A New Method for Assessment Condition of Oil-paper Insulation Based on The Characteristics of Frequency Domain Spectroscopy

The Frequency Domain spectroscopy is a nondestructive electric diagnosis. It's very suitable for transformer oil-paper insulation condition of field detection, the actual development of the internal oil paper insulation status can be reflected accurately, especially in the low frequency and the ultra-low frequency. Because of the frequency domain dielectric spectroscopy at low frequency measurement requires a very long time, and it's vulnerable to environment. In order to ensure the accuracy of the insulating condition, the FDS needs to be better applied to the nondestructive quantitative assessment in transformer oil paper insulation system. The aged ample of oi-paper insulation is first prepared, and then this sample tested at thermostat 30 degrees C in the FDS. To obtain the insulation information contained in dielectric loss factor (t(an delta)) as more as possible, the integral of dielectric loss factors (S-tan delta) in the characteristics frequency ranges are introduced as characteristics parameters for assessing insulation condition. Due to the FDS requires a very long time in characteristics frequency ranges, and it's vulnerable to environmental factors, In this paper, the method of predicting S-tan delta in low frequency FDS based on the parameter identification of the X-Y equivalent circuit is put forward. then, the measured data and calculated data are compared, in order to confirm the availability of this method.