JPH10257657A - Insulation structure body of cable termination part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a layer for breaking a grounding current and to improve a damage resistance characteristic by peeling off a grounding layer at a bushing side, forming an insulation layer, breaking a small amount of current that circulates between grounds, providing a metal cylinder with a constant gap at the outer periphery of the insulation layer by the grounding layer, and controlling the increase in a grounding potential. SOLUTION: A metal cylindrical electrode 20 that is inserted from a cable edge part side to an insulation layer 4 and has a constant gap length for the outer periphery of the insulation layer 4 is provided at the edge part of a cable 2. Then, the metal cylinder electrode 20 is wrapped by a specific distance from one edge part in the axial direction of the insulation layer 4, and a grounding layer 21 is formed near an area directly below the metal cylindrical electrode 20 from the edge part of the opposite side of cable edge part on the outer-periphery surface of the insulation layer 4. One portion of the grounding layer 21 of the bushing 1 is peeled off and the insulation layer 4 is exposed, thus breaking a small amount of current that circulates between grounds. Also, the metal cylindrical electrode 20 is inserted from the side of the cable 2 towards the side of a bushing 1, thus controlling a surge voltage due to increase in the grounding potential generated when the grounding current flows.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation structure of a cable terminal section for cutting off a ground layer on a cable side and a panel side at a cable terminal section connected to, for example, a switch gear used in power supply equipment.

[0002]

2. Description of the Related Art As a configuration example of a cable terminal portion connected to a switch gear, a slip-on type shown in FIG. 7 has recently been frequently used from the viewpoint of shortening a construction period and improving reliability. T
A configuration in which a slip-on type cable 2 is mounted on a bushing 1 of a mold and a switch gear (not shown) is connected to the cable 2 is disclosed in JP-A-64-77406. There is an advantage that can be made from either direction.

A T-shaped bushing 1 is fixed to a panel wall 3 while maintaining airtightness, a cable 2 is attached from the air side, and connected to an internal electrode 5 covered with an insulating layer 4. The internal electrode 5 is provided with a cylindrical opening 5b, and a conductor 5a is attached at a right angle from a substantially central portion, and is connected to an electric device (not shown).

On the left and right sides of the insulating layer 4 made of epoxy resin, there is a conical opening 4a corresponding to the opening 5a of the internal electrode 5, and on one side, an insulating layer 6 made of a rubber insulating material is provided.
And a stress cone 7 for alleviating the electric field are in close contact with a spring 8. These are housed in a protective tube 9 made of metal and having a substantially U-shaped cross section and having a flange portion at one end. An insulating collar 11 is provided on the axial end surface of the insulating layer 4.
The flange of the protective tube 9 is fixed to the insulating collar 11 with bolts 10a.
Is fixed to the axial end surface of the insulating layer 4 by bolts 10b, the bolts 10a and 10b on the protective tube 9 side are formed alternately, and the bolts 10a and 10b are insulated from each other. It is covered with an insulating layer.
A ground layer 12 coated with, for example, a conductive paint is provided on the entire outer circumferential surface of the insulating layer 4 in the axial direction.

In the other opening 4b of the insulating layer 4,
An insulating layer 13 made of a rubber insulating material is sandwiched between electrodes 14 and 15 on the high voltage side and the ground side, and is in close contact with a spring 16. The spring 16 applies the bolt 1 to the insulating layer 4.
The pressure is fixed by a holding plate 18 fixed at 7, and a surface pressure is applied to the interface between the insulating layers 4 and 13. Therefore, this portion is the end of the T-shaped bushing 1 to which the main circuit is not connected.

[0006]

In the conventional cable terminal portion configured as described above, a minute current such as a charging current of the cable 2 is reduced by the ground layer 2a of the cable 2 and the protection tube 9a.
Through the grounding layer 12 of the bushing 1 to the board wall 3. However, in order to prevent heat generation due to this minute current, an insulating collar 11 is provided between the protective tube 9 and the ground layer 12.
Is sandwiched, and the minute current is interrupted.

