JP4218935B2 - Method for manufacturing voltage nonlinear resistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a voltage non-linear resistor which is mainly composed of zinc oxide and is used as an internal element of an overvoltage protection device.
[0002]
[Prior art]
Generally, in a power system, when a circuit breaker provided on a power transmission line is opened or closed, or when a lightning discharge occurs, an overvoltage such as a switching surge or a lightning impulse is generated, causing dielectric breakdown to electrical equipment connected to the system. May cause damage. For this reason, in order to protect electrical equipment or the system from overvoltage, when the overvoltage exceeds a certain limit, it is discharged and the system is quickly restored to the normal state by interrupting the follow-up in a short time. Overvoltage protection devices such as lightning arresters and surge absorbers are used. A voltage nonlinear resistor is mainly used as an internal element of the overvoltage protection device.
[0003]
Here, the voltage non-linear resistor is a resistor having a voltage-current non-linear characteristic that exhibits a substantially insulating characteristic at a normal voltage and has a relatively low resistance when an overvoltage is applied to discharge the overvoltage. It is. Such voltage non-linear resistors are generally made of ceramics, that is, sintered bodies.
[0004]
Conventionally, as shown in FIG. 9, this type of voltage non-linear resistor is composed of zinc oxide (ZnO) as a main component and additives for obtaining non-linear resistance characteristics such as bismuth (Bi), antimony (Sb), Discs made by mixing, granulating, molding, sintering and adding metal oxides such as cobalt (Co), manganese (Mn), chromium (Cr), nickel (Ni), silicon (Si) The sintered body element 4 is formed by applying the electrode 3 after polishing the end face 2 of the disk 1. A side high resistance layer 5 is formed on the side surface of the sintered body element 4 to prevent flashover when an overvoltage is applied.
The disk-shaped sintered body elements 4 formed in this way are stacked so that a plurality of electrodes are in contact with each other according to the discharge capacity, thereby constituting an overvoltage protection device.
[0005]
Further, in order to further prevent flashover in such a disk-shaped sintered body element 4, for example, Japanese Patent Publication No. 5-74921, Japanese Patent Application Laid-Open No. 8-195303, Japanese Patent Application Laid-Open No. 11-186006. As disclosed in publications and the like, the outer peripheral portion of the end surface 2 is arranged such that the outer edge of the electrode 3 formed on the end surface 2 of the sintered body element 4 does not cover the edge of the end surface 2 of the sintered body element 4. In general, the ring-shaped electrode non-forming portion 6 having a dimension of 0.01 to 1.0 mm from the edge of the electrode 3 is formed.
[0006]
[Problems to be solved by the invention]
In recent years, the growth of power demand and the development of an advanced information society are remarkable, and there is a strong demand for stable, inexpensive and reliable power supply. On the other hand, due to the lack of installation space for receiving and transforming equipment due to the lack of land in urban areas, there is an increasing demand for miniaturization of transmission and transformation equipment in addition to high reliability. In order to meet this demand, recently, the voltage value per unit thickness of the voltage nonlinear resistor is increased to keep the height dimension low, and further the energy absorption capacity is improved. Miniaturization is being promoted.
Of course, even in a downsized overvoltage protection device, a stable operating state for a long period of use is required.
[0007]
As described above, in the conventional voltage non-linear resistor, as shown in FIG. 9, when the electrode 3 is formed on the sintered body element 4, the outer peripheral portion and the side surface of the end face 2 of the sintered body element 4 are cured at room temperature. Masking 7 is applied with a rubber mask made of resin or the like, thereby forming a ring-shaped electrode non-forming portion 6 on the outer peripheral portion.
[0008]
However, in the conventional voltage non-linear resistor having such a configuration, a current flows through the electrode 3 forming portion when a current is applied, but a ring-like shape formed on the outer peripheral portion of the end face 2 of the sintered body element 4. Since no current flows through the electrode non-forming portion 6, a temperature difference is generated between the electrode 3 forming portion and the electrode non-forming portion 6. As a result, thermal stress due to this temperature difference is generated, and the sintered body element 4 is cracked and leads to breakdown. As a result, discharge between electrode layers and generation of SF6 gas thereby result in voltage nonlinear resistance. There was a problem that the reliability of the overvoltage protection ability of the body was lowered.
[0009]
Therefore, it is difficult to meet the protection capability against surges such as switching surges, lightning impulses and overvoltages required when the voltage non-linear resistor is downsized by increasing the voltage or reducing the diameter per unit thickness of the sintered body element 4. Met.
