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.
Modelling of aged cavities for partial discharge in power cable insulation
In this study, the ageing process of cavities in solid insulation of power cables is divided into three stages, and for each stage a circuit model is proposed. Each of these circuit models preserves the basic characteristics of the cavity under the circumstances of the corresponding stage and provides the expected behaviour of generated partial discharge (PD) pulses. This set of models simulate cavity wall effects, the non-uniformity of internal electrical field and charge deployed on the wall surfaces with considering the existence of electronegative gases according to the requirements of the three defined ageing stages. Finally, the simulation results, in the forms of phase resolved PD patterns are presented showing good agreement with the published experimental measurements drawn from accelerated ageing process setups.
A study on the deterioration of LDPE and epoxy insulation by partial discharge
Experiments were conducted to investigate the deterioration of LDPE (low density polyethylene) and epoxy insulation by partial discharge (PD) in open air and in nitrogen atmosphere. The specimens subjected to the PD were examined using AFM (Atomic Force Microscopy) and FTIR. It was discovered through the AFM observation that irregularities were generated in the deteriorated region of the insulation. The magnitude of the irregularities after 200 hours of aging was estimated to be 600-900 nanometers. From analysis of the FTIR spectra, carbonyl groups and amides were found to be generated in the LDPE specimen subjected to PD in air, whereas in specimens subjected to PD in nitrogen, amines were generated. The deterioration process of LDPE by PD was discussed in relation to these FTIR results.