JP2021197262A - Vacuum switching device - Google Patents

Abstract

To provide a vacuum switching device in which dielectric breakdown or arc discharge starting from electric field relaxing members is suppressed so as to be capable of reducing damage to the electric field relaxing members.SOLUTION: A vacuum switching device comprises: an insulating container which is made of an insulating material in a cylindrical shape, and which has openings on both ends in a cylinder axial direction; a pair of electrodes which are housed in the insulating container, and whose contacts can be brought into contact with or brought out of contact from each other; sealing metal fittings which are bonded to the openings so as to close the insulating container; and a pair of electric field relaxing members which are made of a material having dielectric breakdown field strength equivalent to that of a material of the contacts, and which relax electric field strength between the insulating container and the contacts. Each of the contacts has a first curved part whose surface is curved at a predetermined radius of curvature. Each of the electric field relaxing members has a second curved part whose surface is curved at a predetermined radius of curvature. The radius of curvature of the surface of the first curved part is smaller than that of the surface of the second curved part.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to a vacuum switchgear.

For example, buildings, factories, hospitals, etc. are equipped with metal closed switchgear (hereinafter referred to simply as switchgear) to protect electric circuits in the power distribution system, control power, and monitor equipment. There is. The switchgear is configured to accommodate a main circuit conductor, a power cable, a grounding device, a current transformer, a vacuum circuit breaker, a vacuum circuit breaker, etc. in a space separated from the outside by a metal container (housing). The vacuum circuit breaker and the vacuum circuit breaker have a vacuum switchgear (also referred to as a vacuum valve) that cuts off the current by appropriately switching the electrodes arranged in the insulated container to the conductive state or the insulated state. The conductive state is a state in which the contacts of the pair of electrodes are in contact (closed poles), and the insulating state is a state in which these contacts are separated (open poles). The insulated state includes a cut-off state and a disconnecting state of a circuit formed by contacting contacts and closing the electrodes.

When the load current is cut off in the vacuum switchgear, if the contact surface is damaged by the arc discharge, the insulation performance between the contacts may deteriorate. A vacuum switchgear provided with an electric field relaxation member (electric field relaxation shield) is known in order to suppress such deterioration of insulation performance between contacts. The electric field relaxation shield is arranged so as to surround the contact of the fixed side electrode and the contact of the movable side electrode, respectively, and relaxes the potential gradient between the contact and the insulating container, in other words, the electric field strength. As an example, the electric field relaxation shield of the contact of the fixed side electrode is fixed to the side surface of the current-carrying shaft, and the electric field relaxation shield of the contact of the movable side electrode is fixed to the sealing plate of the vacuum switchgear.

Japanese Unexamined Patent Publication No. 2020-27782 Japanese Unexamined Patent Publication No. 2004-235121 Japanese Unexamined Patent Publication No. 63-160122

When the load current is cut off, if an arc is generated between the contacts and the electric field relaxation shield is damaged, the insulation performance of the electric field relaxation shield deteriorates depending on the degree of the damage. For this reason, a shield structure is also known in which a gap is provided between the contact and the electric field relaxation shield to prevent the migration of the arc. With such a shield structure, it is possible to suppress the transfer of the arc from the contact to the electric field relaxation shield.

On the other hand, if arc discharge or dielectric breakdown occurs starting from the electric field relaxation shield, damage to the electric field relaxation shield may not be sufficiently suppressed. Therefore, it is required to suppress arc discharge and dielectric breakdown starting from the electric field relaxation shield to reduce damage to the electric field relaxation shield.

The vacuum switchgear of the embodiment includes an insulating container, electrodes, sealing fittings, and an electric field relaxation member. The insulating container is formed of an insulating material in a cylindrical shape, and has openings at both ends in the cylindrical axial direction. The electrodes are housed in an insulating container and form a pair in which the contacts can be brought into contact with each other. The sealing metal fittings are joined to the openings, respectively, to close the insulating container. The electric field relaxation members form a pair and are formed of a material having a dielectric breakdown electric field strength equivalent to that of the contact material, and relax the electric field strength between the insulating container and the contact. The contacts have a first curved portion whose surface is curved with a predetermined radius of curvature. The electric field relaxation member has a second curved portion whose surface is curved with a predetermined radius of curvature. The radius of curvature of the surface of the first curved portion is smaller than the radius of curvature of the surface of the second curved portion.

