JPS6328562Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a lightning arrester whose characteristic element is a voltage nonlinear resistance element containing zinc oxide (ZnO) as a component. In this type of lightning arrester, the desired operating voltage is ensured by the number of stacked elements, which are characteristic elements, but in order to obtain the desired discharge withstand capacity, the element area must be made large. Enlarging the area of a voltage non-linear resistance element has problems in element formation and element characteristics, making it difficult to improve discharge durability. In other words, the voltage nonlinear resistance element shrinks by about 40% in volume during the firing process at 800 to 1000°C, and shrinkage distortion is likely to occur during molding.
The larger the element, the greater the strain and the more likely it is that the element will crack. In addition, bismuth oxide (Bi ₂ o ₃ ) added to element formation melts during firing to form a liquid phase and sinter the element, but this liquid phase sintering is performed at 1000℃
The above becomes active, and eventually a structure is formed in which high-resistance Bi ₂ o ₃ surrounds the grain boundaries of Zno particles of about 10μ, and voltage nonlinearity is established from the junction between the two.
If the entire element does not react uniformly during firing, the grain growth rate of the Zno particles will vary, resulting in variations in the particle size of the Zno particles. For this reason, the larger the device is made, the more likely it is that a non-uniform state will occur where particles with large diameters exist inside the device, and the device current will concentrate on the coarse crystal grains, avoiding the grain boundaries with high resistance. As a result, large devices often have poor voltage nonlinear characteristics. Therefore, as a large-sized element that can be fired uniformly to the inside of the element, there is one that is constructed in the shape of a donut with the central part removed, as shown in FIG. However, in order to obtain the same area of the electrode 1 as the conventional type shown in FIG. 2, this donut-shaped element has a larger outer diameter 2l, and the diameter of the insulator tube that houses the element block has also become larger. It becomes an expensive lightning arrester. In FIGS. 1 and 2, 2l indicates a side insulating layer, and 3 indicates an element body. The present invention was developed in view of the above circumstances, and by installing a separately formed voltage non-linear resistance element in the hollow part of a hollow donut-shaped element, the limiting voltage ratio is improved without increasing the size of the element. However, it is an object of the present invention to provide a lightning arrester with improved discharge withstand capacity. FIG. 3 is a side sectional view a and a view b taken along the line X--X, showing an embodiment of the present invention. Donut-shaped element A
The inner diameter of element A and the outer diameter of element B are designed so that element B is loosely fitted in the center, and the distance d between elements A and B is designed to allow heat flow to dissipate heat from both elements A and B. road is secured. Elements A and B are designed to have the same height dimension h. Elements A and B with such a configuration are individually and simultaneously fired with the same material ratio, and the Zno and Bi ₂ o ₃ are uniformly bonded during firing, making it possible to form an element with improved current and voltage characteristics as a single element. It will be planned. In addition, the characteristic elements that are a combination of elements A and B are stacked with electrode plates C sandwiched between each stage, as shown in Figure 4a, and the electrode plates C have punched holes at least between A and B. A ventilation path between elements A and B is ensured by using a multi-hole electrode plate structure. The stacked structure of these elements A and B is shown in Figure 4 b and c.
The configuration shown in can also be used. Figure b shows elements A _{and B1} stacked in two stages compared to three stages of elements A.
A height dimension of B ₁ is designed. In the same diagram, element A is shown in C.
Two types of elements A ₁ and A ₂ with different inner diameters are prepared, and elements B ₂ and B are installed inside the elements A ₁ and A ₂ with the same spacing, respectively. Stack them alternately. In this case, although there is no ventilation path between the elements A and B, there is an advantage that the stacked surface can secure a portion where the inner elements B ₂ and B ₃ and the outer elements A ₁ and A ₂ meet, and the electrode plate can be omitted. As described above, according to the present invention, the structure in which the cylindrical element is provided inside the donut-shaped element facilitates manufacturing with good characteristics of both elements, and does not increase the overall diameter of the lightning arrester. Moreover, compared to a conventional structure composed of only a donut-shaped element, the electrode area can be increased with the same outer diameter, and the limiting voltage ratio and discharge withstand capacity can be improved. For example, 100mm diameter,
A cylindrical element A shown in FIG. 2 with a height of 22 mm, a donut-shaped element B shown in FIG. 1 with an inner diameter of 40 mm and the same electrode area as in FIG.
We prototyped an element C with a cylindrical element of mm in diameter and a cylindrical element D shown in Fig. 2 with the same electrode area as the element C, and tested their respective limiting voltages V10 _kA / 1 _nA and 2 ms discharge withstand capacity. The results are shown in the table below.

[Table] As is clear from this table, according to the present invention, the device shown in C has an excellent limiting voltage ratio and excellent discharge withstand capacity. In addition, in the present invention, according to the structure shown in FIG. 4 a and b in which a ventilation path is formed between the elements A and B, the element surface area is increased and heat dissipation through ventilation is improved, resulting in a uniform temperature distribution of the element. This has the effect of suppressing the rise in element temperature due to long-term energization.

[Brief explanation of the drawing]

Figures 1 and 2 are configuration diagrams of conventional lightning arrester elements;
FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a block diagram showing the stacking of elements in the present invention. A: Donut-shaped element, B: Cylindrical element.

Claims (1)

[Scope of utility model registration request] In a lightning arrester whose characteristic element is a voltage non-linear resistance element mainly composed of zinc oxide, a first voltage non-linear resistance element configured in a donut shape and a first voltage non-linear resistance element formed in the same material ratio as this element and individually fired. and a cylindrical second voltage nonlinear resistance element that is loosely fitted inside the element, and the first and second voltage nonlinear resistance elements are stacked as characteristic elements to obtain a desired operating voltage. Characteristic lightning arrester.