IEEE Transactions on Transportation Electrification
Abstract-Arcing in future high-voltage aerospace systems could occur more frequently and cause i... more Abstract-Arcing in future high-voltage aerospace systems could occur more frequently and cause irreversible damage to electrical components, system structure and increase the risk of fire. While arcs seen in low-voltage aerospace systems tend to be long-duration and low-energy events, higher power but shortduration arcs may occur in high-voltage aerospace systems if they are readily detectable by system protection. This paper investigates the characteristics of high current arc faults generated at the AC frequencies expected in future rotating machines used for higher voltage aerospace systems. As such, arcs with a peak current up to 4.6 kA are generated at frequencies in the range of 0.5-2 kHz using an underdamped RLC circuit, under pressures of 0.2-1 bar absolute. High frequency arcs exhibit a similar characteristic to lower frequency arcs. A reduction in pressure results in lower arc voltage and arc power. Arcing tests at atmospheric pressure may therefore represent a worst-case scenario and the development of a low-pressure test environment may not be necessary. A black box model is developed to provide good agreement with experimental arc voltage waveforms for different parameters investigated in this study. This is a generalized modeling approach to estimate high-frequency highvoltage arcing characteristics without recourse to experiment.
2022 IEEE 4th International Conference on Dielectrics (ICD), Jul 3, 2022
SF6 alternatives with significantly lower environmental impact have been extensively researched. ... more SF6 alternatives with significantly lower environmental impact have been extensively researched. This paper investigates two electrode configurations and test pressures to mimic the conditions as found in MV/HV equipment to systematically compare the breakdown performance of SF6, C3H2F4 and a mixture of 30% CF3I / 70% CO2 under AC and LI stresses. SF6 possesses comparatively better breakdown performance than the other alternatives investigated in this study. C3H2F4 shows "first breakdown" behavior and only the stable data series is considered for evaluation of 50% breakdown voltage, U50. The lower boiling points of C3H2F4 and CF3I limit its potential application to medium-voltage equipment with a low operating pressure. Due to pyrolysis, there is formation of soot and iodine post-breakdown in C3H2F4 and 30% CF3I / 70% CO2 respectively. This will reduce their dielectric performance and could pose health hazard to maintenance personnel.
IEEE Transactions on Dielectrics and Electrical Insulation, 2021
More-electric-aircrafts (MEAs) are heading towards larger power, higher voltage, and more optimum... more More-electric-aircrafts (MEAs) are heading towards larger power, higher voltage, and more optimum architectures, it is extremely important to understand partial discharge (PD) behaviors under the challenging aeronautical power systems. PD under the pressure of 1–101 kPa and frequency of 50–1000 Hz is studied to emulate the practical situation with the consideration of insulation defects from electric machine windings. The high frequency current transformer (HFCT) is specifically employed to pick up partial discharge signals. Experimental results indicate that PD inception voltage (PDIV) decreases almost linearly with air pressure. As to the discharge amplitude, it increases first and then decreases as air pressure dropping. The highest discharge repetition rate and the number of discharges appear at 30 kPa. High frequency doubles the number of discharges without affecting PD amplitude. Low air pressure causes the phase shift and phase width of the phase-resolved partial discharge (PRPD) to increase, and the trend also is accelerated by high frequency. This experimental approach is beneficial to provide prerequisite knowledge in characterizing PD and assessing its potential adverse impact on the aeronautical power system and consequently contribute to optimizing the insulation design for MEA.
Bushings are essential components in a power transformer where incipient partial discharge (PD) a... more Bushings are essential components in a power transformer where incipient partial discharge (PD) activities and its detection and diagnosis cannot be ignorant. In this paper, an oil-impregnated paper (OIP) bushing is modeled to investigate that the oil gaps between the flange and condenser body in a typical OIP bushing provide a feasible path to trace the electromagnetic signal. As a non-destructive method, UHF (Ultra High Frequency) is proposed to detect 4 typical inside and outside PD defects of 110 kV bushings. To analyze the parameters of different defects, not only phase-resolved partial discharge (PRPD) is presented, but also 16 detailed time-domain and frequency-domain parameters of UHF signal are involved. Then feature extraction and selection are conducted through comparative principal component analysis (PCA) and extremely randomized trees (ET) algorithms. It is revealed that the selected features are representative and ET greatly reduces the amount of data whilst ensuring high accuracy. Fault diagnosis for bushing is finally achieved via support vector machine (SVM) with the selected features. The presented work of bushing PD detection based on UHF sensors provides a complete solution for the bushing diagnosis in potential field application and maintenance.
