Recently, the World Wide Web is the most potential force for information distribution. For educational purpose, hundreds of technical courses are offered on the Web by many universities or educational institutions. For power system engineering, we can also access the large amount of information by Web. The Internet technologies have many educational advantages over their conventional classroom teaching counterparts.
In this paper, we proposes a remote power system analysis using the internet environment. Java's unique characteristics such as Java Native Interface (JNI), serialization, and multithreaded programming are helping to implement our system. The usefulness are demonstrated by using a remote power flow analysis for user created model power systems.

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A real time FFT based on-line identification has been presented for the real time monitoring of power system oscillation modes. The monitoring system is set up by using a personal computer with a DSP board with AD conversion interfaces. For the monitoring, the real power flow signal is utilized. The real power signal is sampled through AD conversion interfaces and stored in the memory. The monitored signal is also passed to the workspace in the Matlab/Simulink environment for the FFT analysis and also the visualization of the obtained results by using a color mapping to show the variation of oscillations in real time. Furthermore, a fuzzy reasoning based filtering has been proposed to washout individual oscillation modes included in the measured real power signals. The efficiency of the proposed method has been demonstrated through the testing using a test signal, monitoring signals on the analog power system simulator at the Research Laboratory of the Kyushu Electric Power Co. In addition, the proposed system has been tested by using real power flow signals measured on actual 500 kV trunk lines.

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Prony analysis method can detect oscillation frequency, damping, phase and amplitude directly from time series data. Several applications based on the method have been developed in power systems, but it is said that it gives less accurate results for noisy data. In this paper, a power swing mode detection method is presented which is suitable for noisy measured data in power systems.
First, the analysis parameters such as sampling interval, number of data and number of orders are investigated. For detection of low frequency inter-area modes, longer sampling interval (0.2 to 0.4 s) is preferable. The importance of each detected mode can be evaluated by an index based on integration of each waveform. And for data containing large noise, the accuracy of analysis can be improved by applying a low-pass filter. By modifying amplitudes and phases based on the filter characteristics, the original waveform eliminating noise can be estimated precisely.
Effectiveness of the method were verified through examinations using active power and bus voltage data actually measured in a power system.

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A reactive power resource planning problem is generally formulated as a large-scale mixed integer programming problem, and is mathematically hard to solve. In this paper, an approach named ‘multi-stage tabu search’ is proposed to solve the problem, where tabu-search is used in two stages. One is used to determine the optimal installation of reactive power resources. The other is used to determine the optimal operation of the reactive power resources for several pre-determined operational states. To reduce the computational burden, the sensitivity analysis is also introduced for selecting the efficient neighborhood solutions of the tabu search. Numerical examples are shown to demonstrate the validity of the method.

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Advanced real-time power system simulator has been developing which consists of conventional real-time analogue simulator (RAS) and real-time digital simulatot (RDS). The Bergeron method used to present distribution lines was utilized to combine the RAS with the RDS. EMTP simulations were carried out to verify the advanced power system simulator concept and to evaluate on the effect of various parameters. A prototype of the advanced power system simulator with the Bergeron method was tested Test results confirmed the feasibility of the real-time power system simulator.

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Power system has become so large and, furthermore, forthcoming open electricity market will make power system operation more complex. Therefore, power system operation is required to become more efficient and flexible. Very fast power system simulation method is a ticket to more sophisticated power system on-line monitoring and control, and parallel computing technology is a key technology to very fast power system simulation method. In this paper, an efficient and fast parallel algorithm of network calculation is proposed, which will contribute to the development of fast power system simulation program. Numerical examples show that the proposed method using 6 processors is about 4.0 times faster than usual serial algorithm when applied to a large scale radial power system and about 3.2 times faster when applied to a large scale loop power system.

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A real-time power system simulator becomes an indispensable tool in the power system engineering for testing newly developed devices and controllers. The conventional digital simulator has the following disadvantages,
_??_The real-time simulator requires a special hardware for parallel processing. This makes the simulator very expensive.
_??_Many real-time simulators are based on the similar algorithm to EMTP (Electro-Magnetic Transients Program). The algorithm is not easy to implement on the parallel processors.
_??_The implementation and modification of the newly developed devices and controllers are not so easy for the end users.
These are the reasons why the conventional real-time digital simulators for power systems are not utilized widely in the universities and power industries.
The present paper proposes a new scheme of low cost and flexible power system real-time simulator. The proposed real-time simulator has the following features,
_??_The simulation model is constructed by the blockdiagram representation. The model is converted to executable code automatically by widely used CAD software.
_??_In order to speed up the computation and make it easy to model the power apparatus by the blockdiagram representation, Euler's method is utilized as well as some approximations. In addition, insertion of the interface delay is proposed for improving the efficiency of the parallel processing. This allows a low cost and flexible configuration of the power system simulator.
The present paper describes results of the feasibility study on the proposed low cost real-time simulator. It makes it clear through the eigenvalue analysis that the real-time simulation can be conducted with enough accuracy by the proposed scheme. In addition, the validity of the proposed real-time simulator is demonstrated through the comparison with EMTP. The obtained results indicate that the proposed scheme enables the development of a low cost and flexible real-time simulator.

