JP2010027634A - Oil-filled electric apparatus, and method for preventing deposition of copper sulfide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preventing deposition of copper sulfide onto insulating paper by a simple method without pretreatment of insulating oil (removal of a copper sulfide forming sulfur component), addition of a metal passivator and the like and a transformer configured almost hermetically, and to provide an oil-filled electric apparatus. <P>SOLUTION: The invention provides the oil-filled electric apparatus in which a copper component and the insulating paper are dipped in the insulating oil in a container. The apparatus is characterized by including an oxygen removing means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an oil-filled electrical device such as an oil-filled transformer in which a plurality of copper components and insulating paper sandwiched between them are immersed in the electrical insulating oil. The present invention relates to a method for preventing copper sulfide from precipitating on insulating paper by reacting with a substance that produces copper.

  In electrical equipment where transformers and other copper parts and insulators sandwiched between them are immersed in electrical insulation oil, the copper components in the equipment and the sulfur component in the electrical insulation oil (causative substances for copper sulfide) A phenomenon is known in which copper sulfide is deposited on the surface of insulating paper and the insulating performance of the insulating paper is impaired.

  However, details of the copper sulfide formation mechanism are not known. For this reason, at present, in order to prevent the precipitation of copper sulfide, attempts have been made to develop a technology for removing sulfur components in the insulating oil and to add a metal passivator.

  Patent Document 1 discloses a technology for removing sulfur components in insulating oil. The sulfur component removal apparatus disclosed in Patent Document 1 is shown in FIG. In FIG. 6, the insulating oil 3 introduced into the container 1 from the introduction pipe 7 comes into contact with the copper powder in the container 1. Reference numeral 9 denotes a stirring device that stirs the insulating oil 3 to prevent the copper powder 4 from settling. Reference numerals 10A and 10B denote heaters that are provided below the outside of the container 1 to heat the insulating oil 3. Reference numeral 11 denotes an injection pipe for connecting the container 1 to an oil-filled electrical device main body (not shown) and injecting the insulating oil from which sulfur compounds have been removed into the oil-filled electrical device main body. The injection pipe 11 captures copper. And a filter 112 for preventing the adsorbent 111 and copper powder from entering the oil-filled electrical device main body.

  On the other hand, Non-Patent Document 1 discloses a technique of adding a metal passivator (benzotriazole) to an insulating oil in order to prevent copper from being dissolved in the insulating oil.

  In addition, regarding the mechanism of copper sulfide formation, it has recently been reported that dibenzyl disulfide (hereinafter abbreviated as “DBDS”) is a causative substance of copper sulfide generation among sulfur components contained in insulating oil (non-sulphur). Patent Document 2).

  By the way, as will be described later, in the insulating oil containing a sulfur component (copper sulfide generation causative substance), the present inventors are greatly influenced by the generation of copper sulfide on the insulating paper, and the presence of oxygen generates copper sulfide. Was found to be promoted. Therefore, it is necessary to prevent the dissolution of oxygen in the insulating oil in order to prevent copper sulfide from forming on the insulating paper. As a method for preventing the dissolution of oxygen in insulating oil, it is disclosed to install an insulating plate or a diaphragm on the insulating oil surface. In Patent Document 2, an insulating plate is provided on the insulating oil to prevent deterioration of the insulating oil. In Patent Document 3, a diaphragm is provided between the insulating oil and the gas phase in order to prevent corrosion of the container containing the insulating oil. This configuration does not newly absorb outside air, does not require a hygroscopic agent, and prevents condensation inside the transformer and corrosion of the tank due to this.

  By the way, as a method for preventing deterioration of insulating oil in a transformer, an open type using a moisture absorbing material such as an inert gas sealing type, a diaphragm type, or silica gel is known (Non-Patent Document 3). In the inert gas-filled type / diaphragm type, there is almost no breathing between the container containing the insulating oil and the outside air, so that air hardly mixes in the container. Therefore, the production of copper sulfide is suppressed. On the other hand, in the open type, a container containing insulating oil breathes with the outside air, so that air is mixed.

