JPS6329766B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to oil-impregnated electrical equipment.
In recent years, electrical equipment such as capacitors, cables, and transformers have become increasingly high-voltage and compact.As a result, synthetic resins are being used as insulating materials instead of or in combination with insulating paper. Film and other materials have come into use. As a result, the performance requirements for electrical insulating oils have become even more stringent. Conventionally, mineral oils, alkylbenzenes, polybutenes, alkylnaphthalenes, alkylbiphenyls, diarylalkanes, and the like have been proposed and used as insulating oils for oil-impregnated electrical equipment. However, the performance of these insulating oils has not been able to sufficiently respond to the development of electrical equipment as described above. This is particularly unsatisfactory for electrical equipment using synthetic resin film insulators. In other words, with the increase in voltage and miniaturization of electrical equipment mentioned above, the performance required of the insulating oil used is high dielectric breakdown voltage, low dielectric dissipation factor that causes dielectric loss, and hydrogen gas It is required to have excellent absorbency. Hydrogen gas absorption indicates the stability of an insulating oil against corona discharge under high voltage; the higher the gas absorption, the less likely corona discharge occurs and the more stable the insulating oil is. On the other hand, in response to the above-mentioned demand for higher voltage in electrical equipment, insulators or dielectrics used in electrical equipment such as oil-impregnated power cables and capacitors are being replaced with polyolefin, polystyrene, polyester, etc. Plastic films such as these have come to be used as part or all of insulators or dielectrics. dielectric strength, dielectric loss tangent,
From the viewpoint of dielectric constant, etc., polyolefin films, particularly polypropylene films and crosslinked polyethylene films, are used as plastic films. When these polyolefin films are impregnated with electrical insulating oil, they swell or dissolve to some extent depending on the type of oil. When the film swells, the thickness of the insulating layer increases, which causes phenomena such as an increase in the oil flow resistance of electrical insulating oil in cables and poor impregnation of electrical insulating oil in capacitors, resulting in voids (areas where oil is not impregnated). occurs, causing a decrease in corona discharge voltage, which is undesirable. However, although each of the electrical insulating oils described above has satisfactory dielectric breakdown voltage (BDV) and dielectric loss tangent (tan δ) to some extent, it has poor hydrogen gas absorption,
As a result, it is not possible to fully satisfy the corona discharge characteristics and the dimensional stability of the polypropylene film. The present invention solves these drawbacks of conventional oil-impregnated electrical equipment, and uses diarylalkanes and alkyl-
The present invention relates to oil-impregnated electrical equipment impregnated with an insulating oil containing a 3-phenylindane dielectric. general formula In the above formula, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms or methyl groups, and the total number of carbon atoms from R ₁ to R ₄ is 0.
is an integer from 2 to 2. Examples of electrical equipment in the present invention include capacitors, cables, transformers, and the like. As the insulator for electrical equipment, any one of insulating paper, synthetic resin film, and a combination thereof can be used. Specifically, there are capacitors that use insulating paper as the insulator (dielectric), those that use both insulating paper and polypropylene film, and those that use only polypropylene film. Also, as an insulator for cables (OF cables),
Those using insulating paper, those using insulating paper and a polyolefin such as polyethylene or polypropylene laminated, those using a composite film in which insulating paper and silane grafted polyethylene are cross-linked in the presence of a silanol catalyst, or those using insulating paper. Instead, there are those using polyolefin films such as polyethylene and polypropylene. Although the oil-impregnated electrical equipment of the present invention is intended for any of these, it is particularly preferable to use a combination of a synthetic resin film for at least a portion of the insulator (dielectric) and the insulating oil. Next, regarding the diarylalkanes used in the oil-impregnated electrical equipment of the present invention, those having a viscosity of 7 cSt or less at 40° C. alone or in a mixture thereof are preferred. Among diarylalkane, preferred compounds are diarylethanes, and more preferred are arylphenylethanes represented by the following general formula (). general formula In the above formula, R ₁ to R ₃ are a hydrogen atom or a C ₁ to _{C 3} alkyl group, and the total number of carbon atoms in R ₁ to R ₃ is 3 or less. Specific examples of diarylalkanes are as follows. 1,1-diphenylethane, 1,1-di(methylphenyl)ethane, 1-phenyl-1-(methylphenyl)ethane, 1-phenyl-1-(dimethylphenyl)ethane, 1-phenyl-1-
(ethylphenyl)ethane, 1-phenyl-1-
(Methyethylphenyl)ethane, 1-phenyl-1(isopropylphenyl)ethane, 1-phenyl-1-(trimethylphenyl)ethane. These can be easily produced by reacting styrene or alkylstyrene with alkylbenzene in the presence of a Lewis acid catalyst. Alternatively, it can also be obtained by separating it from by-product oil during ethylbenzene production. These diarylalkane may be used alone or as a mixture of two or more compounds. Alkyl-3- represented by the above general formula ()
