Due to deregulation in power sector, several planning and analytical models are being developed based on previous models, which used to be applied power system before deregulation. However, basic structures of the most of model are not changed so drastically. For example, understanding market structure such as old system in California or PJM, it is the best way of understanding several power production models. These market systems are well designed based on dispersed method for determining dispatch of power stations. Also, these modeling are now including Risk Management methods to evaluate position in trading and strategies of those companies.

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This paper presents some extensions for Combined Iterative Method (CIM) based on Modified Predictor-Corrector Iteration (MPCI) and Newton Raphson Iteration (NRI) to extend Electromagnetic Transient Simulation for including nonlinear elements in an electrical network solution. It is important to adopt an iterative method optimally in CIM to improve convergency, because a solution obit depends on a multi-dimensional plane between initial and real solutions. An effective construction of MPCI and Jacobian matrices based on a multi-dimensional solution with Dommel's method, and an effective expression of MPCI and NRI on EMTP-Type simulators have been also proposed to realize a high accuracy, high stability and saving a calculation time simultaneously for any kinds of circuits, Some examples are demonstrated using the proposed algorithm, and the results are compared with those by a basic nodal conductance approach (NCA), EMTDC/PSCAD solutions and measured results. The comparison proves the validity of the proposed methods, which is applicable to EMTP-Type simulators to solve a nonlinear circuit.

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Power system is a dynamic system, which includes several kinds of nonlinear elements. Transient stability is a typical example originated in the nonlinearity of power swing. On the other hand, the use of nonlinear analysis method based on the Hopf bifurcation theory tells us the existence of limit cycle around an operating point and the stability of limit cycle. In this paper power system global stability formed by an unstable limit cycle, is evaluated. The limit cycle mainly results from the excitation control. Therefore, it is important to consider the effect of flux change in the field winding in addition to the δ-ω variables. This paper presents a method to calculate the correct stability boundary associated with the unstable limit cycle. Some numerical results using a model power system demonstrate the accuracy of method.

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The phase domain generator model for instantaneous value simulation was proposed and introduced into ATP-EMTP as type-58 model by authors. Numerical stability of the type-58 model is higher than type-59 generator model in conventional dq0-domain. However, previous type-58 model had a few problems.
(1) Magnetic saturation was not formulated.
(2) Initialization of generators was inconsistent with unbalanced three-phase network. (3) Computation time was longer than that of type-59 model.
In this paper, modified type-58 generator model is proposed to solve and improve the above problems.

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In recent years, there has been a possibility to become lower reliability in power supply system due to the competitive environment. Also, from demand side viewpoint, customer's preference of service reliability has been widely diverse. Reliability differentiated power supply system is one of the most effective solutions to cope with the above problems. This paper presents an integrated resource planning (IRP) model for evaluating the benefit of reliability differentiated power supply service from the social point of view. The proposed model consists of demand side and supply side sub-models. In the former sub-model, all customers are divided into some groups that are differentiated in supply reliability of electric power. The latter sub-model determines a best mix of generating units based on minimizing the social cost. The numerical examples illustrate the influences of the reliability differentiated power supply service on the generation mix and social cost.

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This paper presents distribution system equipment models for the fast distribution three phase unbalanced load flow calculation. Recently, number of distributed generators introduced into distribution systems has been increasing and detailed system analysis using load flow calculation has been eagerly awaited. Moreover, since many distribution systems loads are composed of single phase loads, three phase unbalanced load flow calculation is required for the distribution system analysis. Although the fast distribution three phase unbalanced load flow calculation has been developed, various equipment models considering interconnection of distributed generators have not been developed yet in Japan. This paper develops practical equipment models such as various distributed generators, voltage control equipment, and loads for fast three phase unbalanced load flow calculation in distribution systems. The feasibility of the developed models is verified and demonstrated on practical distribution system models with promising results.

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The retail competition in electric power market has been introduced in Japan from March 2000. Although the liberalization is limited in a part of the retail power market having about 30% share of total electricity demand, the liberalized customers segment is now under competitive circumstances among the utilities and new entrants. This paper examines the profitability of competitive pricing for eligible segmented customers through scenario-based model analysis focusing on demand characteristics of segmented customers. The model includes the utility's investment in power generation for segmented customers to consider the long-term profitability rather than the short-term one. Load leveling is not always achieved under profit-maximizing behavior of the utility because the profitability of competitive pricing depends on load patterns of bypassed customers and price differentials among power suppliers.

