Analysis of deterioration by partial discharge of XLPE using GCMS and FTIR
Deterioration of polymeric dielectrics by partial discharge (PD) might occur at defects in an insulation layer. To elucidate the mechanism of deterioration by PD, measurements were conducted of the gas components produced during deterioration and the substances created on the surface of cross-linked polyethylene (XLPE) samples subjected to PD. Gas component measurements were performed using an experimental apparatus including GC-MS. Results of gas analyses showed that carbon dioxide (CO2) was produced when the XLPE sample is subjected to the PD in a N2+O2 gas atmosphere. The amount of generated CO2 was confirmed to increase concomitantly with the period of voltage application. The FTIR spectroscopic analysis of substances on the surface of deteriorated XLPE revealed carbonyl compounds on the surface of the deteriorated samples. The deterioration was suppressed when a phenolic antioxidant was added: 44-thiobis-3methyl-6tert butyl phenol. The process of deterioration by PD and the effect of the antioxidant on the deterioration by PD were also discussed.
Degradation of low-density polyethylene and cross-linked polyethylene by partial discharge
To study the degradation of low-density polyethylene (LDPE) and cross-linked polyethylene (XLPE) by partial discharge (PD), experiments were conducted in a nitrogen (N2) and (N2+O2) gas atmosphere. After being subjected to the PD, samples were examined using atomic force microscopy (AFM) and FTIR. The AFM images clearly revealed the creation of pits on the surface of degraded samples. A large difference in the pit pattern was observed between samples subjected to the PD in N2 and those subjected to the PD in (N2+O2). The FTIR spectra detected in samples subjected to the PD in (N2+O2) showed that carbonyl compounds were produced on the surface of degraded LDPE. Experiments were performed using an experimental system incorporating GC-MS to measure the gas components produced during degradation. Results of experiments showed that carbon dioxide (CO2) is produced when LDPE and XLPE are subjected to the PD in an oxygen-containing atmosphere. The amount of CO2 was found to increase concomitantly with the period of voltage application and oxygen concentration in the area where PD occurs. Based on experimental results, the processes of LDPE and XLPE degradation by PD were examined along with the antioxidant effect on degradation.
Venus: Evolution of the Upper Atmospheric Clouds
Abstract The large number of UV photographs taken by different observatories throughout the world are grouped for analysis at the IAU Planetary Photograph Center of Meudon Observatory. Three horizontal V, Y, or psi-shaped dark-hued cloud features are usually aligned along the equator and move 110 m s−1 westward in a planetary-wide rotation. The more intense and distinctly V-Shaped features last several weeks. The smaller scale cloud structures usually show significant changes after each successive rotation in 4 days around the planet. The average UV contrast is 32% but can fluctuate from disappearance to 37%. For periods of several years, the polar areas are sometimes covered by a white cloud. According to a set of photographs taken at Pic-du-Midi, this never occurred between 1962 and 1966 but has happened during 25% of the time for at least one pole since 1967, and only when the planet was in a given half of its orbit. These polar clouds are ephemeral and usually last several weeks or months; they evolve...