JPH0529108A - Nonlinear resistor - Google Patents

Abstract

PURPOSE:To get a nonlinear resistor where the discharge withstand current rating is hard to drop even if the size is enlarged by using an inorganic adhesive which contains fibers as a high resistance layer. CONSTITUTION:An inorganic adhesive, which contains 20-32% fibers which have, for example Al2O3 for their main ingredients, are applied on the side of a sintered substance, using a roll applicator. The average length of this fibers is, for example, 100mum, and the thickness is 2-3mum, and the main ingredient of the inorganic adhesive is, for example, Al2O3 or SiO2. After application of this inorganic adhesive which contains the fibers, a high-resistance layer 2 is stored to the side of the backed substance 1. That is, the temperature is raised 150 deg.C in two hours, and this temperature is maintained for two hours, and further the temperature is raised 350 deg.C, and this condition is maintained for two hours, and then it is cooled in three hours. Hereby, a nonlinear resistor excellent in discharge withstand current rating can be gotten.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear resistor used in an overvoltage protection device.

[0002]

2. Description of the Related Art Generally, a system voltage is suppressed in an electric power system,
Lightning arresters are installed to protect the power system. This lightning arrester uses a non-linear resistor that exhibits almost insulating characteristics at normal voltage and changes to a low resistance value when an abnormal voltage is applied.

For the non-linear resistor, a sintered body is used which is mainly composed of zinc oxide ZnO and is sintered by adding at least one additive such as a metal oxide so as to exhibit non-linear characteristics. A material for forming a high resistance layer is applied to the side surfaces of this sintered body to prevent flashover, and baked, and electrodes are formed on both end surfaces to form a non-linear resistance body.

As a conventional high resistance layer, for example, SiO ₂ ,
The _{Bi 2 O 3, Sb 2 O} 3 or the like is mixed with water and an organic binder is applied to the sintered body side, 1000-1200
An inorganic high resistance layer that is baked at ℃ is known.

By the way, in recent years, the electric power system has been increasing in capacity and voltage, as represented by 100 KV (UHV), which is planned for practical use. In order to cope with such large capacity and high voltage, it is necessary to increase the thickness and diameter of the non-linear resistor to increase the size.

[0006] However, such a large non-linear resistor is easily deformed during firing, and electrical characteristics are likely to vary. Moreover, in order to form a high resistance layer
Since it has to be re-fired at a high temperature of 00 to 1200 ° C., residual stress occurs in the sintered body itself. In order to reduce such residual stress acting on the sintered body, it is necessary to prevent the bending strength of the side surface of the sintered body, which is in contact with the high resistance layer, from decreasing. That is, the high resistance layer must be formed of a material having an appropriate coefficient of thermal expansion. However, conventionally, the coefficient of thermal expansion has been changed by changing the substance to be applied, so that it is difficult to control the coefficient of thermal expansion, and there is a problem that the discharge withstand capacity decreases as the size of the non-linear resistor increases.

[0007]

As described above, when the conventional non-linear resistor is made large in size in order to cope with the increase in capacity and the increase in voltage, the electric characteristics are likely to vary, and in particular, the baking in contact with the high resistance layer is made. There is a problem that the discharge withstand characteristic deteriorates due to the decrease in strength of the side surface of the united body. Therefore, it is an object of the present invention to provide a non-linear resistor in which the discharge withstand voltage characteristic does not easily deteriorate even when the size is increased.

[0008]

In order to achieve the above object, the present invention provides a non-linear resistor having a high resistance layer formed on a side surface of a sintered body containing zinc oxide as a main component, wherein the high resistance layer is Provided is a non-linear resistor characterized by being an inorganic adhesive containing a fiber.

[0009]

The thermal expansion coefficient of the high resistance layer formed on the side surface of the sintered body can be changed by the amount of the fiber contained in the inorganic adhesive. Therefore, it is possible to form a high resistance layer having an appropriate coefficient of thermal expansion by increasing or decreasing the amount of contained fiber, and it is possible to prevent the bending strength of the side surface of the sintered body in contact with the high resistance layer from decreasing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

ZnO is 95 mol% and Bi ₂ O ₃ , M
0.5 mol% of nO ₂ , SiO ₂ and Cr ₂ O ₂ and 1 mol% of (Co ₂ O ₃ , Sb ₂ O ₃ and NiO, respectively) were added and mixed, and water and an organic binder such as a dispersant were added. And spray granulate to a particle size of 100 μm with a spray dryer.
It is molded into a disk-shaped m having a thickness of 22 mm and the molded body is fired to obtain a sintered body 1 shown in FIG.

