JP3283941B2 - Mold bushing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead portion of a main circuit conductor of an electric device used for, for example, a switchgear.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration diagram of a gas insulated switchgear as an example of a switchgear as a power receiving and distributing facility. In the figure, the inside of a box 1 whose outer periphery is hermetically surrounded by metal is
A breaker room 1a at the front and a busbar room 1b at the rear are partitioned by a partition wall 2 provided vertically near the left front side in the figure.
1b is filled with, for example, sulfur hexafluoride gas (hereinafter referred to as insulating gas).

The circuit breaker 3 is accommodated in the circuit breaker room 1a, and an insulating spacer 9 is mounted in a through hole (not shown) in the partition 2 and the circuit breaker 3 is connected to the front side. Have been.

A disconnector 4A whose front terminal is connected to the rear of an upper insulating spacer 9 via a connecting conductor 8 is attached to the ceiling of the busbar room 1b. Are connected to the bus bar 5 attached to the rear insulator 6 via the connection conductor 8. The bus 5 connects to an adjacent board.

On the other hand, a disconnector 4B having substantially the same shape as the disconnector 4A whose front terminal is connected to the rear of the lower insulating spacer 9 via a connecting conductor 8 is attached to the bottom of the busbar chamber 1b. The terminal at the rear of the disconnector 4B is connected via a connecting conductor 8 to the upper terminal of a cable head 7 attached to the rear of the bottom.

FIG. 7 is a cross-sectional view of the insulating spacer 9 shown in FIG. In the figure, a substantially central portion of an insulating layer 11 in which a center conductor 10 is integrally cast with an insulating material made of, for example, epoxy resin is fixed to a flange 12 attached to the partition wall 2. Also, to alleviate the electric field at the tip of the flange 12,
On the insulating layer 11 side, a U-shaped groove 11a having a substantially U-shape is disposed so as to face the flange 12, and a ground layer 13 made of a conductive paint or the like is provided. The end portion 11b of the insulating layer in contact with the center conductor 10 and the surrounding insulating gas is, for example,
8717, the angle θ of the insulating layer 11b is about 90 degrees.
It has become a degree. This is because the insulation thickness of the insulation layer 11 in the substantially central portion and the insulation thickness in the vicinity of the lead-out portion of the center conductor 10 are substantially the same so that the dielectric strength in the penetration direction of the insulation layer 11 is uniform and the creepage insulation distance is increased. is there.

On the other hand, the relative dielectric constant of the insulating layer 11 is about 5 in the case of epoxy resin, and the relative dielectric constant of the surrounding insulating gas is about 1. That is, the relative dielectric constant differs along the surface of the insulating layer.

[0008]

When the two or more insulating media have different relative dielectric constants as described above, the equipotential lines at the boundary are refracted, and the electric field intensity is disturbed. That is, the electric field strength is disturbed on the surface of the insulating layer 11. Looking at this component, since the angle θ of the insulating layer 11 is about 90 degrees, almost the tangential direction is along the surface near the center conductor 10, and the normal direction is small.

In general, the breakdown voltage largely depends on the electric field strength. The components of the breakdown voltage are the breakdown electric field in the normal direction and the sustaining electric field in the tangential direction along the creeping surface. For this reason, the breakdown electric field may be small and the breakdown voltage may increase. However, if the electric field strength in the tangential direction is large, the streamer on the creeping surface is easily extended. Further, since dust and the like easily adhere to the creeping surface, the streamer is further easily stretched, so that the electric field intensity on the creeping surface is further disturbed, and as a result, the breakdown voltage is reduced.

When the surface of the insulating layer 11 is sufficiently long, the absolute value of the electric field strength is lower than the allowable value, so that the breakdown voltage does not decrease even if the component in the tangential direction is large. However, when the creepage distance is reduced and the size is reduced, the creepage electric field strength does not exceed the allowable value but approaches. Therefore, dust and dirt easily adhere to the creepage surface, and it is not possible to maintain a completely clean surface condition.If the electric field strength in the tangential direction is large, the streamer on the creepage surface is easily elongated, and the breakdown voltage is reduced. become. For this reason, by making the creepage distance relatively large, the developed electric field strength of the creepage is suppressed to a certain ratio or more with respect to the allowable value,
Miniaturization was difficult. In this way, if the insulation distance of one storage device is increased, it spreads to other storage devices, and as a result, the overall shape of the device is increased. SUMMARY OF THE INVENTION It is an object of the present invention to provide a main circuit conductor lead portion of an electric device with improved breakdown voltage.

