Power transformer protection using S-transform with complex window and pattern recognition approach

A new approach for power transformer protection using S-transform with complex window to distinguish between inrush current and internal fault is presented. The S-transform with complex window is used to extract patterns of transient current samples during inrush and faults. S-transform is a very powerful tool for non-stationary signal analysis giving the information of transient currents both in time and in frequency domains. The spectral energy is calculated for inrush and internal faults and an energy index is found out to distinguish between inrush magnetising current and internal faults. The simulation results and the results obtained using real-time data from a transformer in the laboratory environment indicate the robustness of the proposed technique     

Complex impedance analysis of NaLaTiO4 electroceramics

A layered perovskite type ceramic oxide, NaLaTiO₄, has been prepared by a standard high temperature solid-state reaction route. Material formation has been confirmed by x-ray diffraction (XRD) studies. Complex impedance analysis on this system has been carried out, to investigate its electrical properties in details. The impedance analysis results have indicated the electrical conduction process to be governed by the contribution of both the grain (bulk) and grain boundaries above a temperature of 350 ^∘C with typical negative temperature coefficient of resistance (NTCR) type behaviour like that of a semiconductor. The d. c. conductivity of the material as evaluated from the impedance analysis has been observed to be of the order of ∼ 10⁻⁹ Scm⁻¹ at room temperature and ∼ 10⁻⁶ Scm⁻¹ at 500 ^∘C. The conductivity variation shows a cross over from Mott-type hopping behaviour at lower temperatures to a thermally activated Arrhenius behaviour at higher temperatures.     

Integrated modeling and simulation of vehicle and human multi-body dynamics for comfort assessment in railway vehicles

An integrated vehicle-biodynamic model is developed in this article by using multi-domain energy domain bond graph model simulation and multi-body simulation software ADAMS VI-Rail. These models are specifically used to evaluate passenger ride comfort in a railway vehicle where vertical and lateral excitations at the wheels arise out of the track irregularities. In the bond graph model, the carbody of the railway vehicle is treated as an Euler-Bernoulli beam and its first five modes are included in the model. Thereafter, a detailed model of the railway vehicle is created in ADAMS VI-Rail. The International Organization for Standardization (ISO) 2631 specification is used to determine the passenger comfort for different travel durations and track irregularities.     

An overview on constitutive modelling to predict elevated temperature flow behaviour of fast reactor structural materials

This overview emphasized the aspects of formulation and application of various constitutive models developed by us in recent past viz. Johnson- Cook (JC), modified Zerilli-Armstrong (MZA), strain compensated Arrhenius type model and artificial neural network (ANN) model to predict elevated temperature flow behaviour of fast reactor structural materials. It has been shown that the JC model is not able to represent the high temperature flow behaviour of both alloy D9 and the modified 9Cr-1Mo as it does not incorporate the coupled effect of strain and temperature, and of strain rate and temperature. The new materials model based on Zerilli-Armstrong (ZA) equation considers the coupled effects of temperature and strain and of strain rate and temperature on the flow stress and hence has the capability to predict flow stress over a wider domain temperature and strain rate in comparison with JC model. The formulation and application of strain compensated Arrhenius type constitutive model to predict high temperature flow behaviour of alloy D9 and modified 9Cr-1Mo has been discussed. Development and application of a generic ANN based constitutive model to predict high temperature deformation behaviour of austenitic stainless steels has been highlighted. Finally, a comparative analysis of the merits and shortcomings of these models has been made.     

Graft copolymerization with new class of acidic peroxo salts as initiators. I. Grafting of acrylamide onto cotton–cellulose using potassium monopersulfate,catalyzed by co(II)

Graft copolymerization of acrylamide (AM) onto cotton–cellulose has been studied using a new class of acidic peroxo-salt “potassium monopersulfate” as initiator catalyzed by Co(II). It is observed that the graft yield is influenced by the reaction time, temperature, and concentrations of the monomer, catalyst, initiator, at fixed weight of the polymer. Maximum graft yield (30.8%) is obtained at 40°C under nitrogen atmosphere for the concentrations of monomer 1.2M; initiator 4.83 × 10^?3M; Co(II) 5 × 10^?4M for 4 h of reaction time. The graft copolymers after proper purification have been subjected to IR analysis, testing of their water-retention properties, rot resistance, tensile properties, and behavior towards acids and alkalies. The results of such analysis are compared with the base. Suitable mechanism for the graft copolymerization is suggested and grafting rate has been evaluated.     

