As reliable and stable operations have become critical issues in deregulated electric power markets and systems, a growing number of individuals need advanced and timely information that will allow them to understand the major trends and technologies that are moving this dynamic segment of the electric power industry and market ahead. Under such circumstances, Power System Engineering Committee in The Institute of Electrical Engineering of Japan (Chairman: Ryuichi Yokoyama) and The Consortium for Power Technology of Japan (President: Takeshi Taneichi, Secretariat: Waseda University) have organized a special symposium on “New Issues on Electric Power Markets and System Operations in Asian Countries" on May 28th, 2007, at Uchisaiwaicho Hall in Tokyo. The purposes of the symposium were to address and discuss current situations and new issues related to reliable and stable operations of power markets and systems in the competitive environment in Asian countries. This article is a summary of presentations by four prominent speakers in the special symposium.

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After the last war, the output of single Steam Turbine Generator produced by the own technology in Japan returned to a prewar level. Electric power companies imported the large-capacity high efficiency Steam Turbine Generator from the foreign manufacturers in order to support the sudden increase of electric power demand. On the other hand, they decided to produce those in our own country to improve industrial technology. The domestic production of large-capacity 125MW Steam Turbine Generator overcome much difficulty and did much contribution for the later domestic technical progress.

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In this study, an adaptive PSS using data measured at its generator bus is developed. The low-order linear models are utilized for the eigenvalues analysis of the large-scale power system and for the PSS on-line tuning. A generator with the PSS is modeled as the 5th order model, and the models are identified by the least squares method using measured variables at each generator. Control parameters of the phase compensator in the PSS are updated online by using the trinomial tree method based on the eigenvalue analysis. The 4th order model is also developed to obtain the dominant oscillation mode of the whole system. The PSS parameters are updated only when the dominant eigenvalues detected at the 4th and 5th order models are converged for a given period, and the identification is considered to be accurate enough to update the parameters. Dynamic digital simulation is carried out for IEEJ WEST 10-machine system model to show the effectiveness of the proposed tuning method.

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A method for effective utilization of power distribution apparatus in an industrial park by looping distribution lines is proposed. The proposed method uses a series type Back-To-Back (BTB) converter in loop distribution line. This method solves the problem of heavily-loaded and lightly-loaded lines condition in distribution line autonomously. The problem of heavily-loaded and lightly- loaded lines results in lower utilization of transformers and increases losses in electricity system of the industrial park. By employing this proposed method, effective utilization of apparatus is realized by minimizing circulating current and balancing power of transformers in loop distribution line. One of the major characteristics of the proposed scheme is that the required converter capacity is small and it can be installed close to the transformers in loop distribution line. Analysis and simulation results to validate the proposed method are presented in this paper.

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Global warming caused by carbon dioxide (CO₂₎ and other greenhouse gases is one of the serious environmental issues. Carbon dioxide is the biggest contributor to global warming. Many efforts to reduce emissions of CO₂ are carrying out in various fields. In electrical power system field, various approaches to reduce CO₂ emissions have been performed such as loss reduction, utilization of renewable energy, recycling of resources and so on. Especially, distribution loss minimization is effective to reduce CO₂ emissions because reduction of distribution loss leads to save the energy. For example, the largest distribution system in Japan consists of about 19,000 feeders. Much CO₂ emissions can be reduced by minimizing distribution loss of the largest distribution system. However, CO₂ emissions reduced by distribution loss minimization for the largest Japanese distribution system have not been estimated so far.
In this paper, the authors try to calculate annual CO₂ emissions reduced by distribution loss minimization for a distribution system model based on partial actual data, which is composed by 19,000 distribution feeders, 95,358 sectionalizing switches and 73,849 load sections. In the trial calculation, reduced CO₂ emissions are estimated by sequentially proceeding four procedures: (1) classification of distribution system model into several load areas, (2) determination of loss minimum configuration in each load area, (3) calculation of reduced annual distribution loss for each area, and (4) calculation of reduced annual CO₂ emissions. As the result of the trial calculation, reduced annual CO₂ emissions of 40 × 10⁶kg/year is estimated for the Japanese largest scaled 19,000 feeders distribution model.

