JPS6187301A - Lightning arrestor - 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] [Industrial Field of Application] This invention relates to a zinc oxide type lightning arrester, especially its inner features! (This relates to a lightning arrester in which the arrangement of the non-linear resistance elements to be accommodated is ingenious.

[Conventional technology]

Lightning arrester is 1! suppresses abnormal voltages that occur in power systems,
Prevent insulation breakdown accidents of various protected devices connected to the grid. In general, lightning arresters discharge current when a certain overvoltage level is reached, and do not operate at a certain voltage level such as normal operating voltage, exhibiting characteristics similar to ordinary insulators.

Zinc oxide type lightning arresters are currently the mainstream type of lightning arrester, and a typical example thereof will be described. Third
The figure is a side sectional view showing an insulator-shaped zinc oxide type lightning arrester. In figure 1, C (1) is an insulator tube container, which has flanges (2) at both ends.

(3) is a non-linear resistance element column constructed by connecting in series a plurality of non-linear resistance elements (,?/) to (3n) made of a sintered body of metal oxide whose main component is zinc oxide. .

This non-linear resistance element column (3) is fixed to the sealing lid Cj via a spring (4'l) with spring pressure.

Next, the operation will be explained. When an abnormal voltage such as a lightning surge hits the lightning arrester shown in Fig. 3, the resistance of the non-linear resistance element column (3) becomes significantly smaller against the overvoltage, and the sealing cover (!r) and spring A surge current is caused to flow through (lI), thereby suppressing the overvoltage below a fixed level. On the other hand, after abnormal voltage suppression, non-direct 1liI
i! Since the resistance of the resistive element pillar (<3) becomes very high, the nonlinear resistive element pillar (3) exhibits characteristics close to those of an ordinary insulator. For such normal continuous operating voltages, the voltage distribution within the lightning arrester will affect the energized life and thermal stability of the lightning arrester.

This characteristic will be explained below using figures.

FIG. 7 is a circuit diagram showing an equivalent circuit of the lightning arrester shown in FIG. ). and C (3i to Cef1 are each nonlinear resistance element (
Cst % C
ss is the ground floating capacitance. It depends on the shape and size of the lightning arrester, but in general, the i! In lightning equipment, the parallel capacitance of ground stray capacitance Cst - C5J? The value is much greater than the 100 series static response value of the capacitance Ce1-Cea of each non-linear resistance element. Further, at normal continuous operating voltages, the capacitance i1J actance due to the capacitance of each nonlinear resistance element is smaller than the resistance of each nonlinear resistance element.

It ranges from several percent to about 20 percent. For this reason, at a normal continuous operating voltage, the voltage distribution of the non-linear resistance element pillar 3 becomes unequal due to the V effect of the stray capacitance to ground Cst to Cs,y. That is, as can be seen from the equivalent circuit in Figure 1I, if the current flowing through each non-linear resistance element is Iel~Ie<+, the higher the voltage side, the larger the current Ie flowing through the non-linear resistance element, and the resulting voltage drop will also be This is because it becomes bigger.

Figures 3(a) and (bl respectively show the potential distribution characteristics of the non-linear resistance element column (1) and the voltage characteristics per element of the device shown in Figure 3:/C. Assuming that there is no stray capacitance Cst % C5J, the resulting voltage sharing is equal, and it can be seen from FIG. 5(b) that the voltages applied to each non-linear resistance element column are equal at continuous operating voltages. However, if stray capacitance to ground is included, each broken line curve becomes a solid line curve with unequal voltage distribution, and as shown in @!r figure (b), the nonlinear resistance element on the high voltage side is A large voltage will be applied.

[Problem that the invention seeks to solve]

In this way, if the voltage distribution of the lightning arrester is unequal, a voltage higher than the set value will be applied to some non-linear resistance elements, causing significant deterioration of the non-linear resistance elements in these parts. In turn, this could shorten the lifespan of the entire lightning arrester and deteriorate its thermal stability. For this reason large rated lightning arresters.

Adding a voltage dividing capacitor to equalize voltage sharing,
Since a large partial pressure shield is required, there is a problem that the device becomes large and expensive.

The present invention was made to solve these problems, and an object of the present invention is to obtain a lightning arrester in which each nonlinear resistance element shares a uniform voltage.

[Means for solving problems]

The lightning arrester according to the present invention has a non-linear resistance element having a large ratio VNmA/Zc arranged on the high voltage side.

[For production]

In this invention, by arranging non-linear resistance elements with a large ratio vNm/Zc on the high voltage side and arranging them in order from the high voltage side to the ground side, the voltage distribution of the lightning arrester becomes equal. , [Example] The concept of this invention will be explained below with reference to the drawings. Second
The figure is a diagram showing voltage-current (VI) characteristics of each nonlinear resistance element. In order to correspond to the lightning arrester series gap,
The operation start voltage is set, and it is the current NmA (
Normally, a current of 1 to JmA is used). This VI characteristic is.

Wide current range, especially OKA (,・), has excellent nonlinearity with little voltage change, and in this region, even if nonlinear resistance elements are manufactured in large quantities, The same stable V-I curve is obtained.On the other hand, NmA
The following is the V-I characteristic in the small current region.

It does not show much non-linearity, and when the element size IF bursts, there is a large variation as shown by diagonal lines in Figure 1.

This is about ±2Q% at maximum for the same voltage.