The cross-sectional view in one plane including the cylinder shaft (axis core) which shows the structure of the vacuum switchgear which concerns on 1st Embodiment. The figure which shows the relationship between the effective area and the dielectric breakdown electric field strength. The figure which shows the form of the electric field relaxation shield and the contact in FIG. 1 enlarged and schematic. The figure schematically showing the mode of the electric field relaxation shield and the contact which concerns on 2nd Embodiment. The figure which shows the relationship between the surface roughness and the dielectric breakdown electric field strength. The figure schematically showing the mode of the electric field relaxation shield and the contact which concerns on 3rd Embodiment.

Hereinafter, the vacuum switchgear according to the embodiment will be described with reference to FIGS. 1 to 6. A vacuum switchgear (also called a vacuum valve) is provided for a vacuum circuit breaker of a metal closed switchgear installed for the purpose of protecting electric circuits, controlling electric current, monitoring equipment, etc. in an electric power distribution system, for example. It is used as a switch to cut off the current (load current as an example).

(First Embodiment)
FIG. 1 is a diagram schematically showing the configuration of the vacuum switchgear 1 of the first embodiment, and is a cross-sectional view taken along a plane including a tubular shaft (axis core C) described later. In the following description, the direction indicated by the arrow UP in FIG. 1 is defined as the upper direction, and the opposite direction is defined as the lower direction. These directions may be the same as the directions in which the vacuum switchgear is mounted, but may be different.

As shown in FIG. 1, the vacuum switchgear 1 includes an insulating container 2, a sealing metal fitting 3, an electrode 4, and an electric field relaxation member 5.

The insulating container 2 is formed of an insulating material in a cylindrical shape, and has openings 21 (first opening 21a and second opening 21b) at both ends in the direction of the cylinder axis (axis C). As the insulating material _{, ceramics such as alumina (Al 2} O ₃ ), glass and the like can be applied, but the insulating material is not limited thereto. The opening 21 is closed with the sealing metal fitting 3. Specifically, the first opening 21a is closed by the first sealing metal fitting 3a, and the second opening 21b is closed by the second sealing metal fitting 3b. The sealing metal fitting 3 can be formed of a metal material such as aluminum or stainless steel (SUS). However, the material is not limited to these. The sealing metal fitting 3 has, for example, a substantially disk shape, and the peripheral edge portion thereof is joined to the end portion of the insulating container 2 in the axis C direction and is arranged coaxially with the axis C.

The electric field relaxation shields 5a and 5b can be formed of a metal material such as aluminum or stainless steel (SUS). However, the material is not limited to these. The electric field relaxation shields 5a and 5b are brazed to the sealing metal fittings 3 (first sealing metal fittings 3a and second sealing metal fittings 3b) with, for example, silver, gold, copper, etc. It protrudes to the inside 22 of the. In the example shown in FIG. 1, the protruding ends of the electric field relaxation shields 5a and 5b are curved and folded so as to reduce the diameter over the entire circumference.

The electrode 4 has a current-carrying shaft 6 and a contact 7. The electrode 4 includes a pair of fixed electrodes 4a and a movable electrode 4b. The fixed electrode 4a has a first energizing shaft 6a and a first contact 7a, which will be described later, and the position does not change (displace) with respect to the insulating container 2. The movable electrode 4b has a second energizing shaft 6b and a second contact 7b, which will be described later, and is displaced (moves up and down in the present embodiment) so as to be contactable and detachable with respect to the fixed electrode 4a.

The energizing shaft 6 can be formed of a conductive material such as copper (oxygen-free copper), aluminum, chromium, or the like. However, the material is not limited to these. The energizing shaft 6 is composed of a first energizing shaft 6a and a second energizing shaft 6b arranged in a pair coaxially with the axis C of the insulating container 2.

