Faculty Publications
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Item Associative study of Absorbing Aerosol Index (AAI) and precipitation in India during monsoon season (2005 to 2014)(SPIE spie@spie.org, 2016) Dubey, S.; Mehta, M.; Singh, A.Based on their interaction with solar radiations, aerosols may be categorized as absorbing or scattering in nature. The absorbing aerosols are coarser and influence precipitation mainly due to microphysical effect (participating in the formation of Cloud Condensation Nuclei) and radiative forcing (by absorbing electromagnetic radiations). The prominent absorbing aerosols found in India are Black Carbon, soil dust, sand and mineral dust. Their size, distribution, and characteristics vary spatially and temporally. This paper aims at showing the spatio-temporal variation of Absorbing Aerosol Index (AAI) and precipitation over the four most polluted zones of Indian sub-continent (Indo-Gangetic plains 1, Indo-Gangetic plains 2, Central and Southern India) for monsoon season (June, July, August, September) during the last decade (2005 to 2014). Zonal averages AAI have been found to be exhibiting an increasing trend, hence region-wise correlations have been computed between AAI and precipitation during monsoon. Daily Absorption Aerosol Index (AAI) obtained from Aura OMI Aerosol Global Gridded Data Product-OMAEROe (V003) and monthly precipitation from TRMM 3B42-V7 gridded data have been used. © 2016 SPIE.Item Correlation of wind speed and wind turbine reliability in system adequacy assessment(Institute of Electrical and Electronics Engineers Inc., 2018) Nguyen, N.; Almasabi, S.; Mitra, J.; Shenoy, B.B.This paper proposes a new method to evaluate the reliability of a power system in the presence of wind generation, considering the negative correlation of wind turbine reliability and wind speed. Although wind power integration supports the power system by increasing generation, its intermittent nature is a matter of concern. As the integration of wind power systems steadily increases, the reliability of such integrated systems needs re-evaluation. Besides the relationship between wind speed and wind power output, the relationship between wind speed and wind turbine failure rate also has an impact on reliability of a wind farm and needs to be given due consideration. The method proposed in this paper to evaluate system reliability is implemented using the sequential Monte Carlo simulation. The implementation is tested on the IEEE RTS-79 system with relevant modifications. The effectiveness of the proposed method is proved by comparing system reliability indexes with and without considering the impacts of correlation between wind turbine reliability and wind speed. © 2018 IEEE.Item Application of Proper Orthogonal Decomposition in Concrete Performance Appraisal(Springer Science and Business Media Deutschland GmbH, 2021) Manoj, A.; Babu Narayan, K.S.B.Mould ability of concrete has made it the most versatile and popular material of construction. Workability, strength and durability of concrete are very important characteristics that depend on a large number of variables like cement and aggregate type, mix proportioning, method of mixing, conveying, placing and curing and environmental conditions of exposure like temperature, humidity, wind velocity and insolation. The degrees to which workability, strength and durability characteristics vary, and also interplay and conflicts make decision on consideration of independent variables that influence concrete performance, make the job of analysts very complex. Proper Orthogonal Decomposition (POD) is a tool that has great usage potential in reorganizing and rationalizing vast data to understand dependence, interdependence and independence of variables that affect the concrete characteristics. This paper presents the utility of Proper Orthogonal Decomposition in concrete performance appraisal. © 2021, Springer Nature Singapore Pte Ltd.Item Probabilistic Load Flow Considering Load and Wind Power Uncertainties using Modified Point Estimation Method(Institute of Electrical and Electronics Engineers Inc., 2022) Singh, V.; Moger, T.; Jena, D.Nowadays, renewable energy sources (REs) are increasingly integrated into electrical power networks. Among many REs, wind energy has emerged as a prominent source of electricity. However, rising wind power penetration has increased the system's net generation variability. Consequently, the ability to monitor and simulate the behavior of wind power generation (WPG) in detail is critical. Furthermore, the wind speed or wind power output of different wind farms can be highly interdependent and may not follow Normal distribution. This study proposes a probabilistic load flow (PLF) technique for modeling normally distributed loads and non-normally distributed WPG based on the modified point estimation method (PEM). This modification allows modeling dependent input random variables as a function of many independent ones using the Nataf transformation. By utilizing the findings of the Monte-Carlo method as a reference, the usefulness of the suggested technique is tested by conducting case studies on a 24-bus equivalent system of the Indian Southern region power grid. Simulation results indicate that the modified PEM can easily handle the correlation and have high processing efficiency. © 2022 IEEE.Item Modified Cumulant based Probabilistic Load Flow Considering Correlation between Loads and Wind Power Generations(Institute of Electrical and Electronics Engineers Inc., 2022) Singh, V.; Moger, T.; Jena, D.With the growing use of wind sources, power system analysis should consider the variation of wind power and the correlation among wind farms. In this paper, the Cumulant method (CM) for performing probabilistic load flow (PLF) analysis is modified to account for the correlation between random input variables. Considering the dependence between loads and wind power generations (WPGs), the modified CM models the dependent variables as a function of many independent ones using the Nataf transformation. The effectiveness of the suggested method is verified by performing case