Patent Application
20060279895
1. Field of the Invention
The present invention relates to a lightning arrestor, and particularly relates to a lightning arrestor in which a plurality of zinc oxide elements are stacked, which are to be protected from abnormal voltage such as opening-and-closing surge or lightning surge generated in a circuit of an electric equipment connected to an electric system, and an insulating member formed of an insulating member such as silicone rubber or silicone polymer is covered around the elements as an armor.
2. Description of the Related Art
As a structure of the lightning arrestor in the related art, in which the insulating member formed of the insulating member such as silicone rubber or silicone polymer is covered around the zinc oxide elements as the armor, two types are given in rough classification. That is, two types of structures including a structure where the peripheries of the zinc oxide elements are covered by an insulating cylinder (for example, refer to patent literature 1 and patent literature 2), and a structure where several platelike insulators (for example, FRP) are disposed around the zinc oxide elements (for example, refer to patent literature 3) are given (hereinafter, the former is called insulating cylinder type, and the latter is called insulating plate type).
These lightning arrestors are common in that the insulating cylinder or the platelike insulators is/are disposed around the stacked zinc oxide elements, and the insulating cylinder or the platelike insulators is/are fixed using screws and the like at electrodes placed in both ends of the zinc oxide elements, however, essentially different in pressure relief mechanism of the lightning arrestor. In the insulating cylinder type, circular, elliptical, or slit-like holes or reduced thickness portions are provided in an outer circumferential portion of the insulating cylinder, and such hole portions are designed to have capability for promptly relieving internal pressure generated in the unlikely event that a short-circuit current flows through the lightning arrestor, on the other hand, in the insulating plate type, the insulating plates are disposed with being spaced from each together, and the internal pressure is relieved through spaces among them.
[Patent literature 1]
JP-A-2003-397608 (FIGS. 2 to 4 and p. 3).
[Patent literature 2]
JP-A-6-139858 (FIGS. 1 to 2 and p. 3).
[Patent literature 3]
JP-A-2001-291606 (FIGS. 1 to 2 and pp. 4 to 6).
In the case of the insulating cylinder type, the lightning arrestor has high mechanical strength against bending necessary for a lightning arrestor, and relieves pressure applied to inner faces of the insulating cylinder during relieving the internal pressure of the lightning arrestor from the hole portions provided in the outer circumferential face of the insulating cylinder to reduce the pressure, thereby prevents explosive scattering, and consequently the lightning arrestor is excellent in pressure relief performance. However, the lightning arrestor has a disadvantage of high manufacturing cost because the insulating cylinder is subjected to processing for making the cylinder into a complicated shape. In particular, since manufacturing cost depends on thickness of the insulating cylinder, there is a difficulty that when thickness of the insulating cylinder is excessively increased to improve the mechanical strength or pressure relief performance, manufacturing cost of the insulating cylinder itself is extremely increased.
On the other hand, in the case of the insulating plate type, while manufacturing cost is low, there is a difficulty that mechanical strength against bending is inferior compared with the insulating cylinder type. Therefore, in the case that internal pressure of the lightning arrestor is increased, when excessive force is loaded to the insulating plates, in the worst case, the insulating plates may be broken, or may be blown off together with the screws fixing the insulating plates. When thickness of the insulating plates is increased to prevent this, manufacturing cost is accordingly increased, and consequently low manufacturing cost as the largest merit in the case of using the insulating plate can not be drawn.
In this way, while each of the insulating cylinder type and the insulating plate type has one of merits in respect of the mechanical strength and the manufacturing cost, both conditions of improvement in mechanical strength and low manufacturing cost have been hardly satisfied.
It is desirable to obtain a lightning arrestor that is excellent in pressure relief performance and can be reduced in manufacturing cost while securing bending strength necessary for a lightning arrestor.
In a lightning arrestor according to an embodiment of the invention, a plurality of insulating members having arcuate sections enclosing nonlinear elements are arranged around the nonlinear elements to form a common cylindrical construct provided enclosing the nonlinear elements, and the plurality of insulating members are provided with a predetermined interval to one another in a circumferential direction of the cylindrical construct, and both ends of the plurality of insulating members are fixed to both ends of the nonlinear elements respectively.
Advantage of the Invention
According to the embodiment of the invention, the lightning arrestor can be obtained, which is excellent in pressure relief performance and can be reduced in manufacturing cost while securing the bending strength necessary for a lightning arrestor.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
Embodiment 1
An embodiment 1 according to the invention is described with regard to FIGS. 1 to 6C.
Both ends of the eaves-trough-like insulators 2 are fixed to terminal portions 6A and 6B provided at both ends of the zinc oxide elements 1 by screws 3.
