JPS5893201A - Lightning arrester and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a lightning arrester and its manufacturing method.

In recent years, capless surge arresters have been developed that omit the series gap by applying a voltage non-linear resistor element mainly composed of zinc oxide, instead of gapped surge arresters that add a series gap to a characteristic element mainly composed of silicon carbide. The mainstream of lightning arresters is shifting. Compared to gapped arresters, this gapless arrester is smaller, lighter, has fewer parts, and is more economical.
It has excellent features such as good stain resistance, good steep wave response, and resistance to multiple lightning strikes. In addition, a lightning arrester with a straight-line gap has also been put into practical use, in which a gap is provided in parallel to a part of the zinc oxide element.

On the other hand, since a discharge gap is not provided in series with the element, a small current constantly flows through the element, and the life of the element becomes a problem when used as a lightning arrester. In other words, conventional zinc oxide-based voltage nonlinear resistors suffer from deterioration of characteristics due to surge absorption or long-term constant voltage application, and leakage current gradually increases, eventually leading to thermal runaway. Gapless surge arresters and surge arresters with bypass caps using this type of surge arrester have the disadvantage that their surge handling ability decreases after long-term use, and eventually they run out of control. Furthermore, from the viewpoint of the lifespan of the elements, it was necessary to equalize the potential distribution of the lightning arrester so that an equal current flows through each element.

An object of the present invention is to provide a lightning arrester with better life characteristics than conventional ones and a method for manufacturing the same.

That is, the present invention provides a lightning arrester that is housed in a lightning arrester container with all internal elements composed of a voltage non-linear resistor element containing zinc oxide as a main component, in which the entire housing or part of the element forming the entire internal element is 5.11 A lightning arrester and zinc oxide comprising an element in which the concentration of γ-type bismuth oxide phase in the vicinity of the surface layer of at least one polar shadow-forming principal surface is higher than the concentration in the central part of the element; a step of using a sintered body containing at least boron oxide as an additive, a step of diffusing bis oxide from at least one major surface of the sintered body, and an electrode provided on the major surface of the sintered body. A method for manufacturing a lightning arrester, comprising the steps of providing the sintered body and storing the sintered body in a lightning arrester container.

The lightning arrester of the present invention includes γ-type bismuth oxide as a zinc oxide-based voltage nonlinear resistor element forming an internal element, and the concentration thereof is high near at least one main surface where an electrode is formed, and the thickness increases toward the center. It is characterized by using an element having a distribution that decreases in the direction. The present invention also provides a lightning arrester using an element in which a γ-type bismuth oxide phase having the above concentration distribution is formed by diffusing bismuth oxide from one or both of the upper and lower main surfaces of a sintered body containing zinc oxide as a main component. It is characterized by Furthermore, the present invention is characterized in that a surge arrester using these elements does not include any component for improving potential distribution in the surge arrester container. Note that it is particularly desirable that the lightning arrester of the present invention be a gapless lightning arrester or a lightning arrester with a bypass gap. Next, the present invention will be explained using the drawings.

FIG. 1 is a schematic diagram showing a cross section of an element used in the lightning arrester of the present invention. In the present invention, the concentration of the γ-type oxidized bismuth phase in the vicinity of either or both the upper and lower main surfaces of the main surface 11 on which the electrode 2 of the zinc oxide-based sintered body 1 containing bismuth oxide is formed is reduced by sintering. higher than the center of the body. The r-type bismuth oxide phase in this sintered body has the effect of improving the stability of the voltage nonlinear resistor against long-term electrification. Possible reasons for this are as follows.

Regarding the characteristic deterioration of zinc oxide-based voltage nonlinear resistor elements due to long-term energization, it is found that when the element is heat-treated in a nitrogen atmosphere, the characteristics deteriorate in the same way as when energization is applied, and that the deteriorated element is exposed to air or oxygen atmosphere. Because the properties return to their original properties when heat-treated inside the sintered body, oxygen in the grain boundary layer in the sintered body or oxygen adsorbed on the surface of the crystal grains is desorbed and dissipated to the outside when electricity is applied, and as a result, the grain boundary layer This is thought to be because the electrostatic potential of 141M decreases and leakage 141M increases. On the other hand, the γ-type bismuth oxide phase formed in the sintered body has a body-centered cubic structure, and the α-type bismuth oxide phase (monoclinic)
Because its volume is larger than that of the β-type bismuth oxide phase (tetragonal), it fills the gaps between grain boundaries and blocks the movement of oxygen. Alternatively, it is said that the γ-type hismuth oxide phase contains not only trivalent bismuth but also some pentavalent bismuth, and this pentavalent bismuth stabilizes the oxygen ions present in the grain boundary layer and Possible effects include preventing dissipation into the air. Especially bismuth oxide from the outside.

