JPH11273475A - Polymer bushing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer bushing which does not generate partial electric discharge despite rain precipitation during the service and can prevent deterioration due to partial discharge irrespective of the degree of yield strength of a sheath material for the partial discharge. SOLUTION: A polymer bushing 1 is composed of an insulating tube 11, a center conductor 21 furnished penetrating the center of the tube 11, and an electric field relieving means 31 installed between the tube 11 and center conductor 21 in a location below the tube 11, wherein the tube is filled with an insulating medium consisting of a gas or oil, and the means 31 is composed of an inner grounding electrode 32 in cylindrical form furnished concentrically around the center conductor 21, a capacitor rod 33 fixed to the top of the electrode 32 and extending upward, and a conductor ring 34 supported by the rod 33 concentrically to the center conductor 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polymer insulator tube,
A center conductor penetrating the inner center of the polymer insulator,
The present invention relates to a polymer bushing for substation equipment, comprising electric field relaxation means provided between a polymer insulator and a center conductor and below the polymer insulator, and filled with an insulating medium made of gas or oil inside the polymer insulator. is there.

[0002]

2. Description of the Related Art Conventionally, a polymer insulator, a center conductor penetrating the center of the polymer insulator, and an electric field relaxation means provided between the polymer insulator and the lower portion of the polymer insulator are provided. There are known various types of polymer bushings for substation equipment in which a polymer insulator tube is filled with an insulating medium made of gas or oil.
FIG. 8 is a diagram showing a configuration of an example of a conventional polymer bushing. In the example shown in FIG.
Reference numeral 1 denotes a polymer insulator 61, a center conductor 71 penetrating through the center of the polymer insulator 61, and a polymer insulator 61
And a central conductor 71 and an electric field relaxation means 81 provided below the polymer insulator tube 61.

[0003] The polymer insulator 61 is formed of a tapered FRP.
It is composed of a tube 62, a jacket 63 made of, for example, silicone rubber provided around the FRP tube 62, and upper and lower flange members 64-1 and 64-2 gripped and fixed to both ends of the FRP tube 62. . The outer cover 63 is composed of a body 65 contacting the FRP cylinder 62 and a plurality of caps 66 erected from the body 65. The electric field relaxation means 81 is configured by providing a cylindrical intermediate potential electrode 82 and a cylindrical internal ground electrode 83 from the center side concentrically.
The intermediate potential electrode 82 is connected to the internal ground electrode 8 via a plurality of insulating spacers 84 and a flange portion 85 of the intermediate potential electrode 82.
3 fixedly supported.

An upper lid 67 is provided on the upper flange metal fitting 64-1, and a terminal 68 used for connecting the center conductor 71 to an external device is provided on the upper lid 67. The lower flange metal fitting 64-2 is hermetically attached to a wall (not shown) through which the center conductor 71 is inserted. The airtight internal space 52 is filled with an insulating medium made of gas or oil. In the polymer bushing 51 having the above-described structure, the electric field in the direction along the length of the polymer insulator 61 is reduced, thereby controlling the partial discharge on the surface of the polymer insulator 61 and thereby improving the withstand voltage performance.

[0005]

Although there was almost no problem when the insulator tube was made of porcelain, a polymer in which the outer cover 63 was made of a water-repellent insulating material (EPDM, EVA, silicone rubber, etc.). It has been found that the following problems occur when the insulator tube 61 is used. That is, when raindrops adhere to the surface of the jacket during rainfall, the jackets become independent granular waterdrops because the jacket has water repellency. FIG. 9 obtained by simulating a part having a relatively high electric field, that is, a state of electric field concentration
In other words, there is a problem that a partial discharge occurs in the space between the granular water droplets at a position indicated by Emax, in other words, near the height of the tip of the intermediate potential electrode 82.

It is generally said that if this partial discharge continues to be violent for a long period of time, the organic material may be deteriorated. Therefore, it is necessary to prevent such partial discharge from occurring. Of course, if it is an organic material, it does not necessarily deteriorate due to this kind of partial discharge. For example, if the material is silicone rubber, it does not deteriorate much even when exposed to a discharge of a little energy due to its high heat resistance. . Whether or not deterioration occurs depends on the degree of discharge and the resistance of the material to discharge. Therefore, in order to prevent deterioration due to partial discharge, it is conceivable to select and use a material having a high discharge resistance, but generally, a material having a high discharge resistance is expensive, so partial discharge occurs. If a material having a high discharge resistance is used so as not to cause deterioration under use in a state, the cost increases.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a polymer bushing which does not generate a partial discharge even when rain occurs during use. Another object of the present invention is to provide a polymer bushing capable of preventing partial discharge deterioration regardless of the degree of proof strength of the jacket material against partial discharge.

