Arc extinguishing chamber of the switch, and the switch

Abstract

To provide an arc-extinguishing chamber of a circuit breaker, capable of recovering insulation resistance in a first period while enhancing arc-extinguishing performance of an arc generated between a stationary contact and a movable contact, and provide a circuit breaker.SOLUTION: An arc-extinguishing chamber 40 of a circuit breaker 1, is a thermoplastic resin formed by polyacetal or polyamide. The arc-extinguishing chamber is formed by a foam formation body when forming the arc-extinguishing chamber 40, supercritical fluid of one inactive gas selected from nitrogen, carbon dioxide, and sulfur hexafluoride is ejected and formed as a foam agent to the thermoplastic resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an arc extinction chamber of a switch and a switch. Specifically, it relates to an arc extinction chamber of a switch and a switch that can enhance the arc extinction performance generated between a fixed contact and a movable contact and can quickly recover the insulation withstand voltage.

Background Art

[0002] Generally, high-voltage power distribution lines drawn from a substation are stretched in a mesh pattern by a large number of utility poles erected in the city to supply power to consumers. Such utility poles are equipped with switches for the responsibility demarcation point at the entrance of consumers or for separating power distribution line sections for work areas and accident areas. For example, when an abnormality occurs, during inspection and repair work of electrical equipment, etc., this switch is operated to temporarily cut off the flow of current.

[0003] This type of switch includes a movable contact made of a strip and a fixed contact made of a pair of strips. When the movable contact separates from the fixed contact, an arc is generated between the movable contact and the fixed contact. Since the arc generated in the switch affects each device inside the switch, various proposals have been made conventionally to quickly extinguish the generated arc.

[0004] For example, Patent Document 1 discloses a switch provided with an arc extinction chamber made of an insulating resin having a slit portion (arc guide) that generates an arc-extinguishing gas when an arc touches it. According to Patent Document 1, the slit portion is provided along the rotation locus of the movable contact, guiding the generated arc while stretching it inside the slit portion, ejecting an arc-extinguishing gas when the arc passes through the slit portion, and cooling and extinguishing the arc with this gas.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Incidentally, the larger the current value to be interrupted, the greater the arc energy generated during interruption. Even if the current is interrupted, it may reignite and become impossible to interrupt. This phenomenon of reigniting after interruption is thought to occur frequently when the current reaches zero and the arc is extinguished at an early stage after the movable contact separates from the fixed contact, if the separation distance between the two contacts is short, if the dielectric strength in the arc extinguishing chamber has not recovered sufficiently, or if the electrical resistance has decreased due to the carbon and metal vapor-deposited phases in the arc extinguishing chamber.

[0007] Furthermore, insufficient recovery of dielectric strength within the arc extinguishing chamber means that the density of ionized and plasma-formed gases with no dielectric strength within the chamber, induced by the arc during interruption, increases. This means that even if the current is interrupted, it can reignite without waiting for the insulation within the arc extinguishing chamber to recover, leading to an inability to interrupt the current.

[0008] In conventional arc extinguishing chambers, the narrower the gap in the arc guide, the more the inner wall of the gap is exposed to the arc. As a result, the gas ejected from the inner wall of the arc extinguishing chamber is accelerated, the arc is cooled more easily, and consequently the current interruption performance improves. However, if the gap in the arc guide is made too narrow, the gas exhaust passage becomes narrower, and ionized and plasma-formed gases with no dielectric strength are not quickly discharged outside the arc guide, resulting in poor insulation recovery characteristics and making it easier for the current to become uninterruptible upon re-ignition. These are conflicting problems.

[0009] Meanwhile, investigations are underway into the issue of carbon deposits on the inner walls and contact points of the arc extinguishing chamber, which can lead to a decrease in electrical resistance and thus prevent interruption. However, a solution has not yet been found. In conventional arc extinguishing chambers equipped with arc guides, the inner walls of the arc guide are uniformly exposed to the arc and carbonized. Therefore, as the value of the current to be interrupted increases, carbonization within the arc guide is accelerated. Furthermore, repeated interruptions naturally lead to carbonization within the arc guide, and ultimately, the resulting decrease in insulation prevents sufficient insulation recovery during load switching, leading to re-ignition and a state of interruption failure.

