Discrete and continuous moisture-in-oil measurements in electrical apparatus

Water-in-oil instruments have been developed for field use, both as a portable devices and for continuous on-line measurements and are trademarked as DOMINOs. The unit responds to changes in relative saturation of water in oil that can be related to the water content in paper. As the solubility of water in oil can increase with very aged oils, the water content as a concentration can overestimate the wetness of the solid insulation when using equilibrium curves. Using an instrument which responds to relative saturation of water in oil provides a means to estimate moisture in paper even when the oil has become very aged. The concentration of water in various dielectric liquids can be calculated and displayed automatically by selecting the correct algorithm developed with Karl Fischer coulometric titrations.