The phenylindane dielectric is obtained by dimerizing styrene or its alkyl dielectric with an acidic catalyst such as a solid acid catalyst. Among the alkyl-3-phenylindane dielectrics, preferred compounds are those obtained by dimerizing styrene, α-methylstyrene, and vinyltoluene, particularly preferably 1-methyl-3-
It is phenylindane. Diarylalkane itself has excellent electrical properties as well as excellent biodegradability, thermal stability, and oxidation stability, but when used in combination with an alkyl-3-phenylindane dielectric, it can be used in plastic insulators such as polypropylene film. The dimensional stability of plastic insulation is significantly improved when impregnated into electrical equipment in which it is used. On the other hand, alkyl-3-phenylindane dielectrics themselves have excellent biodegradability, heat resistance, oxidation stability, and electrical properties, but generally have high pour points;
For example, even in the case of 1-methyl-3-phenylindane, the pour point is -40°C, which is not necessarily completely satisfactory when used alone, but when used in combination with diarylalkane, it can be used for plastic insulation as described above. The effect of improving the dimensional stability of the body can be obtained, and the viscosity of the electrical insulating oil can be adjusted to a preferable range. The mixing ratio of diarylalkane and alkyl-3-phenylindane dielectric is arbitrary, but the former is 1 and the latter is in the range of 0.01 to 9 (weight ratio).
Preferable from the viewpoint of synergistic effects. Since the electrical insulating oil described above has the various properties described above, it can be used in capacitors, cables, transformers, and various other electrical equipment. Electrical insulating oil for capacitors or cables that contain plastic film as an insulator, because it has a higher dielectric constant and better compatibility with polypropylene film or polyethylene film than other hydrocarbon-based insulating oils. It is most suitable as The electrical insulating oil used in the present invention consists of a mixture having the above composition, but is not limited thereto. That is, polybutene, mineral oil-based insulating oils, alkylbenzene-based insulating oils, alkylnaphthalene-based, alkylbiphenyl-based, and other aromatic Can be used with addition of insulating oil. Polybutene improves volume resistivity and dielectric loss tangent, mineral oil-based insulating oil improves breakdown voltage,
Although alkylbenzene-based insulating oils and other aromatic insulating oils improve breakdown voltage, dielectric loss tangent, pour point, etc., they tend to lower dielectric constant, so it is not preferable to add more than 50%. Also,
There is no problem in adding a small amount of oxidation stabilizer if necessary. Furthermore, compounds known as additives for electrical insulating oils, such as phosphoric acid ester compounds and epoxy compounds, can also be used in combination. The oil-impregnated electrical equipment impregnated with the electrical insulating oil described above has the following features. Since plastic insulators have excellent dimensional stability, in the case of cables, there is little dimensional change in the insulators due to swelling, so the oil flow resistance of insulating oil is small, and oil immersion can be completed in a short time. In addition, cables that use an insulator made of a laminated film of plastic film and insulating paper have a long lifespan because there is no risk of peeling, wrinkling, or buckling even if they come into contact with insulating oil for a long time. You get the cable. In the case of capacitors, since the plastic film swells little, it is sufficiently impregnated with electrical insulating oil and no voids are formed. Therefore, it is possible to obtain a capacitor that is less likely to cause corona discharge, has no risk of dielectric breakdown, and has an extremely long life. In addition, since it has excellent hydrogen gas absorption, both the cable and the capacitor have excellent corona discharge resistance under high voltage, and oil-impregnated electrical equipment with a long life can be obtained. Furthermore, by impregnating it with an insulating oil consisting of multiple components, we have achieved improvements in the above properties, while maintaining the excellent electrical properties, biodegradability, heat resistance, and oxidation stability of each component itself. At the same time, the viscosity and pour point can be adjusted within the desired range.
Oil-impregnated electrical equipment can be manufactured efficiently, and oil-impregnated electrical equipment that exhibits high performance can be obtained without restrictions due to usage conditions. EXAMPLES Below, the electrical insulating oil used in the present invention and the electrical equipment impregnated with the insulating oil will be explained in more detail with reference to Examples. Examples and Comparative Examples (1) Test of electrical properties of insulating oils The electrical properties of the various insulating oils shown in Table 1 were measured. The results are shown in Table 2. In Table 1,
Insulating oils 3 and 4 are insulating oils used in the oil-impregnated electrical equipment of the present invention;
is a comparative example. In Table 2, the pour point, flash point, and electrical performance were all measured according to the test method of JIS C 2101, and the oxidation stability test was conducted at 115°C with air heating for 96 hours. be.