[0010]
As a means for solving such a problem, it is conceivable to increase the electrode formation area as much as possible. However, if an attempt is made to form the electrode 3 to the limit of 5 parts of the side high resistance layer 5 using a mask such as that used in the manufacture of a conventional voltage non-linear resistor, the result is to the side of the side high resistance layer 5 as a result. Since the electrode material is attached, it is difficult to increase the electrode formation area as much as possible. It is also conceivable to attach an adhesive tape or the like to the side surface of the sintered body element 4 to perform masking to prevent the electrode material from adhering to the side high resistance layer 5. There is a problem that the production process and labor are reduced and the production efficiency is lowered.
[0011]
The present invention solves the above problems, prevents the electrode material from adhering to the side high resistance layer without reducing the production efficiency, maximizes the electrode formation area, and is excellent in normal use conditions. It is an object of the present invention to provide a method for manufacturing a voltage non-linear resistor that realizes discharge energy withstand characteristics and electric charging life characteristics, and has improved protection against surges such as switching surges, lightning impulses and overvoltages.
[0012]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is directed to an end face of a disk-shaped sintered body element mainly composed of zinc oxide and a ring-shaped electrode non-formation portion along the outer peripheral portion of the end face. When forming the electrode by thermal spraying to form a thermal spraying , the end face of the sintered body element is sprayed almost at right angles to the end face without masking, and the spraying direction and the dust collecting direction for collecting fume and the like are set. In the method of manufacturing a voltage non-linear resistor in the same direction, while the sintered body element is rotated, the thermal spraying proceeds from the outer periphery of the end face of the sintered body element toward the center, and the aluminum wire used for arc spraying The operation of the servo motor for feeding is slow-started at the start of spraying, and at the end of spraying, the aluminum wire is returned 3 mm to form an electrode .
[0015]
According to the present invention, will promote spray from the outer peripheral portion of the end surface of the sintered body element, to terminate the spraying in the center, the side surface of the outer part directly sintered body from the center of the sprayed particles emitted radially No gap is formed in the electrode at the outer peripheral portion of the sintered body element.
[0017]
According to the present invention, or, when spraying begins, gradually into contact with aluminum wire, sputtering is unlikely to occur.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. First, zinc oxide (ZnO), manganese dioxide (MnO ₂ ), cobalt oxide (Co ₂ O ₃ ), for example, 0.5 mol%, bismuth oxide (Bi ₂ O ₃ ), antimony oxide (Sb ₂ O ₃ ), For example, 1 mol% of nickel oxide (NiO) is added. Next, the raw material is mixed with water, an organic dispersant, and binders in a mixing apparatus, and the mixture is spray-granulated using, for example, a spray dryer. These granulated powders are put into a mold and pressed to form a disk 1 having a diameter of 100 mm and a thickness of 30 mm as shown in FIG. 1, and this molded body is fired at 1200 ° C., for example.
[0019]
Next, for example, an alumina-based inorganic insulator is applied to the side surface of the fired sintered body element 4 and baked at a temperature of 400 ° C., for example, to form the side surface high resistance layer 5. After polishing the upper and lower end surfaces 2 of the sintered body element 4 on which the side high resistance layer 5 is formed, the electrode 3 is formed on the polished surface by thermal spraying using a thermal spray gun 8 to manufacture a voltage nonlinear resistor.
[0020]
Here, when the electrode 3 is formed by thermal spraying, the characteristics of the example in which the sintered body element 4 is masked as in the conventional method and the two types of methods in which the masking is not performed as in the present invention are described. Explain the results of the test.
[0021]
First, three pieces of the sintered body element 4 manufactured as described above are stacked to form a voltage non-linear resistor, and the 2 ms rectangular wave discharge energy is gradually increased from 200 J / cm ³ to the sintered body element 4. While being applied, a destructive test was conducted until one of the three sintered body elements 4 was electrically destroyed. At this time, the maximum amount of discharge energy absorbed until the sintered body element 4 was destroyed was defined as discharge energy resistance (J / cm ³ ). In addition, a 10 p discharge energy withstand test was performed for each electrode forming condition and electrode-shaped sintered body element.
[0022]
FIG. 2 shows the results of a discharge energy resistance test when various thermal sprays forming the electrode 3 of the sintered body element 4 are changed. In FIG. 2, the electrode forming method A shows the discharge energy withstand characteristics in the case of the sintered body element subjected to the thermal spraying with masking, and B represents the sintered body element subjected to the thermal spraying without masking.