[0007] Between the insulating collars 11, for example, a dielectric strength sufficient to withstand a surge voltage generated when an arrester housed in the panel operates is required. This surge voltage is an increase in the ground potential. The larger the ground resistance and the greater the steepness of the current, the larger the surge voltage becomes, and generally becomes several tens of kV.

For this reason, the insulating collar 11 requires a creepage distance in addition to a sufficient insulating thickness, so that the insulating collar 11 becomes a long object having a large diameter. As a result, the size of the cable termination itself becomes large, which goes against the recent trend of miniaturization. SUMMARY OF THE INVENTION An object of the present invention is to provide an insulating structure of a cable terminal portion that can be reduced in size.

[0009]

In order to achieve the above object, according to the present invention, an outer peripheral portion of an electrode fixed to a fixed portion such as a switch gear and connected to an electric device or the like is surrounded by an insulating layer. The bushing, and at the cable end where the cable end of the electrode is electrically connected, is inserted into the cable end from the cable end side toward the insulating layer, and with respect to the outer periphery of the insulating layer. A metal cylinder electrode is provided so as to form an air gap having a constant gap length, the metal cylinder electrode is wrapped by a predetermined distance from one end in the axial direction of the insulating layer, and an outer peripheral surface of the insulating layer. A grounding layer is formed from an end opposite to the end of the cable to a position immediately below the metal cylindrical electrode.

In order to achieve the above object, the invention according to claim 2 is characterized in that, based on a voltage characteristic of an air gap between the metal cylinder electrode and the grounding layer, an insulation layer surface in which the metal cylinder electrode and the insulation layer are wrapped. So that the voltage characteristics of
2. The insulation structure of a cable end portion according to claim 1, wherein said air gap and creepage distance are set.

According to a third aspect of the present invention, there is provided a bushing, wherein the bushing is fixed to a fixed portion such as a switch gear and an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer. At the cable terminal end where the cable end of the electrode is electrically connected, an insulating layer of the bushing is provided with an insulating layer at the end on the side connected to the cable, electrodes are provided at both ends of the insulating layer, and An insulation structure at a cable terminal end, wherein a resistance layer or a protection layer is formed.

According to a fourth aspect of the present invention, there is provided a bushing wherein the outer periphery of an electrode connected to an electric device or the like is surrounded by an insulating layer. At the cable end where the cable end of the electrode was electrically connected, the vicinity of the cable end was removed from the outer peripheral surface of the insulating layer and the axial end opposite to the cable end. A grounding layer is formed up to a portion, and a semiconductive layer is formed on an outer peripheral surface of the insulating layer where the grounding layer is not formed.

According to a fifth aspect of the present invention, there is provided a bushing, wherein the bushing is fixed to a fixed portion such as a switch gear, and an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer. At the cable end where the cable end of the electrode was electrically connected, the vicinity of the cable end was removed from the axial end opposite to the cable end on the outer peripheral surface of the insulating layer of the bushing. A ground layer is formed on all portions of the portion, and a cylindrical protective cap made of a semiconductive material is attached to the outer peripheral surface of the insulating layer of the bushing, where the ground layer is not formed, An insulating structure at a cable terminal end, wherein the protective cap and the insulating layer of the bushing are adhered to each other.

According to a sixth aspect of the present invention, there is provided a bushing, wherein the bushing is fixed to a fixed portion such as a switch gear and an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer. At the cable end where the cable end of the electrode is electrically connected, a ground layer is formed on the outer peripheral surface of the insulating layer from the axial end opposite to the cable end to the cable end. Formed, and an insulating layer newly formed of an insulating material having a high dielectric constant is interposed between the cable end and the bushing insulating layer, and is integrally fixed with the cable end and the bushing insulating layer. It is an insulating structure of a cable terminal portion.