[0010] The present invention was conceived in view of the above points, and aims to provide an arc extinguishing chamber for a switch and a switch that can improve the arc extinguishing performance of arcs generated between fixed contacts and movable contacts, and can quickly restore dielectric strength. [Means for solving the problem]

[0011] To achieve the above objective, the arc extinguishing chamber of the switch of the present invention is an arc extinguishing chamber provided to cover the fixed contact of the switch, and the arc extinguishing chamber is made of a foamed molded body formed by foaming a thermoplastic resin with a supercritical fluid of an inert gas as a foaming agent.

[0012] Here, the arc-extinguishing chamber of the switch is a foamed molded body formed by foaming a thermoplastic resin with a supercritical fluid of inert gas as a foaming agent, which allows fine inert gas particles to be dispersed densely and uniformly within the foamed molded body.

[0013] With the above configuration, the heat generated during arc generation releases both the pyrolysis gas from the arc extinguishing chamber itself and the inert gas dispersed within the chamber due to the melting of the inner wall by the heat of the arc. In this way, when an arc is generated, the release of arc-extinguishing pyrolysis gas and inert gas (collectively referred to as "arc-extinguishing gas") allows the arc to be extinguished quickly. Furthermore, since the inert gas is uniformly dispersed within the arc extinguishing chamber, the inert gas can be reliably released each time the fixed contact and movable contact are shut off, even if the shutoff is repeated.

[0014] Furthermore, since the arc extinguishing chamber is formed by micro-foaming a supercritical fluid of an inert gas as a foaming agent, a fine uneven surface is formed on the inner wall surface where the arc makes contact. This uneven surface increases the surface area of ​​the arc extinguishing chamber where the arc makes contact, and also increases the amount of arc-extinguishing gas released, so that carbon and metal phases that adhere to the inner wall of the arc extinguishing chamber due to the arc can be discharged from the system. Consequently, it is possible to suppress the decrease in electrical resistance due to carbonization caused by carbon adhering to the inner wall surface and contact points of the arc extinguishing chamber, and furthermore, to restore the dielectric strength inside the arc extinguishing chamber at an earlier stage.

[0015] Furthermore, if the amount of inert gas contained in the foamed molded product is 5% to 15% by volume relative to the total volume of the thermoplastic resin in its non-foamed state, it becomes possible to release a sufficient amount of inert gas into the arc extinguishing chamber without impairing the original mechanical properties (elasticity, strength, etc.) of the thermoplastic resin.

[0016] Furthermore, if the inert gas content exceeds 15% by volume relative to the total volume of the thermoplastic resin, it may affect the mechanical properties of the thermoplastic resin, potentially leading to increased pressure during arc generation or weakening its resistance to impacts generated when the movable contact is inserted into or removed from the fixed contact.

[0017] On the other hand, if the amount of inert gas is less than 5% by volume relative to the total volume of the thermoplastic resin, the mechanical properties can be improved, but because the amount of inert gas released is small, the arc extinguishing performance when an arc is generated will be inferior.

[0018] Furthermore, if the inert gas consists of one of nitrogen, carbon dioxide, and sulfur hexafluoride, or a mixture of two or more of these, these inert gases are chemically stable and have high insulating and cooling properties, allowing the arc in the arc extinguishing chamber to be extinguished quickly by these inert gases.

[0019] Furthermore, if the thermoplastic resin is polyacetal or polyamide, these thermoplastic resin materials have high insulation properties, excellent abrasion resistance, and fatigue resistance, thus preventing damage to the arc extinguishing chamber due to impact during arc generation.

[0020] Furthermore, if the voids in the foamed molded body are between 50 μm and 500 μm, the arc extinguishing performance during arc generation can be improved by uniformly dispersing the fine foam within the arc extinguishing chamber.

[0021] Furthermore, if the void size of the foamed molded body exceeds 500 μm, the mechanical strength of the arc extinguishing chamber decreases, and there is a risk that the arc extinguishing chamber may be damaged by the impact when an arc is generated. On the other hand, if the void size is less than 50 μm, the amount of inert gas released decreases, resulting in inferior arc extinguishing performance when an arc is generated.