The first energizing shaft 6a extends from the contact 7 (specifically, the first contact 7a described later) toward the first sealing metal fitting 3a, and extends from the hole portion 31a of the first sealing metal fitting 3a to the insulating container. It protrudes to the outside of 2. The hole portion 31a penetrates the central portion of the first sealing metal fitting 3a. The first energizing shaft 6a is joined to the first sealing metal fitting 3a at the hole portion 31a, and the position of the first sealing metal fitting 3a, in short, the vacuum switchgear 1 is fixed.

The second energizing shaft 6b extends from the contact 7 (specifically, the second contact 7b described later) toward the second sealing metal fitting 3b, and extends from the hole portion 31b of the second sealing metal fitting 3b to the insulating container. It protrudes to the outside of 2. The hole portion 31b penetrates the central portion of the second sealing metal fitting 3b. The second energizing shaft 6b advances and retreats in the axis C direction together with the second contact 7b described later. Therefore, a gap S is formed between the second energizing shaft 6b and the hole portion 31b to allow the displacement of the second energizing shaft 6b (advancing / retreating in the axis C direction) in the hole portion 31b. In other words, the shaft diameter of the second energizing shaft 6b is smaller than the hole diameter of the hole portion 31b. A bellows 8 that supports the second energizing shaft 6b so as to be able to advance and retreat in the axis C direction is attached to the second energizing shaft 6b.

The bellows 8 is configured in a bellows shape that can be expanded and contracted in the axis C direction, and together with the sealing metal fittings 3 (first sealing metal fittings 3a and second sealing metal fittings 3b), airtightly keeps the inside 22 of the insulating container 2 airtight. keep. The pressure inside the insulating container 2 ^{is preferably 1 × 10 -2} Pa or less. One end 8a of the bellows 8 is joined to the second sealing metal fitting 3b. The other end 8b of the bellows 8 is joined to the second energizing shaft 6b. The other end 8b of the bellows 8 may be joined to the second energizing shaft 6b via, for example, a cover member (bellows cover) that covers the other end 8b. The bellows cover suppresses the adhesion of the metal melt scattered by the arc to the bellows 8, and airtightly seals the void S.

Around the fixed electrode 4a and the movable electrode 4b, a cylindrical arc shield 9 is arranged so as to surround the electrodes 4a and 4b, and in short, the contacts 7a and 7b. The arc shield 9 prevents the metal melted by the arc from scattering when an arc is generated between the first contact 7a and the second contact 7b in the open pole state, and the metal melt is transferred to the inner peripheral surface 23. It suppresses the adhesion and deterioration of the insulating performance of the insulating container 2. The arc shield 9 can be formed of, for example, stainless steel (SUS), copper, or the like, but is not limited thereto. The arc shield 9 has a protrusion 92 protruding from the outer peripheral surface 91 toward the insulating container 2. For example, the protrusion 92 is continuous over the entire circumference of the outer peripheral surface 91 and is joined to the inner peripheral surface 23 of the insulating container 2.

The fixed electrode 4a and the movable electrode 4b each have a contact 7, and these contacts 7 are brought into contact with each other. The contact 7 is configured to include a pair of a first contact 7a and a second contact 7b. The first contact 7a corresponds to the end of the fixed electrode 4a that comes into contact with and separates from the movable electrode 4b. The second contact 7b corresponds to the end of the movable electrode 4b that comes into contact with and separates from the fixed electrode 4a.

The first contact 7a and the second contact 7b are arranged so as to face each other, and the movable electrode 4b is displaced with respect to the fixed electrode 4a to be brought into contact with each other. By the contact and separation of the contacts 7a and 7b, the connection between the fixed electrode 4a and the movable electrode 4b is changed to the conductive state and the insulated state. The conductive state is a state in which the contacts 7a and 7b are in contact (closed poles), and the insulating state is a state in which the contacts 7a and 7b are separated (open poles). The insulating state includes a disconnecting state of a circuit formed by contacting the contacts 7a and 7b and closing the electrodes 4a and 4b.

