Polymer insulator apparatus and method of mounting same

The cantilever and compression strength of a polymer post insulator decreases according to lengthening of lever length of the polymer post insulator. By combining polymer post insulators to construct a structure having an increased strength in an arbitrary direction, a polymer insulator apparatus and a method for mounting the same can provide a sufficient strength and rigidity even as a long insulator for high voltage that requires a long insulation distance. Polymer post insulator columns 12-1, 12-2, in which plural polymer post insulators 1-1 to 1-4 are stacked, are arranged in parallel. The polymer post insulator columns 12-1, 12-2 arranged in parallel are connected with each other via connecting plates 13-1 to 13-3 at each connection site of the polymer post insulators 1-1 to 1-4 constituting the polymer post insulator columns 12-1, 12-2 as well as at the top and bottom of the polymer post insulator columns 12-1, 12-2. Thus, the cantilever strength in a direction of arranging the polymer post insulator columns 12-1, 12-2 in parallel is increased, and also the compression strength in a direction of stacking the polymer post insulators 1-1 to 1-4 is increased.

REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Application 2002-380961 filed Dec. 27, 2002, the entireties of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a post insulator that receives a large compression load by supporting an electric conductor, a switching device, or the like, for example, in a substation. In particular, the present invention relates to an insulator apparatus constituted with polymer post insulators and to a method of mounting the same.

2. Description of the Background Art

Hitherto, since post insulators used in a substation not only support an electric conductor but also are structural members constituting a transformer apparatus, a high rigidity is required and also, in a post insulator that supports an opening/closing part of a switching device, a strict position control is required in order to ensure an accurateness in repetition of switching operation. For this reason, insulators made of porcelain being excellent in rigidity have been used as station posts. However, insulators made of porcelain are brittle, and are not durable against a dynamic stress such as generated in a large earthquake or the like. Polymer post insulators are constructed with a solid FRP core for supporting mechanical load such as cantilever and compression, an outer cover having a weather resistance such as a silicone rubber for protecting the FRP core and imparting a suitable leakage distance to the insulator, and metal fitting pieces for connecting the insulator to a supporting structure and to an electric conductor or the like. Since polymer post insulators are excellent in earthquake-proof characteristics and contamination-proof characteristics, polymer post insulators are more and more widely used in recent years as insulators for a substation chiefly in coastal areas that often suffer from earthquake and severe contamination.

While porcelain post insulators are little deformed, the aforementioned polymer post insulators are deformed by being deflected against cantilever load and are deformed by being buckled against compression load. Such deformations increase according as the insulators increase in length, and also the strength decreases according as the insulators increase in length. For this reason, in application of polymer post insulators for substations, insufficient rigidity of the polymer post insulators is a problem particularly for high voltage that requires a long insulation distance.

An object of the present invention is to solve the aforementioned problems of the prior art and to provide a polymer insulator apparatus that can increase the strength in a desired direction and can be applied to a station post for high voltage that requires a long length and to a method of mounting the same.

SUMMARY OF THE INVENTION

A polymer insulator apparatus according to the present invention is such that polymer post insulator columns, in which plural polymer post insulators are stacked, are arranged in parallel, and the polymer post insulator columns arranged in parallel are connected with each other via a connecting plate at each connection site of the polymer insulator constituting the polymer insulator columns as well as at the top and bottom of the polymer post insulator columns, whereby the cantilever strength in a direction of arranging the polymer post insulator columns in parallel is increased, and also the compression strength in a direction of stacking the polymer post insulators is increased.

A method of mounting a polymer insulator apparatus according to the present invention is such that, in mounting the above-described polymer insulator apparatus vertically onto a base, the polymer insulator apparatus is mounted so that the direction of arranging the polymer post insulator columns in parallel will be a direction of cantilever load and the direction of stacking the polymer post insulators will be a direction of compression load.

In the present invention, polymer post insulator columns, in which plural polymer post insulators are stacked, are arranged in parallel, and the polymer post insulator columns arranged in parallel are connected with each other via a connecting plate at each connection site of the polymer insulator consisting the polymer insulator columns as well as at the top and bottom of the polymer post insulator columns. Therefore, in mounting the above-described polymer insulator apparatus vertically onto a base, the polymer post insulator apparatus can be mounted so that the direction of arranging the polymer post insulator columns in parallel will be a direction of cantilever load and the direction of stacking the polymer post insulators will be a direction of compression load. For this reason, the strength in the direction of cantilever load and the strength in the direction of compression load in particular can be improved.