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In recent year, enhancement of consciousness for problem of environment is advancing effective use of natural energy, such as wind power generation system. Induction generators are almost employed in the generation system due to saving of cost and maintenance. When the generator is interconnecting to a distribution line, high inrush current is fed from the line to the generator. Since the current causes momentary sag on the line, a countermeasure must be taken.
The paper describes a study of interconnecting technique of induction generator to a distribution line. Authors had studied phenomenon of momentary sag on a distribution line due to high inrush current of a induction generator and a countermeasure against the voltage sag.

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The grid-connected PV systems in the community area is the system which connect the area distribution line to commercial high voltage distribution line at one point. The area distribution line connect many residential PV systems, public facilities PV systems, different residential loads and public facilities loads. The characteristics of the grid-connected PV systems and the grid-connected PV systems in the community area are studied and simulated by computer. The system construction method of the grid-connected PV systems in the community area is obtained when the residential PV systems are diffused step by step.
This study shows that the interchange electric power of the grid-connected systems in the community area can be directly supplied to the demand loads in the community area. The maximum annual interchange power of the grid-connected PV systems in the community area can be obtained by using suitable PV capacity based on the rate of diffusion for residential PV systems. The electrical energy cost of the grid-connected PV systems in the community area is lower than the grid-connected PV systems as the increase of annual interchange electric power of the grid-connected PV systems in the community area if selling price of surplus power is lower than purchased price of shortage power.

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The importance of the dynamic stability analysis has been increased in the complicated power systems. Since power system operators have to confirm the status whether it is stable or not for various contingencies, faster and more accurate dynamic analysis becomes indispensable. This paper proposes an application of the explicit embedded Runge-Kuttamethod (ERK) with error assessment to the power system transient stability studies.
Historically, the Tokyo Electric Power Co. (TEPCO) has been used “classical” 4 th order Runge-Kutta method (RK 4) with fixed integration step size since 1960 s. Extensive efforts have been devoted to improve the program, together with TEPCO and Mitsubishi Electric Co. (MELCO). Most of apparatus/controllers used in practical and future systems have been implemented. But we do not have variable step-size simulation nor any assessment for accuracy of dynamic studies, so far.
Concerning to accuracy issue, we applied one of ERK (Dormant & Prince 4^1H and 5^1H order Pair). The proposed method will be implemented to the practical program which has been used in TEPCO. Tests are carried out with models based on existing system.

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With the advancement of power electronics technologies, it has become feasible to control the line power flow directly and quickly. In the circumstances, the direct power control of generator in order to linearize the power swing property has been developed. The controller is robust in the sense that the control parameters do not have to be adjusted even if the operating point of the power system is changed. The effectiveness has been confirmed by a series of simulation studies. In this paper, the feasibility of control strategy is confirmed by several experimental results using a 10 kVA model power transmission system. First, the control scheme to adjust the generator power to the specified signal is implemented in the experimental system, which is extended to the control strategy for the power swing linearization. The capability of generator power direct control by Unified Power Flow Controller (UPFC) is confirmed by the experiments in which the generator power is controlled to follow the specified sinusoidal waveform. Some experimental results demonstrate the significant effect on the power system stabilization and the robustness of the proposed controller of power swing.

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The 500 kW wind generator was developed as one of NEDO's projects, and it has been operated at TAPPl wind park since October in 1996. Since then, several tests on its performance have been made so far. One of the most important characteristics is to know the dynamic behavior under fluctuating wind conditions. For this purpose, we performed the modeling of the NEDO 500 kW wind generator by system identification technique using the measured data. Then, we clarified the basic characteristics such as transient response and frequency response of the generator based on the model. We confirmed that the simulated results of dynamic behavior almost agree with the measured results.

