JP3453150B2 - Oil impregnated cable and impregnated oil - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to an oil impregnated power cable,
In particular, the present invention relates to a power cable suitable for a submarine cable and impregnated oil suitable for impregnating the power cable.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for increasing the voltage applied to oil-impregnated power cables. Therefore, various improvements have been made to the structure of the power cable, particularly with respect to its insulating layer. First, instead of conventional insulating paper, a higher dielectric strength plastic film was used for the cable insulation layer. However, when the plastic film is impregnated with oil, the plastic film swells and the oil flow resistance increases. Therefore, it was proposed to use a composite film composed of a plastic film and insulating paper for the insulating layer, but with conventional insulating oils such as alkylbenzene and polybutene, oil-impregnated composite films with such a structure as an insulating layer were proposed. Not enough for the cable.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have proposed an oil-impregnated power cable, particularly a submarine cable, having an insulating layer formed by winding a composite film containing at least an insulating paper layer and a polyolefin layer on a conductor. As a result of searching for useful impregnating oil, the present invention has been completed.

[0004]

That is, according to the present invention, an insulating layer formed by winding a composite film containing at least an insulating paper layer and a polyolefin layer on a conductor is coated with benzyltoluene and 1,1-diphenylethane. The present invention relates to an oil-impregnated electric power cable characterized by being impregnated with impregnated oil composed of a mixture. More specifically, the present invention relates to a composite film having a three-layer structure of at least insulating paper / polypropylene / insulating paper or insulating paper / polypropylene / polyolefin, or at least insulating paper /
A composite cable including a two-layer structure of a silane-grafted polyolefin is wound around a conductor to form an insulating layer, and a power cable is impregnated with insulating oil. Specifically, as the impregnating oil, 1,1-diphenylethane 10 to 90% by weight and benzyltoluene 90 to 10% by weight, relating to impregnating oil for various electric devices including power cables Is.

A composite film having at least a three-layer structure of insulating paper / polypropylene / insulating paper or insulating paper / polypropylene / polyolefin is, for example, an insulating paper or an insulating oil and a polyolefin film are bonded and integrated by melt extrusion of polypropylene. It can be manufactured by Further, a composite film containing at least a two-layer structure of insulating paper / silane-grafted polyolefin can be produced by laminating and melting an insulating paper and a silane-grafted polyolefin film and crosslinking them in the presence of a silanol condensation catalyst. it can.

The impregnating oil of the present invention is an impregnating oil consisting of a mixture of benzyltoluene and 1,1-diphenylethane. That is, 1,1-diphenylethane 10-9
An impregnating oil consisting of 0% by weight and 90 to 10% by weight of benzyltoluene. Further, an impregnating oil composed of 20 to 70% by weight of 1,1-diphenylethane and 80 to 30% by weight of benzyltoluene is preferable. Benzyltoluene may be various regioisomers of o-, m- or p-form, but benzyltoluene in which the amount of m-form in benzyltoluene is 30 to 80% by weight is preferred for the purpose of the present invention. It is a thing. Benzyltoluene or 1,1-
Diphenylethane alone has a high freezing point and is not suitable for use in cold regions. When the amount of 1,1-diphenylethane is small, the specific gravity of the impregnating oil is small, while when the amount of benzyltoluene is small, the viscosity is not high, either of which is not preferable. That is, when the specific gravity is high, there is an advantage that when it is used in water, for example, in the sea, it is difficult to float and thus it is easy to handle. The specific gravity of the cable itself is an important factor when using underwater electrical equipment such as electric power cables that use a material having a relatively low specific gravity such as polyolefin. Further, for example, in a power cable, an insulating layer made of insulating paper wound around a conductor serves as an oil passage, and impregnated oil needs to flow due to thermal expansion or contraction. Therefore, it is also important that the impregnated oil has a low viscosity and a low resistance in the oil passage.
From this viewpoint, the impregnated oil of the present invention is selected. The impregnated oil of the present invention may be mixed with other known insulating oils or additives within the scope of the object of the present invention.

This impregnated oil has high insulation resistance and dielectric strength of the oil itself, and also has excellent hydrogen absorption, so that the impregnating property and impregnating property with respect to a polyolefin film such as polypropylene are excellent. It has characteristics such as low swelling property with respect to these films. Furthermore, this impregnated oil has a particularly low viscosity and a large specific gravity among the bicyclic aromatic compounds having such characteristics, and is therefore particularly suitable for a cable used in water. Furthermore, the insulating layer of the oil-impregnated power cable of the present invention is composed of the composite film having the above-mentioned specific structure, but the composite dielectric constant of this composite film is relatively close to that of the impregnated oil. Therefore, the withstand voltage of the oil-impregnated cable of the present invention, particularly the impulse breakdown voltage, is extremely excellent.

