The protection of wind turbine blades from lightning damages is increasingly important for an increase of wind power generation. This paper shows the manner of lightning damage of wind turbine blades and the difference between the blades made of various materials. Possible protection measures from lightning damages are shown for various types of wind turbine blades. Moreover we stress that protection of wind turbine blades from winter lightning damages is necessary for us to build wind power generators at the coast faced to the Sea of Japan.

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An adjustable speed generator has the capability of controlling easily its output power by secondary-excitation control system. It makes a contribution to increasing AFC (Auto Frequency Control) operation capacity on electric network, and makes it possible for the disturbance to be decreased rapidly when fault is occurred. In order to simulate such a response of the system in network transient analyzing program, we derived the system model which includes a circuit for excitation power supply, and analyzed the validity of the proposed model.

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An approach based on structured singular value theory is proposed for the design of robust load frequency controller in response to the new technical control demand for large scale power systems in a deregulated environment. In this approach the power system is considered under the pluralistic Load Frequency Control (LFC) scheme, as a collection of different control areas. Each control area can buy electric power from some generation companies to supply the area-load. The control area is responsible to perform its own LFC by buying enough power from pre-specified generation companies, which equipped with robust load frequency controller.
A three area power system example is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation.

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The liberalization of the electric power industries was executed from April 1998 in California State. Though this liberalization is suspended because of the extremely high bids and the outages, the information of the power price in the power exchange is very variable to investigate its structure and determination factor.
From the accessible web site, we obtained the every hour data of the zone prices and the whole demand of California from April 1998 to September 2001, under the deregulation of the electric power industry. We are analyzing the prices by the regression analysis. In this paper, we compose simple regression equations successfully to classify the price data into four time zones. Next, we analyze the prices from June to September 2000 when the price cap of the power price is changed twice. The Chow test shows that the structural changes in the power price are occurred when the price cap is changed. Thus we observe the determining factor of the electric power price by the regression analysis.

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This paper presents a fuzzy logic switching for the thyristor controlled braking resistor to damp turbine-generator shaft torsional oscillations. Following a major disturbance in electric power system, variable rotor speed of the generator is measured, and then the current through the braking resistor is controlled by the firing-angle of the thyristor switch which is controlled by the fuzzy logic. Thus the braking resistor controls the accelerating power in generators and damps the shaft torsional oscillations. The effects of the fault occurring time on turbine shaft torsional torques have also been investigated. Simulations are performed by using EMTP (Electro-Magnetic Transients Program). Through the simulation results of various multi-phase faults in a single machine connected to an infinite bus system, the effectiveness of the proposed fuzzy logic controlled braking resistor in damping shaft torsional oscillations is demonstrated.

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In this paper, we propose new nonlinear stability indices for multi-mode oscillations in power systems by using normal form analysis. One of the indices indicates the characteristics of damping factor with regard to its amplitude change, and the other indicates the stability region for each oscillation mode. We could obtain more detailed information on the stability of power systems by using the proposed indices together with eigenvalues in comparison with eigenvalue analysis. We show the validity of the proposed indices by numerical simulation in a multi-machine power system.

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This paper carries out the action confirmation test of a semiconducting-type fault current limiter (FCL) using the digital signal processor (DSP) to improve the instantaneous voltage drop and to reduce the fault current of power system. A insulated gate bipolar transistor (IGBT) is used as a commutation element of the FCL. The IGBT is a kind of the MOS-type gate power device. By using the IGBT, the high-speed operation of large current and high voltage can be realized. Next, the DSP is used in the FCL in order to detect the fault current at high speed. The DSP used in a test equipment is a starter kit (Texas Instrument TMS320C67). This is mainly used by the real-time processing, and it is suitable for the high-speed operation.
The examination was carried out using computer simulation and a test equipment of small capacity in order to demonstrate the effectiveness of the technique using in this paper. Three kinds of FCLs are used in this paper. One is a resisted type and another is a reactor type. One of the remainder is the Z type which parallelly connected resistance and reactor. From computer simulation using PSCAD/EMTDC and small-scale experiment, three kinds of fault current limiter used in this paper confirmed moving within 1 msec from the fault detection to the action completion.