According to a seventh aspect of the present invention, to achieve the above object, a zinc oxide element is buried in a newly disposed insulating layer between the cable end portion according to the sixth aspect and the insulating layer of the bushing. In addition, the cable end portion and the insulating layer of the bushing are integrally fixed to each other.

According to the present invention, the following functions and effects can be obtained. That is, there is no circulation between the bushing and the ground layer of the cable because the minute current is interrupted at the bushing end. Here, if a ground fault current occurs,
Although a surge voltage is applied to the cut surface of the insulating layer, the surge voltage is absorbed by an air gap formed by electrodes provided between the ground layers. Since this air gap is set to flash over at a lower voltage than the creepage,
When a surge voltage enters, no flashover occurs along the surface. Therefore, the creepage distance of the blocking layer can be reduced. In addition, since the outer periphery of the blocking layer is covered with a cylindrical electrode, contamination such as dust can be prevented.

Further, if a resistor or semiconductive layer is provided on the cut surface of the insulating layer, a minute current circulating between the ground layers can be further reduced, and an overvoltage such as a surge voltage can be suppressed. Thereby, the creepage distance of the insulating layer to be cut off can be reduced.

Further, if the insulating layer to be cut off is made of an insulating material having a high dielectric constant, when an overvoltage such as a surge voltage is applied, the insulating layer can easily absorb a high-frequency surge voltage, resulting in a peak value. Can be suppressed.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of an insulation structure of a cable terminal according to the present invention.
The same reference numerals are given to the same portions as those of the conventional cable terminal end insulating structure shown in FIG.

<First Embodiment> FIG. 1 shows a slip-on type cable terminal portion. A T-shaped structure in which the outer peripheral surface of a rod-shaped electrode 5a fixed to a fixed portion such as the panel wall 3 of the switch gear and connected to an electric device or the like is surrounded by an insulating layer 4 made of a solid insulating material made of, for example, epoxy resin. At the end of the cable where the bushing 1 and the end 2 of the cable 2 are electrically connected, the cable is inserted into the end of the cable 2 from the end of the cable toward the insulating layer 4. A metal tube electrode (protective tube) 20 is provided so as to form an air gap having a constant gap length, the metal tube electrode 20 is wrapped by a predetermined distance from one end of the insulating layer 4 in the axial direction, and From the outer peripheral surface of the insulating layer 4 and the end opposite to the cable end, the metal cylindrical electrode 20
The ground layer 21 is formed almost immediately below.

A bushing 1 for connecting the aforementioned cable 2
Ground layer 21 provided on the outer periphery of
The metal tube electrode 20 fixed to one end of the ground layer 21 with a gap of, for example, several millimeters provided on the outer periphery of the cut insulating layer 4 is cut off. It is attached to cover the part. In this case, an existing device can be applied.

In FIG. 1, a cable 2 is mounted on a T-shaped bushing 1 fixed to a panel wall 3. In the bushing 1, an electrode 5 connected to the cable 2 and a rod-shaped electrode 5a connected to an electric device in a panel (not shown) are arranged substantially perpendicular to the electrode 5, and these are integrally formed by an insulating layer 4. Molded.

At the end of the cable 2, an insulating layer 6 made of a rubber insulating material and a stress cone 7 for alleviating an electric field are provided.
Is provided, and the insulating layer 4 and the insulating layer 6 are pressed against each other by a spring 8 so as to be in close contact with each other.

Here, the metal tube electrode 20 fixed to the insulating layer 4 with bolts 19 is housed, and the end portion 20a of the metal tube electrode 20 is slightly larger than the outer diameter of the insulating layer 4. The ground layer 21 provided on the outer periphery of the insulating layer 4 extends to the end 20 a of the metal tube electrode 20, and the portion facing the metal tube electrode 20 is the surface of the insulating layer 4. Therefore, the grounding layer 2a on the cable 2 side and the grounding layer 21 on the bushing 1 side are shut off.

On the side where the cable 4 is not connected, the insulating layer 13 sandwiched between the electrodes 14 and 15 is adhered by a spring 16. Further, the spring 16 is provided with the insulating layer 4.
Is fixed by a holding plate 18 fixed by bolts 17.

