M. Talaat

A numerical model of electrical tree growth in solid insulation

A new model for investigating the electrical tree growth in solid insulation using a hyperbolic needle-to-plane gap is presented. The needle is embedded in the insulation medium. Classification of tree shape depends on the electric field value is presented. Then, accurate computation of the electric field is a pre-requisite for calculating electrical tree growth. The electric field distribution is obtained from Laplaces equation by treating the tree structure as an extension of the stressed electrode i.e., conducting medium. The electric field is redistributed during each growth of the electrical tree. This is achieved by using the charge simulation method. The charge at the needle surface is simulated by a group of ring charges. To determine the appropriate arrangement of simulating ring charges inside the needle, a genetic algorithm is used. A number of series finite line charge is used for simulating the charge over each branch and sub-branch during the treeing progress. The presented model for simulating electrical tree growth is a three dimensional field problem. The used needle tip radius was 3 ¿m while the gap spacing varied from 0.3 to 15 mm. The results have been assessed through comparison with available analytical and experimental data.

A Simulation Model for Electrical Tree in Solid Insulation Using CSM Coupled with GAs

A new model for investigating the growth of electrical tree in solid insulation using hyperbolic needle-to-plane gaps is used. Accurate computation of electric field is a pre-requisite for calculating the growth of electrical tree. The electric field distribution is obtained from Laplaces equation by treating the tree structure as an extension of the stressed electrode i.e. conducting medium. The electric field is redistributed during each growth of the electrical tree. This is achieved by using charge simulation method coupled with genetic algorithms. Series of vertical and inclined line charges are used for simulating the tree, for these inclined line charges, a coordinate transformation is performed. Then, the electric field is calculated in the original coordinate system. The used needle tip radius is 3 mum while the gap spacing varies from 0.3 to 15 mm. The results have been assessed through comparison with experimental data.

Types of electrical trees in solid insulation under electrical and mechanical energy basis

The shape of electrical trees is critical in determining the life of electrical insulation subject to this type of degradation. This paper identifies a physical basis for determining tree shape. A quantitative physical model for propagation of electrical tree structures in polymeric insulation is presented. In the present model the propagation of trees arises from the formation of electrodamage that precedes and surrounds the tree tip during the tree propagation process. A kinetic model for the electrical tree structures in solid polymeric insulation is developed, that allows for combined electrical and mechanical stresses. Also present an energy balance analysis during the tree growth process, and present results which show that the proposed model can give predicted tree shape type which in a good agreement with the experimental data of the tree growth subjected to a combined electrical and mechanical stress.

Use of finite element method for the numerical analysis of eddy current brake

Eddy current brake is developed to take the superior advantages of fast anti-lock braking to the conventional hydraulic brake systems. Magnetic and electric field generated by these eddy currents suppress the disturbing field. The electric and magnetic field distribution are obtained from Neumanns and Maxwells equations respectively. The presented model for simulating electric and magnetic field are a three dimensional field problem. Braking torque analysis is investigated by using an approximate theoretical model. A good agreement is found between the numerical and experimental. Since the eddy-current problem usually depends on the geometry of the moving conductive sheet and the pole shape, there is no general method for solving it analytically. This paper presents a method for analysis of the eddy current in the special case of a rotating disc in a time-variant field by using a time-domain Finite Element Method from t = 0 to the brake time. Finite Element Methods is adopted for this work using COMSOL Multiphysics model.

Charge simulation modeling for calculation of electrically induced human body currents

A new method is described for investigating the distribution of the electric field in the human body subjected to high voltage. The electric field distribution is obtained from Laplaces equation. This method of analysis is based on the charge simulation method coupled with genetic algorithms to determine the appropriate arrangement, optimum number and radius of simulating ring charges inside the human body. The presented model for simulating electrical field is a three dimensional field problem. The results have been assessed through comparison with the magnitude of total induced charge and its distribution over the body surface, as estimated in other experimental and computational work. The accuracy of the simulation is satisfied for the potential error, (not more than 1 %), and the field deviation angle, (not more than 5 degree) over the human body.

Influence of transverse electric fields on electrical tree initiation in solid insulation

The study of tree growth in solid insulation is important to reveal many aspects in order to develop the way of its suppression. The additives are one of the main aims to do this also good manufacture of solid insulation material without impurities are also another way. This paper introduces new method to study the influence of transverse electric field on electrical tree initiation in solid insulation. A new model is introduced for investigating the effect of transverse fields on the morphology of electrical tree by using needle-to-plane gap for tree initiation and plane-to-plane gap for field transverse. Only the needle is embedded in the insulation medium. Then, accurate computation of the electric field is a pre-requisite for calculating the electric field distribution by using the finite element methods.

