• Computers and Concrete
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• v.29 no.4
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• pp.209-217
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• 2022

In order to analyze the static and dynamic structural characteristics of the Obermeyer gate under overflow conditions, the force characteristics and vibration characteristics of the shield plate structure are studied based on the fluid-solid coupling theory. In this paper, the effects of the flow rate, airbag pressure and overflow water level on the structural performance of shield plate of air shield dam are explored through the method of controlling variables. The results show that the maximum equivalent stress and total deformation of the shield plate decrease first and then increase with the flow velocity. In addition, they are positively correlated with the airbag pressure. What's more, we find that the maximum equivalent stress of the shield plate decreases first and then increases with the overflow water level, and the total deformation of the shield plate decreases with the overflow water level. What's more importantly, the natural frequency of the shield structure of the Obermeyer gate is concentrated at 50 Hz and 100 Hz, so there is still the possibility of resonance. Once the resonance occurs, the free edge of the shield vibrates back and forth. This work may provide a theoretical reference for the safe and stable operation of the shield of the Obermeyer gate.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.567-576
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• 2021

Climate change threatens the security of domestic water resources in South Korea. To overcome the potential water shortage, various approaches are being studied by alterning the operation of dams or by integrated operation of multiple dams and reservoirs. However, most of the related researches were developed and applied for multi-purpose dams, and few studies were conducted for the hydropower dams. The main purpose of the hydropower dam is to generate electric energy; however, the potential water shortage due to prolonged droughts brings the idea to supply water from the hydropower dam in the basin. To that end, it is required to estimate the water supply ability of the hydropower dams. In this study, we proposed a methodology to classify the hydropower dam into a "storage-type" and "run-of-river type" dam. The proposed approach was demonstrated using the hydropower dams located in North-han River basin. The results of this study are expected to contribute for further analysis of the hydropower dams, such as evaluation of water supply capacity and drought mitigation purpose operation of the hydropower dams.

• Journal of Korea Water Resources Association
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• v.55 no.7
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• pp.505-513
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• 2022

Recently, uncertainty in predicting available water resources is gradually increasing due to climate change and extreme weather conditions. Social interest in water management such as flood and drought prevention is also increasing, and after the unification of water management implemented in 2018, domestic water management is facing a major turning point. As part of such strengthening of water management capabilities, various studies are being conducted to utilize a hydropower dam for flood control and water supply purposes, which was mainly operated for hydroelectric power generation. However, since the dam evaluation methods developed based on a multi-purpose dam are being applied to hydropower dams, an additional evaluation approach that can consider the characteristics of hydropower dams is required. In this study, a new water supply capacity evaluation method is presented in consideration of the operational characteristics of hydropower dams in terms of water supply, and a connected reservoir simulation method is proposed to evaluate the comprehensive water supply capacity of a dam group operating in a river basin. The presented method was applied to the hydropower dams located in the Bukhan River basin, and the results of the water supply yield of individual dams and multi-reservoir systems were compared and analyzed. In the future, the role of hydropower dams for water supply during drought is expected to become more important, and this study can be used for sustainable domestic water management research using hydropower dams.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.2
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• pp.53-60
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• 2011

This study was conducted to investigate the effect of hydropower factors (watershed, gross head), operation ratio and unit electricity cost on the benefit-cost ratio (B/C ratio) of small hydropower using agricultural reservoirs. The equation of B/C ratio was expressed as a function of watershed area, gross head, operation ratio and unit electricity cost. The benefit increased with watershed area, gross head and unit electricity cost, while the cost increased with watershed area and gross head but decreased with operation ratio. The B/C ratio increased with watershed area, gross head, operation ratio and unit electricity cost. While the effect of gross head on the B/C ratio decreased with watershed area, the effect of operation ratio and unit electricity cost on the B/C ratio increased with watershed area. The operation ratio is an important factor to affect the B/C ratio and therefore we need to develop hydropower for the heightened dams to expect high operation ratio due to continuous water release. The unit electricity cost is also an important factor to affect the B/C ratio and the B/C ratio was always below 1 unless unit electricity cost is over 60 Won/kWh under given conditions. The reservoirs with economic feasibility for small hydropower development were three in 21 when the equation of B/C ratio was appled to the study reservoirs. The results can be used to choose the appropriate reservoir with economic feasibility for development of small hydropower.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.219-219
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• 2015

