This paper discusses about the usefulness of a paper in power and energy society of IEEJ. The measure of the automobile industry is reported for this consideration. The automobile industry balanced competition and cooperation well and the author assumed that it made the usefulness of a research result easy to understand. This paper proposes that it should be required to activate the fundamental measure, which clarifies common recognition of the power and energy section.

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This paper discusses visualization methods of power systems to provide intuitive insight of static or dynamic behavior of power network, including a series of events to a blackout. Visualization study on power system has been getting attention among the researchers. Development of high performance computer system and software is addressing this research, which is spreading for both of static and dynamic studies, enables easy understanding of invisible phenomena in a generator or a network. So far, a table has been used to show the system condition, including voltage profile; real and reactive power flow distribution, phase angles, and these relationships. This paper discusses three examples of power network representations.

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This paper describes the new scheme to enhance data handling for deducing efforts on power system analysis. Generally, power systems are very large and containing great many power devices. Further more, conventional applications for power system analysis are developed individually and requiring complicated and different data format so that power system operators and planners are always forced heavy labor and widely experienced. To reduce efforts on power system analysis, it is necessary to increase efficiency of data handling. Many useful data handling schemes can be provided by the latest information technology (IT). In this paper, the example of applying graphical user interface, data base function and Python script to data handling for power system analysis will be introduced. These schemes are all installed in the power system analysis application package, named IMPACT.

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Three-phase voltage imbalance occurs by variety of connecting points of single-phase loads. In order to improve three-phase voltage imbalance, connecting points of single-phases loads are exchanged. System planner has to decide how to exchange connection of single-phase loads with the minimum planning cost in order to improve three-phase voltage imbalance. However, since there are many patterns of connection for single-phase loads, it is not easy to determine the optimal connection pattern for single-phase loads with the minimum planning cost under the constraint for improving voltage imbalance. In this paper, authors propose a computational method to support the planner's decision of single-phase loads connection systematically. The proposed method, which is based on effective enumeration algorithm, can obtain the optimal single-phase loads connection pattern, which satisfies with constraint of voltage balance and has the minimum total number of single-phase loads exchanged from previous single-phase loads connection. In the proposed method, three-phase iterative load flow calculation is applied to calculate rate of three-phase voltage imbalance. Three-phase iterative load flow calculation has two simple procedures: (Procedure1) addition of load currents from terminal node of feeder to root one, and (Procedure2) subtraction of voltage drop from root node of feeder to terminal one. In order to check the validity of the proposed method, numerical results are shown for a distribution system model with DG.

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It is said that the cogeneration system (CGS) is an effective countermeasure for energy saving and CO₂ reduction in the commercial building. However, the economic, energy and environmental efficiency of CGS varies so much depending on the annual load factor and the demand patterns of heat and electric power.
In this research, we develop a model to evaluate the optimum decision on the capacity and the operating pattern of CGS by nonlinear mixing integer programming in order to formulate the partial load properties of CGS in practical operation, since the existing optimization models without partial load properties could have generated too optimistic evaluation of CGS.
The compatibility between the economy and the energy saving of the CGS implementation planning has been the problem. Our system proposes a new measure to develop an optimal energy saving system under the constraint of economic efficiency as the investment recovery years of CGS for the commercial building. Our system has been applied to the case of hotel building. The results show us that the optimum CGS capacity planning generated by our model provides more effective solution compared to the existing simulation tools used generally without optimization capability.

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To use distribution networks effectively and to smooth introduction of the distributed generations, we proposed the loop or mesh structure for the distribution systems using loop power flow controller (LPC) at the opened switch which can connect the adjoining feeder. LPC is able to optimal control for distribution systems in the points of reducing voltage rise, voltage fluctuation and loss minimum power flow control, and so on, with acquisition of state of distribution systems. Adapting to the area that cannot use communication system, points of view at the power quality for the transition phenomena, we also required the distributed control using local voltage information for the LPC control. The purposes of this paper show a total power flow control structure of LPC and propose a determination method of control coefficients using object function that describe optimal condition of the network. The distributed control using control coefficients by proposed determination method shows suitable operation for disturbances of DG (distributed generator).

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To use distribution networks effectively and to smooth introduction of the distributed generations, we proposed the loop or mesh structure for the distribution systems using loop power flow controller (LPC) at the opened switch which can connect the adjoining feeder. LPC is able to take optimal control for distribution systems in the points of reducing voltage rise, voltage fluctuation and loss minimum power flow control, and so on, with acquisition of state of distribution systems. Adapting to the area that cannot use communication system, from the points of view at the power quality for the transition phenomena, the distributed control using local voltage information is required for the LPC control. The purposes of this paper to show power flow and reactive power control for LPC and to propose a determination method of control coefficients using optimal operation pattern and local voltage information of LPC. The distributed control using these control coefficients was verified by 6.6kV 100kVA BTB (back to back) type LPC and distribution system testing facility in CRIEPI.