[0008]

According to the present invention, there is provided a polymer bushing comprising: a polymer porcelain; a center conductor penetrating the center of the polymer porcelain; and a lower portion between the polymer porcelain and the center conductor. And an electric field alleviating means provided on the side, and in a polymer bushing in which an insulating medium made of gas or oil is filled in a polymer insulator tube, the electric field alleviating means is provided concentrically around a central conductor in a cylindrical internal ground. An electrode, a capacitor rod fixed to the upper end of the internal ground electrode and extending upward, and a conductor ring supported by the capacitor rod concentrically with the center conductor.

According to the present invention, the configuration of the electric field relaxation means is improved, and a cylindrical internal ground electrode provided concentrically around the center conductor, a capacitor rod fixed to the upper end of the internal ground electrode and extending upward, Composed of a center conductor and a conductor ring supported concentrically by a capacitor rod, the state of the electric field on the outer surface of the polymer insulator can be controlled appropriately, preventing the occurrence of partial discharge from water droplets even in rainy weather Yes, there is no concern about jacket deterioration. As a result, it is not always necessary to use a high-cost material with high resistance to partial discharge for the jacket, and a polymer bushing that is not subject to deterioration due to partial discharge from water droplets attached in rainy weather regardless of the type of the jacket material. Obtainable.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a configuration of an example of a polymer bushing of the present invention. In the example shown in FIG. 1, a polymer bushing 1 includes a polymer insulator 11 and a center conductor 2 provided through the center of the polymer insulator 11.
1 and electric field relaxation means 31 provided between the polymer insulator 11 and the center conductor 21 and below the polymer insulator 11. The polymer porcelain tube 11 includes a tapered FRP tube 12, a jacket 13 made of, for example, silicone rubber provided around the FRP tube 12, and an upper flange fitting 14-1 and a lower flange fitting gripped and fixed to both ends of the FRP cylinder 12. 14-2. The jacket 13 is F
It is composed of a body part 15 that comes into contact with the RP cylinder 12 and a plurality of caps 16 standing upright from the body part 15. An upper lid 17 is provided on the upper flange fitting 14-1, and the center conductor 21 is
And a terminal 18 used for connection with an external device. The lower flange fitting 14-2 is hermetically attached to a wall (not shown) through which the center conductor 21 is inserted. The airtight internal space 2 is filled with an insulating medium made of gas or oil.

The above configuration is the same as the conventional polymer bushing. A feature of the polymer bushing of the present invention is that the configuration of the electric field relaxation unit 31 is different from the conventional configuration. That is, in the present invention, the electric field relaxation means 31 includes a cylindrical internal ground electrode 32 provided concentrically around the center conductor 21, a capacitor rod 33 fixed to the upper end of the internal ground electrode 32 and extending upward, It comprises a conductor 21 and a conductor ring 34 concentrically supported by a capacitor rod 33.

In the example shown in FIG. 1, the capacitor rod 33 is formed by stacking a plurality of solid capacitor elements 41 each having a high magnetic permeability. The conductor ring 34 is supported by a plurality of capacitor rods 33, and as shown in FIG.
The plurality of capacitor rods 33 are arranged so as to have the following. The number of condenser rods shall be small. The small number is such that the ratio of the apparent area viewed from the side occupied by the space 42 is relatively larger than the ratio of the apparent area viewed from the side occupied by the capacitor rod.

Regarding the conductor ring 34, the conductor ring 3
4 is smaller than the diameter of the internal ground electrode 32 so that the present invention can be achieved without increasing the size of the bushing itself. In addition, the conductor ring 34 is located at a place where the conductor ring 34 is retracted inward from the inner surface of the insulator tube by a required distance in terms of electric field distribution. With the above configuration, the direction of the electric field on the outer surface of the jacket at the height near the conductor ring 34 is not the creepage direction of the outer shell like the conventional polymer bushing but is oblique, and the creepage direction component of the electric field is Is significantly reduced than that of the polymer bushing. The reduction of the creepage direction component of the electric field is the key to suppressing the water droplet corona. Next, in the present invention, the reason why the electric field relaxation means 31 of the present invention having the above configuration can prevent the occurrence of partial discharge from water droplets will be described.