Of course, the strength in a desired direction can be improved by setting the direction of parallel arrangement of the polymer post insulator columns to be an arbitrary direction. Also, the strength in a direction other that the direction of improved strength can be improved as compared with the strength in a case of a single polymer post insulator, though the improvement is not great as in the direction of improved strength. Further, the polymer insulator apparatus according to the present invention is constructed in such a manner that polymer post insulator columns, in which plural polymer post insulators are stacked, are arranged in parallel, and the polymer post insulator columns arranged in parallel are connected with each other via a connecting plate at each connection site of the polymer insulator constituting the polymer insulator columns as well as at the top and bottom of the polymer post insulator columns. Therefore, a long polymer insulator apparatus can be obtained easily while maintaining the diameter of the FRP core of each polymer post insulator constituting the polymer insulator apparatus to be of the same degree as in the prior art.

Furthermore, in a preferable mode, the polymer post insulator columns are arranged in parallel in the direction of the cantilever load generated by opening and closing of a switching device. Disposing the polymer post insulator columns in such a manner is preferable because of the following reason. When a switching device of a substation is constructed with the polymer insulator apparatus of the present invention, the cantilever load imposed upon the top by an operation of the opening/closing part is applied in the direction of great improvement of the strength of the polymer insulator apparatus. Therefore, a sufficient position precision can be maintained against a larger cantilever load, and also the polymer insulator apparatus can exhibit a sufficient strength against the compression load imposed upon the polymer insulator apparatus by placing the opening/closing part thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a view showing one construction example of a polymer post insulator constituting a polymer insulator apparatus according to the present invention. In the example shown inFIG. 1, a polymer post insulator1is constituted with a core member2, an outer cover5constructed by a sheath3and sheds4disposed around core member2, and holding metal fitting pieces6disposed at two ends of core member2. Further, core member2is made of a solid FRP, and outer cover5constructed by sheath3and sheds4is made of, for example, silicone rubber. Also, an end of holding metal fitting piece6has a flange shape, and is constituted to be capable of being fixed onto a planar plate member or the like with screws. The construction of this polymer post insulator is the same as in the prior art.

FIG. 2is a view showing one example of a polymer insulator apparatus according to the present invention. In the example shown inFIG. 2, a polymer insulator apparatus11according to the present invention is constructed in such a manner that polymer post insulator columns12-1,12-2, in which a plurality of (here, two) polymer post insulators1-1,1-3and1-2,1-4are stacked, are arranged in parallel, and polymer post insulator columns12-1,12-2arranged in parallel are connected with each other via connecting plates13-1to13-3at each connection site of polymer post insulators1-1to1-4constituting the polymer post insulator columns12-1,12-2and at the top and bottom of the polymer post insulator columns12-1,12-2.

The connection between polymer post insulators1-1,1-2and connecting plate13-1at the bottom of polymer insulator apparatus11is achieved by fixing the flange-shaped parts located at the end of holding metal fitting pieces6-1,6-2of polymer post insulators1-1,1-2onto connecting plate13-1with screws. Similarly, the connection between polymer post insulators1-3,1-4and connecting plate13-3at the top of polymer insulator apparatus11is achieved by fixing the flange-shaped parts located at the end of holding metal fitting pieces6-3,6-4of polymer post insulators1-3,1-4onto connecting plate13-3with screws. Further, the connection between polymer post insulators1-1to1-4and connecting plate13-2at the connection site of polymer insulator apparatus11is achieved by disposing flange-shaped holding metal fitting pieces6-1to6-4located at the end of polymer post insulators1-1to1-4via connecting plate13-2with holding metal fitting pieces6-1and6-3and holding metal fitting pieces6-2and6-4respectively forming pairs, and integrally fixing the set of holding metal fitting piece6-1, connecting plate13-2, and holding metal fitting piece6-3and the set of holding metal fitting piece6-2, connecting plate13-2, and holding metal fitting piece6-4set by set with screws.

