JPS6236328B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION Many types of electrical equipment, including transformers, cables and capacitors, contain insulating oil. In some cases, these devices lose this insulating oil when leaks occur. Loss of insulating oil draws moisture into the electrical equipment, reducing the equipment's insulation ability to the point that the electrical equipment fails. When the insulating oil is mineral oil or other colored oil and is fairly non-volatile, insulating oil leaks can be easily detected by locating the leaked insulating oil on the exterior of the electrical equipment. However, since insulating oil is colorless and volatile, it is very difficult to detect leaked oil, and it does not remain outside of electrical equipment for long, so it is difficult to detect the leaked point. Very difficult. An example of such an insulating oil is perchlorethylene, which is widely used in transformers. This insulating oil is colorless and quite volatile, which makes it difficult to detect where it has leaked, and since the volatilized insulating oil is heavier than air and almost odorless at low concentrations, perchlor. When the ethylene leaks out, it displaces the air in the room, causing some of the people in the room to become dizzy and eventually lose consciousness. SUMMARY OF THE INVENTION We have discovered that if certain fluorescent dyes are added to halogenated aliphatic electrical oils, leakage of the electrical oils can be easily detected under ultraviolet light that causes the dyes to fluoresce. The dye does not interfere with the electrical or physical properties of the insulating oil within the concentration range used. This dye can be easily added to these types of insulating oils at a relatively low cost. The dye was found to be stable in dielectric oil, non-mutagenic, and non-carcinogenic. Another advantage of using dyes is that leaks of insulating oil can be easily detected even in the wild. The reason for this is that the only means necessary for detection is ultraviolet light. Prior Art U.S. Pat. No. 4,312,794 entitled "Ultrapure Tetrafluoroethylene" filed April 2, 1980 by Pearce et al. discloses the use of ultrapure perfluoroethylene as an insulating oil in transformers. are doing. DESCRIPTION OF THE INVENTION The insulating oils useful in the compositions of this invention are halogenated aliphatic insulating oils. Suitable insulating oils include Freons, such as trifluoroethane. Particularly preferred is perchlorethylene. The reason for this is that perchlorethylene is a very good insulating oil. All of these insulating oils (liquids) are generally colorless, volatile, relatively odorless, and therefore difficult to detect. Although a number of fluorescent dyes were tested for suitability in insulating oils for use in the compositions of this invention, only one dye was found to work satisfactorily. That is, only this particular dye is sensitive enough to easily detect oil leaks, yet does not interfere with the electrical or chemical properties of the oil. Dyes that have been found to work satisfactorily have the formula: 2,2'-(2,5-thiophenedale)bis(5-t-butyl-benzoxazole). This compound has a melting point of 200℃~201℃
(392〓~394〓), solubility in water at 25℃ is 100ml
It weighs 0.1g per serving and has a specific gravity of 1.27. It is an odorless pale yellow-green powder with a maximum absorption wavelength of 375n under ultraviolet light.
emits bright blue fluorescence at m. This dye has low toxicity and is used only at very low concentrations of about 5 ppm to about 1000 ppm by weight. At concentrations below 5 ppm, the dye is not sensitive enough to be detected. Concentrations above 1000 ppm do not significantly enhance detectability and degrade the electrical properties of the insulating oil. Preferably, the dye is used at a dye concentration of about 40 ppm to about 60 ppm. Within this range, ultraviolet light can be used to detect insulating oil leaks in electrical equipment at a distance of 1.5 meters (5 feet) from the equipment. This insulating oil can be used in any electrical equipment that uses insulating oil, including transformers, cables, and capacitors, but is particularly useful in transformers. The reason for this is that large amounts of perchlorethylene are used as insulating oil in transformers, and leakage of insulating oil is a bigger problem than in other equipment. Effects of the Invention By using the composition of the present invention in electrical equipment, leaks of colorless, fairly volatile, and almost odorless insulating oil can be easily detected. This invention will be described below with reference to Examples. EXAMPLE At 125°C and 150°C using perchlorethylene (C ₂ Cl ₄ ) oil containing 50 ppm (0.005%) of dye sold under the name "UVITEX OB" by Ciba Geigy Corporation. I did a screen test for 7 days. The properties of the oil were analyzed after aging of the oil to determine whether the dye had a beneficial effect on the oil. The results are listed in the table below.

