The 19^th Power & Energy Society Annual Conference was held on September 24-26, 2008 at Hiroshima University. The total number of technical papers was 415 and 53 sessions (52 oral sessions and 1 poster session) were organized. A panel discussion, a special lecture, technical exhibitions and technical tours were also organized. All events were very well attended and the final enrollment attained to 954 registrations. The conference has been successfully closed by the great contribution of all participants. In this article, the outline of the conference is reported.

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The extra large diameter bundle conductors, which results in lower line inductance is one of the most cost effective methods to boost stable power transfer capability of a long bulk overhead transmission line. The Chubu electric power company co., inc. has developed a new technology that achieves a 6-conductor line of extra large bundle diameter whose conductor-to-conductor spacing is 120cm, that is practically maximum in stringing workability, and a unique tensioning method. This paper describes the process of determining design specifications that were established based on the results of galloping observations in the 500kV full-scale test line.

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This paper presents a new technique of waveform reconstruction method with CT (Current Transformer) saturation in power system. The authors have developed the method of waveform reconstruction using secondary current waveform of CT during a non-saturation. It is the method to identify variables of a mathematical model of primary current waveform of CT. We applied this technique to real current waveform in the fault of 66kV transmission line and confirmed the effectiveness. And we report the result that applied the proposed method to fault location of transmission line. In verification of fault location, we confirmed that the proposed method has improved fault location precision.

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This paper evaluates the economic impact of the introduction of customer-owned Thermal Storage Air-conditioning (TSA) systems, in an electricity market, from the viewpoint of the load service entity. We perform simulations on the condition that several thousand customers install TSA systems and shift peak demand in an electricity market by one percent. Our numerical results indicate that the purchase cost of the LSE was reduced through load management of customers with TSA systems. The introduction of TSA systems also reduced the volatility of market clearing price and reduced the whole-trade cost in an electricity market.

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The problem of recovery from power-system failures is the problem of handling operations that make it possible to supply power from other lines in response to power-system failures or construction by switching between the opened and closed states of sectionalizing switches. Considerable research has already been conducted with regard to this issue. This paper addresses the issue of determining target systems for final recovery in cases when some sections remain subject to power failure (i.e., sound bank capacity < load capacity). For this purpose, intersection is conducted only for parameters within such power-failure sections. In such research, calculations are implemented by setting a value of 2 to the sectionalizing switches of a single parameter. In addition, when the state of a sound section changes due to mutation improvements, the method of simultaneously changing the selected points and neighboring sectionalizing switches is applied. It is clear that the proposed method, consisting of conventional GA only, is superior in terms of average fitness values.

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In a deregulated environment, fairness and transparency to power system operation are required and it is necessary to give information on the appropriate transmission capability to transmission network users. In this paper, a novel evaluation method of available transfer capability, total transfer capability and power supply reliability margins, based on Monte Carlo Simulation considering system uncertainties, is presented. IEEJ WEST 10-machine system model is utilized to examine the effectiveness of the proposed method. The simulation result shows that the margins play a significant role in the determination of the ATC.

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Considering interconnection of a large-capacity of wind power generation to the utility grid, it is of great concern that its output power fluctuation has adverse influences, e.g. frequency fluctuation. There have so far been some research works on installation of battery energy storage systems (BESS), as a solution of these problems. However, owing to very high cost of the BESS, its capacity should be as small as possible. In this paper, not only the installation of the BESS as one of measures of suppressing the frequency fluctuation caused by wind power generation, but also blade pitch angle control for blunting the output power of wind turbine generators (WTGs) is also considered. This paper proposes a coordinated control method of the BESS and the blade pitch angle, and evaluates reduction of the capacity of the BESS and the power generation loss caused by blunting the output power which should be originally generated by WTGs.

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Verification test result of isolated operation of a microgird configured with some new energy generators on Aichi EXPO. 2005 showed stable controllability without rotating machine. However, improvement of voltage fluctuation with changing reactive power of loads had been hoped. Some improvements of system voltage control had been implemented on the maicrogrid moved to Central Japan Airport City. This paper presents a verification test result of the improvement of voltage fluctuation in isolated operation with PAFC output power compensation control by NaS batteries and also presents a simulation study of a further improvement of voltage control strategies of PAFC inverters.

