JPH06188105A - Manufacture of non-linear resistor - Google Patents

Abstract

PURPOSE:To provide a nonlinear resistor of high power and high discharging resistance by applying aramid resin onto side faces of a sintered body and then backing it to form high-resistance layers. CONSTITUTION:A compact that is mainly formed of ZnO and is formed in the shape of a disc is burned in the air to remove an organic binder from the compact. After that, the compact is burned at high temperature to make a sintered body 1. On the side faces of the sintered body 1, meta-oriented aramid resin is applied by means of a roll applicator. In order to burn the applied aramid resin on the sintered body 1, the sintered body 1 is heated to form high-resistance layers 2. Nextly, both end faces of the sintered body 1 are ground and then aluminum is flamed to form electrodes 3 on both end faces of the sintered body 1. Thereby, the sintered body is made into a non-linear resistor. By this method, a burning temperature of the high resistance layer can be reduced and the sintered body is protected from cracked gas of SF6 gas and therefore a withstand level of the non-linear resistor can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-linear resistor containing zinc oxide as a main component.

[0002]

2. Description of the Related Art Generally, a lightning arrester is used to suppress an abnormal voltage in a power system and protect the power system. The lightning arrester employs a non-linear resistor that exhibits insulation characteristics at normal voltage and low resistance when abnormal voltage occurs and protects the system.

This non-linear resistor is made of zinc oxide (ZnO).
With Bi, Sb, Co, Mn, Ni, Cr,
Si is an auxiliary component. After thoroughly mixing these raw materials with water and an organic binder, granulate with a spray dryer or the like, shape the obtained granulated powder into a disk shape, and sinter the disk-shaped molded body to obtain a sintered body. In order to prevent creeping flash on the side surface of this sintered body, SiO ₂ , Bi ₂ O ₃ , Sb ₂ O ₃
A high resistance material is prepared by mixing the above materials with water and an organic binder and re-baked at 1000 to 1200 ° C to form a high resistance layer.
Further, both end surfaces of the sintered body are polished and electrodes are attached to form a non-linear resistor.

By the way, in recent years, electric power systems have become larger in capacity and higher in voltage. Along with this, the capacity of the non-linear resistor forming the lightning arrester is being increased. Specifically, the thickness and area of the non-linear resistor are increased.

However, such a large non-linear resistor is easily deformed at the time of sintering, and since it is re-fired at 1000 ° C. or more to form a high resistance layer, it is difficult to obtain a predetermined shape. was there. The deformation of the non-linear resistor causes deterioration or variation in electric properties such as non-linear resistance characteristics and discharge withstand voltage characteristics. The nonlinear resistor has a problem that may be used in SF ₆ gas often decomposed gas of SF ₆ gas corrosion upon contact with the sintered body occurs the electrical characteristics of the nonlinear resistor is degraded.

[0006]

SUMMARY OF THE INVENTION As described above, the conventional non-linear resistor has a problem that the electrical resistance is deteriorated and variation is increased due to the formation of a high resistance layer and the permeation of decomposed gas as the capacity is increased. there were. Therefore, an object of the present invention is to provide a method for manufacturing a non-linear resistor having a large capacity and improved discharge withstand voltage characteristics.

[0007]

In order to achieve the above object, in the present invention, as a first aspect of the present invention, a molded body containing zinc oxide as a main component is fired, and a high resistance layer is formed on a side surface of the obtained sintered body. In the method for manufacturing a non-linear resistor, a method for manufacturing a non-linear resistor characterized in that the high resistance layer is formed by applying an aramid resin to the side surface of the sintered body and heating the same. . Further, as a second invention, in a method for producing a non-linear resistor in which a molded body containing zinc oxide as a main component is fired, and a high resistance layer is formed on a side surface of the obtained sintered body, the side surface of the sintered body is Provided is a method for manufacturing a non-linear resistor, characterized in that an aramid resin and an aramid film are arranged in layers and heated to form two high resistance layers.

[0008]

[Function] Since the aramid resin and the aramid film are thermoset at a temperature of 400 ° C. or lower, the heating temperature for forming the high resistance layer can be made lower than before. Therefore, a non-linear resistor having a predetermined shape is easily obtained, and the discharge withstand voltage characteristic is improved.

Further, since the aramid resin and the aramid film have extremely small gas permeability, the side surface of the sintered body can be protected from the decomposition gas of SF ₆ gas, and the deterioration of the electrical characteristics of the nonlinear resistor can be prevented.

[0010]

[Embodiment] First embodiment

A first embodiment of the present invention will be described with reference to FIGS. 1 to 6. ZnO, which is the main component, has B as an auxiliary component.
i ₂ O ₃ , MnO ₂ , SiO ₂ and Cr ₂ O ₃ are each 0.5 m
ol%, Co ₂ O ₃ , Sb ₂ O ₃ and NiO are added to 1 mol each.
Add l% as raw material. Water and an organic binder such as a dispersant are added to this raw material and mixed in a mixing device, and the resulting mixture is spray granulated with a spray dryer to a particle size of 100 μm, for example. This granulated powder is put in a mold and pressed, and for example, it is fired in air to remove organic binders from a molded body obtained by molding into a disk shape, and further fired at a high temperature to show in FIG. Such a sintered body 1 is obtained. Next, the following meta-type aramid resin is applied to the side surface of the sintered body 1 using a roll coater.

