Patent ID: 9389196
Filing Date: 2016-07-12
CPC Classification: G01N

Claim Text:
1. A water-concentration detection device for detecting a water concentration of insulating gas filled in a gas-insulated device, the water-concentration detection device comprising: porous electrodes that are arranged to face each other in the insulating gas; a solid electrolyte membrane that is sandwiched between and fixedly attached to the electrodes, and has hydrogen-ion conductivity; a voltage application unit that applies an alternating-current voltage to the electrodes at a frequency of 325 Hz or a frequency equal to or lower than 10 Hz; an impedance measurement unit that measures an alternating-current impedance between the electrodes in a state in which the alternating-current voltage is applied to the electrodes; a logarithmic amplifier that logarithmically converts the alternating-current impedance measured by the impedance measurement unit and outputs a conversion result; a water-concentration detection unit that detects a water concentration of the insulating gas based on the alternating-current impedance outputted from the logarithmic amplifier; a gas chamber in which air in an atmospheric atmosphere is encapsulated before starting measuring the water concentration, in which the insulating gas introduced from the gas-insulated device is encapsulated at a time of starting measuring the water concentration, and inside which the electrodes are arranged to face each other; and a storage unit that stores impedance-time change curves for a plurality of different water concentrations, respectively, each of the impedance-time change curves representing a time change in the alternating-current impedance according to the water concentration of the insulating gas, wherein the water-concentration detection unit compares at least a behavior of a measured value of the alternating-current impedance at one or more time points or of the measured value of the alternating-current impedance during a certain period with the impedance-time change curves stored in the storage unit before the measured value of the alternating-current impedance obtained by the impedance measurement unit converges, identifies an impedance-time change curve that indicates a same behavior as the behavior, and outputs a water concentration corresponding to the identified impedance-time change curve as a detected value.