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Electricity markets are experiencing widespread changes that are significantly altering the industry. In this paper, we study economic load dispatching rules in power systems under competitive environment when independent power producers (IPP) are introduced, and analyze their economic consequences by using game theory. An electric utility and several IPPs are viewed as players of a game in the model. We consider an extensive game model of electricity market where IPPs enter into the game, firstly as a group and secondly as individuals. Both the Utility and IPPs intend to maximize their own profit. The prices between the electric utility and IPPs are determined in such a way that they are equilibrium points of a noncooperative game. In this paper, we employ the Stackelberg strategy and Nash equilibrium solution method to analyze negotiation processes between utility and IPP since it is widely recognized as a rational decision for competitive markets in terms of axiom. It is shown in this paper that all obtained simulation results can be viewed as an extension of the equal incremental cost from regulated power systems to competitive power markets.

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The symmetrical method is one of the common theory to simulate the faulted state of electric power system even now. However, this symmetrical method has major disadvantage especially for unbalanced fault calculation on multi-parallel routes due to the necessity of complex equivalent zero-sequence network formation. In order to secure the power system including multi-parallel route in it from the disturbance, the method is needed which can solve the faulted state with accuracy and efficiency when the disturbance occurs on that multi-parallel route.
From the point of view described above, this report proposes a newly developed fault calculation method, which can easily incorporate zero-sequence mutually coupling effect among multi-parallel route in it without any topological changes of the symmetrical network. In the proposed method, mutually coupling effect is treated as voltage source inserted each parallel branches to compensate the mutually coupling effects from other circuits. As the voltage source can be equivalently expressed as injection currents of connected nodes, the faulted state can be easily calculated without topological change of the zero-sequence network. The numerical application result for a couple

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Grounding resistance of tower footing base is one of the most important factors for lightning surge analysis in electric power system. Some investigations have showed that the grounding resistance under very large current impulse has nonlinear characteristic because of soil ionization effect. In this paper, we describe the multi-phase flashover analyses for 500 kV transmission line especially on the high resistivity soil. We propose here a nonlinear grounding resistance model to apply to flashover EMTP simulation. As the result of the simulation, it became clear that the probability of flashover using the proposed model is evidently less than that using the conventional model. It suggests that the appropriate model describing grounding resistance in detail should help to make a reasonable design to construct transmission towers.

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The unnecessary triggering of an earth leakage circuit breaker (ELB), which may occur when a lightning strike occurs (hereafter referred to as a false operation) causes an interruption of the stable supply of electricity because it leads to a power failure accident for low voltage consumers. Furthermore, in many cases, the major cause of the false operation is not the direct lightning strike, it is the rather small induced lightning surge invading through a distribution line. As a result, the problem occurs over a wide range and, therefore, it becomes one of those problems that must be solved in order to properly serve the present highly information-oriented society.
The author has studied the causes and mechanisms of the false operation of ELBs due to lightning surges which may occur when lightning occurs.
In this report, the author details the results of further experimental studies into the means to prevent false operation of ELBs due to lightning surges building on the study results obtained so far, and reports the results obtained.
(1) Reverse-parallel diodes were applied to the secondary side of the zero phase current transformer (ZCT) of an ELB. As a result, the surge current at which false operation occurs was improved by approx. 6 times, that is, from 80 to 500 A.
(2) A false operation prevention device for an existing ELB was trial-manufactured and studied experimentally. As a result, the false operation performance could be improved up to a surge current of 1.4 kA.

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At the sub-station connected with transmission lines and cables, shunt reactors are sometimes installed to compensate the capacitive current of the transmission lines and cables. It is known that the re-ignitions occur and high-frequency currents flow during interrupting the shunt reactor currents by switches. When the high-frequency currents are interrupted immediately after the re-ignitions, called as high-frequency arc extinction, it often leads to appearance of repetitive re-ignitions or voltage escalations resulting in generation of dangerous over-voltages.
The authors investigated the occurrence of the high-frequency arc extinctions for a 550 kV one-break SF6 gas circuit breaker during interrupting a 550kV shunt reactor current. By computations for a actual 500 kV substation, minimum frequency of 290 kHz was obtained for the high frequency current. However, it was found by conducting 550 kV reactor current interruption tests that the high-frequency arc extinctions did not occur even if the high-frequency was lowered to 26 kHz. The high-frequency arc extinction is generally likely to occur at the lower frequency. So that it was concluded that the high-frequency arc extinction would not occur on the 550 kV one-break SF6 gas circuit breaker during interrupting the shunt reactor current in the actual substations.

