JP2014063876A - Oil-filled electric apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil-filled electric apparatus using a vegetable oil, capable of reducing the environmental load, as an insulation oil.SOLUTION: Out of vegetable oils, a vegetable oil containing a lot of natural antioxidant is used as an insulation oil. For example, rice oil containing a lot of tocotrienol or orizanol is preferable. Since oxidation stability of insulation oil can be ensured by the natural antioxidant contained in vegetable oil, it is not required to add an antioxidant having uncertain impact on the environment to the insulation oil. Even a vegetable oil not containing a lot of natural antioxidant enhances oxidation stability without having adverse effect on the environment, when adding an antioxidant that has been approved to be used in foods. The oil-filled electric apparatus has high possibility to be utilized in a transformer or a cable, a circuit breaker, or a capacitor.

Description

  The present invention relates to an oil-filled electrical device using vegetable oil as an insulating oil that reduces environmental burden.

  2. Description of the Related Art Conventionally, insulating oil has been used in electric devices such as transformers, circuit breakers, and capacitors for the purpose of insulation and cooling. As the insulating oil, mineral oil obtained by refining crude oil, synthetic insulating oil, or a mixed oil of mineral oil and synthetic oil has been used for many years. However, since these insulating oils are not easily decomposed in natural ecosystems, they are not preferable for use from the viewpoint of reducing the environmental load.

  Therefore, in recent years, it has been proposed to use a vegetable insulating oil excellent in biodegradability that is easily decomposed in natural ecosystems (see Patent Documents 1 and 2 below).

JP-A-11-306864 Patent No. 3145301

  The insulating oils described in Patent Documents 1 and 2 provide a vegetable oil whose electrical properties are not deteriorated as compared with mineral oil or synthetic oil when corn oil or safflower oil or rapeseed oil is used as insulating oil. Is.

  According to this invention, since there is no use of mineral oil or synthetic oil with poor biodegradability, the environmental load can be reliably reduced, and it can be replaced with mineral oil having a low flash point. There is an advantage that safety at the time of doing can be secured.

  However, unless the electrical equipment (transformer, etc.) that uses the insulating oil is completely sealed and covered with an inert gas, the insulating oil is exposed to the air, causing oxidation and degradation. And produce sludge. The generated acid corrodes metal parts such as transformers, and oxidation products adhering to the surfaces of the core and coil and the cooling tube reduce the cooling effect of the oil. It is usual to add an antioxidant. And when using the vegetable oil of the said patent documents 1, 2, it describes that the antioxidant is added in order to improve oxidation stability.

  Here, as the antioxidant, in the case of phenol type, for example, 2,6-di-tert-p-cresol; monophenol type such as 2,6-di-tert-butyl-4-ethylphenol, 4,4 Examples include diphenols such as' -methylenebis (2,6-di-tert-butylphenol); 2,2'-methylenebis (4-ethyl-6-tert-butylphenol).

  Here, as described above, vegetable oil is highly biodegradable and can reduce the impact on the environment, but the effect of antioxidants as an additive on the environment is uncertain. There is a concern that it may not be possible to reduce the environmental load, which is one of the purposes of using the device.

  Therefore, the present invention provides an oil-filled electrical device that uses vegetable oil as an insulating oil that does not require the use of an additive that has uncertain effects on the environment.

  The invention according to claim 1 is characterized in that a vegetable oil containing a natural antioxidant is used as an insulating oil.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, rice oil is used as the vegetable oil.

  The invention according to claim 3 is characterized in that among the antioxidants approved for use in foods, vegetable oil to which naturally derived ones are added is used as insulating oil.

  According to the first aspect of the invention, since the oxidation stability of the insulating oil can be ensured by the natural antioxidant contained in the vegetable oil, an antioxidant that is uncertain about the influence on the environment is added to the insulating oil. There is no need.

  According to invention of Claim 2, since the rice oil which contains many natural antioxidants is used as insulating oil, an antioxidant effect can be improved.

  According to invention of Claim 3, even if it is vegetable oil which does not contain many natural oxidizing agents, by adding the antioxidant permitted use to food, without having a bad influence on an environment, Oxidation stability can be improved.

It is a flowchart which shows the influence which the oxidation phenomenon of insulating oil has on oil-filled electrical equipment. It is a figure which shows the characteristic of rice oil and mineral oil.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, using FIG. 1, taking a transformer, which is one of oil-filled electrical devices, as an example, a process until oxidation of insulating oil causes insulation failure will be described.