[0022] To achieve the above objective, the present invention provides a switch comprising a fixed contact, a movable contact that moves toward and away from the fixed contact, and an arc-extinguishing chamber provided to cover the fixed contact, wherein the arc-extinguishing chamber is made of a foamed molded body formed by foaming a thermoplastic resin with a supercritical fluid of an inert gas as a foaming agent.

[0023] With the above configuration, arc-extinguishing gas can be released into the arc-extinguishing chamber when an arc occurs, thus extinguishing the arc quickly. Furthermore, since the inert gas is uniformly dispersed within the arc-extinguishing chamber, the inert gas can be reliably released each time the fixed and movable contacts are shut off, even if the shutoff is repeated. Therefore, damage to the equipment inside the switchgear caused by arcing can be protected.

[0024] In addition, when the arc extinguishing chamber has a slit provided along the movement locus of the movable contact, in addition to the thermal decomposition gas released from the arc extinguishing chamber itself, an inert gas is released, so that the pressure in the slit can be increased further. Therefore, the arc extinguishing performance in the slit can be enhanced, and the arc can be surely extinguished.

Effects of the Invention

[0025] The arc extinguishing chamber and the switch of the switch according to the present invention can enhance the arc extinguishing performance of an arc generated between the fixed contact and the movable contact, and can quickly restore the insulation withstand voltage.

Brief Description of the Drawings

[0026] [Figure 1] It is an overall external view of a switch according to an embodiment of the present invention. [Figure 2] It is a front sectional view of a switch according to an embodiment of the present invention. [Figure 3] It is an overall external view of an arc extinguishing chamber according to an embodiment of the present invention. [Figure 4] It is a sectional view of a main part of an arc extinguishing chamber according to an embodiment of the present invention. [[ID=3G]]

Mode for Carrying Out the Invention

[0027] Hereinafter, the arc extinguishing chamber and the switch of the switch according to the embodiment of the present invention will be described with reference to the drawings for the purpose of understanding the present invention.

[0028] (Switch) First, the overall configuration of the switch 1 according to the embodiment to which the present invention is applied will be described with reference to FIGS. 1 and 2. The switch 1 is, for example, a pole-mounted switch installed on a utility pole as a responsibility demarcation point at the entrance of a customer, and various power supply devices 20 are housed in a metal case 10.

[0029] Here, switch 1 does not necessarily have to be a pole-mounted switch. For example, any switch that can switch the load current under normal conditions and also close the abnormal current in the case of a short circuit in the circuit can be used for any purpose.

[0030] (Connection terminals) One side of the case 10 is provided with a power supply side bushing 21a having a power supply side connection terminal 22 that connects to a power distribution line in the power distribution system, and the other side of the case 10 is provided with a load side bushing 21b having a load side connection terminal 23 that connects to a power distribution line (hereinafter, the power supply side bushing 21a and the load side bushing 21b are collectively referred to as "bushing 21"). A fixed contact 24 is connected to the power supply side bushing 21a, and a movable contact 25 is connected to the load side bushing 21b.

[0031] Here, Figure 1 shows a case where there are three bushings 21 in a pair, i.e., a total of six bushings 21. However, the bushings 21 may consist of one, two, or four or more bushings in a pair, or two or more pairs.

[0032] The movable contact 25 is pivotally supported on a rotating shaft so as to be able to move toward and away from the fixed contact 24. The state in which the movable contact 25 is in contact with the fixed contact 24 is defined as the closed state of the main contact (circuit), and the state in which the movable contact 25 is separated from the fixed contact 24 is defined as the open state of the main contact (circuit). The opening and closing of the main contacts between the fixed contact 24 and the movable contact 25 is achieved by a manual handle 30 or by an operating mechanism including a solenoid (not shown).

[0033] (arc extinguishing room) An arc extinguishing chamber 40 is provided at the inner end of the power supply side bushing 21a. As shown in Figure 3, the arc extinguishing chamber 40 has a main body portion 41 that covers the fixed contact 24, and a narrow gap portion 42 is provided on the main body portion 41, which is formed to be narrower than the width of the main body portion 41 and is used to guide the arc. In a side view, the narrow gap portion 42 is shaped to follow the rotation trajectory of the movable contact 25, and the movable contact 25 can be inserted into the narrow gap portion 42 through an opening 43 formed at the tip of the narrow gap portion 42.

