JPH0757534A - Molding method for insulating resin and insulating resin molding - Google Patents

Abstract

PURPOSE:To improve dielectric breakdown resistance performance. CONSTITUTION:When a hardening resin containing carbon black of 0.1-5 pts.wt. against the total weight is poured and hardened to form an insulating resin unit 15, voltage is applied to the resin being hardened, and the carbon black is migrated to form a field relaxation layer 17 in the hardened resin. Since the carbon black is migrated to form the field relaxation layer 17, the field relaxation layer 17 having a high dielectric constant can be formed, and the dielectric breakdown resistance performance of a power cable can be improved.

Description

Detailed Description of the Invention

[0001]

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

[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. Here, as an insulating resin molded product used in the field of cables, a prefabricated type connecting portion of a crosslinked polyethylene insulated PVC sheath cable (CV cable) is used. This prefabricated connection is 275-50
Among the 0 kV ultra-high voltage CV cables, it is considered as a promising alternative to the mold type connection part because of the short construction period.

As shown in FIG. 2, 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 the insulating resin unit 3 will be described. First, a mold (not shown) is arranged around the embedded electrode 8, and a resin containing a mixture of a main agent / curing agent / filler is poured into the mold, and the resin is subjected to a 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.

Further, when the epoxy resin is used for the insulating resin unit 3, the epoxy resin has a polar group as compared with the cross-linked polyethylene, so that the dielectric loss (tan δ) is large and a filler is added to the epoxy resin. This further increases tan δ. Therefore, ultra high pressure C
When an epoxy resin cast product is used for a V cable or the like, thermal destruction due to an increase in tan δ also poses a problem.

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

[0010]

A method for molding an insulating resin according to claim 1 is characterized in that carbon black is added in an amount of 0.
When a curable resin containing 1 to 5 parts by weight is poured and the resin is cured to form an insulating resin unit, a voltage is applied to the resin being cured to cause the carbon black to migrate and cure. An electric field relaxation layer is formed in the resin.

The insulating resin molded article according to claim 2 is an insulating resin unit containing 0.1 to 5 parts by weight of carbon black with respect to the total weight, and the insulating resin unit is embedded in the insulating resin unit. And an embedded electrode for applying a voltage to the resin unit. An electric field relaxation layer is formed around the buried electrode.

[0012]

In the present invention, when the insulating resin unit is molded with the embedded electrode, by applying a voltage to the resin being cured, the carbon black in the resin being cured migrates,
An electric field relaxation layer having a high dielectric constant is formed. 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 of the buried electrode, this electric field is relaxed by the electric field relaxation layer.

[0013]

EXAMPLE An example of an insulating resin molding method and an insulating resin molded product of the present invention will be described below with reference to FIGS. 1 to 3. 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 tubular portion 16 whose end is pushed into the premolded insulator 2, an electric field relaxation layer 17 formed on the inner peripheral surface of the tubular portion 16, and the electric field relaxation. And a buried electrode 8 buried inside the layer 17. Here, the tubular portion 16 is mainly composed of a resin such as a two-liquid mixing type resin which reacts by mixing the main agent and the curing agent. The electric field relaxation layer 17 contains carbon black dispersed in the resin of the tubular portion 16 and a filler such as silica or alumina as main components. 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.

Here, the surface of carbon black in the electric field relaxation layer 17 is active and adsorbs ionic impurities in the epoxy resin and the filler, so that the dielectric loss (tan δ) of the insulating resin unit 15 is reduced. Reduce. Therefore, the carbon black is added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the mixture of the two-component mixed resin and the filler. As the addition amount of this carbon black,
If it is 0.1 parts by weight or less, the dielectric loss (tan δ) will not be improved, and if it is 5 parts by weight or more, carbon black particles will start to form chains, and the dielectric loss (tan δ) will be poor. Here, as carbon black, channel black,
Thermal black, furnace black, acetylene black, etc. are used. Channel black has a low pH, a high content of volatile substances, and a small particle size. Thermal black has a coarse grain size. The furnace black made from natural gas has a particle size intermediate between channel black and thermal black, and the one made from petroleum has various particle sizes.