In the case of diffusion, the diffused bismuth oxide phase fills grain boundaries and pores, which has a particularly remarkable effect in preventing oxygen from escaping from the sintered body.

Furthermore, the effect of the high concentration of the γ-type bismuth oxide phase near the main surface 11 can be considered as follows.

That is, the resistance in the operating region of the element tends to decrease as the content of the γ-type bismuth oxide phase precipitated at the grain boundaries increases. In the element used in the present invention, since the resistance is low near the main surface 11, fewer hot needles are generated here than inside when electricity is applied, and less oxygen is dissipated to the outside. Not easy to deteriorate. On the other hand, in the interior where the γ-type bismuth oxide phase is small, a large amount of heat is generated when electricity is applied, but oxygen is dissipated to the outside through a thick layer, so the amount of dissipation is small and characteristics are less likely to deteriorate. As a result of the above, an element having a high concentration of γ-type bismuth oxide phase near the main surface where the electrode is formed has a long life when energized. When the concentration of the γ-type bismuth oxide phase is high near both the upper and lower main surfaces, the effect is significant.

The above-mentioned element with a high concentration of γ-type bismuth oxide phase on the main surface where the electrode is formed is produced by attaching or coating a diffusing agent containing bismuth oxide to one or both of the main surfaces of the sintered body, and diffusing it by heat treatment. It can be obtained by changing the phase to r phase.

By using the thus obtained element having a high concentration of r-type bismuth oxide phase in the vicinity of the main surface, it is possible to construct a capless surge arrester and a bypass gap surge arrester that have superior life characteristics than conventional ones. Furthermore, since the above-mentioned element can be used in a higher electric field than conventional elements, the number of elements used as a component can be reduced, the lightning arrester can be made smaller and lighter, and it has the advantage of improving earthquake resistance.

The element used in the present invention has zinc oxide as a main component,
This is a sintered body containing at least 0.05 to 5 mol of bismuth oxide. If the bismuth oxide content is outside this range, the nonlinear coefficient of the VI characteristic will not have a sufficiently large value. A decrease in the nonlinear coefficient is undesirable because it causes an increase in current at a constant charging rate and deteriorates the product characteristics of the device.

Furthermore, it is particularly desirable that the element used in the present invention contains 0.01 to 5 mol of boron oxide. This has the effect of increasing the nonlinear coefficient. If the amount of boron oxide is less than this range, the effect will be insufficient, and if it is too much, the nonlinear coefficient will decrease and the life will be shortened.

In addition to the above-mentioned additives, the voltage non-linear resistor used in the present invention contains 0.05 to 5 mol each of phosphor oxide, antimony oxide, cobalt oxide, chromium oxide, nickel oxide, and silicon oxide, and aluminum oxide. , and gallium oxide in an amount of 0.001 to 0.05 molty. These additives are effective in improving the non-linearity coefficient of the device, as well as the lifespan of charging and impulse withstand capability.

Next, according to the present invention, it is possible to omit components provided in the lightning arrester container in order to improve the potential distribution of the lightning arrester. Normally, in a lightning arrester, stray capacitance exists continuously in the height direction, so as shown in Figure 2, the potential distribution of the lightning arrester is not uniform as shown by the broken line, but becomes like the solid line, and some elements are They will share a large amount of voltage. Generally, the upper element has a larger voltage share. In conventional gapless surge arresters and surge arresters with side gap, a compensating capacitor, etc. is installed inside the surge arrester container to prevent the life of the entire surge arrester from being shortened due to a voltage that is higher than evenly distributed in some elements. , the potential distribution was improved so that an equal voltage was applied to each element.

However, since the lightning arrester of the present invention has good element life characteristics,
A certain amount of voltage is applied to some elements (9)
It is possible to ensure that the lightning arrester has a sufficient lifespan even when the lightning is on. Therefore, it is possible to omit components necessary for improving the potential distribution of the lightning arrester.

As a result, the number of parts of the lightning arrester can be reduced, miniaturization is possible, and there are advantages such as improved economy and reliability.

As is clear from this point, the above-described elements with good life characteristics may be used for all of the elements forming the internal elements, but they may also be used for some of them. For example, it is possible to construct a lightning arrester with superior lifetime characteristics by using the above-mentioned elements with good lifetime characteristics for the elements that are larger than those in the case where the voltage sharing is uniformly distributed, and by using conventional elements for the other elements.

The present invention will be explained below with reference to Examples.

Example l Zn01CBi203Q, 7 mol%, Mn CO30,
5 mol L 002031.0 mol/l/%, Cr203
0.5 mol%, 5b2031.0 mol Ni0 1.0 mol, 5in21.5 mol) 32o30.1 mol Az (NO3) 30.005 mol was added and sintered to obtain a diameter of 60 mm (10) Thickness Bismuth 2
A paste consisting of g, 0.5 g of ethyl cellulose Q, and 0.4 g of flucarbitol was applied almost uniformly,
Heat treatment was performed at 950'C for 2 hours. Next, A/ was thermally sprayed onto the amphiboid surface to form an electrode having a diameter of 56 mm.

