JPS6357897B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vacuum shield breaker, and more particularly to a vacuum shield breaker equipped with a vertical magnetic field type electrode that suppresses the generation of abnormal voltage due to switching surges. In general, the following conditions must be met for the electrodes of vacuum shields and disconnectors: (1) Excellent static withstand voltage characteristics. (2) It has a large ability to cut off current. (3) Large current carrying capacity. (4) Excellent welding resistance. (5) Capable of dealing with overvoltage caused by switching surges. (6) Excellent electrical and mechanical life. However, in recent years, research on the switching surge phenomenon has progressed, and in addition to the conventionally known rupture surges and re-ignition surges, multiple re-ignition surges and surges due to three-phase simultaneous rupture associated with multiple re-ignition surges have become known. Therefore, there is a need for an electrode that can cope with these problems. Here, multiple re-ignition surge is a phenomenon in which the voltage gradually increases as the arc alternately repeats firing and extinguishing due to the competition between the insulation recovery between the poles and the circuit voltage due to the vacuum breaker's rupture. This is thought to be caused by high-frequency arc extinguishing, where the vacuum breaker immediately cuts off the high-frequency current flowing through the circuit at its zero point when it re-ignites, and the vacuum breaker breaks the arc without enough arc time. This occurs when the arc is opened near the zero point of the commercial frequency current and immediately extinguished at the current zero point immediately after that. In addition, when multiple re-ignition surges occur in a three-phase circuit, the high-frequency current due to the re-ignition flows to the other phase through the impedance between the phases, causing the commercial frequency of the other phase to The currents are canceled and a current zero point is forcibly created, and at this current zero point, the three phases are simultaneously cut off, and the current is larger than the cutting current of the vacuum shield breaker, sometimes even the commercial frequency current. This is a phenomenon in which extremely large surges occur, which is the same result as cutting off the wave height. However, vacuum breakers equipped with vertical magnetic field electrodes made of contact materials that are currently commercially available are susceptible to multiple re-ignition surges and three-phase simultaneous disconnections due to multiple re-ignition surges. Unable to cope with the surge caused by. Currently, a surge absorber (surge suppressor) is installed in the circuit to protect the circuit. Therefore, as a vacuum switchgear, there are problems such as the overall size of the device increases, the reliability of the circuit decreases, and the cost increases. The present invention has been made in view of the above-mentioned problems, and its object is to provide a cap-shaped disk-shaped electrode or a disk-shaped contact and a ring disposed around the electrode to make the contact protrude. In a vacuum shield disconnector equipped with a vertical magnetic field type electrode consisting of a disk-shaped arc electrode and a coil body disposed on the back of each electrode to generate an axial magnetic field, a cap-shaped disk-shaped electrode is used. is made of a chromium alloy metal material containing pure chromium and 10% or less of a conductive metal such as copper or silver, and the arc electrode has a vapor pressure slightly higher than that of the metal material of the contact. By forming the arc from pure iron or a metal material mainly composed of pure iron, which allows the arc to easily move from the contact, it can withstand multiple re-ignition surges and multiple re-ignition surges without compromising the necessary conditions for an electrode. An object of the present invention is to provide a vacuum shield disconnector equipped with an electrode capable of suppressing surges caused by three-phase simultaneous disconnection. Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of a vacuum sheath disconnector according to the present invention, which consists of a plurality (two in this embodiment) of insulating cylinders made of glass or ceramic formed into a cylindrical shape. 1, 1 are coaxially joined via one sealing fitting 2, 2 implanted at both ends to form a single insulating cylinder, and both open ends are connected to metal via the other sealing fitting 2, 2. A vacuum container 4 is formed by airtightly closing the end plates 3, 3 in the shape of a disc, and evacuating the inside to a high vacuum. In order to bring the paired fixed side and movable side electrodes 5, 5 into contact with and away from each other, the fixed side and movable side electrodes form a pair while maintaining airtightness of the vacuum vessel 4 from the center of each end plate 3. Bar 6,
In addition to introducing 6 relatively freely approaching and leaving,
The current flowing in the axial direction (vertical direction in FIG. 1) in the electrode rod 6 between the inner end of each electrode rod 6 and the back of each electrode 5 is changed to a loop current along the outer periphery of the back of the electrode 5. It is constructed by interposing coil bodies 7, 7 which generate an axial magnetic field. The coil body 7 is of the 1/3 turn type as shown in FIGS. 2 and 3, and the electrode rod 6