Since the container described in Patent Document 2 is considered to correspond to a diaphragm type due to its structure, there is almost no air contamination. Moreover, since the structure of the transformer of Patent Document 3 that prevents the insulating oil from coming into contact with the outside air is considered to correspond to a diaphragm type, there is almost no air mixing. Therefore, in both Patent Document 2 and Patent Document 3, the insulating oil hardly comes into contact with the outside air, but a structure close to a sealed type is required, so that the manufacturing process of the oil-filled electrical device increases.
JP 2001-311083 A Japanese Patent Laid-Open No. 9-22822 JP 2006-295017 A Per Wiklund, Chemical Stability of Benzotriazole Copper Surface Passivators in Insulating Oils, 2007, Industrial & engineering chemistry research, 46, 3312-3316 R. Maina, F. Scatiggio, S. Kapila, V. Tumiatti, and M. Tumiatti and M. “Pompilli, Dibenzyl disulfide (DBDS) as corrosive sulfur Contaminant in used and unused mineral insulating oils”, [online], CIGRE ( International Council on Large Electric Systems), [Search June 24, 2008] Internet <URL: http://www.cigre-a2.org/Site/Publications/download/DBDS_paper_ColorVersionID44VER52.pdf> “Cooling method of electrical equipment”, [online], free encyclopedia “Wikipedia”, [searched on June 24, 2008], Internet <URL: http://en.wikipedia.org/wiki/%E9%9B % BB% E6% B0% 97% E6% A9% 9F% E5% 99% A8% E3% 81% AE% E5% 86% B7% E5% 8D% B4% E6% 96% B9% E5% BC% 8F >

  The present invention relates to an open-type transformer using an insulating oil containing a sulfur component (a copper sulfide producing causative substance), which dissolves oxygen in the insulating oil even if outside air enters the container containing the insulating oil. The problem is to prevent it. In Patent Document 1, a pretreatment facility for insulating oil is required. In Non-Patent Document 2, benzotriazole is added again as benzotriazole is consumed. In Patent Documents 2 and 3, a closed-type transformer is used. Although a structure is required, the present invention does not require such pretreatment of insulating oil (removal of sulfur components that produce copper sulfide) and addition of a metal passivator, or a structure of a transformer close to a sealed type. Another object of the present invention is to provide a method and an oil-filled electrical device that can prevent copper sulfide from being deposited on insulating paper by a simple method.

  The present invention relates to an open-type oil-filled electrical device in which a copper part and insulating paper are immersed in insulating oil in a container, and in order to prevent oxygen from being dissolved in the insulating oil, the air is relatively simple. Means for removing oxygen therein (oxygen removing means) is provided.

  It is preferable to use a metal sheet and / or an oxygen scavenger containing two or more kinds of metals having different ionization tendencies provided in the gas phase in the container as the oxygen removing means. In the metal sheet, it is preferable that two or more kinds of metals having different ionization tendencies consist of a combination of copper or silver and aluminum, zinc or an alloy thereof. Among the two or more metals having different ionization tendencies, aluminum, zinc, and alloys thereof are used as the metal having a large ionization tendency. The oxygen scavenger preferably contains at least one of iron, ascorbic acid, gallic acid and glycerin.

  Further, the present invention provides an insulating paper, characterized in that oxygen in a gas phase in a container is removed in an open-type oil-filled electrical device in which a copper part and insulating paper are immersed in insulating oil in the container. This also relates to a method for preventing the precipitation of copper sulfide.

  In the present invention, by providing the oxygen removing means, it is possible to prevent oxygen from being dissolved in the insulating oil by a simple method, and the sulfur component that is a copper sulfide generation causative substance is contained in the insulating oil. Even when it is present, the precipitation of copper sulfide on the insulating paper is suppressed.