The nonlinear coefficient of the obtained voltage nonlinear resistor element (current 10
μA to 1 mA) was 24, the flat rate (ratio of the voltage when the current was 10 kA and the voltage when the current was 1 mA) was 1,720'c, and the voltage when the DC current was 1 mA was 4.6 kV.

Thirty-five of these elements were connected in series to form a lightning arrester internal element. This internal element is housed in an insulator tube (inner diameter 120mm),
A gapless lightning arrester was constructed by installing a regular shield on the outside. Figure 3 shows the structure of this gapless arrester. In FIG. 3, 30 is a lightning arrester, 31 is an internal element, 32 is an insulator tube, and 33 is a shield. [.

The voltage nonlinear resistor element used in this example was heated to 80'.
c. The time change of the resistance leakage current (11) when the current was continuously applied at AC (effective value) 3.04 kV (charge rate 100%) was as shown in Figure 4. Here, the charging rate is
DC 1mA at 20'C of applied AC voltage peak value
It is the ratio to the voltage required to flow.

As seen in FIG. 4, the resistance current of this device after 10,000 hours of energization did not reach 1.5 times the initial value. Taking into consideration the acceleration of property deterioration due to temperature, this corresponds to a life of over 30 years at 40'C under actual use.

On the other hand, when the potential distribution of the gapless lightning arrester of this example was obtained by approximate calculation, the voltage sharing was maximum at the uppermost element, and its thickness was 1.3 times that in the case of uniform distribution. Therefore, when the gapless lightning arrester of this embodiment is applied to a system with a maximum system voltage of 1101c'V in consideration of the protection characteristics, the charging rate for the normal operating voltage is 100X42X (
110/M block)/4.6X35=55.8 (%). Therefore, the charging rate targeted at the element with the largest voltage share is 55
．． 8x1.3-72.5 (%). From the life characteristics of the above elements, the gapless arrester of this example has a sufficient life as a surge arrester with a rated voltage of 112 kV (12 kV).
).

Further, FIG. 5 shows the concentration distribution of the γ-type bismuth oxide phase in the device used in this example. The distribution of the r-type bismuth oxide phase can be determined by cutting the device into 0.5-thick pieces parallel to the main surface on which the electrodes are formed, pulverizing each section, and diffracting the γ-type bismuth oxide phase using X-ray powder diffraction. Determined from line strength. In the measurement, a reflection line with a lattice spacing of 2□71 to 2.72 A was used and normalized by the diffraction line intensity of ZnO. FIG. 5 shows the distribution when the concentration of the γ-type bismuth oxide phase in the center of the element is normalized to 1. As seen in this figure, the concentration of the γ-type bismuth oxide phase in the device used in this example is
It is high near the surface layer of the main surface where the electrode is formed and low inside.

Example 2 Paster containing bismuth oxide was applied and diffused from one of the main surfaces of a sintered body obtained in the same manner as in Example 1, and A was applied to both sides.
/ was thermally sprayed to form an electrode with a diameter of 56 mm. The voltage required to pass 1 mA of DC through the resulting voltage nonlinear resistor element is 4.
．． It was 3kV. Ko (13)
.

When the element was continuously energized with alternating current at a temperature of 80'C and a charge rate of 100, the increase in resistance current was slightly greater than that of the element used in Example 1, but even after 10,000 hours of energization, the initial The current did not reach 1.5 times.

Further, without applying and diffusing a paste containing bismuth oxide to a sintered body obtained in the same manner as in Example 1, an electrode having a diameter of 56 cm was formed by thermally spraying AI on the bibulous surface.

The voltage required to pass 1 mA of direct current through the obtained voltage nonlinear resistor element was 4.2 kV. This element is heated to 80'
c. When AC current was continuously applied at a charging rate of 100%, the resistance current increased to 7.5 times the initial current after 1000 hours of current application. On the other hand, this element was heated at a temperature of 80'C and a charge rate of 70
%, the resistance current did not reach 1.5 times the initial current after 10,000 hours of current application.

Of these two types of elements, 30 elements in which bismuth oxide was not diffused were laminated, and 30 elements in which bismuth oxide was diffused from one side were laminated to form a gapless surge arrester as an internal element of the surge arrester.14) Ta.

Approximate calculation of the potential distribution at this time shows that for the 30 elements below, the potential sharing is at most 098 times that of the uniform distribution.
It was found that for the above 30 elements, the increase was at most 1.4 times.