[0011]

In order to achieve the above object, the present invention provides a method of casting a center conductor with an insulator and connecting the center conductor to the center conductor.
Angle between the end of the insulating layer and the axis of the center conductor
Below, and along the edge of the insulating layer where the center conductor is led out.
The point is that the electric field strength in the normal direction and the electric field strength in the tangential direction are balanced.

[0012]

In these configurations, the insulation in contact with the center conductor is provided.
The angle between the end of the layer and the axis of the central conductor is set to 50 degrees or less,
Since the electric field strength in the normal direction and the electric field strength in the tangential direction on the surface along the end of the insulating layer from which the center conductor is led out are balanced, the breakdown voltage can be improved.

That is, the angle of the insulating layer with respect to the center conductor is
If it is 90 degrees, equipotential lines intersect at substantially right angles, so that the tangential component becomes large on the surface of the insulating layer. Conversely, if the angle of the insulating layer is almost 0 degrees, the component in the normal direction becomes large. Looking at the component of the electric field strength at this angle at all angles,
At a certain angle, a point where the components intersect occurs. In this regard, while the absolute value of the electric field strength is suppressed,
This is the point where the mutual components are at the minimum value, and the breakdown voltage can be improved.

[0014]

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

FIG. 1 is a cross-sectional view of the insulating spacer 9 in FIG. An insulating layer 14 in which an insulating material such as an epoxy resin is cast is formed around the center conductor 10, and a substantially central portion of the insulating layer 14 is fixed to the flange 12. Also,
A U-shaped groove 14a is provided in the ground-side insulating layer 14 so as to face the flange 12, and the U-shaped groove 14a is provided in the ground layer 13 made of conductive paint.
Is applied to alleviate the electric field on the ground side as in the prior art. Here, the insulating layer end 14 in contact with the center conductor 10
The angle θ of b is 50 degrees or less. The relative permittivity of the insulating layer 14 is about 5, and the surrounding insulating gas has a relative permittivity of 1.

FIGS. 2 and 3 show the electric field intensity distribution along the surface of the insulating layer 14 in such a configuration. FIG. 2 is a characteristic diagram of the electric field intensity when the angle of the insulating layer 14 is changed, and FIG. 3 is a vector diagram of the electric field intensity for explaining the components of the electric field intensity. In FIG. 3, the electric field strength in the normal direction is E _H and the electric field strength in the tangential direction is E _S with respect to the absolute value E _O of the electric field strength. Θ is the angle of the insulating layer 14 in contact with the center conductor 10.

In these figures, it can be seen that the electric field intensity changes depending on the angle of the insulating layer 14. That is, the angle θ
Increases, the absolute value E _O rises more rapidly than approximately 50 degrees or more, and E _S also rises accordingly. Conversely, E _H decreases as angle θ increases, and E _S and E _H
Cross at 50 degrees. Further, theta is the E _S <E _H in E _S> E _H next, theta = 50 degrees is 50 degrees or more.

As a result, the discharge developing electric field on the surface, E,
To suppress _S , the angle θ needs to be 50 degrees or less,
In this case, the breakdown voltage depends on E _H. For this reason, even if the creeping surface is slightly dusty or uneven, the streamer is prevented from extending, and the electric field strength on the creeping surface is not disturbed. The breakdown voltage depends on E _H , and the electric field strength and the breakdown voltage can be matched. Here, conversely, when the angle θ is set to 50 degrees or more, the E _H seems to decrease and the breakdown voltage seems to increase, but on the surface, the discharge develops and the electric field intensity is disturbed, and as a result, the breakdown voltage increases. Will decrease.

From these, when the angle θ is equal to or less than 50 degrees, the development of the discharge on the creeping surface can be prevented, so that the electric field strength can be increased to near the allowable electric field strength. In other words, since the dielectric strength can be maintained satisfactorily, the insulation distance on the creeping surface can be shortened, and the size of the insulating spacer 9 can be reduced. Note that the diameter of the center conductor 10, the outer diameter of the ground layer 13, and the U-shaped
If the optimum shape of b is found, the surface electric field strength
From the ground layer 13 to the ground layer 13 to achieve a significant reduction in size.However, in general, the electric field strength of the center conductor 10 becomes higher than that of the ground layer 13, so that the component of the electric field strength on the high voltage side is balanced. An effective reduction can be achieved if this is achieved.