On the other hand, the life of the non-linear resistance element when applied with electricity depends on the ratio of the continuous operating voltage and the operation start voltage shown in FIG. 1, that is, the application rate P. Generally, when the charging rate P increases by 10%, the charging life per charging is approximately 1
It is said that the lifetime of the lightning arrester can be increased by an order of magnitude, and one way to extend the life of the lightning arrester is to eliminate the inequality in the voltage distribution of the lightning arrester and use it at a constant average charge rate.

This invention utilizes such characteristics of non-linear resistance elements. First, the operation start voltage VNmA of each nonlinear resistance element is measured. The average value divided by the number of medical elements) is used to measure leakage current. Then, the impedance Zc is determined from the ratio of the two. From the Zc thus obtained and the VNmA mentioned above, the ratio -Nv.c is further calculated as follows.

Here, the ratio vxmA/Zc is an index that determines the application of the nonlinear resistance element, and the idea of the present invention is that the element having a larger value is placed at a location with a higher duty ratio.

The derivation of this ratio will be explained below. Operation starts when the pressure is vNm and a continuous working voltage (P x VNz *) is applied to the nonlinear resistance element of impedance Zc.

If the current flowing through the non-linear resistance element is Ie, a linear relationship holds true.

Zc When P is transferred, Zc Here, in order to make the charging rate P of each non-linear resistance element of the lightning arrester constant, it is necessary to establish a zero-order equation with P=constant.

vNm oct 6 Zc As mentioned about the equivalent circuit in Figure 7, if the nonlinear resistance element with a high voltage share on the high voltage side is placed with another nonlinear resistance element with a large voltage, the above equation will be satisfied. Is possible.

The structure of the lightning arrester according to the present invention is exactly the same as that shown in FIG. 1, and the effect of suppressing abnormal voltages such as lightning surges does not change at all.

Next, the voltage sharing characteristics of the lightning arrester according to the present invention at normal continuous operating voltage will be explained. Figure 1(a),
(b) is the nonlinear resistance element column (3) in the present invention.
These are an example of the voltage sharing characteristics of , and are the voltage distribution characteristics and the voltage characteristics per element, respectively. The solid line in the figure shows the case where nonlinear resistance elements are arranged in order from the high voltage side to the ground side, starting with the ratio VgIA/Zc. In comparison T, the voltage applied to the non-linear resistance element in the high voltage side portion becomes significantly smaller, and exhibits characteristics similar to the case of equal voltage sharing as shown by the broken line.

Furthermore, as another embodiment, the same effect can be obtained by using the capacitance -1i 1J actance l/ωCe of the non-linear resistance element in place of the above-mentioned Zc. This is because the resistance of the nonlinear resistance element is sufficiently larger than l/ωCe near the normal continuous operating voltage and can be ignored.

〔Effect of the invention〕

In the present invention, as explained above, by increasing the voltage of the lightning arrester, the voltage distribution of the lightning arrester becomes equal, and some of the non-linear resistance elements with a high charge rate are prevented from being significantly deteriorated by the charge. About this.

Not only does it extend the energized life of the entire lightning arrester, but it also improves its thermal stability, and for lightning arresters with large ratings! This has the effect that the capacitance of the voltage dividing capacitor for equalizing the voltage distribution can be made smaller, and that a small voltage dividing shield can be used.

[Brief explanation of drawings]

Figure 1 shows the voltage distribution characteristics (a) of the nonlinear resistance element pillar in the lightning arrester according to the present invention and the voltage characteristics per element (b).
Figure 2 shows the voltage-current of each non-linear resistance element (
V-I) A diagram showing the characteristics, Figure 3 is a side cross-sectional view showing the lightning arrester currently in use, Figure 3 is a circuit diagram showing the equivalent circuit of the lightning arrester shown in Figure 3, and Figure 3 is the conventional lightning arrester. It is a diagram showing the voltage distribution characteristics (at) and the voltage characteristics (b) per element of the nonlinear resistance element pillar in the lightning arrester. In the figure, (3) is the nonlinear resistance element pillar, (31) to (
3n) is a non-linear resistance element, V is the operation start voltage of the non-linear resistance element, and Zc is the impedance of the non-linear resistance element. Note that the same reference numerals in each figure indicate the same or corresponding parts. Rod 1 figure (Q) (b) Atsushi 2 figure!

Claims (4)

[Claims] (1) Measured operation of each nonlinear resistance element in a lightning arrester equipped with a nonlinear resistance element column configured by connecting multiple nonlinear resistance elements in series, each made of a metal oxide whose main component is zinc oxide. The impedance Z is determined from the starting voltage V_N_m_A and the leakage current measured at a given voltage.
c, and further calculate the ratio V from these V_N_m_A and Zc.
_N_m_A/Zc is determined, and a nonlinear resistance element having a large ratio is arranged on the high voltage side of the lightning arrester. (2) From the high voltage side of the lightning arrester to the ground side, the ratio V_N_
2. The lightning arrester according to claim 1, wherein the nonlinear resistance elements are arranged in order of increasing m_A/Zc. (3) Claim 1 or 2, characterized in that the predetermined voltage for measuring leakage current is a continuous use voltage.
Lightning arrester as described in section. (4) The lightning arrester according to claim 1 or 2, characterized in that the capacitive reactance 1/(ωCe) of the nonlinear resistance element is used in place of Zc.