JPS6024544B2 - Lightning arrester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gapless sealed lightning arrester using a resistor with excellent nonlinear characteristics, and particularly to a current rejector that can improve internal potential distribution.

An example of a conventional device of this type is shown in FIG. 1 and will be explained as follows.
In the figure, 1 is a grounded tank, and the interior 2 of this grounded tank 1 is filled with a gas having high dielectric strength, for example SF6.

Reference numeral 3 denotes a resistor having excellent non-linear characteristics, which is made of, for example, a laminate of zinc oxide crystals.

4 is a conductor that serves as the high voltage side lead wire, 5 is this conductor 4
8 is an insulating material supporting the resistor 3 and the conductor 4.
is the total length of the resistor 3, D is the inner diameter of the resistor 3, and Do is the inner diameter of the ground tank 1.

In a lightning arrester having such a configuration, first, the conductor 4 is connected to a high-voltage terminal of the equipment to be protected, and a surge caused by lightning or the like is grounded through the resistor 3. Next, an example of the voltage-current characteristics of the zinc oxide sintered element used as the resistor 3 is shown and explained in Fig. 2. In Fig. 2, the horizontal axis represents the current A, and the vertical axis represents the voltage V. FIG. 2 is an explanatory diagram of the operation of FIG. 1; Due to such a wide range of constant current characteristics, the increase in terminal voltage due to the above-mentioned surge can be suppressed to a low level. Here, the solid line A in Figure 2 shows the characteristic curve for direct current or large current surge, but when an alternating current voltage is applied to such an element, the voltage-current characteristic is considered at the peak of both current and voltage. As shown by the dashed line in FIG. 2, in the small current region, the effect differs from that for DC voltage. This is because the element has capacitance, and is a characteristic common to other nonlinear resistors including zinc oxide dawn stripe elements. Note that C indicates a surge. For AC voltages that are higher than a certain level, the voltage
The current characteristics are the same as those of direct current shown in solid line A. That is, in FIG. 2, above the voltage Vo, both AC and DC curves are approximately the same, but below the voltage yo, the two curves diverge. Here, in the zinc oxide competitive element, the current value for this voltage Vo is usually 1 skin A or more. V
p is the level of normal mine pressure. However, in an AC current arrester, an AC line voltage is always applied to the non-linear resistor.

This normal ground voltage is selected to be a voltage lower than the voltage Vo, for example, the level shown as Vp in FIG. 2, in view of the life span of the element, which will be described later. For such low AC voltages, the device behaves almost as a perfect capacitor, causing the following problems. That is, the first
In the structure shown in the figure, there is a stray capacitance between the resistor 3, which has excellent non-linear characteristics, and the ground tank 1. Taking this into consideration, it is necessary to Regarding voltage, the potential sharing of non-linear resistors can be discussed using an equivalent circuit as shown in FIG.

In Fig. 3, the mark is the total length of the resistor 3 shown in Fig. 1, x
is the distance from the high voltage end to the point being considered, dx is the differential distance for the following differential calculation, K/dx is the capacitance of the element at the length dx, and Cdx is the length at the side. The capacitance v (text) between it and the grounded tank 1 is the potential of the non-traffic line resistor at the point of distance x with respect to the total voltage V. And between these, V(X)-CdX=magazine [volume]-d
If we consider that there is a relationship of X - device

Boundary conditions for kneading v(0) = V, v(H) = 0 Solving under is found.

The potential distribution v(x) of this resistor has a shape as shown by the solid line A in FIG. 4a, which is different from the linear potential distribution shown by the broken line. As can be seen from the above equation, the "deviation" from the linear potential distribution increases as the length of the resistor increases. As a result, the electric field inside the resistor E(x) = [dv
(x)/■] becomes extremely non-uniform as shown by the solid line A in FIG. 4B.

The maximum electric field occurs on the high voltage side (x=0), and the electric field Emax at that point is extremely high compared to the average electric field Eav. Under such a situation, the portion of the nonlinear resistor close to the high voltage side is in an overvoltage state that is higher than the level of the normal anti-mine pressure Vp shown in FIG. If such an overvoltage is constantly applied to an element, the element generally deteriorates electrically. FIG. 5 is a characteristic diagram showing an example of a voltage-life curve of a zinc oxide element.

In the figure, the curve A indicates high temperature, and the curve end indicates low temperature. As is clear from the figure,
As the voltage approaches Vo, the life span rapidly shortens. Therefore, in the conventional construction method of the torpedo torpedo device, there was a drawback that the normal ground voltage was biased toward the high voltage side, and the nonlinear resistor in that portion rapidly deteriorated. In view of the above points, the present invention has been made to solve such problems and eliminate such drawbacks.The purpose of the present invention is to create a structure in which a high voltage conductor can be connected from the side of the earth protection layer.
It is possible to omit the bending parts required to connect busbars and lightning arresters in gas-insulated substations, and the cost of this part can be significantly reduced.In addition, the simple internal structure allows for constant AC voltage resistance. Since the potential distribution of the resistor can be made uniform, the life of the device can be significantly extended, and a highly reliable snow removal device can be obtained.Furthermore, there is no need to add a voltage dividing capacitor. Another object of the present invention is to provide a current protection layer that can reduce the size of a lightning arrester.