Next, FIG. 4 shows a through-type bushing in which a secondary winding is mounted on the ground side. In the insulating layer 17 in which the center conductor 15 and the secondary winding 16 are integrally cast, the center conductor 15 is Derive
By setting the angle of the insulating layer 17a to 50 degrees or less,
The component of the electric field strength is balanced between the normal direction and the tangential direction.
Can be . Reference numeral 18 denotes a contact, and 19 denotes a connection conductor for connecting to another device. In such a bushing, since the buried metal is large, the insulating layer 17 may be made of a soft material such as rubber. In this case, the relative dielectric constant is, for example, 2 to 3 for silicone rubber, but since the relative dielectric constants of the insulating layer 17 and the surrounding insulating medium are different,
On the surface, the equipotential lines are refracted and the electric field strength is disturbed. On such a creeping surface having a lower relative dielectric constant, the progress of discharge on the creeping surface can be prevented by balancing the components of the electric field intensity. In addition, even when the secondary winding 16 is on the ground side and the electric field strength distribution with the center conductor 15 is different from that of a general mold bushing, the electric field strength on the high voltage side where the electric field strength is high among the creeping surfaces is suppressed. If the components are balanced, the dielectric strength can be improved.

FIG. 5 shows the case of an instrument transformer. Even when the primary winding 20 and the secondary winding 21 and the main circuit lead wire 22 leading out of the primary winding 20 are cast and the insulating layer 23 is formed, the main circuit lead wire is also used. By setting the angle of the insulating layer end 23a of the protruding portion 22 to 50 degrees or less, the electric field intensity on the creeping surface can be suppressed. The main circuit lead wire 22 is generally a covered electric wire using a stranded wire because of its small current carrying capacity, and is provided with a coating 24. The component of the electric field strength of the portion 23a can be balanced and suppressed. The relative permittivity of the insulating layer 23 and the coating 24 is higher than the relative permittivity of the insulating gas of about 1,
The refraction of equipotential lines along the surface of the insulating layer 23 increases, disturbing the electric field strength.
In comparison with 24, which is as high as several tens of kV / mm, the insulating gas is as low as 8.9 kV / mm at atmospheric gas pressure, so the insulation breakdown on the creepage surface is determined by the insulating gas. The breakdown voltage depends. Reference numeral 25 denotes a secondary terminal for detecting a voltage from the secondary winding.

[0022] As another example, in the insulating medium using air or N ₂ gas, the dielectric constant decreased relative to the insulator, and since the dielectric strength is small, corresponds to the lead-out portion of the main circuit conductor insulation If the angle of the object is less than 50 degrees, the normal
The electric field strength in the direction and the tangential direction is balanced , the electric field strength is suppressed, the breakdown voltage is improved, and the size can be effectively reduced.

[0023]

As described above, according to the present invention , the center conductor
By balancing the electric field strength in the normal direction and the electric field strength in the tangential direction on the surface of the end of the insulating layer from which the electric field is derived , the electric field intensity can be suppressed, and the breakdown voltage on the surface of the insulator can be improved.

Furthermore, according to the present invention , it is in contact with the center conductor.
Since the angle between the end of the insulating layer and the axis of the center conductor is set to 50 degrees or less, the dielectric strength can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an insulating spacer showing one embodiment of the present invention.

FIG. 2 is a diagram for explaining the characteristics of FIG. 1;

FIG. 3 is a diagram for explaining the characteristics of FIG. 1;

FIG. 4 is an enlarged sectional view of a main part of a through-type bushing showing another embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of an instrument transformer according to another embodiment of the present invention.

FIG. 6 is a side view of a typical switchgear.

FIG. 7 is a cross-sectional view of the insulating spacer 9 of FIG.

[Explanation of symbols]

 9 ... insulation spacer, 10 ... center conductor, 14 ... insulation layer

────────────────────────────────────────────────── (5) References JP-A-1-309217 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02B 1/20 H01B 17/26

Claims (1)

(57) [Claims] 1. A center conductor is cast with an insulator, and said center conductor is
Angle between the end of the insulating layer in contact with the body and the axis of the central conductor
Is less than 50 degrees and the insulation from which the center conductor is led out
Meaux and the electric field strength in the normal direction of the electric field strength and the tangential direction of the creeping of the layer ends, characterized in that into a balanced
Ludo bushing .