A hybrid model of an artificial neural network with thermodynamic model for system diagnosis of electrical power plant gas turbine

Abstract In this paper, the diagnosis system of power plant gas turbine has been developed to detect the deterioration of engine performance. This system can be analyzed the gas path measurement to predict the deterioration of engine main component by using artificial neural network. The deterioration performance data of gas turbine was generated by using the thermodynamic model. So, the artificial neural network model was built to predict the deteriorated characteristics of gas turbine. Thermodynamic model was used to simulate gas turbine performance as well as the deterioration of engine components (compressor, combustion chamber and turbine) which were represented by changing component characteristic parameters (efficiency and flow capacity). On one hand, the probability of these deteriorated components was simulated to generate deteriorated data (measurement parameters and deterioration degree of each component). On the other hand, the neural network was trained with deterioration data and the best structure of neural network (number of hidden layers, number of neurons in hidden layer and transfer function) was selected based on the minimum value of the mean square error. The different deterioration data (testing data) was generated in thermodynamic model to test the effectiveness of the neural network. The comparison between the mean square error value of single and multi-neural network output parameters at training and testing data were achieved. In final, the testing with the real engine data were achieved.

Electrical Characteristics of Nonthermal Gliding Arc Discharge Reactor in Argon and Nitrogen Gases

Gliding arc discharge (GAD) has the properties of both thermal and nonthermal plasma conditions. GAD plasma in the atmospheric pressure with argon/nitrogen and its characteristics are described. Some experimental results about alternating current gliding arc plasma generator have been obtained. It seems that the current density strongly depends on the gas type, and increased with increasing discharge current and gas flow rate. In addition, the discharge current of GAD in nitrogen gas (N2) is greater than one in argon gas (Ar) because of N2 needs more breakdown voltage than Ar. The intensity of GAD increased with increasing the gas flow rate. The oscillograms of discharge current in each case of Ar and N2 were obtained. The electron temperatures of Ar and N2 plasma were calculated to be 22 800 and 8400 K, respectively. The characteristics of both Ar and N2 gases in atmospheric pressure, such as current density, electron density with flow rates (5, 10, 20, and 40) standard cubic foot per hour, were investigated and all experimental results were classified. An experimental study was carried out through using of GAD device for medical treatment by exposing three human blood samples of leukemia to the nonthermal GAD plasma for different periods.

A numerical model of investigating the electric field in dielectric liquid

The initial filamentary streamers in liquid dielectrics drastically changes by the tip curvature of the electrode and the applied voltage. In this paper to get the non uniform field a sphere-to-plane electrodes configuration is used. Also, an immersed air bubble adjacent to the sphere electrode is presented, to obtain the sharp tip, after the air bubble compressed against the sphere electrode i.e., sharp conducting protrusion tip, which considered as a source of high non-uniform field and streamer initiation. A simulation model for field distribution in the dielectric medium is presented by using Finite Element Method. An experimental technique was used to investigate the accuracy of the field simulation. Also an analytical equation for field calculation was used to investigate the percentage field error.

Screening of renal dysfunction among Burkitt lymphoma survivors by novel markers

ABSTRACT Background: Burkitt lymphoma (BL) represents the most common pathological type of non-Hodgkin lymphoma in our region. Recently, high success rates have been achieved in BL treatment. Little is known about long-term renal dysfunction in this vulnerable group. In the present study, we tried to detect early chronic kidney diseases (CKD) among BL survivors by using novel screening modalities. Patients and methods: we investigated 53 children (aged 10 ± 2.8 years, 34 boys) who successfully treated for Burkitt lymphoma, based on LMB96 protocol, as “patient group” and 30 children as control. All eligible participants were subjected to history taking, physical assessment, and routine laboratory investigations including urine analysis, serum creatinine. Estimated glomerular filtration rates using new Schwartz formula (GFRCKD) were calculated and chronic kidney disease prevalence was diagnosed accordingly. Also, serum Cystatin-C (Cys-C) and neutrophil-gelatinase-associated Lipocalin (NGAL) were determined as novel markers aiming at early and accurate detection of CKD in BL survivors. Results: After 18.3 ± 5.2 months of BL cytotoxic therapy completion, almost one fifth of asymptomatic BL survivors showed evidence of subclinical CKD when estimated GFRCKD (16.9%), serum Cystatin-C (15%) and serum neutrophil-gelatinase-associated Lipocalin (18.8%) were used for kidney function monitoring. This prevalence was four to fivefolds higher than that detected by routine serum creatinine screening (3.7%). Significant persistent albuminuria was diagnosed at 4/53 (7.5.3%) of BL survivors and asymptomatic hypertension was reported in 1/53 (1.9%) of them compared to none of the controls. Positive correlation could be displayed between serum Cys-C and serum NGAL. Conversely, negative correlations between both of them and estimated GFRCKD were documented. Conclusion: Novel modalities such new Schwartz formula (GFRCKD) estimation, serum Cys-C, and serum NGAL assessment should be incorporated in the routine follow-up screening for CKD among BL survivors for accurate diagnosis of such detrimental morbidity.