The Electromagnetic Transients Program (EMTP) is a common software for analyzing the electromagnetic transient phenomena, the electromechanical dynamics, and the control system transients in electric power systems and electronic circuits. Since the late 1960's, the EMTP has been developed by many contributors, and various capabilities, functions and auxiliary programs have been added to the EMTP. In the first half of the paper, history of Japanese EMTP Committee (JEC) and its activity is described. The basic policy of the JEC is “neutral” and “public domain”. The objectives, members, recent workshops and publications are introduced in this report. The activity of the JEC covers any EMTP version, such as ATP- and DCG-EMTP, derived from the BPA-EMTP. The second part of this paper presents the history and products of the EMTP Development Coordination Group Project (EMTP-DCG Project), which is organized to rationalize the development of the EMTP.

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On July 23, 1987, a very hot day, the largest wide-area power outage occurred in Kanto-Area, Japan. The cause was a voltage collapse on the bulk power network of Tokyo Electric Power Company, due to the abnormal rate of demand rising following resume after lunch break. Aggressive studies on voltage collapse throughout industry and university have led to great advances in power system stability. This essay describes the detail record of the outage, the applied countermeasures, and the inside story when the multiple voltage solutions of power flow on actual power system were found out for the first time.

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This paper shows a method that reconfigures the distribution power system by using branch exchange algorithm. The optimal reconfiguration method calculates line loss and voltage condition in all possible power system configurations depending on line on/off, and it searches for the most appropriate optimal configuration. However, it is not easy to search for the solution for the most appropriate optimal configuration in distribution power system for a short time because there are a number of connection & sectionalized switches in distribution power system and it should comply with the condition of radial operation. Therefore, this research shows the method that not only reduces the whole system loss by using branch exchange algorithm which has the advantage in time, but also complies with the condition of radial operation and the constraint condition of voltage.

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Market splitting is one of the methods to solve the transmission congestion problem associated with the introduction of competitive electricity market and transmission access. Based on the concept of price difference among congested areas, the market splitting approach produces a solution that strongly informs market participants of congestion path. In this paper, an algorithm to solve the market splitting problem for complex networks including loop structures is proposed. The method, based on an algebraic approach, ensures a feasible optimal solution verifiable and easily understandable by the market participants. Complex networks are transformed into simple radial ones using the delta-star approach. The method was tested on large problems to evaluate the performances.

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Ocean Thermal Energy Conversion (OTEC) converts heat energy into electricity using 20-27[°C] temperature difference between warm seawater at surface and cold seawater in depth. In this paper, a simulation model for an OTEC plant, which uses the Uehara cycle with an ammonia-water mixture as working fluid, is constructed based on the mass balance and the heat balance. Moreover, a method of the initial value determination for numerical simulation is developed. Accuracy of the simulation model was evaluated by comparing with the experimental results of a pilot OTEC plant.

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A direct load management scheme with two-way communication while considering end users comfort is proposed. First, the control algorithm is developed and the data required to be transmitted between system operator and controllable loads is identified. Then, the actions of controllable air conditioners and the power adjustment of dispersed generators to eliminate overloads in a substation transformer are simulated. The results indicate that the proposed load management technique performs effectively to reduce overloads on the transformer while maintaining energy consumption in each loads, and the performance is improved by coordination with the output of dispersed generators.

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It is important to grasp the actual condition of power quality before attempting to maintain appropriate levels. Some data on power quality, such as on the harmonic voltage, are available but their actual conditions have not been clarified as a whole. This report analyzes power quality data in further detail and clarifies the following points:
The level of power quality varies due to two reasons: location and time. Overall, the distribution of voltage distortion is similar to a logarithmic normal distribution because the distribution due to location is similar to a logarithmic normal distribution. However, the distribution of the cube root of voltage unbalance is similar to a normal distribution. The distributions due to time are nearly symmetrical for both voltage distortion and voltage unbalance.
Analysis of measured data from 1999 to 2006 revealed that the recent annual trend of voltage distortion was certainly decreasing. The Japanese government issued limits on harmonic currents from home appliances in 1994. Thus, it seems to have taken five years for the effect of these limits to appear as the appliances that were in use in 1994 were slowly replaced with ones that conformed to the limits.
When power quality is measured, it is important to determine the reliability of the measured data. The number of measuring points necessary to estimate confidence intervals was clarified. To estimate them within a ± 10% error, 50 and 120 measuring points are necessary for voltage distortion and voltage unbalance, respectively.

