Insulating Spacer

Abstract

An insulating spacer comprising a central conductor, a cylindrically shaped metallic shield which is arranged around said central conductor and is partially in contact with said central conductor, an insulating member made of a thermosetting resin said shield is embedded into the inner diameter thereof and said central conductor is enclosed thereby, and a shield of the earth side which is deeply embedded into a outwardly extending flange portion of said insulating member, and also preferably comprises fiber-reinforced resin formed of fibrous tissues which is tightly wound around a plurality of independent grooves provided on the periphery of said central conductor and a thermosetting resin which is infiltrated into said fibrous tissues so that said insulating member formed of a thermosetting resin may be firmly fixed around over said central conductor, thus said insulating spacer being adapted to be applied to a duct line air power transmission bus bar, gas-filled breaker or the like in which a sulfur hexafluoride gas is employed as an insulating medium.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an insulating spacer, and more particularly to an insulating spacer which is to be employed for a duct line air power transmission bus bar, a gas-filled breaker or the like in which a sulfur hexafluoride gas is mainly used as an insulating medium.

A type of insulating spacer having an insulating member formed of a thermosetting resin such as epoxy resin in the prior arts has been customarily constructed in the manner that metallic flanges are fixed to the periphery of the insulating member for said insulating member to be secured to an external duct and a central contuctor is fixedly connected to the center of the insulating member for said central conductor to penetrate through the insulating member.

However, the construction as described above tends to cause gap spaces at the boundary portions between the metallic flange and the insulating member and as well between the central conductor and the insulating member in manufacturing steps, and moreover in operation of the insulating spacer said gap spaces being caused and spread by respective differences of the thermal expansion coeficients thereof while the expansion and contraction due to the variable heat exerted. Accordingly, it is impossible to obtain any satisfactory gas-tightness and as well to prevent corona discharge from being generated even under low voltage.

Although a method in which a semiconductive adhesive is employed in order to solve the problems as above described has been attempted to be practiced, it has been impossible to obtain a satisfactory effect by this method.

The present invention has been completely accomplished with an object of eliminating the above mentioned disadvantages and then an insulating spacer according to this invention comprises a central conductor, a cylindrically shaped metallic shield arranged around said central conductor and partially in contact with said central conductor, an insulating member consisting of a thermosetting resin with said cylindrically shaped metallic shield being embedded into the inner wall thereof as to enclose said central conductor therewithin, and a shield of the earth side which is deeply embedded into a flange portion of said insulating member, and also preferably comprises fiber-reinforced resin formed of fibrous tissues which is tightly wound arround a plurality of independent grooves provided on the periphery of said central conductor and a thermosetting resin which is infiltrated into said fibrous tissues so that said insulating member formed of a thermosetting resin may be firmly fixed around over said central conductor, thus said insulating spacer being adapted to be applied to a duct line air power transmission bus bar, gas-filled breaker or the like in which a sulfur hexafluoride gas is employed as an insulating medium.

SUMMARY OF THE INVENTION

According to the present invention, there is obtained a much more improved insulating spacer as compared with that of the prior art, and the insulating spacer of the present invention comprises a central conductor and an insulating member provided around said central conductor, and as well is characterized in that a cylindrically shaped metallic shield being arranged on the periphery of said central conductor and made partially in contact with said central conductor, said central conductor being enclosed by the insulating member formed of a thermosetting resin for said cylindrically shaped shield to be embedded into said insulating member, and a shield portion of an earth side shield being deeply embedded into an outwardly extending flange portion of said insulating member, and further preferably characterized in that said central conductor being provided with a plurality of annular grooves on the periphery thereof, and each of said grooves being filled with reinforced plastic layer formed of fibrous tissues which is tightly wound with tension around each of said grooves and a thermosetting resin which is infiltrated into said fibrous tissues.

The primary object of the present invention is to provide a much more highly efficient insulating spacer means which is adapted to be applied to a duct line air power transmission bus bar, gas-filled breaker or the like for extremely high voltage.

Another object of the present invention is to provide an insulating spacer improved in that the insulating member formed of a thermosetting resin is firmly fixed around over the central conductor for eliminating gap spaces which tends to cause undesirable condition, that is corona discharge or deterioration of insulation.

The other advantages or characteristic features of the present invention will be described in detail in the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is an elevational sectional view of principal portion of the present invention, FIG. 1b is a front view of a shield which to be located close to the earth side in the present invention, FIG. 2 is an elevational sectional view of principal portion of another embodiment of the present invention, FIG. 3 is an elevational sectional view of principal portion of a prior art of an insulating spacer, and FIG. 4 is a graph illustrating the results in a comparison test on the flash-over characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, the reference numeral 1 designates a tubular or rod like central conductor, and the central conductor is arranged to be embedded as to penetrate through the center of an insulating member 2 formed of a thermosetting resin such as epoxy resin or the like and is also provided with annular projections 3,3 at the embedded portion therearound in a suitably spaced relation. A cylinder 4' made of a conductive material such as a metallic foil, a metal plate or a metallic meshes is closely arranged around the central conductor 1 between the annular projections 3,3 and is connected to the central conductor, thereby a shield 4 of the conductor side is provided as to be embedded into the inner wall of said insulating member 2.

