Condition evaluation of oil-paper insulation based on dielectric spectroscopy

New techniques are necessitated to be introduced for the diagnosis of large oil-immersed power equipments for the disadvantages of traditional methods such as not very good operability and accuracy. The Frequency Domain dielectric Spectroscopy (FDS) for the diagnosis of oil-paper insulation is presented in this paper. Specimens and on-site equipments under different conditions are measured using FDS technique. The tan ¿-f curve shifts upwards as the moisture content increases, and the trends are particularly evident in the high and low frequency range. Aging will also result in the increase of dissipation factor due to the byproducts such as water and carboxylic acid. Besides, Temperature has great effect on the dielectric response of the insulation and the tan ¿-f curve moves towards high frequency range at elevated temperature. Research shows that the dielectric response in frequency domain can reflect the condition of the insulation and it is hopeful to be considered as an auxiliary method for the diagnosis of oil-paper insulation.