[0034] Here, the arc extinguishing chamber 40 does not necessarily have to be of the structure described above. It may be equipped with an arc extinguishing grid in which multiple arc extinguishing plates are held at predetermined intervals and stacked, or it may be equipped with an arc extinguishing shutter that can be displaced between a retracted position in which it is moved away from the narrow gap and inside the fixed contactor, and a shielding position in which it closes the end of the narrow gap on the fixed contactor side.

[0035] The arc extinguishing chamber 40 is made of a thermoplastic resin consisting of polyacetal or polyamide. When the arc extinguishing chamber 40 is molded, a supercritical fluid of one inert gas selected from nitrogen, carbon dioxide, and sulfur hexafluoride is injected into the thermoplastic resin as a foaming agent.

[0036] Here, the resin material for the arc extinguishing chamber 40 does not necessarily have to be selected from either polyacetal or polyamide; any thermoplastic resin is acceptable. However, since polyacetal and polyamide have excellent insulating properties, abrasion resistance, and fatigue resistance, using these thermoplastic resins can further enhance the performance of the arc extinguishing chamber.

[0037] Furthermore, it is not always necessary to use a supercritical fluid of one inert gas selected from nitrogen, carbon dioxide, and sulfur hexafluoride as a blowing agent during injection molding. Inert gases formulated with nitrogen, carbon dioxide, and sulfur hexafluoride individually may be used, or other inert gases may be mixed.

[0038] (supercritical fluid) Here, in the embodiments of the present invention, "supercritical fluid" refers to a fluid that exhibits properties intermediate between a gaseous state and a liquid state under conditions above a specific temperature and pressure (critical point). Therefore, by using it as a foaming agent, its penetrating power (dissolving power) into the molten thermoplastic resin is stronger than that of a liquid.

[0039] Figure 4 shows the cross-sectional shape of an arc-extinguishing chamber 40 that has been injection-molded using a supercritical fluid of an inert gas as a foaming agent. As shown in Figure 4, by using a supercritical fluid of an inert gas as a foaming agent, fine inert gas bubbles A can be uniformly and densely dispersed inside the arc-extinguishing chamber 40.

[0040] With the above configuration of the arc extinguishing chamber 40, in addition to the pyrolysis gas ejected from the arc extinguishing chamber 40 by the heat of the arc generated when the movable contact 25 is engaged with and disengaged from the fixed contact 24, an inert gas evenly distributed inside the arc extinguishing chamber 40 is released to the outside. In this way, since the pyrolysis gas and the inert gas are ejected into the arc extinguishing chamber 40 simultaneously, it is possible to reliably and quickly extinguish the arc with these arc-extinguishing gases.

[0041] Furthermore, because bubbles A are densely and uniformly dispersed inside the arc-extinguishing chamber 40, an uneven surface S is formed on the inner wall surface of the arc-extinguishing chamber 40, as shown in Figure 4. This uneven surface S increases the surface area of ​​the arc-extinguishing chamber 40, further increasing the amount of arc-extinguishing gas released and thus improving the arc-extinguishing performance of the arc-extinguishing chamber 40. Moreover, since a new uneven surface S is formed after the arc-extinguishing gas is released, the surface is always less contaminated, making it possible to quickly recover the dielectric strength of the arc-extinguishing chamber 40.

[0042] The size of the inert gas-filled bubble A varies depending on the manufacturing conditions during injection molding, but is preferably in the range of approximately 50 μm to 500 μm. If the size of bubble A is larger than 500 μm, the void volume in the arc extinguishing chamber 40 increases, which significantly reduces the mechanical strength of the arc extinguishing chamber 40, and there is a risk that the arc extinguishing chamber 40 may be damaged by the impact when the arc is generated.