Regarding the cantilever strength of polymer insulator apparatus11of the present invention constructed as shown inFIG. 2, when a cantilever load (shown by arrow A) is applied to connecting plate13-3at the column top with connecting plate13-1fixed and polymer insulator apparatus11standing upright, the apparatus exhibits a high strength because of having a rigid frame structure in which polymer post insulators1-1to1-4arranged in parallel and connected with each other are stacked.

When compression load (shown by arrow B) off the central axis of the polymer post insulator is applied to a single polymer post insulator1shown in FIG.3A and to a polymer post insulator column12-1shown in FIG.3B, in which a plurality of (here, two) polymer post insulators1-1and1-3are stacked, via a structure21supported by polymer post insulator1or polymer post insulator column12-1, a column top buckling mode such as shown inFIG. 4Awill appear where the buckling strength against the compression load is approximately equal to the formula obtained by Euler's buckling theory: W=(¼)·π2EIz÷L2. Here, W, π, E, Iz, and L represent the buckling load, circle circumference diameter ratio, elastic modulus, area moment of inertia, and length of the column, respectively.

When compression load (shown by arrow C) is applied to a single polymer post insulator1shown in FIG.3A and to a polymer post insulator column12-1shown inFIG. 3B, in which a plurality of (here, two) polymer post insulators1-1and1-3are stacked, onto the central axis of polymer post insulator1or polymer post insulator column12-1, a column center buckling mode such as shown inFIG. 4Bwill appear where the buckling strength against the compression load is approximately equal to the formula obtained by Euler's buckling theory: W=π2EIz÷L2.

Therefore, even with the same polymer post insulator column, when the buckling mode assumes the column center buckling mode, the polymer post insulator column exhibits compression strength four times as large as the compression strength when the buckling mode assumes the column top buckling mode.FIG. 4Cshows a phase of buckling deformation in the case of a structure in which two columns are arranged in parallel with both ends thereof fixed, i.e. the case where compression load is applied onto the central axis of the rigid frame structure. If the column length L remains the same, the exhibited buckling strength is two times as large as that of the column center buckling mode of one column shown in FIG.4B and is eight times as large as that of the column top buckling mode of one column shown in FIG.4A.

In polymer insulator apparatus11of the present invention constructed as shown inFIG. 2, polymer post insulator column12-1, which is constructed with polymer post insulators1-1and1-3, and polymer post insulator column12-2, which is constructed with polymer post insulators1-2and1-4, are arranged in parallel; the top and the bottom thereof are connected with connecting plates13-1and13-3; and the central part of the columns are connected and fixed with connecting plate13-2. By the function of connecting plate13-2located at the central part, the deformation of column center buckling shown inFIG. 4Ccan be completely restrained.

Therefore, when compression load is applied to polymer insulator apparatus11, each of polymer post insulators1-1to1-4assumes the column center buckling mode, so that the length of the column applied to Euler's formula will be the length of individual polymer post insulators1-1to1-4, which is about half of the length of polymer insulator apparatus11. As is apparent from Euler's formula, the buckling strength thereof is inversely proportional to the square of the length L of the column. Thus, when the length of the column becomes, for example, half of the original length, the buckling strength will be the inverse of the square of half, which is four times the original buckling strength. Therefore, the buckling strength of polymer insulator apparatus11shown inFIG. 2is, with respect to a column having a similar column length L, eight times as large as the buckling strength of the column center buckling mode of one column shown inFIG. 4B, and thirty two times as large as the buckling strength of the column top buckling mode of one column shown in FIG.4A.

In order to obtain a buckling strength of the same degree as that of polymer insulator apparatus11of the present invention by using single polymer post insulator column, an FRP core having 2.38 times the FRP diameter and having 5.66 times the FRP weight is needed as compared with an existing typical polymer post insulator used in polymer post insulators1-1to1-4of polymer insulator apparatus11. Thus, by combining existing typical polymer post insulators, a polymer insulator apparatus11of the present invention with less deformation and in particular with reinforced buckling strength can be obtained.