  In the system in which insulating oil, copper, and insulating paper coexist, in the oil-filled electrical device and the method for preventing copper sulfide precipitation of the present invention that can prevent copper sulfide from precipitating on the insulating paper, the air contained in the container Means for removing oxygen (oxygen removing means) are necessary. As a means for removing oxygen, a metal sheet or oxygen scavenger containing two or more metals having different ionization tendencies is used. These methods may be used simultaneously.

  Aluminum (hereinafter referred to as Al), zinc (hereinafter referred to as Zn) or an alloy thereof, or a steel plate plated with Al or Zn is used as a metal having a large ionization tendency used for a metal sheet containing two or more kinds of metals having different ionization tendencies. .

  When Al or Zn is used, the thickness of Al or Zn is preferably 0.05 to 5 mm. If the thickness is 0.05 mm or less, it is soft and not rigid, so that it is difficult to install in a container and the availability is poor. On the other hand, when the thickness is 5 mm or more, it is difficult to mount the container in the container due to an increase in weight, and the availability is poor. An Al plate or a Zn plate is placed inside the container containing the insulating oil and in the gas phase part. In the open type, the dissolution reaction of Al or Zn (formula (i) or (ii)) and the surface of the container material (steel) on the surface of the Al plate or Zn plate by water vapor due to evaporation of moisture mixed in the insulating oil Thus, an oxygen reduction reaction (formula (iii)) occurs, and oxygen in the air is removed by the oxygen reduction reaction.

Al → Al ³⁺ + 3e (i)
Zn → Zn ²⁺ + 2e (ii)
1 / 2O ₂ + H ₂ O + 2e → 2OH ⁻ (iii)
Generally, steel used as a container material is electrically connected to an Al plate or a Zn plate. As a result, the difference in natural potential due to the combination of steel and Al or the combination of steel and Zn serves as a driving force to promote the oxygen reduction reaction occurring on the steel surface. Moreover, the side effect that corrosion of steel can be prevented by the combination of these materials also arises.

  In order to further increase the difference in natural potential, a metal with a low ionization tendency, such as copper or silver, is electrically connected and installed on the surface of the Al plate or Zn plate. FIG. 1 is a diagram in which a metal having a small ionization tendency is placed on the surface of an Al plate or a Zn plate. In FIG. 1, 51 is an Al plate or Zn plate, 52 is a metal having a low ionization tendency, and 53 is a distance between metals having a low ionization tendency.

  The metal 52 is used as a plate thickness of 0.05 to 1 mm from the viewpoint of availability and workability. The metal 52 may be fixed to the metal 51 using a bolt or the like. The distance 53 is preferably 5 to 10 mm. If it is 5 mm or less, the workability of attaching the metal 52 is poor, and if it is 10 mm or more, the effect of promoting the oxygen reduction reaction by the combination with the metal 52 becomes small.

  Another method for removing oxygen in the air is to use an oxygen scavenger. In this method, oxygen in the gas phase is removed by keeping the oxygen scavenger in the gas phase in contact with the insulating oil. Examples of the oxygen scavenger used include inorganic oxygen scavengers and organic oxygen scavengers.

  Examples of the inorganic oxygen scavenger include iron powder and sulfite. For example, iron powder removes oxygen in the gas phase by its oxidation. The average particle size of the iron powder is preferably in the range of 50 μm to 500 μm. Below 50μm, the iron powder has a large surface area and is active, so it may be oxidized before it is installed in the gas phase of oil-filled electrical equipment and lose its effectiveness. Above 500μm, the oxidation reaction rate is slow and the oxygen removal ability Is inferior. A method for removing oxygen in a gas phase by utilizing oxidation of iron is known and commercialized as an oxygen scavenger. For example, “AGELESS (registered trademark) SA type” manufactured by Mitsubishi Gas Chemical Co., Ltd. using an iron-based reaction main agent is commercially available and can be applied as the oxygen scavenger of the present invention.