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This paper presents an Improved Evolutionary Programming (IEP) for solving the Optimal Power Flow (OPF) problem, which is considered as a non-linear, non-smooth, and multimodal optimization problem in power system operation. The total generator fuel cost is regarded as an objective function to be minimized. The proposed method is an Evolutionary Programming (EP)-based algorithm with making use of various crossover techniques, normally applied in Real Coded Genetic Algorithm (RCGA). The effectiveness of the proposed approach is investigated on the IEEE 30-bus system with three different types of fuel cost functions; namely the quadratic cost curve, the piecewise quadratic cost curve, and the quadratic cost curve superimposed by sine component. These three cost curves represent the generator fuel cost functions with a simplified model and more accurate models of a combined-cycle generating unit and a thermal unit with value-point loading effect respectively. The OPF solutions by the proposed method and Pure Evolutionary Programming (PEP) are observed and compared. The simulation results indicate that IEP requires less computing time than PEP with better solutions in some cases. Moreover, the influences of important IEP parameters on the OPF solution are described in details.

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In recent years, it has been very important to adequately keep power qualities such as voltage and imbalance and so on. Especially the imbalance of voltage on distribution system may increase in the future by increasing electrified houses. Therefore it is necessary to decrease imbalance of voltage all the time in cooperation with electric power company and consumers. The high voltage consumers usually install static capacitors (SC) in order to improve power factor at receiving point. In this paper authors propose the method that these SCs in consumers are controlled in order to decrease the imbalance of voltage on distribution line. By the proposed method, single phase SCs are installed and the amounts of these SCs are decided in cooperation with several consumers that the proposed method is installed. The effect of the proposed method is confirmed by numerical simulation. Furthermore the effective scheme for introducing the proposed method to consumers is studied in this paper.

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Plug-in Hybrid Electric Vehicle (PHEV) is one of the technologies to reduce amount of CO₂ emissions in transport section. This paper presents one of the scenarios that shows how widely used the PHEVs will be in the future. And this paper also presents how amount of CO₂ will be reduced by the introduction of PHEVs, and whether there are any serious effects on power supply system in those scenarios.
PHEV can run with both gasoline and electricity. Therefore we evaluate CO₂ emissions not only from gasoline consumption but also from electricity consumption. To consider a distribution of daily-trip-distance is important for evaluating the economical merit and CO₂ emissions by introducing of PHEV. Also, the battery cost in the future is very important for making a PHEV's growth scenario. The growth of the number of PHEV makes battery cost lower. Then, we formulate the total model that combines passenger car sector and power supply sector with considering a distribution of daily-trip-distance and Learning Curve on battery costs. We use the iteration method to consider a Learning Curve that is non- linear. Therefore we set battery cost only in the first year of the simulation. Battery costs in the later year are calculated in the model. We focus on the 25-year time frame from 2010 in Japan, with divided in 5 terms (1st∼5th). And that model selects the most economical composition of car type and power sources.

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Two-pole large generators are extensively used in power utilities. Growing demand for electric power in recent years has led to substantial increases in the capacity of generators. To meet this trend, we have manufactured 2 pole turbine generators in 900,000kVA to 1,200,000kVA classes.
As the capacity of generators becomes larger, equivalent circuits are increasingly expected to improve their precision in estimating operation characteristics. Park model has been widely used as an equivalent circuit model. Park model with quadrature axis transient reactance x'_q is claimed to be useful for accurately estimating the load rejection characteristics of turbine generators. However it is difficult to measure the x'_q, few studies have been reportedly carried out based on measured data. As one of the few examples, we have conducted a measured data on a 500,000kVA class generator. Recently, the authors obtained the test data of x'_q of 900,000kVA class generator. In this study, based on these data, we studied the effect of x'_q, using the finite element method (FEM) and transient analysis program (EMTP-ATP).

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We propose a cooperative control system of gas engine generators and lead-acid battery in a microgrid. The control system enables a microgrid system to balance between electric power demand/supply and to control the state of charge (SOC) of the battery at the same time. To evaluate this control system, we simulated its performance in balancing the control of an experimental microgrid facility with two reciprocating engine generators for a day in which large fluctuation in PV and wind turbine output was observed. The capacity ratio of renewable energy installed in a microgrid can be increased beyond 50%.

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This paper describes an application of neural network for forecasting of the recession time constant of river flow rate into a dam after the rainfall. We proposed that the used data to forecast the recession time constant is classified by cluster analysis. A neural network system is developed through a case study on a dam for hydropower plant located the upper district of the Yahagi River in Central Japan. It is found from our investigations that the forecasted results of the recession time constant of river flow rate are improved by classifying the rainfalls based on cluster analysis.