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The data processing of the meteorological radar echoes was developed for the improvement of the forecast of the river flow rate. This paper describes an application of a neural network for estimating the runoff ratio from radar echo data. A neural network system for this purpose is developed through a case study on a dam for hydro-power plant located the upper district of the Yahagi River in Central Japan. We use the two types of neural networks; one of the types is for estimating the ground rainfall distribution from radar echo data and another one is for estimating the runoff ratio from estimated ground rainfall. It is found from our investigations that estimating accuracy of the runoff ratio is improved by utilization the radar echo data.

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High performance and real-time capability are very important for control systems including load dispatching office systems with energy management system (EMS) functions. Parallel computing and very large memory (VLM) introduced by general purpose symmetric multi-processor (SMP) computers are required to achieve high-performance computing for EMS applications. However, a performance decline was observed on concurrent execution of EMS applications in our early evaluation. VLM may cause non-preemption and I/O inversion problems that interfere with real-time processing.
The main issues addressed in this paper are: (1) adoption guidelines of SMP computers to achieve high performance and (2) design guidelines to realize real-time capability with VLM environment from practical points of view. The verification results show that performance can be improved by 2 times by selecting SMP computers appropriately and that real-time processing can be realized by the guidelines. The results of this study are used in the newly developed load dispatching office system that has been in practical operation.

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Output characteristics of amorphous silicon solar cell are known as the phenomenon which repeats degradation and recovery with solar light spectrum and temperature change, and it is remarkably controlled at insolation intensity and temperature. However, it has sufficiently and not yet clarified the relation between degradation and recovery by the temperature.
Here, it was confirmed to recover by the heat treatment, while the phenomenon was confirmed by the outdoor exposure test. From these results, exposure test equipment which stuck the warmth heat element in solar cell back surface was manufacture, and temperature effect method for the degradation control was proposed by the heating to the lowering stage of the temperature, and the effect was evaluated.

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This paper describes the effect of mutual leakage reactance in rotor circuit (Canay reactance) on analysis of medium capacity generator transient and dynamic behavior. The authors proposed the decision method of field mutual leakage reactance, and analyzed sudden short circuit and voltage dip on sudden load application by simulations using the electromagnetic transients program (ATP-EMTP) and compared the results with the experimental data.

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The suitable hybrid configuration of Darrieus lift-type and Savonius drag-type rotors for stand-alone wind turbine-generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up: Type-A installs the Savonius rotor inside the Darrieus rotor and Type-B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behaviors of the system operated at the maximum power coefficient points show that Type-A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational shaft, is an effective way for self-controlled stand-alone small-scale systems.

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Controlled switching system (CSS) with a 204kV gas circuit breaker (GCB) demonstrates to reduce an inrush current and to eliminate re-ignitions in shunt reactor switching. Target closing and opening instants for controlled switching are determined by the electrical and mechanical characteristics of GCB. Idle time dependence of the operating time, which gives a sufficient impact on controlling accuracy, is evaluated and successfully compensated by synchronous switching controller (SSC). Field operation of CSS for a year shows an effective suppression of inrush current on closing and prevention of re-ignitions on opening of shunt reactor. The operations also proved that the CSS has a satisfactory performance for electro-magnetic disturbance imposed in practical field.

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The on-line partial discharge testing has been used to provide useful information to diagnose and monitor the integrity of stator winding insulation of hydrogenerators. We are aiming for the establishment of a method of on-line diagnosis of insulation deterioration on hydrogenerator stator winding by acoustic emission (AE) detection method. We have developed a new AE measuring system that is controlled by output signal of hydrogenerator. In this paper, it was clarified that the insulation deterioration of hydrogenerator stator winding depended remarkably on the temperature of stator winding during a starting operation period.

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Many electric utilities world-wide have been forced to change their ways of doing business, from vertically integrated mechanisms to open market systems. We are facing urgent issues about how we design the structures of power market systems. In order to settle down these issues, many studies have been made with market models of various characteristics and regulations. The goal of modeling analysis is to enrich our understanding of fundamental process that may appear. However, there are many kinds of modeling methods. Each has drawback and advantage about validity and versatility.
This paper presents two kinds of methods to construct multi-agent market models. One is based on game theory and another is based on reinforcement learning. By comparing the results of the two methods, they can advance in validity and help us figure out potential problems in electricity markets which have oligopolistic generators, demand fluctuation and inelastic demand. Moreover, this model based on reinforcement learning enables us to consider characteristics peculiar to electricity markets which have plant unit characteristics, seasonable and hourly demand fluctuation, real-time regulation market and operating reserve market. This model figures out importance of the share of peak-load-plants and the way of designing operating reserve market.