Hwacheon Reservoir is one of the reservoirs, which are located on the North Han River in South Korea. Construction of this reservoir was started in 1939 and completed in 1944. At the upstream of this reservoir there are Peace Reservoir, which is located in South Korea and Imnam Reservoir, which is located in North Korea. After construction of Imnam Reservoir, inflow regularity of Hwacheon Reservoir was changed and inflow of Hwacheon Reservoir also, was decreased. Peace Reservoir is used to decrease flood and damage at downstream due to unexpected release from Imnam Reservoir. This reservoir also, has a special role to regulate inflow of Hwacheon Reservoir. Hwacheon Reservoir has an important role for hydropower generation and flood control. Capacity and maximum discharge capacity of Hwacheon Reservoir are 1018 million $m^3$ and $9500m^3/s$, respectively. This reservoir has four generators to produce power and it is one of the important reservoirs for hydropower generation in South Korea. Due to the important role of this reservoir in generating power, maximization of hydropower generation of this reservoir is important and necessary. For this purpose, HEC-ResPRM model was applied in this study. HEC-ResPRM is a useful and applicable model to operate reservoirs and it gives optimal value for release to maximize power by minimizing penalty functions. In this study, after running the model, amount of release was optimized and hydropower generation was maximized by allocating more water for hydropower release instead of spillway release. Also, the model increased release in dry period from October to June to prevent high amount of release in flood season from July to September.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.63-65
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• 2007

Recently with increase consumption of electric power, the scale of the electric system becomes bigger and complex. Then, it is increasing the hardship in the operation of electric system and the continuance of stability. Especially, as the differences between demand and supply in electric power keeping low frequency oscillating attenuation from electric power have been very important in the continuance part of stability. The more control time of electricity system is getting faster with digitalization the more stability of electricity system is getting worse. As solutions of these problems, by establishing Power System Stabilizing Controller putting PSS output signal and putting damping to vibration of the rotor at generators's AVR in area where is oscillated, We are willing to contribute the electricity system by holding in generator output vibration.

• Steel and Composite Structures
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• v.36 no.5
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• pp.521-531
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• 2020

The behavior variation of concrete dam is investigated, based on a new method for analyzing the data model of concrete dam in service process for the limitation of wavelet transform for solving concrete dam service process model. The study takes into account the time and position of behavior change during the process of concrete dam service. There is no dependence on the effect quantity for overcoming the shortcomings of the traditional identification method. The panel data model is firstly proposed for analyzing the behavior change of composite concrete dam. The change-point theory is used to identify whether the behavior of concrete dams changes during service. The phase space reconstruction technique is used to reconstruct the phase plane of the trend effect component. The time dimension method is used to solve the construction of multi-transformation model of composite panel data. An existing 76.3-m-high dam is used to investigate some key issues on the behavior change. Emphasis is placed on conversion time and location for three time periods consistent with the practical analysis report for evaluating the validity of the analysis method of the behavior variation of concrete dams presented in this paper.

• Computers and Concrete
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• v.15 no.4
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• pp.485-501
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• 2015

Cooling by the flow of water through an embedded cooling pipe has become a common and effective artificial thermal control measure for massive concrete structures. However, an extreme thermal gradient induces significant thermal stress, resulting in thermal cracking. Using a mesoscopic finite-element (FE) mesh, three-phase composites of concrete namely aggregate, mortar matrix and interfacial transition zone (ITZ) are modeled. An equivalent probabilistic model is presented for failure study of concrete by assuming that the material properties conform to the Weibull distribution law. Meanwhile, the correlation coefficient introduced by the statistical method is incorporated into the Weibull distribution formula. Subsequently, a series of numerical analyses are used for investigating the influence of the correlation coefficient on tensile strength and the failure process of concrete based on the equivalent probabilistic model. Finally, as an engineering application, damage and failure behavior of concrete cracks induced by a water-cooling pipe are analyzed in-depth by the presented model. Results show that the random distribution of concrete mechanical parameters and the temperature gradient near water-cooling pipe have a significant influence on the pattern and failure progress of temperature-induced micro-cracking in concrete.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.151-151
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• 2021

The alarming climate change impacts are demanding the use of renewable energy sources like never before. Hydropower is one of the most cost-effective and environmental friendly energy technology recognized in the world. Big hydropower projects come up with the requirements of huge investment costs along with environmental impacts, whereas small hydropower(SHP) are considered a best solution for the economical source of energy. SHP, basically Run-of-River (RoR) type plants can be sustainable renewable energy sources and given the nature of perennial rivers flowing from steep gradient and rugged topography, feasibility of such plants is equally high in Nepal. The objective of this study is to determine the primary potential sites for the development of RoR type SHP sites using Geo-spatial Information System(GSIS). The use of GSIS enables precise survey of large area within a short period of time. This study has focused on the determination of locations by establishing defined criterions and methodologies and hence have located multiple locations rather than selecting one best location. The approach is applicable for the rapid initial screening of potential locations and results can facilitate detail feasibility study for the technical and economic analysis of SHP in the basin.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.635-636
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• 2005