JP7489433B2 - Bushings and Cable Terminations - Google Patents

Description

The present invention relates to bushings and cable termination connections, and in particular to technology suitable for use in termination connections that are directly connected to equipment.

Conventionally, cable termination connections such as gas termination connections, oil termination connections, and air termination connections are known (see, for example, Patent Document 1). In general, cable termination connections are formed by connecting a cable terminal portion to which a connection material is attached to a main body material (hereinafter referred to as a "bushing") having an inner conductor and a hard insulating tube arranged around the outer periphery of the inner conductor. In particular, equipment direct connection type termination connections used for connecting to electric power equipment such as switchgears are equipped with a T-shaped (or L-shaped) bushing having an equipment connection portion, a voltage supply portion, and a cable connection portion.

In a bushing for a T-shaped device direct connection type terminal connection part, the ends of the charging part and the cable connection part have a structure that allows the attachment of a fixing metal fitting or a rubber insulating plug for fixing the cable terminal part. For example, in the end of the cable connection part in the bushing disclosed in Patent Document 1, a fixing metal fitting (a pressing metal fitting flange 62 that is part of the pressing device 6 that presses the stress cone in the axial direction) that is subjected to spring stress on the cable terminal part side is directly fixed by bolting to an embedded metal fitting embedded in an insulating tube (3) made of epoxy resin.

Japanese Patent No. 4283659

As mentioned above, in conventional bushings, the fixing hardware (the lid for the rubber insulating plug, if a rubber insulating plug is installed) on which the spring stress is applied is fixed directly to the embedded hardware embedded in the bushing by tightening a bolt. Therefore, if the bolts are attached or removed unevenly when attaching or removing the cable terminal and rubber insulating plug to or from the bushing, localized stress may be concentrated in the insulating tube, causing cracks.

The object of the present invention is to provide a highly reliable bushing and cable termination section that can prevent damage to the insulating tube of the bushing when assembling or disassembling the cable termination section.

The bushing according to the present invention comprises:
A bushing for a direct connection type terminal connection part for connecting a power cable to a power device,
An inner conductor;
an insulating tube disposed around the outer periphery of the inner conductor;
an intermediate connection member having a front end fixed to the open end of the insulating tube by bolt fastening and a rear end to which a fixing member of the cable terminal portion to which spring stress is applied can be attached;
The intermediate connection member is formed of a material stronger than the insulating tube.

The cable termination according to the present invention comprises:
The above bushing and
the cable terminal portion attached to the bushing,
The cable terminal portion includes at least a conductor connection terminal, a stress cone, a compression device, and a protective metal fitting at a tip portion of the power cable,
The compression device includes a press fitting, a press fitting flange, the spring, and a washer,
The fixing member is constituted by the press fitting flange.

The present invention makes it possible to prevent damage to the insulating tube of the bushing when assembling or disassembling the cable termination connection part.

FIG. 1 is a cross-sectional view showing the internal structure of a cable termination to which a bushing according to an embodiment of the present invention is applied. FIG. 2 is an exploded view of a cable termination to which a bushing according to an embodiment of the present invention is applied.

The following describes in detail the embodiments of the present invention with reference to the drawings.

Figure 1 is a cross-sectional view showing the internal structure of a cable terminal connection part 1 to which a bushing 10 according to an embodiment is applied. Figure 2 is an exploded view of the cable terminal connection part 1 to which a bushing 10 is applied. The cable terminal connection part 1 is a direct-connection type terminal connection part for electric power equipment that requires airtightness, such as a switchgear or a transformer. In the following description, in the first bushing part 10A, the left side in the drawing is referred to as the "tip side" and the right side is referred to as the "rear end side", and in the second bushing part 10B, the upper side in the drawing is referred to as the "tip side" and the lower side is referred to as the "rear end side". In other words, the side in the direction in which the member is attached is referred to as the "tip side" and the opposite side is referred to as the "rear end side". In addition, the end face on the tip side may be referred to as the "tip face" and the end face on the rear end side as the "rear end face".

As shown in FIG. 1, the cable termination connection part 1 is formed by attaching the cable terminal part 20 to the bushing 10.