【table】

[Table] (2) Compatibility test between insulating oil and polypropylene film Next, we conducted a compatibility test with polypropylene film. (b) Thickness change rate test Kraft insulating paper/polypropylene film/kraft insulating paper (thickness 43μ/49μ/43μ)
Layer 10 composite films of kraft insulating paper and polypropylene film with the following composition.
After drying at 100°C for 24 hours while applying a pressure of Kg/cm ² , it was impregnated with insulating oil at the same temperature while maintaining a constant pressure, and changes in thickness were measured. The results of this test are shown in Table 3.
(The numbers in Table 3 are the thickness change rate %)

[Table] Since the thickness change rate of each insulating oil with respect to kraft insulating paper is the same, the difference in thickness change rate shown in Table 3 indicates the difference in thickness change of each insulating oil with respect to polypropylene film. (b) Solubility test Polypropylene extruded film (thickness
49μ) was immersed in a sufficient amount of insulating oil at 100°C for 40 days, the polypropylene dissolved in the oil was precipitated with methanol, and the amount of dissolved polypropylene was determined. The results are shown in Table 4.

[Table] From the above results, it can be seen that the insulating oil used in the present invention has excellent performance and also has good compatibility with polyolefin film. (3) Oil-impregnated cable test A model cable was manufactured and its performance was tested using the method described below. (a) Preparation of polypropylene composite film Two sheets of kraft insulating paper (thickness 43 μm) were bonded together by polypropylene melt extrusion to obtain a polypropylene composite film. The thickness of the film is kraft paper (43μ)/polypropylene (49μ)/kraft paper (43μ)
It was hot. (b) Production of oil-impregnated cable Next, a model cable was produced using the above composite film. In other words, as a conductor
The above composite film in the form of a tape with a width of 20 mm is wound around a 30 mmφ copper pipe at a pressure of 0.5 kg/20 mm to form an insulating layer with a thickness of 4.5 mm, and the outside is covered with corrugated aluminum through carbon paper. The cable was coated, vacuum dried at 110°C and 10 ^-3 mmHg for 12 hours, and then impregnated with the degassed and dried insulating oil to produce a model cable. (c) Oil-impregnated cable test The above model cable was tested for initial and
The impulse breakdown strength after heating at 100°C for 30 days and the rate of change in the thickness of the insulating layer before and after heating were measured. The results are shown in Table 5 below.

[Table] (4) Oil-impregnated capacitor test Using three stacked 18μ polypropylene films as the dielectric and aluminum foil (thickness 6μ, width 80mm) as the electrode, length 9.5
A model capacitor was fabricated by winding and stacking 5 m of capacitors according to a conventional method. This capacitor was impregnated with each of the insulating oils described in item (1) above under vacuum to produce 10 oil-impregnated capacitors each having a capacitance of about 0.5 μF. A voltage 1.5 times the rated voltage was continuously applied to the capacitor thus obtained at 30°C, and the breakdown rate was determined. The results are shown in Table 6.

[Table] From the results in Tables 5 and 6, it can be seen that the cables and capacitors impregnated with the insulating oils 3 and 4 have superior electrical properties compared to those using the insulating oil of the comparative example.

Claims (1)

[Claims] 1. Oil-impregnated electrical equipment using a synthetic resin film as at least a part of the insulator or dielectric, one or more diarylalkane,
and alkyl- represented by the following general formula ()
Oil-impregnated electrical equipment characterized by being impregnated with an insulating oil containing one or more types of 3-phenylindane dielectrics, general formula: In the above formula, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms or methyl groups, and the total number of carbon atoms from R ₁ to R ₄ is 0.
is an integer from 2 to 2. 2. The oil-impregnated electrical device according to claim 1, wherein the oil-impregnated electrical device is a capacitor. 3. The oil-impregnated electrical equipment according to claim 1, wherein the oil-impregnated electrical equipment is an oil-impregnated cable. 4. The oil-impregnated electrical device according to any one of claims 1 to 3, wherein the synthetic resin film is a polypropylene film or a polyethylene film. 5. The oil-impregnated electrical equipment according to any one of claims 1 to 4, wherein the diarylalkane is arylphenylethane. 6. The oil-impregnated electrical device according to any one of claims 1 to 5, wherein the alkyl-3-phenylindane dielectric is 1-methyl-3-phenylindane. 7 The alkyl-3-phenylindane derivative is 0.01 to 9 to 1 of the diarylalkane.
The oil-impregnated electrical equipment according to claim 1, which is impregnated with insulating oil in a proportion of (weight ratio).