  Examples of the organic oxygen scavenger include ascorbic acid, gallic acid, glycerin and the like, and are commercialized as various oxygen scavengers. For example, “AGELESS (registered trademark) GL type” manufactured by Mitsubishi Gas Chemical Co., Ltd. using an organic reaction main agent is commercially available.

  Both the physical and chemical methods described above are effective in removing oxygen, but should be selected taking into account the gas phase volume of oil-filled electrical equipment, operating frequency, availability of inert gases and oxygen scavengers. That's fine.

  By using a metal or oxygen scavenger having a large ionization tendency, oxygen in the air can be removed and the formation of copper sulfide is suppressed, but oxygen cannot be completely removed. As a result, residual oxygen is dissolved in the insulating oil. Therefore, when an air barrier layer is used in combination with these oxygen removing means to prevent dissolution of residual oxygen in the insulating oil, a further effect of suppressing copper sulfide can be obtained.

  As the air barrier layer provided on the insulating oil surface in contact with the gas phase, a floating ball, a sheet, or the like can be used. As for the floating ball, it is preferable to use a floating ball (such as a pneumatic floating ball) having a diameter in the range of 1 mm to 20 mm. This is because if the size is 1 mm or less, the manufacture is difficult, and if it is 20 mm or more, the air blocking ability is reduced. In addition, it is preferable to use polypropylene, polyethylene, Teflon, and nylon as the material of the floating ball. As for the sheet, it is preferable to use a sheet having a thickness in the range of 0.2 mm to 1 mm. If the thickness is 0.2 mm or less, it is difficult to produce a sheet. If the thickness is 1 mm or more, the insulating oil surface cannot be covered because it sinks from the insulating oil surface due to its own weight. Further, it is preferable to use polyethylene, Teflon, nylon or the like as the material of the sheet.

(Copper sulfide precipitation test)
The influence of oxygen on the deposition of copper sulfide on the insulating paper of oil-filled electrical equipment has not been clarified so far. The inventors quantitatively investigated the influence of oxygen on the precipitation of copper sulfide on insulating paper using an insulating oil artificially containing DBDS. The copper sulfide precipitation test on the insulating paper was performed in a nitrogen atmosphere and a mixed gas of nitrogen and oxygen (80% N ₂ + 20% O ₂ ), with the copper plate and the insulating paper being spaced 5 mm apart, This was performed by immersing in an insulating oil containing DBDS and heating at 120 ° C. for 144 hours. The insulating oil, copper plate, and insulating paper used for the precipitation test are as follows.

Insulating oil: 50 ml of alkylbenzene containing 1154 ppm of DBDS (300 ppm in terms of sulfur) Copper plate: Pure copper (4 pieces of size 30 x 50 x 0.2 mm)
Insulating paper: Kraft paper (size 10 × 19 × 0.08 mm).

After heating, the insulating paper was taken out and immersed in 2M nitric acid for 1 hour to dissolve the precipitated copper in nitric acid, and then the copper was quantified using a plasma emission spectrometer. As a result of measuring the amount of copper deposited on the insulating paper (kraft paper) after heating, the amount of copper deposited in the mixed gas (80% N ₂ + 20% O ₂ ) atmosphere was 19.5 μg / cm ² , and the precipitation in the nitrogen atmosphere The amount of copper was 3.9 μg / cm ² .

From the above results, the amount of copper deposited on the insulating paper in a mixed gas (80% N ₂ + 20% O ₂ ) atmosphere is five times that of the nitrogen atmosphere, and the amount of copper deposited on the insulating paper increases due to the presence of oxygen. I understood. It was confirmed by X-ray photoelectron spectroscopy that copper deposited on the insulating paper was present as copper sulfide. Thus, it was found that even when DBDS, which is a causative substance of copper sulfide generation, is contained in the insulating oil, the precipitation of copper sulfide on the insulating paper is suppressed in an atmosphere where oxygen is not present.