Next, a method of manufacturing the insulating resin unit 15 will be described. First, the surface of the embedded electrode 8 is surface-treated to have a predetermined roughness, a mold (not shown) is arranged around the buried electrode 8, and a resin containing carbon black is poured into the mold, Predetermined temperature and time for the resin,
The resin is cured to form the insulating resin unit 15. 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,
Since carbon black is conductive particles and has a large dielectric constant, carbon black in the resin moves toward the embedded electrode 8 by dielectrophoresis. Therefore, carbon black is arranged around the embedded electrode 8, and the electric field relaxation layer 17 having a high dielectric constant is formed around the embedded electrode 8. Here, since the dielectric constant of carbon black is higher than that of the resin layer, carbon black is applied to the edge portion of the embedded electrode 8 which is a local high electric field portion in the resin layer, the uneven portion of the surface of the embedded electrode 8, and the like. Move by dielectrophoresis, and an electric field relaxation layer 17 having a high dielectric constant is formed around the embedded electrode 8.
Furthermore, since carbon black adsorbs ionic impurities, it is possible to reduce the dielectric loss of the electric field relaxation layer 17.

At this time, the moving speed of the particles due to the charge in the liquid 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 the particle, K is the proportional constant, η is the viscosity of the liquid, ε ₁ is the dielectric constant of the liquid, and ε ₂ is the dielectric constant of the particle. Rate, x is the distance traveled,
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, as the dielectric constant of the particle is larger, the moving speed of the particle is higher, and d depends on the level of the local defective portion of the embedded electrode 8.
The electric field relaxation layer 17 is formed in proportion to E ² / dx. Further, 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 so that the insulating resin unit 1 can be formed.
After forming 5, the pre-mode insulator 2 is pushed into both ends of the insulating resin unit 15 to form the pre-fabricated connecting portion 1
0 is produced.

According to such a method of molding the insulating resin unit 15, a curable resin containing carbon black is poured around the cable insulator 5 of the power cable 1 and the resin is cured to form the insulating resin unit. At the time of forming, by applying a voltage to the resin being cured, the carbon black is caused to migrate so that the electric field relaxation layer 17 is formed in the cured resin.
Since carbon black adsorbs ionic impurities, the electric field relaxation layer 17 with a small dielectric loss can be formed, and the electric field relaxation layer 17 with a high dielectric constant can be formed. Therefore, it is possible to prevent the electric field applied to the insulating resin unit 15 from being relaxed by the electric field relaxation layer 17 and destroying the insulating resin unit 15. The insulating resin unit 15 thus obtained has high dielectric breakdown resistance.

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

Further, with respect to the surface roughness of the embedded electrode 8, the electric field relaxation layer 17 having a uniform thickness can be formed around the periphery. Therefore, it is possible to prevent the insulating resin unit 15 from being destroyed by a high electric field, further improve the dielectric breakdown resistance performance of the insulating resin unit 15, and further improve the safety of the prefabricated type connection portion 10. be able to.

On the other hand, by providing the embedded electrode 8 embedded in the insulating resin unit 15, by applying a voltage to the embedded electrode 8, carbon black can be migrated in the resin being cured. The electric field relaxation layer 17 having a high dielectric constant can be formed around the embedded electrode 8. 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 Examples 1 to 4) Insulating resin unit 15
As a raw material, bisphenol A was used as the main component, an acid anhydride was used as the curing agent, and 2 parts by weight of the filler was mixed with the mixture of the main component and the curing agent. As this filler 2,
Alumina was used (Experimental Examples 1 to 3) or silica was used (Experimental Example 4). Furnace black was added to the mixture of the main agent, the curing agent and the filler, and the mixture containing these furnace blacks was maintained at 125 ° C. for 12 hours to give a thickness of 1
mm plate-shaped samples were molded. For each of these samples, the amount of furnace black added (CB parts by weight) was changed under the conditions of 50 Hz and 1 kV (Experimental Examples 1 to 1).
3), the dielectric loss (tan δ) was measured.