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Recently, the total number of Wind Turbine Generation System (WTGS) connected to distribution network has been increased drastically. Installation of WTGS can reduce the distribution loss and emission of CO₂. However, the distribution network with WTGS must be operated keeping reliability of power supply and power quality. The WTGS's effects to distribution network depend on its structure. In order to accomplish both the stable operation of distribution network and the progress of WTGS's prevalence, it is necessary to evaluate the acceptable output of WTGS quantitatively. In this paper, the authors evaluate several WTGSs connected to distribution network from viewpoint of Acceptable Maximum Output (AMO). The operational constrains to calculate the AMO of a WTGS are the following, (1) voltage limit, (2) line current capacity, (3) no reverse flow to distribution transformer, (4) short circuit capacity, and (5) voltage dip by inrush current. In order to evaluate the WTGS from viewpoint of AMO, numerical simulations are accomplished for a distribution system model. Furthermore, characteristics of AMO of a WTGS connected to distribution feeder are analyzed by several numerical examples.

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In the switching impulse test of the transformers, magnetic saturation of core is produced when full test voltage is applied to the winding. The waveform then appearing is different from the waveform of the switching impulse test voltage which has been discussed in the standard waveform 250/2500 microseconds.
On the reactor testing, damped oscillation discharge is generated when voltage of an impulse generator is applied to the winding since the inductance of the reactor is far below the exciting impedance of the transformer. In some cases, therefore, it is not possible to obtain the specified waveform in a large shunt reactor.
This paper shows for determining a method the waveform of the switching impulse voltage and recommends the obtainable values of waveform parameters on reactors that wider tolerances may have to be accepted.

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One of the common problems faced by many electric utilities concernes with the uncertainty from both load forecast error and generating unit unavailability. This uncertainty might lead to uneconomic operation if it is not managed properly in the planning stage. Utilities may have many operational tools, e.g. unit commitment, economic dispatch. However, they require a proper operating strategy, taking into account uncertainties. This paper explicitly demonstrates how to include the uncertainties to obtain the best operating strategy for any power systems. The uncertainty of the load forecast is handled using decision analysis method, meanwhile the uncertainty of the generating unit is approached by inclusion of risk cost to the total cost. In addition, three spinning reserve strategies based on deterministic criteria are incorporated in the development of scenario. Meanwhile, Mixed Integer Linear Programming method is utilized to generate unit commitment decision in each created scenario. The best strategy which gives the minimum total cost is selected among the developed scenarios. The proposed method has been tested using a modified of IEEE 24-bus system. Sensitivity analysis with respect to the number of unit, expected unserved energy price, standard deviation of load forecast, and probability of load level is reported.

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Damage of home appliances, such as personal computers and fax machines has a great influence on highly sophisticated information society. Surge protective devices (SPD) are expected to be prevalent because installation of the SPD at a switchboard is recommended in the regulation on indoor wires revised in 2005.
In this study, experiments were conducted with a full-scale distribution system and interior wiring in order to clarify lightning response to surges intruding from service wires. The results confirmed that SPD at a switchboard with common grounding wire is effective for protecting home appliances. But in some cases, surge current could propagate into communication lines when the ground wires of SPDs at a switchboard and of a communication appliance are connected each other.

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The low pressure mercury lamp has been used as the sterilization technique by UV light. However, short time high efficiency sterilization have been required in recent years. Although the plasma arc is one of the highly intense radiation medium, there is few papers of sterilization by a plasma arc. The number density and net emission coefficient of high temperature argon mixed with iron or mercury vapors are calculated by using a line spectrum emission, free-bound emission, and free-free emission equations. The high net emission coefficient of UV ray emitted from argon-iron gas is obtained. Fe II from argon-iron gas is dominant in UV ray wavelength range. The tendency of the spectrum characteristic of sterilization about the wavelength of argon-iron gas obtained. Especially, a strong emission was obtained at 259nm for argon-iron gas. The net emission coefficient of argon-iron gas is larger than that of argon-mercury gas from 200 to 300nm. Mercury vapor has few spectrum lines and the net emission coefficient becomes small. Therefore, the argon-iron gas is applicable to UV ray sterilization.