[0012]

[Chemical 1]

The viscosity of the aramid resin during coating is adjusted to 5 to 30 poises, and the thickness of the aramid resin during coating is 50 to 300 μm.
Adjust to m. In order to bake the applied aramid resin on the sintered body 1, the sintered body 1 is heated in the firing pattern shown in FIG. That is, it takes about 1 hour to heat up to 150 ℃,
The temperature is maintained for about 1 hour, the temperature is gradually raised to 350 ° C over about 1 hour, and the temperature is maintained at 350 ° C for 2 hours, and then allowed to cool. The heating rate for baking the aramid resin is controlled to be 10 ° C / min or less. Thus, as shown in FIG.
After forming, the both end surfaces of the sintered body 1 are polished and aluminum is sprayed to form the electrodes 3 on both end surfaces to form a non-linear resistor. Next, the operation will be described.

In the present embodiment, the temperature for baking the high resistance layer is 350 ° C. or less, and the heating temperature can be greatly reduced as compared with the conventional temperature of 1000 ° C. Therefore, the distortion of the sintered body due to re-firing is reduced, and the discharge withstand value (hereinafter referred to as withstand value) of the nonlinear resistor can be improved.
As shown in FIG. 3, the resistance value of the non-linear resistor according to the conventional method is 180 J / CC, whereas the non-linear resistor according to the present embodiment is improved to 220 J / CC.

When the temperature is suddenly raised during baking of the aramid resin, bubbles or the like are generated in the aramid resin and an uneven portion is formed on the surface of the high resistance layer. The electric field is likely to be concentrated on this uneven portion, and there is a possibility that the flashover may occur and the withstand value may be reduced. Therefore, it is desirable that the heating rate be 10 ° C / min or less.

FIG. 4 shows the relationship between the thickness of the aramid resin at the time of application and the withstand value. In this example, the thickness of the aramid resin is in the range of 50 to 300 μm, but for comparison, the withstand value was also measured for the non-linear resistor coated with the aramid resin having a thickness outside this range. . As is clear from FIG. 4, the withstand value is improved in the present embodiment, that is, in the thickness range of 50 to 300 μm. The reason for obtaining such a result is that when the thickness is less than 50 μm, recesses are easily formed on the surface of the high resistance layer, and when the thickness exceeds 300 μm, it is included in the high resistance layer. The reason is that bubbles of about 10 to 100 μm are less likely to diffuse and an uneven portion is formed on the surface of the high resistance layer. The electric field is likely to be concentrated around the irregularities and the bubbles, and the surface flashover is likely to occur.

FIG. 5 shows the relationship between the viscosity of the aramid resin during coating and the withstand value of the non-linear resistor. When the aramid resin is applied to the sintered body, the viscosity of the aramid resin is preferably 5 to 30 poise as in this embodiment. If it is applied with a viscosity of less than 5 poises, a concave portion is likely to be formed in the high resistance layer, the thickness of the aramid resin is also 2 μm or less, and a creeping flashover easily occurs. Further, when an aramid resin having a viscosity higher than 30 poise is applied, the air bubbles contained in the aramid resin and the air bubbles generated at the time of application cannot be completely diffused to the outside of the aramid resin, so that the surface flashover easily occurs.

The aramid resin has excellent heat resistance, insulation and chemical resistance like the polyimide resin known as a heat resistant resin, and has extremely low gas permeability as compared with the polyimide resin, and SF ₆ gas. It is possible to protect the sintered body from permeation of decomposed gas. FIG. 6 shows a comparison of the electric current ratio of the non-linear resistor of this embodiment in which the side surface of the sintered body is coated with the aramid resin and the non-linear resistor in which the side surface of the sintered body is coated with the polyimide resin, and the current ratio is used as an example. Is. Leakage current ratio I _R / I which is the ratio of leakage current I _R and initial leakage current I _RO
RO becomes smaller than 1 as the nonlinear resistor deteriorates. A voltage was applied to the non-linear resistor and changes in the leak current ratio in SF ₆ gas at 80 ° C. were measured for several thousand hours. It was smaller than when the resin was applied, and as shown in FIG. 6, it hardly changed after 3000 hours.

As described above, according to this embodiment, by forming the high resistance layer of aramid resin, the re-firing temperature can be lowered, and the sintered body can be protected from the decomposition gas of SF ₆ gas. This has the effect of improving the withstand value of the resistor. The aramid resin has a viscosity of 5 to 30 poise, a thickness of 50 to 300 μm, and a heating rate of 10 for baking.
C./min or less is desirable. Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. 7 to 9.