FIG. 5is a view for describing one example of a method for mounting a polymer insulator apparatus according to the present invention.FIG. 5shows an example in which the polymer insulator apparatus11of the present invention is used as one example of a switching device that opens and closes in an up-and-down direction in a substation or the like. In the example shown inFIG. 5, connecting plate13-1is fixed onto base14with screws, and polymer insulator apparatus11is mounted onto base14by disposing an opening/closing part mounting part17that is disposed on connecting plate13-3and connects the opening/closing part16of switching device15in a freely rotatable manner so that the cantilever load direction, here, the direction (shown by arrows) parallel to the plane of the operation (both directions shown by the arrows) of the opening/closing part16of switching device15will be the direction of parallel arrangement and connection of polymer post insulators1-1to1-4.

FIG. 6is a view for describing another example of a method for mounting a polymer insulator apparatus according to the present invention.FIG. 6shows an example in which the polymer insulator apparatus11of the present invention is used as one example of a switching device that opens and closes by swiveling in a substation or the like. In the example shown inFIG. 6, a switching device22having a swiveling opening/closing part23and an opening/closing part mounting part24for connecting the swiveling opening/closing part23in a freely rotatable manner is disposed on a polymer insulator apparatus11fixed onto a base (not illustrated) with screws. Further, a switching device25for connecting the swiveling opening/closing part23is disposed on another polymer insulator apparatus11fixed onto a base (not illustrated) with screws, which is different from the above-described one. In this case, the polymer insulator apparatus11are respectively mounted onto the bases (not illustrated) by disposing the polymer insulator apparatus11so that the direction E, F of the load generated at the time of connecting the swiveling opening/closing part23to the switching device25will be the direction of parallel arrangement and connection of the polymer post insulators1-1to1-4.

Thus, the polymer insulator apparatus of the present invention, which is constructed in such a manner that polymer post insulator columns, in which plural polymer post insulators are stacked, are arranged in parallel, and the polymer post insulator columns arranged in parallel are connected with each other via a connecting plate at each connection site of the polymer insulator constituting the polymer insulator columns as well as at the top and bottom of the polymer post insulator columns, can improve the strength against cantilever load and the buckling strength against compression load without increasing the diameter of the FRP of the polymer post insulators, by using already existing polymer post insulators. Therefore, the apparatus in particular can be suitably used as a substitute for a single polymer post insulator for high voltage, which tends to be long. With the use of the polymer insulator apparatus of the present invention, the polymer post insulators of 500 kV or higher that currently use a hollow core member in view of the strength can be replaced, and also the limit of the use of the polymer post insulators that are applied only up to 69 kV as a switching device in view of the problem of deflection can be raised to 115 kV class or higher.

Here, in the embodiment described above, polymer insulator apparatus11is constructed by arranging in parallel and connecting two polymer post insulator columns12-1,12-2which are constructed by stacking two polymer post insulators1-1,1-3or1-2,1-4. However, this is only an example, and it goes without saying that the number of stacked polymer post insulators is not limited to two, that the number of polymer post insulator columns, each constructed by stacking polymer post insulators, arranged in parallel and connected with each other is not limited to two, and that, if the number of polymer post insulator columns is three or more, the polymer post insulator columns arranged in parallel may be disposed not only in a line but also to form a polygon such as a triangle (FIG. 7) or a quadrangle as viewed from above. Furthermore, in the embodiment described above, the end of holding metal fitting pieces6-1to6-4has a flange shape, and holding metal fitting pieces6-1to6-4are fixed to connecting plates13-1to13-3with screws. However, it goes without saying that the holding metal fitting pieces6-1to6-4may be fixed onto connecting plates13-1to13-3with any means as long as they can be fixed.

As will be apparent from the above description, according to the present invention, polymer post insulator columns, in which plural polymer post insulators are stacked, are arranged in parallel, and the polymer post insulator columns arranged in parallel are connected with each other via a connecting plate at each connection site of the polymer insulator constituting the polymer insulator columns as well as at the top and bottom of the polymer post insulator columns. Therefore, in mounting the polymer insulator apparatus vertically onto a base, the polymer insulator apparatus can be mounted so that the direction of arranging the polymer post insulator columns in parallel will be a direction of cantilever load and the direction of stacking the polymer post insulators will be a direction of compression load. Thus, in particular, the strength in the cantilever load direction and the strength in the compression load direction can be improved.