An ultrasonic evaluation for degradation of insulating oil using fuzzy inference

Periodic inspection for degradation of insulating oil in transformers requires for preventing outage. However, conventional methods were not suitable for that, due to a large size of the measurement system and requirement of sampling. This study aims to develop the ultrasonic evaluation system satisfying these requirements aided by fuzzy inference. The system evaluates degradation, and it estimates kinetic viscosity. In the experiment, we applied our method into six kinds of insulating oils. As a result, correlation coefficient between our estimation and viscometer were over 0.92. Thus, our method correctly determines degradation of insulating oil.