One of the composite films of the present invention is a film having a structure in which insulating papers or an insulating paper and a polyolefin film such as a biaxially oriented polypropylene film are bonded and integrated by melt extrusion of polypropylene. This composite film can be produced by, for example, applying polypropylene by extrusion from a T-die onto insulating paper, and further fixing the insulating paper or biaxially oriented polypropylene by pressure bonding before being solidified by cooling.
This composite film has a low swelling property with respect to the oil to be impregnated in the present invention, and therefore, the oil-impregnated electric power cable of the present invention has a small oil flow resistance in combination with the low viscosity of the oil itself, It will be preferable. Furthermore, the composite film of the present invention may be a composite film composed of an insulating paper and a silane-crosslinked polyolefin film. For example, the insulating paper and the silane-grafted polyolefin are laminated and fusion-bonded and crosslinked in the presence of a silanol condensation catalyst. It is a composite film. In addition, when the plastic film is a polyolefin film, the composite film of the present invention preferably has a thickness of 40 to 120 μ, and an insulating paper thickness of about 10 to 60 μ, and a composite film of about 100 to 250 μ is suitable. There is. The present invention will be further described below with reference to examples.

[0009]

【Example】

(Production of impregnated oil) 2 mol of toluene, 1 diphenylmethane
A mixture of mole ratios is used as a hydrogen-type synthetic zeolite Z.
Using SM-5 catalyst, reaction temperature 280 ° C., reaction pressure 2
The reaction was carried out under the conditions of 5 atm and LHSV 1.0. Benzyltoluene was recovered from this reaction solution by distillation under reduced pressure. Its isomer distribution is o-form: 8%, m-form: 54%, p-
Body: 38%. This benzyltoluene, 1,1
-Dichloroethane, benzene, and 1,1-diphenylethane synthesized using an aluminum chloride catalyst were mixed at a weight ratio of 6 to 4 to obtain an impregnated oil. This impregnated oil is referred to as impregnated oil 1. The properties of the impregnated oil 1 are known mineral oil-based insulating oil (MO), alkylbenzene-based impregnated oil (AB), and alkylnaphthalene-based impregnated oil (AN) used as comparative examples.
Table 1 also shows the properties of the polybutene-based impregnated oil (PB).

[0010]

[Table 1]

(Production of Composite Film ) Composite Film 1 Two pieces of kraft paper (thickness 43 μm) were bonded and integrated by melt extrusion of propylene to obtain a composite film 1. The thickness of this film was kraft paper (43μ) / polypropylene (49μ) / kraft paper (43μ). Composite film 2 To 100 parts by weight of high-density polyethylene, 0.15 parts by weight of dicumyl peroxide (DCP) and 2.0 parts by weight of vinyltrimethoxysilane (VTMOS) were added, and the mixture was heated and kneaded at about 200 ° C. with an extruder to produce silane. Grafted polyethylene pellets were obtained. Next, add 0.05 parts by weight of dibutyltin laurate to 100 parts by weight of the pellets,
It was extruded from an extruder through a T-die between two sheets of insulating paper and pressure-bonded before being cooled and solidified. At this time, the silane may be further cross-linked by steam treatment or the like, but this is not usually necessary, and the cross-linking is promoted by desorbed water during heating for drying the composite film. The thickness composition of this film is kraft paper (43μ) / polyethylene (49μ) / kraft paper (4μ)
3 μ).

(Manufacture of Cable) A model cable was prepared using the composite films 1 and 2 and the impregnating oil. That is, a copper pipe with a diameter of 30 mm as a conductor has a width of 20 mm.
Tape and the above composite films 1 and 2 respectively.
It is wound with 5 kg / tape width to form an insulating layer with a thickness of 4.5 mm, which is vacuum dried at 110 ° C and 10 ^-3 mmHg for 12 hours, and then impregnated with degassed and impregnated oil to form a model cable. It was made. One of the two samples was left as it was, and the other one was heated at 100 ° C. for 30 days and then subjected to an impulse breakdown test. The results are shown in Table 2.

[0013]

[Table 2]

[0014]

The impregnated oil of the present invention has a low freezing point, is suitable for low temperature use, and has a low viscosity and a high specific gravity.
Difficult to float when used in water such as seawater. Therefore,
It becomes easy to use as an electric device impregnated with the impregnated oil of the present invention, for example, as a power cable for seabed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification symbol FI C10N 40:16 C10N 40:16 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 3/22 H01B 9/06 H01B 7/14

Claims (2)

(57) [Claims] 1. A benzyltoluene 90 to 10% by weight and 1, to an insulating layer formed by winding a composite film containing at least an insulating paper layer and a polyolefin layer on a conductor.
An oil-impregnated power cable for a seabed , characterized by being impregnated with an impregnating oil comprising a mixture of 10-90% by weight of 1-diphenylethane. 2. A composite film having at least a three-layer structure of insulating paper / polypropylene / insulating paper or insulating paper / polypropylene / polyolefin, or at least a two-layer structure of insulating paper / silane-grafted polyolefin. Claim that is a composite film having
Item 1. A submarine oil-impregnated power cable according to Item 1 .