  Hereinafter, the present invention will be described in more detail with reference to specific embodiments of the effect of suppressing the precipitation of copper sulfide on insulating paper for electrical equipment by removing oxygen, but the present invention is not limited to these.

(Embodiment 1)
FIG. 2 is a diagram showing an embodiment (Embodiment 1) of a simulated open-type oil-filled electrical device and a method for preventing copper sulfide from being deposited on insulating paper using the present invention. 1 is made of steel, filled with insulating oil 2, and a copper plate wrapped with insulating paper is immersed therein. The copper plate 3 wound with insulating paper is a copper plate (size 10 × 40 × 0.2 mm) wound with insulating paper (size 12 × 100 × 0.08 mm kraft paper). It is a simulation. 4 is a gas phase filled with air. Reference numeral 12 denotes an air outflow inlet. 5 is a metal sheet in which a Cu plate (size 10 × 300 × 1 mm) is attached to an Al plate (size 300 × 400 × 1 mm), and has a shape as shown in FIG. 1 in which the Cu plates are arranged at intervals of 10 mm.

The container 1 was heated at 120 ° C. for 12 days, and the amount of copper deposited on the insulating paper wound on the heated copper plate was examined. The amount of copper deposited on the insulating paper when an Al plate with a Cu plate attached thereto was 12 μg / cm ² . On the other hand, the amount of copper deposited on the insulating paper after heating at 120 ° C. for 12 days without installing the Al plate with the Cu plate attached thereto was 24 μg / cm ² . From the above results, it can be seen that the amount of copper deposited on the insulating paper is suppressed by providing an Al plate with a Cu plate attached thereto.

  In this embodiment, an Al plate with a Cu plate attached is used as the metal sheet, but a Zn plate or the like may be used instead of the Al plate.

(Embodiment 2)
FIG. 3 is a diagram showing an embodiment (Embodiment 2) of a simulated open-type oil-filled electrical device and a method for preventing the precipitation of copper sulfide on insulating paper using the present invention. The container 1, the insulating oil 2, the insulating paper 3, the gas phase 4, and the air outflow / inlet 12 are the same as those in the first embodiment. 5 is a metal sheet in which a Cu plate (size 10 × 300 × 1 mm) is attached to an Al plate (size 300 × 400 × 1 mm), and has a shape shown in FIG. 1 in which the Cu plates are arranged at intervals of 10 mm. Reference numeral 61 denotes a float (oxygen blocking means), and a polypropylene float (diameter 10 mm) was used.

One container was heated at 120 ° C. for 12 days, and the amount of copper deposited on the insulating paper wound around the heated copper plate was examined. As a result, the amount of copper deposited on the insulating paper was 10 μg / cm ² when an Al plate attached with a Cu plate was installed and a floating ball made of polypropylene was used. On the other hand, the amount of copper deposited on the insulating paper after heating at 120 ° C. for 12 days without providing an Al plate with a Cu plate and a float was 24 μg / cm ² . From the above results, it can be seen that the amount of copper deposited on the insulating paper is suppressed by providing the float.

(Embodiment 3)
FIG. 4 is a diagram showing another embodiment (Embodiment 3) of a simulated open-type oil-filled electrical device and a method for preventing copper sulfide from depositing on insulating paper using the present invention. The container 1, the insulating oil 2, the insulating paper 3, the gas phase 4, and the air outflow / inlet 12 are the same as those in the first embodiment. 5 is a metal sheet in which a Cu plate (size 10 × 300 × 1 mm) is attached to an Al plate (size 300 × 400 × 1 mm), and has a shape shown in FIG. 1 in which the Cu plates are arranged at intervals of 10 mm. 62 is a sheet (oxygen blocking means), and a nylon sheet (0.1 mm thick) was used.