In order to achieve such an object, the present invention provides a grounded tank, a high voltage conductor insulated and supported on the side surface of the grounded tank, and an electrical connection in series between the high voltage conductor and the inner wall of the grounded tank. a non-linear resistor inserted and divided into at least two units, a high voltage side and a low voltage side; a first shield provided on the high voltage side of the high voltage side unit connected to the high voltage conductor; a second shield provided on the high voltage side of the low voltage side unit directly connected to the grounding tank; a connecting conductor connecting the low voltage side of the high voltage side unit and the high voltage side of the low voltage side unit; and the first and second shields are inverted with respect to the low-pressure side unit of the high-pressure side unit and are arranged between the low-pressure side unit and the high-pressure side unit and the low-pressure example thereof. The unit is arranged to have a capacitance between the unit and the high voltage conductor.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 6 is a cross-sectional side view showing an embodiment of the earth protection layer according to the present invention, and shows an example of a lightning arrester having a structure of a cylindrical hammer-shaped ground tank with a high-voltage conductor attached to the side surface. In the figure, 6 is a cylindrical hammer-shaped grounding tank, 7 is a high voltage conductor (hereinafter referred to as high voltage conductor) insulated and supported by an insulating material spacer 5 on the side surface of this grounding tank 6, and 8 and 9 are a large number of housing units. The non-linear resistor is divided into two units, a high-voltage side and a low-voltage side, and is electrically inserted in series between the high-voltage conductor 7 and the inner wall of the grounded tank 6.
1 River is a medium voltage conductor. In addition, there are shields Sa and Sb that also serve as connection parts at both ends of the unit of non-linear resistor 8, and a shield Sc that also serves as a connection part on the upper side of the unit of non-linear resistor 9. This shield Sa is connected to high-voltage conductor 7. The shield Sb and the shield 8c are connected to the medium voltage conductor 10.
connected via. Here, this medium voltage conductor 10 constitutes a connection conductor that connects the low voltage side of the high voltage side unit and the high voltage side of the low voltage side unit. Then, the high-voltage side unit connected to the high-voltage conductor 7 is connected in the opposite direction to the low-voltage side unit directly connected to the other grounded tank 6, and the electrostatic charge between the low-voltage side unit, the high-voltage side unit, and the high-voltage conductor is Configured to increase capacity. That is, the high-voltage side unit connected to the high-voltage conductor 7 is inverted with respect to the low-voltage side unit directly connected to the ground tank 6, and the shields Sa and Sc are faced to form the low-voltage side unit and the high-voltage side unit. The high voltage conductor 7 is arranged so as to have a capacitance Ca between the high voltage conductor 7 and between the low voltage side unit and the high voltage conductor 7. Here, the nonlinear resistors 8, 9
The high-voltage and low-voltage side units do not need to be divided into two equal lengths, and the division ratio may be set by voltage sharing or the like. FIGS. 7a and 7b are characteristic diagrams for explaining the operation of FIG. 6, which show the potential distribution and electric field distribution of the nonlinear resistor with respect to the current and voltage that are constantly applied and released.

In FIG. 7a, the solid line A indicates the potential distribution of the non-linear resistor, and the broken line indicates the ideal linear potential distribution. 7th
In Figure b, the solid line A indicates the electric field distribution of the non-linear resistor, and the dashed line indicates the average electric field distribution. Next, the operation of the embodiment shown in FIG. 6 will be explained with reference to FIG.

First, in response to surges caused by lightning, etc., the nonlinear resistor 8
, 9 becomes lower, the rise in terminal voltage is suppressed,
In this case, since each resistor has approximately the same value, the voltage applied to each resistor is approximately equal even if it is divided into two.
On the other hand, for an alternating current voltage that is constantly applied, only a small current flows through the resistor. Here, in a commercial frequency power torpedo device to which alternating current is constantly applied, the capacitance is determined by the capacitance of the resistor, as described above. In the embodiment shown in FIG. 6, the nonlinear resistors 8 and 9 are divided into two units, one on the high voltage side and one on the low voltage side, and their shields Sa and Sc are brought close together so that the capacitance Ca between them can be increased. In addition, the connection of the unit of the non-linear resistor 8 is reversed. Now, if such a configuration is explained using the equivalent circuit shown in FIG. Capacity C
This is equivalent to connecting a. And this capacitance Ca
As the voltage increases, the potential of the shield Sc approaches the potential of the high voltage conductor 7 and the shield Sa than in the arrangement shown in FIG.

