JP2000276954A - Oil-impregnated solid power cable and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil-impregnated solid power cable and its manufacturing method, less liable to form a void directly on its conductor or directly beneath its metallic sheath due to a change in temperature. SOLUTION: This oil-impregnated solid power cable equipped with a conductor 1, an insulating layer 3 impregnated with an insulating oil, and a metallic sheath (lead shield layer 6), is further provided with a reinforcing layer 5 made of a material having a Young's modulus higher than that of the lead shield layer 6 between the insulating layer 3 and the lead shield layer 6. If the insulating oil is heated to a high temperature and thermally expanded, because the Young's modulus of the reinforcing layer 5 is higher than that of the lead shield layer 6, expansion of the lead shield layer 6 can be inhibited. Thus, the volume of the lead shield layer 6 is hardly increased, and a void can be inhibited from being produced when the temperature falls.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid power cable suitable for long-distance large-capacity transportation and a method for manufacturing the same. In particular, the present invention relates to a solid power cable optimal for DC submarine power transmission and a method for manufacturing the same.

[0002]

2. Description of the Related Art For a DC submarine cable, an insulating paper is wound on a conductor, and a high-viscosity insulating oil (for example, at 60 ° C.)
Insulating oil with a viscosity of about 1200 cSt
5 ")) with a solid cable (M
Ass-Impregnated Cable) is used.

[0003] Such a cable is manufactured by winding insulating paper on a conductor to a required thickness, winding it around an oil immersion tank, drying by heating under vacuum, impregnating with solid oil, and providing a metal sheath. Have been done.

[0004] Unlike the OF cable, the solid DC cable does not supply insulating oil from both ends of the cable,
For example, a sudden temperature change at the time of load rejection or the like causes voids due to contraction of the insulating oil, and when the voids become harmful, they tend to become discharge starting points.

[0005] Such voids are likely to occur first in the oil gap that is inevitably generated when spirally winding the insulating paper, and then in the gaps between the natural fibers in the insulating tape. This is likely to occur just above the conductor and directly below the metal shielding layer, and this portion is dangerous because the electric field is high.

[0006] The conventional solid DC cable has a relatively small operating voltage of, for example, 400 kV or less and a transmission current of less than 1000 A, and therefore has no particular problem with respect to voids.

[0007]

However, in recent years, plans for transmitting a large current over a long distance by using a solid DC cable have appeared one after another. For example, the transmission voltage is 450k
Lines with transmission currents exceeding V and transmission currents exceeding 1000A have been planned.

[0008] When the voltage and the current are increased as described above, the formation of harmful voids in the insulating layer immediately above the conductor cannot be ignored.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an oil-immersed solid power cable in which a void is hardly formed just above a conductor or directly below a metal sheath due to a temperature change, and a method of manufacturing the same.

[0010]

According to the present invention, the above object is achieved by providing a reinforcing layer having a high Young's modulus on the outer periphery of an oil immersion insulating layer to suppress the expansion of the insulating layer.

That is, an oil-immersed solid power cable according to the present invention is an oil-immersed solid power cable comprising a conductor, an insulating layer impregnated with insulating oil, and a metal sheath, wherein a metal sheath is provided between the insulating layer and the metal sheath. It is characterized by comprising a reinforcing layer made of a material having a higher Young's modulus than the material.

Here, the material constituting the reinforcing layer desirably has a Young's modulus of 3 × 10 ¹⁰ Pa or more. If the Young's modulus is low, the deformation of the insulating layer during the impregnation with the insulating oil cannot be suppressed, which is not preferable.

As the constituent material of the reinforcing layer, stainless tape, aramid fiber tape and the like can be mentioned. In particular, stainless steel tape is preferable because it can be easily reduced in thickness. The reinforcing layer is formed by winding these tapes on the insulating layer.

It is also preferable that the reinforcing layer is formed by winding a perforated metal tape or by opening a metal tape. If the reinforcing layer is wrapped around using metal tape, the entire outer periphery of the insulating layer will be covered with the metal tape,
Impregnation with insulating oil is difficult. Therefore, if a perforated metal tape is used or an open winding is used in which the outer peripheral surface of the insulating layer is exposed with an interval between adjacent turns, the insulating oil can be impregnated in a short time.

It is preferable to use an insulating tape containing a polyolefin resin film at least partially for the insulating layer. Examples of the polyolefin-based resin film include polyethylene, polypropylene, ethylene-propylene copolymer, and polybutene. Polypropylene is preferable because it has excellent electrical properties and has a high melting point and can be used at high temperatures. In particular, a composite tape in which kraft paper is laminated on both sides of a polypropylene film is used as the insulating tape, and the ratio of the thickness of the polypropylene film to the total thickness of the composite tape (polypropylene ratio) is 40% or more and less than 90%. It is preferable that If it is less than 40%, the proportion of kraft paper increases, and voids tend to occur in the kraft paper layer. Also, when it is over 90%,
During cable manufacture, the impregnation of the insulating oil is performed through the kraft paper layer, and the impregnation is time consuming and impractical.