Similar to the first embodiment, the sintered body 1 shown in FIG.
To manufacture. A aramid resin having a thickness of 5 to 20 μm is applied to the side surface of the sintered body 1, and an aramid film having a thickness of 20 to 100 μm processed to a size to cover the surface of the aramid resin is sintered on the aramid resin. Wrap around the side of. The aramid resin is made of the meta aramid shown in the first embodiment, and the para aramid shown below is used as the aramid film.

[0021]

[Chemical 2]

After winding the aramid film around the sintered body 1, the sintered body 1 is heated in the firing pattern shown in FIG. 2, and the high resistance layer 2a and the aramid film made of aramid resin are heated as shown in FIG. The high resistance layer 2b is formed. Both ends of the sintered body 1 on which the high resistance layers 2a and 2b are formed are polished, and the electrodes 3 are formed by spraying aluminum to form a nonlinear resistor.

When the aramid film is provided on the sintered body 1, an aramid resin may be applied to the aramid film in advance and the applied surface may be brought into close contact with the side surface of the sintered body 1. Further, the high resistance layers 2a and 2b may be formed after forming the electrodes 3 on both end surfaces of the sintered body 1. Next, the operation will be described.

In this embodiment, the baking temperature of the high resistance layers 2a and 2b is 350 ° C. or less as in the case of the first embodiment, and the baking temperature can be greatly reduced compared to the conventional case. Therefore, the distortion of the sintered body due to re-firing is reduced, and the withstand value is improved to about 220 J / CC. High resistance layer 2a,
The heating rate during baking of 2b is 10 ° C. as in the first embodiment.
/ Min or less is desirable.

FIG. 8 shows the relationship between the thickness of the aramid resin and the withstand value when the thickness of the aramid film is 80 μm. As shown in this example, when the thickness of the aramid resin is in the range of 5 to 20 μm, the improvement of the withstand value is recognized. On the other hand, when the thickness of the aramid resin is less than 5 μm, the applied aramid resin is absorbed by the minute holes on the surface of the sintered body, and a void is generated between the aramid resin and the aramid film, resulting in the adhesion of the aramid film. Becomes worse. On the other hand, if the thickness exceeds 20 μm, the organic solvent in the aramid resin is less likely to diffuse, voids are formed between the organic solvent and the aramid film, and irregularities are formed on the surface of the high resistance layer 2b. If the aramid film is peeled off or voids or irregularities are generated, creeping flashover easily occurs and the withstand value decreases.

FIG. 9 shows the relationship between the thickness of the aramid film and the withstand value when the aramid resin is applied in a thickness of 10 μm. As shown in this example, the reason why the improvement of the withstand value is recognized when the thickness of the aramid film is in the range of 20 to 100 μm is that the high resistance layer 2b has a thickness outside this range.
It can be mentioned that irregularities are likely to occur on the surface of and the surface flashover is likely to occur.

In the second embodiment, as in the first embodiment, the withstand value is improved, and since the aramid film already formed in the film shape is used, the high resistance layer having a predetermined thickness can be formed more easily. be able to.

[0028]

As described above, according to the method for manufacturing a non-linear resistor of the present invention, it is possible to lower the baking temperature of the high resistance layer by forming the high resistance layer with an aramid resin or an aramid resin and an aramid film. Moreover, since the sintered body can be protected from the decomposition gas of SF ₆ gas, the withstand value of the non-linear resistor can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a non-linear resistor according to a first embodiment of the present invention.

FIG. 2 is a firing pattern of a high resistance layer showing the first and second embodiments of the present invention.

FIG. 3 is a distribution of withstand values of a non-linear resistor according to the first and second embodiments of the present invention and a conventional non-linear resistor.

FIG. 4 shows the relationship between the thickness and the withstand value of the aramid resin showing the first embodiment of the present invention.

FIG. 5 shows the relationship between the viscosity at the time of application of the aramid resin showing the first embodiment of the present invention and the withstand value.

FIG. 6 is a comparison of leakage current ratios of a non-linear resistor baked with an aramid resin or an aramid resin and an aramid film according to the first and second embodiments of the present invention and a non-linear resistor baked with a polyimide resin.

FIG. 7 is a sectional view of a non-linear resistor according to a second embodiment of the present invention.

FIG. 8 shows the relationship between the thickness and withstand value of the aramid resin showing the second embodiment of the present invention.

FIG. 9 shows the relationship between the thickness and the withstand value of the aramid film showing the second embodiment of the present invention.

[Explanation of symbols]

 1 ... Sintered body, 2, 2a, 2b ... High resistance layer, 3 ... Electrode.

Claims (2)

[Claims] 1. A method for producing a non-linear resistor, comprising forming a high resistance layer on a side surface of a sintered body obtained by firing a molded body containing zinc oxide as a main component, wherein aramid is formed on the side surface of the sintered body. A method for manufacturing a non-linear resistor, which comprises applying a resin and heating the resin to form the high resistance layer. 2. A method for producing a non-linear resistor, comprising forming a high resistance layer on a side surface of a sintered body obtained by firing a molded body containing zinc oxide as a main component, wherein aramid is formed on the side surface of the sintered body. Place the resin and aramid film in layers and heat
A method for manufacturing a non-linear resistor, comprising forming the high resistance layer of a layer.