than 10.

Description

The present invention relates to gas-insulated electrical equipment, and more particularly, to a gas-insulated electrical equipment capable of preventing a decrease in dielectric strength within the equipment even under the condition that conductive particles are mixed into the equipment.

In many cases, gas-insulated electrical equipment is used as a device in which a high-voltage object serving as a power supply conductor is assembled in a metal tube sealed with an electronegative gas, such as SF ₆ gas, when conductive particles are mixed into these equipment and fall and adhere In the case of the bottom of the tube, the conductive particles rise from the inner wall of the tube under the action of the electric field inside the tube and float in the gas space. Due to these floating conductive particles, the insulation strength of the gas space is greatly reduced. In order to ensure the insulation reliability of the equipment, a device configuration that can avoid the influence of such conductive particles is required.

In order to solve this problem, as shown in Japanese Patent Application No. 136811/80, there is a device with such a configuration that the inner wall of the tube is provided with a high dielectric constant insulating layer, due to the voltage supplied to the device, Generates a strong electrostatic attraction capable of overcoming the electrostatic buoyancy force acting on the conductive particles between the conductive particles and the bottom of the tube, thereby inhibiting the floating movement of the conductive particles. In this case, it is necessary to make An insulating layer is formed using a highly insulating substance having a dielectric constant larger than a predetermined value. Usually, the dielectric constant of an organic polymer compound is not greater than 6. Although the dielectric constant of inorganic compounds such as sintered barium titanate can reach several thousand, materials such as sintered barium titanate are fragile and cannot be processed. Furthermore, it is also difficult to fix sintered barium titanate to a tube having an annular inner wall.

On the other hand, it is necessary to increase the electrostatic attraction for attracting conductive particles on the insulating layer in order to further improve the insulating performance of the device.

It is an object of the present invention to increase the attractive force for conductive particles on an insulating layer and to provide a gas insulated electrical apparatus in which an insulating layer is firmly attached to the inner wall of a pipe semi-permanently.

According to the present invention, there is provided a gas-insulated electrical apparatus comprising a metal tube hermetically sealed against an insulating gas, a conductor supported by an insulating support member inside said metal tube, and an insulating layer on an inner surface of said metal tube. This insulating layer is a coating formed from a mixed liquid obtained by mixing strong insulating material powder of an inorganic material and an organic material, wherein a fine powder having a high dielectric constant is dissolved in a binder as a filling substance. The dielectric constant of this coating can be adjusted according to the mixing ratio of the filling substances and their dielectric constants. Experiments have confirmed that when the coating is formed, its dielectric constant becomes equal to or greater than 10, and the floating motion of conductive particles attached to the coating can be suppressed. In this way, the present invention is formed by coating with a mixed liquid as a means of semi-permanently and firmly placing a thin-film insulating layer of a high-permittivity system on the inner wall of the device.

In addition, according to the present invention, in order to increase the electrostatic attraction of the insulating layer, a Conductive treatment on the side.

The present invention is described in detail as follows in conjunction with accompanying drawing:

Fig. 1 is a vertical sectional view of a gas insulated electrical apparatus with an insulating layer according to a first embodiment of the present invention.

Fig. 2 is a sectional view along line II-II of the embodiment in Fig. 1 .

Fig. 3 is a graph showing the relationship between the mixing ratio of the binding liquid and the filling substance and the dielectric constant.

Fig. 4 is a graph showing the relationship between the electric field of an insulating layer attracting a conductive particle and the DC electric field when the insulating layer is polarized.

5A and 5B are schematic diagrams of a second embodiment of the present invention.

Fig. 6 is a partial sectional view of a second embodiment of the present invention.

Fig. 7 represents the second embodiment of the present invention, the curve that the power that conductive particle is attracted to insulating layer has increased; And

Figures 8, 9 and 10 all show improved structural diagrams of the first and second embodiments of the present invention.

Referring to Figures 1 and 2, gas-insulated electrical equipment is constructed in such a way that a high-voltage conductor 3 is insulated and supported by an insulating support member 2, and the high-voltage conductor 3 is placed in a grounded metal pipe or a grounded metal pipe sealed with an insulating gas inside. In the container 1, the insulating layer 4 of the high-voltage insulation system formed on the inner wall of the pipe 1 is formed by a coating, which is formed by applying a mixed liquid in which strong insulating Fine powder of material.

The electrostatic attraction, which can overcome the electrostatic buoyancy, acts on the conductive particles 5 and 6 through the generated electric field (the particles fall and attach to the insulating layer 4 between the bottom of the tube and the conductive particles). so as to hinder the floating transport of conductive particles 5 and 6 mixed into the equipment move.

In order to obtain enough electrostatic attraction to effectively hinder the floating movement of conductive particles, it is necessary to make the dielectric constant of the insulating layer greater than 10, however, this dielectric constant is determined by the dielectric constant of the bonding liquid and the filling material, or even their determined by the mixing ratio.

