JP3681962B2 - Pressure measuring element for vacuum insulated switchgear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum insulated switchgear provided with a measuring device for pressure detection.
[0002]
[Prior art]
Breaking performance and withstand voltage performance of the vacuum valve is rapidly reduced when the pressure is below 10- ⁴ Torr. Causes of fluctuations in the vacuum pressure include not only vacuum leakage due to cracking, but also the release of gas molecules adsorbed on the metal / insulator, and the permeation of atmospheric gas. When the vacuum vessel is enlarged with the increase in the voltage of the vacuum valve, the release of the adsorbed gas and the permeation of the atmospheric gas cannot be ignored. Further, in a structure in which a circuit breaker, a disconnecting switch, and a grounding switch are integrated in a single vacuum valve as in the insulated switchgear described in JP-A-9-249076, the load or the switchgear main body is maintained and inspected. In order to ensure the safety of the operator, it is desired to add a vacuum pressure check function during operation or a function for constantly monitoring pressure.
[0003]
Up to now, vacuum valves equipped with pressure detectors are equipped with ionization vacuum gauges, those that detect the pressure by applying a voltage to a small gap in the vacuum vessel, and those that have magnetron terminals Etc. are known. In addition, in the vacuum insulated switchgear disclosed in Japanese Patent Laid-Open No. 11-329174, a pressure measuring element protruding outside from the grounded vacuum vessel is attached, and the insulation for insulation between the outer electrode and the coaxial electrode constituting the protruding portion is directly joined. Has been. In this publication, the output of the pressure measuring element is enhanced by actively using the metallized surface of the insulator as an electron supply source.
[0004]
[Problems to be solved by the invention]
In the above prior art, the pipe-shaped outer electrode and the ceramic are directly joined. In brazing in a vacuum furnace, a brazing material is inserted between the outer electrode and the ceramic and heated to a high temperature to melt the brazing material and join them together. Since the thermal expansion coefficients of the joined members are different, if the temperature is returned to room temperature after brazing, there is a risk that residual thermal stress is generated and the ceramic is damaged. Accordingly, a copper material having high ductility must be used for the outer electrode. When copper-based pipes are used, (1) the vacuum vessel is preferably made of stainless steel because of its withstand voltage performance. Stainless steel and copper can be joined only by brazing, and the number of brazing increases. (2) Problems such as corrosion and aging occur.
[0005]
An object of the present invention is to provide a pressure measuring element of a vacuum insulated switchgear in which a member made of the same material as that of a vacuum vessel can be used for an outer electrode and pressure measurement sensitivity is improved.
[0006]
[Means for Solving the Problems]
The present invention attaches an outer electrode of the same material as the vacuum vessel to the vacuum vessel, absorbs the difference in thermal expansion coefficient between the outer electrode and the insulating portion, and emits electrons between the outer electrode and the insulating portion. It is characterized by joining with a brazing material via
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described in detail with reference to FIGS.
[0008]
A vacuum valve 1 of the vacuum insulated switchgear shown in FIG. 1 includes a vacuum vessel 2 and a pressure measuring terminal 30 attached to the vacuum vessel 2. The grounded stainless steel vacuum vessel 2 is vacuum-sealed by two bushings 3 and 4, an insulating rod 9, a bellows 10, and a pressure measuring terminal 30 around it.
[0009]
A fixed electrode 5 and a movable electrode 6 that can be freely contacted and separated are arranged inside the vacuum vessel 2. The movable electrode 6 is brought into contact with and separated from the fixed electrode 5 by an operating mechanism provided outside. Is inserted into and cut off from the fixed electrode 5. The fixed electrode 5 is fixed to the fixed conductor 12 that penetrates the bushing 3, and the flexible conductor 8 is connected between the movable electrode 13 that penetrates the bushing 4 and the movable electrode 6.
[0010]
In the vacuum valve 1 of the present embodiment, current flows through a path of the fixed side conductor 12 -the fixed electrode 5 -the movable electrode 6 -the flexible conductor 8 -the movable side conductor 13. The movable electrode 6 is connected to an insulating rod 9, and the insulating rod 9 is fixed to the vacuum vessel 2 through a bellows 10. The arc shield 11 is for avoiding a ground fault that occurs when the arc A touches the vacuum vessel 2 at the time of interruption.
[0011]
Next, the operation of the vacuum valve 1 will be described. The vacuum valve 1 is driven by an operating mechanism (not shown) to drive the insulating rod 9 upward, and the movable electrode 6 is brought into contact with the fixed electrode 5 for charging. Further, the insulating rod 9 is driven in the downward direction, and the movable electrode 6 is separated from the fixed electrode 5 to be cut off.
