Cascading Failures and Contingency Analysis for Smart Grid Security

The modern electric power grid has become highly integrated in order to increase the reliability of power transmission from the generating units to end consumers. In addition, today’s power system are facing a rising appeal for the upgrade to a highly intelligent generation of electricity networks commonly known as Smart Grid. However, the growing integration of power system with communication network also brings increasing challenges to the security of modern power grid from both physical and cyber space. Malicious attackers can take advantage of the increased access to the monitoring and control of the system and exploit some of the inherent structural vulnerability of power grids. Therefore, determining the most vulnerable components (e.g., buses or generators or transmission lines) is critically important for power grid defense. This dissertation introduces three different approaches to enhance the security of the smart grid. Motivated by the security challenges of the smart grid, the first goal of this thesis is to facilitate the understanding of cascading failure and blackouts triggered by multi-component attacks, and to support the decision making in the protection of a reliable and secure smart grid. In this work, a new definition of load is proposed by taking power flow into consideration in comparison with the load definition based on degree or network connectivity. Unsupervised learning techniques (e.g., K-means algorithm and self-organizing map (SOM)) are introduced to find the vulnerable nodes and performance comparison is done with traditional load based attack strategy. Second, an electrical distance approach is introduced to find the vulnerable branches during contingencies. A new network structure different than the original topological structure is formed based on impedance matrix which is referred as electrical structure. This structure is pruned to make it size compatible with the topological structure and the common branches between the two different structures are observed during contingency analysis experiments. Simulation results for single and multiple contingencies have been reported and the violation of line limits during single and multiple outages are observed for vulnerability analysis. Finally, a cyber-physical power system (CPS) testbed is introduced as an accurate cyber-physical environment in order to observe the system behavior during malicious attacks and different disturbance scenarios. The application areas and architecture of proposed CPS testbed have been discussed in details. The testbed’s efficacy is then evaluated by conducting real-time cyber attacks and exploring the impact in a physical system. The possible mitigation strategies are suggested for defense against the attack and protect the system from being unstable

ASSESSMENT OF CREDIT RISK IN NEPALI COMMERCIAL BANKS

The main objective of the study is to identify the major indicators of credit risk among the Nepali commercial banks. The study is conducted using the sample of 15 commercial banks operated in Nepali economy. One way Fixed Effect Model (FEM) of panel data analysis is used as a major tool of analysis. All the data for the study were obtained from the database of Nepal Rastra Bank for bank specific variables and database of World Bank for macroeconomic variables for the year 2002/03 to 2014/15. The credit risk among the commercial banks in Nepal was regressed on bank specific variables such as liquidity, capital adequacy ratio, bank size, and interest spread. Similarly, the effects of macro-economic variables such as GDP growth, rate of inflation and interbank interest rate were also examined along with bank specific variables in identifying credit risk in Nepali commercial banks. The study reveals that liquidity has the significant positive impact on credit risk in Nepali commercial banks. In contrast, capital adequacy ratio and interest spread have the significant negative impact on credit risk. The analysis further confirmed that bank size and interest spread both have no any clear direction of impact on credit risk. Moving towards the GDP growth, credit risk in Nepali commercial banks is negatively fluctuates with GDP growth, however, the statistics show the coefficients are insignificant at 5% level. Contrarily, Inter-bank interest rate has insignificant negative impact on credit risk in Nepali commercial banks

Ab initio Studies of Structure and Properties of Group-IV Monochalcogenide Monolayers

The goal of this dissertation is to study the structure of ferroelectric group-IV monochalcogenide monolayers (MMLs) and their material properties. This work also established a new buckled honeycomb phase of these monolayers. Chapter 1 serves as an introduction where the motivation for these studies is established. In chapter 2, I used eight different exchange-correlation functionals (XC) to study the structure of these 2D ferroelectrics and found that their properties are independent of the choice of XC functionals. These findings reveal that the ground-state ferroelectric unit cell can be described by only five independent parameters, whereas their paraelectric (square or rectangular) unit cells can be described by three or two independent variables. It is found that reducing the number of independent variables increases their energy barriers Jc (the energy difference among the ground state structure and the paraelectric ones). In chapter 3, 2D structural phase transformation of two-dimensional monochalcogenides have been discussed through ab initio molecular dynamics and a 2D discrete clock model on the basis of the SnSe monolayer. Group-IV monochalcogenide monolayers undergo a two- dimensional phase transition from a ground state rectangular unit cell (threefold-coordinated structure) to a square unit cell (fivefold-coordinated structure) at a critical temperature Tc that is well below the melting point. Our DFT calculation shows a transition temperature Tc of about 1.42 Jc, where Jc is given in units of Kelvin per unit cell. In chapter 4, we established a new phase of MMLs with a buckled honeycomb structure. Its structural stability is discussed on the basis of three independent methods. Also, the out- of-plane intrinsic electric polarization and piezoelectric response of these buckled honeycomb structures are studied for the first time in this work

Impact of credit risk on profitability of commercial banks in Nepal

The main purpose of the study was to examine the impact of credit risk on profitability of the commercial banks in Nepal. Data were collected from the sample of 15 commercial banks operated in Nepali economy for the period of 2002/03 to 2014/15. One way Fixed Effect Model (FEM) of panel data analysis is used as a major tool of analysis. The profitability of the commercial banks is measured in terms of return on equity and is regressed on bank specific variables and macro-economic variables. The results confirmed that credit risk has the significant negative impact on profitability of commercial banks in Nepal. In addition, solvency ratio, interest spread rate, and inflation have the insignificant negative impact on profitability. In contrast, capital adequacy ratio, total assets, and GDP growth have the significant positive impact on profitability of commercial banks in Nepal. Finally, inter-bank interest rate has insignificant positive impact on profitability