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Accuracy of the calculation method of transient DC component of three phase short circuit current is carefully studied. Using a multi-machine model system 4 different methods are compared, which are catenacci method, AIEE method, 4 parameters method, and the proposed method. Among all these four methods the proposed method gives the most accurate result, which gives almost identical wave form of the averaged wave obtained by the post processing of ATP-EMTP results. Compared to ATP-EMTP the proposed method is more convenient because it automatically gives the severest fault case while ATP-EMTP needs several computations.
Main reason of the discrepancies of the conventional methods is based on the insufficient order of the internal models. In contrast to the proposed method, they use only a second order model at most. The usefulness of the proposed method is demonstrated using a test analysis of the saturation of a current transformer. Computing time is also discussed by comparing the results applied to two 10-machines systems and one 30-machines system.
In conclusion, the proposed method is accurate and is ready to apply to multi-machine systems within a realistic computing time. The usefulness of the proposed method is confirmed by this study.

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The purpose of this study is to propose a method to evaluate approximately a geographical smoothing effect on the output fluctuation of photovoltaic generation systems installed densely in a bounded area. This paper comprises two parts. The first part shows the result of analysis about output fluctuation, which is observed during four months in summer at ten groups of photovoltaic generation systems, located in AIST Tsukuba Central and totaling 844kW, and presents findings about a geographical smoothing effect on output fluctuation in the light of statistical characteristics such as the standard deviation of output variation and correlation factors between the output variations of different systems. The second part contains a mathematical modeling of a geographical smoothing effect in a bounded area based on the findings presented in the previous part and proposes a set of formulas to evaluate approximately a geographical smoothing effect on the output fluctuation of photovoltaic generation systems installed densely in a bounded area only using geometrical information about the area.

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Two-dimensional analysis is carried out in order to reveal the generator characteristics of the large pulsed MHD generator “Sakhalin" under the self-excited magnetic mode and the fixed magnetic mode. Numerical results show that there is a considerable difference of the generator characteristics between the two magnetic modes. Under the fixed-magnetic mode, the channel current decreases with the loading parameter, while the channel voltage increases, so that the channel output power has an optimal value of loading parameter. Under the self-excited magnetic mode, the channel output power increases with the loading parameter in the low part of loading parameter because the channel current and the channel voltage increase with the loading parameter. In the high part of loading parameter, the channel output power is, however, saturated with the increase of the loading parameter because the channel voltage increases with the loading parameter, whereas the channel current decreases.

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This paper presents analytical calculation of magnetic flux line from hexahedral edge finite element analysis and its allocation using the Bubble System for visualization. Most of methods to draw magnetic flux lines can't take their distribution into sufficient consideration. As a result, such visualizations bring out observer's misunderstanding about the magnetic field and the phenomenon. Therefore, the method to appropriately allocate the magnetic flux lines in a space using the Bubble System is proposed. In the proposed method, the bubble's radius of the Bubble System depends on the magnetic flux density to consider the density of lines. The proposed method using the Bubble System can visualize magnetic flux lines appropriately. Then, the observer can correctly grasp the magnetic field and the phenomenon.

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This paper describes the theoretical analysis of lightning impulse voltage waveform with an overshoot or oscillation caused by the residual inductance of the impulse generator. The oscillating lightning impulse waveform is expressed by the following formula;
v_out (t) = A {e^-α1t - e^-α2t sin(ωt+θ)/sinθ}
where A, α₁, α₂, ω, θ are constants, respectively. The front time, time to half value, peak value, oscillation frequency, overshoot voltage k-factor and virtual origin are derived from this expression. Some simulation results show the following merits;
(1) The discussion on the definition of front time and tail time is possible by comparing with the base curve and overshoot.
(2) The formula can analyze the effect of the residual inductance of the test circuit and express the overshot (i.e. k-factor and overshoot).
(3) The formula can express the relationship between the oscillation frequency and the decay time.
(4) The discussion on the meaning of base curve and waveform parameters is possible based on the theoretical analysis.

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This paper reports an insolation forecasting method for photovoltaic power predictions. The method of proposal forecasts the global irradiance every one hour by using weather forecast every three hours. The weather forecast is classified into 14 kinds of weather change categories by weather change patterns, and the insolation forecasting accuracy is improved. The forecasting accuracy was examined based on the measurement data and the weather forecast announced in Tokyo. In the result, using weather change patterns decrease mean absolute error ratio of hourly forecasting from 32.6 to 30.2% and the error ratio of daily forecasting from 24.7 to 23.5%. The result also shows the possibility that the error ratio of hourly forecasting is decreased to 24.5% and the error ratio of daily forecasting is decreased to 17.8% in Tokyo when the weather forecast accuracy is improved.

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