Kumari Swati
@jaduniv.edu.in
SERB- NPDF, Electrical Engineering Department, Jadavpur University
Jadavpur University
EDUCATION
10th - D.A.V Public School, H.F.C Barauni, Bihar (CBSE) - 2007 - Percentage 93 out of 100
10+2 - Jawahar Vidya Mandir, Shyamali, Ranchi, Jharkhand (CBSE) - 2009 - Percentage 81.4 out of 100
B.Tech - Electrical Engineering - Dr. B. C. Roy Engineering College, Durgapur, West Bengal (West Bengal University of Technology) - 2014 - CGPA 8.63/10
MS - Electrical Engineering - Indian Institute of Technology Madras, Chennai, Tamil Nadu - 2019 - CGPA - 8.8 out of 10
PhD - High Voltage Engineering - Indian Institute of Technology Madras, Chennai, Tamil Nadu - 2019 , Thesis Title - Investigation on Electrical Insulation and Thermal Performance of Transformer Oil on Dispersion of Titania Nanoparticles with Surfactant, Guide - Prof. R. Sarathi
RESEARCH, TEACHING, or OTHER INTERESTS
Electrical and Electronic Engineering
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Kumari Swati, Vishnu M, K Arul Prakash, and R Sarathi
IOP Publishing
Abstract The heat transfer characteristics of nanofluid produced by mixing nano titania with transformer oil, facilitated by addition of surfactants are analyzed. A 2D model is used to analyze the heat transfer and fluid flow characteristics of nano fluid for understanding the formation of hot spots in the chamber filled with nanofluid. Governing equations for conservation of mass, momentum and energy for capturing the above characteristics are described. The temperature along the vertical mid line from the hot spot are measured experimentally and compared with simulation results. Temperature distribution obtained for nanofluid and transformer oil under both steady and transient state has revealed high rate of heat dissipation in nanofluid. Streamlines have shown the presence of press board affects flow in the bulk of the cavity. Nusselt number estimated across the edges of the hot spot has shown higher convective heat transfer in nanofluid.
Kumari Swati, R. Sarathi, K. Sahitya Yadav, Nathaniel Taylor, and Hans Edin
Institute of Electrical and Electronics Engineers (IEEE)
Titania (TiO2) nanoparticles with cetyl trimethyl ammonium bromide (CTAB) surfactant dispersed in transformer oil has higher corona inception voltage than the normal transformer oil, under AC, DC, and composite AC and DC voltages. It is observed that corona inception voltage is lower under composite voltages compared to AC and DC voltages. The corona activity radiates ultra high frequency (UHF) signals with its dominant frequency near 1 GHz. Operating a spectrum analyzer in zero span mode, the UHF signals generated from the corona activity, the number of discharges is observed to be more under composite voltages than under AC voltages, both at inception and at higher voltages. A reduction in interfacial tension and an improvement in flash point is observed in nano-titania with surfactant dispersed transformer oil. The addition of surfactant reduces the turbidity of the nanofluid. Phase Resolved Partial Discharge (PRPD) analysis with UHF signals measured, indicates that corona discharge activity occurs around the peak and the pre-peak rising portions of the supply voltage. It is observed that more discharges occur in the positive half cycle for AC superimposed with positive DC voltage and in the negative half cycle for AC superimposed with negative DC voltage. The magnitude of UHF signals formed due to corona activity is less with nanofluid, irrespective of voltage profiles.
Kumari Swati and R. Sarathi
IEEE
In the present work, an attempt has been made to obtain stable nanofluids by dispersing an appropriate amount of titania nanoparticles in transformer oil as base oil. The surfactant added in appropriate amount helps in achieving consistent dispersion of the nanoparticles in colloidal solution. A set of experiments were done for understanding the discharge trait because of particle movement in nanofluid and pure transformer oil. It is noted that the particle levitation voltage in nanofluids achieves an increment as compared to base transformer oil. It is realised that partial discharges are generated because of movement of particle in nanofluid which emits UHF signals with 0.9 GHz as major frequency content. The partial discharge trait in nanofluid is studied under AC, DC and composite voltages. The acquired UHF signals are fed to spectrum analyser to realise number of discharges that occurs on application of supply voltage. The number of discharges are noted to be lesser in nanofluids compared to transformer oil. For investigating the phase of supply where discharges are generated because of particle movement, Phase Resolved Partial Discharge (PRPD) studies were done for the motion of conducting particle in nanofluid on application of AC and composite voltages.