The bushing 10 has a first bushing part 10A extending in a first direction (horizontal direction (left and right direction in FIG. 1)) and a second bushing part 10B extending in a second direction (vertical direction (up and down direction in FIG. 1)) perpendicular to the first direction. The bushing 10 is a so-called T-shaped bushing in which the second bushing part 10B is branched and connected to the axial center part of the first bushing part 10A. The bushing 10 may also be a so-called L-shaped bushing in which the second bushing part 10B is connected to the axial end part of the first bushing part 10A. In this case, the internal conductor 11 described later becomes L-shaped, and the structure does not include the charging part 102 described later, the first receiving port 121, and the rubber insulating plug 40 attached to the receiving port.

The first bushing part 10A has an equipment connection part 101 at one end (left side in FIG. 1) to which an electric power device is connected, and a voltage charging part 102 at the other end (right side in FIG. 1) to which a voltage charging cable is connected during a voltage resistance test. The second bushing part 10B has a cable connection part 103 at its open end to which the cable terminal part 20 is connected. The voltage charging part 102 is blocked by a rubber insulating plug 40 during normal use.

The bushing 10 comprises an inner conductor 11, an insulating tube 12, a shielding layer 13, an equipment side fixing flange 14, a load side fixing flange 15, and an intermediate connection member 16.

The internal conductor 11 and the insulating tube 12 are integrally formed, for example, by molding. The shielding layer 13 is formed by a conductive paint applied to the outer circumferential surface of the insulating tube 12. The equipment side fixing flange 14 is disposed on the end face of the first bushing 10A on the equipment connection part 101 side (left side in FIG. 1) of the part excluding the equipment connection part 101, and is disposed on the outer periphery of the rear end part of the equipment connection part 101. The current-carrying side fixing flange 15 is disposed at the end of the insulating tube 12 in the current-carrying part 102.

The intermediate connection member 16 is disposed at the end of the insulating tube 12 at the cable connection section 103. The intermediate connection member 16 can have the press fitting flange 232 (fixing member) of the cable terminal section 20 attached to its rear end. The intermediate connection member 16 is formed from a material stronger than the insulating tube 12. A metal material is suitable for the material of the intermediate connection member 16. For example, a conductive material such as brass, stainless steel alloy, or aluminum alloy can be used for the material of the intermediate connection member 16.

The intermediate connection part 16 is, for example, a plate-like member having a circular ring shape in a plan view, and has a through hole formed in the center through which the tip side of the compression device 23 of the cable terminal part 20 is inserted. The inner diameter of the intermediate connection part 16 is larger than the outer diameter of the tip side of the compression device 23. The outer diameter of the intermediate connection part 16 is smaller than the outer diameter of the step part 123 described later. The edges of the tip surface and the rear end surface of the intermediate connection part 16 may be chamfered. The rear end surface of the intermediate connection part 16 has a plurality of non-penetrating screw holes (female threaded parts) formed along the circumferential direction for attaching the fixing member of the power cable 50. The intermediate connection part 16 also has a plurality of penetrating bolt insertion holes formed along the circumferential direction for fastening the bolt to the open end of the insulating tube 12.

The intermediate connection member 16 is fitted into the open end of the insulating tube 12. Specifically, a step 123 recessed from the rear end to the front end is formed at the open end of the insulating tube 12, and the intermediate connection member 16 is fitted into this step 123 and mechanically fixed to the insulating tube 12 by bolting. The surface 14 on the front end side of the step 123 (hereinafter referred to as the "mounting surface 14") is perpendicular to the axis of the cable terminal portion 20. A number of embedded fittings having female threads for bolting the intermediate connection member 16 are embedded in the mounting surface 124. The intermediate connection member 16 is fixed to the mounting surface 124 by inserting a bolt into the bolt insertion hole of the intermediate connection member 16 and bolting it to the embedded fitting.

The shielding layer 13 functions as a shielding section that prevents leakage to the outside and as an electric field mitigation section that mitigates the electric field within the bushing 10. In the first bushing section 10A, the shielding layer 13 is formed on the entire outer surface of the insulating tube 12 from the equipment side fixing flange 14 to the current-carrying side fixing flange 15. In the second bushing section 10B, the shielding layer 13 is formed on the outer surface of the insulating tube 12 except for the end on the cable connection section 103 side. The part of the second bushing section 10B where the shielding layer 13 is not formed (the part between the end of the shielding layer 13 and the press fitting flange 232 in FIG. 1) becomes the edge separation section 17 that insulates the grounding structure on the equipment side from the grounding structure of the power cable 50.

