JPS587551Y2 - High dielectric constant tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high dielectric constant tape that is particularly suitable for reducing the electric field immediately above the conductor of a paper insulated cable and improving the dielectric breakdown characteristics of the cable.

Generally, in high-voltage OF cables, a wound layer of semiconducting paper is provided on the stranded conductor, and an insulating layer consisting of a wound layer of oil-impregnated insulating paper is provided around the outer periphery.However, in ultra-high voltage cables, In this case, the electric field strength between the semiconducting layer and the insulating layer increases, and charges penetrate into the insulating layer, causing dielectric breakdown.

In order to overcome these difficulties, it is effective to use insulating paper with a high dielectric constant for the insulating layer directly above the semiconducting layer, but it is extremely difficult to adjust the permittivity of the insulating paper itself. and is not practical.

In particular, among the conventionally known insulating tapes, there is no one that has a high dielectric constant and low dielectric loss.

Specifically, the dielectric constant is 4 or more and the dielectric loss is 0.2%.
The following insulating tapes are not known.

That is, among known insulating materials, those with a large dielectric constant have a large dielectric loss, and those with a small dielectric loss have a small dielectric constant.

The present invention was developed in view of this point, and is made by blending barium titanate powder with polyolefin, which has a dielectric constant of 5 to 2.
The present invention aims to provide a high dielectric constant tape in which electrically insulating paper is adhered to one side of a film made of a composition adjusted to zero, and semiconductive paper is adhered to the other side.

To explain one embodiment shown in the drawings below, 1 is a film made of polypropylene mixed with barium titanate and has a dielectric constant of about 5 and a thickness of 60μ, and 2 and 2' are each attached to both sides of the film 1. Kraft insulating paper and semiconducting paper each having a thickness of 40 μm were integrated by heat fusion.

It is also possible to replace the above-mentioned polypropylene with other polyolefins having good oil resistance, such as high-density polyethylene or silane-blatted polyethylene.

Although the barium titanate used in the present invention has a relatively small dielectric loss, it has an extremely large dielectric constant of 600 or more, so a predetermined dielectric constant can be obtained by blending a small amount into the above polyolefin. be able to.

In the present invention, the range of the dielectric constant of the film containing barium titanate mixed with polyolefin is limited as described above because if the dielectric constant is less than 5, there is almost no electric field relaxation effect, and if it exceeds 20, there is no dielectric loss. This is because it becomes larger and generates some heat due to dielectric loss.

A tape with the above structure can be obtained by bonding a polyolefin film containing barium titanate to an insulating paper or a semiconductive paper using an adhesive. A suitable method is to press insulating paper and semiconducting paper on both sides while in the softened state.

The high dielectric constant tape of the present invention can be used, for example, in OF cables, GF cables, etc.
By winding the semiconductive paper on the inside of a conductor such as a cable or on an internal semiconductive layer, the electric field between the conductor and the insulator is relaxed.

As is clear from the above explanation, according to the present invention, barium titanate is blended to make the dielectric constant of the polyolefin film 5 to 20, and this is inserted between the insulating paper and the semiconductive paper. A tape with high electric field relaxation effect can be obtained without increasing dielectric loss.

Furthermore, since the semiconductive paper is pasted in advance, it is also possible to omit the winding of the semiconductive tape, which smooths the conductor surface and prevents electric field concentration.

Furthermore, since the film is interposed between the insulating paper and the semiconducting paper, the tape is prevented from bending due to the difference in thermal expansion coefficient between the film and the insulating paper, and it stably exerts an electric field relaxation effect.

In the above embodiments, an example in which kraft insulating paper was used as electrical insulating paper was explained, but the present invention is not limited to such an embodiment. For example, synthetic paper or various laminated insulating papers may be used. You can also use

Further, the application of the present invention is not limited to electric field relaxation of OF cables and GF cables.

[Brief explanation of the drawing]

The drawing is a sectional view of an embodiment of the present invention. 1...Film made of polypropylene mixed with barium titanate, 2...Kraft insulating paper,
2'... Semi-conductive paper.

Claims (1)

[Scope of utility model registration request] The film is made of a polyolefin compounded with barium titanate powder to have a dielectric constant of 5 to 20, and is characterized by pasting electrically insulating paper on one side and semiconducting paper on the other side. electric field mitigation tape.