Prem Ranjan - Academia.edu (original) (raw)
Papers by Prem Ranjan
IEEE Transactions on Instrumentation and Measurement
A moisture sensing technique for real-time monitoring of the moisture content in transformer oil ... more A moisture sensing technique for real-time monitoring of the moisture content in transformer oil based on an S-taper fiber structure, is proposed and experimentally demonstrated, with the advantages of high sensitivity, excellent repeatability, simple fabrication, compact structure and resistance to ambient temperature variation. By analyzing the physical model of the S-taper fiber, the quantitative relationship between the wavelength change of the transmission dip in the transmission spectrum of the S-taper fiber and the moisture content is established. Then the S-taper fibers with different structural parameters, such as the waist diameter and the axial offset, were fabricated in the lab, and actual measurements in transformer oil samples with different moisture content are carried out. The results show that the transmission dip experiences a red-shifts with decreasing moisture, which could be used to correlate/trace moisture content. It is demonstrated that the S-taper fiber achieves higher detection sensitivity with a decreasing waist diameter or increasing axial offset. For the Staper fiber with a waist diameter of 50 μm and an axial offset of 110 μm, the sensitivity and the lower detection limit reach up to 0.48 nm/ppm and 2.19 ppm, respectively. Therefore, the S-taper fiber sensor could effectively in-situ monitor the moisture content in the transformer oil in real-time, which helps to detect the insulation damp problem in the early stage of the transformer in time and ensure its long-term safe operation.
Electrical Characterization and Modeling of High Frequency Arcs for Higher Voltage Aerospace Systems
IEEE Transactions on Transportation Electrification
A review on insulation challenges towards electrification of aircraft
High Voltage
Standards and Regulations Pertaining to Aircraft
Transportation Electrification, Dec 9, 2022
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.
Partial Discharge Investigation under Low Air Pressure and Variable Frequency for More-electric-aircraft
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.
Partial Discharge Detection and Sensitivity Improvement for Bushing Based on Optical Interference Technique
IEEE Transactions on Power Delivery, 2021
Propagation and localisation of partial discharge in transformer bushing based on ultra‐high frequency technique
High Voltage, 2021
Partial Discharge Detection and Diagnosis of Transformer Bushing Based on UHF Method
IEEE Sensors Journal, 2021
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.
IEEE Transactions on Instrumentation and Measurement
A moisture sensing technique for real-time monitoring of the moisture content in transformer oil ... more A moisture sensing technique for real-time monitoring of the moisture content in transformer oil based on an S-taper fiber structure, is proposed and experimentally demonstrated, with the advantages of high sensitivity, excellent repeatability, simple fabrication, compact structure and resistance to ambient temperature variation. By analyzing the physical model of the S-taper fiber, the quantitative relationship between the wavelength change of the transmission dip in the transmission spectrum of the S-taper fiber and the moisture content is established. Then the S-taper fibers with different structural parameters, such as the waist diameter and the axial offset, were fabricated in the lab, and actual measurements in transformer oil samples with different moisture content are carried out. The results show that the transmission dip experiences a red-shifts with decreasing moisture, which could be used to correlate/trace moisture content. It is demonstrated that the S-taper fiber achieves higher detection sensitivity with a decreasing waist diameter or increasing axial offset. For the Staper fiber with a waist diameter of 50 μm and an axial offset of 110 μm, the sensitivity and the lower detection limit reach up to 0.48 nm/ppm and 2.19 ppm, respectively. Therefore, the S-taper fiber sensor could effectively in-situ monitor the moisture content in the transformer oil in real-time, which helps to detect the insulation damp problem in the early stage of the transformer in time and ensure its long-term safe operation.
Electrical Characterization and Modeling of High Frequency Arcs for Higher Voltage Aerospace Systems
IEEE Transactions on Transportation Electrification
A review on insulation challenges towards electrification of aircraft
High Voltage
Standards and Regulations Pertaining to Aircraft
Transportation Electrification, Dec 9, 2022
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.
Partial Discharge Investigation under Low Air Pressure and Variable Frequency for More-electric-aircraft
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.
Partial Discharge Detection and Sensitivity Improvement for Bushing Based on Optical Interference Technique
IEEE Transactions on Power Delivery, 2021
Propagation and localisation of partial discharge in transformer bushing based on ultra‐high frequency technique
High Voltage, 2021
Partial Discharge Detection and Diagnosis of Transformer Bushing Based on UHF Method
IEEE Sensors Journal, 2021
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.