J. A. Diego

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Several semiconducting (SC) shields used in medium voltage cables were analyzed. Besides, four experimental SC shields were prepared in the laboratory and were studied as well. PEA measurements were performed in LDPE films, in contact with the SC shields, with applied fields up to 140 MV/m. These measurements show the presence of a threshold electric field,(More)
Conductivity (Σ) in XLPE insulation of power cables annealed at 90°C at temperatures between 50 and 97°C has been measured. In all cases there is an initial increase in conductivity that develops a maximum and finally decreases for long annealing times. This maximum appears in the sample annealed 20 days when conductivity is measured at(More)
In order to study charge trapping and transport in polyimide, we have submitted samples of Kapton HN to corona charging and measured its surface potential decay with an electrostatic voltmeter. We propose a two terms mobility to explain the experimental data: a non dispersive contribution based on Toomer and Lewis model added to a dispersive process, which(More)
We have submitted samples of Kapton HN polyimide to corona charging and measured its potential decay with an electrostatic voltmeter. In order to analyze and explain the experimental data we propose a two terms mobility. We use a non-dispersive model based on hopping transport and introduce a dispersive term associated with the highly disordered structure(More)
The analysis by TSDC of a large variety of cables subjected to long annealing times, has resulted in spectra that sometimes show an oscillation of the current peak observed at 99°C. This process has been observed in some cables only and it is scarcely reproducible. We present an explanation of this behavior based on the formation of charge packets and some(More)
Space charge profiles in electrets of cable XLPE insulation have been determined by pulsed electroacustic method (PEA). A single positive peak close to the cathode, which decreases with annealing time, is observed. Typically, thermally stimulated depolarization currents (TSDC) of those electrets show heteropolar peaks initially. A new transient homopolar(More)
The glass transition in amorphous poly(ethylene terephthalate) is studied by thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC). The ability of TSDC to decompose a distributed relaxation, as the glass transition, into its elementary components is demonstrated. Two polarization techniques, windows polarization(More)
NdFeB melt spun amorphous or partially amorphous alloys of four compositions were prepared. Their crystallization kinetics induced by thermal treatment was studied by differential scanning calorimetry and scanning and transmission electron microscopy. Scanning electron microscopy demonstrated that heterogeneous nucleation occurs preferentially at the ribbon(More)
In the present work, a XLPE mid-voltage cable from General Cable co. has been studied by thermally stimulated depolarization currents. Systematic measurements have been carried out in order to compare the conductive processes in this cable with previous results. Depolarization current as a function of thermal annealing, thermal history, polarizing field and(More)
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