Risk-based Probabilistic Quantification of Power Distribution System Operational Resilience

It is of growing concern to ensure the resilience in electricity infrastructure systems to extreme weather events with the help of appropriate hardening measures and new operational procedures. An effective mitigation strategy requires a quantitative metric for resilience that can not only model the impacts of the unseen catastrophic events for complex electric power distribution networks but also evaluate the potential improvements offered by different planning measures. In this paper, we propose probabilistic metrics to quantify the operational resilience of the electric power distribution systems to high-impact low-probability (HILP) events. Specifically, we define two risk-based measures: Value-at-Risk ($VaR_\alpha$) and Conditional Value-at-Risk ($CVaR_\alpha$) that measure resilience as the maximum loss of energy and conditional expectation of a loss of energy, respectively for the events beyond a prespecified risk threshold, $\alpha$. Next, we present a simulation-based framework to evaluate the proposed resilience metrics for different weather scenarios with the help of modified IEEE 37-bus and IEEE 123-bus system. The simulation approach is also extended to evaluate the impacts of different planning measures on the proposed resilience metrics.Comment: 12 pages, 11 figures, journa

3D 프린터를 이용한 미소수력 프로펠러 터빈 설계 및 생산

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 8. Sung-Hoon Ahn.제3세계 발전도상 나라에는 빈곤한 고립지역이 많이 있는데 이런 지역에는 기초시설도 많이 낙후하고 인구도 아주 희박하다. 후진 기초시설로 인한 국가 송전선망의 증축이 어렵지만 낮은 수원이 많기에 피코/마이크로 수력발전이 에너지 생산의 메인 옵션으로 활용될 수 있다. 그렇지만 피코/마이크로 수력발전 시스템을 구현하는데 있어서 터빈기술의 생산비용은 개발도상 나라들한테 아주 큰 병목중의 하나로 되고 있다. 터빈 제작에 필요한 비용을 줄이고자 본 연구에서는 3차원 프린터 기술을 응용하여 터빈을 제작하려고 한다. 3차원 프린터는 적절한 형상의 소형 터빈을 제작할 수 있으며 이는 이론적 효율과 매칭할 수 있게 된다. 때문에 3차원 프린터를 이용하여 발전소자를 제작하고 발전도상국가에서 조립하여 사용하게 되면 엄청난 비용을 절감시킬 수 있다. 본 연구의 목적은 2.5m높이와 30lps 유량으로 300W의 전력을 제공할 수 있는 저비용 프로펠러 터빈을 설계하고 제작하는 것이며 300W의 전력은 제3세계 발전도상 국가에서 한 가족의 전력 소비를 충분히 만족시킬 수 있다Abstract i List of Tables v List of Figures vi CHAPTER -1 1 INTRODUCTION 1 1.1 Background and motivation 1 1.2 Objective 2 CHAPTER- 2 3 HYDRO TURBINES FOR PICO HYDRO APPLICATIONS 3 2.1 Hydro turbine classification 4 2.1.1 Impulse turbine 4 2.1.2 Reaction turbine 5 2.2 Turbine selection criteria 7 CHAPTER -3 9 DESIGN OF PICO PROPELLER TURBINE 9 3.1 Design parameters 9 3.2 Turbine selection 10 3.3 Runner design 11 3.4 Design velocity diagrams 12 3.4.1 Forces acting on blade 18 3.5 Stator design 19 3.6 Casing/ housing design 19 3.7 Draft tube design 20 CHAPTER - 4 21 EXPERIMENT, RESULTS AND MANUFACTURING STRATEGIES 21 4.1 Simulation 21 4.2 Efficiency 21 4.3 Static Analysis of 3D printed turbine 23 4.4 Manufacturing strategies for 3D printed turbine 24 4.5 Installation 27 4.6 Advantages of 3D Printed turbines 28 4.7 Limitations of the 3D printed design 28 4.8Economics of 3D printed pico hydro turbine 29 CHAPTER 5 31 CONCLUSION AND RECOMMENDATION 31 5.1 Conclusion 31 5.2 Recommendation 31 Bibliography 32 초록 36Maste

Analysis of agricultural growth and its determinant factors in Nepal

This paper critically analyzes the trajectory of agricultural growth and its determinants in Nepal. Agricultural growth is vital for stimulating overall economic growth. The World Bank research shows strong statistical link between agricultural and overall economic growth in less developed countries. Economic growth and agricultural growth in Nepal also show strong correlation (r = 0.7501***). Agricultural transformation is characterized by declining share of agriculture in national employment and GDP, and increasing share of secondary sectors like industry, service and manufacturing. However, this structural shift seems unplanned and ungoverned in case of Nepal. The contribution of agriculture to GDP is continuously declining, but, the growth of secondary sectors likes industry and manufacturing still looks stagnant. At this incipient stage of agricultural transformation, productivity growth in agriculture is both a necessary as well as sufficient condition for the development of economy as a whole. Agricultural growth depends on institutional (agricultural credit and land holdings), infrastructural (irrigated area, farm mechanization, electricity, storage, transportation, agricultural market), technological (high yielding varieties or improved seed, fertilizers and pesticides) and socioeconomic factors (population, poverty and literacy). Policies strengthening these determinants can help Nepal in achieving targeted sustained economic growth