Figure 3 shows that when ordinary unwatered coating solution (solvent 40% raw material 60%) is used as the bonding liquid and barium titanate ceramic fine powder is used as the filling material, the mixing ratio of the above materials and the coating formed by the above mixed liquid The relationship between the dielectric constant of the layer. The dielectric constant ε _r of the coating can be increased by increasing the mixing amount ω of the filling material. In the case of ω ≥ 20 (volume percent), ε _r ≥ 10 can be obtained. On the one hand, the relationship between the mixing ratio and the dielectric constant as shown in Figure 3 mainly changes with the dielectric constant of the filling material, and at the same time, the use of a filling material with a high dielectric constant can also effectively increase ε _r .

In addition, as a bonding liquid, a liquid having a strong coagulation strength is expected, and this may produce the effect that the bonding property of the coating applied to the inner wall of the pipe can be strong, Moreover, the insulating layer 4 can be firmly fixed semi-permanently.

In order to protect the metal surface, using anti-corrosion paint or the like as the adhesive liquid can produce such an effect that the insulating layer also has a metal surface protection function, such as anti-corrosion and other functions.

On the one hand, the substance that can be used as the adhesive liquid can be phenolic resin, urea resin, melamine resin, alkyd resin, polyester resin, epoxy resin, vinyl resin, polystyrene, acrylic resin, polyamide resin, Fluorine resin, ester resin, etc. In addition, paints and varnishes of any of the above-mentioned substances may also be used as the main raw material.

Although the use of barium titanate ceramics as the filling material has been described above, it can also be used as lithium tantalate, sodium niobate or lithium niobate as a strong insulating material, or lead titanate fine powder, etc., or their solid solutions. If barium titanate is used, when the filler material exceeds 20%, the volume ratio of the binder liquid and the filler substance mixture that makes the dielectric constant _εr equal to or greater than 10 can be obtained. In the case of other substances, the results are as follows: when the dielectric constant ε _r becomes greater than 10, the volume ratio is as follows, the volume ratio of lead titanate is greater than 25%, lithium tantalate is greater than 10%, niobate Lithium is greater than 10%, and sodium niobate is greater than 20%.

On the other hand, a DC electric field is provided to the insulating layer 4 to carry out polarization treatment, so that the dielectric constant of the insulating layer 4 can be further improved, so that the electrostatic attraction can be further increased. Fig. 4 is an example, showing the The gravitational electric field strength of conductive particles (when the conductive particles move out from the surface of the insulating layer, the relationship between the electric field strength (EL ₀ ) inside the tube and the direct current electric field strength E _DC used for polarization treatment.

The hatched rectangle in the left half of Fig. 4 represents the electric field strength E _L0 of the insulating layer without polarization treatment, and the electric field strength is about 0.85-1.05 kv/mm. The hatched rectangle in the middle part of Fig. 4 represents the electric field strength E _L0 of the insulating layer 4 under the polarization treatment with the electric field strength E _DC =2kv/mm, which is about 0.85-1.25kv/mm. The hatched rectangle in the right half of Fig. 4 indicates the electric field strength E _L0 of the insulating layer 4 under the polarization treatment of E _DC =3.5 kv/mm, which is about 1.4-1.6 kv/mm. In some cases, when the polarization treatment is performed due to E _DC =2 (kv)/(mm), the intensity of the gravitational electric field is almost so low that polarization cannot be performed (E _DC =0 (kv)/(mm) ). On the contrary, in another case, since E _DC =3.5 (kv)/(mm), when the polarization treatment is performed, the value of E _L0 is greatly improved compared with the above two cases. In the figure, as shown by the line connecting dots and long dashes, it is possible to obtain more satisfactory results than bare electrodes (the metal without insulating layer is exposed). From this result, it can be known that when the polarization treatment When E _DC >2 (kv)/(mm) is satisfied, the effect of insulating layer formation can be utilized as effectively as possible.

As a method of polarization treatment, after the insulating layer 4 is formed in the tube 1, a DC voltage is applied between the tube 1 and the conductor 3, where an electric field greater than (2kv)/(mm) is generated.

According to the first embodiment of the present invention, there is such an effect that the attractive force of the particles and the insulating layer is increased; and the insulating layer can be easily formed on the inner wall of the pipe by spraying the adhesive liquid mixed with a filler etc. . In this way, its formation can be greatly simplified; and the adhesion to the inner wall of the pipe can be enhanced.

Next, a second embodiment of the present invention will be explained with reference to FIGS. 5A, 5B, 6, and 7. FIG.

