A sensing system for degradation diagnosis of oil-filled transformers

Under normal operating conditions the insulation of power transformers undergoes gradual deterioration that produces various degradation by-products. Properties of the insulation, such as degree of paper polymerization, also change. To evaluate the degradation state of the insulation the detection and analysis of the degradation by-products have been widely performed. However, the diagnostic techniques presently used are rather complicated and time consuming. This paper describes a new diagnostic technique for oil-filled transformers based on a semiconductor-type sensor. The technique can be used for in-situ measurements in the field, requires very small amounts of oil for analysis and allows for rapid test data analysis. The detection of ketonic by-products with the newly developed sensor was found to be very useful as a diagnostic tool