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SOC (State of Charge) estimation based battery management is essential for HEV (Hybrid Electric Vehicle) applications. SOC can be estimated by the relationship between OCV (Open Circuit Voltage) and SOC, which is based on Nernst equation, in combination with coulomb counting. However voltage hysteresis and relaxation make the measurement of OCV difficult. Measured OCV after charge (discharge) is higher (lower) than estimated OCV by Nernst equation, and is slowly relaxed with time constant from few minutes to few hours. In this paper, to express voltage hysteresis and relaxation, three layers model concerning Nickel active materials is proposed. A voltage gap between surface and inside of Nickel active materials is introduced, and voltage hysteresis is modeled as surface partial battery decides OCV of the whole battery. Voltage relaxation is also expressed as equalization between surface layer and relaxation layer with higher internal resistance. The statical and dynamical behavior of proposed model is confirmed through the experiments of 7.2V 6.5Ah NiMH battery module.

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Low Harmonic Component Elimination Method that is one of the methods of PWM control is an effective method to the miniaturization of the filter, or the decrease of the loss by the decrease of the switching frequency. However, this method is only a specific usage like a Static Var Generator, because this method only can read the switching angle decided beforehand from the memory and only can control fundamental wave. In this paper a PWM method to control Low Harmonic Components is proposed. The proposed method use the curved triangle wave that was developed this time for the carrier wave. The proposed method turned out decreasing the total harmonic distortion more than conventional Low Harmonic Component Elimination Method and Subharmonic Method by some experimental results employing single phase inverter.

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We developed a power system stabilizer with an EDLC (electric double layer capacitor) that makes it possible to operate microgrids autonomously from utility grids, and to maintain the electric power quality in an islanded microgrid. This paper proposes two types of control systems that are composed of a PFC (power flow compensator) and a CVCF (constant voltage constant frequency) compensator. Installation locations of this system with the CVCF compensator are not limited by hardware requirements, and can maintain the quality of electricity in the islanded microgrid. Also, it is possible for the CVCF compensator to manage a dynamic load sharing function. Therefore, it is not always necessary for this equipment to have the central controller by using information networks. The EDLC is capable of charging and discharging stored electricity at a short cycle repetitively and has an advantage to keep a storage resource minimum to maintain the electric power quality. This paper shows specifications and verification results obtained by simulation studies and by demonstrating experiments of this equipment. In order to verify the practicability of the proposed control, these experiments were carried out in the microgrid that is supplying electric power to actual loads.

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Recently, with the dawn of the electric deregulation, the installation of distributed generation with power electronics device has grown. This current causes a greater concern of power quality, primarily voltage disturbance for power companies, and their interest in power quality is peaking. Utilities are also interested in keeping their customers satisfied, as well as keeping them on-line and creating more revenue for the utility. As a countermeasure against the above surroundings, a variety type of devices based on power electronics has been developed to protect customers' load from power line voltage disturbance. One of them is the series type voltage restore. The series device is an active device, designed to provide a pure sinusoidal load voltage at all times, correcting voltage disturbance. Series type device compensates for voltage anomalies by inserting the ‘missing’ voltage onto the line through insertion transformer and inverter. This paper shows the setting guideline of target level to compensate voltage disturbance, that is, voltage dip, voltage harmonics, voltage imbalance and voltage flicker, and the design approach of the prototype of series voltage restores to accomplish the required compensation level. The prototype system gives satisfactory compensation performance through evaluation tests, which confirm the validity and effectiveness of the system.

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Spatial distribution of lightning discharges that were observed simultaneously with faults of power transmission lines in Hokuriku area in winter is analyzed. Spatial distribution of all lightning discharges located by LLS in winter around the coastline of the Sea of Japan is analyzed as well for comparison. Majority of the transmission line faults experienced within about 20km from the coastline were associated with positive flashes. On the contrary, most of the faults located inland farther than about 20km from the coastline were associated with negative upward flashes. Distribution of located lightning flashes dependent on their polarities observed by LLS coincides with this pattern of lightning faults. Accordingly, the relationship between the lightning flash density observed by LLS and the frequencies of lightning hits on high structures in winter is examined. Based on this result, the lightning fault rate of 500kV transmission lines in winter is evaluated by using this relationship, resulting in successful reproduction of the high fault rate experienced so far.