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Due to the relatively high deNOx efficiency and the compactness, the pulsed-discharge deNOx process is considered to be one of the candidates for deNOx processes of combustion gas. However, a sufficient guidance for the optimum operation condition has not been presented. In this study, we have simulated the pulsed-discharge deNOx process by solving the Boltzmann equation for discharge electron and the deNOx chemical reaction equations simultaneously, and have clarified the effect of exhaust gas composition, temperature and pressure on the deNOx performance. When the oxygen concentration of exhaust gas increases, only the conversion from NO to NO₂ proceeds keeping the removal efficiency, the energy consumption and the reduction ratio almost constant. When water vapor concentration increases, reactions NO→HNO₂ and NO₂→HNO₃ proceed due to the increased OH concentration resulting that the reduction ratio decreases, and both the removal efficiency and the energy consumption are improved drastically. When the gas temperature increase, the generation of NO increases by the N radical reaction with CO₂ and O₂ resulting that both the removal efficiency and the energy consumption deteriorate. When the gas pressure increases, the removal efficiency and the energy consumption decreases by decreasing ratio of the produced electron and radicals density to combustion gas density.

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When lightning strikes an overhead distribution line, an overvoltage is induced across an insulator due to the lightning current flowing into the system. In analyzing the lightning overvoltage in a distribution system, the surge characteristic of a grounding vertical conductor should be taken into account if the lightning current has a steep front. In the present paper, an experiment on a reduced-scale model is carried out to evaluate the surge characteristic of a grounding lead conductor with circular and flat shapes. On the basis of the experimental result, an empirical formula of the surge impedance of the grounding vertical conductor is proposed. This formula includes the effect of a reinforced concrete pole close to the grounding vertical conductor. The developed formula agrees well with measured results. The formula of the surge impedance of the grounding lead conductor is effective for an accurate lightning surge analysis in an overhead distribution line.

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The behavior of magneto-acoustic waves in a non-equilibrium subsonic disk MHD generator was examined. The solution of the six-order dispersion relation obtained by linearlizing the set of MHD equations suggested that the magneto-acoustic wave which propagates at the velocity of u_r - a (u_r: radial fluid velocity, a: sound velocity), should be damped in the subsonic flow. From time dependent quasi-one-dimensional simulations, it was verified that the pressure disturbance in the subsonic generator was damped at approximately the same rate as the value predicted by the linear theory. From a simplified analytical model, the mechanism of magneto-acoustic instability under the fully ionized seed was discussed, and the damping criterion for the magneto-acoustic wave was clarified.

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The frequent (20000 times) switching ability of a puffer-type SF₆ gas switch as a switch to move usual opening points is verified by the presumption based on the data of a less number (up to 5000) of load switching tests. The variation of measured arc times is approximated by a saturating function of switching number and the cumulative arc time up to the No 20000 switching is estimated. CF₄ gas is generated as one of cracked gases of SF₆ in the presence of the material of a tested nozzle and increases cumulatively with increasing switching number without being absorbed in an absorbent. A linear relation is experimentally found between the cumulative arc time and the amount of CF₄ proportional to the consumed mass of the nozzle. The consumed mass and corresponding enlarged diameter of the nozzle at the No 20000 switcing are estimated. Several model worn nozzles of different enlarged diameters including the estimated one were prepared and the switching with any of the model nozzles was quite successful. The arc time measured with the model worn nozzle of the estimated diameter (No 20000) agrees roughly with the corresponding estimated arc time and both arc times are not longer than the arc time to initiate the failure of switching. It is concluded that the switch under test will maintain sufficient switching ability still at the No 20000 switching as well.

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An average wave front time of the large lightning current, such as over 50kA, is 4_??_5 μs in summer and about 16μs in winter, respectively. In case lightning hits a transmission line, the wave shapes of the tower top voltage are much different in winter from the summer ones, because of the large difference in the current wave front time. Little published data is available on the analysis of the tower top voltage caused by lightning with the longer wave front time, such as longer than 6μs. The authors calculated tower top voltage using EMTP, and found the important phenomena. (1)The wave shape of the tower top voltage is “a leniently rising impulse” in case of the winter lightning. The flashover voltage of an airgap for these kinds of impulse voltage is not proportional to the gap length. (2)The effect of the tower footing resistance to “restrain the occurrence of backflashover” is very much larger in winter as compared with summer. (3)The results of analysis give indispensable factors on the estimation of probability of flashovers caused by winter lightning.