As shown in
Hole portions 4 are provided in two places on an outer circumferential portion of the eaves-trough-like insulator 2 near both ends of the insulator. The hole portions 4 are used for fixing the eaves-trough-like insulator 2. That is, the eaves-trough-like insulators 2 are disposed around the zinc oxide elements 1, and the eaves-trough-like insulators 2 are fixed using screws 3 at electrode portions 6A, 6B disposed at both ends of the zinc oxide elements 1. An aspect of such fixation is shown in
The eaves-trough-like insulators 2 are disposed around the zinc oxide elements 1. As shown in
When the internal pressure is increased, force of pushing the eaves-trough-like insulators 2 to the outside is applied, and thereby excessive load is applied to the screws 3, therefore the eaves-trough-like insulators 2 need to be securely fixed. Thus, inner diameters of the eaves-trough-like insulators 2 are designed to be conformed to an outer diameter of the zinc oxide element 1 to enhance adhesion.
While an interval of the eaves-trough-like insulators 2 may be optionally set, as shown in
In the embodiment 1 according to the invention, while cost necessary for processing is increased because the eaves-trough-like insulators 2 are produced by cutting out from the insulating cylinder TS, the eaves-trough-like insulators 2 are disposed with the interval, thereby weak portions need not be provided on the eaves-trough-like insulators 2 to relieve the gas with increased pressure, therefore processing cost for the insulating cylinder TS itself is eliminated, and consequently manufacturing cost can be relatively reduced. Moreover, since inner surfaces of the insulators are smooth along the diameters of the zinc oxide elements 1 unlike the insulating plates, the insulators are enhanced in adhesion to the zinc oxide elements 1, and easily fixed to the electrode portions 6A, 6B at both the ends of the zinc oxide elements 1, as a result mechanical strength against bending is increased compared with the insulating plates.
According to the embodiment 1 according to the invention, a plurality of insulating members including the eaves-trough-like insulators 2 having arcuate sections enclosing nonlinear elements including the zinc oxide elements 1 are arranged around the nonlinear elements including the zinc oxide elements 1 to form a common cylindrical construct TA, which is provided enclosing the nonlinear elements including the zinc oxide elements 1, and the plurality of insulating members including the eaves-trough-like insulators 2 are provided with a predetermined interval to one another in a circumferential direction of the cylindrical construct TA, and both ends of the plurality of insulating members including the eaves-trough-like insulators 2 are fixed to the terminal portions 6A, 6B provided at both end portions of the nonlinear elements including the zinc oxide elements 1 by clamping by the screws 3 respectively; therefore the lightning arrestor can be obtained, which is excellent in pressure relief performance and can be reduced in manufacturing cost while securing the bending strength necessary for a lightning arrestor.
Embodiment 2
Embodiment 2 according to the invention is described with regard to
The embodiment 2 has the same configurations as in the embodiment 1 described before with regard to configurations other than a specific configuration described herein and exhibits the same operation. In the figure, the same signs indicate equivalent or corresponding portions.
According to the embodiment 2 according to the invention, in the configuration of the embodiment 1, the fixation holes 4 are provided at both ends of the plurality of insulating members including the eaves-trough-like insulators 2, and the pressure relief holes 5A, 5B are provided on the same axis AL as that of the fixation holes 4, therefore the lightning arrestor can be obtained, which is excellent in pressure relief performance and can be reduced in manufacturing cost while securing the bending strength necessary for a lightning arrestor.
Embodiment 3
Embodiment 3 according to the invention is described with regard to
The embodiment 3 has the same configurations as in the embodiment 2 described before with regard to configurations other than a specific configuration described herein and exhibits the same operation. In the figure, the same signs indicate equivalent or corresponding portions.
When the number of cutout from the insulating cylinder TS is small, and consequently the number of the eaves-trough-like insulators 2 is small, since width of the eaves-trough-like insulator 2 is increased (the width is necessarily increased to keep the spaces between the eaves-trough-like insulators 2 constant), fixation of the eaves-trough-like insulators 2 may be necessary to be enhanced. In such a case, a plurality of holes for fixing the eaves-trough-like insulators 2 are provided.
According to the embodiment 3 according to the invention, in the configuration of the embodiment 2, the plurality of fixation holes 4A, 4B and 4C are provided at both ends of the plurality of insulating members including the eaves-trough-like insulators 2, and the pressure relief holes 5A, 5B are provided on the same axis AL as that of the fixation hole 4B in the fixation holes 4A, 4B and 4C, therefore the lightning arrestor can be obtained by reinforcing fixation portions, which is excellent in pressure relief performance and can be reduced in manufacturing cost while securing the bending strength necessary for a lightning arrestor.
