JPH0731044A - Dielectric resin molded item - Google Patents

Abstract

PURPOSE:To enhance dielectric strength of a dielectric resin unit containing a filler formed on the outer periphery of a cable insulator by providing an embedded electrode for applying voltage to the dielectric resin unit and forming a field relax layer around the embedded electrode. CONSTITUTION:Voltage is applied to a dielectric resin unit 15 through an embedded electrode 8 to cause electrophoresis of the filler in the unit 15 thus forming a field relax layer 17. Consequently, the electric field applied to the unit 15 is relaxed. Even when a strong electric field is applied to the vicinity of the edge part 8a of an electrode embedded in a power cable 1, for example, the field is relaxed by the field relax layer 17. This structure enhances the dielectric strength of the dielectric resin unit 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating resin molded product used for electric wires, terminals of power cables, connecting portions and the like.

[0002]

2. Description of the Related Art In recent years, insulating resin moldings such as epoxy resin have been widely used in electric equipment such as cable terminals and connecting portions. For example, as the most electrically severe example, as an insulating resin molded product used in the field of cables,
Used for prefabricated connection of cross-linked polyethylene insulated PVC sheath cable (CV cable). This prefabricated type connection portion is regarded as a promising alternative to the molded type connection portion in the 275 to 500 kV ultrahigh voltage CV cable because of its short construction period.

As shown in FIG. 3, the prefabricated type connecting portion includes a premolded insulator 2 inserted into the outer periphery of an end portion of a power cable 1, and an insulating resin unit 3 which is pushed into the premolded insulator 2. Have. Power cable 1
Has an inner conductor 4 and a cable insulator 5 made of cross-linked polyethylene (XLPE) that covers the inner conductor 4, and has a structure in which the inner conductor 4 is projected from an end portion of the cable insulator 5. .

The pre-molded insulator 2 covers the periphery of the end of the cable insulator 5, an insulating rubber 6 which forms an electric field relaxation insulating reinforcing layer, and a semiconductive rubber which pushes the insulating rubber 6 toward the insulating resin unit 3 side. 7 and. Insulating rubber 6
Is made of ethylene propylene rubber, silicone rubber, or the like.

The insulating resin unit 3 is formed into a substantially cylindrical shape whose end is pushed into the premolded insulator 2. The insulating resin unit 3 has an embedded electrode 8 inside.
Is embedded. The embedded electrode 8 is arranged around the inner conductor 4 protruding from the cable insulator 5, and is electrically connected to the inner conductor 4 of the power cable 1. Here, considering that the material of the insulating resin unit 3 is a cast product for electrical insulation having a large thickness, the main heat / curing agent having a small hardening heat and a slow hardening speed is used so that the residual strain becomes small. A combination of bisphenol A / anhydride and fillers such as silica and alumina are usually used.

A method of manufacturing such a prefabricated type connecting portion will be described. First, the premolded insulators 2 are inserted into the ends of the pair of power cables 1, respectively. Then, the internal conductors 4 of each power cable 1 are arranged to face each other, and
Embedded electrodes 8 are arranged on the outer periphery of these internal conductors 4. A mold (not shown) is arranged around this embedded electrode 8, and a resin in which a main agent / curing agent / filler is mixed is poured into the mold, and the resin is subjected to predetermined temperature and time, The resin is cured to form the insulating resin unit 3. After that, the pre-mode insulator 2 is pushed into both ends of the insulating resin unit 3 to manufacture the prefabricated type connection portion.

[0007]

The electrically weak portion of the insulating resin unit 3 is the edge portion 8a of the embedded electrode 8, and the electric field strength near the edge portion 8a of the embedded electrode 8 is the largest. Become. That is, when the dielectric breakdown test is performed, the vicinity of the edge portion 8a of the embedded electrode 8 is often destroyed. For this reason, the insulating resin unit 3 in which the electric field strength near the edge portion 8a of the embedded electrode 8 is reduced and the dielectric breakdown resistance is improved has been desired. The dielectric breakdown performance has the property of being easily influenced by the surface smoothness of the embedded electrode 8.

The present invention effectively solves the above problems, and an object of the present invention is to provide an insulating resin molded article capable of improving dielectric breakdown performance.

[0009]

An insulating resin molded article of the present invention is molded on the outer periphery of an insulator such as a power cable, and is embedded in the insulating resin unit containing a filler. , An embedded electrode that applies a voltage to the insulating resin unit, and an electric field relaxation layer is formed around the embedded electrode.

[0010]

In the present invention, when a voltage is applied to the insulating resin unit by the embedded electrode, the filler in the insulating unit migrates to form the electric field relaxation layer. By forming this electric field relaxation layer, the electric field applied to the insulating resin unit is relaxed. That is, even when a high-strength electric field is applied near the edge portion of the embedded electrode of the power cable or the like, this electric field is relaxed by the electric field relaxation layer.