A cylindrical center conductor 8 with an appropriately small outer diameter, three arc-shaped first coils 9a, 9b, 9c arranged concentrically around the outer periphery of the center conductor 8, and three etc. on the outer periphery of the center conductor 8. The semi-longitudinal direction (second
The first arm 1 extends outward (left-right direction in the figure)
0a, 10b, 10c, and each first arm 10a,
Second coils 11a, 11b, 11c curve in an arc shape from the ends of the electrodes 10b, 10c in the same circumferential direction along the outer peripheral edge of the back of the electrode 5, and each second coil 11
a, 11b, 11c and the first coils 9a, 9
b, 9c to connect the first arms 10a, 10
second arms 12a, 12b, 12 extending in parallel in the same radial plane as b, 10c;
c, and is electrically and mechanically connected to the electrode rod 6 via the first coils 9a, 9b, and 9c, and electrically connected to the electrode 5 via the center conductor 8, and A recess 6a formed in the center of the end shaft
It is mechanically supported by the electrode rod 6 through a cylindrical resistance spacer 13 made of ceramic or high-resistance metal housed in the electrode rod 6, and is formed into a substantially ring-circular shape from an insulator such as ceramic or a high-resistance metal such as stainless steel. At the same time, the second coil 11 is
a, 11b, 11c, etc. are reinforced and supported. In addition, in FIG. 1, 15 is a bellows, 16,
17 is a shaft shield and a bellows shield for protecting the fixed side electrode rod 6 and bellows 15 from adhesion of metal vapor, etc. 18 is a nearly cylindrical main shield, and the middle part is connected to one of the sealing metal fittings 2. , 2 are supported by support fittings 19 held between them. Furthermore, in Figure 2, 13
A is a hole for venting gas during soldering with the electrode rod 6 and the like. The electrode 5 is made of pure chromium or a chromium alloy containing 10% (by weight) or less of a conductive metal such as copper or silver. Those made of pure chromium are formed by sintering chromium powder in a vacuum atmosphere or inert gas atmosphere, and those made of chromium alloy are formed by sintering chromium powder and copper or silver powder. Sintering in a vacuum atmosphere or inert gas atmosphere, or sintering chromium powder into porous form and infiltrating it with copper or silver, which has a lower melting point than chromium, in a vacuum atmosphere or inert gas atmosphere. It is something that is formed. FIG. 4 is a longitudinal cross-sectional view of a main part of another embodiment of the present invention, and in this embodiment, the electrode 5 is formed by one member formed in the shape of a hat-shaped disk, whereas in the embodiment described above, On the other hand, the disk-shaped contact 5a and this contact 5
The electrode 5'
The only difference is that the center conductor 8 of the coil body 7 is provided so as to be directly electrically connected to both. And the electrode 5' is
The contact 5a is made of a metal material such as pure chromium or a chromium alloy containing 10% or less of a conductive metal such as copper or silver, and the arc electrode 5b is made of a metal material with a vapor pressure slightly higher than that of the metal material of the contact 5a. a metal material that has a metal material and allows the arc to easily move from the contact point 5a;
For example, pure iron or stainless steel, a metal material whose main component is iron containing copper or silver is used. Note that the contact 5a made of pure chromium or a chromium alloy containing 10% or less of copper or silver is formed in the same manner as in the embodiment described above, and is made of iron containing copper or silver as a main component. The electrode 5b made of a metal material is formed by porously sintering iron or stainless steel powder in a vacuum atmosphere and infiltrating it with copper or silver. Here, when selecting the metal material of the cap-shaped disk-shaped electrode 5 and the electrode 5' consisting of the contact 5a and the arc electrode 5b, we first consider the cutting current value and 200KHz high frequency of various electrode materials such as iron-related materials and chromium. Characteristic tests such as shear cutting were conducted and the experimental results shown in Table 1 were obtained.

[Table] (Each value is the average value of three test pieces, contact resistance includes lead rod)
Therefore, although iron-based materials such as pure iron and stainless steel have a relatively small cutting current value and are capable of cutting commercial frequency current, they have a low ability to cut high frequency current. Poor welding resistance,
In addition, since the contact resistance is large, the electrode material, especially the electrode 5
Although pure chromium seems to be inappropriate as a material for the contact 5a of the electrode 5', pure chromium has almost the same characteristics as the contact 5a of the electrode 5 or 5', except for its relatively low ability to cut high frequency current. Is pleased. Next, a contact 5a is formed by combining the metal materials of the contact 5a and the arc electrode 5b in the electrode 5'.
A test was conducted to determine the ease with which the arc could be moved from the base, and the experimental results shown in Table 2 were obtained.