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The authors perform numerical simulations for the whole region of single cell plate of planar solid oxide fuel cell. It is made clear that the maximum temperature in the cross-flow type cell is considerably higher than that in the co-flow and the counter-flow type cells. This is because the air flows along the high heat generation region near the fuel gas inlet in this type cell. The partial reverse of the fuel gas flow direction is most effective to reduce the maximum temperature in the cross-flow type cell, because this divides the high heat generation region and makes the gas temperature rise of each air channel uniform. The effect of uneven gas supply to each gas channel on cell performance is investigated, and it is made clear that its bad influence is very small. The influence of radiation heat transfer to and from its exterior is also examined in the case the cell is contained in a constant temperature vessel and is under the thermally self-sustaining operation, and its bad influence is turned out to be also small.

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Electrical characteristics of Air, CO₂, etc. are studied as candidate of substitute gas for SF₆. To evaluate their interruption capability as close as actual case the gas blasting with sonic velocity was applied. Authors have measured time constant (θ) and power loss coefficient (N₀). In this experiment, Air, He, CO₂, and SF₆ and gas mixture with SF₆ were varied. Among these gases it was found to be θ_SF6<θ_CO2<θ_air<θ_He and N_0SF6>N_0CO2>N_0air>N_0He, and it is understood that the arc extinction performance of CO₂ was excellent except for SF₆. Moreover, the time constant became large when the rate of SF₆ in mixture gas was reduced, and the power loss coefficient became small. Moreover, the simulation of the SLF interception by EMTP was performed using the obtained arc parameters of the various gases.

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Phenomena is presented whereby the performance of a dimethyl-ether fuel cell (DDFC) at 80°C is much lower when Pt-Ru catalyst is used on the anode than when Pt catalyst is used, in contrast to the higher performance achieved using Pt-Ru catalyst over Pt catalyst in direct methanol fuel cells (DMFC). The DDFC performance achieved using Pt-Ru catalyst increases with temperature and exceeds that using Pt catalyst at temperatures of over 100°C. After high temperature operation, the performance of DDFC using Pt-Ru catalyst at 80°C is improved. By supplying sufficient steam before operation, the performance of DDFC using Pt-Ru catalyst at 80°C is also found to improve. Before and during operation, more steam is needed for stable operation of the DDFC using Pt-Ru catalyst at 80°C than using Pt catalyst.

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This paper deals with partial discharge (PD) time-sequential properties of SF₆/N₂/CO₂ ternary gas mixture as well as SF₆ and SF₆/N₂ gas mixture under ac and positive dc voltage applications. The measurements were carried out by changing the gas pressure up to 0.6MPa and applied voltage with the N-shape characteristics of breakdown voltage vs gas pressure for each tested gas considered. We obtained experimental results of gas pressure dependence of maximum peak value of PD current pulse as well as relationship between the time interval of PD pulses and the peak value of PD pulse. We discuss the mechanism of increase in breakdown voltage by adding CO₂ into SF₆/N₂ gas mixtures in terms of change of PD type from streamer to leader discharge.

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A new electromagnetically actuated vacuum circuit breaker (VCB) has been designed and developed on the basis of the transient electromagnetic analysis coupled with motion. The VCB has three advanced bi-stable electromagnetic actuators, which control each phase independently. The VCB serves as a synchronous circuit breaker as well as a standard circuit breaker. In this work, the flux delay due to the eddy current is analytically formulated using the delay time constant of the actuator coil current, thereby leading to accurate driving behavior. With this analytical method, the electromagnetic mechanism for a 24kV rated VCB has been optimized; and as a result, the driving energy is reduced to one fifth of that of a conventional VCB employing spring mechanism, and the number of parts is significantly decreased. Therefore, the developed VCB becomes compact, highly reliable and highly durable.

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This paper proposes effective and general-purpose insulation design method of the power cable joint. To improve the insulation performance of the cable joint, the electric field strength on the inner electrode surface should be made as low as possible. The evolution strategy (ES) method is employed for obtaining the optimum shape of the electrode. The multi-objective evaluation is performed as well as the single-objective evaluation. The one of the objective functions is the maximum electric field strength on the electrode and the other is the maximum electric field strength along the interface. The electrode shape that shows the smallest maximum electric field is obtained among the shapes that satisfy the constraint condition.

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