Abstract: The present invention provides a method of diagnosing an oil-immersed electrical apparatus by an assessment of a state of deterioration of the oil-immersed electrical apparatus including an insulating oil. The insulating oil has been subjected to changing from mineral oil to vegetable oil.

Abstract: The present invention is directed to a method of estimating an overheating temperature of an oil-immersed electric appliance in which ester oil is used as insulating oil. The overheating temperature is estimated based on a first concentration ratio representing a concentration ratio between two types of gas components contained in the ester oil and a second concentration ratio representing a concentration ratio between other two types of gas components contained in the ester oil. The first concentration ratio and the second concentration ratio are selected from a concentration ratio between acetylene and ethane, a concentration ratio between acetylene and hydrogen, a concentration ratio between acetylene and methane, and a concentration ratio between acetylene and ethylene.

Abstract: The present invention is directed to a method of estimating an overheating temperature of an oil-immersed electric appliance in which ester oil is used as insulating oil. The overheating temperature is estimated based on a first concentration ratio representing a concentration ratio between two types of gas components contained in the ester oil and a second concentration ratio representing a concentration ratio between other two types of gas components contained in the ester oil. The first concentration ratio and the second concentration ratio are selected from a concentration ratio between acetylene and ethane, a concentration ratio between acetylene and hydrogen, a concentration ratio between acetylene and methane, and a concentration ratio between acetylene and ethylene.

Abstract: The present invention is a diagnosis method for internal fault of an oil-immersed electric apparatus using a silicone oil as an insulating oil. The method diagnoses an internal fault of the oil-immersed electric apparatus based on a first concentration ratio that is a concentration ratio between two gases selected from an analysis gas group consisting of hydrogen gas, methane gas, ethane gas, and ethylene gas contained in the, silicone oil, and a second concentration ratio that is a concentration ratio between the other two gases selected from the analysis gas group. A combination of the two gases and a combination of the other two gases are a combination of ethylene gas and hydrogen gas, a combination of ethane gas and hydrogen gas, a combination of ethylene gas and methane gas, or a combination of methane gas and ethane gas.

Abstract: The method for diagnosing the oil-filled electrical apparatus in the present invention is a method for diagnosing whether or not discharge has occurred inside the oil-filled electrical apparatus. The diagnosing method includes: an in-oil gases analyzing step of analyzing hydrogen gas and a gas selected from the group consisting of methane, ethane, ethylene, acetylene, hydrocarbon having a carbon number of 3 or 4, carbon monoxide, carbon dioxide, oxygen, and nitrogen, contained in an insulating oil used inside the oil-filled electrical apparatus; a step of analyzing a causative substance serving as a cause of generation of hydrogen in the insulating oil irrespective of whether or not the discharge has occurred; and a step of diagnosing whether or not the discharge has occurred based on an analysis result of the in-oil gases analyzing step and an analysis result of the step of analyzing the causative substance.

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 diagnosis method for internal fault of an oil-immersed electric apparatus using a silicone oil as an insulating oil. The method diagnoses an internal fault of the oil-immersed electric apparatus based on a first concentration ratio that is a concentration ratio between two gases selected from an analysis gas group consisting of hydrogen gas, methane gas, ethane gas, and ethylene gas contained in the, silicone oil, and a second concentration ratio that is a concentration ratio between the other two gases selected from the analysis gas group. A combination of the two gases and a combination of the other two gases are a combination of ethylene gas and hydrogen gas, a combination of ethane gas and hydrogen gas, a combination of ethylene gas and methane gas, or a combination of methane gas and ethane gas.

Abstract: The method for diagnosing the oil-filled electrical apparatus in the present invention is a method for diagnosing whether or not discharge has occurred inside the oil-filled electrical apparatus. The diagnosing method includes: an in-oil gases analyzing step of analyzing hydrogen gas and a gas selected from the group consisting of methane, ethane, ethylene, acetylene, hydrocarbon having a carbon number of 3 or 4, carbon monoxide, carbon dioxide, oxygen, and nitrogen, contained in an insulating oil used inside the oil-filled electrical apparatus; a step of analyzing a causative substance serving as a cause of generation of hydrogen in the insulating oil irrespective of whether or not the discharge has occurred; and a step of diagnosing whether or not the discharge has occurred based on an analysis result of the in-oil gases analyzing step and an analysis result of the step of analyzing the causative substance.

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: The present invention is a diagnosing method for oil-filled electrical equipment for diagnosing a degree of risk with regard to occurrence of abnormality due to copper sulfide generation in oil-filled electrical equipment, and the method includes a first step of detecting specific compounds contained in insulating oil in said oil-filled electrical equipment, a second step of evaluating a possibility of copper sulfide generation at a dangerous part leading to dielectric breakdown in said oil-filled electrical equipment in accordance with a detection result obtained in said first step, and a third step of diagnosing a degree of risk with regard to occurrence of abnormality in said oil-filled electrical equipment in accordance with an evaluation result obtained in said second step. Said specific compounds include dibenzyldisulfide and 2,6-di-t-butyl-p-cresol.

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: 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: 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.