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S.Senthilkumar,B.Karthik,S.Chandrasekar 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
Partial discharge (PD) detection plays a major role in the life time assessment of liquid insulation in power transformers. Many research works are being carried out to replace conventional mineral oil insulation in transformers by vegetable oils. It is necessary to understand the PD characteristics of vegetable oils before recommending them as an alternate for mineral oil. In this paper, the breakdown strength and PD characteristics of palm and corn oil were investigated in both unaged and thermally aged conditions. Laboratory experiments were performed as per IEC test procedures. PD signals were measured using wide band detection system. Phase resolved PD pattern of vegetable oils and mineral oil were compared. Effect of increase in voltage stress on the PD pattern of palm and corn oil were studied. Time and frequency domain analysis of PD pulses at needle-plane electrode configuration was carried out. Statistical analysis of PD pattern i.e. skewness and shape parameter variations with respect to applied thermal stress were also carried out. From the results, it is observed that palm and corn oils have better breakdown strength and PD characteristics even under long-term thermal stress and hence they can be used for power transformer applications.
S. Purushotham,S.Chandrasekar,Gian Carlo Montanari 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.6
Failure of underground cables due to electrical treeing phenomena, i.e. formation of electrical discharges in the imperfections of cable insulation, is a major problem faced by electrical utilities. Many research works on nanocomposites are being carried out to improve the electrical treeing resistance of the XLPE cable insulation material. Technological advancements in communication and data analytic systems have shown the way for implementing online continuous partial discharge (PD) monitoring systems for high voltage apparatus. Hence collection of PD database of XLPE nanocomposites in the laboratory during entire electrical tree growth process is important for implementing effi cient condition monitoring systems and relatively little work has been published in this area. In this work, PD characteristics of XLPE nanocomposites with 1, 3, 5 and 10 wt% silica were investigated. Electrical tree growth and corresponding phase resolved PD (PRPD) pattern were analysed with respect to time. Cluster analysis of equivalent time–frequency mapping of PD signals was carried out with respect to tree growth time period. Statistical analysis was performed for the entire set of PD data. Results show that cluster analysis of T–F map of PD data is useful in estimating early failure of insulating material due to treeing. Addition of silica nano fi llers in the range of 3–5 wt% concentration signifi cantly improves the PD resistance and breakdown time of XLPE material.
S. Nagendran,S. Chandrasekar 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
The reliability of power transmission and distribution depends up on the consistency of insulation in the high voltage power transformer. In recent times, considering the drawbacks of conventional mineral oils such as poor biodegradability and poor fire safety level, several research works are being carried out on natural ester based nanofluids. Earlier research works show that sunflower oil has similar dielectric characteristics compared with mineral oil. BIOTEMP oil which is now commercially available in the market for transformers is based on sunflower oil. Addition of nanofillers in the base oil improves the dielectric characteristics of liquid insulation. Only few results are available in the literature about the insulation characteristics of nano modified natural esters. Hence understanding the influence of addition of nanofillers in the dielectric properties of sunflower oil and collecting the database is important. Considering these facts, present work contributes to investigate the important characteristics such as partial discharge, lightning impulse, breakdown strength, tandelta, volume resistivity, viscosity and thermal characteristics of SiO₂ nano modified sunflower oil with different wt% concentration of nano filler material varied from 0.01wt% to 0.1wt%. From the obtained results, nano modified sunflower oil shows better performance than virgin sunflower oil and hence it may be a suitable candidate for power transformer applications.
( , s)-Continuous Functions between Topological Spaces
Ravi, O.,Chandrasekar, S.,Ganesan, S. Department of Mathematics 2011 Kyungpook mathematical journal Vol.51 No.3
In this paper, we introduce ($$\tilde{g}$$, s)-continuous functions between topological spaces, study some of its basic properties and discuss its relationships with other topological functions.
Senthilkumar, S.,Karthik, B.,Chandrasekar, S. The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
Partial discharge (PD) detection plays a major role in the life time assessment of liquid insulation in power transformers. Many research works are being carried out to replace conventional mineral oil insulation in transformers by vegetable oils. It is necessary to understand the PD characteristics of vegetable oils before recommending them as an alternate for mineral oil. In this paper, the breakdown strength and PD characteristics of palm and corn oil were investigated in both unaged and thermally aged conditions. Laboratory experiments were performed as per IEC test procedures. PD signals were measured using wide band detection system. Phase resolved PD pattern of vegetable oils and mineral oil were compared. Effect of increase in voltage stress on the PD pattern of palm and corn oil were studied. Time and frequency domain analysis of PD pulses at needle-plane electrode configuration was carried out. Statistical analysis of PD pattern i.e. skewness and shape parameter variations with respect to applied thermal stress were also carried out. From the results, it is observed that palm and corn oils have better breakdown strength and PD characteristics even under long-term thermal stress and hence they can be used for power transformer applications.
Nagendran, S.,Chandrasekar, S. The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
The reliability of power transmission and distribution depends up on the consistency of insulation in the high voltage power transformer. In recent times, considering the drawbacks of conventional mineral oils such as poor biodegradability and poor fire safety level, several research works are being carried out on natural ester based nanofluids. Earlier research works show that sunflower oil has similar dielectric characteristics compared with mineral oil. BIOTEMP oil which is now commercially available in the market for transformers is based on sunflower oil. Addition of nanofillers in the base oil improves the dielectric characteristics of liquid insulation. Only few results are available in the literature about the insulation characteristics of nano modified natural esters. Hence understanding the influence of addition of nanofillers in the dielectric properties of sunflower oil and collecting the database is important. Considering these facts, present work contributes to investigate the important characteristics such as partial discharge, lightning impulse, breakdown strength, tandelta, volume resistivity, viscosity and thermal characteristics of $SiO_2$ nano modified sunflower oil with different wt% concentration of nano filler material varied from 0.01wt% to 0.1wt%. From the obtained results, nano modified sunflower oil shows better performance than virgin sunflower oil and hence it may be a suitable candidate for power transformer applications.
Computational Analysis of Apolipophorin-III in Hyphantria cunea
Chandrasekar R.,Dhanalakshmi R.,Krishnan M.,Kim H. J.,Jeong H. C.,Seo S. J. Korean Society of Sericultural Science 2005 International Journal of Industrial Entomology Vol.10 No.1
Recently a cDNA clone of apoLp-III from Hyphantria cunea was isolated and subjected to computational analysis to compare with other available sequences. Multiple sequence alignments were carried out using the amino acid sequences of apoLp-III from six insects. It was found that the H. cunea apoLp-III has relatively high sequence identities to Spodoptera litura ($69.5\%$), Manduca sexta ($66.8\%$), Galleria mellonella ($65.1\%$), Bombyx mori N4 ($54.3\%$) but less identity to Locusta migratoria ($18.3\%$). The amino acid composition was compared with other insects using EXPASY tools; it shows that alanine (Ala), glutamine (Gln), leucine (Leu) and lysine (Lys) are the major amino acid components of apoLp-III in H. cunea as well as other lepidopterans. Homology modeling performed using PSI-BLAST (PDB template M. sexta) reveals that the apoLp-III molecules consist of five, long amphipathic alpha helical bundles with short loops connecting the helices and shows homology with other insects. Phylogenetic analysis shows that the orthopteran apoLp-III represented by locust was most distantly related to the lepidopteran insects.