First, referring to FIG. 5A, the insulating layer 4 is an insulating plate or is formed by mixing the above-mentioned strong insulating material with the above-mentioned resin or with a film material such as polyethylene. If the insulating plate 4 is placed on the inner wall of the pipe, due to the limitation of the working accuracy and the roughness of the inner wall of the pipe 1, a gap g will be generated between the inner wall of the pipe 1 and the insulating plate. If a particle 5 with a charge of −Q ₁ falls onto the insulating plate, then an equivalent charge +Q ₂ of opposite polarity is induced in the insulating plate 4 on the particle side. Conversely, a charge -Q ₃ (Q ₃ =Q ₂ ) is also induced on the surface on the other side, as shown. Furthermore, a charge +Q ₄ of opposite polarity to -Q ₃ is induced on the inner wall of the tube 1 with the gap g. In this case, the attractive force F ₁₂ on the particle 5 is determined by the charged particle of charge -Q ₁ and the charge +Q ₂ induced on the insulating plate and their distance. However, the thickness t of the insulating plate 4 is very thin, and the repulsive force generated on the opposite side of the insulating plate due to the charge- _Q of the same polarity as the charged particle cannot be ignored; so that the attractive force cannot be fully utilized. On the other hand, as shown in Fig. 5B, if the back of the insulating layer is tightly attached to the inner tube of tube 1, -Q ₃ and +Q ₄ neutralize each other, so that the repulsive force generated by -Q ₃ is negligible, and -Q The gravitational force F ₁₂ between ₁ and +Q ₂ can be fully exploited. Thereby, it is possible to overcome the floating of particles.

Since the charges -Q ₃ and +Q ₄ cancel each other out, as shown in Figure 6, the surface of the conductive substance is brought into contact with the inner wall of the tube 1 by means of spraying or the like, and bonded to the back of the insulating plate 4, thereby forming the electrode 7 .

FIG. 7 shows the effect obtained by forming the electrodes 7 on the insulating plate 4. As shown in FIG. The vertical axis represents the relative value of the gravitational electric field to the particle attraction, and 1 represents the situation that there is no insulating plate. A on the horizontal axis represents an insulating plate on which no electrode 7 is formed. In the case of A, the gravitational electric field is slightly improved compared with the conventional case where no insulating plate exists; however, no significant effect is obtained. On the one hand, B represents the case of the insulating plate on which the electrode 7 has been formed, and we found that the gravitational electric field at this time is about 3 times stronger than the conventional case. That is, according to the second embodiment of the invention, the gravitational electric field of particles can be greatly improved, so that even when a particle is mixed into a gas-insulated electric device, floating of the particle when voltage is applied to the device is avoided, thereby improving insulation reliability.

As far as the insulating plate configuration is concerned, it is not necessary to provide it on the entire inner wall of the grounded container. As shown in Fig. 9, even if the insulating plate is placed only at the bottom of the container, a sufficient effect can be obtained in consideration of the action of the particles. In addition, it is not necessary to provide the insulating plate along the length direction of the entire container, and the insulating plate may be provided locally as shown in FIG. 8 .

On the other hand, as shown in Fig. 10, the insulating plate can also be placed only near the insulating support member, such as the support 8 or the object easily affected by particles. In FIG. 10 , reference numerals 9 , 10 denote metal parts for supporting and fixing the support 8 . In this case, the structure of the insulating layer 4 of the present invention is formed by attaching the insulating plate 4 to the metal support member 9, thereby producing an effect similar to that shown in FIG. 5 . In addition, there is no need to fix the insulating plate on the bottom surface of the grounding container, and it only needs to be integrally assembled with the insulating support inside, so this configuration method is superior in terms of production.

Claims (6)

1, electric gas-isolated device comprises:

The metal tube of a sealed insulation gas,

A conductor that in above-mentioned metal tube, supports by insulating support member;

It is characterized in that one above-mentioned metal pipe internal surface by the strong insulating material powder of inorganic material and organic material mix obtain thereby its dielectric coefficient more than or equal to 10 insulating barrier.

2, electric gas-isolated device according to claim 1,

It is characterized in that: be applied to the above-mentioned insulating barrier that forms in the above-mentioned metal tube by the strong insulating material powder of inorganic material and the mixing material of organic material.

3, electric gas-isolated device according to claim 1,

It is characterized in that: above-mentioned insulating barrier is a plate or sheet;

And described electric gas-isolated device comprises that also one forms electrode on above-mentioned insulating barrier and above-mentioned metal pipe internal surface facing surfaces, thereby above-mentioned electrode is offset the electric charge of responding on above-mentioned insulating barrier, the polarity that each electric charge had with float to metal tube on the conducting particles charge polarity identical.

4, according to the described gas electric insulation of claim 2 electric equipment, it is characterized in that: above-mentioned insulating barrier is by close support component setting.

5, according to the described gas insulated electric apparatus of claim 2, it is characterized in that: insulating barrier is polarized under the electric field strength more than or equal to 2KV/mm.

6, gas insulated electric apparatus according to claim 2 is characterized in that: strong insulating material is a barium titanate.

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