The first contact 7a and the second contact 7b are made of a conductive alloy, for example, copper chromium (CuCr). The composition of copper-chromium is not particularly limited, but as an example, copper (Cu) is about 75% to 65%, chromium (Cr) is about 25% to 35%, preferably copper (Cu) is about 75%, and chromium (Cr). ) Is about 25%. However, the materials of the first contact 7a and the second contact 7b are not limited to this, and alloys such as AgW and CuCrTe can be used.

The electric field relaxation member (hereinafter referred to as an electric field relaxation shield) 5 is arranged in the vicinity of the contact 7, and relaxes the potential gradient between the contact 7 and the insulating container 2, in other words, the electric field strength. The electric field relaxation shield 5 includes a pair of a first electric field relaxation shield 5a and a second electric field relaxation shield 5b. These electric field relaxation shields 5a and 5b are arranged one by one corresponding to each of the pair of electrodes 4a and 4b. The first electric field relaxation shield 5a is arranged in the vicinity of the first contact 7a. The second electric field relaxation shield 5b is arranged in the vicinity of the second contact 7b.

In the contact / separation direction (axis C direction) of the contacts 7a and 7b, one electric field relaxation shield 5 is arranged farther from the other contact 7 than the corresponding one contact 7. That is, the first electric field relaxation shield 5a is arranged farther from the second contact 7b than the first contact 7a. The second electric field relaxation shield 5b is arranged farther from the first contact 7a than the second contact 7b. In other words, the first contact 7a is located closer to the second contact 7b than the first field relaxation shield 5a, and the second contact 7b is the first contact than the second field relaxation shield 5b. It is located closer to 7a. As a result, in the contact / separation direction (axis C direction) of the contacts 7a and 7b, the facing distance between the contacts 7a and 7b becomes narrower than the facing distance between the electric field relaxation shields 5a and 5b. The first contact 7a protrudes from the first electric field relaxation shield 5a in the contact direction with the second contact 7b. The second contact 7b protrudes from the second electric field relaxation shield 5b in the contact direction with the first contact 7a. Therefore, when the contacts 7a and 7b are connected and separated, the electric field relaxation shields 5a and 5b do not interfere with each other and do not interfere with the contact and separation of the contacts 7a and 7b.

The electric field relaxation shield 5 (first electric field relaxation shield 5a and second electric field relaxation shield 5b) is a material having the same dielectric breakdown electric field strength as the material of the contact 7 (first contact 7a and second contact 7b). Is formed of. The dielectric breakdown electric field strength (Eb) is defined by the effective area (Seff). FIG. 2 shows the relationship between the effective area and the dielectric breakdown electric field strength. The effective area is the area of a region having an electric field strength of 90% or more of the maximum electric field strength in the total surface region of the target system, for example, all the target members. The dielectric breakdown electric field strength is calculated as a value obtained by multiplying the value obtained by multiplying the effective area by k by α (Eb = α × Seff ^ k). k and α are coefficients determined by the material, and the value of k is about −0.2 to −0.3.

The relationship between the effective area and the dielectric breakdown electric field strength varies depending on the material (constituent material) of the target system, but in general, as shown in FIG. 2, the larger the effective area, the lower the dielectric breakdown electric field strength. Become. Therefore, in order to increase the dielectric breakdown electric field strength, it is preferable to reduce the effective area. As described above, the contact 7 is made of a material having excellent insulation performance and current cutoff performance, such as copper chrome. On the other hand, the electric field relaxation shield 5 is made of a material having a dielectric breakdown electric field strength equivalent to that of copper chromium, for example, stainless steel (SUS). The material of the electric field relaxation shield 5 is not limited to this. For example, when an alloy such as AgW or CuCrTe is used as the contact material, any material having the same dielectric breakdown electric field strength as these is used as the shield material. It may be used as.