First, conventionally, "Aging of Non-Ceramic"
Insulators due to Corona from Water Drops ", AJPh
ilips, DJChilds, HMSchneider, CIGRE WG 33-97 (T
F04.07) 5IWD and others describe the following facts about the behavior of water droplets attached to a conventional polymer bushing. (1) Partial discharge comes out from the tip of a water droplet. (2) Since the electric field is concentrated at the tip of the water droplet, the electric field is higher than the surrounding area. (3) In an actual power transmission insulator, an electric field is applied in the length direction. In other words, the electric field is in a direction of the creeping surface in the trunk of the jacket and in a direction perpendicular to the surface in the shade. The degree of electric field concentration is greater in the creeping electric field, so that the body is the only part where the electric field is high enough to cause partial discharge. (4) Water droplets adhering to the trunk are stretched in the direction of the electric field by the electrostatic force of the creeping electric field and deformed into a flat shape (FIG. 3).
(A), (b)). (5) Flattening increases the electric field concentration at both ends. As a result, partial discharge at the tip is more likely to occur. (6) According to experimental observations, when the electric field is gradually increased, the state in which the water droplets attached to the body are extended in the direction of the electric field by electrostatic force is not continuous with the increase in the electric field, It has a discontinuous aspect in which it does not deform halfway, but suddenly deforms when the electric field reaches a certain level. If the field falls, it will gradually return, but not completely.

Based on the above facts, the inventor has made the following studies. (1) In order to prevent the partial discharge from being generated from the water droplet, it is effective to prevent the micro electric field value from taking into account the electric field concentration at the tip of the water droplet so as not to exceed a predetermined value. (2) The water droplets on the body, whose electric field direction is the creeping direction, tend to be stretched in the creeping direction by the electrostatic force of the electric field. The water droplets endure without deformation if the creepage direction component of the electric field is sufficiently small. As a result, since the water droplet does not flatten, the electric field concentration at the end of the water droplet does not increase so much, and no partial discharge occurs. Even if the absolute value of the electric field, which is a vector value, is high, it is effective to suppress the component in the creeping direction to be small to suppress the occurrence of partial discharge from water droplets. That is, means for changing the direction of the electric field from the creeping direction to the oblique direction is effective. (3) Once the water droplet is stretched in the creepage direction by the electric field and flattened and a partial discharge occurs, even if the electric field is artificially lowered, the shape of the water droplet is delayed and does not return to the original shape. The concentration is kept high, and the next time an electric field is applied, the start of the partial discharge will occur from a lower value. (4) Conversely, if the direction of the electric field is made sufficiently oblique, the direction in which the water droplets are going to deform will not extend in the creepage direction but will extend in the air obliquely, and consequently will be closer to a spherical shape (Fig. (A), (b)). Therefore, depending on the conditions, the concentration of the electric field may not decrease but may even decrease. Since partial discharge is unlikely to occur unless the electric field is concentrated, the oblique direction of the electric field is effective in suppressing partial discharge from water droplets in this sense as well.

[0016] Based on the above examination results, the configuration of the present invention could be obtained. Hereinafter, the reason for adopting the configuration of the present invention will be described. (1) The conventional cylindrical intermediate potential electrode is eliminated, and a conductor ring made of a conductor material is used instead. This is because the electric field does not become oblique in a cylinder, but it is possible in a ring shape. (2) The conductor ring is supported above the internal ground electrode via a capacitor rod. This is because, when the conductor ring is held by a normal spacer or the like, the electric potential is increased as shown in FIG. 5 showing the result of the electric field calculation for the polymer bushing in which the capacitor rod is replaced with an insulator in the structure of the present invention. As a result, the influence of the electric field on the external creeping surface is reduced, and the inclination of the electric field cannot be sufficiently achieved. When supported on the internal ground electrode via a capacitor having a sufficiently large capacity, the potential of the conductor ring becomes close to the ground potential, and the electric field direction is oblique. Also, do not connect with conductor bars instead of capacitor bars. When the connection is made by the conductor rod, the potential of the conductor ring becomes equal to the ground potential, and as a result, the electric field in the creeping direction on the surface of the insulator above the ring-shaped electrode is increased.