[0023]
FIG. 3 shows a voltage non-linear resistor formed by laminating three sintered body elements 4, and a rectangular wave discharge energy of 180 J / cm ³ in the sintered body element 4 in an atmosphere of 80 ° C. in SF ₆ gas. Is applied to the sintered body element 4 at room temperature for 1000 hours, and the resistance leakage current (IR (0h )) And a resistance current (IR (1000 h)) after 1000 hours of power application, and a characteristic diagram in which the electric life characteristics are evaluated by IR (1000 h) / IR (0 h).
[0024]
In FIG. 3, the electrode forming method C shows the characteristics in the case of a sintered body element subjected to thermal spraying with masking, and D represents the characteristics in the case of a sintered body element subjected to thermal spraying without masking.
As is apparent from the test results of FIGS. 2 and 3, the discharge element withstand energy characteristics and the electric charge life characteristics are remarkably excellent in the sintered body element formed without masking in the electrode formation by thermal spraying.
[0025]
The reason why the sintered body element without masking in this electrode formation exhibits excellent characteristics is that when the electrode is formed using a mask, the electrode material attached to the mask when the mask is removed is together. Partly peels off from the upper surface portion of the sintered body element. Therefore, a gap is generated at the end of the electrode, and when energy is applied, a thermal stress is locally generated, leading to destruction. When electrode formation is performed without masking, it is considered that the end portions are not peeled off and are not easily broken, which makes it difficult to cause discharge between the electrode layers and local electric field concentration.
[0026]
For these reasons, as shown in FIG. 2 and FIG. 3, by performing electrode formation of the sintered body element in the voltage non-linear resistor without masking, excellent discharge energy withstand characteristics and electric charging life characteristics A voltage non-linear resistor is obtained.
[0027]
Next, in the figures shown in FIGS. 4 to 8, in the voltage non-linear resistor manufactured by the above method, the sintered body element 4 is sprayed without masking to form an electrode, and the electrode 3 is formed. It is a figure which shows the result of the discharge energy tolerance test and the electrical charging lifetime characteristic test at the time of changing various conditions at the time of the thermal spraying.
[0028]
FIG. 4 shows a voltage non-linear resistor that is always sprayed at right angles from the spray gun 8 to the end face 2 of the sintered body 4 when the electrode is formed by spraying without masking, and the spray gun 8. It is the result of the discharge energy tolerance test with the voltage non-linear resistance body which was arranged diagonally with respect to the end surface 2 of the sintered compact element 4, and sprayed diagonally. In FIG. 4, the spray angle E indicates the characteristics when sprayed at right angles, and the spray angle F indicates the characteristics when sprayed obliquely.
[0029]
As apparent from FIG. 4, the spray particles emitted from the spray gun 8 are scattered in a radial manner because the metal wire is short-circuited and blown off by the air pressure due to its structure. By spraying at right angles to the end face 2 of the sintered body element 4 at all times, the spray particles released radially do not wrap around the side face of the sintered body element 4 and can prevent adhesion. On the other hand, by performing the oblique spraying, the sprayed particles adhere to the side surface of the sintered body element 4, and the insulating distance of the side surface high resistance layer 5 is shortened. When spraying at right angles to the end face 2 of the sintered body element 4, excellent discharge energy resistance is shown, but when oblique spraying is performed, the discharge energy resistance is low.
[0030]
In FIG. 4, only the discharge energy withstand test results are shown. However, with regard to the chargeable life characteristics, good characteristics are obtained in the voltage non-linear resistance body sprayed at right angles to the end face 2 of the sintered body element 4. It was.
[0031]
As described above, in forming the electrode of the sintered body element 4, the spray gun 8 is always perpendicular to the end face 2 of the sintered body element 4, so that the voltage non-reliability of the excellent discharge energy withstand characteristics and the charging life characteristics is improved. A linear resistor is obtained.
[0032]
FIG. 5 shows the results of a discharge energy withstand test of a voltage non-linear resistor when the spraying direction of the spray gun 8 and the direction of collecting dust and fumes not adhering to the sintered body element 4 are changed. FIG. In FIG. 5, the dust collection direction G shows the characteristics when the spraying direction and the dust collection direction are the same, and the dust collection direction H shows the characteristics when the spraying direction and the dust collection direction are different.