It is preferable that the thickness of the insulating tape is thinner because the thickness of the oil gap is smaller. However, it is difficult to manufacture a thinner tape from the viewpoint of manufacturing, and a thickness of 50 to 200 μm is practical.

If the polypropylene laminated paper layer used for the insulating layer is subjected to ρ-grading by combining polypropylene laminated papers having different polypropylene ratios as necessary, the DC stress distribution becomes mild and effective.

Note that the DC stress distribution of the insulating layer is
Determined by the insulation resistance of The insulation resistance of the insulating oil is 1 × 10
¹⁵~ 1 × 10¹⁶Ωcm, insulation resistance of kraft paper is 4 × 10¹⁶~
1 × 10 ¹⁷Ωcm, polypropylene insulation resistance is 1 × 10¹⁷
~ 1 × 10¹⁸Ωcm
The insulation oil has low insulation resistance
The discharge is low and does not trigger the start of discharge.

With the above configuration, expansion of the oil immersion insulating layer is suppressed, and generation of voids is suppressed. The voids are caused by the contraction of the insulating oil due to a rapid temperature change, for example, when the load is cut off, and when the voids become harmful, they tend to be the starting point of the discharge. At a high temperature, the insulating oil thermally expands, so that the pressure causes the lead shielding layer (metal sheath) to expand and the inner volume to increase. If the load is cut off in that state, the temperature on the conductor side drops and the insulating oil shrinks, but since the viscosity of the insulating oil is high, it takes time for the oil outside to return to the conductor side, so voids are generated It is considered something.

Therefore, by wrapping the reinforcing tape between the outside of the insulating layer (external semiconductive layer) and the lead shielding layer, even if the temperature of the insulating oil becomes high and the insulating oil thermally expands, the reinforcing tape is made of lead. Since the Young's modulus is large, expansion of the lead shielding layer can be suppressed. Thereby, the internal volume in the lead shielding layer hardly increases, and the generation of voids can be suppressed even when the temperature decreases. In addition, since the expansion and contraction of lead is suppressed, the fatigue rupture life of lead due to a thermal heat cycle can be extended.

Furthermore, in order to suppress the generation of voids, it is preferable to reduce the amount of impregnating oil. By bonding kraft paper to a plastic film as insulating paper, voids are not generated because there is no gap in the plastic film. . Further, the ratio of the kraft paper layer in which voids are generated can be reduced.

Conventionally, impregnation of solid oil has
A semiconductive layer, an insulating layer, and an external semiconductive layer.
It is done after coiling the oil tank and drying by vacuum heating.
You. At that time, since solid oil has high viscosity,
It takes time to diffuse into the layer. Also introduced solid oil
After that, in order to fully impregnate the solid oil, 1-3 kg / cm
^TwoPressurize the tank to the extent that the solid oil
Due to its viscoelastic properties, it is difficult to apply pressure uniformly
No. As a result, the insulation layer may be eccentric,
Insulation layer may loosen in some parts, causing voids in those parts
There was something easy to do.

In the method for manufacturing a cable according to the present invention, a reinforcing layer having a high Young's modulus is provided outside the insulating layer (external semiconductive layer) and then impregnated with solid oil, whereby the insulating layer is held down by the reinforcing layer. Can be processed sufficiently densely so that the insulation layer of the entire length of the cable is loosened. That is, the reinforcing layer may be formed after the insulating layer is impregnated with the insulating oil, but it is more preferable to impregnate the insulating oil after forming the reinforcing layer. Then, according to this manufacturing method, the insulating layer can be made dense without loosening, so that generation of voids can be suppressed.

[0024]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing an example of the oil-immersed solid power cable of the present invention. This cable is a conductor
1. Includes an inner semiconductive layer 2 made of carbon paper, an insulating layer 3, an outer semiconductive layer 4 made of carbon paper, a reinforcing layer 5, a lead shielding layer (metal sheath) 6, and a cable sheath (usually made of polyethylene) 7. I have.

An example cable having such a configuration and a comparative example cable having no reinforcing layer were prepared, and electricity was supplied to the conductor to examine whether or not insulation breakdown occurred due to a heat cycle.

[0026] (Example 1) 1100 mm (Carbon Paper six thickness 100 [mu] m) inner semiconducting layer 2 to conductor 1 of ^2, the insulating layer 3 (thickness 1
100 μm kraft paper 100), external semiconductive layer 4 (thickness 100μ)
m 6 pieces of carbon paper). Then, impregnated with insulating oil (Dasek T2015 (kinematic viscosity: 1200 cSt at 60 ° C)), and a stainless steel (SUS) tape without holes (100 μm
The two layers (thickness) were rolled open to form a reinforcing layer 5 and coated with lead (Young's modulus 1.6 × 10 ¹⁰ Pa) and polyethylene to prepare a cable. Stainless steel tape has a Young's modulus of 20 × 10
¹⁰ Pa. The total time from the introduction of the insulating oil into the tank to the completion of the impregnation is 30 days.