[0011]

EXAMPLE An example of an insulating resin molded article of the present invention will be described below with reference to FIGS. Here, as an example of using an insulating resin molded product, a prefabricated type connecting portion will be described, and the same components as those of the conventional example will be described using the same reference numerals. As shown in FIG. 1, reference numeral 10 is a prefabricated type connecting portion 10, and the prefabricated type connecting portion 10 includes a premolded insulator 2 inserted in a power cable 1 and an insulation that can be pressed into the premolded insulator 2. And a conductive resin unit 15 (insulating resin molded product).

In the power cable 1, the inner conductor 4 is projected from the end of the cable insulator 5. The premolded insulator 2 has an insulating rubber 6 that covers the periphery of the end of the cable insulator 5, and a semiconductive rubber 7 that pushes the insulating rubber 6 toward the insulating resin unit 3 side.

The insulating resin unit 15 has a cylindrical portion 16 whose both ends are pressed into the premolded insulator 2, and an electric field relaxation layer 17 formed on the inner peripheral surface of the cylindrical portion 16.
The embedded electrode 8 is embedded inside the electric field relaxation layer 17. Here, the tubular portion 16 is mainly composed of a resin such as a two-component mixed resin such as epoxy which reacts when the main agent and the curing agent are mixed. The electric field relaxation layer 17 includes the tubular portion 1
The main component is a filler such as alumina or silica dispersed in the resin of No. 6. The embedded electrode 8 is formed in a cylindrical shape around the inner conductor 4 protruding from the cable insulator 5, and is electrically connected to the inner conductor 4 of the power cable 1.

A method of manufacturing such a prefabricated type connecting portion 10 will be described. First, the premolded insulators 2 are respectively inserted into the ends of the pair of power cables 1, and the inner conductors 4 of each power cable 1 are arranged to face each other. On the other hand, the surface of the embedded electrode 8 is surface-treated to have a predetermined roughness, and the embedded electrode 8 is arranged on the outer circumference of the internal conductors 4 facing each other. And
A mold (not shown) is arranged around the embedded electrode 8, a resin containing a filler is poured into the mold, and the resin is cured at a predetermined temperature for a predetermined time to cure the resin. The unit 15 is formed. Here, when the resin is cured, a voltage is applied to the embedded electrode 8 to apply a voltage to the resin.

By applying a voltage to this resin,
The filler in the resin moves toward the embedded electrode 8 by dielectrophoresis, the filler is concentrated around the embedded electrode 8, and the electric field relaxation layer 17 is formed around the embedded electrode 8. It
Here, since the dielectric constant of the filler in the resin is larger than that of the resin layer, the edge portion 8a of the embedded electrode 8 or the uneven portion of the surface of the embedded electrode 8 which is a local high electric field portion in the resin layer. The filler moves to the periphery by dielectrophoresis, and the electric field relaxation layer 17 having a high dielectric constant is formed around the embedded electrode 8.

The moving speed of particles in a liquid due to charging is
It is expressed by the following equation. v = K · η · ε ₁ · {(ε ₂ −ε ₁ ) / (ε ₂ + 2ε ₁ )} · (dE ² / dx) where v is the moving velocity of particles and K is a proportional constant. , Η is the viscosity of the liquid, ε ₁ is the dielectric constant of the liquid, ε ₂ is the dielectric constant of the particles, x is the migration distance,
E indicates an electric field.

As described above, the moving speed of particles depends on the dielectric constant difference,
Liquid viscosity, proportional to dE ² / dx. Therefore, depending on the level of the local defect portion of the buried electrode 8, the electric field relaxation layer 1
7 is formed. Since the moving speed is proportional to dE ² / dx, the voltage to be applied may be alternating current or direct current. In this way, the electric field relaxation layer 17 is formed and the resin is cured to form the insulating resin unit 15, and then the pre-mode insulator 2 is pushed into both ends of the insulating resin unit 15 to manufacture the prefabricated type connection portion. .

According to such a method of molding the insulating resin unit 15, the insulating resin unit 15 is made by pouring a curable resin containing a filler on the outer periphery of the cable insulator 5 of the power cable 1 and curing the resin. When the resin is being formed, a voltage is applied to the resin being cured to cause the filler to migrate and form the electric field relaxation layer 17 in the cured resin. Therefore, the insulating resin unit 15 is electrically charged. It is possible to prevent the electric field generated by the electric field relaxation layer 17 from being relaxed and the insulating resin unit 15 from being destroyed. The insulating resin unit 15 thus obtained has high dielectric breakdown resistance.

Therefore, by curing and molding the insulating resin unit 15 on the edge portion of the embedded electrode 8 to which a high voltage is applied, such as the prefabricated type connection portion 10, the edge portion 8a of the embedded electrode 8 is formed. The dielectric breakdown resistance can be improved, the dielectric breakdown resistance of the prefabricated connection 10 and the like can be improved, and the 10-safety of the prefabricated connection can be improved.

