Abstract: A temperature estimation method estimating a temperature of a heat generating site in an oil-immersed electric appliance immersed in insulating oil, the insulating oil being silicone oil or ester oil. The temperature estimation method includes measuring concentrations of two types of thermal decomposition products in the insulating oil and calculating a temperature of the heat generating site in the oil-immersed electric appliance based on a concentration ratio between the two types of thermal decomposition products and a relational expression between the temperature of the heat generating site and the concentration ratio prepared in advance. When the silicone oil is adopted as the insulating oil, at least one of the two types of thermal decomposition products is straight-chain siloxane, alcohol containing silicon, or benzene. When the ester oil is adopted as the insulating oil, the two types of thermal decomposition products are fatty acids.

Abstract: A temperature estimation method estimating a temperature of a heat generating site in an oil-immersed electric appliance immersed in insulating oil, the insulating oil being silicone oil or ester oil. The temperature estimation method includes measuring concentrations of two types of thermal decomposition products in the insulating oil and calculating a temperature of the heat generating site in the oil-immersed electric appliance based on a concentration ratio between the two types of thermal decomposition products and a relational expression between the temperature of the heat generating site and the concentration ratio prepared in advance. When the silicone oil is adopted as the insulating oil, at least one of the two types of thermal decomposition products is straight-chain siloxane, alcohol containing silicon, or benzene. When the ester oil is adopted as the insulating oil, the two types of thermal decomposition products are fatty acids.

Abstract: A testing method of the present invention is a testing method for examining a degree of deterioration, due to oxygen, of an object material constituting an oil-filled electrical apparatus. The oil-filled electrical apparatus is an open-type oil-filled electrical apparatus including an insulating oil, an insulator, and a conductor, the insulating oil being contained as being in contact with the atmosphere. The object material is at least any of the insulating oil, the insulator, and the conductor. The testing method includes putting the insulating oil and the object material into a testing tank, keeping a state where dry air is continuously supplied to the upper space in the testing tank, and subsequently performing measurement of an index of deterioration of the object material due to oxygen.

Abstract: The present invention is a method for preventing copper sulfide generation in oil-filled electrical equipment having an inhibitor of copper sulfide generation in insulating oil, and the method is characterized in monitoring characteristics of the insulating oil and performing re-addition of the inhibitor at an appropriate moment in accordance with a result of the monitoring.

Abstract: The present invention relates to an electric insulating oil inspection method for determining whether or not an inhibitor-consuming substance is present in an electric insulating oil. The inhibitor-consuming substance is such a substance that causes to decrease over time a concentration of an inhibitor which is added to the electric insulating oil to inhibit copper sulfide from being generated on an insulating paper immersed in the electric insulating oil. The electric insulting oil inspection method includes steps of: preserving the electric insulating oil at a predetermined condition, measuring a concentration of the inhibitor, and determining that the inhibitor-consuming substance is present upon condition that a decrement of the concentration of the inhibitor relative to an initial concentration of the inhibitor becomes not less than a specified amount within a predetermined period.

Abstract: A diagnosis method for oil-filled electrical equipment, for diagnosing a risk of occurrence of an abnormality caused by generation of copper sulfide on insulating paper, wherein a step 1 of conducting sulfidation corrosion evaluation of insulating oil in the oil-filled electrical equipment is performed, any one of a step 2A-1 of analyzing the insulating oil for presence of dibenzyldisulfide and an oxidative degradation preventing agent, a step 2A-2 of analyzing the insulating oil for presence of a copper sulfide generation inhibitor, and a step 2B of checking presence of oxygen in an atmosphere of the insulating oil is performed, a step 3 of analyzing the insulating oil for presence of a byproduct derived when copper sulfide is generated from dibenzyldisulfide is performed, and a step 4 of diagnosing the risk of occurrence of an abnormality based on results of the steps 1, 2A-1, 2A-2, and 3 is performed.

