A new method for measuring degradation level of insulating oil with temperature in microwave

The authors proposed a new method for measuring the degradation level of the transformer insulating oil through comparison of the relative permittivity of the reference oil with that of the degraded oil. The relative permittivity of the reference insulating oil was derived from Cole-Cole parameter with a temperature obtained by a curve fitting method and that of the degraded one was measured using the open-ended one port probe. From their comparison, degradation level can be measured.