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Rudranna N.,Rashtreeya Vidyalaya College of Engineering | Rajan J.,Indian Central Power Research Institute
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2012

Corrosion of copper due to sulphur in oil has affected the performance of transformers. The fundamental processes governing corrosion of copper due to sulphur in oil are still not well understood. In this paper, the dielectric performance of paper oil insulation under conditions of copper sulphide is discussed based on changes in capacitance, Insulation resistance and Partial discharges. Electric field analysis using FEM and PD results are employed to develop an empirical model to predict PD inception of paper oil insulation when copper sulphide is present. A simple model is also proposed to explain progressive copper sulphide migration in paper insulation. The non-linear V-I characteristics of copper sulphide is discussed to explain the breakdown of paper¿oil insulation. © 1994-2012 IEEE.

Munaiah Y.,CSIR - Central Electrochemical Research Institute | Sundara Raj B.G.,Indian Central Power Research Institute | Prem Kumar T.,Indian Central Power Research Institute | Ragupathy P.,CSIR - Central Electrochemical Research Institute | Ragupathy P.,Indian Central Power Research Institute
Journal of Materials Chemistry A | Year: 2013

Nearly X-ray amorphous hollow sphere manganese oxides (hollow sphere MnO2) have been synthesized by a carboxylic acid-mediated system containing KMnO4 and Na2S2O4 under ambient conditions for supercapacitor applications. The product was characterized by powder XRD, Raman spectroscopy and thermal analysis. SEM and TEM were used to investigate the morphology of MnO2. The as-prepared MnO2 was X-ray amorphous and had particles in the size range 0.1-1 μm. A mechanism has been proposed for the formation of hollow sphere structures in the micro-emulsion medium. Upon annealing the sample at temperatures greater than 500 °C, the amorphous MnO2 transforms into Mn2O3. Cyclic voltammetry and galvanostatic charge-discharge cycling were used to evaluate the electrochemical performance. The initial discharge capacities were found to be 283 and 188 F g-1 in 0.1 M Ca(NO3)2 and 0.1 M Na2SO4, respectively, at a current density of 0.5 mA cm-2. The higher specific capacitance in the electrolyte with a bivalent cation is attributed to the reduction of two Mn4+ to Mn3+ by each of the bivalent cations present in the electrolyte. © The Royal Society of Chemistry 2013.

Mandi R.P.,Indian Central Power Research Institute | Yaragatti U.R.,Indian National Institute of Engineering
International Journal of Electrical Power and Energy Systems | Year: 2014

This paper describes the results of energy efficiency enhancement in 23 numbers of 210 MW coal fired power plants spread over India. Energy efficiency improvement of major auxiliary equipment with different plant load factors are summarized here with improved performance. The effect of plant load factor on all major auxiliary equipment and improvement in performance of auxiliary equipment are discussed in this paper. Operation of the plant at improved plant load factor reduced the specific auxiliary power from 11.23% at 70% PLF to 8.74% at 100% PLF that reduced the net auxiliary power by 9.1 MU/year that is an equivalent reduction of CO2 emission by 9500 t/year. Optimizing the excess air, controlling the furnace ingress, enhanced energy efficiency of individual equipment by proper maintenance, etc., improves the plant capacity and reduces the overall auxiliary power by about 1.5-2.1% of gross energy generation i.e., equivalent CO2 reduction of 23,000-32,400 t/year and release an additional power of about 3.5 MW (for a typical one 210 MW power plant) into grid. © 2014 Elsevier Ltd. All rights reserved.

The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted. © 2013 Elsevier B.V. All rights reserved.

