The effect of surface treatment of silica nanoparticles on the breakdown strength of mineral oil

In previous work, the results of AC breakdown tests showed that unmodified silica nanoparticles improve the breakdown strength of mineral oil based nanofluids, especially at a relatively high humidity level of around 25 ppm. It was proposed that, since the hydrophilic surface of unmodified silica nanoparticles can absorb water, this would lead to a reduction of free moisture in the bulk of the oil, which has a strong influence on the breakdown strength. In the present study this proposition is verified, by comparing the breakdown strength of two mineral oil based nanofluids: a reference with unmodified silica nanofluid and a nanofluid with Z-6011 modified silica. The silane coupling agent Z-6011 turns the surface of silica nanoparticles hydrophobic, thus preventing water adsorption

An investigation into the dynamics of partial discharge propagation in mineral oil based nanofluids

Recent studies present a model which assumes that conductive nanoparticles can reduce the speed of the positive streamer propagation in mineral oil due to electron trapping at the particle surface. Time resolved partial discharge measurements can be used to evaluate the discharge dynamics and to verify this hypothesis. A special measurement setup was built to enable the recording of the discharge dynamics. In this study, the effect of nanoparticles with different conductivities on the discharge dynamics of mineral oil is investigated. The time resolved current shapes of partial discharges in nanofluids and mineral oil are compared. To understand the effect of the conductivity of the nanoparticles on the partial discharge dynamics of mineral oil, nanoparticles with two different conductivities are synthesized with mineral oil. The two types of nanoparticles are silica and fullerene. The host fluid used in this study is Shell DialaS3ZXIG mineral oil

Space charge analysis of epoxy boron nanocomposites and the importance of dispersion techniques

The present research work analyzes the space charge (S.C.) behavior and correlated dynamics in epoxy based nano- composites (NC) with hexagonal boron nitride (hBN) nano- particles. The importance of adopting an effective particle dispersion technique for producing such nano-composites is also experimentally validated. Three different dispersion techniques are contrasted in terms of the corresponding space charge behavior exhibited, and the interplay between increasing filler content and dispersion techniques is investigated and reported. It is observed that an effective particle dispersion technique results in a homogeneous distribution of nano- particles in the polymeric matrix, which in turn gives rise to evenly distributed trap sites and affects the local mobility of charge carriers, effectively restraining them. More significantly, since most of the developed trap-sites are located close to/in the interfacial zone between the injecting electrode and nano-composite specimen, an initial, reasonably homogeneous distribution of nano-particles at relatively lower loading (vol. %) is just as efficient in restricting bulk space charge accumulation as higher loaded nano-composite specimens – proving the importance of adopting an effective particle dispersion technique. Achieving lower levels of bulk space charge accumulation (as demonstrated in this work) results in smaller internal electric field distortion and stress in insulation material, thus having the beneficial effect of prolonging operational life-time and increased reliability

Space charge analysis of epoxy boron nanocomposites and the importance of dispersion techniques

The present research work analyzes the space charge\u3cbr/\u3e(S.C.) behavior and correlated dynamics in epoxy based nano-\u3cbr/\u3ecomposites (NC) with hexagonal boron nitride (hBN) nano- particles.\u3cbr/\u3eThe importance of adopting an effective particle dispersion technique\u3cbr/\u3efor producing such nano-composites is also experimentally validated.\u3cbr/\u3eThree different dispersion techniques are contrasted in terms of the\u3cbr/\u3ecorresponding space charge behavior exhibited, and the interplay\u3cbr/\u3ebetween increasing filler content and dispersion techniques is\u3cbr/\u3einvestigated and reported. It is observed that an effective particle\u3cbr/\u3edispersion technique results in a homogeneous distribution of nano-\u3cbr/\u3eparticles in the polymeric matrix, which in turn gives rise to evenly\u3cbr/\u3edistributed trap sites and affects the local mobility of charge carriers,\u3cbr/\u3eeffectively restraining them. More significantly, since most of the\u3cbr/\u3edeveloped trap-sites are located close to/in the interfacial zone\u3cbr/\u3ebetween the injecting electrode and nano-composite specimen, an\u3cbr/\u3einitial, reasonably homogeneous distribution of nano-particles at\u3cbr/\u3erelatively lower loading (vol. %) is just as efficient in restricting bulk\u3cbr/\u3espace charge accumulation as higher loaded nano-composite\u3cbr/\u3especimens – proving the importance of adopting an effective particle\u3cbr/\u3edispersion technique. Achieving lower levels of bulk space charge\u3cbr/\u3eaccumulation (as demonstrated in this work) results in smaller\u3cbr/\u3einternal electric field distortion and stress in insulation material, thus\u3cbr/\u3ehaving the beneficial effect of prolonging operational life-time and\u3cbr/\u3eincreased reliability

The Electrical Breakdown Strength of Pre-stretched Elastomers, with and without Sample Volume Conservation

n practice, the electrical breakdown strength of dielectric electroactive polymers (DEAPs) determines the upper limit for transduction. During DEAP actuation, the thickness of the elastomer decreases, and thus the electrical field increases and the breakdown process is determined by a coupled electro-mechanical failure mechanism. A thorough understanding of the mechanisms behind the electro-mechanical breakdown process is required for developing reliable transducers. In this study, two experimental configurations were used to determine the stretch dependence of the electrical breakdown strength of polydimethylsiloxane (PDMS) elastomers. Breakdown strength was determined for samples with and without volume conservation and was found to depend strongly on the stretch ratio and the thickness of the samples. PDMS elastomers are shown to increase breakdown strength by a factor of ~3 when sample thickness decreases from 120 to 30 μm, while the biaxial pre-stretching (λ = 2) of samples leads similarly to an increase in breakdown strength by a factor of ~2.5