(Example 2) An oil-immersed solid cable having the same cross-sectional structure as in Example 1 was produced. The first difference from Example 1 is that a composite tape in which kraft paper is bonded to both surfaces of polypropylene is used as the material of the insulating layer 3. The composite tape used had a thickness of 100 μm, a number of 100, and a polypropylene ratio of 60%. The second difference is that the stainless steel tape used for the reinforcing layer was a perforated stainless steel tape (one sheet of 100 μm thickness), and the stainless tape was wound on the outer semiconductive layer and then impregnated with insulating oil. is there. The stainless tape was formed with a large number of φ3 mm holes dispersed in the tape. The total time from the introduction of the insulating oil into the tank to the completion of the impregnation was 30 days.

[0028] (Comparative Example) (carbon paper six thickness 100 [mu] m) inner semiconducting layer 2 to the conductor 1 of 1100 mm ^2, an insulating layer 3 (thickness 100
100 μm kraft paper), external semiconductive layer 4 (100 μm thickness)
(6 sheets of carbon paper). Thereafter, the cable was impregnated with an insulating oil (Dessek: T2015), and coated with lead and polyethylene to prepare a cable. The difference from Example 1 is the presence or absence of a stainless steel tape.

As a result of applying a DC voltage of 1000 V to these cables while applying a heat cycle from room temperature (16 hours) to 60 ° C. (8 hours) by energizing the conductors, Examples 1 and 2 performed 30 heat cycles. While no dielectric breakdown occurred even when given, in the comparative example, dielectric breakdown occurred during the cooling process after the 20th cycle of shutting off the energization.

[0030]

As described above, according to the oil immersion solid power cable of the present invention, by providing the reinforcing layer, the expansion of the oil immersion insulating layer accompanying the heat cycle at the time of energization is suppressed.
Generation of voids can be suppressed.

Further, according to the method for manufacturing an oil-immersed solid power cable of the present invention, by providing the reinforcing layer and then impregnating the insulating oil, loosening and eccentricity of the insulating layer during impregnation can be suppressed, and voids can be generated. You can get fewer cables. In particular, the impregnation time can be reduced by using a perforated tape or an open wound tape as the reinforcing layer tape.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one example of an oil-immersed solid power cable of the present invention.

[Explanation of symbols]

 1 conductor 2 inner semiconductive layer 3 oil immersion insulating layer 4 outer semiconductive layer 5 reinforcing layer 6 metal shielding layer 7 cable sheath

Continued on the front page (72) Hiroshi Hirota, 1-3-1, Shimaya, Konohana-ku, Osaka-shi Sumitomo Electric Industries, Ltd. Osaka Works (72) Inventor Hiroshi Takigawa 1-3-1, Shimaya, Konohana-ku, Osaka-Sumitomo (72) Inventor Jun Yoda 1-3-1 Shimaya, Konohana-ku, Osaka-shi F-term (reference) 5G327 DA07 DC01 in Osaka Works, Sumitomo Electric Industries, Ltd.

Claims (9)

[Claims] 1. An oil-immersed solid power cable comprising a conductor, an insulating layer impregnated with insulating oil, and a metal sheath, wherein a material having a Young's modulus higher than that of the metal sheath material is interposed between the insulating layer and the metal sheath. An oil-immersed solid power cable comprising a reinforcing layer. 2. The material constituting the reinforcing layer has a Young's modulus of 3 × 1.
The method for producing an oil-immersed solid power cable according to claim 1, wherein the pressure is not less than 0 ¹⁰ Pa. 3. The oil immersion solid power cable according to claim 1, wherein the reinforcing layer is formed by winding a stainless steel tape. 4. The oil-immersed solid power cable according to claim 1, wherein the reinforcing layer is formed by winding an aramid fiber tape. 5. The oil-immersed solid power cable according to claim 1, wherein the reinforcing layer is formed by winding a perforated metal tape. 6. The oil-immersed solid power cable according to claim 1, wherein the reinforcing layer is formed by open winding of a metal tape. 7. The oil-immersed solid power cable according to claim 1, wherein an insulating tape containing a polyolefin-based resin film is used for at least a part of the insulating layer. 8. A composite tape in which kraft paper is laminated on both sides of a polypropylene film is used as the insulating tape, and the ratio of the thickness of the polypropylene film to the total thickness of the composite tape is 40% or more and less than 90%. The oil immersion solid power cable according to claim 7, wherein 9. A method for manufacturing an oil-immersed solid power cable in which an oil-immersed insulating layer and a metal sheath are formed on the outer periphery of a conductor, wherein a step of forming an insulating layer on the outer periphery of the conductor is performed by using a metal sheath material outside the insulating layer. Forming a reinforcing layer made of a material having a high Young's modulus, impregnating the insulating layer with insulating oil after forming the reinforcing layer, and forming a metal sheath on the reinforcing layer. A method for producing an oil-immersed solid power cable.