[0033]
As is apparent from FIG. 5, the spray particles that do not adhere to the sintered body element 4 are collected and processed so as not to stay in the spray chamber. The spray particles are exposed to air, become solid, and usually collect dust, but have a property of adhering to the closest substance in a molten state. Therefore, when the spraying direction and the wind flow of the dust collection are not the same, the sprayed particles adhere to the side surface of the sintered body element 4 while floating. When the spraying direction and the dust collection direction are the same direction, the dust is collected directly without floating, so that there is no wraparound to the side surface of the sintered body element 4 and adhesion can be prevented. Therefore, when the spraying direction and the dust collection direction are the same, excellent discharge energy resistance is shown, but when spraying is performed in different directions, the discharge energy resistance is low.
[0034]
In FIG. 5, only the discharge energy withstand test results are shown, but with regard to the electric charge life characteristics, good characteristics were obtained in the voltage non-linear resistor in which the spraying direction and the dust collection direction were the same. .
[0035]
As described above, in forming the electrode of the voltage non-linear resistor, by making the spraying direction of the sprayed particles scattered from the spray gun the same as the direction of dust collection, the voltage of the excellent discharge energy withstand characteristics and the charging life characteristics can be obtained. A non-linear resistor is obtained.
[0036]
FIG. 6 shows a result of conducting a discharge energy resistance test when the sintered body element 4 is rotated and the electrode is formed by the trajectory of the spray gun 8 and when the sintered body element 4 is fixed and the electrode is formed. FIG. In FIG. 6, the thermal spray method I shows the characteristics when the sintered body element 4 is rotated, and the thermal spray method J shows the characteristics when the sintered body element 4 is fixed.
[0037]
As apparent from FIG. 6, in the method in which the sintered body element 4 is rotated and the electrode is formed by the trajectory of the spray gun 8, the spraying is advanced from the outer peripheral portion and the spraying is terminated at the central portion. For this reason, since the portion outside the center of the spray particles that are radially emitted is not directly sprayed onto the side surface of the sintered body 4, no gap is formed in the electrode at the outer peripheral portion of the end surface 2 of the sintered body element 4. However, when the sintered body element 4 is fixed and thermal spraying is performed, it is very difficult to move the spray gun 8 in accordance with the area of the sintered body element 4, and it moves in a spiral or square shape. There is a need to. Therefore, the thermal spray particles sprayed over the outer peripheral portion of the end face 2 of the sintered body element 4 adhere to the side surface of the sintered body element 4.
[0038]
In general, when the area of the electrode 3 of the sintered body element 4 is larger than the sprayed area released from the spray gun 8, it is necessary to spray the spray gun by moving the area of the electrode 3 of the sintered body element 4. However, when the thermal spray gun 8 is moved at a high speed, connection lines such as aluminum wires, power wires, and signal wires are obstructive and cannot operate properly. Further, the robot for moving the heavy spray gun 8 at a high speed becomes larger and requires a large installation space. Therefore, the installation space can be reduced by making the operating distance of the thermal spray gun 8 as small as possible, rotating the sintered body element 4 and performing thermal spraying along the trajectory. When spraying is performed by rotating the sintered body element 4, excellent discharge energy resistance is shown, but when the sintered body element 4 is fixed and spraying is performed, the discharge energy resistance is low.
[0039]
In FIG. 6, only the discharge energy withstand test results are shown, but with regard to the electric charge life characteristics, good characteristics were obtained in the voltage non-linear resistor which was sprayed by rotating the sintered body element 4.
[0040]
Thus, in forming the electrode of the voltage non-linear resistor, the sintered body element 4 is rotated and sprayed along the trajectory of the thermal spray gun 8, whereby the voltage non-linear resistance having excellent discharge energy withstand characteristics and electric charging life characteristics. The body is obtained.
[0041]
FIG. 7 is a view showing an example in which an adsorption jig is installed at the lower portion to prevent the dropout when the sintered body element 4 is rotated. In the case where the rotating mechanism of the sintered body element 4 is provided, since the thermal spraying is performed while the sintered body element 4 is rotated, the sintered body element 4 is detached from the pedestal 9 by the centrifugal force, and the electrode is attached to the side surface. There is a risk that it cannot be formed. For this reason, the sintered body element 4 is attracted to the base 9 and is rotated to prevent the sintered body element 4 from falling off and to form a stable electrode. As an example, an O-ring 10 is provided in accordance with the shape of the sintered body element 4 and is adsorbed by a vacuum device (not shown).