(3) In a preferred embodiment, the diameter of the conductor ring is smaller than the diameter of the internal ground electrode. This is because if the diameter of the conductor ring and the diameter of the cylindrical internal ground electrode are the same, the outer space of the cylindrical internal ground electrode will be as large as the required gap between the conductor ring and the inner surface of the insulator tube. This is because if only the conductor ring is moved inward, the necessity is eliminated. In that case, the dielectric strength between the conductor ring and the center conductor is reduced by reducing the insulation distance between them, but the potential of the conductor ring is higher than the ground potential, so the voltage applied between the conductor ring and the center conductor is reduced. Since is smaller than the voltage applied between the internal ground electrode and the center conductor, insulation coordination can be achieved by adjusting the degree of inward reflection within the range of the ratio. Therefore, the present invention can be achieved without increasing the size of the polymer bushing itself, and the compactness can be achieved.

(4) In a preferred embodiment, the capacitor rod has a stacked structure of solid capacitor elements. In a further preferred embodiment, the conductor ring is supported by the plurality of capacitor rods, and the plurality of capacitor rods are arranged so that the center conductor has a space that can be seen from between the capacitor rods when viewed from the side, and further occupies the space. The ratio of the apparent area viewed from the side is relatively larger than the ratio of the apparent area viewed from the side occupied by the capacitor rod. This is a means to create a situation where the electric field part is substantially composed of only the conductor ring and the internal ground electrode. If the capacitor rod has a cylindrical shape or a large number of rods, the electric field is not much different from that of the conventional polymer bushing as shown in FIG. Is not achieved. If the space between the conductor ring and the internal ground electrode is substantially just a space,
As shown in FIG. 6, the electric field calculation result for the polymer bushing of the present invention shows that the electric potential of the center conductor affects this space portion, so that the electric field portion is deformed and the electric field direction on the surface of the jacket is oblique. Since a solid capacitor element usually has a dielectric constant of about several thousands, a large capacitance can be formed by using a small number of elements, and the number of used capacitor rods can be reduced.

(5) In a preferred embodiment, the conductor ring is located at a position withdrawn from the inner surface of the insulator tube by a required distance in an electric field distribution. This is to prevent a problem that local electric field concentration around the conductor ring appears as it is in the vicinity of the jacket due to the approach of the insulator tube and the conductor ring. When such local concentration appears, the absolute value of the electric field increases even if the obliqueness of the electric field is achieved, and a partial discharge due to this is rather generated. On the other hand, the internal ground electrode may be close to the inner surface of the insulator tube. This is because the presence of a conductor ring having an upper intermediate potential alleviates the electric field around the tip of the internal ground electrode and the absolute value has already been reduced. Does not occur.

[0020]

EXAMPLE A gas-insulated polymer bushing with a rated voltage of 550 kV was prototyped for the configuration of the present invention (FIG. 1) and the configuration of the conventional example (FIG. 7). An electrical test of a rainfall simulation was performed on the prototype gas-insulated polymer bushings of the present invention and the conventional example, and the partial discharge inception voltage was obtained. The results are shown in Table 1 below.

The electrical test for simulating rainfall was conducted as follows. The bushing of the conventional structure and the bushing of the present invention were respectively set upright in the electrical test chamber as shown in FIG. The inside of the bushing was filled with SF ₆ gas up to 0.4 MPa. Water droplets for simulating rainfall were applied by a water injection device so as to hit the bushing at an angle of 45 °. The amount of water is 3 mm / min, and the specific resistance of water is 10,000
It was adjusted to Ωcm. Next, the lighting of the electric test room was turned off and the room was darkened. After the observer's eyes became dark, voltage application was started. The voltage is applied from 0V
Stopped at 0 kV and held for 1 minute. The appearance of the visible corona of the bushing was observed with binoculars. Thereafter, while observing the visible corona with binoculars, the pressure was applied at an interval of 10 kV / 1 step, and the voltage was applied for 1 minute each. Then, when the corona was first visually observed through the binoculars, the voltage was lowered to 0V. When the starting voltage of the corona, which was first visually observed, was higher than the ground voltage 318 kV, the voltage was applied again, the voltage was maintained at 318 kV for 6 hours, and it was observed whether or not partial discharge started during that time. As a result, visible corona was first observed at 250 kV in the bushing of the conventional structure. On the other hand, in the bushing of the present invention, visible corona was first observed at 350 kV, and after returning to 0 V once, 318
kV was applied for 6 hours, during which time no visible corona was generated.