Abstract: An object of the invention is to provide a diagnostic method for an oil-filled electrical device that considers a temperature distribution in the oil-filled electrical device and enables accurate diagnosis to be conducted even when the method is applied to diagnosis of an actually operating device, and further provide a method with which such diagnosis of an oil-filled electrical device can be conducted from a component analysis value of an insulating oil in the oil-filled electrical device. The invention is a diagnostic method for an oil-filled electrical device including in an insulating oil a metal part wrapped with insulating paper, and determines that a time when a surface resistivity of a maximum precipitation site where metal sulfide is most precipitated on the insulating paper reaches a preset surface resistivity management value is a time of occurrence of an abnormality.

Abstract: The present invention is a method for preventing copper sulfide generation in oil-filled electrical equipment having an inhibitor of copper sulfide generation in insulating oil, and the method is characterized in monitoring characteristics of said insulating oil and performing re-addition of said inhibitor at an appropriate moment in accordance with a result of said monitoring.

Abstract: The present invention provides a method for inhibiting production of copper sulfide in an electrical insulating oil inside an oil-filled electrical apparatus, including adding a benzotriazole compound not having a long-chain alkyl group when the oil-filled electrical apparatus is an open-type oil-filled electrical apparatus, or adding a benzotriazole compound having a long-chain alkyl group when the oil-filled electrical apparatus is a closed-type oil-filled electrical apparatus.

Abstract: The present invention provides a method for inhibiting production of copper sulfide in an electrical insulating oil inside an oil-filled electrical apparatus, including adding a benzotriazole compound not having a long-chain alkyl group when the oil-filled electrical apparatus is an open-type oil-filled electrical apparatus, or adding a benzotriazole compound having a long-chain alkyl group when the oil-filled electrical apparatus is a closed-type oil-filled electrical apparatus.

Abstract: The present invention relates to an electric insulating oil inspection method for determining whether or not an inhibitor-consuming substance is present in an electric insulating oil. The inhibitor-consuming substance is such a substance that causes to decrease over time a concentration of an inhibitor which is added to the electric insulating oil to inhibit copper sulfide from being generated on an insulating paper immersed in the electric insulating oil. The electric insulting oil inspection method includes steps of: preserving the electric insulating oil at a predetermined condition, measuring a concentration of the inhibitor, and determining that the inhibitor-consuming substance is present upon condition that a decrement of the concentration of the inhibitor relative to an initial concentration of the inhibitor becomes not less than a specified amount within a predetermined period.

Abstract: An initial concentration of the residual concentration of a causative substance contained in an insulating oil is compared with a reference value. The causative substance reacts with a conductor forming a winding of an oil-filled electrical device to generate an electrically conductive compound. The reference value is defined as a value for determining whether a main determinant that determines the lifetime of the oil-filled electrical device is generation of the electrically conductive compound or degradation of insulating paper. Based on the initial concentration of the causative substance and the reference value, the lifetime of the oil-filled electrical device is assessed.

Abstract: Provided is a diagnosis method for an oil-filled electrical apparatus, which is for evaluating the degree of danger of copper sulfide being generated within the oil-filled electrical apparatus, comprising: a first step for detecting a specific compound contained within insulating oil inside the oil-filled electrical apparatus; a second step for evaluating the possibility of copper sulfide being generated inside the oil-filled electrical apparatus, on the basis of the result detected by the first step; and a third step for diagnosing the degree of danger of a malfunction occurring in the oil-filled electrical apparatus, on the basis of the evaluation result obtained in the second step. The specific compound contains dibenzyl disulfide and/or a reaction product of a radical resulting from dibenzyl disulfide, and di-tert-butyl-p-cresol and/or a reaction product of a radical resulting from di-tert-butyl-p-cresol, or, di-tert-butyl-phenol and/or a reaction product of a radical resulting from di-tert-butyl-phenol.

