Moisture solubility for differently conditioned transformer oils

It is important to monitor the moisture content of transformer oil in a tra nsformer. One parameter of particular interest is the moisture solubility o f transformer oil. It has been reported that transformer oils under differe nt conditions have different solubility. Measurements of solubility for fou r different types of conditioned oil are presented in this paper: fresh She ll Diala AX oil, lab-aged Shell Diala A oil, Texas Utility used transformer oil, and Ramapo Substation used transformer oil. To avoid the difficulty o f achieving full saturation, this paper proposes an alternative method of m easuring the moisture solubility in transformer oil using a relative humidi ty sensor. It utilizes the linearity between the relative humidity of the o il and the moisture content of the oil, to measure the solubility indirectl y. The measured results of fresh oil, lab-aged oil, and the Texas Utility o il are very close, and only Ramapo oil shows different sensor response char acteristics and solubility.