JP2020149780A - Vacuum circuit breaker - Google Patents

Abstract

To improve the insulation performance at a contact point.SOLUTION: A vacuum circuit breaker (10) is provided inside a vacuum vessel (11) so as to be detachable and be energized in a contact state, and includes a movable contact (12) and a fixed contact (14) that cut off in a separated state. The movable contact and the fixed contact respectively have electrode portions (30, 40) that generate a longitudinal magnetic field with contact portions (32, 42) formed with facing surfaces (33, 43) facing each other. The facing surface is provided with a contact region (47) in contact with the other facing surface and a recess (48) in which a distance from the other facing surface is larger than the contact region. The bottom (48a) of the recess is formed to have a smaller maximum surface roughness (Rmax) than the contact region.SELECTED DRAWING: Figure 2

Description

The present invention relates to a vacuum circuit breaker that cuts off an electric current by separating contacts in a vacuum space.

Conventionally, a vacuum circuit breaker has been used in which a pair of electrodes that can be brought into contact with each other are provided in a vacuum vessel and an arc generated between the electrodes is extinguished in a vacuum when a current is cut off (see Patent Document 1). The vacuum circuit breaker is required to improve the breaking performance so that the high voltage and large current in the substation equipment and the power receiving and distributing equipment can be cut off. In addition, there is a need for a vacuum circuit breaker as a clean device that can be operated without using an insulating gas having a large global warming potential.

Japanese Unexamined Patent Publication No. 2003-92050

Dielectric breakdown (generation of arc) between electrodes when the current of a vacuum circuit breaker is cut off can be explained based on the Paschen curve. FIG. 12 is a graph of Paschen curve. In the Paschen curve graph of FIG. 12, the horizontal axis is atmospheric pressure × gap length, and the vertical axis is insulation breakdown voltage (insulation strength). In the Paschen curve, it is known that the breakdown voltage rises sharply when the gap length × pressure on the horizontal axis at which the minimum value Vmin of the breakdown voltage is obtained is further reduced.

Under vacuum pressure handled by a vacuum circuit breaker (for example, about 10 ^-4 Pa or less), dielectric breakdown occurs under the condition that the dielectric breakdown voltage is smaller than the value on the horizontal axis, which is the minimum value Vmin, in the graph of FIG. To do. Further, since the atmospheric pressure becomes a vacuum and is substantially constant, the value of atmospheric pressure × gap length on the horizontal axis changes according to the gap length, and the larger the gap length, the smaller the breakdown voltage. Therefore, the region where the gap length is large is more likely to undergo dielectric breakdown than the region where the gap length is small.

The present inventor studied the conditions under which dielectric breakdown occurs due to such a gap length, and examined the use of an electrode that forms a recess in the contact portion.

By the way, dielectric breakdown under vacuum in a vacuum circuit breaker is different from dielectric breakdown in air in a gas atmosphere environment under atmospheric pressure or high pressure. In a gas atmosphere environment, electron multiplication progresses due to impact ionization of gas molecules and electrons accelerated by voltage, resulting in electron avalanche and dielectric breakdown. On the other hand, under the vacuum pressure handled by the vacuum breaker, the gas atmosphere is small, so the mean free path required for the electrons to collide with the gas molecules is extremely long, specifically, it comes out of the cathode. The length is such that the electrons collide with the electrode without collision. Therefore, the trigger of dielectric breakdown is the electrons generated by the field electron emission from the cathode first.

The present inventor considers that suppressing the generation of initial electrons due to such field electron emission is an important point in improving the insulation performance of the vacuum circuit breaker. Furthermore, as a result of various trials and errors, the present inventor has diligently studied the relationship between the suppression of initial electron generation due to field electron emission and the surface roughness of the contact portion, and in this research, the contact portion having the above-mentioned recess formed. We have devised an invention that can improve the insulation performance in Japan.

The present invention has been made in view of this point, and an object of the present invention is to provide a vacuum circuit breaker capable of improving the insulation performance at a contact portion.

The vacuum circuit breaker of one aspect of the present invention is a vacuum circuit breaker provided inside the vacuum vessel so as to be contactable and detachable, and includes a movable contactor and a fixed contactor that energize in a contact state and cut off the energization in a separated state. The movable contact and the electrode portion of the fixed contact include contact portions on which facing surfaces facing each other are formed, and at least one of the facing surfaces is in the contact state with the other facing surface. A contact region to be contacted and a recess having a distance from the other facing surface larger than the contact region are provided, and the bottom portion of the recess is formed to have a smaller maximum surface roughness (Rmax) than the contact region. It is characterized by that.