(Comparative Examples 1 to 4) As a comparative example, each resin was mixed with a resin to which furnace black was not added and cured under the same conditions as in Experimental Examples 1 to 4 to mold each sample (comparative). Examples 1, 4). Further, using alumina as a filler, 0.05 parts by weight of furnace black,
Using 7 parts by weight of the resin added, the resin was cured under the same conditions as in Experimental Examples 1 to 4, and each sample was molded (Comparative Example 2,
3). The dielectric loss of these Comparative Examples 1 to 4 was calculated as Experimental Examples 1 to 4.
It measured similarly to. These Experimental Examples 1 to 4 and Comparative Examples 1 to 4
The measurement results are shown in Table 1.

[0027]

[Table 1]

In Experimental Examples 2 and 4 shown in Table 1, when 0.5 parts by weight of the furnace black was added, the dielectric loss in each case was smaller than that when the furnace black shown in Comparative Examples 1 and 4 was not added. . Here, it is understood that the dielectric loss becomes small when 0.5 parts by weight of furnace black is added. Further, as shown in Experimental Examples 1 to 3, when the amount of furnace black added was 0.1 to 5 parts by weight, the dielectric loss was significantly smaller than that in Comparative Examples 2 and 3.

(Experimental Example 5) As Experimental Example 5, the same resin composition and mixture as the sample of Experimental Example 2 were used, and the embedded electrode 8 was used.
The resin was cured while an alternating voltage of 200 kV was applied to the insulating resin unit 15. The prefabricated type connection part 10 was manufactured using this insulating resin unit 15.

Comparative Example 5 As Comparative Example 5, Comparative Example 2
Using the same resin composition and mixture as in the sample, the resin was naturally cured without being applied with a voltage when the resin was cured to obtain an insulating resin unit. A prefabricated type connection part was manufactured using this insulating resin unit. After manufacturing the prefabricated type connection parts in Experimental Example 5 and Comparative Example 5, an AC breakdown test was performed by increasing the AC voltage by 5 kV at intervals of 5 minutes. Table 2 shows the AC breakdown voltage results of this AC breakdown test.

[0031]

[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 1300 kV. As is clear from this result, when the resin containing furnace black is electrically cured, the AC breakdown voltage increases,
It can be seen that the insulation performance of the resin is improved.

[0033]

As described above, according to the insulating resin molding method and the insulating resin molded product of the present invention, the following effects can be obtained. According to the method of the present invention, when a curable resin containing 0.1 to 5 parts by weight of carbon black is poured into the insulating resin unit to cure the resin to form an insulating resin unit, By applying a voltage to the resin, the carbon black migrates to form the electric field relaxation layer in the cured resin, so that the electric field relaxation layer having a high dielectric constant can be formed. Therefore, it is possible to prevent the electric field applied to the insulating resin unit from being relaxed by the electric field relaxation layer and prevent the insulating resin unit from being destroyed by the high electric field. Therefore, by forming an electric field relaxation layer with a high dielectric constant in the vicinity of a portion where a high voltage is applied, such as a power cable, it is possible to prevent the power cable, etc. from being destroyed by a high electric field and improve the dielectric breakdown resistance performance. Can be made.

On the other hand, according to the insulating resin molded product, since the insulating resin unit has an embedded electrode which is embedded in the insulating resin unit and applies a voltage to the insulating resin unit, a voltage is applied to the embedded electrode. By doing so, the carbon black is caused to migrate and an electric field relaxation layer having a high dielectric constant is formed around the buried electrode. Therefore, even when a high electric field is applied to the buried electrode, this electric field is relaxed by the electric field relaxation layer,
It is possible to prevent the vicinity of the embedded electrode from being destroyed by a high electric field and improve the electrical safety in the vicinity of the embedded electrode.

[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 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

Claims (2)

[Claims] 1. Carbon black in an amount of 0.
When a curable resin containing 1 to 5 parts by weight is poured and the resin is cured to form an insulating resin unit, a voltage is applied to the resin being cured to cause the carbon black to migrate and cure. An insulating resin molding method, characterized in that an electric field relaxation layer is formed in the resin. 2. Carbon black in an amount of 0.
1 to 5 parts by weight of an insulating resin unit, and an embedded electrode that is embedded in the insulating resin unit and applies a voltage to the insulating resin unit. Around the embedded electrode, An insulating resin molded product having an electric field relaxation layer formed thereon.