[0042]
Next, in FIG. 8, the wire feed K is manufactured by causing the servo motor that feeds the aluminum wire in aluminum spraying to slow start at the start of spraying, returning 3 mm at the end of spraying, and forming an electrode. The sintered body element 4 and the line feed L are respectively diagrams showing the characteristics in the case of the sintered body element 4 in which the electrode is formed without controlling the line feed.
[0043]
As is apparent from FIG. 8, it can be seen that the sintered body element 4 in which the wire feed control at the time of thermal spraying is performed and the electrode 3 is formed exhibits excellent discharge energy withstand characteristics. In the wire feed K, a voltage is instantaneously applied at the start of spraying, and sputtering is likely to occur when short-circuiting is performed. Sputtering is a process in which a voltage is applied and the aluminum wire is melted by contact, but at that time, the aluminum wire is thermally sprayed without being completely melted. Therefore, in order to make it difficult for spatter to occur, it is slow-started (slow feed), and the aluminum wire is gradually brought into contact. In addition, when spraying is finished, it is surely performed by returning 3 mm. In the line feed L, spatter is generated without the control of the line feed, an aluminum thickness of about 1 mm is placed on the electrode thickness of 100 μm, and a gap occurs between the electrodes during the discharge withstand energy test, Current concentration occurs and the withstand characteristics are lowered. In FIG. 9, only the discharge energy withstand test results are shown, but good characteristics were also obtained in the voltage nonlinear resistor in which the line feed was controlled during electrode formation.
[0044]
As described above, in the formation of the electrode of the sintered body element 4 constituting the voltage non-linear resistor, by controlling the wire feed, a voltage non-linear resistor having excellent discharge energy withstand characteristics and charging life characteristics can be obtained. It is done.
[0045]
【The invention's effect】
As described above, according to the present invention, thermal spraying is performed so that a ring-shaped electrode non-formation portion is formed along the outer peripheral portion of the end face on the end face of the disk-shaped sintered body element mainly composed of zinc oxide. In the method of manufacturing a voltage non-linear resistor in which electrodes are formed by the above method, the end face of the sintered body element is sprayed at a substantially right angle with respect to the end face without masking. Prevents the electrode material from adhering to the high-resistance layer, maximizes the electrode formation area, achieves excellent discharge energy withstand characteristics and charging life characteristics under normal use conditions, and switching surge and lightning impulse And a method for manufacturing a voltage non-linear resistor with improved protection against surges such as overvoltage. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a voltage nonlinear resistor manufactured according to an embodiment of the present invention.
FIG. 2 is a graph showing discharge energy resistance characteristics of a voltage nonlinear resistor according to the present invention and a conventional voltage nonlinear resistor.
FIG. 3 is a graph showing a voltage-life characteristic of a voltage nonlinear resistor according to the present invention and a conventional voltage nonlinear resistor.
FIG. 4 is a graph showing the relationship between the angle of a thermal spray gun forming an electrode and the discharge energy withstand characteristics.
FIG. 5 is a graph showing discharge energy withstand characteristics in which electrodes are formed by changing spray particles discharged from a spray gun and a dust collection direction.
FIG. 6 is a graph showing the relationship between the thermal spray trajectory and the discharge energy withstand characteristics.
FIG. 7 is a cross-sectional view of a suction jig used in the manufacturing method of the present invention.
FIG. 8 is a graph showing the relationship between line feed control and discharge energy withstand characteristics.
FIG. 9 is a cross-sectional view showing a conventional method for manufacturing a voltage nonlinear resistor by masking.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Disk 2, 2 End face, 3 ... Electrode, 4 ... Sintered body element, 5 ... Side high resistance layer, 6 ... Electrode non-formation part , 7 ... Masking , 8 ... Thermal spray gun, 9 ... Base, 10 ... O ring.

Claims (1)

When forming an electrode by thermal spraying so as to form a ring-shaped electrode non-formation part along the outer peripheral part of the end face on the end face of the disk-like sintered body element mainly composed of zinc oxide , the sintered body In the method of manufacturing a voltage non-linear resistor in which the end face of the element is sprayed almost at right angles to the end face without masking, and the spraying direction and the dust collecting direction for collecting fume and the like are in the same direction ,
While rotating the sintered body element, the thermal spraying proceeds from the outer periphery of the end face of the sintered body element toward the center, and the servo motor that sends the aluminum wire used for arc spraying is started slowly at the start of spraying. Then, at the end of spraying, the electrode is formed by returning the aluminum wire by 3 mm, and the method for producing a voltage non-linear resistor.

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