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Khan, Umer-Amir,Lee, Sang-Hwa,Seong, Jae-Kyu,Lee, Bang-Wook The Korean Society of Superconductivity and Cryoge 2010 한국초전도저온공학회논문지 Vol.12 No.2
A considerable amount of research material discussing designs and properties of High Temperature Superconducting Fault Current Limiter (HTS FCL) is available. However, a shortage of research concerning positioning of HTS FCL in power grid is felt. In this paper a feasibility study of HTS FCL positioning in Smart Grid through simulation analysis is carried out. A complete power network (including generation, transmission and distribution) is modeled in Simulink / SimPowerSystems. A generalized HTS FCL is also designed by integrating Simulink and SimPowerSystem blocks. The distribution network of the model has a wind turbine attached to it forming a micro grid. Three phase fault have been simulated along with placing FCL models at key points of the distribution grid. It is observed that distribution grid, having distributed generation sources attached to it, must not have a single FCL located at the substation level. Optimized HTS FCL location regarding the best fault current contribution from wind turbine has been determined through simulation analysis.
Amir Khan, Umer,Jong-Geon Lee,Amir, Faisal,Bang-Wook Lee Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.6
<P>The key obstacle in integrating high-voltage direct current (HVDC) point-to-point networks into meshed multiterminal HVDC networks (MTDC) is the absence of dc circuit breakers (DCCBs), which can timely and reliably isolate the faulty HVDC network from the MTDC. In this paper, a novel hybrid-type superconducting DCCB model (SDCCB) is proposed. The SDCCB has a superconducting fault current limiter (SFCL) located in the main line, to limit the fault current until the final trip signal to the SDCCB is given. After the trip signal, insulated-gate bipolar transistor (IGBT) switches located in the main line will commutate the fault current into a parallel line, where dc current is forced to zero by combination of IGBTs and surge arresters. DC fault current behavior in MTDC and fundamental requirements of DCCB for MTDC were described, followed by an explanation of the working principles of the SDCCB. To prove the viability of the SDCCB, a simulation analysis demonstrating SDCCB current interruption performance was done for changing the intensity of dc fault current. It was observed that the passive current limiting by SFCL caused significant reduction in fault current interruption stress for SDCCB. Furthermore, fundamental design requirements for SFCL, including the effect of SFCL quenching impedance on SFCL voltage rating and energy dissipation capacity, were investigated. Finally, advantages and limitations of the SDCCB were highlighted.</P>
Khan, Amir,Zaman, Gul,Jung, Il Hyo Marcel Dekker, Inc 2017 JOURNAL OF POROUS MEDIA Vol.20 No.7
<P>This article presents some new exact solutions corresponding to unsteady magnetohydrodynamic flow of generalized Jeffrey fluid in a rectangular duct, filled with a porous medium oscillating parallel to its length. The exact solutions are established by means of the double finite Fourier sine transform and discrete Laplace transform. The series solution of velocity field, associated shear stress, and volume flow rate in terms of Fox H-function, satisfying all imposed initial and boundary conditions, have been obtained. Also, the obtained results are analyzed graphically through various pertinent parameters.</P>
Investigation of Coherent Flow Turbulence in the Proximity of Mid-channel Bar
Mohd Amir Khan,Nayan Sharma 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
The turbulent flow characteristics in the vicinity of mid-channel bar are studied in this paper. The velocity is measured with the help of the acoustic Doppler velocimetry (ADV). Fractal modelling is done for analysing the fractal nature of bursting events. The conditional Reynolds stress structure was analysed by using the quadrant technique. Decomposition of Reynolds stress help in studying the distribution of stress among the four quadrants. The hole-size concept is utilized for segregating the extreme bursting events from the low intensity events. Variation of quadrants stresses with the hole-size is analysed. The result of hole-size study indicates that the extreme turbulent burst is produced by the mid channel bar. The new parameter inclination ratio is evolved in this research to reflect streambed elevation changes. The results indicate that the high-level turbulence is generated at region near upstream end of mid-channel bar. The presence of mid-channel bar causes the critical changes to the turbulent structure of flow, where high Reynolds stresses are generated at region near upstream region of mid-channel bar. Third order moments are computed for vertical lines in the proximity of mid-channel bar. High value of third order moments for bar condition indicate that the intense turbulent mixing and momentum exchange take place.
Md. Amir Khan,Nayan Sharma 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7
Braided river is currently important topic of study; several scientists doing research on the complexity of braided river. However,the turbulent characteristics of flow around the braid bar is not thoroughly studied till now. In the current paper, the quadrant methodis used for analyzing the turbulence characteristics of flow in the vicinity of bar using 2-D bursting events technique. Although manyadvances have been made within recent years in interpreting the mechanics of flow, transport of sediment and sedimentaryarchitecture of braided rivers, many key issues remain to be addressed in particular the underlying processes of braid bar initiation. An attempt has been made herein to relate the depositional characteristics around the bar in the braided river model to the sweep andejection bursting events. The concept of the hole is used in order to isolate the extreme events that contribute to the turbulent burst. The mean angle of sweep and ejection events possesses direct relationship with the scouring/ deposition characteristics in the vicinityof bar. The mean values contour of normalized ejection and sweep stress are plotted and their variation with the changing discharge isstudied in this paper.
움아르 아미르(Umer Amir Khan),오석호(Seok-Ho Oh),성재규(Jae-Kyu Seong),신우주(Woo-Ju Shin),이상화(Sang-Hwa Lee),이방욱(Bang-Wook Lee) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
This paper discusses the benefits of DC LED lighting system and the challenges that are hindering its large scale adoption in Korea. Despite providing high efficiency, long life span and easy integration with renewable energy resources the price and installation costs are so high that it is beyond the reach of domestic users. In the end suggestions are provided about how the prices of DC LED systems can be brought down.