The reference numeral 5 designates a shield of the earth side, which is embedded coaxially with the central conductor 1 into a flange portion 2' of the insulating member 2, and this earth side shield 5 consists of an annular shield portion 6 made of a conductive material such as a metallic foil, a metal plate or a metallic meshes as similar to that of the shield 4' and formed into the shape of a channel in cross section as shown in FIG. 1b, a plurality of conductive portions 7 provided on the annular shield portion 6, and cylindrical brackets 8 provided at the respective ends of the conductive portions 7. Each of the brackets 8 is made to penetrate through the flange portion 2' of the insulating member 2 so that adjacent external ducts 10 may be fixedly joined at the projected flanges 10' thereof together with the insulating member 2 by means of bolts 9 inserted through the brackets 8.

In addition, the central conductor 1 is provided with a plurality of independent annular grooves 11 having the dimensions, for an example, of approximately 10 mm. in width, approximately 3 mm. in depth and approximately 10 mm. in pitch, and each of the grooves is filled with reinforced plastic layer 12 that is so called FRP formed of fibrous tissues such as roving, cloth or tape which is tightly wound with tension around said annular grooves 11 and a thermosetting resin such as epoxy resin or the like which is infiltrated into said fibrous tissues.

When the insulating member 2 formed of a thermosetting resin material such as epoxy resin or the like as above mentioned is put over around the central conductor after each of the annular grooves 11 have been previously filled with the reinforced plastic layer 12, since the reinforced plastic layer 12 is also formed of substantially the same thermosetting resin as the insulating member 2, the insulating member may be positively integrated together with the reinforced plastic layer. Furthermore, since the thermal expansion coefficient of the reinforced plastic layer 12 is provided with an intermediate value between that of the central conductor 1 made of a metal and that of the insulating member 2 made of a thermosetting resin, the reinforced plastic layer 12 serves as a buffer layer against the thermal shock caused between the central conductor 1 and the insulating member 2.

Additionally, any occurrence of corona discharge due to foams involved in the reinforced plastic layer 12 may be prevented by means of the metallic shield 4, and in case of this shield being formed of a metallic meshes the insulating member 2 formed of a thermosetting resin can be rigidly fixed to the reinforced plastic layer 12 by impregnating said meshes with said resin without gap spaces.

Still further, since each of the annular grooves 11 filled with the reinforced plastic layer 12 is independently arranged, assuming that partial break away would be caused between the central conductor 1 and the reinforced plastic layer 12, this break away is effectively prevented from further spreading into the other portion of the layer.

FIG. 2 shows an another embodiment of the present invention which is different from FIG. 1a only in that annular projections as indicated 3,3 in FIG. 1a are omitted and an insulating member 2 is formed upright.

FIG. 3 shows an insulating spacer of the prior art in which gap spaces tends to be brought about at the adhesive boundary area 14 between the insulating member 2 and the metallic flange portion 13 arranged on the periphery of the insulating member 2 and at the boundary area 15 between the central conductor 1 and the insulating member 2.

In case that the insulating spacer which is constituted as above mentioned according to this invention is practiced with sulfur hexafluoride gas being charged into each of closed chambers defined by the central conductors 1, external ducts 10 and the insulating spacers, since the shield portion 6 of the earth side shield 5 is deeply embedded into the flange portion 2' of the insulating member 2 formed of thermosetting resin such as epoxy resin or the like, any gap space is not brought about at the area of the earth side shield 5, and since the conductor side shield 4 is also firmly embedded into the insulating member 2 in connection with the central conductor 1, any gap space is not brought about as well at the area of the conductor side shield 4. Accordingly, it can be effectively prevented from occurring that the insulating material is eroded by a resolved gases of the sulfur hexafluoride gas caused by the corona discharge, thus resulting in the insulation deterioration and damage of the insulating spacer being eliminated.

The results in a comparison test with respect to the flash-over characteristics by changing the pressure of the sulfur hexafluoride gas filled in each of the closed chamber provided between the adjacent insulating spacers which have the dimensions of 150 mm. in the outer diameter of the central conductors 1 and of 600 mm. in the inner diameter of the external ducts 10 are as shown in a graph of FIG. 4, and the insulating spacer according to the present invention proves to be much more improved in that any insulation deterioration does not appear even at the high pressure region of the sulfur hexafluoride gas as compared with that of the prior art.

Claims

I claim:

1. An insulating spacer comprising a central conductor and an insulating member provided around said central conductor, characterized in that said central conductor is provided with a plurality of grooves on the periphery thereof, each of said grooves is filled with reinforced plastic layer formed of fibrous tissues which is tightly wound with tension around each of said grooves and a thermosetting resin which is infiltrated into said fibrous tissues, a cylindrically shaped metallic shield is arranged on the periphery of said central conductor and made partially in contact with said central conductor, said central conductor is enclosed by the insulating member formed of a thermosetting resin for said cylindrically shaped shield to be embedded into said insulating member, and a shield portion of an earth side shield is deeply embedded into an outwardly extending flange portion of said insulating member.

2. An insulating spacer as defined in claim 1 wherein the thermosetting resin infiltrated into the reinforced plastic layers and the thermosetting resin formed into the insulating member are epoxy resin.

3. An insulating spacer as defined in claim 1 wherein the shield portion of the cylindrically shaped metallic shield and the earth side shield are formed of a metallic meshes.