According to the present invention, since the contact portions of the contacts are separated under vacuum when the current is cut off, the electric field can be concentrated on the longer distance between the contact portions, that is, toward the bottom of the recess, as compared with the contact region. The recess can be easily discharged. Further, since the surface roughness of the concave portion is reduced, in other words, the surface roughness of the region where discharge is likely to occur is reduced, the generation of initial electrons due to field electron emission can be suppressed, and as a result, the insulation performance at the contact portion is improved. Can be done.

It is a schematic blocker which made a part view of the vacuum circuit breaker which concerns on 1st Embodiment. FIG. 2A is an explanatory view of the electrode portion of the fixed contact according to the first embodiment as viewed from above. FIG. 2B is a vertical sectional view taken along the line AA of FIG. 2A at the contact portion. 3A and 3B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the second embodiment. 4A and 4B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the third embodiment. 5A and 5B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the fourth embodiment. It is sectional drawing for explanation for explanation of the contact part which concerns on 5th Embodiment. It is sectional drawing for explanation for explanation of the contact part which concerns on 6th Embodiment. 8A and 8B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the seventh embodiment. It is sectional drawing for explanation for explanation of the contact part which concerns on 8th Embodiment. It is sectional drawing for explanation for explanation of the contact part which concerns on 9th Embodiment. It is sectional drawing for explanation for explanation of the contact part which concerns on tenth Embodiment. It is a graph of Paschen curve.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments, and can be appropriately modified and implemented without changing the gist thereof. In the following figures, some configurations may be omitted for convenience of explanation.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of a partial cross-sectional view of the vacuum circuit breaker according to the first embodiment. As shown in FIG. 1, the vacuum circuit breaker 10 includes a vacuum container 11, a movable contact 12 and a fixed contact 14 provided so as to be contactable and detachable inside the vacuum container 11. In the vacuum circuit breaker 10, the movable contact 12 and the fixed contact 14 are energized (closed) in a contact state (not shown), and the energization is cut off (open) in the separated state shown in FIG.

The vacuum container 11 includes an insulating cylinder 15 made of ceramic or the like, and end plates 16 and 17 provided so as to close the upper end side and the lower end side of the insulating cylinder 15 in FIG. 1. A movable contact 12 is provided on the upper end plate 16 so as to be vertically movable. A fixed contact 14 is fixed to the lower end plate 17.

The movable contact 12 includes a movable rod 19, and the movable rod 19 can move in the axial direction (vertical direction) while maintaining a vacuum state in the vacuum vessel 11 via an airtight member (not shown) such as a bellows. It is provided in. The movable rod 19 is connected to a blocking spring 20 serving as a tension spring, and is locked via a latch or the like (not shown) in a stretched state of the blocking spring 20, while the movable contact 12 and the fixed contact 14 Is in contact and energized. From this state, by operating the latch or the like, the movable side rod 19 is moved upward by the restoring force of the blocking spring 20 to separate the movable contact 12 from the fixed contact 14, and the energization is cut off.

The fixed contact 14 includes a fixed side rod 22, and the fixed side rod 22 is fixed via a fixed block 23 mounted on the lower end plate 17.

The movable contact 12 includes an electrode portion 30 at one end (lower end in the middle of FIG. 1) of the movable rod 19. The fixed contact 14 includes an electrode portion 40 at one end portion (upper end portion in FIG. 1) of the fixed side rod 22. In the present embodiment, the electrode portions 30 and 40 are provided so as to be vertically symmetrical and are arranged so as to face each other. A shield 25 that protects the inner peripheral surface of the insulating cylinder 15 is provided on the outside of each of the electrode portions 30 and 40.

The electrode portions 30 and 40 include electrode body portions 31 and 41 having a columnar outer shape, and disk-shaped contact portions 32 and 42 connected to the ends of the electrode body portions 31 and 41 by brazing or the like. ing. The upper surface of the contact portion 42 of the fixed contact 14 is formed as the facing surface 43, and is opposed to the facing surface 33 which is the lower surface of the contact portion 32 of the movable contact 12.

A plurality of inclined slits 34, 44 (six in the present embodiment) are formed in the electrode main bodies 31 and 41 so as to extend spirally while being inclined with respect to the axis. The inclined slits 34 and 44 are formed at a predetermined depth from the outer peripheral surfaces of the electrode main bodies 31 and 41. The contact portions 32 and 42 are formed with slits 35 and 45 having one end formed on the outer peripheral edge thereof, so that one end of the slits 35 and 45 and the upper ends of the inclined slits 34 and 44 are continuous.

