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Electrical Engineering should face the challenge of developing a mature approach in insulation design. Modeling charge transport and linking charge dynamics with dissipative processes responsible for electrical ageing are crucial as regards this objective. Such an approach is exemplified here for polyethylene-based materials by introducing two models describing bipolar Space Charge Limited Current...
The topic of polymer nanocomposites remains an active area of research in terms of potential applications for dielectric materials. Although more than a decade has passed since these systems were first considered as dielectric materials, the precise effects of incorporating nanofillers into different polymers are yet to be confirmed. This paper reports on an investigation into the AC and DC breakdown...
Published work, including mechanistic studies, of molecular dielectrics, involving molecular additives, co-polymers, and miscible and immiscible polymer blends, in the 60s, 70s, and 80s, led to major improvements in breakdown and physical and mechanical properties of polymer-based insulation systems. Many new products were the result of these studies, resulting in improved designs and performance...
The composites of PVDF-HFP with various low concentrations (0–0.08 wt%) of single-walled carbon nanotubes (SWNTs) were prepared via solution casting and melt pressing, and were investigated for their enhanced dielectric and piezoelectric properties. It is found that the piezoelectric response increases by a factor of 1.5–3 over the pristine material for a 0.02 wt. % SWNT concentration in the polymer...
For the electric field control, relaxation and optimization in a solid insulator of electric power apparatus, we have been investigating functionally graded materials (FGM) with spatial distribution of dielectric permittivity (εr). We have so far developed the fabrication and simulation techniques of FGM with a cylindrical shape for post-type solid insulator of gas insulated switchgears (GIS). In...
We compute the ferroelectric properties of barium titanate on a microscopic scale by calculating the local electric fields. In contrast to macroscopic or medium field calculations the method of local fields considers all electric fields within the sample taking account of the electrodes by the method of images. In our model, the barium and the oxygen ions are assumed to be fixed point charges with...
Graphene oxide filled silicone rubber nanocomposites were found to possess a large nonlinear coefficient of electrical conductivity, smaller low field conductivity than that of the neat polymer and an increase in the dielectric constant over that of the polymer matrix with a very small increase in the dielectric loss. These electrical and dielectric properties make graphene oxide/silicone nanocomposites...
The electric stress created on an insulation system depends on the type of applied voltage stimulus. Real insulating systems often contain defects of different types e.g. cavities, voids within dielectric materials or at boundaries between the dielectric and the conductor which are sources of PD at large enough electric field. These defects can arise in the technological manufacturing processes or...
Gas filled cavities in solid insulation can form during production and are likely to have initial spherical or ellipsoidal geometry; as degradation takes place the shape will distort. Due to the difficulties of producing spherical and ellipsoidal cavity shapes most previous partial discharge (PD) measurements, in polymeric insulations, have used a layered polymer sandwich approach to create flat cylindrical...
Partial discharge (PD) occurring in gas void introduced during the manufacturing process of insulating constructions forms a serious threat to the life of insulation, hence it's necessary to clarify its mechanism. In our paper, the surface charge measurement system based on Pockels effect was constructed to detect the residual surface charge distribution after PD occurred in a cylindrical void enveloped...
Partial discharge (PD) analysis, based on measurement data, assumes that PD signals propagate inside a transformer winding from the PD source to the measurement points. In this paper, signals are injected via an external connection into specific points along the winding of a transformer experimental model. The measurement data obtained using radio frequency current transducers (RFCT) connected to...
The detection of Ultra high frequency (UHF) Electromagnetic wave(EM) induced by partial discharge (PD) has been applied in power transformer to find insulation defects due to such features as interference-free and abundant discharge information. However, the propagation mechanism of UHF EM in power transformer has not been detailed investigated, and there are few effective results to instruct the...
The aim of this paper is to describe the study of the Partial Discharge (PD) characteristics of mineral oil obtained from Partial Discharge Inception Voltage(PDIV) testing using the needle — plane and needle — sphere electrode configurations. This paper represents the experimental investigation of the PD characteristics of the mineral oil, Nynas 4000x, with the water content not more than 10 ppm at...
The pre-breakdown phenomena, have been studied with the aim to further understand the use of liquid nitrogen as a part of insulation system in High Temperature Superconducting (HTS) devices. Previous studies have shown that streamer discharges in liquid dielectrics can appear in the form of pulse trains which are thought to be the results of density-change channels expanding and collapsing. This behavior...
In the inverter-fed motor, the surge voltages with fast rise time and high voltage peak may cause partial discharge (PD) which potentially damages the electrical insulation system. Offline tests with an impulse generator are executed under the IEC technical specifications of TS60034–18–41 (2006) and TS61934 (2011) for insulation systems of low-voltage motors fed from inverters, which are required...
Partial discharge (PD) activity within a void in a dielectric material is influenced by many factors. One of the factors is the applied voltage waveform on the material. In this paper, a two-dimensional (2D) model of a cylindrical void in polyethylene layers has been developed using finite element analysis (FEA) software. The model was used to simulate PD activity in the void under square waveform...
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