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SF₆ is used as the main insulation gas for gas-insulated switchgear (GIS), but it has recently become a gas that must be restricted because of its greenhouse effect. To date, we have studied the insulation characteristics of compressed N₂ and CO₂ as a possible alternative for SF₆. We have reported that N₂ or CO₂ must be pressurized up to 2.0MPa when it is used as a substitute for SF₆ of 0.5MPa. Therefore, we have proposed a hybrid insulation composition that uses the gas and solid insulators. Because the central conductor of GIS is the covered by solid insulator in this composition, the high-pressure gas of 2.0MPa is not needed. However, the joint of the solid insulator becomes the weak point for discharge development. In this paper, we describe the effective configuration for the improvement of withstand voltage on the basis of the experiment. As a result, the most effective connector was made of resin without an implanted electrode and the configuration was the case without the solid-solid interface between the solid insulator of the central conductor and the resin connector. In this experiment, the improvement of the breakdown electric field of the hybrid composition was 44% or more compared with the case of only gas insulation (conventional method). In addition, a further improvement can be expected by optimizing the insulation creepage distance and configuration.

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Rationalization of the maintenance of gas-insulated equipment under operation and lifetime extension based on the results of appropriate diagnosis are necessary to reduce in the cost of gas-insulated equipment. Therefore, condition-based maintenance (CBM) is required and accurate methods for observing the inside of equipment is important. In this report, we describe a diagnosis method that can be used for actual gas-insulated equipment, such as to assess the deterioration of the spacer made by epoxy resin and to detect a loose connection in the central conductor. The principal results are summarized as follows:
(1) The quantity of decomposition gases depend on the moisture and magnitude of the partial discharge. However, decomposition gases were detected even if SF₆ has low moisture content (less than 100ppm) similar to that used in actual equipment. This means that our method can be applied to actual equipment.
(2) It became clear that CF₄ is a typical gas generated by partial discharge on the spacer surface. Therefore, it is possible to diagnose the deterioration of the spacer by monitoring the CF₄.
(3) The decomposition gases (SF₄, SO₂, SO₄, SO₂F₂) were generated by an impulse breakdown, which was assumed to be due to the repetition discharge caused by insulation failure and loose connection.
(4) SF₆ gas which is assumed the loose connection and was heated up from room temperature to 800 degrees C, and the generated decomposition gases were analyzed by FTIR in real time. As a result, the decomposition gases were generated at temperatures above approximately 500 degrees C in the heating time of 1.5 minutes. Therefore, a loose connection can be detected by analyzing the decomposition gas.

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The excessive input of phase-advanced capacitors by customers has been posing a problem to date. To cope with this problem, the installation of phase-advanced capacitors on the low voltage side was recommended, but does not presently seem to have produced the expected effect.
As a solution, a phase-advanced rectifier circuit, integrated from rectifier circuit built-in equipment and phase-advanced capacitor, is proposed and the effect of its introduction is discussed. This method is confirmed to be effective for the reduction of reactive power, because the receiving-end voltage and current waveform distortion are improved; in particular, the number of capacitors input into the system under light-load is reduced.

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In order to improve the reliability of electric power systems, it is important to reduce the malfunction of relay or the fault of low voltage control circuits in substation by switching and lightning surge. However, it is not enough that the study of intrusion of surge into the low voltage control circuits. We studied the terminal voltage of the control panel and analyzed the intrusion route of surge in substation.

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In this paper, we have shown that FDTD calculations for a conductor system having a radius smaller than 0.15Δs or larger than 0.65Δs (Δs is the lateral side length of cells employed), represented using arbitrary-radius-wire representation techniques proposed by Noda and Yokoyama, and Railton et al., with a time increment determined from the upper limit of Courant's stability condition, result in numerical instability. The reason for this numerical instability is that the speed of waves propagating outward in the radial direction from the wire in the immediate vicinity of the wire exceeds the speed of light, and therefore, Courant's condition is not satisfied there. Furthermore, we have improved the arbitrary-radius-wire representation proposed by Noda and Yokoyama. In representing a wire whose radius is smaller than the equivalent radius (r₀ =0.230Δs) using the improved technique, the permeability for calculating the axial magnetic field components closest to the wire and for calculating the circulating magnetic field components closest to and half cell away from the tip of the wire is modified in addition to the permeability and the permittivity for calculating the circulating magnetic field components and the radial electric field components, closest to the wire, respectively. In representing a wire whose radius is larger than r₀ using the technique, the permittivity for calculating the axial electric field components closest to the wire is modified in addition to the permittivity and the permeability for calculating the radial electric field components and the circulating magnetic field components, respectively. The improved technique is effective in representing a wire whose radius ranges from 0.0001Δs to 0.9Δs.

