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A Study on Transmission Replacement Plan Considering Multiple Supply Networks
Yasumura, Takumi,Tsuji, Takao,Oyama, Tsutomu,Hidaka, Kazuhiro,Koda, Jun,Seki, Tomomichi 대한전기학회 2012 The Journal of International Council on Electrical Vol.2 No.2
In recent years, Japanese electric power supply network equipments are almost at the end of their lifetime. It is an urgent necessity to manage their replacements[1]-[2]. In this paper, replacement planning approach for electric power supply network is studied based on the actual network model. The EENS (Expected Energy Not Supplied) is used as an index for reliability of supply network. The aging effect of equipments is also treated. It is assumed that the retransmission failure probability of single circuit fault is increased due to the aging of the equipments. In our previous papers, single supply network connected to one substation is examined[3]-[4]. On the contrary, multiple supply networks connected to different substations are examined in this paper. If the EENS of individual supply network is used for evaluation, the replacement plan may become too severe. However, evaluating the total EENS in multiple supply networks, the replacement plan becomes flexible.
A Study on Synchronous Stability Analysis of Power System with a Large Amount of PVs
Yoshida, Mitsutaka,Tsuji, Takao,Oyama, Tsutomu,Hashiguchi, Takuhei,Goda, Tadahiro,Kihara, Hidemi,Nomiyama, Fumitoshi,Suzuki, Naoto The Korean Institute of Electrical Engineers 2012 The Journal of International Council on Electrical Vol.2 No.2
To solve the energy and environmental issues, it is planned that a large amount of photovoltaics (PVs) are introduced in Japan. However, because the characteristic of PV output is different from that of conventional generators, it is possible that the synchronous stability changes due to a large amount of PVs. Additionally, supposing that some generators are stopped when PV output becomes large, decrease of inertia constant and change of power flow are also important factors for synchronous stability. Hence, in this paper, the synchronous stability of power system with a large amount of PVs is studied considering both the voltage characteristic of PV output and the change of system operation such as unit commitment. Specifically, the stability is evaluated from a viewpoint of critical clearing time (CCT) based on both the accelerating and decelerating energy in P-${\delta}$ curve. IEEJ-WEST10 model system is utilized as a simulation model.
Bae, Hyangryul,Tsuji, Takao,Oyama, Tsutomu The Korean Institute of Electrical Engineers 2014 The Journal of International Council on Electrical Vol.4 No.4
As an expected effectiveness in introducing micro-grid, there are possibilities that the micro-grid can improve the electrical power supply reliability. Specifically, micro-grid with islanded operation mode can continuously supply power to loads when a fault, such as large-scale power outage, occurs at the utility grid. When the range of the small scale network which can operate independently is planned in advance, it is easier for DGs (Distributed Generators) to design desirable autonomous operation in islanded state during a grid failure in the upstream network. Inversely, under the assumption that the range of the islanded system changes depending on the fault cases, the control logic should have any robustness. Hence, in this paper, to improve the power supply reliability in small-scale distribution systems, we studied the relationship between inverter control and stability of the islanded mode. Supposing that the inverter control is based on droop characteristics, its parameters have to be adjusted considering the equivalent impedance between the inverter and the center of inertia of the remained part of the system in order to realize the stable islanded operation in various fault cases.
Tsujita, Shinsuke,Shinji, Takao,Oyama, Tsutomu,Tsuji, Takao The Korean Institute of Electrical Engineers 2011 The Journal of International Council on Electrical Vol.1 No.3
Electric power systems, which include many renewable energy resources for worldwide low-carbon path, have a lot of problems and many studies are made for its solutions. Co-generation systems which consist of gas engine etc. have also been expected to make low-carbon path come true. One of difference between gas engines and renewable energy resources is their controllability. In this study, the operating reserve is considered as the ancillary service from distributed generator side. We have considered whether distributed generators are able to alternative thermal power plant when the peak demands. As the result, we have realized the generating cost of distributed generator possible to able to reduce against existing thermal power plant.
So-Young Kim,Sung-Hyuk Bang,Shunichi Honda,Takao Tsuji 대한예방치과학회 2012 International Journal of Clinical Preventive Denti Vol.8 No.1
Objective: Oral health and relative factors causing dental caries and periodontal disease for high students were examined in order to determine the correlations between each factor. Methods: 58 male students and 12 female students participated in this study through oral examination for caries and laboratory tests for GCF, the Snyder Test, salivary glucose measurements, and microscopic analysis of oral micro-organisms, and a correlation was derived between each factor. Results: The degree of caries formation was highly related to results from the Snyder Test, salivary glucose, a higher degree of oral moisture, and lower levels of GCF and DMF. There was no influence by oral micro-organisms causing caries directly in young adults except for the amount of filamentous type oral micro-organisms, and there was positive relationship between the amounts and motility for this type of micro-organism when compared to other types. There was a relationship between the salivary glucose and the amounts and motility of bacillus type micro-organisms. Otherwise, GCF was revealed to have a negative relationship with the motility of bacillus type oral micro-organisms. Conclusion: For high school students, modified Snyder Tests and salivary glucose checks are recommended to predict the formation of caries. Tests for GCF; and the amount and motility of bacillus, filamentous and spiral type micro-organisms, are recommended to predict the incidence of periodontal disease.