Here, for example, in the case of a vacuum disconnector, it is necessary to cut off the load current, but since it is not required to cut off the problem current to the extent that the vacuum circuit breaker needs to be cut off, the contact 7 is compared with the vacuum circuit breaker. The surface area of the circuit breaker may be small. Therefore, it is possible to reduce the size of the contact 7 in order to reduce the size and cost of the vacuum switchgear 1 according to the present embodiment. However, the smaller the contact 7, the higher the electric field strength acting on the contact 7, and the lower the withstand voltage performance is likely to occur. Therefore, in the present embodiment, the electric field relaxation shield 5 is arranged in the vicinity of the contact 7 so as to cover the periphery of the first energization shaft 6a and the second energization shaft 6b, respectively, and the electric field strength in the vicinity of the contact 7 is relaxed. However, we are trying to increase the withstand voltage.

On the other hand, if the electric field strength in the vicinity of the contact 7 is relaxed by arranging the electric field relaxation shield 5, the electric field strength in the vicinity of the electric field relaxation shield 5 may be equal to or higher than the relaxed electric field strength. In this case, there is a possibility that dielectric breakdown may occur starting from the electric field relaxation shield 5 when the voltage is increased, or arc discharge may occur when the load current is cut off. If the electric field relaxation shield 5 is damaged by these, the damaged portion becomes a fragile portion in terms of insulation, and the insulation performance of the vacuum disconnector may deteriorate.

Therefore, in the present embodiment, the electric field relaxation shield 5 and the contact 7 are set as appropriate forms, and the electric field balance between them is controlled to suppress the occurrence of dielectric breakdown and arc discharge in the electric field relaxation shield 5. Next, the form of the electric field relaxation shield 5 and the contact 7 will be described.

FIG. 3 schematically shows the form of the electric field relaxation shield 5 and the contact 7 in FIG. 1 in an enlarged manner.
As shown in FIG. 3, the contact 7 (first contact 7a and second contact 7b) is a flat plate-shaped member having a circular shape substantially concentric with the axis C. The first surface 71 of the contact 7 is in contact with and separated from the facing contact 7 (in the case of the first contact 7a, it is the second contact 7b, and in the case of the second contact 7b, the first contact 7a). It is a face. The second surface 72 of the contact 7 is a fixed surface with respect to the energizing shaft 6 and the electric field relaxation shield 5. The contact 7 is fixed to the second surface 72, for example, by brazing the second surface 72 to the current-carrying shaft 6 and the electric field relaxation shield 5 with silver, gold, copper, or the like.

The contact 7 has a flat portion 73 and a curved portion (hereinafter referred to as a first curved portion) 74. The flat portion 73 is a flat portion that comes into contact with and separates from the facing contact 7. The first curved portion 74 is a peripheral portion of the contact point 7, and is continuous with the peripheral edge of the flat portion 73 over the entire circumference. The surface 75 of the first curved portion 74 is a series of continuous surfaces without uneven portions such as protrusions, dents and grooves.

The electric field relaxation shield 5 (the first electric field relaxation shield 5a and the second electric field relaxation shield 5b) is flat and has a diameter larger than the thickness and is substantially concentric with the axis C. The thickness of the electric field relaxation shield 5 is the maximum length in the axis C direction (vertical direction in FIG. 3). It is the diameter of the electric field relaxation shield 5 and the maximum length in the direction orthogonal to the axis C direction (left-right direction in FIG. 3). The outer peripheral surface 51 of the electric field relaxation shield 5 is a surface facing the inner peripheral surface 23 of the insulating container 2. The inner peripheral surface 52 of the electric field relaxation shield 5 is a fixed surface with respect to the current-carrying shaft 6. The electric field relaxation shield 5 is fixed to the current-carrying shaft 6 by, for example, brazing the inner peripheral surface 52 to the outer peripheral surface of the current-carrying shaft 6 with silver, gold, copper or the like.

The electric field relaxation shield 5 has a base portion 53 and a curved portion (hereinafter referred to as a second curved portion) 54. The base portion 53 is a cylindrical portion supported by the current-carrying shaft 6, and the cylinder ends (upper and lower ends in FIG. 3) on both sides are flat surfaces. The second curved portion 54 is a peripheral portion of the electric field relaxation shield 5, and is continuous with the peripheral edge of the base 53 over the entire circumference. The surface 55 of the second curved portion 54 is a series of continuous surfaces without uneven portions such as protrusions, dents and grooves. The surface 55 corresponds to the outer peripheral surface 51 of the electric field relaxation shield 5.

