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: 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 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 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.