Due to the globalization of electric power technology, international standard becomes more and more important because international standard such as IEC standard is typical international standard and recognized as most wide-spread standard. In this paper, recently revised IEC standard 60505 for thermal endurance test method of electrical insulation system is explained as one of the most basic test methods of electrical insulating materials under electrical, thermal, mechanical and environmental stress.

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New small-scale dispersed generation systems, such as fuel cells and micro gas-turbines have made remarkable advances lately and they will be applied practically in the near future. Although a large number of researches on the introduction of small-scale dispersed generation systems have been carried out, only a small number of small-scale dispersed generation systems are considered in these researches. Therefore, little is known about problems to be solved in case where a large number of small-scale dispersed generation systems are introduced into electric power systems. This paper deals with a super distributed energy system that consists of a great number of dispersed generation systems such as fuel cells, micro gas turbines and so on. The behavior of a customer with a dispersed generation system is simulated as the Ising model in statistical mechanics. The necessity of a distribution network in super distributed energy systems is discussed based on the Ising model. The feasibility of decentralized autonomous control using vicinity information is also investigated on the basis of stability analysis of the Hopfield neural network model.

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We evaluate total energy consumption and CO₂ emissions in the phase of the city gas utilization system from obtaining raw materials to consuming the product. First, we develop a simulation model which calculates CO₂ emissions for monthly and hourly demands of electricity, heats for air conditioning and hot-water in a typical hospital. Under the given standard capacity and operating time of CGS, energy consumption in the equipments is calculated in detail considering the partial load efficiency and the control by the temperature of exhaust heat. Then, we explored the optimal size and operation of city gas system that minimizes the life cycle CO₂ emissions or total cost. The cost-effectiveness is compared between conventional co-generation, solar heat system, and hybrid co-generation utilizing solar heat. We formulate a problem of mixed integer programming that includes integral parameters that express the state of system devices such as on/off of switches. As a result of optimization, the hybrid co-generation can reduce annual CO₂ emissions by forty-three percent compared with the system without co-generation. Sensitivity for the scale of CGS on CO₂ reduction and cost is also analyzed.

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In case of analyzing power system by numerical calculation for power flow and transient stability, it is very useful to make a power system diagram to ease the modification and the change of data for system analysis. However, making the system diagram has been so far done by man power. It not only takes a lot of time to make a drawing for large-scale power system, it but also may cause a mistake. This paper proposes a supporting system for drawing the system diagram by applying a method for the automatic placement of nodes using genetic algorithm.
We construct a prototype system available for not only automatic drawing but also editing and modifying diagrams. In addition, since we assume that the proposed system utilizes computation resources on Internet, the proposed system is expected to run on different operating systems through graphical user interface (GUI). To realize this, a prototype system is developed by JAVA language and is designed by design pattern technique that enables to record, reuse, and represent recurring design structures and associated design experience.

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This paper proposes a mechanism for clearance of line congestion and power flow control in a deregulated market environment. The mechanism applies penalties to the bilateral transactions that cause line congestion by increasing the prices of such transactions. The market regulates itself by redefining the transactions and checking again for violations, applying penalties if necessary and repeating the process until all the demand is satisfied without causing line congestion to the system. A bilateral transaction matrix (BTM) creation algorithm developed by the authors and a DC power flow program are integrated as parts of the market mechanism proposed in this paper. The congestion is cleared by the market participants when they reschedule their transactions. This mechanism is useful to study the effects of bilateral transactions on a power system and helps the Independent System Operator (ISO) to create rules and market mechanisms for line congestion clearance and power flow control.

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In order to realize a photovoltaic(PV) solar power system which is low cost and flexible on its installation, authors have studied on vertical installations of bifacial solar modules. Simulation studies and field tests were made to evaluate daily and yearly output energies when bifacial modules are vertically installed with various azimuth angles. It is clarified that the yearly generated energies by a vertically installed bifacial module is equivalent to that of a mono-facial module faced to the south with an optimum tilt, regardless the azimuth angles. According with the above results, some applications have been successfully demonstrated including a fence-integrated PV system and a pole mounted PV system.

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In recent years, various inexperienced events with uncertain factors, such as a competitive electricity market, tend to gradually take place surrounding the actual electric power industry. Towards the mid-21st century, most of these tendencies, keeping steady pace with global trends, will become more prominent and still widely increased in Japan. Under such a changing and ambiguous situation of these days, it is of great significance to establish a national view of the ideal electricity supply in the 21st century. To cope with the relevant technological problems from the standpoint of sustainable development is a challenging and timely task for today's power system engineers.
This paper provides fundamental requirements for the future adequate power system especially in terms of supply capability coordination between generation and transmission sectors. It is noted that a newly proposed concept of “System Margin” is utilized as an evaluation index for the effective use of existing system components. A numerical example incorporating the suggested ideas is then presented for a simple trunk power system model. Finally, concluding remarks are shortly summarized, and a few related considerations and further research study topics are also supplemented.