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Energy loss in transformer is composed of no-load loss and load loss. No-load loss of amorphous transformer (i.e. amorphous metal-based transformer) is less by about 70% compared with traditional transformers (e.g. silicon steel-based transformer). However, amorphous transformers have disadvantages of high cost and high load loss parameter compared with traditional transformers. Furthermore, there are varieties of transformer capacities, and the customers who would buy new transformer have many choices.
In this paper, the authors propose an algorithm for optimum transformer selection based on the load curve patterns of customers. It is possible to select the capacity that minimizes the total cost by measuring equivalent load Q_e that is the root mean square of load. It becomes clear that amorphous transformer is effective in achieving substantial energy saving compared with traditional transformer.

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Condition Based Maintenance (CBM) is a new maintenance strategy and interest of utilities for reliable operation of aged power equipments. Although CBM has been tried to apply for various equipments, since an affection of accuracies of condition information from sensor have not sufficiently discussed, specification of reliable information is still not clear and CBM has not widely applied in actual power substation. The affection of accuracies of condition information for the criteria of failure recognition is treated in this paper. Authors retrace to the potential—failure curve (P-F curve) in original Reliability Centered Maintenance (RCM) concept and explain the affection. The explanation is proved using comparison with original sensor for CBM and existing sensor in SF₆ gas slow leakage detection experiment. As a result of experiment SF₆ gas leakage less than 0.1%/year might be detected using CBM sensor. The authors concluded that special performances in sensitivity and long term stability of sensor are very important for reliable operation of power substation under CBM strategy.

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The influence of various compounds on the increase of the electrostatic charging tendency (ECT) in insulating oil was investigated. Sulfide compounds, which are contained in new mineral oil, are identified as original materials to increase the ECT for the first time. This is verified by heating tests of alkylbenzene with the addition of various compounds. Coexistence with copper and injection of oxygen enhance the increase of the ECT. Some of the sulfide and sulfoxide compounds increase ECT remarkably. On the other hand, the influence of sulfone, which is an oxide of sulfoxide, is negligible. Although sulfonic acid, which is the oxide of sulfone, remarkably increases ECT, the polarity is reverse. Thus ECT is influenced by the kinds and the molecular structures of additive sulfur compounds.
The influence of nitrogen compounds and that of oxygen compounds are confirmed smaller than that of sulfur compounds. Since the amount of nitrogen compounds and that of oxygen compounds are much smaller than that of sulfur compound in mineral insulating oils, the influence of these compounds is considered negligible.
Since ECT of the oil with the addition of sulfide or sulfoxide increases after the heating, the other compounds should be created from these compounds that increase ECT directly. Thus the increase of ECT is mostly caused by the oxidation of sulfide, which creates sulfoxide. Then certain compounds, which directly increase ECT, are created from sulfoxide. If sulfone or sulfonic acid is created by the oxidation of sulfoxide, ECT decreases because of the influence of these compounds on ECT. It is most likely that a certain process other than oxidation occurs at the creation of the compounds that increase the ECT directly.

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Both of the mechanism and the causing compound to increase the electrostatic charging tendency (ECT) of insulating oil was investigated by accelerated deterioration tests with the addition of various compounds. Although the ECT of the insulating oil was almost constant when only sulfoxide compounds were added, remarkable increase was observed when either of hydrochloric acid or moisture, which was considered to be generated by the aging of insulating oil, was further added to the oil containing sulfoxide compounds. It is presumed that sulfonium ion, which is generated by the reaction between sulfoxide compound and hydrogen ion, is the compound to directly contribute the increase in ECT. Hydrogen ion can be supplied from the organic acids, which is generated by the oxidation of hydrocarbon in aging insulating oil. It is considered that the increase in ECT of insulating oil is caused by the generation of sulfoxide by the oxidation of sulfide, which is contained in new oil (origin compound), and the generation of sulfonium ion from the reaction between sulfoxide and hydrogen ion, which is generated due to aging.

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This paper proposes the micro wind generator system for automobile. This proposes system is composed of the deflector, the micro windmill, the generator, and electric storage device. Then, the effectiveness is confirmed from an examination using air blower. Therefore, new energy can be expected to be obtained by installing this system in the truck.

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