As described above, since a part of the ground layer 21 of the bushing 1 is peeled off and the insulating layer 4 is exposed, a minute current circulating between the ground can be cut off. Also, the insulating layer 4
Is inserted from the cable 2 side toward the bushing 1 side, for example, a surge due to a rise in ground potential generated when a ground fault current flows. The voltage can be suppressed by controlling the gap length, the size of the layer that blocks the ground current can be reduced, and the antifouling property can be improved.

<Second Embodiment> Here, the metal cylindrical electrode 2
0 is shown in FIG. 2, but the ground layer 2 provided on the surface of the insulating layer 4
At one end, a U-shaped groove 21 a is provided to divide the boundary between the ground layer 21 and the insulating layer 4.

In such a configuration, the flashover when the creepage distance of the insulating layer 4 is 1 and the gap length between the U-shaped groove 21a (the end of the ground layer) and the end 20a of the metal cylindrical electrode 20 is G. FIG. 3 shows an example of the voltage characteristics. The solid line a) shows the voltage characteristic corresponding to the gap length G, and the dotted line b) shows the voltage characteristic corresponding to the creepage distance l. When the gap length G and the creepage distance 1 are the same, the creepage voltage characteristic is about 10%
descend. This is because the creeping characteristic has a larger intrinsic capacitance between the electrodes, so that the flashover easily progresses. Thus, the size of the end portion 20a of the metal cylindrical electrode 20 is set so that the gap length G is at least equal to or less than the creeping distance l. That is, the voltage characteristic of the gap length G is set to a level lower than the surface characteristic.

As a result, the ground current flows and the ground layer 2a
When a surge voltage is applied to −21, a flashover occurs between the ground layer 21 and the end 20 a of the metal cylindrical electrode 20, and dielectric breakdown does not occur on the creeping surface. This surge voltage is several tens of k
Although it is estimated to be V, it may easily change depending on the current steepness, the peak value, and the ground resistance value of the ground current, and may become excessively large. However, since the surge voltage can be suppressed by the gap length G, the creepage distance can be minimized. For this reason, it is possible to form a ground current blocking layer having a short creepage distance.

The withstand voltage characteristic of the gap between the electrode provided on the outer periphery and the ground layer is lower than the withstand voltage characteristic of the surface of the insulating layer that blocks the ground layer 21 formed at the end of the T-shaped bushing 1. Furthermore, since the end portion 20a of the metal cylindrical electrode 20 is covered on the creepage portion, it is possible to prevent contamination such as dust, so that a stable creepage dielectric strength can be maintained. In addition, since the inspection cycle such as cleaning is greatly extended, maintenance is facilitated. The magnitude of the surge voltage can be controlled by changing the size of the end portion 20a of the metal cylinder electrode 20, so that a malfunction of the control circuit can be dealt with. That is, if there is a fear of malfunction, the surge voltage can be controlled by changing the gap length.

Third Embodiment Next, FIG. 4 shows a configuration in which a resistance layer or a protection layer (hereinafter referred to as a resistance layer or the like) 22 is provided on the surface of the insulating layer 4. The resistance layer 22 and the like 22
And a protective tube 9, for example, a paint mixed with carbon is applied, and has a resistance value of a megorder. Further, for example, a semiconductive layer 23 coated with a semiconductive paint mixed with silicon oxide is provided.

In these configurations, during steady operation, the minute current circulating in the ground layer 21 is further reduced by the resistance layer 22 or the semiconductive layer 23, and has little effect such as thermal. When a surge voltage enters, the surge current is suppressed by the resistance layer 22 or the like, or the surge current is similarly suppressed by reducing the resistance of the semiconductive layer 23,
Surge voltage is suppressed. Note that these resistance layers and the like 2
2. If a protective layer formed by applying a paint such as an epoxy resin is formed on the semiconductive layer 23, it is possible to cope with moisture proofing.