The shielding layer 13 is electrically connected to the equipment side fixing flange 14 and the charging side fixing flange 15. The shielding layer 13 is electrically connected to the equipment case 60 of the power equipment via the equipment side fixing flange 14 and is grounded. In other words, the end 131 of the shielding layer 13 at the equipment connection part 101 is the grounded end, and the ends of the shielding layer 13 at the charging part 102 and the cable connection part 103 are non-grounded ends. The resistance of the shielding layer 13 in the conductive path connecting the grounded end (end 131) of the equipment connection part 101 and the non-grounded end (end 132) of the charging part 102 is, for example, 10 Ω or less.

The internal conductor 11 is formed of a conductive material suitable for current flow, such as copper, aluminum, a copper alloy, or an aluminum alloy. The internal conductor 11 has a first conductor connection part 111 that connects to a cable conductor for current supply (not shown) inserted into the voltage supply part 102, and a second conductor connection part 112 that connects to a cable conductor 51 of a power cable 50 inserted into the cable connection part 103. Note that FIG. 1 shows normal use, in which a rubber insulating plug 40 is attached to the voltage supply part 102, and the conductor on the tip side of the rubber insulating plug 40 is electrically connected to the first conductor connection part 111 of the internal conductor 11.

The insulating tube 12 is formed of a hard plastic resin material with high mechanical strength (e.g., epoxy resin or fiber reinforced plastics (FRP)). The insulating tube 12 has a first receiving port 121 for receiving a charging cable (not shown) at the end on the charging section 102 side, and a second receiving port 122 for receiving a cable terminal section 20 at the end on the cable connection section 103 side. The first receiving port 121 communicates with the first conductor connection section 111 of the internal conductor 11, and the second receiving port 122 communicates with the second conductor connection section 112 of the internal conductor 11. A step 123 is formed on the inner peripheral surface on the rear end side of the second receiving port 122. The step 123 is formed, for example, so that the rear end surface of the insulating tube 12 and the rear end surface of the intermediate connection member 16 are flush with each other. Here, "flush" means that multiple different surfaces are in a positional relationship without any steps.

The outer diameter of the equipment side fixing flange 14 is larger than the diameter of the fixing opening (reference number omitted) provided in the equipment case 60. The equipment connection part 101 of the bushing 10 is inserted into the fixing opening of the equipment case 60, and the equipment side fixing flange 14 is bolted to the equipment case 60 via a sealing member (reference number omitted) such as an O-ring, thereby hermetically fixing the bushing 10 to the equipment case 60.

In the cable termination connection section 1, the cable terminal section 20 is configured by attaching connection members such as a conductor connection terminal 21, a stress cone 22, a compression device 23, a protective fitting 24, and a corrosion protection layer (not shown) to the tip of the power cable 50.

As shown in FIG. 2, the power cable 50 is, for example, a power cable insulated with rubber or plastic. The power cable 50 has, from the center, a cable conductor 51, a cable insulator 52, a cable outer semiconductive layer 53, a cable shielding layer 54, and a cable sheath (not shown). At the cable terminal portion 20, each layer is exposed by step-stripping a predetermined length from the tip of the power cable 50.

When the power cable 50 is of the free stripping type (also called the frist type), it is preferable to provide an external semiconductive processing part 25 on the tip side of the cable external semiconductive layer 53 in order to fill the step between the tip of the cable external semiconductive layer 53 and the cable insulator 52. The external semiconductive processing part 25 is formed by applying a conductive paint to the step-stripped tip side of the cable external semiconductive layer 53, or by wrapping a semiconductive tape such as polyethylene around it and performing a molding process.

A conductive conductor connection terminal 21 suitable for current flow and made of, for example, copper, aluminum, a copper alloy, or an aluminum alloy, is connected to the cable conductor 51 by compression. This electrically and mechanically connects the cable conductor 51 and the conductor connection terminal 21. A stress cone 22 is attached to the outer periphery extending from the cable insulator 52 to the tip of the external semiconductive processing part 25. A compression device 23 and a protective fitting 24 are attached to the rear end side of the stress cone 22.

The stress cone 22 is a pre-molded insulating tube having an overall spindle shape, with an insulating portion (numeral omitted) at the tip end and a semi-conductive portion (numeral omitted) at the rear end integrally formed by molding. The insulating portion is formed of an insulating rubber material such as ethylene propylene rubber (EP rubber) or silicone rubber, and the semi-conductive portion is formed of a semi-conductive rubber material such as semi-conductive ethylene propylene rubber (EP rubber) or silicone rubber.

