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.
Deterioration by partial discharges of polyethylene in oxygen containing gas atmosphere
To study the deterioration of LDPE by PD (partial discharge), experiments were conducted using the CIGRE II type electrode in N/sub 2/ (pure nitrogen) and (N/sub 2/+O/sub 2/) gas atmosphere. After being subjected to the PD, specimens were examined by AFM (Atomic Force Microscope). The AFM image clearly revealed the creation of pits on the surface of LDPE specimen. A big difference in the pattern of pits was observed between the specimen subjected to the PD in N/sub 2/ and to the PD in (N2+O2). The FTIR spectra detected in the specimen subjected to the PD in (N/sub 2/+O/sub 2/) showed that carbonyl compounds were produced on the surface of the deteriorated LDPE. The oxidative degradation is presumed to be the dominant process of the deterioration of LDPE by PD in oxygen containing atmosphere.
Assessment of dielectric degradation by ultrawide-band PD detection
Partial discharges (PD) and the way they affect insulation quality has for decades been a rewarding subject for many researchers. There are two topics that are of particular interest to the workers in the field of PD. One is the impact of a wide variety of statistical tools on the interpretation of discharge data obtained with standard PD detection apparatus according to IEC270. The other topic is the study of discharge-induced degradation processes by looking into the physics of the discharge process. This can be done by different means but a valuable technique, at least for the laboratory, is the use of ultra-wide band PD detection systems. This paper is a mix of a short review on the progression in the understanding of deterioration by internal PD obtained with such systems and of results recently obtained by the author. >