At the contact point 7, the surface 75 of the first curved portion 74 is a curved surface that curves with a predetermined radius of curvature. Further, in the electric field relaxation shield 5, the surface 55 of the second curved portion 54 is a curved surface curved with a predetermined radius of curvature. The radius of curvature of the surface 75 of the first curved portion 74 is smaller than the radius of curvature of the surface 55 of the second curved portion 54.

In the present embodiment, the electric field relaxation shield 5 and the contact 7 are each made of a material having the same dielectric breakdown electric field strength. In a system composed of an electric field relaxation shield 5 and a contact 7 on the fixed electrode 4a side and the movable electrode 4b side (hereinafter referred to as a target system), the radius of curvature of the surface 75 of the first curved portion 74 is set to the second curved portion. By making it smaller than the radius of curvature of the surface 55 of the 54, the electric field strength acting on the electric field relaxation shield 5 is reduced to be smaller than the electric field strength acting on the contact 7.

Therefore, in such a target system, the effective area of the second curved portion 54 can be made smaller than the effective area of the first curved portion 74. In other words, the effective area in the target system can be concentrated by the first curved portion 74 of the contact 7. As a result, the dielectric breakdown electric field strength of the electric field relaxation shield 5 in the target system can be increased with respect to the contact 7. Therefore, even if an arc discharge occurs when the current is cut off, the location where the arc discharge occurs can be kept between the contacts 7a and 7b, and the arc discharge between the electric field relaxation shields 5a and 5b can be suppressed. As a result, damage to the electric field relaxation shield 5 can be reduced, and dielectric breakdown of the electric field relaxation shield 5 can be suppressed. As a result, deterioration of the insulation performance of the vacuum switchgear 1 can be suppressed.

The degree of reduction of the radius of curvature of the surface 75 of the first curved portion 74 with respect to the radius of curvature of the surface 55 of the second curved portion 54 is not particularly limited. For example, when the contacts 7a and 7b are separated (opened) and the load current is cut off, the maximum electric field strength acting on the second curved portion 54 of the electric field relaxation shield 5 is the first curved portion of the contact 7. The radius of curvature of the surface 75 may be smaller than that of the surface 55 so as to be smaller than the maximum electric field strength acting on the 74. Specifically, the maximum electric field strength acting on the second curved portion 54 of the electric field relaxation shield 5 may be about 90% or less of the maximum electric field strength acting on the first curved portion 74 of the contact 7. As an example, when the radius of curvature of the surface 75 of the first curved portion 74 is about 5 mm, the radius of curvature of the surface 55 of the second curved portion 54 may be about 20 mm.

The electric field relaxation shield 5 according to the present embodiment has a base portion 53 and a second curved portion 54, but the base portion 53 may be omitted. In this case, the electric field relaxation shield is configured to have an annular curved portion having a through hole concentric with the axis C in the central portion as a portion corresponding to the second curved portion 54.

As described above, in the present embodiment, in the first curved portion 74 and the second curved portion 54, the radius of curvature of the surface 75 is made smaller than that of the surface 55, but in addition to this, these curved portions 74, 54 are used. The arc discharge between the electric field relaxation shields 5a and 5b may be suppressed by adopting the following form. Hereinafter, such an embodiment will be described as a second embodiment and a third embodiment. The basic configuration of the vacuum switchgear in these embodiments is the same as that of the vacuum switchgear 1 (FIG. 1) according to the first embodiment. Therefore, in the following, the description of the basic configuration of the vacuum switchgear will be omitted, and the electric field relaxation shield and the contacts which are the features of the second embodiment and the third embodiment will be described in detail. At that time, the same reference numerals are used for the same or similar components as those in the first embodiment.