Thus, the resistance layer 22 and the semiconductive layer 2
Since the surge voltage applied during the period 3 is suppressed and no flashover occurs on the surface, the creepage distance between the resistive layer 22 and the semiconductive layer 23 can be reduced.

<Fourth Embodiment> Next, FIG. 5 shows a configuration in which the surface of an insulating layer is covered with a semiconductive cap 24 made of an insulating material. The semiconductive cap 24 is made of a rubber material and is formed from the protection tube 9 to the ground layer 21 on the bushing 1 side. After the cable 2 is connected, the semiconductive cap 24 is slid over the protection tube 9 and attached.

Incidentally, silicone grease may be applied to the interface between the insulating layer 4 and the semiconductive cap 24 so that the grease can be easily mounted. In addition, the interface only needs to be in close contact with the semi-conductive cap 24 by making the inner diameter of the semi-conductive cap 24 slightly smaller than the outer diameter of the insulating layer 4 and by such a stress that the semi-conductive cap 24 itself shrinks.
Thereby, the surge voltage applied to the protection tube 9 and the ground layer 21 can be suppressed.

<Fifth Embodiment> Next, FIG.
A configuration in which an insulating collar 25 made of an insulating material having a high dielectric constant is provided between the protective collar 9 and the protective tube 9 is shown. As the insulating material having a high dielectric constant, for example, a material obtained by mixing powder such as barium titanate with an epoxy resin and molding the mixture is used. The ground layer 12 provided on the surface of the insulating layer 4 has the same configuration as the conventional example provided up to the end of the bushing.

As a result, the insulating collar 25 is easily charged by the surge voltage of the protective tube 9 and the ground layer 21,
The peak value of the surge voltage is suppressed, and the rise time becomes slow.

<Sixth Embodiment> Next, an insulating collar 25 will be described.
If a zinc oxide element is embedded and mounted in the device, the surge voltage can be controlled by selecting the thickness of the zinc oxide element. In this case, one of both ends of the zinc oxide element is connected to the grounding layer 12 of the bushing, and the other is connected to the grounding layer 2 a of the cable 2.

As described above, at the cable termination, the minute current circulating in the ground layer is cut off, the surge voltage generated when a ground fault current flows is suppressed, and the length of the bushing can be reduced in the length direction. An insulating structure is obtained.

<Seventh Embodiment> The present invention is not limited to the above-described embodiments, and can be implemented with, for example, the following modifications. That is, a large number of electrical components provided with a ground layer on the outer periphery by molding a conductor with an insulator are connected, and when a circulating current flows between the power supply side and the ground layer, the ground layer is peeled off at any connection point, By providing an electrode with a gap around the stripped blocking layer, a circulating current can be cut off, and a surge voltage generated between the grounds can be suppressed, so that the size of the blocking layer can be reduced.

[0041]

According to the present invention described above, at the cable terminal end, the grounding layer on the bushing side for connecting the cable is peeled off to form an insulating layer, and a minute current circulating between the grounds is cut off. A metal cylinder with a certain gap around the outer periphery of the layer is provided from one of the ground layers, and surge voltage caused by a rise in ground potential generated when a ground fault current flows is controlled by controlling the gap length, and grounding is performed. It is possible to obtain an insulating structure at the cable terminal end that can reduce the size of the current blocking layer and improve the antifouling characteristics.

Further, according to the present invention, a cable capable of suppressing and reducing surge voltage by providing a resistance layer, a semiconductive layer, or a high dielectric constant insulating material layer on an insulating layer that blocks ground current. An insulating structure at the end can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of an insulating structure at a cable terminal end according to the present invention.

FIG. 2 is an enlarged cross-sectional view in which main parts of FIG. 1 are enlarged.

FIG. 3 is a representative characteristic diagram showing a flashover voltage between a creepage surface and an air gap shown in FIG. 2;

FIG. 4 is a cross-sectional view showing only a main part of a second embodiment of an insulating structure at a cable terminal end according to the present invention.