Embodiment 4
Embodiment 4 according to the invention is described with regard to
The embodiment 4 has the same configurations as in the embodiment 3 described before with regard to configurations other than a specific configuration described herein and exhibits the same operation. In the figure, the same signs indicate equivalent or corresponding portions.
In the embodiment 4, a form of the pressure relief holes 5A, 5B in the embodiment 3 shown in
When structures described in the embodiments 1 to 3 are applied to a lightning arrestor used for low system voltage in the lightning arrestors in which the peripheries of the stacked zinc oxide elements 1 are covered with silicone rubber, silicone polymer or the like, a hole 5 for enhancing pressure relief capability is acceptable, however, when they are applied to a lightning arrestor used for high system voltage, the short-circuit current is typically increased compared with the low system voltage, and consequently generated internal pressure becomes large, therefore pressure needs to be relieving smoothly and promptly, and therefore relief area is desired to be increased. Therefore, the relief area was increased by changing the shape from the circle to the ellipse to improve the pressure relief capability.
According to the embodiment 4 according to the invention, in the configuration of the embodiment 2 or the embodiment 3, since the hole for enhancing pressure relief capability is formed in an elliptical form as the pressure relief hole 15 shown in
In the embodiments of the invention, configurations described in the following sections (1) to (4) are proposed.
(1) The lightning arrestor in which the insulating cylinder TS is cut out severally in the axial direction to form the eaves-trough-like insulators 2, and then for each of the eaves-trough-like insulators 2, the holes 4 are opened at the points near the ends to allow the insulators to be fixed using the screws 3 at the electrode portions 6A, 6B placed at both ends of the stacked zinc oxide elements 1, and the eaves-trough-like insulators 2 are disposed with an appropriate interval to secure the necessary pressure relief performance.
(2) The lightning arrestor in which the pressure relief hole 5 are provided on the same axis as that of the fixation holes 4 separately from the holes 4 for fixing the eaves-trough-like insulators 2 to improve the pressure relief capability.
(3) The lightning arrestor in which the plurality of holes are provided for fixing the eaves-trough-like insulators 2, and the pressure relief holes 5 are provided on the same axis as that of the fixation holes 4 separately from the holes 4 for fixing the eaves-trough-like insulators 2.
(4) The lightning arrestor in which the holes 5 for relieving increased internal pressure are formed in an elliptical form rather than circular form to improve the pressure relief capability.
In the embodiment according to the invention, the insulating cylinder TS is cut out severally (about 2 to 4 depending on the diameter of the zinc oxide elements 1 to be used) in the axial direction to form the eaves-trough-like insulators 2. Then, the fixation holes 4 are opened at the places near the ends of the eaves-trough-like insulators 2 so that the insulators can be fixed at the electrode portions 6A, 6B placed at both ends of the stacked zinc oxide elements 1. Appropriate spaces are provided between the plurality of eaves-trough-like insulators 2 obtained by being cut out so that the internal pressure generated in the likely event that the short-circuit current flows within the lightning arrestor is promptly relieved through the spaces. To ensure fixation of the eaves-trough-like insulators 2, the inner diameters of the eaves-trough-like insulators 2 are designed to be conformed to the outer diameters of the zinc oxide elements 1 to enhance adhesion. To secure the necessary pressure relief performance, the interval L between the eaves-trough-like insulators 2 is set constant irrespective of the number of the eaves-trough-like insulators 2. Therefore, when the number of the eaves-trough-like insulators 2 is increased, the interval is adjusted by reducing the width of the eaves-trough-like insulators 2.
As a different method from the above, to improve the pressure relief capability, the pressure relief holes 5A, 5B are provided on a surface of the eaves-trough-like insulator 2 separately from the holes 4 for fixing the eaves-trough-like insulator 2. The pressure relief holes 5 are opened near the holes 4 for fixing the eaves-trough-like insulator 2 and on the same axis as that of the fixation holes 4. When the number of the eaves-trough-like insulators 2 is small, since width of the eaves-trough-like insulators 2 is increased, fixation may be necessary to be enhanced. Thus, a plurality of holes for fixing the eaves-trough-like insulator 2 are provided like the fixation holes 4A, 4B and 4C.
As another method, the above methods may be combined. That is, an example where when the number of the eaves-trough-like insulators 2 is small, the plurality of fixation holes 4A, 4B and 4C are provided for fixing the eaves-trough-like insulator 2, and the pressure relief holes 5A, 5B are provided on the surface of the eaves-trough-like insulator 2, and an example where the pressure relief holes 5A, 5B for relieving internal pressure is formed elliptically like the pressure relief hole 15 shown in
While the presently preferred embodiments of the present invention have been shown and described. It is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-170353 | Jun 2005 | JP | national |
