Moisture characteristic parameter extraction and quantitive analysis of oil-paper insulation based on new explanation model of FDS

Frequency domain spectroscopy (FDS) technique is regarded as an effective nondestructive diagnosis method of the insulating state for oil-paper insulation that has been widely researched worldwide. To quantify the dielectric's FDS character, a new explanation model of the dielectric loss with several parameters was first proposed after an in-depth study of the frequency-domain dielectric response theory. H-N function was used to represent the polarization loss while random free-energy barrier model was used to describe the conductance process. The fitted curve based on the proposed model was in good agreement with the measured curve in lab. Then, in order to develop a new method to evaluate the oil-paper insulating system's moisture content, the frequency domain spectroscopy of several oil-immersed paper samples with different moisture contents of 0.5%, 1%, 3% and 6% were measured at 40°C respectively. By analyzing the results, we find that the moisture content significantly affects only the conductance process. Therefore, the extracted characteristic parameter, namely the DC conductivity 00, which is closely related to the conductance process, can be used to quantitatively describe the moisture content of OIP.