[0012]
The pressure in the vacuum vessel 2 is measured by a pressure measurement terminal 30. The pressure measurement terminal 30 is a magnetron type measurement terminal shown in FIGS. 2A and 2B, and includes a coaxial electrode 38 and a permanent magnet 37 disposed around the coaxial electrode 38. The permanent magnet 37 may be a magnetic field generating coil. The permanent magnet 37 is not always provided, but may be attached only at the time of pressure measurement (maintenance / inspection).
[0013]
The coaxial electrode 38 includes a cylindrical outer electrode 33, an inner electrode 34 penetrating the cylindrical outer electrode 33, an insulating portion 31 made of an insulating member that insulates both, and a metal block 32 of a metal member sandwiched between the insulating portion 31 and the outer electrode 33. Each member is brazed and joined in a high-temperature vacuum furnace. The installation location of the brazing material 35 is as shown in FIG.
[0014]
The cylindrical outer electrode 33 communicates with the inside of the vacuum vessel 2 in the vacuum vessel 2, and the insulating portion 31 is joined to the open end on one end side by a brazing material 35, for example, Ag brazing. The electrode 34 penetrates. The outer electrode 33 is made of stainless steel made of the same material as the vacuum vessel 2 and is attached to the vacuum vessel 2 by brazing or welding. When the vacuum vessel 2 is produced, a cylindrical projection is formed on a part of the vacuum vessel 2. May be integrally molded, and this protrusion may be used as the outer electrode 33.
[0015]
The metal block 32 and the center electrode 34 have higher electron emission performance than the outer electrode 33 and are made of a highly ductile material such as Cu or CuAg to prevent the insulating portion 31 from being damaged by residual stress after brazing. . A member that can withstand high temperature brazing, such as ceramic, is used for the insulating portion 31. As shown in FIG. 2B, the end portion of the metal block 32 is provided with a protruding portion 32 a extending to the side where the outer electrode 33 and the inner electrode 34 face each other, and a through hole 32 b penetrating the metal block 32. A corner 32c is formed at the end of the protrusion 32a facing the through hole 32b.
[0016]
The operation of the pressure measurement terminal 30 will be described. A DC voltage is applied between the outer electrode 33 and the inner electrode 34 by the power supply circuit 40. The polarity of the applied voltage is such that the inner electrode 34 is an anode and the outer electrode 33 and the metal block 33 are cathodes. The applied voltage may be an alternating voltage or a pulsed voltage.
[0017]
The electrons e emitted from the metal block 32 receive a Lorentz force by the electric field E and the magnetic field B applied by the permanent magnet 37 and rotate around the inner electrode 34. The rotating electrons e collide and ionize the residual gas G, and the generated cations I flow into the outer electrode 33. Since the ion current j depends on the residual gas amount, that is, the pressure, the pressure can be measured by the voltage V generated across the resistor R.
[0018]
When the pressure is constantly monitored, the relay may be operated by the voltage V across the resistor R to turn on the alarm lamp or generate a warning sound. As shown in the graph of FIG. 3, interruption performance and insulation performance of the vacuum valve 1 is rapidly reduced when the pressure P becomes equal to or higher than 10- ⁴ Torr. Pressure measuring terminal 30 indicated in the present embodiment is identifiable to about 10- ⁷ Torr, it is effective enough as a pressure monitor.
[0019]
Next, the effect of the present embodiment will be described. In this embodiment, a metal block 32 having a greater ductility than the material of the outer electrode 33 and the insulating part 31 is inserted between the outer electrode 33 and the insulating part 31. This metal block 32 is inserted between the outer electrode 33 made of the same material as the vacuum vessel 2 and the insulating portion 31, and the residual thermal stress due to the difference in thermal expansion coefficient between the outer electrode 33 and the insulating portion 31 after brazing. Is absorbed, so that damage to the insulating portion 31 can be avoided.
[0020]
Further, since the outer electrode 33 can be made of stainless steel made of the same material as the vacuum vessel 2 by inserting the metal block 32, secular change due to corrosion is suppressed, and reliability is improved. When the outer electrode 33 can be made of stainless steel of the same material as the vacuum vessel 2, it can be attached by welding, and no special employment is required when brazing in a high temperature vacuum furnace, and brazing in a high temperature vacuum furnace. Work can be simplified. Further, if the vacuum container 2 provided with a protruding portion in part is manufactured, this protruding portion can be used as an outer electrode, and the cost is further reduced.