FIG. 5 is a cross-sectional view showing only a main part of a third embodiment of an insulating structure at a cable terminal end according to the present invention.

FIG. 6 is a sectional view showing only a main part of a fourth embodiment of an insulating structure at a cable terminal end according to the present invention.

FIG. 7 is a cross-sectional view showing an example of a conventional cable termination portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Bushing 2 ... Cable 3 ... Board wall 4, 6, 13 ... Insulation layer 5, 14, 15 ... Electrode 7 ... Stress cone 8, 16 ... Spring 9 ... Protection tube 11, 25 ... Insulation collar 12, 21 ... Grounding layer 18 ... pressing plate 20 ... metal cylinder electrode 22 ... resistive layer 23 ... semiconductive layer

Claims (7)

[Claims] 1. A power supply device, comprising:
In a bushing in which an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer, and in a cable end portion in which a cable end portion of the electrode is electrically connected, the cable end portion is connected to the cable end portion from the cable end side. A metal cylinder electrode is provided so as to be inserted toward the insulating layer and form an air gap with a constant gap length with respect to the outer periphery of the insulating layer, and the metal cylinder electrode is placed from one axial end of the insulating layer. A grounding layer is formed by wrapping a predetermined distance, and forming a grounding layer from an end on the outer peripheral surface of the insulating layer opposite to the end of the cable to near immediately below the metal cylindrical electrode. Insulating structure. 2. The air gap according to claim 1, wherein a voltage characteristic of an air gap between the metal cylinder electrode and the ground layer is higher than a voltage characteristic of an air gap formed between the metal cylinder electrode and the insulating layer. 2. The insulation structure of a cable terminal section according to claim 1, wherein a creepage distance is set. 3. It is fixed to a fixing portion such as a switch gear,
An insulating layer of the bushing is connected to a cable at a bushing in which an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer, and at a cable end portion at which a cable end of the electrode is electrically connected. An insulating structure at a cable terminal end, wherein an insulating layer is provided at an end on the side, electrodes are provided at both ends of the insulating layer, and a resistance layer or a protective layer is formed on the surface. 4. It is fixed to a fixing portion such as a switch gear,
A bushing in which an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer, and a cable end portion in which a cable end portion of the electrode is electrically connected, the outer peripheral surface of the insulating layer, A ground layer is formed from an axial end opposite to the cable end to a portion except near the cable end, and a semiconductive layer is formed on an outer peripheral surface of the insulating layer where the ground layer is not formed. An insulating structure at a cable end portion, wherein the insulating structure is formed. 5. It is fixed to a fixing part such as a switch gear,
A bushing in which an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer; and a cable end portion in which a cable end portion of the electrode is electrically connected, the outer peripheral surface of the insulating layer of the bushing. Forming a grounding layer on all portions of the portion except for the vicinity of the cable end from the axial end opposite to the cable end, and forming an outer peripheral surface of an insulating layer of the bushing; An insulating structure at a cable end portion, wherein a cylindrical protective cap made of a semiconductive material is attached to a portion where the protective cap is not formed, and the insulating layer of the bushing is in close contact with the protective cap. 6. It is fixed to a fixing portion such as a switch gear,
A bushing in which an outer peripheral portion of an electrode connected to an electric device or the like is surrounded by an insulating layer, and a cable end portion in which a cable end portion of the electrode is electrically connected, the outer peripheral surface of the insulating layer, A ground layer is formed from the axial end opposite to the cable end to the cable end, and a new high-dielectric-constant insulating material is provided between the cable end and the bushing insulating layer. An insulating structure at a cable end portion, wherein the formed insulating layer is sandwiched between the cable end and the insulating layer of the bushing. 7. A zinc oxide element is buried in a newly provided insulating layer between the cable end according to claim 6 and the insulating layer of the bushing, and the cable end and the insulating layer of the bushing are provided. An insulating structure at a cable end portion, which is integrally fixed.