Investigation of Water Content in Power Transformer Oils through Ultrasonic Measurements

Transformers are one of the most important equipment found in electrical power systems. Thus, their status must be constantly monitored to avoid critical failures. The analysis of the dissolved gas (DGA) in the oil is one of the most important technique to detect short-circuits and partial discharges. However, this technique has a serious drawback to get the percentage of water absorbed by the oil, requiring other kind of predictive technique. In this context, this paper presents a technique to detect the water content in oils, which uses ultrasound measurement. The measurement results showed that after the frequency scan, the best results for determining the percentage of water in insulating oils were obtained at frequencies around 5MHz. These preliminary results revealed very promising.