X-ray studies on the structure of p-(Pb1−xSnx)1−y Tey thin films

Thin films were deposited by vacuum evaporation of p-(Pb_1−x Sn _x )_1−y Te_y powders (wherex ≃ 0.71 andy ≃ 0.508) on to glass, mica and natural NaCl substrates heated to various temperatures. X-ray diffractograms show that films deposited on colder substrates exhibit inferior crystalline quality. Films deposited atT _sub ≃ 457±5 K are polycrystalline, showing strong (2 0 0) or (2 2 2) peaks along with weaker (2 2 0), (4 0 0) or (4 2 0) peaks. Variance analyses performed on intense line profiles show that the crystallite size, r.m.s. strain and dislocation density are fairly high even in polycrystalline films. PbSnTe crystallites show a preference for (1 0 0)-oriented growth on heated glass and (1 0 0)-cleaved NaCl substrates; but on equally heated mica, their growth shows an initial preference for the (1 1 1) orientation, which gradually switches over to the (1 0 0) orientation for higher thicknesses. Probably due to a higher SnTe content, PbSnTe crystallites show evidence of misorientation on heated glass and natural NaCl substrates.     

In situ compatibilization of low-density polyethylene and polydimethylsiloxane rubber blends using ethylene–methyl acrylate copolymer as a chemical compatibilizer

The effect of the ethylene–methylacrylate copolymer as a chemical compatibilizer in the 50:50 blend of low-density polyethylene (LDPE) and polydimethylsiloxane rubber (PDMS) has been studied in detail. Ethylene–methylacrylate (EMA) reacted with PDMS rubber during melt-mixing at 180°C to form EMA-grafted PDMS rubber (EMA-g-PDMS) in situ, which acted as a compatibilizer in the LDPE–PDMS rubber blend. An optimum proportion of the compatibilizer (EMA) was found to be 6 wt % based on results of dynamic mechanical analysis, adhesion studies, and phase morphology. Lap shear adhesion between the phases increased significantly on incorporation of 6 wt % of EMA. Dynamic mechanical analysis showed a single glass transition (T_g) peak at ?119°C. This was further supported by X-ray diffraction studies, which exhibited a remarkable increase in the degree of crystallinity and phase morphology and showed a drastic reduction in the size of the dispersed phase at the optimum concentration of EMA. © 1993 John Wiley & Sons, Inc.     

Radial distribution function analysis study on alkali and heat-treated ramie fiber

The radial distribution function (RDF) analysis of wide-angle X-ray diffraction by ramie fibers in untreated condition and after treatment with alkali of mercerizing strength or heat have been carried out. Interatomic distances, coordination numbers, mean square displacements, and coupling constants for different atom pairs have been calculated. The results have been interpreted in terms of a difference in both the conformation and packing of molecular chains in raw and alkali-treated ramie. In general, the coupling constant values have been found to be more in alkali-treated ramie, indicating relatively weak bond strength. Heat-treated ramie shows a marginal decrease in coupling constant values. © 1994 John Wiley & Sons, Inc.     

Decision Tree based discrimination between inrush currents and internal faults in power transformer

This paper presents a new approach for discriminating inrush currents from internal faults in case of power transformer protection using Decision Tree (DT). Differential current of one cycle inrush and internal faults are taken as inputs to the Decision Tree with corresponding target outputs as ‘0’ for inrush and ‘1’ for internal fault conditions. The DT is trained with inrush currents and internal faults with wide variations in operating parameters of the power network and provides accurate results in distinguishing inrush currents from internal faults. The proposed DT based algorithm is found to be accurate and robust, and thus highly suitable for power transformer protection.