The rear end (semiconductive portion) of the stress cone 22 is electrically connected to the cable external semiconductive layer 53 of the power cable 50. In this embodiment, the rear end (semiconductive portion) of the stress cone 22 is connected to the external semiconductive processing portion 25 and is electrically connected to the cable external semiconductive layer 53 via the external semiconductive processing portion 25. When the cable external semiconductive layer 53 is a bond type, the end of the cable external semiconductive layer 53 may be formed in a slope shape and directly connected to the rear end (semiconductive portion) of the stress cone 22. The outer peripheral surface of the tip side (insulating portion) of the stress cone 22 has a shape corresponding to the second receiving port 122 of the insulating tube 12 of the bushing 10, and the stress cone 22 is pressed against the second receiving port 122 of the insulating tube 12 by being pressed by the compression device 23.

The compression device 23 includes a pressing metal fitting 231, a pressing metal fitting flange 232, a spring 233, and a washer 234. The pressing metal fitting flange 232 is a fixing member for fixing the cable terminal portion 20 to the bushing 10. The pressing metal fitting flange 232 is fixed in a state in which the rear end surface of the recess (the bottom surface of the recess) and the rear end portion of the pressing metal fitting 231 are separated by a predetermined length so that the recess on the tip side covers the outer periphery on the rear end side of the pressing metal fitting 231, and the stress of the spring 233 is applied when the cable termination connection portion 1 is assembled. The spring 233 is disposed between the pressing metal fitting 231 and the washer 234 so that the tip portion is accommodated in a groove provided in the rear end portion of the pressing metal fitting 231, penetrating the pressing metal fitting flange 232.

After the tip of the power cable 50 is stripped, the protective bracket 24, compression device 23, and stress cone 22 are attached to the power cable 50, and the conductor connection terminal 21 is attached to the cable conductor 51, thereby assembling the cable terminal 20. By fixing the pressing bracket flange 232 to the bushing 10 by bolting, the outer surface of the insulation part at the tip side of the stress cone 22 is pressed against the inner wall surface of the second receiving port 122 of the insulating tube 12, and the conductor connection terminal 21 is electrically connected to the inner conductor 11. The biasing force of the spring 233 is adjusted by adjusting the axial position of the washer 234.

In this embodiment, the press fitting flange 232 of the cable terminal 20 is not directly attached to the insulating tube 12 of the bushing 10, but is attached to the intermediate connection member 16 fixed to the insulating tube 12. Even if the bolts are attached or detached unevenly during assembly or disassembly of the cable terminal connection part 1, causing localized stress concentration on the bushing 10, the stress is received by the intermediate connection member 16, which is stronger than the insulating tube 12, so damage such as cracks will not occur in the bushing 10.

In addition, in the case of bushings for equipment direct connection type terminal connections, the radial dimensions are significantly restricted, so it is difficult to ensure the strength of the mounting portion of the press fitting flange 232 on the insulating tube 12 by increasing the outer diameter of the insulating tube 12. On the other hand, when the bushing 10 of this embodiment is applied, the strength of the mounting portion of the press fitting flange 232 can be increased with a dimensional design equivalent to that of the conventional method.

In addition, in the bushing 10, it is necessary to ensure a certain length for the edge cutting portion 17. On the other hand, if the intermediate connection member 16 is placed on the rear end surface of the insulating tube 12, the length of the second bushing portion 10B will be increased. In this embodiment, the intermediate connection member 16 is placed by fitting it into the open end of the insulating tube 12, so that the provision of the intermediate connection member 16 can ensure the length of the edge cutting portion 17 without increasing the length of the second bushing portion 10B.

Thus, the bushing 10 according to the present embodiment is a bushing for an equipment direct-connection type termination portion for connecting a power cable 50 to an electric power equipment, and includes an inner conductor 11, an insulating tube 12 arranged on the outer periphery of the inner conductor 11, and an intermediate connection member 16 fixed to the open end of the insulating tube 12 and to which a press fitting flange 232 (fixing member) of a cable terminal portion 20 can be attached, the intermediate connection member 16 being made of a material stronger than the insulating tube 12. Specifically, the intermediate connection member 16 is made of a metallic material.
According to the bushing 10, it is possible to prevent the insulating tube 12 of the bushing 10 from being damaged when the cable termination connection part 1 is assembled or disassembled, thereby improving the reliability of the bushing 10. Furthermore, even if a defect occurs in the cable terminal part 20 and the cable termination connection part 1 is disassembled, the bushing 10 is not damaged and can be reused.