Microbial fuel cells (MFCs) are emerging as promising technology for the treatment of wastewaters... more Microbial fuel cells (MFCs) are emerging as promising technology for the treatment of wastewaters. The potential energy conversion efficiencies are examined. The rates of energy recovery (W/m3 reactor) are reviewed and evaluated. Some recent data relating to potato-processing wastewaters and a hospital wastewater effluent are reported. Finally, a set of process configurations in which MFCs could be useful to treat wastewaters is schematized. Overall, the MFC technology still faces major challenges, particularly in terms of chemical oxygen demand (COD) removal efficiency.
Abstract Zinc oxide (ZnO) nanoparticles were produced by wire explosion process and characterized... more Abstract Zinc oxide (ZnO) nanoparticles were produced by wire explosion process and characterized through X-ray diffraction (XRD) studies and by TEM studies. The particle size analysis indicates that they follow log-normal distribution and the mean size of the ZnO nanoparticles formed is about 44 nm. Optical band gap of ZnO is found to be 3.21 eV by UV–vis diffuse reflectance spectroscopy (DRS). The synthesized ZnO nano particles were used as photo catalyst for degradation of methylene blue (MB) in aqueous solution. Nano zinc oxide of 100 mg/L was found as the optimum quantity for UV photo degradation of 10 mg/L MB. ZnO nanoparticles were verified for its reusability. The results of the study are compared with commercial ZnO nanoparticle and with Degussa P-25 TiO 2 . LC-MS studies were carried out to identify the intermediates and degradation pathway.
IEEE Transactions on Transportation Electrification
Abstract-Arcing in future high-voltage aerospace systems could occur more frequently and cause i... more Abstract-Arcing in future high-voltage aerospace systems could occur more frequently and cause irreversible damage to electrical components, system structure and increase the risk of fire. While arcs seen in low-voltage aerospace systems tend to be long-duration and low-energy events, higher power but shortduration arcs may occur in high-voltage aerospace systems if they are readily detectable by system protection. This paper investigates the characteristics of high current arc faults generated at the AC frequencies expected in future rotating machines used for higher voltage aerospace systems. As such, arcs with a peak current up to 4.6 kA are generated at frequencies in the range of 0.5-2 kHz using an underdamped RLC circuit, under pressures of 0.2-1 bar absolute. High frequency arcs exhibit a similar characteristic to lower frequency arcs. A reduction in pressure results in lower arc voltage and arc power. Arcing tests at atmospheric pressure may therefore represent a worst-case scenario and the development of a low-pressure test environment may not be necessary. A black box model is developed to provide good agreement with experimental arc voltage waveforms for different parameters investigated in this study. This is a generalized modeling approach to estimate high-frequency highvoltage arcing characteristics without recourse to experiment.
2022 IEEE 4th International Conference on Dielectrics (ICD), Jul 3, 2022
SF6 alternatives with significantly lower environmental impact have been extensively researched. ... more SF6 alternatives with significantly lower environmental impact have been extensively researched. This paper investigates two electrode configurations and test pressures to mimic the conditions as found in MV/HV equipment to systematically compare the breakdown performance of SF6, C3H2F4 and a mixture of 30% CF3I / 70% CO2 under AC and LI stresses. SF6 possesses comparatively better breakdown performance than the other alternatives investigated in this study. C3H2F4 shows "first breakdown" behavior and only the stable data series is considered for evaluation of 50% breakdown voltage, U50. The lower boiling points of C3H2F4 and CF3I limit its potential application to medium-voltage equipment with a low operating pressure. Due to pyrolysis, there is formation of soot and iodine post-breakdown in C3H2F4 and 30% CF3I / 70% CO2 respectively. This will reduce their dielectric performance and could pose health hazard to maintenance personnel.
