JPH03254087A - Zinc oxide element for lightning arrester with gap - Google Patents

Abstract

PURPOSE:To provide a ZnO element suitable for use in a lightning arrester provided with a gap, by including Bi2O3, and using ZnO whose specific dielectric factor is over 600 and whose restrictive voltage ratios at 1mA/cm<2> and 10muA/cm<2> range 1.4 thru 2.0. CONSTITUTION:It is known that a resistant body chiefly containing ZnO and also including a minor amount of Bi2O3, etc., exhibits an excellent linearity, and the restrictive voltage ratio has generally been flattened between 1mA/cm<2> and 10muA/cm<2> according to any conventional method. Contrary to this common sense, the restrictive voltage ratios at 1mA/cm<2> and 10muA/cm<2> shall be made over 1.4 and below 2.0. The specific dielectric factor of ZnO incl. Bi2O3 shall be kept over 600. This provides easy flowing of current in the minor amperage range, causes flash shortcircuit on the series gap 4 side certainly at the time of cloud-to-ground discharge, and enhances the insulative coordinativeness with an arc horn 1. Also the subsequent stream shutoff characteristic is enhanced due to selecting the V1mA/V10muA to below 2.0.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a zinc oxide element for a gap-type lightning arrester, which contains zinc oxide as a main component.

(Conventional technology) Bi203 has traditionally been made with zinc oxide (ZnO) as the main component.
Sb203.5102. Resistors containing small amounts of metal oxides such as CO2O3 and MnO2 as subcomponents are widely known to exhibit excellent voltage nonlinearity, and are used in lightning arresters and the like by taking advantage of this property.

On the other hand, more than half of electrical accidents on overhead power transmission lines are caused by lightning. When a transmission line is struck by lightning and the potential of the tower rises, an arcing horn discharges, followed by a fault current (follow-on current). The power was cut off by the circuit breaker at the substation due to the flow of electricity.

To solve this problem, a gap-type lightning arrester was developed, as schematically shown in the drawing. Conceptually, this is a lightning protection function added to the arc horn 1 of the insulator device 2.
It is composed of a current limiting element section 3 and a series gap 4. The current limiting element section 3 is constructed by connecting zinc oxide elements having non-linear voltage resistance characteristics in series and housing them in an insulator (porcelain tube) or molded with an insulator (ethylene, propylene rubber). As a result, when the tower potential rises due to a lightning strike on a power transmission line, it is discharged in the series gap 4, and in a short time, the non-linear resistance characteristics of the current limiting element are used to completely block the follow-on current, resulting in substation. The aim is to prevent power outages by preventing circuit breakers from operating.

(Problem to be solved by the invention) However, since it is necessary to newly insert a gap-type lightning arrester between the existing steel towers, there is a problem with insulation coordination with the arc horn 1, and when lightning strikes, a flashover occurs in the series gap 4. It is necessary to prevent the arc horn from flashing. In order to preferentially cause a flash fault to occur in the series gap 4 during a lightning strike, it is conceivable to reduce the number of zinc oxide elements in the current limiting element section 3 to make it easier for the current to flow toward the series gap 4 side. However, when the number of the above-mentioned elements is reduced, current flows more easily than in the past, and the follow-on current blocking performance deteriorates.

It is also conceivable to reduce the interval between the series gaps, but in this case, there is a possibility of flash shorting due to opening/closing surges generated by opening/closing of the cutoff path.

For power transmission lines of 33 KV or higher, especially 66 to 154 Kv, it is difficult to design from the standpoint of insulation from the arcing horn, and conventional zinc oxide elements with dielectric constants of 500 to 600 are used. In this case, it became difficult to make a good lightning arrester, and complicated work such as replacing the arc horn became necessary.

An object of the present invention is to provide a gap-type lightning arrester that can reliably prevent flash shorting at the arc horn of a gap-type lightning arrester, thereby increasing the reliability of the lightning arrester, and improving the design margin of the lightning arrester. An object of the present invention is to provide a zinc oxide element for a type lightning arrester.

(Means for Solving the Problems) The present invention is a zinc oxide element used in a current-limiting element of a gap-type lightning arrester for a power transmission line connected between a power transmission line and earth, the element comprising at least bismuth oxide. Contains a dielectric constant of 600 or more, and has a dielectric constant of 1mA/Cm2 and 10μ
Limiting voltage ratio V I-A / V at A/an2
The present invention relates to a zinc oxide element for a gap type lightning arrester, characterized in that 1o u A is 1.4 or more and 2.0 or less.

(Function) In the present invention, unlike the prior art, the dielectric constant is set to 600 or more (preferably 850 or more), so that the flashover voltage of the series gap 4 shown in the drawings can be reduced against lightning surges. That is, the series gap 4 causes a flashover even when a lightning surge voltage is lower than the conventional one. Therefore, conventionally, the flashover voltage of the series gap 4 is higher than the flashover voltage of the arc horn 1, or the difference between the two is relatively small (for example, 1.2
Even in cases where the reliability is low due to the fact that the lightning arrester is less than 2 times as large, the reliability of the lightning arrester is high and the design margin is high because the zinc oxide element according to the present invention can be used to reliably flash over the series gap 4. . If the dielectric constant of the zinc oxide element at IMHz is less than 600, the shared voltage across the series gap 4 will be reduced, resulting in a large-sized lightning arrester structure and poor reliability of the lightning arrester.