The container 1 was heated at 120 ° C. for 12 days, and the amount of copper deposited on the insulating paper wound on the heated copper plate was examined. As a result, the amount of copper deposited on the insulating paper was 10 μg / cm ² when an Al plate attached with a Cu plate was installed and a nylon sheet was used. On the other hand, the amount of copper deposited on the insulating paper after heating for 12 days at 120 ° C. without an Al plate attached with a Cu plate and without a sheet was 24 μg / cm ² . From the above results, it can be seen that the amount of copper deposited on the insulating paper is suppressed by providing an Al plate and a sheet to which a Cu plate is attached.

  In this embodiment, a sheet having a thickness of 0.1 mm is used, but a sheet having a thickness in the range of about 0.2 mm to 1 mm can be used. In addition to nylon, polypropylene, polyethylene, Teflon, etc. can be used as the material for the sheet.

(Embodiment 4)
FIG. 5 is a diagram showing still another embodiment (embodiment 4) of a simulated open-type oil-filled electrical device and a method for preventing copper sulfide from depositing on insulating paper using the present invention. The container 1, the insulating oil 2, the insulating paper 3, the gas phase 4, and the air outflow / inlet 12 are the same as those in the first embodiment. 63 is an oxygen scavenger, and was installed in the container at a ratio of 10 per 1 L of gas phase volume. As the oxygen scavenger, “AGELESS (registered trademark) SA type” manufactured by Mitsubishi Gas Chemical Co., Ltd., which is an inorganic oxygen scavenger, was used.

The container 1 was heated at 120 ° C. for 12 days, and the amount of copper deposited on the insulating paper wound on the heated copper plate was examined. As a result, the amount of copper deposited on the insulating paper when the oxygen scavenger was installed was 12 μg / cm ² . On the other hand, the amount of copper deposited on the insulating paper after heating at 120 ° C. for 12 days without a sheet was 24 μg / cm ² . From the above results, it can be seen that the amount of copper deposited on the insulating paper is suppressed by providing an oxygen scavenger in the gas phase.

  In this embodiment, an inorganic oxygen scavenger is used as the oxygen scavenger, but the same effect can be obtained even if an organic oxygen scavenger is used.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the structure of the metal sheet which installed the metal with a small ionization tendency on the surface of the Al plate or Zn plate used by this invention. It is a figure which shows Embodiment 1 of this invention. It is a figure which shows Embodiment 2 of this invention. It is a figure which shows Embodiment 3 of this invention. It is a figure which shows Embodiment 4 of this invention. It is a figure which shows the removal apparatus of the sulfur compound in the conventional insulating oil.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Container, 10A, 10B Heater, 11 Injection piping, 111 Adsorbent, 112 Filter, 12 Air outflow inlet, 2 Insulation oil, 3 Copper plate which wound insulation paper, 4 Gas phase, 5 Metal sheet, 51 Al plate or Zn plate , 52 Metal with low ionization tendency, 53 Distance between metals with low ionization tendency, 61 Float, 62 sheet, 63 Oxygen scavenger, 7 Introducing pipe, 8 Copper powder, 9 Stirrer.

Claims (6)

  An oil-filled electrical device, which is an open-type oil-filled electrical device in which a copper part and insulating paper are immersed in insulating oil in a container, and has oxygen removing means.   The oil-filled electrical device according to claim 1, wherein the oxygen removing means includes a metal sheet including two or more kinds of metals having different ionization tendencies provided in a gas phase in a container.   The oil-filled electrical device according to claim 2, wherein the two or more kinds of metals having different ionization tendencies are a combination of copper or silver and aluminum, zinc or an alloy thereof.   The oil-filled electrical apparatus according to claim 1, wherein the oxygen removing means includes an oxygen scavenger.   The oil-filled electrical device according to claim 4, wherein the oxygen scavenger contains at least one of iron, ascorbic acid, gallic acid, and glycerin.   In open-type oil-filled electrical equipment in which copper parts and insulating paper are immersed in insulating oil in the container, the deposition of copper sulfide on the insulating paper is characterized by removing oxygen in the gas phase in the container Prevention method.

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