Kartik S Sharma, Kumari Swati, and R. Sarathi
IEEE
In the present work, thermal ageing of oil impregnated pressboard material in mineral oil and nanofluid was carried out and fundamental characteristics viz surface discharge inception voltage under high frequency AC voltages and with harmonic voltages with different THDs are studied. It is observed that SDIV increases with increase in supply voltage frequency. Also, on thermal ageing, reduction in SDIV is observed, irrespective of frequency of the AC voltage. Also, increase in harmonic frequency with increase in THDs showed reduction in SDIV. In addition, charge accumulation studies are carried out. It is observed that three layers of OIPs store more charge and dissipates slowly. Also, negative charges get accumulated more than positive charges. PRPD analysis shows that the surface discharge activity on OIPs occurs near to the peak of the AC voltage and with harmonic AC voltages when dv/dt is high.
Kumari Swati, , Ramanujam Sarathi, Kartik Sunil Sharma, , and
School of Electrical Engineering and Informatics (STEI) ITB
SDIV of OIP material gets altered with thermal ageing temperature of OIP material, supply voltage frequency and the harmonic content in the supply voltage. The UHF signal radiated due to surface discharges formed under AC voltage, high frequency AC voltages and with harmonic voltages, have dominant frequency at about 0.9 GHz. Surface charge accumulation studies indicate that thermal ageing have high impact on amount of charge accumulation. Also number of layers of insulation have high charge trap density, which is ascertained through tdv/dt plot. The amount of charge accumulated is high with pressboard impregnated in titania nanoparticle dispersed transformer oil. The SD activity occurs at the rising portion of AC voltage and at high dv/dt’s with harmonic AC voltages. More number of discharges occur with OIPs thermally aged at higher temperature. Physico-chemical changes clearly indicate not much of a change occurs with transformer insulation due to thermal ageing.
Ramanujam Sarathi and Kumari Swati
IEEE
Titania (TiO2) nanoparticles dispersed transformer oil has high Corona Inception Voltage (CIV). The volume of nanoparticles and the amount of surfactant have a strong influence on corona inception voltage. It is observed that the CIV is almost the same under high frequency AC voltage. CIV reduces with increase in level of distortion of the harmonic AC voltages. Corona generates UHF signal with its dominant frequency at 1 GHz. The characteristics is the same irrespective of harmonic voltages with different THDs. PRPD analysis was carried out to understand the discharge occurrence phase under harmonic voltages and could clearly indicates that discharges always occurs at the point where dv/dt is high. In addition, it is observed that discharges in negative half cycle are high at the point of corona inception, irrespective of harmonic voltages with different level of distortions.
Kumari Swati, K. Sahitya Yadav, R. Sarathi, R. Vinu, and M. G. Danikas
Institute of Electrical and Electronics Engineers (IEEE)
Titania (TiO2) nanoparticles dispersed transformer oil has high Corona Inception Voltage (CIV) and breakdown strength, and gets further enhanced on insertion of the barrier in the electrode gap. The volume of nanoparticles and the amount of surfactant have a strong influence on the dispersion of nanoparticles in transformer oil and were characterized through viscosity measurement, particle size analysis and by zeta potential measurements. It was also observed that with needle plane configuration, negative DC voltages have high breakdown voltage as compared to positive DC and AC voltages. Improvement in breakdown voltage with barrier can be obtained by placing the barrier at 20–80% of electrode gap from the tip of the high-voltage electrode. The breakdown voltage of needle plane electrode configuration was calculated based on normal distribution parameters. It was observed that the corona activity generates Ultra High Frequency (UHF) signal in the frequency range of 0.7–2 GHZ with its dominant frequency at 0.9 GHz and was characterized using a ternary plot. The discharge activity was studied by using a spectrum analyzer by operating it in zero span mode with 0.9 GHz as center frequency. It was observed that for a given voltage under AC and DC voltages, the magnitude of discharges is less with nanoparticles dispersed transformer oil. A pyrolysis study indicated no variation in the composition of the oil with the addition of titania. It was observed that the esters present in the oils were alkyl substituted oxalic acid and alkyl substituted sulfurous acid esters.