Moreover, in the present invention, 1 mA/cm of the zinc oxide element
” and the limiting voltage ratio V3 at 10 μA/cm2, /
It is extremely important that V + o 11 A be 1.4 or more and 2.0 or less (preferably 1.6 or more and 1.9 or less).

That is, in the past, it was common practice to make the voltage between 1 mA/Cm2 and 10 μA/cIo2 very flat (good voltage nonlinearity).

On the other hand, in the present invention, contrary to conventional common sense, 1
The feature is that the limiting voltage ratio at mA/cm2 and 10μA/a [+2] has been increased to 1.4 or more, which makes it easier for current to flow in the small current region and ensures that there is no flash on the series gap side in the event of a lightning strike. It is possible to improve the insulation coordination with the arc horn by connecting it to the arc horn.

Moreover, the above limiting voltage ratio V+-/V+oμ is 2.0
Since it is as follows, the follow-on current blocking property is good.

Suppose this limiting voltage ratio V1□/V+. When μ9 was less than 1.4, the flashover voltage at the series gap increased, making it difficult to use, and when μ9 exceeded 2.0, the follow-on current blocking performance decreased.

(Example) To manufacture a zinc oxide element, a zinc oxide raw material adjusted to a predetermined particle size, bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, chromium oxide, silicon oxide, nickel oxide, A predetermined amount of additives such as silver oxide, boron oxide, etc. are mixed. In this case, silver nitrate or boric acid may be used instead of silver oxide or boron oxide. Preferably, bismuth borosilicate glass containing silver is used. A predetermined amount of polyvinyl alcohol aqueous solution or the like is added to these raw material powders, mixed preferably using a disper mill, and then granulated, preferably using a spray dryer, to obtain a granulated product. After granulation, molding pressure 80C1-
Form into a predetermined shape under 1000 kg/cm2. Then, the molded body is heated and cooled at a rate of 30 to 70°C/br
Temporary firing is carried out under the conditions of 800 to 1000°C for a holding time of 1 to 5 hours.

In addition, before calcining, the molded body is heated and cooled at a rate of 10 to 100'.
It is preferable to remove the binder by scattering it by heating at 400 to 600° C. for a holding time of 1 to 10 hours at C/br. This is called a defatted body.

Next, a side high resistance layer is formed on the side surface of the calcined body. A mixture paste for side high resistance layer, which is made by adding ethyl cellulose, butyl calpitol, n-butyl acetate, etc. as an organic binder to a predetermined amount of bismuth oxide, antimony oxide, silicon oxide, etc., is applied to a calcined body to a thickness of 60 to 300 μm. Apply to the sides. Note that the mixture paste may be applied to a molded body or a degreased body. Next, this temperature increase/decrease rate is 40
~60°C/hr.

1000-1300°C preferably 1100-1250
The main firing is carried out under the conditions of a holding time of 3 to 7 hours at °C.

In addition, a glass paste made by adding ethyl cellulose, butyl calpitol, n-butyl acetate, etc. as an organic binder to glass powder is applied to the side surface high resistance layer in a thickness of 100 to 300 μm.
Coated to a thickness of m and heated at a rate of 100 to 200 in air.
°C/hr, 500-900°C1 holding time 0.5-1
By performing the heat treatment for 0 hours, it is also possible to form the glass layer at the same time.

Thereafter, both end faces of the obtained zinc oxide element were coated with SiC.

#400 to #2000 such as Al2O3, diamond, etc.
Polish using water or oil with a suitable abrasive agent.

Next, after cleaning the polished surfaces, electrodes made of aluminum or the like are provided on both polished end surfaces by thermal spraying, for example, to obtain a zinc oxide element.

In order to obtain the zinc oxide element according to the present invention, the following procedure is performed.

That is, in order to make the dielectric constant of the zinc oxide element 600 or more, Bi2O3, ZnvSb20+□, Zn25iOa generated at the intergranular layer and triple point of the zinc oxide particles after main firing.
Is there a way to reduce the crystals? To this end, it is conceivable to reduce the amount of Bi2O3, 5b203, and 5I02 added to the raw material mixture. Furthermore, it is effective to mix a predetermined amount of Bi2O3 powder and 5b203 powder into the raw material mixture and scatter and remove the Bi2O3 and 5b203 in the intergranular layer during the main firing. Specifically, 1100~
When firing at 1250℃, the temperature inside the kiln is 100-700To
The pressure is reduced to rr to scatter the Bi2O3, 5b203.

In addition, as a method for increasing the dielectric constant of a zinc oxide element to 600 or more, high dielectric constant crystals (titanium oxide rutile crystals, BaT i Oa crystals, PbTiOz crystals, or
There is a method of mixing rTiQ3 crystals) into the raw material powder.

