JP5305769B2 - Cast insulation - Google Patents

Description

The present invention relates to a cast insulator in which a central conductor that can improve insulation characteristics is embedded.

Cast insulators molded with epoxy resin have excellent electrical and mechanical properties and are often used as insulating supports for electrical equipment such as switchgear. For example, a main circuit disconnecting portion in which an insulating layer is formed around a central conductor is used in a portion penetrating the board wall, and the main circuit conductor is supported and fixed together with insulation from the board wall (for example, Patent Documents) 1).
JP 2007-274861 A (Page 3, FIG. 1)

  The above-described conventional cast insulator has the following problems. When an epoxy resin is filled in the casting mold and cured by heating, burrs are formed on the mating surface of the casting mold. Further, burrs are also formed on the boundary surface between the central conductor and the insulating layer. Such burrs are finished by removing with a file or the like, but if an excessive stress is applied to the center conductor, a minute gap may be formed at the boundary surface between the center conductor and the insulating layer.

  That is, although the insulating layer is firmly bonded to the central conductor, the thermal expansion coefficient may be different between the central conductor and the insulating layer, and it is difficult to make the adhesive strength the same over the entire region. For this reason, at the time of finishing the boundary surface between the central conductor and the insulating layer, there are cases where peeling occurs at a portion where the adhesive strength is weak. When the gap is formed by peeling, a partial discharge is generated from that portion, resulting in insulation deterioration.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a cast insulator that can improve the insulation characteristics of the boundary surface between the central conductor and the insulating layer.

In order to achieve the above object, a casting insulator according to the present invention includes a central conductor connected to a main circuit conductor of an electrical device, an insulating layer formed by casting around the central conductor, and the central conductor. And a filling layer in which a fluidized insulator is pressurized and filled in a gap formed at the interface between the insulating layer and the insulating layer, and a sealing film is provided on an exposed portion of the filling layer in the air .

  According to the present invention, since the filling layer filled with the fluidized insulating material is provided in the gap formed at the boundary surface between the central conductor and the insulating layer, the insulating characteristics can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a cast insulator according to Example 1 of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the structure of a cast insulator according to Example 1 of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of the cast insulator according to Example 1 of the present invention, and FIG. It is a flowchart explaining the manufacturing method of the casting insulator which concerns on Example 1 of this invention. The cast insulator will be described using the main circuit disconnection portion of the switch gear.

  As shown in FIG. 1, an insulating layer 2 formed by being integrally cast with an insulating material such as an epoxy resin is formed around the center conductors 1 for three phases arranged in a row while maintaining a predetermined insulating distance. Is provided.

  A cylindrical fold 2a is provided on the left side of the insulating layer 2 so as to surround each central conductor 1, and a main circuit conductor 3 of a switch (not shown) is connected to the end of the central conductor 1 at the bottom of the fold 2a. It has become so. On the right side of the insulating layer 2 in the figure, annular ridges 2 b are provided so as to surround the center conductor 1, and the main circuit conductor 4 of the switch gear is fixed to the end of the center conductor 1. Fillers 5 are embedded at both ends of the insulating layer 2, and are fastened and fixed to the panel wall 6 with bolts 7.

  Here, as shown in FIG. 2, a fluid insulating material having excellent liquid or cream-like insulating properties such as silicone oil or silicone grease is pressurized in the gap at the boundary surface between the central conductor 1 and the insulating layer 2. In this way, a filled layer 8 is provided which is permeated and filled. The filling layer 8 is different in thickness and length for three phases, and there is a phase in which the filling layer 8 is not formed.

  Next, a method for forming the filling layer 8 will be described with reference to FIG.

  When the epoxy resin was heated and cured in the casting mold and released from the mold, and the casting was completed (st1), it was formed at the joint of the casting mold, the boundary surface between the central conductor 1 and the insulating layer 2, or the like. Remove the burr with a file (st2). Then, silicon grease is applied to the boundary surface between the central conductor 1 and the insulating layer 2 at the bottom of the fold 2a, for example, by brushing (st3). Although silicon grease is applied to the entire circumference of the boundary surface, it may be sufficiently applied to the center conductor 1 side.

  Next, the main circuit disconnecting portion coated with the fluid insulator is carried into a pressurized tank and pressurized with dry air (st4). The pressure is 0.2 MPa to 0.5 MPa, and is maintained for about 5 minutes. As a result, the fluidized insulator applied to the surface is pressurized and filled while penetrating into the gap, thereby forming the filling layer 8. In addition, it is thought that there is a part where the gap has a negative pressure. By applying pressure, the silicon grease can be uniformly filled. After that, the pressure is reduced (st5), taken out from the pressurized tank, and so-called remaining silicon grease adhering to the surface of the central conductor 1 and the insulating layer 2 is removed.

  Next, when the pressurized pressure and the corona characteristics were obtained, the corona characteristics increased with increasing pressure and saturated from 0.2 MPa or more. Corona characteristics were improved by 20 to 50% at a pressure of 0.2 MPa. Since the width of the gap is as narrow as several to several hundreds of micrometers, once filled silicon grease is difficult to flow out easily. Note that a gap is easily formed in a cast insulator having a large capacity of the central conductor 1 and having a volume ratio larger than that of the insulating layer 2, and the effect of the filling layer 8 is large.

  According to the cast insulator of Example 1 above, a fluidized insulator such as silicon grease is filled at a pressure of 0.20 Pa or more into the gap formed at the boundary surface between the central conductor 1 and the insulating layer 2. Since the filled layer 8 is provided, the corona characteristics can be improved.

  In the first embodiment, the cast insulator has been described using the main circuit disconnecting portion. However, an insulating layer is formed around the main circuit conductor such as a single bushing or an insulating bus, and a gap is formed at the boundary surface. Similar effects can be obtained in cast products.

  Next, a cast insulator according to Example 2 of the present invention will be described with reference to FIG. FIG. 4 is an enlarged cross-sectional view of a main part of the cast insulator according to the second embodiment of the present invention. The second embodiment differs from the first embodiment in that a sealing film is provided. In FIG. 4, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4, a sealing film 9 is provided on the exposed portion where the filling layer 8 is in contact with the air, and a quick-drying epoxy resin adhesive is applied by brushing, for example, and cured. In addition, before apply | coating an epoxy resin adhesive, if the said part is degreased with alcohol etc., the sealing film 9 can be provided firmly.

  According to the cast insulator of the second embodiment, the filling layer 8 can be stably provided over a long period of time.

Sectional drawing which shows the structure of the casting insulator which concerns on Example 1 of this invention. The principal part expanded sectional view of the casting insulator which concerns on Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The flowchart figure explaining the manufacturing method of the cast insulator which concerns on Example 1 of this invention. The principal part expanded sectional view of the casting insulator which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Center conductor 2 Insulating layer 2a, 2b Folding 3, 4 Main circuit conductor 5 Filler 6 Board wall 7 Bolt 8 Filling layer 9 Sealing film

Claims (1)

A central conductor connected to the main circuit conductor of the electrical equipment;
An insulating layer formed by casting around the central conductor;
A filling layer that pressurizes and fills a gap formed in a boundary surface between the center conductor and the insulating layer by pressurizing a fluid insulator;
A casting insulator, wherein a sealing film is provided on an exposed portion of the filling layer in the air .

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