On the other hand, by providing the embedded electrode 8 embedded in the insulating resin unit 15 and applying a voltage to the insulating resin unit 15, by applying a voltage to the embedded electrode 8, The electric field relaxation layer 1 is provided around the buried electrode 8.
7 can be formed. Therefore, it is possible to prevent the vicinity of the embedded electrode 8 from being destroyed by a high electric field, improve the dielectric breakdown resistance performance of the insulating resin unit 15, and improve the electrical safety in the vicinity of the embedded electrode 8. be able to.

(Experimental Example 1) As a raw material of the insulating resin unit 15, bisphenol A was used as a main component, an acid anhydride was used as a curing agent, and alumina and silica were used as fillers for each sample. The main agent and the curing agent were mixed, and 200 parts by weight of a filler was mixed with this mixed liquid. The resin containing the filler was poured into the mold 20 as shown in FIG. In this frame 20, a pair of electrodes 21, 21 made of aluminum are arranged facing each other with a space of 1 mm. As these aluminum electrodes 21, a pair of surface-treated products surface-treated with # 120 polishing paper and a pair of surface-treated products surface-treated with # 600 polishing paper were used for each sample.
When the resin was cured, the temperature was held at 125 ° C. for 12 hours, and an AC voltage and a DC voltage were applied to each sample.

Comparative Example Using the same raw material and the same test equipment as in Experimental Example 1, when the resin was cured, the aluminum electrode 21 was held at 125 ° C. for 12 hours to be cured without applying a voltage. It was After preparation of each sample in Experimental Example 1 and Comparative Example, an AC voltage was increased by 5 kV at intervals of 5 minutes, and an AC breakdown test was performed for each sample. AC by curing condition and AC destructive test for each sample
The breakdown voltage results are shown in Table 1.

[0023]

[Table 1]

As is clear from the results shown in Table 1, the resin is cured when the AC voltage is applied and when the DC voltage is applied, as compared with the case where the resin is not electrically cured.
C breakdown voltage increased. Then, as the applied voltage for curing was increased, the AC breakdown voltage was increased. On the other hand, comparing # 120 and # 600, the effect is recognized even with the one having a large surface roughness, and the effect is shown in alleviating the electric field in the rough surface of the electrode.

(Experimental Example 2) As the raw material of the insulating resin unit 15, the same material as in Experimental Example 1 was used to prepare a prefabricated type connecting portion. When curing the insulating resin unit 15, an AC voltage of 200 kV was applied to the embedded electrode 8.

Comparative Example The same raw material as in Experimental Example 2 was used for the insulating resin unit 3, and the insulating resin unit 3 was naturally cured at room temperature. The AC breakdown voltage of the prefabricated type connection in these Experimental Example 2 and Comparative Example was measured. The measurement results are shown in Table 2.

[0027]

[Table 2]

As shown in Table 2, when the resin is not charged, the edge portion of the embedded electrode is destroyed and the AC breakdown voltage is 960 kV. The parts other than the insulating resin unit were destroyed, and the AC breakdown voltage was 1200 kV. As is clear from this result, when the resin is cured by applying an electric voltage, the insulating performance of the resin is improved.

[0029]

As described above, according to the insulating resin molded product of the present invention, an insulating resin unit molded on the outer periphery of an insulator such as a power cable and containing a filler, and the insulating resin unit. The insulating unit has a buried electrode embedded in the inside and applies a voltage to the insulating resin unit, and an electric field relaxation layer is formed around the buried electrode. It is possible to prevent the electric field applied to the insulating unit from being relaxed by the electric field relaxation layer and being destroyed by the high electric field. Since the insulating resin unit has a buried electrode for applying a voltage, a voltage is applied to the buried electrode to cause the filler to migrate and an electric field relaxation layer to be formed around the buried electrode. It Therefore, even when a high electric field is applied to the buried electrode, this electric field is relaxed by the electric field relaxation layer, so that the vicinity of the buried electrode can be prevented from being destroyed by the high electric field. The electrical safety around the electrodes can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an insulating resin molded product obtained by an insulating resin molding method of the present invention.

FIG. 2 is a cross-sectional view showing an instrument used for a test of the insulating resin molding method of FIG.

FIG. 3 is a cross-sectional view showing a conventional insulating resin molded product.

[Explanation of symbols]

 1 Power Cable 8 Embedded Electrode 15 Insulating Resin Unit (Insulating Resin Molded Product) 17 Electric Field Relaxation Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Niwa 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Ltd.

Claims (1)

[Claims] 1. An insulating resin unit formed on the outer periphery of an insulator such as a power cable and containing a filler, and an embedding embedded in the insulating resin unit and applying a voltage to the insulating resin unit. An insulating resin molded article having an electrode, and an electric field relaxation layer formed around the embedded electrode.