Nithya V.D.,Bharathiar University | Selvan R.K.,Bharathiar University | Kalpan D.,Indian Central Power Research Institute | Vasylechko L.,Lviv Polytechnic | Sanjeeviraj C.,Alagappa Chettiar College of Engineering And Technology
Electrochimica Acta | Year: 2013

Nanosized Bi2WO6 particles were successfully synthesized by sonochemical method with an objective to develop an inexpensive and eco-friendly electrode material for supercapacitors. The prepared materialwas subjected to various thermal, structural, morphological, compositional, electrical and electrochem-ical studies. Bi2WO 6 nanoparticle with homogeneous distribution was achieved through sonochemicalprocess. The lattice parameter and atomic positions of Bi 2WO6 structure were refined through Reitveldanalysis. The electrochemical performance of Bi2WO6 nanoparticles was investigated in various aqueouselectrolytes such as 1 M NaOH, 1 M LiOH, 1 M Na2SO4, 1 M KOH and 6 M KOH solutions. Among these,the material exhibited an enhanced electrochemical performance in KOH electrolyte due to its smallerhydration sphere radius, high ionic mobility and lower equivalent series resistance. The charge-dischargestudies rendered a specific capacitance of 608 F/g in 1 M KOH at a current density of 0.5 mA/cm2. Bi2WO6 exhibited an excellent coulombic efficiency and specific capacitance of around 304 F/g at 3 mA/cm2inthe potential range from -0.9 to 0.1 V vs Hg/HgO in 1 M KOH electrolyte. The above results assured thatBi2WO6 could be utilized as suitable negative electrode material for supercapacitor applications and 1 MKOH could be its desirable electrolyte. © 2013 Elsevier Ltd. All rights reserved.

Singh M.,Indian Central Power Research Institute
Proceedings of the IEEE Power Engineering Society Transmission and Distribution Conference | Year: 2016

Distance relays are set in coordination with the over current relays for protection of sub-transmission lines. Depending upon the location of faults on the transmission lines, faults are cleared by the distance relays from their zone-1 or zone-2 operations. If the distance relays fails due to any relay failure reasons, then over current relays operates as backup relays to clear the same fault after some time delay. These time delays are known as coordination time margins. The coordination time margins with respect to backup over current relays are at minimum at starting of zone-1 and zone-2 of distance relays and increases in forward direction of zones of distance relays. In this research article, the zone -2 of distance relays are optimised in such a manner that desired coordination time margin remains valid for all the fault location in zone-1 and zone-2 of distance relays. Integration of decentralised distributed energy resources may cause the change in the fault levels which may lead to violation of coordination time interval among the distance and over current relays. In order to handle this problem, the non-standard time inverse over current relays are proposed for better zone-2 selection of distance relays. The proposed user defined non-standard time inverse over current relay have flexible relay characteristics to maintain the desired coordination time margin among the over current and distance relays for all possible fault locations on zone-1 and zone-2 of distance relays. The coordination of proposed user defined time-inverse over current relay and distance relays results in fast operation of backup over current relays and maintains the coordination among the distance and over current relays during any variable infeed from distributed energy sources. © 2016 IEEE.

Ragupathy P.,Indian Central Power Research Institute
RSC Advances | Year: 2014

In order to understand the influence of manganese valence on electrochemical performance of spinel manganese oxide cathodes, a systematic investigation of doubly substituted LiMn2-x-yZnxTi yO4 (0.05 ≤ x ≤ 0.25, 0.05 ≤ y ≤ 0.2) spinel compositions has been reported. The synthesized substituted spinel oxides are correlated to the initial manganese valence, observed capacity, ratio of observed to theoretical capacity, capacity loss, degree of manganese dissolution, and irreversible capacity (IRC) loss. The capacity retention and initial observed capacity are found to depend on the manganese valence for the fixed amount of manganese content in the material. The obtained chemical and electrochemical data reveal that the extraction of lithium becomes more difficult with decreasing manganese valence. This phenomenon can be explained by the perturbation of the Mn-Mn interaction across the shared edges, which reduces the ability to extract lithium from spinel cathodes. These investigations lead to finding the optimum doped compositions that can offer the combination of long cycle life, high capacity, and high rate capability. This journal is © The Royal Society of Chemistry 2014.

