An alternative test for evaluating transformer-oil deterioration using microwaves

This paper describes the sensitivity of microwaves to the chemical and physical specification variation of a power transformer-oil. The evaluation of a power transformer-oil deterioration by measuring the complex permittivity (complex dielectric constant) in the frequency range of X-band (8.5-10.5 GHz) and Ku-band (17.63-18.07 GHz)is investigated. A completely filled short-circuited waveguide technique is used to perform these measurements. It is shown that the microwave measurement of both the dielectric constant and the loss tangent can be successfully implemented for transformer-oil evaluation. Moreover, the low cost of the measurement set-up together with its simplicity and safety encourage us to recommend it for transformer-oil evaluation rather than the traditional high-voltage measurement techniques.