studies on a 24-bus equivalent system of the Indian southern region power grid. Furthermore, relative error values in reference with the Monte-Carlo simulation (MCS) method are analyzed. © 2022 IEEE.Item A critical review on probabilistic load flow studies in uncertainty constrained power systems with photovoltaic generation and a new approach(Elsevier Ltd, 2017) Prusty, B.R.; Jena, D.A power system with large integration of renewable energy based generations is inherently associated with different types of uncertainties. In such cases, probabilistic load flow is a vital tool for delivering comprehensive information for power system planning and operation. Efforts have been made in this paper to perform a critical review on different probabilistic load flow models, uncertainty characterization and uncertainty handling methods, since from its inspection in 1974. An efficient analytical method named multivariate-Gaussian mixture approximation is proposed for precise estimation of probabilistic load flow results. The proposed method considers the uncertainties pertaining to photovoltaic generations and load demands. At the same time, it effectively incorporates multiple input correlations. In order to examine the performance of the proposed method, modified IEEE 118-bus test system is taken into consideration and results are compared with univariate-Gaussian mixture approximation, series expansion based cumulant methods and Monte Carlo simulation. Effect of various correlation cases on distribution of result variables is also studied. The effectiveness of the proposed method is justified in terms of accuracy and execution time. © 2016 Elsevier LtdItem Uncertainty handling techniques in power systems: A critical review(Elsevier Ltd, 2022) Singh, V.; Moger, T.; Jena, D.Integration of renewable generations with electrical power systems has gained considerable attention in recent years due to environmental and economic benefits. However, this integration introduces additional uncertainties into the existing system and requires appropriate uncertainty modeling for power systems. Typically the uncertainties in power systems are modeled using probabilistic or possibilistic approaches. A combined probabilistic-possibilistic approach is necessary when some uncertain variables are probabilistic and others are possibilistic. This paper presents a complete review of uncertainty categorization and several techniques to address the uncertainty in power systems, along with the merits and weaknesses of each technique. The challenges have been highlighted for future research directions. Analytical and approximate methods are reviewed in this paper when wind power generations are integrated into the existing power grid. Considering the uncertainties of wind power generation and system load demands, the basic probabilistic methods such as Monte-Carlo simulation, cumulant, and 2n+1 point estimation methods are implemented. To explore the capability and shortcoming of these basic methods, a 72-bus equivalent system of Indian southern region power grid is taken into consideration. The results obtained using Monte-Carlo simulation method are treated as a benchmark to analyze the performance of the cumulant and 2n+1 point estimation methods. © 2021 Elsevier B.V.Item Effect of soil parameters on dynamic cone penetration indices of laterite sub-grade soils from India(2009) George, V.; Nageshwar Rao, Ch.; Shivashankar, R.The focus of this study was on correlating the effect of grain-size, maximum dry-density (MDD), field moisture content, and the void ratios on penetration measured using the dynamic cone penetrometer (DCP) for laterite soils blended with fines. Tests were performed on soil samples compacted to MDD for moulding water contents set to the optimum moisture content (OMC), dry of OMC, and wet of OMC un-soaked condition. The results indicated that an increase in the fines-content caused a decrease in the MDD, and an increase in the OMC and the DCP penetration. Regressions were developed correlating various parameters. © Springer Science+Business Media B.V. 2008.Item PFWD, DCP and CBR correlations for evaluation of lateritic subgrades(2009) George, V.; Rao, N.C.; Shivashankar, R.The evaluation of subgrade strength plays a major role in pavement design. An understanding of subgrade properties enables the selection of road materials for sub-base and base courses. In developing countries like India, apart from the use of well-established traditional pavement evaluation techniques such as the California bearing ratio (CBR) test and the dynamic cone penetrometer (DCP) test, the use of non-destructive testing devices such as the portable falling weight deflectometers (PFWDs) has gained popularity in recent years. This is mainly because of the inherent capability of PFWDs in obtaining quick estimates of the modulus of subgrade in addition to their simplicity in design and portability. Thus, there exists a need to correlate the results obtained using PFWDs with those obtained using traditional approaches such as the CBR and the DCP for the benefit of road engineers. This work focuses on exploring the correlations between these approaches for lateritic soils in Dakshina Kannada district, India.Item Assessment of mixture boiling heat transfer correlations for ammonia/water mixture(2009) Sathyabhama, A.; Ashok Babu, T.P.The aim of this work is to present a critical examination of both the available experimental data and the performance of the available mixture boiling heat transfer correlations for ammonia/water mixture. First, a selection and comparison of the experimental database found in the open literature at the mentioned working conditions is presented. Subsequently, after a short description of the most relevant heat transfer correlations, and in accordance with the selected data, a detailed analysis of the performance of each correlation is carried out. Results show a small divergence between the experimental data sets and conclude that the presently available correlations show considerable discrepancies in heat transfer coefficients within the selected conditions. © 2009 Wiley Periodicals, Inc.