Venkateswara Rao M.,Indian Central Power Research Institute
Materials Science Forum | Year: 2015

Conventional tensile test methods are used for service exposed high temperature boiler tubes to evaluate the deterioration in mechanical properties such as tensile strength, yield strength and percentage elongation. The mechanical properties are required to be evaluated periodically as the boiler components undergo material degradation due to aging phenomena. The aging phenomena occurs due to continuous exposure of tubes to high temperature & pressure steam prevailing inside the tubes and high temperature exposure to corrosive combustible gases from the external surfaces within the boiler. A recent developed new technique called small punch testing has been used to evaluate the tensile properties of SA 213T22 grade steel predominantly exists in super-heater and re-heater sections of boiler. The small punch tests have been carried out on the miniature disk shaped specimens of diameter of 8.0 mm and 0.5 mm thickness extracted from both the new and service exposed tubes. Conventional uniaxial tensile tests on standard specimens from the same tube material have also been performed for comparison. The service exposed tubes showed considerable loss in mechanical properties in both the conventional and small punch test results. Correlations of tensile properties have been obtained based on the comparative analysis of both small punch and uniaxial tensile test results. Further, the study showed that an appropriate empirical relation could be generated for new and service exposed materials between both the techniques. Conventional test methods require large quantity of material removal for test samples from in-service components whereas small punch test method needs only a miniature sample extraction. This small punch test technique could also be extended to evaluate the thicker section boiler components such as pipelines and headers in the boiler as a part of remaining life assessment study. Also this technique could be a useful tool to any metallic component where large quantity of sample removal may be difficult or may not be feasible. © (2015) Trans Tech Publications, Switzerland.

Thomas P.,Indian Central Power Research Institute | Thomas P.,Indian Institute of Science | Varughese K.T.,Indian Central Power Research Institute | Dwarakanath K.,Indian Central Power Research Institute | Varma K.B.R.,Indian Institute of Science
Composites Science and Technology | Year: 2010

The possibility of obtaining relatively high dielectric constant polymer-ceramic composite by incorporating the giant dielectric constant material, CaCu3Ti4O12 (CCTO) in a Poly(vinylidene fluoride) (PVDF) polymer matrix by melt mixing and hot pressing process was demonstrated. The structure, morphology and dielectric properties of the composites were characterized using X-ray diffraction, Thermal analysis, scanning electron microscope, and impedance analyzer. The effective dielectric constant (εeff) of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz-1 MHz) under study. The dielectric loss did not show any variation up to 40% loading of CCTO, but showed an increasing trend beyond 40%. The room temperature dielectric constant as high as 95 at 100 Hz has been realized for the composite with 55 vol.% of CCTO, which has increased to about 190 at 150 °C. Theoretical models like Maxwell's, Clausius-Mossotti, Effective medium theory, logarithmic law and Yamada were employed to rationalize the dielectric behaviour of the composite and discussed. © 2010.

Sankar K.V.,Bharathiar University | Kalpana D.,Indian Central Power Research Institute | Selvan R.K.,Bharathiar University
Journal of Applied Electrochemistry | Year: 2012

The nanosized Mn 3O 4 particles were prepared by microwave-assisted reflux synthesis method. The prepared sample was characterized using various techniques such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Raman analysis, and transmission electron microscopy (TEM). Electrochemical properties of Mn 3O 4 nanoparticles were investigated using cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge analysis in different electrolytes such as 1 M KCl, 1 M Na 2SO 4, 1 M NaNO 3, and 6 M KOH electrolytes. XRD pattern reveals the formation of single-phase Mn 3O 4 nanoparticles. The FT-IR and Raman analysis also assert the formation of Mn 3O 4 nanoparticles. The TEM image shows the spherical shape particles with less than 50 nm sizes. Among all the electrolytes, the Mn 3O 4 nanoparticles possess maximum specific capacitance of 94 F g -1 in 6 M KOH electrolyte calculated from CV. The order of capacitance obtained by various electrolytes is 6 M KOH > 1 M KCl > 1 M NaNO 3 > 1 M Na 2SO 4. The EIS and galvanostatic charge-discharge results further substantiate with the CV results. The cycling stability of Mn 3O 4 electrode reveals that the prepared Mn 3O 4 nanoparticles are a suitable electrode material for supercapacitor application. © 2012 Springer Science+Business Media B.V.

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