(Second embodiment)
FIG. 4 schematically shows a mode of the electric field relaxation shield 5 and the contact 7 according to the second embodiment. For example, the size of the electric field relaxation shield 5 depends on the size of the space inside 22 of the insulating container 2. If the vacuum switchgear 1 is miniaturized and sufficient space cannot be secured inside the insulating container 2, the size of the electric field relaxation shield 5 is limited accordingly. In this case, the electric field relaxation shield 5 and the contact 7 have appropriate surface roughness, and the electric field balance between them can be controlled. For example, in the Waller-Nordheim theory, the insulation performance in vacuum is also defined by the surface roughness of the target system, for example, the target member. According to this theory, assuming a micro-projection with high electric field inequality, the electric field is locally emphasized and the field electron emission becomes remarkable, and this field electron emission triggers dielectric breakdown. .. FIG. 5 shows the relationship between the surface roughness and the dielectric breakdown electric field strength. As shown in FIG. 5, the finer the surface roughness (for example, the smaller the scale of the surface roughness), the higher the dielectric breakdown electric field strength. Therefore, in order to increase the dielectric breakdown electric field strength, it is preferable to make the surface roughness finer.

Therefore, in the electric field relaxation shield 5 according to the present embodiment, the surface roughness of the surface 55a of the second curved portion 54 is finer than that of the surface 75a of the first curved portion 74. In other words, the surface 55a is a smoother surface than the surface 75a, and the surface 75a is a rougher surface than the surface 55a. The method for making the surface roughness of the surface 75a smaller than that of the surface 55a, that is, the method for making the surface 55a a smoother surface than the surface 75a is not particularly limited. For example, the second curved portion 54 of the electric field relaxation shield 5 may be subjected to surface treatment such as electrolytic polishing or chemical polishing to make the surface roughness of the surface 55a finer than the surface roughness of the surface 75a. At that time, it does not matter whether or not the first curved portion 74 of the contact 7 is subjected to surface treatment such as electrolytic polishing or chemical polishing. That is, the surface roughness of the surface 55a of the second curved portion 54 of the electric field relaxation shield 5 may be smaller than that of the surface 75a of the first curved portion 74. When the surface 75a is not surface-treated, its surface roughness is the same as the surface roughness of the surface 75 of the first curved portion 74 according to the first embodiment.

By making the surface roughness of the surface 75a finer than that of the surface 55a in this way, the dielectric breakdown electric field strength of the electric field relaxation shield 5 is applied to the contact 7 in the target system on the fixed electrode 4a side and the target system on the movable electrode 4b side. Can be enhanced. Therefore, it is possible to suppress the arc discharge between the electric field relaxation shields 5a and 5b and suppress these dielectric breakdowns.

As the scale of the surface roughness, for example, an arithmetic average roughness (Ra), a maximum height (Ry), a ten-point average roughness (Rz), or the like can be used. The surface roughness may be determined by any of the above scales in a portion randomly selected from the surfaces 75a and 55a of the first curved portion 74 and the second curved portion 54.

(Third embodiment)
FIG. 6 schematically shows a mode of the electric field relaxation shield 5 and the contact 7 according to the third embodiment.
As shown in FIG. 6, in the electric field relaxation shield 5 according to the present embodiment, the surface 55 of the second curved portion 54 has an insulating property and a current breaking property with the material of the first curved portion 74, in short, the contact 7. Are each coated with the same high pressure resistant material. That is, a predetermined coating 56 is formed on the surface 55.

The coating 56 may be formed of the following materials depending on the material of the contact 7 including the first curved portion 74. For example, when the material of the contact 7 is copper (Cu) of 75% and chromium (Cr) of 25%, the material of the coating 56 is copper (Cu) of 75% to 65% and chromium. Copper chromium having (Cr) of about 25% to 35%, or a high pressure resistant material having the same level as this may be used. The method for forming the coating film 56 is not particularly limited. For example, the film 56 may be formed on the surface 55 by an ion plating method, a physical vapor deposition method (PVD), a chemical vapor deposition method (CVD), or the like.