  When the transformer is operated, oil and air inside the transformer expands and contracts due to changes in the temperature of the outside air and the amount of heat generated due to load fluctuations, creating a difference between the internal pressure and the atmospheric pressure, and the air enters and exits (Respiratory effect).

  As a result, when air enters the transformer and comes into contact with the insulating oil, oxygen or moisture in the air is mixed into the insulating oil and the insulating oil is oxidized. In addition, when the temperature of the insulating oil rises due to the operation of the transformer, oxidation is further promoted, and acid and sludge (a mudous substance formed by combining with metal and coil insulator) are generated.

  Acids corrode the transformer metal, and oxidation products deposited on surfaces such as the core and coil surfaces and cooling tubes reduce the cooling effect of the oil. When the cooling effect is reduced, naturally, the temperature rise is promoted, so that the thermal deterioration of the insulator is accelerated. As a result, partial discharge occurs due to overvoltage, leading to destruction of insulation.

  In order to prevent such adverse effects due to oxidation, measures have been taken to improve oxidation stability by adding antioxidants to vegetable oils substituted for mineral oils as described in the prior art. However, in view of the unclear effect of antioxidants on the environment, in the present invention, vegetable oil used as insulating oil contains a lot of natural antioxidants, such as rice oil. .

  Rice oil has more unsaponifiable matter than other vegetable oils, and the amount of tocoeliinol and oryzanol in unsaponifiable matter is 2% by weight or more of the total amount of rice oil. The unsaponifiable matter is a substance obtained by hydrolyzing fats and oils with an alkaline solution and removing a portion that is soluble in water, and includes the above-mentioned tocoeliinol and oryzanol.

  And said tocoeliinol and oryzanol can prevent that fats and oils are oxidized as a natural antioxidant. In other words, by selecting a vegetable oil rich in such natural antioxidants and using it as an insulating oil, it is separately oxidized to improve the oxidation stability of the insulating oil, like the vegetable oil described in the conventional example. There is no need to add an inhibitor.

  Also in the results of the oxidation stability test conducted by the inventor, it was confirmed that the JIS standard was satisfied. Moreover, since rice oil does not generate sludge at all, it has characteristics superior to mineral oil that generates sludge.

  Fig. 2 shows a comparison of physical properties between rice oil and mineral oil. The rice oil according to the present invention has a dielectric breakdown voltage which is the most important item required for insulating oil, and is equal to or higher than that of mineral oil. Moreover, since it has a high flash point, fire and disaster prevention properties are improved compared to mineral oil. Furthermore, the feature that sludge does not occur does not impair the cooling performance of the transformer due to the accumulation of sludge, and long-term operation of the transformer can be expected.

  On the other hand, since the viscosity is higher than that of mineral oil, the cooling performance is inferior to that of mineral oil. However, this should be taken into consideration when designing the transformer, and does not hinder the operation.

  In other words, the vegetable oil of the present invention sufficiently satisfies the level required for safe operation of the transformer, and is used as an insulating oil instead of the conventional mineral oil. We think that we can fully meet the request.

  Moreover, even if it is other than vegetable oils (soybean oil, rapeseed oil, etc.) which contain many natural antioxidants like rice oil, for example, L-ascorbic acid (vitamin C, VC), erythorbic acid (isoascorbic acid) Of the antioxidants recognized by the Food Sanitation Law, such as catechins, tocopherols (vitamin E, VE), etc., it is also effective to add naturally derived ones.

  According to this method, it is possible to reliably improve the oxidation stability of the vegetable oil without the antioxidant having an adverse effect on the environment.

  As described above, when the vegetable oil according to the present invention is used as an insulating oil, it is easily decomposed in natural ecosystems, so that the impact on the environment can be reliably reduced compared to mineral oil and the like, and vegetable oil Among them, select oils that contain a lot of natural antioxidants and use them as insulating oils, or use vegetable oils that contain antioxidants approved for use in foods under the Food Sanitation Law as insulating oils. This is convenient without worrying about the influence of the added antioxidant on the environment.

  The present invention has a high possibility of being used for an electric device using electric insulating oil in the device, for example, a transformer, a cable, a circuit breaker, or a capacitor.

Claims (3)

  An oil-filled electrical device using vegetable oil containing a natural antioxidant as an insulating oil.   The oil-filled electrical device according to claim 1, wherein the vegetable oil is rice oil.   An oil-filled electrical device characterized by using, as an insulating oil, a vegetable oil to which naturally derived ones of antioxidants approved for use in foods are added.

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