[0043] On the other hand, if the size of bubble A is less than 50 μm, although the mechanical strength against impact by the arc increases, the amount of inert gas released decreases, which weakens the arc extinguishing performance and may prevent the arc from being reliably extinguished. Therefore, it is preferable that the size of bubble A is in the range of 50 μm to 500 μm.

[0044] Furthermore, when the bubble size is 50 μm to 500 μm as described above, the volume fraction of bubble A relative to the total volume of the thermoplastic resin is approximately 5% to 15%. In other words, when the volume fraction of bubble A is approximately 5% to 15%, it becomes possible to release a sufficient amount of inert gas into the arc extinguishing chamber 40 without impairing the original mechanical properties (elasticity, strength, etc.) of the thermoplastic resin.

[0045] Furthermore, if the inert gas content exceeds 15% by volume relative to the total volume of the thermoplastic resin, it may affect the mechanical properties of the thermoplastic resin, potentially leading to increased pressure during arc generation or weakening its resistance to impacts generated when the movable contact is inserted into or removed from the fixed contact. On the other hand, if the inert gas content is less than 5% by volume relative to the total volume of the thermoplastic resin, the mechanical properties can be improved, but the reduced release of inert gas will result in inferior arc extinguishing performance during arc generation. [Examples]

[0046] Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0047] [Example 1] An arc-extinguishing chamber was prepared using polyacetal resin and supercritical nitrogen fluid as a foaming agent, resulting in uniformly fine foaming with an average thickness of 100 μm or less and a nitrogen gas volume percentage of 10%. A barrier test was then conducted.

[0048] In the arc extinguishing test, when an arc was generated, the thermal decomposition gas of the polyacetal resin and the inert gas (nitrogen gas) released from the foamed molded body were released into the arc extinguishing chamber. The release of the arc-extinguishing gas increased the pressure inside the arc extinguishing chamber, causing the arc-extinguishing gas to be forcefully ejected outwards from the narrow gaps. This reliably extinguished the arc at the zero point of the current, and the current was interrupted without the need for re-ignition.

[0049] This shutoff test was performed 50 times consecutively, and it was confirmed that the system could shut off without re-ignition in all cases. Furthermore, the internal condition of the arc extinguishing chamber (degree of soot or metal phase deposition) after the 50 shutoff tests did not change significantly from the condition inside the arc extinguishing chamber at the time of the first (initial) shutoff.

[0050] [Example 2] An arc-extinguishing chamber was prepared using polyacetal resin and supercritical carbon dioxide fluid as a foaming agent, resulting in uniformly fine foaming with an average thickness of 300 μm or less and a volume percentage of carbon dioxide gas of 15%. A shutoff test was then conducted.

[0051] Fifty consecutive interruption tests were conducted, and it was confirmed that the current could be interrupted without re-lighting in all cases. Furthermore, the internal condition of the arc extinguishing chamber (degree of soot or metal phase deposition) after 50 interruption tests did not change significantly from the condition inside the arc extinguishing chamber at the time of the first interruption.

[0052] [Comparative Example 1] Using polyacetal resin, an arc extinguishing chamber free of internal air bubbles was fabricated by conventional injection molding, and the same interruption tests as in Examples 1 and 2 were performed. The interruption tests were performed 50 times consecutively, and the current was interrupted without re-lighting in all cases.

[0053] However, after the interruption test, the inside of the arc extinguishing chamber showed significantly more soot and metallic phase deposits compared to the first interruption, confirming the accumulation of contamination. This is thought to be because, in Comparative Example 1, only pyrolysis gas is released into the arc extinguishing chamber as the arc extinguishing gas, resulting in a relatively smaller release of arc extinguishing gas compared to Examples 1 and 2. Furthermore, in Comparative Example 1, there is a risk that the dielectric strength inside the arc extinguishing chamber will deteriorate, and that repeated interruptions may make re-ignition or current interruption difficult.

[0054] [Comparative Example 2] An arc-extinguishing chamber was constructed using polyacetal resin and supercritical nitrogen fluid as a foaming agent, with an average diameter of 300 μm, containing locally distributed relatively large bubbles ranging from 0.6 mm to 0.8 mm in diameter, and with a nitrogen gas volume percentage of 18%. A barrier test was then conducted.