That is, the potential distribution v of the nonlinear resistor in this example
It can be seen that (x) has a shape as shown by the solid line A in FIG. In this case, the peak of potential shown by C on the curve of solid line A is due to the effect of capacitance Ca that appears characteristically in this embodiment, and has a very large effect of making the entire potential distribution close to linear. Further, the electric field distribution E(x) of the non-linear resistor in this embodiment has a shape as shown by the solid line A in FIG. 7B, and is quite close to the average electric field distribution Eav shown by the broken line. In addition, in this embodiment, since the shield Sa of the high voltage part is located near the center of the ground tank 6, the electric field distribution in the ground tank 6 is considerably gentler than in the structure shown in FIG. 1, and is non-linear. The overall potential distribution of the resistor can also be greatly improved. Note that the potential and electric field distributions obtained in these characteristic diagrams differ from the ideal distribution, but this "deviation" is not necessarily a problem in practice, and it is sufficient as long as it is within a certain tolerance range. . Therefore, as shown in the embodiment shown in FIG.
Since the potential at 0 is maintained at approximately half of 50%, the voltage between shields Sa and Sc, between shield Sa and medium voltage conductor 10 and ground tank 6, and between shield Sb and ground tank 6 is about the total ground voltage. It only adds 50%.

Therefore, the insulation distance can be made relatively short, and the device can be made into a four-dimensional structure. FIG. 8 is a cross-sectional side view showing another embodiment of the present invention. In FIG. 8, the same parts as in FIG. 6 are given the same reference numerals, and their explanation will be omitted. B,
, & indicate small bar-shaped shields, and Cb, , Cb2 indicate capacitance. Here, the difference from FIG. 6 is that a shield S is provided at one end of the nonlinear resistor 8 and also serves as a connection part.
a and the shield Sc which is provided above the non-linear resistor 9 and also serves as a connection part, and a small rod-shaped shield B,
, B2, and this shield B, & and the nonlinear resistor 8
, 9, the potential distribution and electric field shown in FIG. 7 are made more uniform. Incidentally, since the shields B, , B can be cut into 4 pieces, the support structure becomes easy. In the above example,
In both cases, the case where the non-linear resistor is divided into two units has been explained, but the present invention is not limited to this, and it is also possible to further increase the number of divisions and connect each of them with a connecting conductor. Generally, the larger the number, the closer the potential distribution of the nonlinear resistor can be to a linear one.

As is clear from the above explanation, according to the present invention, it is possible to create a structure in which a high voltage conductor can be connected from the side of the Shiden equipment platform, so that the bent portions necessary for connecting the busbar and the earth protection equipment layer in a gas-insulated substation can be can be omitted, which has the advantage of significantly reducing the cost of this part.

Furthermore, according to the present invention, the potential distribution of the resistor under constant alternating current voltage can be made uniform with a simple internal structure, so that the life of the device can be significantly extended, and a highly reliable earth-protection system can be provided. You can get a hawk. Furthermore, since there is no need to add a voltage dividing capacitor, the lightning arrester can be downsized. Thus, according to the present invention,
This device has many advantages over conventional devices of this type, and is unique as a sealed lightning arrester device that makes the potential distribution of the non-linear resistor uniform.

[Brief explanation of drawings]

Figure 1 is a cross-sectional side view showing an example of a conventional lightning arrester;
The figure is a voltage-current characteristic diagram of the zinc oxide competitive element used to explain the operation of Figure 1, Figure 3 is an equivalent circuit diagram of Figure 1, and Figures 4a and b are used to explain the operation of Figure 1. FIG. 5 is a characteristic diagram showing an example of the voltage-life curve of the zinc oxide competitive element used to explain the operation of FIG. 1, and FIG. 6 is a characteristic diagram showing the potential distribution and electric field distribution of the resistor. 7a and 7b are characteristic diagrams showing the potential distribution and electric field distribution of the resistor for explaining the operation of FIG. 6, and FIG. 8 is a cross-sectional side view showing one embodiment of the electrical equipment calendar. It is a cross-sectional side view showing an example. 6...Grounding tank, 7...High voltage conductor, 8
, 9... Non-linear resistor, 10... Medium voltage conductor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1 A grounded tank, a high voltage conductor insulated and supported on the side surface of this grounded tank, and at least two conductors electrically inserted in series between this high voltage conductor and the inner wall of the grounded tank, on the high voltage side and the low voltage side. A non-linear resistor divided into two units,
A first shield provided on the high voltage side of the high voltage side unit connected to the high voltage conductor, and a second shield provided on the high voltage side of the low voltage side unit directly connected to the ground tank. and a connecting conductor connecting the low voltage side of the high voltage side unit and the high voltage side of the low voltage side unit, and the high voltage side unit is inverted with respect to the low voltage side unit, and the first and a second shield is arranged to face each other so as to have a capacitance between the low voltage side unit and the high voltage side unit and between the low voltage side unit and the high voltage conductor. Characteristic lightning arrester.