In addition, in the bushing 10, the intermediate connection member 16 is fitted into the open end of the insulating tube 12. This allows the intermediate connection member 16 to be provided without increasing the size of the bushing 10 (second bushing portion 10B).

In addition, in the bushing 10, the insulating tube 12 has a step portion 123 into which the intermediate connection member 16 is fitted. This allows the intermediate connection member 16 to be provided without changing the dimensional design of the insulating tube 12.

In addition, in the bushing 10, the intermediate connection member 16 is a plate-like member that has a circular ring shape in a plan view. This distributes the stress that occurs when the bolt is attached or detached unevenly, making it possible to withstand large stresses and further improving the reliability of the bushing 10.

In the bushing 10, the intermediate connection member 16 is fixed to an embedded metal fitting embedded in the insulating tube 12 by bolting. This prevents the intermediate connection member 16 from falling off the insulating tube 12 due to the weight of the cable terminal portion 20 when the cable terminal portion 20 extends vertically as in the embodiment.

The bushing 10 has a first bushing part 10A extending in a first direction and a second bushing part 10B extending in a second direction perpendicular to the first direction. The first bushing part 10A has an equipment connection part 101 provided at one end to which an electric power device is connected and a charging part 102 provided at the other open end to which a charging cable is connected during a voltage resistance test. The second bushing part 10B has a cable connection part 103 at its open end to which a cable terminal part 20 is connected. The first bushing part 10A and the second bushing part 10B are connected to form a T-shape. This makes it possible to increase the strength of the mounting part of the press fitting flange 232 with a dimensional design equivalent to that of the conventional bushing for a device direct connection type terminal connection part, which has a large radial dimensional constraint.

The invention made by the inventor has been specifically described above based on the embodiment, but the invention is not limited to the above embodiment and can be modified without departing from the gist of the invention.

For example, in the embodiment, the intermediate connection member 16 is provided on the cable connection section 103 side, but it may be provided on the voltage application section 102 side. In that case, a step recessed from the rear end to the front end may be provided on the open end of the insulating tube 12 on the voltage application section 102 side.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

REFERENCE SIGNS LIST 1 Cable end connection part 10 Bushing 10A First bushing part 10B Second bushing part 11 Inner conductor 12 Insulating tube 13 Shielding layer 14 Equipment side fixing flange 15 Load side fixing flange 16 Intermediate connection member 17 Edge cutting part 20 Cable terminal part 232 Press fitting flange 50 Power cable

Claims (7)

A bushing for a direct connection type terminal connection part for connecting a power cable to a power device,
An inner conductor;
an insulating tube disposed around the outer periphery of the inner conductor;
an intermediate connection member having a front end fixed to the open end of the insulating tube by bolt fastening and a rear end to which a fixing member of the cable terminal portion to which spring stress is applied can be attached;
The intermediate connection member is formed of a material having a higher strength than the insulating tube.
Bushing. the intermediate connection member is a plate-like member having a circular shape in a plan view, and has a through hole through which a front end side of a compression device forming the cable terminal portion is inserted, and the fixing member which can be attached to a rear end side forms a part of the compression device.
2. The bushing of claim 1. The intermediate connection member is made of a metal material.
2. The bushing of claim 1. The intermediate connection member is fitted into the open end of the insulating tube.
A bushing according to claim 1 or 2. The insulating tube has a step portion into which the intermediate connection member is fitted.
5. The bushing of claim 4. A first bushing portion extending in a first direction;
a second bushing portion extending in a second direction perpendicular to the first direction,
the first bushing portion has an equipment connection portion provided at one end portion to which an electric power equipment is connected, and a charging portion provided at the other open end portion to which a charging cable is connected during a voltage resistance test,
the second bushing portion has a cable connecting portion at an open end to which a cable terminal portion is connected,
The first bushing portion and the second bushing portion are connected to form a T-shape.
4. The bushing of claim 3. A bushing according to claim 2;
the cable terminal portion attached to the bushing,
The cable terminal portion includes at least a conductor connection terminal, a stress cone, a compression device, and a protective metal fitting at a tip portion of the power cable,
The compression device includes a press fitting, a press fitting flange, the spring, and a washer,
The fixing member is composed of the press fitting flange.
Cable termination connection.

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