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More renewable energy is desirable to be used to protect global warming and exhaustion of fossil fuel. One of such alternative energy system is hydrogen energy system. One of the methods to produce hydrogen from water by renewable energy is polymer electrolyte electrolysis cell (PEEC), which is high efficient and compact with high current density. To optimize operating conditions of PEEC, experimental characteristics measured in a small sized PEEC are compared with numerical analysis. Our numerical model considers two-dimensional variation of temperature and current density along the flow direction of supplied water and perpendicular to membrane/electrodes assembly, taking account of balance equations of mass, heat and electric charge. Calculated results show that the current density and temperature distributions along water flow direction are almost uniform. To confirm the uniform current density, a segmented electrode cell was made to measure the current density. Measured current density with sufficient water supply agrees well with the numerical when cell temperature is 40-80°C, average current density is 0.5_??_2A/cm² and water electrolyzing ratio is 2_??_5%.

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As Photovoltaic (PV) outputs depend on the solar radiation, to get constant power from PV, it has to be combined with any storage device. To realize this purpose, we developed a PV system combined with a storage system of ECS, named PV-ECS. The ECS is a new energy storage system which can directly charge and discharge the electric energy, and it consists of the Electric Double Layer Capacitor (EDLC) and Electronic Circuits which make the capacitor more attractive than the conventional device of chemical battery in terms of efficiency, cycle expectancy, etc.. This paper reports the outline and features of the newly developed PV-ECS system and its experimental results. In addition to the high energy efficiency, the long cycle expectancy of PV-ECS system makes us to expect that it will be put into practice in the near future.

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This paper develops a shunt admittance formula of an overhead conductor above snow by adopting Herz vector. Based on the formula, the effect of snow on the wave propagation characteristics of the conductor is investigated. The admittance is increased by the snow. The difference from the case of no snow becomes smaller as frequency becomes higher, because the permittivity of the snow reaches unity as the frequency increases. The effect of the snow on an attenuation constant increases and that on a propagation velocity and a characteristic impedance decreases, as the frequency increases. The difference from the no snow case in the attenuation constant, the velocity and the step response of wave deformation increases as the snow death, the density and the temperature increase. The characteristic impedance depends on the snow depth but not on the density and the temperature.

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The present study treats a large-scale high-performance supersonic closed-cycle disk MHD generator using cesium-seeded helium plasma with 100 MW thermal input, and investigates the effect of the diffuser back pressure on generator performance through detailed two-dimensional time-dependent numerical analyses for the region which includes the generation channel and the diffuser. In the simulation code, the gas dynamical quantity distributions are calculated by the TVD scheme proposed by Chakravarthy and Osher. It is made clear that high performance operation as designed and high isentropic efficiency including the diffuser region can be achieved by choosing the diffuser back pressure appropriately. The generator performance is influenced by the back pressure and its highest possible performance can not be achieved in both the cases the back pressure is lower and higher than its appropriate value.

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One of the possible fault location methods, is to sense the temperature rise following a ground fault, using a fiber optic distributed temperature sensor. Application of this method to the cable was verified, through sensing the temperature rise at a ground-fault test, using a power/optical composite cable. Next, application of this method to the joint was studied through sensing the temperature rise at a ground-fault test, using a thermocouple as a temperature sensor with test joints. An optical composite joint was experimentally prepared for a ground-fault test. The temperature rise at an incidence of a fault was determined and anticipated performance was demonstrated in a ground-fault test. Furthermore, the practical location system for multiple line was developed. This paper describes the application of this method to joints and the practical location system for multiple actual line.

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It is important for power system operators to determine the optimum network configuration. This paper proposes a new theoretical method to derermine the optimum radial network configuration of a power system.
This algorithm consists of processes as follows, (1) a power system equation can be represented by using node-flow matrix based on Kirch Hoffs 1^st law, (2) after diagonalizing the matrix, branches related to non-basic variables of simplex matrix are regarded as open ones, while branches related to basic variables are regarded as close ones of a radial network, (3) branch on-off operation corresponds to the pivot operation of LP method, (4) the objective function is renewed on every pivot operation.
By using this method on a distribution power system with 539 branches, it is found that calculated results are practically useful. And the calculation time (11 seconds) is also practically satisfied by taking measures as follows, (1) pivot selection only from remote controllable branches, (2) per unit description and sign reverse operation of branch flow. Moreover, even if the calculated value is the minimum solution by the effects of blanch capacity constraints, quasi optimum solution is obtained by using double pivot operation. This logic can be applied to not only a distribution network but also a transmission network at any system state such as normal situation, outage, maintenance, and restoration.

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