A Study for Examining Dissipation Factors of Various Insulations and Test Transformers in the Wide Range of Frequency

Abstract

Modern technology and developments in signal acquisition and analysis techniques have provided new tools for insulation diagnostics. There is still today a need for improved non-destructive diagnostic methods for electrical equipment. Measurements of capacitance and loss are classical methods and more and more attention is paid to measurements over a wide frequency range. Particularly low frequency measurements seem to yield much information about the state of the insulation. Tan delta, also called loss angle or dissipation factor testing, is a diagnostic method of testing insulations to determine the quality of the insulation. In this paper, dissipation factor and capacitance of various dielectric materials at variable frequency are studied. When measured at a fixed frequency only, the property changes in the different materials cannot be discerned. In this paper, results show that of measurements done on the insulation between different various four types dielectrics materials. And finally these results are compared each other to select the best dielectrics. Acetate is the best dielectric material among our experimented materials.  Moreover, dissipation factor measurement at very low frequency 0.1 Hz is one of the diagnostic methods for condition assessment of isolation systems of power transformers. This paper gives a background to frequency domain spectroscopy, correlation between dissipation factor and aging condition of insulation. 0.1 Hz measurements in combination with Fast Fourier Transform theory modeling can be used to calculate dissipation factor and harmonic analysis. Among the electrical methods, dielectric spectroscopy measurements in frequency (0.1 mHz - 1 kHz) domain have gained the reputation of allowing to estimate moisture content in paper and pressboard insulation. Ill. 10, bibl. 17, tabl. 1 (in English; abstracts in English and Lithuanian).

DOI: http://dx.doi.org/10.5755/j01.eee.121.5.1647