We have developed new vegetable based insulating oil for transformers called PFAE (Palm Fatty Acid Ester). PFAE has 0.6 times less viscosity and 1.3 times higher dielectric constant compared to mineral oil. The oxidative stability, biodegradability and acute toxicity to fish of PFAE has also been determined to be superior to mineral oil. In this paper, in order to optimize the characteristics of fatty acid esters originating from palm oil, several kinds of fatty acid alkyl esters were first synthesized in the laboratory by the molecular design technique and the transesterification from fatty acid methyl esters and alkyl alcohols. Next the electro-chemical characteristics of the fatty acid alkyl esters as insulating oil were analyzed.

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The Electro Magnetic Transients Program (EMTP) is originated from the Ph. D. thesis of H. W. Dommel supervised by Prof. Prinz in 1962 at the Technical University of Munick. This article describes why and how the EMTP was developed in the Bonneville Power Administration, US Department of Interia (Department of Energy since 1978). Also some stories behind the EMTP in the early stage of its development are described, as the author being involved in a transient simulation since 1965 and being one of original EMTP developers.

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This paper proposes a method for solving radial distribution system planning problems taking into account geographical information. The proposed method can automatically determine appropriate location and size of a substation, routing of feeders, and sizes of conductors while satisfying all constraints, i.e. technical constraints (voltage drop and thermal limit) and geographical constraints (obstacle, existing infrastructure, and high-cost passages). Sequential quadratic programming (SQP) and minimum path algorithm (MPA) are applied to solve the planning problem based on net price value (NPV) consideration. In addition this method integrates planner's experience and optimization process to achieve an appropriate practical solution. The proposed method has been tested with an actual distribution system, from which the results indicate that it can provide satisfactory plans.

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A fault that occurs in a power system will cause loss of synchronism between two groups of generators and may result in a wide area blackout. A modified method is proposed to predict the loss of synchronism. The method uses power, current and voltage measured on a line that is linking two sub-networks to which groups of generators swinging coherently are connected. A state diagram is used to estimate a region and a direction of movement on the power angle curve where the operating point of the power system exists. The state diagram is defined as follows. First, the power angle curve is separated into several regions such as a region on the left side of the curve, a region between a point where power becomes the maximum and the unstable equilibrium point that is termed UEP on the right side of the curve and so on. Second, the state diagram is defined that represents the regions and the moving directions of the operating point on the curve where an operating point exists. Then, by using the state diagram and the measured values of power, current and voltage, an operating point can be traced on the curve and loss of synchronism will be predicted by detecting that the operating point exceeds UEP. The East 10 model of IEEJ was used for verification of this method. Several simulations were studied including cases of loss of synchronism after multiple swings.

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Optimization of diesel generators (DGs) and renewable energy sources have to be done within a cost-benefit, high reliability and environmentally friendly framework. Most of the optimization methods just consider only the economical point of view. This paper presents complete optimization method involving of cost, reliability and pollutant emission into optimization process. The reliability level is analyzed using basic probabilistic concept in order to find loss of load probability (LOLP). This value is then used to determine the customer damage cost due to electricity interruption. Meanwhile, CO₂ emission as an indicator of pollution is calculated to determine the annual emission cost (AEC). By considering both reliability level and CO₂ emission, the optimization results do not just show economic merit but will satisfy both of reliability level and environmental issue.

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The report modeled an electricity interchange trade by a PPS (Power Producer and Supplier) and a cogeneration, and evaluated the interchange trade using the numerical example. The PPS and the CGS user behave economically themselves in the model. It is new that not an electric power company but PPS trades the surplus electric power.
From the numerical example, the effect of electricity price and gas prices is different between commercial sector and industrial sector when maximizing the PPS profits. An electricity interchange gives profits to three groups (the PPS, the CGS user, and the unspecified general user) who participate in trades. However, it was shown that the PPS cannot gain only few portions of the whole interchange profits although the PPS determines the purchase price for the CGS user.

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This paper deals with large-scale 3D non-linear magnetostatic analysis by Hierarchical Domain Decomposition Method (HDDM). In magnetostatic numerical analysis, the computational object is always made in a complicated way at a large scale, and computational time is always very large. But, with the development of computational capabilities, it is now possible to focus our attention on the computational time without worrying about the amount of memory. In this paper, we reexamine the solution strategy for Finite Element Analysis (FEA) in the subdomain problem. Because the equation is singular, it has been solved by the CG (Conjugate Gradient) method in past researches. To solve it by the direct method, we introduce the A-p method into the subdomain problem. In this method we can expect to analyze more complex objects in relatively short time.

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Large-scale 40-Ah Li-ion cells have been developed for use in industrial applications. To contribute to techniques for ascertaining the state of these cells and detecting deterioration during actual use, we produce a cell whose capacity is reduced by trickle charging at high temperature, and we determine the relationship between the cell's properties such as its capacity and charging/discharging characteristics when the capacity is reduced. When the capacity of a Li-ion cell is reduced, the discharge voltage also decreases. We show that the residual capacity is well correlated to the discharge voltage and to the duration of continuous discharge before reaching a fixed end-voltage. We also show that the constant-current constant-voltage charging characteristics are maintained even when the capacity is degraded, and that the constant-current charging time and discharge voltage are closely related to the residual capacity. We confirm that the reaction coefficient of the capacity degradation formula can be calculated from the capacity change characteristics at multiple temperatures, and that an 8°C change in temperature causes the lifetime to decrease by half.

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This paper shows the investigation results on the change of lightning damages of home electric appliances, which has been done 4 times from 1987 through 2006. The rate of damaged households out of monitors (%/household/year) was around 0.6% in 1980's as well as 1990's. On the other hand, it is over 2% in 2006, when the society has become the fully developed information one. The rapid increase of lightning damages is attributed to the wide spread of home electric appliances with wires for telecommunication such as personal computers, new type telephones and facsimile machines as well as those with grounding wires such as water heaters.

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In order to maintain system voltage within the optimal range and prevent voltage instability phenomena before they occur, a variety of phase modifying equipment is installed in optimal locations throughout the power system network and a variety of methods of voltage reactive control are employed. In this paper, the voltage reactive control problem is considered as the two sub problems such as voltage control and reactive power control. The proposed multi-agent system intends to resolve the reactive power control sub problem. In this system, three types of agents are installed in substations in order to maintain the primary bus voltage within the operation limit by allocating the reactive power.
In order to verify the performance of the proposed method, it has been applied to the model network system. The simulation results show that the proposed method is a promising approach to keep the primary bus voltage within the operational limit by changing the reactive power allocation.

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Lightning protection of wind power generation is becoming an important public issue. Japan in particular suffers from frequent and heavy lightning strikes, such as the notorious “winter lightning” found in coastal areas of the Sea of Japan. Also, it is important to understand the “impedance characteristics” of wind turbine earthing systems from the viewpoint of lightning protection. A report from IEC, TR61400-24, recommends a “ring earth electrode”; however, this concept has not been fully clarified, especially its transient behavior during a lightning strike remains unresolved.
To confirm the effect of a ring earth electrode, this report presents an electromagnetic transient analysis on a foundation and ring earth electrode of a wind power generator using a Finite Difference Time Domain (FDTD) method. The results show that the ring earth electrode provides a low steady resistance with little inductive potential rise. Thus, it is confirmed that the ring earth electrode provides effective lightning protection of wind turbines.

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