Table This table shows that the presence of dye has no adverse effect on C ₂ Cl ₄ . C ₂ Cl ₄ alone, C ₂ Cl ₄ and 50 ppm dye and C ₂ Cl ₄
Transformer element (TC), e.g. paper, with 50ppm dye
Compatibility tests were conducted using mixtures such as steel and copper. The elements were dried under reduced pressure at 125°C for 16 hours and then subjected to aging tests at 125°C and 150°C for 30, 60 and 90 days. "C ₂ Cl ₄ + 50ppm dye + T.C." in the "Period and Composition" column in the table below refers to an experiment using C ₂ Cl ₄ alone, and an experiment in which 50 ppm dye was added to C ₂ Cl ₄ (+50 ppm). , and C ₂ Cl ₄
50ppm dye and transformer element mixture (+T.C.
), and the results of each of these three experiments are shown in the table below. In the table, "precipitation" in "general condition" indicates that solid precipitate was formed at the bottom of the container.

【table】

Table: The results obtained for each of the test oils after the three aging tests indicated that the dye had no adverse effect on the properties of the test oil. The dye remaining in the test oil after the aging test remained unaltered when used in the transformer and remained active in the insulating oil for the entire life of the transformer. 0.075 mm (3 mil) thick paper that has not been subjected to aging tests and 0.075 mm (3 mil) that has been aged in perchloroethylene insulation fluid or transformer insulation oil (mineral oil) for 30 days at 125°C and 150°C. Tensile tests were conducted on paper of different thicknesses. The results for paper taken from each of perchlorethylene insulation liquid and transformer insulation oil (mineral oil) show that in the case of paper immersed in C ₂ Cl ₄ , the retention rate of tensile strength was 56.4%; The paper immersed in oil (mineral oil) had a tensile strength retention rate of 76.4%. At 150°C, paper soaked in C ₂ Cl ₄ liquid showed a retention rate of 3.4%, and paper soaked in transformer insulating oil (mineral oil) showed a retention rate of 18.8%. In this test
Although the retention rate at 125°C is significantly lower in perchlorethylene liquid than in transformer insulating oil (mineral oil), it is satisfactory for insulation in perchlorethylene oil if the transformer temperature is kept below 125°C. Can be used. Furthermore
Results at 150°C showed that the paper degraded at a faster rate in perchlorethylene than in transformer insulating oil (mineral oil).

【table】 %
Impact -60 using pure perchlorethylene and using perchlorethylene + 150ppm dye
A cycle test showed no significant difference in withstand voltage.

Claims (1)

[Claims] 1 2,2'-(2,5-thiophenedale)bis(5-t-butyl-benzoxazole)
A composition consisting of a halogenated aliphatic insulating oil containing 5 ppm to 1000 ppm. 2. The composition according to claim 1, wherein the halogenated aliphatic insulating oil is perchlorethylene. 3. The composition according to claim 1, wherein the concentration of 2.2'-(2.5-thiophenedale)bis(5-t-butyl-benzoxazole) is 40 ppm to 60 ppm. 4 In a method for detecting leakage of insulating oil from electrical equipment containing insulating oil, (A) 2,2'-(2,5-thiophenedale)bis(5-t-butyl-benzoxazole) is used as insulating oil at 5 ppm or more. using a composition comprising a halogenated aliphatic insulating oil containing 1000 ppm; (B) exposing the electrical device to ultraviolet light; and (C) detecting areas on the electrical device that emit blue fluorescence. A method for detecting insulating oil leakage from electrical equipment. 5 Claim 4 in which the electrical equipment is a transformer
The method described in section.