An inorganic adhesive containing 20 to 32% of fibers containing Al ₂ O ₃ as a main component is applied to the side surface of the sintered body 1 by using a roll coater. The average length of this fiber is, for example, 100 μm, the thickness is 2 to 3 μm, and the main components of the inorganic adhesive are, for example, Al ₂ O ₃ and SiO ₂ .
After applying the inorganic adhesive containing this fiber, the high resistance layer 2 is baked on the side surface of the sintered body 1 in the baking pattern shown in FIG. That is, the temperature of 150 ° C. is raised over 2 hours and kept at this temperature for 2 hours, the temperature of 350 ° C. is further raised and kept in this state for 2 hours, and then cooled over 3 hours. If the firing rate is too fast, bubbles will be generated in the inorganic adhesive to form irregularities in the high resistance layer 2, so the temperature change during firing is preferably 10 ° C./min or less. In this way, both end surfaces of the sintered body 1 on which the high resistance layer 2 is formed are polished and aluminum is sprayed to form the electrodes 3 to obtain a nonlinear resistor. The high resistance layer 2 may be formed after the electrode 3 is formed. Next, the operation will be described.

The coefficient of thermal expansion of the high resistance layer 2 is determined by the ratio of the fiber and the inorganic adhesive. In this embodiment, the coefficient of thermal expansion is set to 20 to 32% for the fiber and 80 to 68% for the inorganic adhesive. Can be 2.5 to 6.2 × 10 ⁻⁶ 1 / ° C. As shown in FIG. 3, the relationship between the coefficient of thermal expansion of the high resistance layer 2 and the discharge withstand capability of the non-linear resistor has a coefficient of thermal expansion of less than 2.5 × 10 ⁻⁶ 1 / ° C. or 6.2 × 10 ^−6.
At 1 / ° C. or higher, there is a relationship that the withstand capability decreases. If the coefficient of thermal expansion is too large, the high resistance layer 2 expands due to the temperature rise of the non-linear resistor due to energization, and tensile stress acts on the side surface of the sintered body 1. On the contrary, if the coefficient of thermal expansion is too small, the high resistance layer 2 does not expand as compared with the thermal expansion of the sintered body 1, and the sintered body 1
A compressive stress acts on. Therefore, in order to reduce the stress acting on the sintered body 1, the coefficient of thermal expansion of the high resistance layer 2 is 2.5 to
It is preferably 6.2 × 10 ^-6 1 / ° C.

Further, since the surface of the high resistance layer 2 has a microscopically concave portion, a creeping flashover may occur at a portion where the thickness is thin due to the concave portion. Therefore, the high resistance layer 2 needs to have a certain thickness, and the thickness of the high resistance layer 2 is 100 as shown in FIG. 4 showing the relationship between the high resistance layer 2 and the discharge withstand voltage.
It is desirable that the thickness is 300 μm.

According to the present embodiment, the baking temperature of the high resistance layer 2 is about 350 ° C., and the heating temperature at the time of re-baking can be made considerably lower than that of the conventional one. Stress is reduced.

Further, the thermal expansion coefficient of the high resistance layer 2 is 2.5 to 6.2 × by setting the amount of Al ₂ O ₃ fiber in the inorganic adhesive forming the high resistance layer 2 to ₂₀ to 32%. 1
The stress can be set to 0 ⁻⁶ 1 / ° C., and the stress acting on the sintered body 1 when the nonlinear energy is heated by the application of surge energy can be reduced. Therefore, as shown in the distribution diagram of discharge withstand capability in FIG. 5, SiO ₂ , Bi ₂ O ₃ , Sb ₂
The discharge withstand capacity of about 40 J / cc is improved as compared with the conventional product in which a mixture of O _{3 and the} like is baked at 1200 ° C. to form the high resistance layer 2.
Moreover, the coefficient of thermal expansion of the high resistance layer 2 can be easily changed by increasing or decreasing the amount of fiber contained, so that a high resistance layer having an optimum coefficient of thermal expansion can be formed depending on the size and type of the sintered body.

[0017]

As described above, according to the present invention, a high resistance layer is formed by baking an inorganic adhesive containing fibers on the side surface of a sintered body containing zinc oxide as a main component, which results in excellent discharge resistance. It is possible to provide a non-linear resistor.

[Brief description of drawings]

FIG. 1 is a sectional view of a non-linear resistor.

FIG. 2 Firing pattern of inorganic adhesive containing fibers

[Fig. 3] Relationship between thermal expansion coefficient and discharge withstand capability

[Fig. 4] Relationship between thickness of high resistance layer and discharge withstand capability

[Fig. 5] Distribution map of discharge withstand value

[Explanation of symbols]

 1 ... Sintered body 2 ... High resistance layer 3 ... Electrode

Claims (1)

Claim: What is claimed is: 1. A non-linear resistor having a high resistance layer formed on a side surface of a sintered body containing zinc oxide as a main component, wherein the high resistance layer is an inorganic adhesive containing a fiber. A non-linear resistor characterized by being present.