The effect of temperature and field strength on the resistivity of transformer oil
Safety operation of total ultra-HVDC transmission system could be directly affected by the operation reliability of converter transformer which is one of the most important equipments in the system. The transformer oil is the main liquid dielectric medium in the converter transformer. Thus, it is significant to study the dielectric properties of the transformer oil. In this paper, the dc resistivity of transformer oil under different conditions has been systematically investigated, and then the temperature and field strength were the test parameter variables. The variation range of temperature was 25~80°C, and under each temperature point the field strength changed ranging from 0.5V/mm to 10kV/mm. Meanwhile, 15 min is selected as the duration of testing resistivity. In this paper, the authors obtained the systematical data points and analysis curves of resistivity under different temperature and field strength, and obtained a empirical equation which describe the relationship between resistivity, temperature and field strength. It enhanced the understanding of the resistivity for transformer oil and provided the theoretical and test basis to expand the engineering application of this transformer oil.
Measurement of Electrical Insulating Oil Oxidation by Evaluating the UV Fluorescence Emission Ratio
In this work, a new fluorescence emission measurement technology was introduced and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate it for the oil oxidation measurement of electrical insulating oil. The oxidation characteristics of insulating oil were found to be fairly represented by the titration method and IR spectroscopy, and the results are comparable to a change in the fluorescence emission ratio that is defined as the shift in fluorescence intensity in the measured wavelength range. The result also shows that by the measurement of fluorescence emission ratio, it is possible to detect the oxidation of oil relatively earlier than by other methods. This study suggests that the developed technology can provide sufficient information for evaluating the insulating oil quality, and that the developed FER sensor can be used as an effective condition monitoring device of electrical insulating oil oxidation.
Pioneer 10 Observations of the Ultraviolet Glow in the Vicinity of Jupiter
A two-channel ultraviolet photometer aboard Pioneer 10 has made several observations of the ultraviolet glow in the wavelength range from 170 to 1400 angstroms in the vicinity of Jupiter. Preliminary results indicate a Jovian hydrogen (1216 angstrom) glow with a brightness of about 1000 rayleighs and a helium (584 angstrom) glow with a brightness of about 10 to 20 rayleighs. In addition, Jupiter appears to have an extensive hydrogen torus surrounding it in the orbital plane of Io. The mean diameter of the torus is about equal to the diameter of the orbit of Io. Several observations of the Galilean satellites have also occurred but only a rather striking Io observation has been analyzed to date. If the observed Io glow is predominantly that of Lyman-α, the surface brightness is about 10,000 rayleighs.