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In the large-scale factories like ironworks, many power electronic inverter loads exist, and these inverter loads are connected into ac systems by using rectifiers. On the other hand, DGs (Distributed Generators) such as photovoltaic generators and fuel cells, or ESSs (Energy Storage Systems) such as secondary batteries and SMESs (Superconducting Magnetic Energy Strages), which are dc power sources will be introduced to distribution systems more and more. These are connected into ac systems by using inverters. Therefore, it is expected that some countermeasures to achieve a dc distribution system which can reduce power losses due to rectifiers and inverters, should be developed.
In this paper, a dc loop type distribution system is proposed as one of the new dc distribution system configurations. The calculation results of power losses for the dc loop type distribution system are compared with those for an ac distribution system. Moreover, this paper shows configurations and simulation results of the inverter, bi-directional rectifier and PFC (Power Factor Corrector) used in this system.

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This paper presents a systematic procedure of constructing a Lyapunov function for power system considering with induction machine dynamics characteristics by the state function method. Constructing Lyapunov function for power systems with induction machines is very difficult problem and is hoped for being settled for a long time. In the composition process of the proposed Lyapunov function, the slipping dynamic characteristic of the induction machine is implicitly expressed in the swing equation of power systems. As a result, the dynamic characteristic of an induction machine becomes equivalent to a synchronous machine with a voltage adjustment mechanism to which a dissipation function is added. Using this proposed system description, the Lyapunov function is composed by the state function method, which is based on an expanded energy function, under the condition of some approximations. The effectiveness of the proposed Lyapunov function is verified numerically for multi-machine power systems with induction machine loads.

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This paper describes an algorithm of making switching operation sequence for fault testing using tree structured data. When the faulty section is not isolated exactly, faulty section is tested whether the fault exist in the section by energizing. The proposed algorithm can determine appropriate order of components for fault testing and valid switching operation sequence for each fault testing. An example shows the effectiveness of the proposed algorithm. The proposed algorithm is used at actual control centers.

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When partial discharge occurs in high voltage apparatus, it may develop into its insulation degradation or its electrical breakdown. It is important to detect partial discharge with sufficient sensitivity especially from noisy background. This paper deals with the waveform processing technology by Daubechies wavelet transform to make relief of the partial discharge from a noisy signal. The partial discharge signal was measured in the coaxial electrode arrangement with a metallic needle attached on the high voltage central electrode. By choosing suitably the Daubechies order and its level applied to the measured data, it has been demonstrated that the noise signal is reduced and the partial discharge signal is relieved with sufficient sensitivity.

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Fault current limiters (FCLs) are devices for to suppress current in electric power system. The FCL is extensively expected to suppress fault current, particularly required for trunk power systems heavily connected high-voltage transmission lines, such as 500 kV class power system. For this reason, FCLs based on various principles of operation have been developed. Most of the FCLs under development which employ superconductors are based on the quenching phenomenon peculiar to the superconducting state, that is, making use of a rapid transition to normal conducting state, an electrical resistance appears, and this resistance is used to suppress fault currents. However, this elevation of resistance, although increasing the fault current suppression effect, also tend to raise the overvoltage occurring FCL, the ascertainment of the overvoltage is important as regards the protection of the FCL as well as other power system devices.
Hence the waveform created in the FCL was simulated in detail by the time varying resistance model which constitutes one of the analytical functions of EMTP, thereby analyzing the overvoltage and power system stability when the superconducting FCL is introduced into an actual power system.

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A blast pressure analysis program for gas circuit breaker taking ablation, arc energy and decomposition effect into consideration was developed. In general, it is well known that SF₆ gas accompanies dissociation and ionization in high temperature region, so we cannot apply the equation of state of ideal gas to high temperature region. Thus, it is necessary that the rate of specific heat, specific heat at constant pressure and gas constant are dealt with functions of gas pressure and temperature when SF₆ arc and/or high temperature SF₆ gas calculates.
In this paper, first, we evaluated the decomposition gas model by comparing Pressure-Temperature (P-T) characteristic calculated by the decomposition gas model with P-T characteristic that derived by the summing partial pressures of all dissociated chemical species. Next, using its calculation method, we calculated pressure analysis in gas circuit breaker. Finally, we compared theoretical value was calculated by this program with experimental value tested in 145kV, 40kA class gas circuit breaker. As a result of this simulation, theoretical analysis agreed very well with experimental results.

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Various models for the equivalent circuit of EDLC (Electric Double Layer Capacitor) have been presented so far. The multi-stage connection of RC circuit is a representative model to simulate the EDLC's charge-discharge characteristic. However, since high energy density type EDLC for electric power storage has the electrostatic capacity of thousands F, the phenomenon of being almost uninfluential for the case of conventional capacitor appears in an actual measurement notably. To overcome this difficulty, we develop an equivalent circuit model using a nonlinear model that considers the voltage dependency of the electrostatic capacity in this paper. After various simulations and comparison with experimental results, we confirmed the effectiveness of the proposed model.

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