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The fundamental performance characteristics of an electro-hydrodynamical (EHD) pump composed of a ring electrode and a cylindrical electrode have been discussed. The ring electrode and the cylindrical electrode, namely, the EHD pump is arranged inside an acrylic U type pipe that is filled with working fluid such as transformer oil. In this paper, we mention measurement of liquid displacement, relations between electric pressure and applied voltage, and polarity effect of applied voltage of the EHD pump that vertically transports dielectric liquid such as transformer oil. Liquid displacement caused by the non-uniform electric field is defined as its difference from the steady state liquid level. Test results indicate that liquid displacement is significantly dependent on applied voltage. The electric pressure reached 810(Pa) at applied voltage of 30(kV). When applied voltage exceeded a threshold value, the electric pressure was produced. The transformer oil always moved from the cylindrical electrode toward the ring electrode. Namely, polarity effect of applied voltage on direction of liquid displacement was not observed.

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Lightning occurs in the Joetsu area on between 30 and 35 days per year. The Japan Meteorological Agency's lightning warnings are valid for as many as 2, 170 hours per year. Moreover, electric power consumers have observed that approximately 65 incidences of grounding (zero-phase voltage of 4.5 kV or more), which are assumed to have been caused by lightning, occurred in the 66-kV systems belonging to utility power suppliers in the Joetsu area. Furthermore, there have been a number of cases of instantaneous power failure (two seconds duration or less) each year that are also assumed to be attributable to lightning. For large electric power consumers, such problems particularly instantaneous power failures which can cause serious damage to production facilities, cannot be overlooked. If predicting such types of lightning could be made relatively easily, electric power consumers would be able to establish production systems that enabled them to anticipate and deal with instantaneous power failure. Lightning prediction systems are therefore particularly important to users of utility power systems.
With the increasingly widespread use of the Internet, it has become possible to readily acquire and utilize cloud-to-ground lightning information that has been made publicly available by Tohoku Electric Power Co., Inc., and Hokuriku Electric Power Co., Inc. Therefore, the authors propose applying a prediction algorithm formulated by them to the assessment index through utilizing such Internet based lightning warnings from the Meteorological Agency and cloud-to-ground lightning information from Tohoku Electric Power Co., Inc., and Hokuriku Electric Power Co., Inc. The number of measured grounding incidences was used to determine the assessment index. During a two-year period from 1999 to 2000, lightning was predicted at the users' end of the Joetsu area's 66-kV utility power supply systems. Measurements indicated a 94.6% success rate in predicting lightning and a 100% success rate for predicting instantaneous and normal power failure, thereby proving the effectiveness of the proposed approach.

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According to the deregulation of the electric power market and the improvement of small generators, the electricity supply by the dispersed generators (DG) is very attractive for both utilities and consumers. However, because of various types of DGs with small rating, the introduction of DG in a power distribution system increases the complexity of system operation. We propose on-line information exchange between DGs to facilitate autonomous operation of the distribution system. This paper evaluates the improvement of reliability of such system by the on-line information exchange between DGs.
The large scale introduction of DGs might allow the power supply to the distribution system to be continued even if it is isolated from the upper system. We discuss the effect of information exchange on the system stability under islanding after the upper system failure. The analysis is performed in terms of instantaneous values calculated by using PSCAD/EMTDC. As a result, it is revealed that the transient stability improves when a DG with fast response speed and DG with slow speed exchange the information on inverse power flow to the network.

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One of key issues in designing superconducting apparatuses is how to design high current density superconducting windings whose quench current surely exceed designed operation current. However, a method to quantitatively estimate a quench current of the winding has not been developed. This paper is related to this issue. MQE (Minimum Quench Energy) is a well-known criterion of the stability of superconductors but cannot be a proper measure of the stability of the superconducting windings without knowledge on the size of disturbance in the windings. Therefore, it is important to know quantitatively the size of the disturbance energy to estimate the stability.
Generally, a major cause of unexpected quenches of high current density superconducting windings is a disturbance caused by an abrupt conductor motion due to electromagnetic forces. The released energy by the conductor motion depends on many factors, such as stiffness, compliance and irregularities in dimensions of the conductors, electrical and mechanical forces to the conductors, fixing structure of the conductors etc. We developed a method to estimate the disturbance energy due to conductor motion taking into account of these factors. Once the disturbance energy is known, the stability of the windings can be estimated by knowing MQE of the conductor. The conductor motions occur at poorly supported parts of conductor in winding which are caused by irregularities in the size of conductors and structures. By assuming that the irregularities follow Gaussian process, we developed a statistical method to predict quench characteristics of superconducting windings.
In this paper, the theory to estimate quench characteristics of superconducting windings is described. We applied the theory to two different types of superconducting windings, a large bore superconducting magnet and rotor windings of a superconducting generator, and compared the estimated results with excitation test results. The estimated quench characteristics well coincided with excitation results. Details of the analysis method are presented in the paper. We also discussed about possible method to increase stability or current density keeping required stability level.