[0021]
Furthermore, since the metal block 32 is connected to the outer electrode 33, it becomes a cathode. When a DC voltage is applied between the outer electrode 33 and the metal block 32 and the inner electrode 34, electrons e are emitted from the metal block 32, and the electrons e generate a Lorentz force by the electric field E and the magnetic field B applied by the permanent magnet 37. Receiving and rotating around the inner electrode 34. The rotating electrons e collide and ionize the residual gas G, and the generated cations I flow into the outer electrode 33. Since the ion current j depends on the residual gas amount, that is, the pressure, the pressure can be measured by the voltage V generated across the resistor R.
[0022]
In this embodiment, since the distance between the metal block 32 and the inner electrode 34 is narrower than the inner diameter of the outer electrode 33, the electric field concentrates on the corner 32c facing the inner electrode 34 of the metal block 32, and more electrons e are emitted. Will flourish. Therefore, only became popular amount that the number of times that the electrons e collide ionized residual gas G is provided a corner 32c, the sensitivity of the ion current j is improved, can be identified up to about 10- ⁷ Torr in the graph of FIG. 3 Then, it became difficult to monitor the pressure. Furthermore, since the metal block 32 uses a copper-based material having a small work function, it is possible to supply a sufficient pressure electron for pressure measurement, and to provide a reliable pressure measurement terminal with improved output stability and sensitivity. In addition, the metal block 32 formed a protrusion 32a, and the protrusion 32a further increased the emission of electrons e, improved the sensitivity of the ionic current, and measured the pressure.
[0023]
【The invention's effect】
As described above, according to the present invention, the outer electrode is made of the same material as that of the vacuum vessel, and the secular change due to corrosion is suppressed. .
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a vacuum valve and a pressure measurement terminal according to an embodiment of the present invention.
FIG. 2 is a side sectional view of a pressure measurement terminal attached to the vacuum valve of FIG.
FIG. 3 is a characteristic diagram showing the relationship between pressure P and insulation performance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum valve, 2 ... Vacuum container, 3, 4 ... Bushing, 5 ... Fixed electrode, 6 ... Movable electrode, 9 ... Insulating rod, 10 ... Bellows, 15 ... Hole, 16 ... Insulating cylinder, 20 ... Main shaft, 21 ... Insulating part, 30 ... pressure measuring terminal, 31 ... insulating part, 32 ... metal block, 33 ... outer electrode, 34 ... inner electrode, 35 ... brazing material, 36 ... coil, 37 ... permanent magnet, 38 ... coaxial electrode, 40 ... Power circuit 41 ... Meger 50 ... Insulator B ... Magnetic field E ... Electric field P ... Pressure R ... Resistance V ... Voltage e ... Electron

Claims (5)

A fixed electrode is disposed in a grounded vacuum container, a movable electrode that is in contact with and away from the fixed electrode is disposed, and a tubular outer electrode that communicates with the inside of the vacuum container and has an open end on one end side is disposed in the vacuum container. A magnetic field generating part for generating a magnetic field is arranged on the outer peripheral side of the outer electrode, an insulating part is joined to the open end of the outer electrode with a brazing material, penetrates the insulating part, and the inner part of the outer electrode An inner electrode is arranged facing the peripheral surface, a voltage is applied between the inner electrode and the outer electrode, electrons generated from the outer electrode are rotated by the magnetic field, and the electrons are left in the residual gas in the vacuum vessel. In an element for measuring the pressure in the vacuum vessel by ion current generated by impact ionization, the outer electrode is made of the same material as the vacuum vessel and brazed between the outer electrode and the insulating portion. To absorb residual thermal stress And, and the pressure measuring element of the vacuum insulated switchgear, characterized by inserting a metal having high block of emission performance of the electrons than the outer electrode. The pressure measuring element of a vacuum insulated switchgear according to claim 1, wherein the metal block is a member that absorbs expansion and contraction of the outer electrode and the insulating portion during brazing and emits electrons. The pressure measuring element of a vacuum insulated switchgear according to claim 1, wherein the metal block is oxygen-free copper. The metal block is provided with a protrusion extending on the side where the outer electrode and the inner electrode face each other, and a through hole through which the inner electrode penetrates the protrusion and the metal block. The pressure measuring element of the vacuum insulated switchgear according to claim 1. The pressure measuring element of the vacuum insulated switchgear according to claim 1, wherein stainless steel is used for the vacuum vessel and the outer electrode.

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