Partial Discharge Tests Using CIGRE Method II Upon Nanocomposite Epoxy Resins

Nanocomposite polymers are becoming a new family of dielectric materials with promising insulating properties. In order to apply this technology to insulation systems, a study about the material longterm endurance (life) is needed. In this paper results from comparative life tests performed upon base and nanostructured epoxy resin samples are presented. The nanofiller is a organophillic-modified ultra-clean montmorillonite. Specimens were subjected to ageing under surface discharge phenomena using a standard electrode configuration, that is the CIGRE method II. Life data and partial discharge phase resolved patterns, acquired during time under stress, are presented and commented, in order t…

Electrical Aging Tests on Enameled Wire Exposed to Gamma Irradiation

Electrical tree growth in EVA-layered silicate nanocomposites

This work deals with the growth of electrical treeing in different EVA-layered silicate nanostructured compounds. The experimental activity evidenced that the intercalated nanocomposites have longer lifetimes than pure EVA under the same constant AC stress conditions. A monitoring of the tree growth morphology allowed to evidence very interesting features of the intercalated nano-compounds showing a barrier effect to the treeing path. A preliminary investigation on the possible arrangement of the filler particles inside the matrix was also carried out.

Microscopic and nanoscopic EVA composite investigation: Electrical properties and effect of purification treatment

This work presents preliminary results of an investigation aiming at characterization of nanocomposite insulating materials. Focus is made on size and technological process effects, i.e. dependence of electrical properties on filler size, on polymer-nanofiller interaction (e.g. intercalation or exfoliation) and, in particular, on chemical purification procedures. The materials under investigation are (EVA) copolymer filled by layered micro and nanosized silicates consisting of montmorillonite and fluorohectorite, that is, natural and synthetic clays. Microstructural characterization, using transmission electron microscopy, TEM, and wide-angle X-ray spectroscopy, WAXS, and electrical measure…

Electric strength, space charge and surface discharge characterization of nanostructured epoxy-silicate insulating materials

A set of surface discharge ageing procedures, space charge observations and dielectric strength measurements has been implemented on a type of insulating nanofilled epoxy-resin (nanostructured by compatibilised synthetic layered silicates) and on its non-filled base resin. Promising improvements in the electrical behaviour of the nanofilled epoxy, particularly as concerns surface discharge endurance, were detected. Regarding space charge, it was found that its accumulation rate as a function of ageing time is lower for the nanostructured resin. Finally, the nanofilled material evidenced a highly homogeneous behaviour of the dielectric strength data distribution.

Electrical treeing in EVA-bohemite and EVA-montmorillonite nanocomposites

The present experimental work focuses on the growth of electrical treeing inside different Ethylene-vinyl acetate (EVA) nanocomposites containing Bohemite (an aluminum oxide hydroxide) and Montmorillonite (a phyllosilicate clay mineral) nanoparticles. Bohemite and Montmorillonite particles have different aspect ratios: the first one has a nanometric cube-like symmetry, while the latter has a typical layered structure. The results evidence that the growth of the electrical treeing inside the original polymer can be altered significantly by the dispersion of inorganic nanoparticles.

Dielectric spectroscopy analysis of EVA-silicate nanocomposite insulating materials

Nanocomposite materials show promising results for applications as electrical insulation. Among several materials presently under investigation, previous works indicate that polypropylene and ethylene-vinilacetate filled by nanosilicates present lower content of space charge and higher electric strength. However, efforts are needed to explain nanocomposite behaviour and characterize their electrical, thermal and mechanical properties. In this paper, the results of broad-band dielectric spectroscopy performed on ethylene-vinylacetate copolymer filled by layered micro and nanosized silicates are reported. The nanofillers consist of montmorillonite and fluorohectorite, that is, natural and syn…