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In this paper, the development and the performance of a viable distributed grid-connected power generation system of Photovoltaic-Energy Capacitor System (PV-ECS) considering solar energy estimation have been described. Instead of conventional battery Electric Double Layer Capacitors (EDLC) are used as storage device and Photovoltaic (PV) panel to generate power from solar energy. The system can generate power by PV, store energy when the demand of load is low and finally supply the stored energy to load during the period of peak demand. To realize the load leveling function properly the system will also buy power from grid line when load demand is high. Since, the power taken from grid line depends on the PV output power, a procedure has been suggested to estimate the PV output power by calculating solar radiation. In order to set the optimum value of the buy power, a simulation program has also been developed. Performance of the system has been studied for different load patterns in different weather conditions by using the estimated PV output power with the help of the simulation program.

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Using conventional high temperature superconducting wire, model Superconducting Fault Current Limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series of it. In parallel of these, a conventional reactor coil is connected. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil.

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Electric power systems in Japan are composed of remote and distributed location of generators and loads mainly concentrated in large demand areas. The structures having long distance transmission tend to produce heavy power flow with increasing electric power demand. In addition, some independent power producers (IPP) and power producer and suppliers (PPS) are participating in the power generation business, which makes power system dynamics more complex. However, there was little observation as a whole power system. In this paper the authors present a global monitoring system of power system dynamics by using the synchronized phasor measurement of demand side outlets. Phasor Measurement Units (PMU) are synchronized based on the global positioning system (GPS). The purpose of this paper is to show oscillation characteristics and methods for processing original data obtained from PMU after certain power system disturbances triggered by some accidents. This analysis resulted in the observation of the lowest and the second lowest frequency mode. The derivation of eigenvalue with two degree of freedom model brings a monitoring of two oscillation modes. Signal processing based on Wavelet analysis and simulation studies to illustrate the obtained phenomena are demonstrated in detail.

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Sulfur hexafluoride (SF₆) gas has become the most widely used gas insulator in high voltage equipment. But it has global warming effect. The search for alternative insulating gases is carried out all over the world. In order to use alternative gas for the circuit breaker, it is necessary to acquire the insulating property at high temperature. To study the property of insulating gases at high temperature, we use laser-produced plasma to simulate the arc discharge. The use of laser-produced plasma enables us to collect the experimental data easily via controlled eperiments. In this paper, we report the results of basic experiments carried out to verify the new experimental system. We have measured spark-over voltage, neutral gas density, and optical emission spectra of CO₂ and N₂. From the measurements, relationship among spark-over voltage, gas density, and temperature has been derived.

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In this paper we presented results of fundamental study to introduce the wavelet transform to vibration diagnosis for a turbine. It is required to detect typical vibration of the turbine accurately. The wavelet transform is used in many fields because it is able to visualize a phenomenon in a time-frequency domain. Modern power plants usually use one-high pressure and one or two lower pressure turbines. We made a turbine model with 3 rotors supported with journal bearings to simulate contact vibration, oil whip, and clearance vibration. The vibration phenomena were measured with vertical and horizontal displacement meters at the rotors, and with vertical and horizontal accelerometers at the bearings. The vibration phenomena were visualized in the time-frequency domain by the wavelet transform. This paper especially shows the results of the acceleration signals. It is found that the dynamic spectra obtained by the wavelet transform of the acceleration signals are different for each vibration. Therefore, this method is able to distinguish the vibration phenomena. And furthermore, the contact point is localized by the proposed method.

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The authors have previously proposed a transient simulation model of pole-mounted distribution transformers and its improved model that takes the skin effect of the secondary winding into account. However, the model has been validated only by laboratory tests with a low-voltage pulse generator. To show the accuracy of the model when used in a realistic situation, in this paper, field-test results using an actual-scale distribution line are presented. The following four cases are considered in the validation. Case1 (direct lightning hit is assumed): impulse current is injected into one phase of the high-voltage wires. Case2 (induced lightning is assumed): impulse current is injected into the bonded three phases of the high-voltage wires. Case3 (backflow lightning is assumed): impulse current is injected into the low-voltage neutral wire. Case4: the same conditions as Case1 except that surge-arrestors are installed for the transformer. All results obtained from the field test are compared with corresponding simulation results by considering the transient behavior of the grounding system. It is confirmed that the transformer model gives accurate results in the realistic situations.

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