FIG. 2A is a view of the electrode portion of the fixed contactor in the first embodiment as viewed from above. FIG. 2B is a vertical cross-sectional view taken along the line AA of FIG. 2A at the contact portion of the fixed contact. As shown in FIGS. 2A and 2B, the contact surface 43 of the contact portion 42 of the fixed contact 14 has a contact region 47 formed in an annular shape with a predetermined width along the outer peripheral edge thereof and an in-plane contact region 47. A recess 48 formed on the center side is formed. Due to the formation of the contact region 47 and the recess 48, the distance of the recess 48 to the facing surface 33 (see FIG. 1) of the movable contact 12 is longer in the facing surface 43 than in the contact region 47. Further, on the facing surface 43, a region in contact with the facing surface 33 of the movable contact 12 when energized (closed) is the contact region 47.

Here, the bottom portion 48a (the region with halftone dots in FIG. 2A) inside the recess 48 is formed as a smooth surface having a smaller maximum surface roughness (Rmax) than the contact region 47. As an example, the maximum surface roughness Rmax of the bottom portion 48a is formed to be 0.25 μm, and the maximum surface roughness Rmax of the contact region 47 is formed to be 8 μm.

A plurality of slits 45 (six in the present embodiment) are formed in the contact portion 42, and extend from one end of the outer peripheral edge of the contact portion 42 to the bottom portion 48a of the recess 48 which is inward. The other end (inner end) of the slit 45 is formed so as to be located at the bottom portion 48a which is inward from the boundary between the contact region 47 and the recess 48. Although not shown, the slit 35 has the same shape as the slit 45 in the contact portion 32 of the movable contact 12 although the recess is not formed in the facing surface 33. Due to the slits 35 and 45 and the inclined slits 34 and 44, the energizing paths of the electrode portions 30 and 40 are coiled to generate a vertical magnetic field (magnetic field in the direction parallel to the vertical direction in FIG. 1), and the breaking characteristics can be improved. Will be.

In the present embodiment, the facing surface 33 of the contact portion 32 of the movable contact 12 is formed as a flat surface except for the region where the slit 35 is formed, and the entire facing surface 33 is the contact region.

In the vacuum circuit breaker 10, in the energized state where the movable contact 12 and the fixed contact 14 are in contact with each other, the contact region 47 of the fixed contact 14 and the facing surface 33 of the movable contact 12 at a position facing the contact region 47 are in contact with each other. .. On the other hand, in the cutoff state, the facing surface 33 of the movable contact 12 and the contact region 47 of the fixed contact 14 and the bottom portion 48a of the recess 48 face each other in a non-contact state separated by a predetermined distance.

When the contact portions 32 and 42 of the fixed contact 14 and the movable contact 12 are separated from each other in order to cut off the current from the energized state by the vacuum circuit breaker 10, an arc is generated between the contact portions 32 and 42. ..

Immediately after the facing surfaces 33 and the contact area 47 that are in contact with each other are separated from each other at the contact portions 32 and 42 when the current is cut off, the facing surface 33 is separated from the distance between the facing surface 33 and the contact area 47. The separation distance between the recess 48 and the bottom 48a of the recess 48 is larger. Based on the explanation of the Paschen curve (see FIG. 12) described above, the bottom portion 48a of the recess 48 having a large separation distance from the facing surface 33 is in a state of being more easily discharged, and an arc is selectively generated. That is, it is possible to suppress the generation of an arc in the contact region 47 and make it possible to stably break down the insulation at the bottom 48a of the recess 48.

Further, since the surface roughness at the bottom 48a of the recess 48 is reduced, the surface roughness of the portion where dielectric breakdown occurs can be reduced, and the generation of initial electrons due to the above-mentioned field electron emission can be suppressed at the bottom 48a. it can. As a result, the trigger for dielectric breakdown is less likely to occur, the dielectric breakdown voltage can be maintained at a high value, the insulation performance between the facing surface 33 and the bottom portion 48a of the recess 48 can be improved, and by extension, the breaking performance of the vacuum circuit breaker 10. Can be improved.

Here, when the current is cut off, macroscopic electric field concentration is generated at the edge portions in the slits 35 and 45 for generating the longitudinal magnetic field. Since the slit 45 of the fixed contact 14 is formed in both the bottom portion 48a of the recess 48 and the contact region 47, the electric field is concentrated and dielectric breakdown occurs at the edge portion of the slit 45 located in the bottom portion 48a, which is more easily discharged. Will be. As a result, dielectric breakdown in the contact region 47 can be prevented, dielectric breakdown can be stably performed in the recess 48, and dielectric breakdown (dielectric breakdown voltage) can be improved.