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With the advent of interconnection of large-scale electric power systems, many new dynamics power system problems have emerged, which include low-frequency intersystem oscillations and many others. To date, most major generators in trunk electric power system in Japan are equipped with supplementary excitation control, commonly referred to as the conventional single and two input PSS. However, low-frequency oscillations still occur. It is difficult for these conventional PSS to improve the additional damping of power system oscillation, because of the hardware and design of fixed PSS control constants from a one-machine infinite-bus model. It has therefore become necessary to develop a new adaptive LQG system of generator. This paper explains the development of new adaptive LQG system and the simulation of low-frequency and local mode oscillation for this new adaptive LQG system.

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In previous paper, we proposed a 3-phase variable inductor, which has a sinusoidal output current and a good controllability. We developed a trial 100-kVA var compensator for 6.6-kV ac distribution system using the 3-phase variable inductor. The variable inductor is composed of three orthogonal-cores that have wedge gaps for a reduction of harmonics in the output current. We reported that the trial var compensator is useful for voltage stabilization in the distribution system.
In case of application for a lager power system, the orthogonal-core is not so suitable for enlargement because of its peculiar structure. In this paper, we proposed a new variable inductor that is suitable for enlargement more than the orthogonal-core. We calculated the fundamental characteristics of the new variable inductor using the 3-D nonlinear magnetic circuit analysis.

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This paper proposes new pulse width control to suppress the higher harmonics of the output of a multilevel converter applied for back-to-back (BTB) HVdc Link. A multilevel converter can reduce the snubber loss and the switching loss since it decreases the number of series connected switching device and the switching frequency. The staircase voltage waveform is expected to be able to suppress the higher harmonics. We investigated the condition necessary to suppress the higher harmonics and proposes the control method of the fundamental voltage amplitude. We show the effectiveness of the proposed control method from the simulation results using Alternative Transient Program (ATP).

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Corona attenuation and distortion of lightning surge voltage is an important factor in insulation design. An experimental investigation and a simulation of the voltage waveshapes propagation on 1, 2, 4-conductor bundle transmission line have been carried out. However, the propagation characteristic on a UHV 8-conductor bundle transmission line has not been measured. This paper describes the lightning surge propagation characteristics with corona discharge measured on an actual UHV 8-conductor bundle transmission line. The propagation of a lightning wave is simulated with EMTP, taking the skin effect and the corona effect into account. A comparison between the measured and the calculated results shows that the effect of corona can be modeled by a simple RC equivalent circuit. The model parameters are numerically obtained by fitting the calculated results to the measured results. The resistance and the capacitance are identical to the conventional model.

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Insulators in coastal substations are polluted due to the salty wind blowing from the sea. The insulator pollution may cause higher leakage current and ultimately give rise to blackouts due to flash-over. To avoid those accidents, the insulators are frequently washed using much amount of pure water. Almost all measuring devices use a pilot insulator, which is exposed to the same conditions as the actual insulators, and measure the pollution deposits on the pilot insulator at each measurement interval. However, when measuring the pilot insulator (15 minutes), the pilot insulator is not being exposed. Therefore the larger the times of measuring, the more errors will be resulted. This research aims at developing a method of reliable decision making of timing for measuring and washing of the polluted insulators. The proposed method is derived based on the prediction of pollution deposits by use of the insulator pollution model. Effectiveness of the proposed method was demonstrated by applying it to actual data taken from Karatsu substation in Japan.

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This paper addresses the subject of stationary and non-stationary voltage disturbance problems in electric power system. The modified binary-tree wavelet decomposition technique with an appropriate wavelet filter is introduced as a powerful tool for detecting, classifying, and quantifying the voltage disturbances. Power quality (PQ) indices in terms of total rms, rms of individual frequency bands, duration of disturbance, and their dependent quantities such as voltage magnitude of disturbance and harmonic distortion can be measured directly from the wavelet transform coefficients. The proposed technique is simple, provides accurate value of PQ indices, and enables to discriminate among the type of similar voltage disturbance events. The proposed technique is validated by its application to various disturbance data and the measurement results, such as rms and harmonic distortion, are further compared with those obtained from the time domain and frequency domain methods.

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Under circulation of the positive charge in the oil, the positive charge density in the oil increases and the negative charge density in the coil and the leakage current of the neutral line decrease as the return rate increases, about which attentions might be paid in terms of diagnostics.

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Side flash is one of the most important problems of human damages by lightning. Though several guidelines state that you should not be near a tree when thunderstorm activity is high, little is known about the necessary clearance quantitatively. There was a statement that more than 2 meters is needed to avoid side flash, but neither theoretical nor experimental verification of the statement has been carried out. This paper describes the experimental results on side flash using lightning impulse voltages.

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