IEEE Transactions on Dielectrics and Electrical Insulation, 2021
More-electric-aircrafts (MEAs) are heading towards larger power, higher voltage, and more optimum... more More-electric-aircrafts (MEAs) are heading towards larger power, higher voltage, and more optimum architectures, it is extremely important to understand partial discharge (PD) behaviors under the challenging aeronautical power systems. PD under the pressure of 1–101 kPa and frequency of 50–1000 Hz is studied to emulate the practical situation with the consideration of insulation defects from electric machine windings. The high frequency current transformer (HFCT) is specifically employed to pick up partial discharge signals. Experimental results indicate that PD inception voltage (PDIV) decreases almost linearly with air pressure. As to the discharge amplitude, it increases first and then decreases as air pressure dropping. The highest discharge repetition rate and the number of discharges appear at 30 kPa. High frequency doubles the number of discharges without affecting PD amplitude. Low air pressure causes the phase shift and phase width of the phase-resolved partial discharge (PRPD) to increase, and the trend also is accelerated by high frequency. This experimental approach is beneficial to provide prerequisite knowledge in characterizing PD and assessing its potential adverse impact on the aeronautical power system and consequently contribute to optimizing the insulation design for MEA.
Bushings are essential components in a power transformer where incipient partial discharge (PD) a... more Bushings are essential components in a power transformer where incipient partial discharge (PD) activities and its detection and diagnosis cannot be ignorant. In this paper, an oil-impregnated paper (OIP) bushing is modeled to investigate that the oil gaps between the flange and condenser body in a typical OIP bushing provide a feasible path to trace the electromagnetic signal. As a non-destructive method, UHF (Ultra High Frequency) is proposed to detect 4 typical inside and outside PD defects of 110 kV bushings. To analyze the parameters of different defects, not only phase-resolved partial discharge (PRPD) is presented, but also 16 detailed time-domain and frequency-domain parameters of UHF signal are involved. Then feature extraction and selection are conducted through comparative principal component analysis (PCA) and extremely randomized trees (ET) algorithms. It is revealed that the selected features are representative and ET greatly reduces the amount of data whilst ensuring high accuracy. Fault diagnosis for bushing is finally achieved via support vector machine (SVM) with the selected features. The presented work of bushing PD detection based on UHF sensors provides a complete solution for the bushing diagnosis in potential field application and maintenance.
Microbial fuel cells (MFCs) are emerging as promising technology for the treatment of wastewaters... more Microbial fuel cells (MFCs) are emerging as promising technology for the treatment of wastewaters. The potential energy conversion efficiencies are examined. The rates of energy recovery (W/m3 reactor) are reviewed and evaluated. Some recent data relating to potato-processing wastewaters and a hospital wastewater effluent are reported. Finally, a set of process configurations in which MFCs could be useful to treat wastewaters is schematized. Overall, the MFC technology still faces major challenges, particularly in terms of chemical oxygen demand (COD) removal efficiency.
Abstract Zinc oxide (ZnO) nanoparticles were produced by wire explosion process and characterized... more Abstract Zinc oxide (ZnO) nanoparticles were produced by wire explosion process and characterized through X-ray diffraction (XRD) studies and by TEM studies. The particle size analysis indicates that they follow log-normal distribution and the mean size of the ZnO nanoparticles formed is about 44 nm. Optical band gap of ZnO is found to be 3.21 eV by UV–vis diffuse reflectance spectroscopy (DRS). The synthesized ZnO nano particles were used as photo catalyst for degradation of methylene blue (MB) in aqueous solution. Nano zinc oxide of 100 mg/L was found as the optimum quantity for UV photo degradation of 10 mg/L MB. ZnO nanoparticles were verified for its reusability. The results of the study are compared with commercial ZnO nanoparticle and with Degussa P-25 TiO 2 . LC-MS studies were carried out to identify the intermediates and degradation pathway.
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Papers by Prem Ranjan