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In power systems, Resistor type Superconducting Fault Current Limiters (RSFCL) can limit the prospective short-circuit currents to lower levels, so that the underrated switchgears can operate safely. Besides, RSFCLs can enhance the power system transient stability if they are accompanied by appropriate shunt resistances. This paper presents a method of optimum shunt resistance determination for transient stability improvement. The method is based on minimization of rotor kinetic energy oscillations. Meanwhile to make it more comprehensible, the method is utilized to determine the shunt resistances of three RSFCLs installed in a 9-bus 3-generator sample network. All of the simulations have been carried out by EMTP/ATP.
The paper begins by modeling an RSFCL. Then RSFCL critical current determination is discussed in a model system. Finally, a method of optimum shunt resistance determination for transient stability improvement is presented.

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In past studies, after thin straight copper wires of 0.1mmφ were exposed to an impulse current, their temperature rose; they melted according to the specific pre-arcing Joule integral in an adiabatic state. However, in this study, we confirmed that thick straight copper wires of 1mmφ and over it were broken in a solid state before melting The effect of physical damage on copper wire performance was confirmed. The test data suggest that ohmic heating is the main reason for thin (less than 1mmφ) copper wire breakage in the experiments. However, the magnetic force and skin effect are primarily responsible for breaking thick copper wires rather than thermal failure, as previously thought. And the thicker the copper wires diameter was, the more noticeable the magnetic force and skin effect were. Then the impulse current was impressed through curved copper wires from 0.3mmφ to 2.0mmφ. Because of different breakage mechanism for thin and thick copper wires, the current-carrying capability of thin curved copper wires did not change comparing to that of straight ones. However, the current-carrying capability of thick copper wires greatly decreased when they were curved.

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This paper describes an influence of wind turbulence on yaw-control gears of nacelle in a wind power station. This site is located in Tappi cape of Aomori prefecture where is characterized by a big wind turbulence due to the western strong wind and a steep slope of the cape. In this paper two adjacent wind towers are dealt with among eleven ones. To clarify an influence of the wind turbulence on the leeward wind power generator. The measurement results showed that the turbulence and the standard deviation exceeded IEC Wind Turbine Standards frequently. Accordingly the torque applied to the yaw control gears vibrated with short time period and its magnitude was frequently larger than 4.8 ton-m (47kN-m) regarded as the metal fatigue limit. By the method where the output of the wind turbine generator is controlled, the magnitude of the vibrating torque can be reduced under the limit of the material fatigue.

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In the field of electrical power system, various approaches, such as utilization of renewable energy, loss reduction, and so on, have been taken to reduce CO₂ emission. So as to work toward this goal, the total number of distributed generators (DGs) using renewable energy connected into 6.6kV distribution system has been increasing rapidly. The DGs can reduce distribution loss by appropriate allocation. However, when a fault occurs such as distribution line fault and bank fault, DGs connecting outage sections are disconnected simultaneously. Since the simultaneous disconnection of DGs influences restoration configuration and normal configuration after the restoration, it is necessary to determine the system configuration in normal state considering simultaneous disconnection of DGs.
In this paper, the authors propose a computation method to determine the loss minimum configuration in normal state considering reconnection of DGs after simultaneous disconnection by fault occurrence. The feature of determined loss minimum configuration is satisfying with operational constraints even if all DGs are disconnected from the system. Numerical simulations are carried out for a real scale distribution system model with 252 sectionalizing switches (configuration candidates are 2²⁵²) and 120 DGs (total output is 38.46MW which is 23% of total load) in order to examine the validity of the proposed algorithm.

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Lightning striking characteristics to wind turbine blades have been investigated by the model experiments with actual turbine blades. The effects of various types of receptors, polarities of applied voltages, pollution on the blade surface have been clarified. Based on these experimental results, lightning protection design of actual wind turbine blades by receptors has been discussed.