Abstract: An oil immersed electrical apparatus such as an oil immersed transformer that can detect copper sulfide precipitated on coil insulating paper is provided. In the oil immersed transformer in which a coil with its surface covered by insulating paper is arranged in a container filled with insulating oil, a detection member is prepared by providing two electrodes on a surface of a plate-like pressboard formed of cellulose, which is a same material as that of the insulating paper, this detection member is arranged in contact with the insulating oil, and generation of copper sulfide is detected from reduction in a surface resistance between the electrodes. The temperature of the detection member is set higher than the temperature of the coil so that copper sulfide is generated thereon prior to generation of copper sulfide on a coil unit.

Abstract: A method allowing an accurate diagnosis of a failure of an oil-filled electrical apparatus resulting from production of copper sulfide even with a small amount of an insulating oil is implemented. A diagnostic method for an oil-filled electrical apparatus for diagnosing a failure of the oil-filled electrical apparatus having a copper part disposed in an insulating oil is implemented by detecting at least one compound of bibenzyl and dibenzyl sulfide in the oil of the oil-filled electrical apparatus, to diagnose a failure of the oil-filled electrical apparatus in accordance with the detected amount of the compound. It is configured such that a failure of the oil-filled electrical apparatus resulting from production of copper sulfide can be diagnosed by detecting a specified substance, which allows an accurate diagnosis of a failure even with a small amount of the insulating oil.

Abstract: The present invention is a method of predicting the probability of abnormality occurrence in an oil-filled electrical device, including the steps of: measuring a residual dibenzyl disulfide concentration in an insulating oil sampled from an oil-filled electrical device in operation; determining an estimated decrease of the residual dibenzyl disulfide concentration, relative to an initial dibenzyl disulfide concentration at the start of operation of the oil-filled electrical device; calculating the initial dibenzyl disulfide concentration from the residual dibenzyl disulfide concentration and the estimated decrease; and comparing the initial dibenzyl disulfide concentration with a specific management value.

Abstract: A method for predicting the possibility of occurrence of an anomaly includes compositionally analyzing an insulating oil collected from a transformer in operation, calculating an estimated value of a concentration of dibenzyl disulfide in the insulating oil in its virgin state from the compositional analysis, and predicting the possibility of occurrence of anomaly in the oil-filled electrical apparatus from the level of the estimated value.

Abstract: An initial concentration of the residual concentration of a causative substance contained in an insulating oil is compared with a reference value. The causative substance reacts with a conductor forming a winding of an oil-filled electrical device to generate an electrically conductive compound. The reference value is defined as a value for determining whether a main determinant that determines the lifetime of the oil-filled electrical device is generation of the electrically conductive compound or degradation of insulating paper. Based on the initial concentration of the causative substance and the reference value, the lifetime of the oil-filled electrical device is assessed.

Abstract: An oil immersed electrical apparatus such as an oil immersed transformer that can detect copper sulfide precipitated on coil insulating paper is provided. In the oil immersed transformer in which a coil with its surface covered by insulating paper is arranged in a container filled with insulating oil, a detection member is prepared by providing two electrodes on a surface of a plate-like pressboard formed of cellulose, which is a same material as that of the insulating paper, this detection member is arranged in contact with the insulating oil, and generation of copper sulfide is detected from reduction in a surface resistance between the electrodes. The temperature of the detection member is set higher than the temperature of the coil so that copper sulfide is generated thereon prior to generation of copper sulfide on a coil unit.

Abstract: An object of the invention is to provide a diagnostic method for an oil-filled electrical device that considers a temperature distribution in the oil-filled electrical device and enables accurate diagnosis to be conducted even when the method is applied to diagnosis of an actually operating device, and further provide a method with which such diagnosis of an oil-filled electrical device can be conducted from a component analysis value of an insulating oil in the oil-filled electrical device. The invention is a diagnostic method for an oil-filled electrical device including in an insulating oil a metal part wrapped with insulating paper, and determines that a time when a surface resistivity of a maximum precipitation site where metal sulfide is most precipitated on the insulating paper reaches a preset surface resistivity management value is a time of occurrence of an abnormality.