By forming the high withstand voltage coating 56 on the surface 55 in this way, when an arc discharge occurs between the electric field relaxation shields 5a and 5b in the target system on the fixed electrode 4a side and the target system on the movable electrode 4b side. Even if there is, these damages can be reduced and dielectric breakdown can be suppressed. For example, when the electric field relaxation shield 5 has a larger size than the contact 7, it is not preferable to replace the entire electric field relaxation shield 5 with another high pressure resistant material because it causes an increase in cost. Even in such a case, in the present embodiment, the film 56 having excellent insulating property and current blocking property is formed on the surface 55 of the second curved portion 54 without changing the material of the electric field relaxation shield 5. As a result, the pressure resistance of the second curved portion 54 can be increased. Therefore, the insulating property and the current breaking property of the electric field relaxation shield 5 can be improved at a relatively low cost.

The film thickness of the coating 56 is preferably a thickness considering that it is slightly worn when the current is cut off. For example, the number of cutoffs starting from the electric field relaxation shield 5 is determined in advance based on the opening / closing life of the vacuum switchgear 1 and based on the relative relationship between the effective area of the contact 7 and the effective area of the electric field relaxation shield 5. Assuming that, by setting the film thickness of the coating film 56 according to the number of cutoffs, the coating film 56 can be formed at a lower cost.

Further, in the electric field relaxation shield 5 according to the present embodiment, the coating film 56 is formed not only on the surface 55 of the second curved portion 54 but also on the surface of the base portion 53. That is, the coating 56 is formed over the entire region where the electric field relaxation shield 5 is exposed to the outside. However, the coating 56 does not have to be formed over the entire surface of such a region, and may be formed at least over the entire surface 55 of the second curved portion 54.

Although some embodiments of the present invention have been described above, the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... Vacuum opening / closing device, 2 ... Insulated container, 3 ... Sealing metal fittings, 4 ... Electrodes, 5,5a, 5b ... Electric field relaxation member (electric field relaxation shield), 6 ... Energizing shaft, 7,7a, 7b ... Contact, 8 ... Bellows, 9 ... Arc Shield, 21 ... Opening, 53 ... Base, 54 ... Second Curved Part, 55, 55a ... Surface of Second Curved Part, 56 ... Coating, 73 ... Flat Part, 74 ... First Curved portion, 75, 75a ... Surface of the first curved portion, C ... Axial core, S ... Void.

Claims (7)

An insulating container that is made of an insulating material and has openings at both ends in the axial direction of the cylinder.
A pair of electrodes housed in the insulating container and capable of contacting and separating from each other,
A sealing metal fitting that is joined to each of the openings and closes the insulating container, and
It is provided with a pair of electric field relaxation members which are formed of a material having the same dielectric breakdown electric field strength as the material of the contact and relax the electric field strength between the insulating container and the contact.
The contact has a first curved portion whose surface is curved with a predetermined radius of curvature.
The electric field relaxation member has a second curved portion whose surface is curved with a predetermined radius of curvature.
A vacuum switchgear in which the radius of curvature of the surface of the first curved portion is smaller than the radius of curvature of the surface of the second curved portion. The pair of electric field relaxation members are arranged one by one corresponding to each of the pair of electrodes.
The vacuum switchgear according to claim 1, wherein the electric field relaxation member is arranged at a distance from the contact other than the corresponding contact in the contact / separation direction of the pair of contacts. The vacuum switchgear according to claim 2, wherein the surface of the second curved portion is a series of continuous surfaces without protrusions and dents. The vacuum switchgear according to claim 3, wherein the electric field relaxation member is flattened in the tubular axis direction in a direction orthogonal to the tubular axis direction rather than a maximum length in the tubular axis direction. The vacuum switchgear according to any one of claims 1 to 4, wherein the surface of the second curved portion has a finer surface roughness than the surface of the first curved portion. The vacuum switchgear according to any one of claims 1 to 4, wherein the surface of the second curved portion is coated with a material having the same insulating property and current blocking property as the material of the first curved portion. .. A claim that the maximum electric field strength acting on the second curved portion is 90% or less of the maximum electric field strength acting on the first curved portion in a state where the pair of the contacts are separated and the load current is cut off. Item 6. The vacuum switchgear according to any one of Items 1 to 6.

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