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To improve insulation specification of a gas insulated switchgear (GIS), it is necessary to recognize the insulation characteristics of SF₆ gas under actual surge (called non-standard lightning impulse waveform) occurring in the field substation. The authors had observed the insulation characteristics of SF₆ gas gap under various types of non-standard lightning impulse waveforms and compared them with under standard lightning impulse waveform quantitatively. From the investigation of the experimental results, the evaluation method for real surges is shown and the method is applied to typical surges for various UHV and 500kV systems. In the proceeding study, therefore, only for the quasi-uniform electric field (with a typical range of the field utilization factors in the bus of a GIS) was investigated. In this paper, the insulation characteristics of SF₆ gas gap for non-uniform electric field were observed experimentally and investigated about the evaluation method of converting non-standard lightning impulse waveforms equivalently to the standard lightning impulse waveform.

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A nearby lightning strike can induce significant currents in long horizontal and tall down conductors. Although the magnitude of the current in this case is much smaller than that encountered during a direct strike, the probability of occurrence and the frequency content is higher. In view of this, appropriate knowledge of the characteristics of such induced currents is relevant for the interpretation of recorded currents. Considering these, the present paper discusses a modeling procedure that permits simulation of lightning-induced voltages or currents on overhead lines due to a nearby lightning strikes. In this paper, homogeneous non-perfect ground is also examined to investigate the influence of soil conditions on induced effects.

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As a circuit breaker for over 84kV, SF₆ gas circuit breaker (GCB) has been used for a long time, in virtue of its excellent characteristics as arc extinction and insulating medium. Although, SF₆ gas has very high global warming potential (GWP) of 23,900, and it was designated to regulation object in COP3 in Kyoto in 1997.
A lot of efforts have been done to reduce the amount of SF₆ gas usage and emission from conventional equipments. On the other hand, SF₆ gas free equipment has been researching and one strong candidate is air-insulated type switchgears with vacuum interrupters. In last few years, air-insulated switchgears, which include GIS, Cubicle type GIS (C-GIS) and dead tank type VCB, have been developed in succession. So far, we have already more than three years operation record for the air-insulated dead tank type VCB, and over 100 units is in-service in power systems. Recently, VCB technology, that is essential for SF₆ gas-free equipments, has been advanced in the field of high-voltage, large current interruption and environment-conscious design. In this paper, the advanced dead tank type VCB and its technology is descried.

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Experimental study on behavior of boundary layer in supersonic flow with applied Lorentz force was carried out. In the experiment, Mach 1.5 supersonic wind tunnel driven by a shock-tube was used. At the test section, the current from the external DC power supply and the magnetic field of 2.4 Tesla were applied to the boundary layer developing on the bottom wall. Argon seeded with cesium was used as an electrically conducting gas. Effect of the direction of the Lorentz force on static pressure distribution was investigated, and the remarkable increase of static pressure at the test section was observed for the decelerating Lorentz force. It is noted that the acceleration of the flow inside the boundary layer was demonstrated for the first time without accelerating the main flow when the accelerating Lorentz force was applied. At the same time, the acceleration efficiency defined by a ratio of work done by the Lorentz force to energy input into the flow was found 54-61%. These results have suggested the possibility of the boundary layer separation control by applying the accelerating Lorentz force. In the case of the decelerating Lorentz force, the significant reduction of Mach number was observed not only inside the boundary layer but also in the main flow. The reduction of Mach number could be ascribed to the growth of the boundary layer due to gas heating inside the boundary layer. When the direction of the current was changed, the difference of light emission from the discharge inside the boundary layer was observed, and this was due to the difference of the electromotive force induced in the supersonic flow.

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Gas insulated switchgear (GIS) have been demanded reliability and economical efficiency. Circuit breaker (CB), disconnecting switch (DS), and earthing switch (ES) have been designed toward compactness. DS is required the performance of insulation and current interruption. The bus-transfer current is the highest among all current interruption requirements for the DS. To develop an alternating current DS with the low speed driven, it is necessary to reduce the electrode damage. This paper describes the fundamental characteristics of current interruption in the magnetically driven arc using spiral electrode. Since the arc is rotated by magnetically force, the arcing time with spiral electrode is shortened to about 1/3 compared with that of plain break electrode. The DS by magnetically driven arc was confirmed to comply with bus-transfer current switching requirements on JEC standard. Moreover, the physical model of the magnetic driven arc was constructed, and the behavior of the arc could be evaluated quantitatively. As a result, performance of current interruption became to be predictable.

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