At this time, the average particle size of these crystals is 2 μm or more, and unlike other additives, they are added to the raw materials without being crushed and mixed in a disper mill.

On the other hand, V l w A / V 1゜μ of zinc oxide element
In order to set A to 1.4 to 2.0, a trivalent metal compound such as aluminum is added to the raw material mixture. in this case,
As a trivalent metal compound, A ffi (NOa)3
etc., and the amount added is preferably 0.005 to 0.08 mol%.

Furthermore, the above limiting voltage ratio (V3., A/V1oμA)
As a method of controlling
Another method is to perform heat treatment preferably in an oxidizing atmosphere to turn bismuth oxide in the grain boundaries of the zinc oxide element into γ.

Below, the results of actually measuring various characteristics of zinc oxide elements within and outside the scope of the present invention will be described.

Example 1 812030.3-2.5 mol%, CO2O3 1.0 mol%, MnO20.5 mol%, 5b20. 1.0 mol%, Cr2030.5 mol%, Ni0 1.0 mol%,
51021.0 mol%, Af(NO3) 30.005~
The zinc oxide raw material and the additives were mixed so that 0.1 mol% and the balance consisted of the above zinc oxide raw material, 0.1 wt% of bismuth borosilicate glass was added, and as described above, the zinc oxide raw material and the side surface height were A resistance layer was formed and the main firing was performed to create each voltage nonlinear resistor shown in the table (diameter: 47 mm, height: 22 mm).
．． 5mm, varistor voltage V + A = 6.2 KV
).

However, in order to change the dielectric constant of the zinc oxide element, B1□
The amount of 03 added and the pressure inside the kiln during main firing were varied. Also, the limiting voltage ratio V l-A/V +. In order to change μ5, the amount of AA(NO2)3 added was varied, and after the main firing, heat treatment was performed at 500 to 900'C in an oxidizing atmosphere.

For each zinc oxide element thus obtained, the relative dielectric constant, the flashover voltage in the insulation coordination test, and the rate of change in V I m A after application of lightning surge ΔV. 9. Flatness rate (V4o
KA/V1. A) and the arc extinguishing time (cycle) in the follow-on current interruption test were measured. The measurement results are shown in the table.

The relative dielectric constant was measured according to the JIS K6911 test standard, and the value at a frequency of 1×10'Hz is shown.

For the insulation coordination test, set the series gap 4 spacing to 65
0 mm, an impulse voltage was applied to both ends, and the impulse voltage that caused a flash fault in the series gap was measured. Values in the table are average values of n=10. If the arc horn flashes, the lightning protection function will not work, so this is not possible.

V after lightning surge application. 9 Rate of change ΔV ImA is n=
Prepare 50 test specimens and test them at 120K with a waveform of 4/lOμS.
V Im before and after applying an impulse current of A
The rate of change in A was measured.

For the follow-on current interruption test, 20 of each of the above-mentioned zinc oxide elements of V and A = 6.2 KV were connected to the current limiting element part 3 (see drawing), the series gap length was set to 650 mm, and an AC voltage was applied to both ends. Then, when an impulse voltage was applied and a follow-on current of IA was caused to flow through the current-limiting element portion 3 and the series gap 4, the time (arc extinguishing time: cycle) until the follow-on current was interrupted was measured.

As shown in the table, the dielectric constant and V1mA/
It can be seen that by limiting V1oμ6, the flashover voltage can be lowered, the arc extinguishing time can be shortened, and both ΔVImA and flatness rate can be reduced. In particular, when the arc extinguishing time is 174 cycles or less, it is possible to prevent not only the circuit breaker of the transformer from operating, but also the malfunction of extremely fast-responsive instruments such as computers.

(Effects of the Invention) According to the zinc oxide element for a gap-type lightning arrester according to the present invention, since the dielectric constant of the element is set to 600 or more, the flashover voltage shared by the series gap portion can be reduced. And 1 mA/cm2 and lOμA/c
rn2 and the limiting voltage ratio V1. ．． Since A/VIOμ is set to 1.4 or more, current can flow easily in the small current range. Combined with the above-mentioned limitation on the dielectric constant, it is possible to ensure flashing on the series gap side during lightning strikes, and to prevent contact with the arc horn. Good insulation coordination can be achieved. Therefore, the reliability of the gap-type lightning arrester can be improved and its design margin can be improved.

Furthermore, the above limiting voltage ratio VImA/V+oμ9 is set to 2.0.
Since it is as follows, the follow-on current blocking property can also be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a state in which a gap type lightning arrester is attached to an arc horn. 1... Arc horn 2... Insulator device 3...
・Current-limiting element part 4...Series cap procedure Amendment document flat bottom February 26, 3rd year

Claims (1)

[Claims] 1. A zinc oxide element used in the current limiting element of a gap-type lightning arrester for a power transmission line connected between a power transmission line and the earth, which contains at least bismuth oxide, has a dielectric constant of 600 or more, and 1mA/cm^2 and 10μA/
Limiting voltage ratio V_1_m_A/V_1_0 at cm^2
A zinc oxide element for a gap type lightning arrester, characterized in that μ_A is 1.4 or more and 2.0 or less.