[0022]

[Table 1]

Since the ground voltage applied to the polymer bushing having the rated voltage of 550 kV is 550/3 ^1/2 = 318 kV, the results shown in Table 1 indicate that a partial discharge occurs in the polymer bushing of the conventional configuration in rainy weather. It can be seen that partial discharge does not occur in the polymer bushing of the configuration of the present invention.

[0024]

As is apparent from the above description, according to the present invention, the structure of the electric field relaxation means is improved so that the cylindrical internal ground electrode provided concentrically around the center conductor and the internal ground Consisting of a capacitor rod fixed to the upper end of the electrode and extending upward and a conductor ring supported by the capacitor rod concentrically with the center conductor, the state of the electric field on the outer surface of the polymer insulator can be controlled appropriately. Thus, the occurrence of partial discharge from water droplets can be prevented even in rainy weather, and there is no fear of deterioration of the jacket. As a result, it is not always necessary to use a high-cost material with high resistance to partial discharge for the jacket, and a polymer bushing that is not subject to deterioration due to partial discharge from water droplets attached in rainy weather regardless of the type of the jacket material. Obtainable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of a polymer bushing of the present invention.

FIG. 2 is a side view of a conductor ring, a capacitor rod, and an internal ground electrode constituting the polymer bushing of the present invention.

FIG. 3 is a diagram for explaining a relationship between an electric field and a change in shape of a water droplet in a conventional polymer bushing.

FIG. 4 is a diagram for explaining a relationship between an electric field and a change in shape of a water droplet in the polymer bushing of the present invention.

FIG. 5 is a diagram showing a result of an electric field calculation for a polymer bushing having a configuration in which a capacitor rod is replaced with an insulator in the configuration of the present invention.

FIG. 6 is a diagram showing a result of an electric field calculation for the polymer bushing of the present invention.

FIG. 7 is a diagram showing a state of an electrical test of rainfall simulation in the example of the present invention.

FIG. 8 is a diagram showing a configuration of an example of a conventional polymer bushing.

FIG. 9 is a diagram showing a result of an electric field calculation for a conventional polymer bushing.

[Explanation of symbols]

1 Polymer bushing, 11 Polymer insulator, 12
FRP cylinder, 13 jacket, 14-1 upper flange bracket,
14-2 Lower flange bracket, 15 torso, 16 shades, 1
7 Top cover, 18 terminals, 21 center conductor, 31 Electric field relaxation means, 32 Internal ground electrode, 33 Capacitor rod, 3
4 conductor ring, 41 solid capacitor element, 42 space

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[Procedure amendment]

[Submission date] April 24, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

Claims (5)

[Claims] 1. A polymer insulator, a center conductor penetrating the inner center of the polymer insulator, and an electric field relaxation means provided between the polymer insulator and the center conductor and below the polymer insulator. In a polymer bushing in which an insulating medium made of gas or oil is filled in a polymer insulator tube, an electric field relaxation means is fixed to a cylindrical internal ground electrode provided concentrically around a center conductor and to an upper end of the internal ground electrode. A polymer bushing comprising a capacitor rod extending upward and a conductor ring supported by the capacitor rod concentrically with the center conductor. 2. The polymer bushing according to claim 1, wherein the diameter of the conductor ring is smaller than the diameter of the internal ground electrode. 3. The polymer bushing according to claim 1, wherein the capacitor rod has a stacked structure of solid capacitor elements. 4. The capacitor ring according to claim 1, wherein the conductor ring is supported by a plurality of capacitor rods, and the plurality of capacitor rods are arranged so that a central conductor has a space seen from between the capacitor rods when viewed from the side. Item 2. The polymer bushing according to item 1. 5. The polymer bushing according to claim 4, wherein the ratio of the apparent area viewed from the side occupied by the space is relatively larger than the ratio of the apparent area viewed from the side occupied by the capacitor rod.