According to the first embodiment as described above, the ultimate withstand electric field strength can be increased by setting the maximum surface roughness Rmax of the bottom portion 48a to be small. The ultimate electric field strength varies greatly depending on the electrode material, the ultimate vacuum degree, the presence or absence of conditioning, and the processing conditions, but it is about 1. With a change in the maximum surface roughness Rmax of the bottom 48a (for example, 2.5 μm and 0.8 μm). It can rise about 7 times.

By the way, in the vacuum circuit breaker 10, the contact area 47 comes into contact with or pressurizes the facing surface 33 of the movable contact 12 during storage, distribution, and construction, and each contact 12 is used during a test before actual operation. 14 may be repeatedly opened and closed. Even in this case, the bottom portion 48a of the recess 48 can be kept in non-contact with the contact portion 32 of the movable contactor 12, and a good surface condition with a small maximum surface roughness can be stably maintained. It can be secured and the above-mentioned insulation performance can be maintained. Moreover, the contact region 47 has a rougher surface than the bottom 48a of the recess 48, and the contact region 47 tends to be rougher even if a test or transportation is performed before actual operation. It is possible to facilitate maintaining such a relationship.

Next, embodiments of the present invention other than the above will be described. In the following description, the same reference numerals may be used for the same or equivalent components as those of the embodiments described prior to the embodiments described, and the description may be omitted or simplified. Further, in the drawings of FIGS. 3 and 3 onward, the region with halftone dots similar to that of FIG. 2A is formed to have the same maximum surface roughness as the bottom portion 48a of the first embodiment.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. 3A and 3B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the first embodiment. As shown in FIGS. 3A and 3B, in the second embodiment, the shape of the recess 48 is changed from that of the first embodiment.

In the second embodiment, the recess 48 is formed in a groove shape and is formed along the locus of one circle (closed loop) having the same center as the outer peripheral edge of the contact portion 42. Also in the second embodiment, the other end (inner end) of the slit 45 is formed so as to be located at the bottom 48a of the recess 48. In addition, on the facing surface 43 of the contact portion 42, not only the outer region of the recess 48 but also the inner region is formed as the contact region 47. Also in the second embodiment, the bottom portion 48a is formed as a smooth surface having a smaller maximum surface roughness (Rmax) than the contact region 47.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG. 4A and 4B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the third embodiment. As shown in FIGS. 4A and 4B, in the third embodiment, the point where the groove-shaped recesses 48 are doubly formed concentrically is different from that of the second embodiment. In the third embodiment, the other end (inner end) of the slit 45 is formed so as to be located at the bottom 48a of the inner recess 48 of the double recess 48.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described with reference to FIG. 5A and 5B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the fourth embodiment. As shown in FIGS. 5A and 5B, the fourth embodiment is different from the second embodiment in that the groove-shaped recesses 48 are formed in triple concentric circles. In the fourth embodiment, the other end (inner end) of the slit 45 is formed so as to be located at the bottom 48a of the outermost recess 48 of the triple recess 48. According to the second to fourth embodiments, even if the recess 48 is formed in a groove shape, the same effect as that of the first embodiment can be obtained, and in consideration of ease of processing, material, and the like. By changing the number of recesses 48 formed, the effect of reducing the manufacturing cost and the effect of improving the insulation performance can be obtained in a well-balanced manner.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is an explanatory sectional view of a contact portion according to a fifth embodiment. As shown in FIG. 6, in the fifth embodiment, the contact portion 32 of the movable contact 12 also has the same recess as the recess 48 in the contact portion 42 of the fixed contact 14 as compared with the first embodiment. 38 is formed. In FIG. 6, the sizes and shapes of the recesses 38 and 48 in a plan view are the same, but the size, shape, and formation position of the recesses 38 and 48 may be different.

According to the fifth embodiment, the distance (gap length) between the bottoms 38a and 48a of the recesses 38 and 48 can be increased, and stable insulation performance can be maintained even in a high electric field.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is an explanatory sectional view of a contact portion according to a sixth embodiment. As shown in FIG. 7, in the sixth embodiment, the recess 38 in the contact portion 32 of the movable contact 12 is changed from the fifth embodiment.

In the sixth embodiment, the recess 38 of the movable contact 12 is formed in a groove shape along the locus of a circle like the recess 48 of the second embodiment. In FIG. 7, the recess 38 of the movable contact 12 is formed to have a larger shape and dimension than the recess 48 of the fixed contact 14, and is set at a position where it does not overlap vertically. According to the sixth embodiment, it is difficult for the parts to be dielectrically broken down to be the same, and the degree of freedom of the parts can be secured.