[Table] Therefore, it can be seen that depending on the combination of the metal materials of the contact 5a and the arc electrode 5b, there are cases in which it is easy for the arc to move and cases in which it is difficult to move the arc. After elucidating the basic characteristics of various metal materials as described above, we conducted a switching surge test under reactor load and found that conventional copper and copper alloys containing a few percent or less of bismuth or lead, etc. A surge occurs due to simultaneous three-phase shearing caused by multiple re-ignition surges, but pure iron, stainless steel, copper-tungsten alloys, pure chromium, and chromium alloys containing less than 10% copper do not re-ignite, but It was found that this did not lead to multiple re-ignitions and simultaneous three-phase failures, and did not generate excessive voltage surges. Therefore, the metal material for the contacts 5a of the electrodes 5 and 5' that satisfies the above-mentioned characteristics and can suppress the occurrence of multiple re-ignition surges and accompanying surges due to simultaneous rupture of three phases is as follows: , pure chromium,
It was found to be a chromium alloy containing less than 10% copper. In addition, since simultaneous three-phase shearing due to multiple re-ignition surges occurs immediately after contact opening, in other words, at the time of a very small gap between the contacts, pure chromium or A chromium alloy containing pure chromium and a conductive metal material with a lower melting point, such as copper or silver, is used for the arc electrode 5b of the electrode 5', as shown in Table 2.
Chromium-based materials such as pure chromium and chromium alloys are compatible with arc breakage (the arc moves easily), and metallic materials such as pure iron and stainless steel have slightly higher vapor pressure than chromium-based materials. It is sufficient to use a metal material whose main component is Incidentally, in Table 2, copper is also compatible, but copper is not preferable due to the generation of eddy current. As described above, the present invention introduces a pair of disk-shaped electrodes into a vacuum container on the axis thereof so that they can approach and separate from each other, and the inner end of each electrode rod. In a vacuum shield and disconnector in which a coil body is interposed between the electrode and a coil body that generates an axial magnetic field, the electrode is made of pure chromium or 10%
Since it is made of a medium vapor pressure metal material such as a chromium alloy containing conductive metals such as copper or silver, it can withstand multiple recurrences without impairing the conditions required for a vacuum shield or disconnector electrode. It is possible to suppress arc surges and surges caused by three-phase simultaneous disconnections. Therefore, there is no need to include a surge absorber in the circuit as in conventional systems, and the space of the entire field closing device can be reduced, and the reliability of the circuit can be increased.
Moreover, it is possible to reduce the cost of the opening/closing device. In addition, in a vertical magnetic field type electrode consisting of a contact point and an arc electrode, the contact point is made of a medium vapor pressure metal material such as pure chromium or a chromium alloy containing 10% or less of a conductive metal such as copper or silver. At the same time, the arc electrode is made of a ferrous material such as pure iron, stainless steel, or a chromium-based material containing copper or silver, which has a vapor pressure slightly higher than that of the chromium-based material that forms the contact, and the arc Since it is made of a metal material whose main component is iron, which is easier to move, it is possible to meet the conditions that an electrode should meet by using a contact in the case of a small current, and a contact and an arc electrode in the case of a large current. It is possible to suppress multiple re-ignition surges and accompanying surges due to three-phase simultaneous rupture without causing any damage. Therefore, effects similar to those described above can be obtained from small current to large current.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a vacuum shield disconnector according to the present invention, FIGS. 2 and 3 are a longitudinal cross-sectional view and a plan view of the main parts of the present invention, respectively, and FIG. 4 is a longitudinal cross-sectional view of the main parts of the present invention. FIG. 7 is a vertical cross-sectional view of another embodiment. 4... Vacuum container, 5, 5'... Electrode, 5a...
Contact, 5b... Arc electrode, 6... Electrode rod, 7...
...Coil body.

Claims (1)

[Claims] 1. A disk-shaped 1 on the axis of the vacuum container.
A vacuum created by introducing a pair of electrode rods so as to be able to approach and separate them relatively, and interposing a coil body that generates an axial magnetic field between the inner end of each electrode rod and the electrode. A vacuum breaker, characterized in that the electrode is made of pure chromium or a chromium alloy metal material containing 10% or less of a conductive metal. 2. A pair of electrodes consisting of a disc-shaped contact point and a ring-disc-shaped arc electrode arranged around the contact point in such a way that the contact point protrudes on the axis of the vacuum vessel is brought into contact with and separated from the pair. In a vacuum shield disconnector, in which two electrode rods are introduced so as to be able to approach and separate from each other, and a coil body is interposed between the inner end of each electrode rod and the electrode to generate an axial magnetic field.
The contacts of the electrodes are made of pure chromium or 10% of this.
A vacuum shield disconnector characterized in that it is made of a metal material of a chromium alloy containing conductive metal of % or less, and its arc electrode is made of pure iron or a metal material containing pure iron as a main component.