Study on the frequency domain dielectric spectroscopy of rotating machines insulation

To research the feasibility of applying of frequency domain dielectric spectroscopy method in the state diagnosis of generator insulation condition. Dielectric dissipation factor tan delta and relative dielectric constant of test specimens of generator stator bar of different aging degrees under multi-factor accelerated aging are tested by frequency domain spectroscopy (FDS) method. And the quantitative relationship between capacitance and routine test parameters of dielectric loss tangent tan delta are built. The result shows that the frequency domain spectral curve are affected by the aging degree of test bar significantly. The values of tan delta and epsilon increase with the aging degree, especially in low frequency stage. Tan delta at characteristic frequencies with capacitance C, epsilon at characteristic frequencies with tan delta at power frequency of different aging periods meet the index function relation. The research results are available for reference to apply FDS to noninvasive diagnosis of generator insulation aging status.