When this gapless arrester is applied to a system with a maximum system voltage of 220 kV, the charging rate for the normal operating voltage is 10
0xJ7x (22o/, rth)/(4,2X30+4
．． 3×30)=70.4 (%). Therefore, the 3 below
For 0 elements, the charging rate is all 70% (70,4
For the above 30 elements, the charge rates are all 100chi (70,4X 1.4 ) or less. From the life characteristics of each element described above, it can be seen that the gapless lightning arrester of this example has a sufficient life of 30 years or more as a lightning arrester with a rated voltage of 2101cV.

In this case, only the elements that do not diffuse bismuth oxide are
Assuming that a gapless arrester is constructed by stacking 0 pieces,
It is clear that the characteristic deterioration of elements with large potential sharing becomes serious, and it is not possible to provide a lightning arrester with a sufficient lifespan (15).

In addition, the distribution of the concentration of the γ-type bismuth oxide phase in the element in which bismuth oxide was diffused from one of the main electrode-forming surfaces used in this example was investigated using X-ray powder diffraction in the same manner as in Example 1. It was found that the concentration of the γ-type bismuth oxide phase was highest in the vicinity of the surface layer of the main surface on which the electrode was formed, where diffusion was applied, and that it gradually decreased in the thickness direction.

Example 3 An internal element of a lightning arrester was prepared by connecting in series 50 elements in which electrodes were formed by coating and diffusing a paste containing bismuth oxide after sintering on both the upper and lower main surfaces obtained in the same manner as in Example 1, and compensation. A surge arrester with a bypass cap was constructed by housing a parallel capacitor for the above and a bypass gap in an insulator tube. Figure 6 shows the structure of this lightning arrester. 61 in FIG. 6 is a bypass gap.

When this arrester is applied to a system with a high voltage of 275 kV, the charging rate for the normal operating voltage is 100x fE.
x (275/, 1 gun) / 4.6 x 50
= 97.6 (%). The potential distribution (16) is made uniform by the compensation capacitor, and the charge rate to each element is 100%.
According to the life characteristics of the element described above, the lightning arrester of this embodiment has a life of 30 years or more as a lightning arrester with a rated voltage of 266 kV.

In addition, if you try to give a lightning arrester a similar lifespan using conventional elements, it is necessary to suppress the charging rate to 70 coefficients or less, and to do this, the number of elements must be approximately 10/7 or more of the above. Is required. That is, in the lightning arrester of this embodiment, the number of required elements is reduced to about 70% of the conventional one. Furthermore, since the number of elements is approximately 70 inches compared to the conventional one, the protection level of the lightning arrester when a surge occurs is reduced to approximately 70% of that when conventional elements are used, improving the protection performance.

Therefore, the voltage resistance design of system equipment becomes easier.

As explained above, according to the present invention, the deterioration of the characteristics of the element can be reduced compared to the conventional surge arrester, so it has the effect of improving the life characteristics of the capless surge arrester and the surge arrester with a bypass gap.

[Brief explanation of drawings]

(17)+ Figure 1 is a cross-sectional view showing the structure of a voltage nonlinear resistor element, Figure 2 is a diagram showing the potential distribution of a lightning arrester, and Figures 3 and 6 are obtained in an example of the present invention. FIGS. 4 and 5 are diagrams showing the structure of the lightning arrester, and are characteristic curve diagrams showing the characteristics of the elements used in the embodiments of the present invention. 1... Zinc oxide-based sintered body, 2... Electrode, 11...
Main surface for electrode formation, 31...Zinc oxide voltage nonlinear resistor element (internal element), 32...Insulator tube, 33...Shield, (18) 1st Figure 2 II Hanging 2 Figure Height Height 1 nina ten customer bow @-) 3rd ward ¥ 4 Trouble 6- Condolence 6 Figure 0)

Claims (1)

[Claims] 1. Main ingredient is zinc oxide. In a lightning arrester in which an internal element constituted by a voltage non-linear resistor element is housed in a lightning arrester container, γ-type oxidation in the vicinity of the surface layer of at least one main surface on which an electrode is formed as all or a part of the element forming the internal element. A lightning arrester comprising one element in which the bismuth phase concentration is higher than the concentration in the central part of the element. 2. Claim 1, wherein the element has a γ-type bismuth oxide phase having the concentration distribution by diffusing bismuth oxide from one or both of the upper and lower main surfaces of a sintered body containing zinc oxide as a main component. What is claimed is: 1. A lightning arrester characterized by being an element in which electrodes are formed on the upper and lower principal surfaces. 3. A step of preparing a sintered body mainly composed of zinc oxide and containing at least boron oxide as an additive, a step of diffusing bis oxide from at least one main surface of the sintered body, a main surface of the sintered compact. 1. A method for manufacturing a lightning arrester, comprising the steps of: providing an electric current to the sintered body; and storing the sintered body in a lightning arrester container.