[7th Embodiment]
Next, a seventh embodiment of the present invention will be described with reference to FIG. 8A and 8B are explanatory views similar to those of FIGS. 2A and 2B of the electrode portion according to the seventh embodiment. As shown in FIGS. 8A and 8B, in the seventh embodiment, in contrast to the first embodiment, a step is provided at the bottom 48a of the recess 48 to form a shape having two steps of height. .. The number of steps may be increased as appropriate.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 9 is an explanatory sectional view of a contact portion according to an eighth embodiment. As shown in FIG. 9, in the eighth embodiment, as compared with the fifth embodiment, steps are provided at the bottoms 38a and 48a of both the recesses 38 and 48 to form a shape having two steps of height. are doing.

[9th Embodiment]
Next, a ninth embodiment of the present invention will be described with reference to FIG. FIG. 10 is an explanatory sectional view of a contact portion according to a ninth embodiment. As shown in FIG. 10, in the ninth embodiment, as compared with the sixth embodiment (see FIG. 7), the bottoms 38a and 48a of both the recesses 38 and 48 are provided with steps to increase the height of two steps. It is formed in a shape having.

[10th Embodiment]
Next, a tenth embodiment of the present invention will be described with reference to FIG. FIG. 11 is an explanatory sectional view of a contact portion according to the tenth embodiment. As shown in FIG. 11, in the tenth embodiment, as compared with the fifth embodiment (see FIG. 6), a step is provided at the bottom 38a of the recess 38 in the movable contact 12 to increase the height of two steps. It is formed in a shape that it has. The recess 48 of the fixed contact 14 is formed in a shape having no step, as in the first and fifth embodiments.

By setting the bottoms 38a and 48a to two steps of height as in the seventh to tenth embodiments, the distance between the bottoms 38a and 48a, which is the gap length, and the bottoms 38a and 48a and facing the bottoms 38a and 48a. The distance between the facing surfaces 33 and 43 can be increased, and stable insulation performance can be maintained even in a high electric field.

The present invention is not limited to each of the above embodiments, and various modifications can be made. In the above embodiment, the size, shape, orientation, etc. shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

In each of the above embodiments, if the contact portion 32 of the movable contact 12 and the contact portion 42 of the fixed contact 14 differ in the shape, size, formation position, and presence / absence of formation of the recesses 38 and 48. , The shapes of the contact portions 32 and 42 may be reversed. Further, the shapes of the recesses 38 and 48 when viewed in a plan view are not limited to circular and annular shapes, and are elliptical or polygonal as long as the maximum surface roughness Rmax of the bottoms 38a and 48a is small. Various changes are possible, such as.

Further, the slits 35 and 45 may be formed discontinuously with respect to the extending direction as long as the same longitudinal magnetic field as in each of the above embodiments is generated. However, it is preferable that a part of the slits 35 and 45 is formed in the bottoms 38a and 48a of the recesses 38 and 48 in order to generate macroscopic electric field concentration when the current is cut off.

Further, in the electrode portions 30 and 40, the contact portions 32 and 42 and the electrode main body portions 31 and 41 are fixed as separate bodies, but these may be integrally formed.

10 Vacuum circuit breaker 11 Vacuum vessel 12 Movable contact 14 Fixed contact 30 Electrode 32 Contact 33 Opposing surface 35 Slit 37 Contact area 38 Recess 38a Bottom 40 Electrode 42 Contact 43 Opposing surface 45 Slit 47 Contact area 48 Recess 48a bottom

Claims (3)

A vacuum circuit breaker equipped with a movable contactor and a fixed contactor that are provided inside the vacuum vessel so as to be detachable and energize in a contact state and cut off the energization in a separated state.
The movable contact and the electrode portion of the fixed contact include contact portions having facing surfaces facing each other.
At least one of the facing surfaces is provided with a contact region that contacts the other facing surface in the contact state and a recess that has a greater distance from the other facing surface than the contact region.
A vacuum circuit breaker characterized in that the bottom of the recess is formed so that the maximum surface roughness (Rmax) is smaller than that of the contact region. The vacuum circuit breaker according to claim 1, wherein the contact portion is provided with a slit for generating a longitudinal magnetic field on the facing surface. The vacuum circuit breaker according to claim 2, wherein the slit extends from the outer edge of the contact portion to the bottom portion of the recess.

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