[0055] The results of the shutdown tests showed that the arc extinguishing chamber could not withstand the pressure increase during arc generation, or the impact applied when the movable contact was applied to and released from the fixed contact. During the 32nd shutdown test, a crack formed in the arc extinguishing chamber, starting from the location where a large bubble had formed. However, there was no difference in the amount of soot and metallic phase deposits inside the arc extinguishing chamber after the 32nd shutdown test compared to the first shutdown test.

[0056] Comparative Example 2 showed that using supercritical nitrogen fluid as a foaming agent can prevent the adhesion of soot and metal phases inside the arc extinguishing chamber by releasing an inert gas, but that when the volume percentage of nitrogen gas exceeds 15 volume%, it affects the mechanical properties of the resin.

[0057] [Comparative Example 3] An arc-extinguishing chamber was constructed using polyacetal resin and supercritical carbon dioxide fluid as a foaming agent, with an average diameter of 500 μm, containing relatively large bubbles of 0.6 mm to 0.8 mm in some areas, and with a volume percentage of 20% carbon dioxide gas. A blockage test was then conducted in this chamber.

[0058] The shut-off tests revealed that the arc extinguishing chamber could not withstand the pressure increase during arc generation, or the impact applied when the movable contact was applied to and released from the fixed contact. During the 19th shut-off test, a crack formed in the arc extinguishing chamber, starting from the location where a large bubble had formed. However, the amount of soot and metallic phase deposits inside the arc extinguishing chamber after the 19th shut-off test was no different from that after the first shut-off test.

[0059] Comparative Example 3 showed that using supercritical carbon dioxide fluid as a foaming agent can prevent the adhesion of soot and metal phases inside the arc extinguishing chamber by releasing an inert gas, but that when the volume percentage of carbon dioxide gas exceeds 15 volume%, it affects the mechanical properties of the resin.

[0060] From the results of the above examples and comparative examples, it was confirmed that the arc extinguishing chamber of the examples efficiently and uniformly generates arc-extinguishing gas within the chamber, suppresses the decrease in electrical resistance due to contamination of the inner wall surface of the arc extinguishing chamber, and furthermore, enables reliable current interruption by quickly restoring dielectric strength.

[0061] As described above, the arc extinguishing chamber and the switch according to the present invention enhance the arc extinguishing performance of the arc generated between the fixed contact and the movable contact, and enable the dielectric strength to be restored at an early stage. [Explanation of Symbols]

[0062] 1 Switch 10 cases 20 Power equipment 21 Bushing 21a Power supply side bushing 21b Load-side bushing 22 Power supply side connection terminals 23 Load-side connection terminal 24 Fixed contact 25 Movable contact 30 Manual handle 40 Arc room 41 Main body 42 Slit 43 Opening A bubbles S Concave-convex surface

Claims

1. In an arc extinguishing chamber provided to cover the fixed contacts of a switch, The arc-extinguishing chamber is made of a foamed molded body formed by foaming a thermoplastic resin with a supercritical fluid of an inert gas as a foaming agent. Arc extinguishing chamber of a switch.

2. The inert gas contained in the foamed molded body is 5% to 15% by volume relative to the total volume of the thermoplastic resin. Arc extinguishing chamber of a switch according to claim 1.

3. The inert gas consists of one selected from nitrogen, carbon dioxide, and sulfur hexafluoride, or a mixture of two or more of these. Arc extinguishing chamber of a switch according to claim 1 or claim 2.

4. The thermoplastic resin is polyacetal or polyamide. Arc extinguishing chamber of a switch according to claim 1 or claim 2.

5. The voids in the foamed molded body are 50 μm to 500 μm. Arc extinguishing chamber of a switch according to claim 1 or claim 2.

6. A switch comprising a fixed contact, a movable contact that moves toward and away from the fixed contact, and an arc-extinguishing chamber provided to cover the fixed contact, The arc-extinguishing chamber is made of a foamed molded body formed by foaming a thermoplastic resin with a supercritical fluid of an inert gas as a foaming agent. Switch.

7. The arc extinguishing chamber has a narrow gap provided along the movement trajectory of the movable contactor. The switch according to claim 6.

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