In this paper the basic control and application technologies in high current energy systems are described. The control technology consists of mainly current capability and electro-motive force of conductors and arc plasma phenomena such as the radiant power and torches. And the application deals with mainly concept of applications and the plasma treatment of hazardous wastes.

抄録全体を表示

Perfluorinated compound (PFC) gases, which have large global warming potentials, are widely used in plasma processing for etching and chamber cleaning. In this work, C₄ F₈ gas abatements in the effuluent from semiconductor manufacturing tools are examined by employing an inductively coupled plasma with multi-mode antenna. In particular, an advantage of plasma electron energy reduction is exclusively studied in PFC abatement of the effuluent.

抄録全体を表示

We developed a multifunctional vacuum interrupter that has three functions: current interruption, disconnection, and earth operation in a vacuum vessel. Using the multifunctional vacuum interrupter, we realized 24 kV, 630 A, 25 kA rated switchgear that do not use SF₆ gas. In addition, we could downsize the switchgear greatly compared with conventional switchgear by applying excellent vacuum insulation characteristics. In this paper, we report the backgrounds and the solutions of the following technical problems regarding vacuum insulation inside the multifunctional vacuum interrupter: (1) Improvement of breakdown voltage between the vacuum vessel and high voltage flexible conductors, (2) optimization on the shape of shielding electrodes set at both ends of an insulating rod, (3) removal of conductive micro particles and improvement of breakdown voltage between contacts by using AC working voltage, and (4) identification of long-term reliability of vacuum insulation under the continuous application of AC working voltage.

抄録全体を表示

The decaying aspect of the conductance of an arc after a current zero for SF₆, N₂, O₂, air, c-C₄F₈, CO₂, H₂, He and Ar was studied on the basis of thermodynamic and transport properties of high temperature gases: a mass density ρ, an enthalpy h, an enthalpy h₃₀₀ at 300 K, a specific heat C_P, and a thermal conductivity κ and an electrical conductivity σ. Theoretical calculation revealed two principal phenomena as follows:(1) for the case in presence of gas flow, the conductances for SF₆, c-C₄ F₈, O₂, CO₂, H₂, He and Ar decay rapidly just around a current zero and (2) the conductances for H₂ and He in no axial gas-flow decrease in an almost similar aspect to that for the case in presence of the gas flow. To explain the phenomenon (2), a thermal diffusivity α expressed as α = κ /(ρ C_P) was calculated. The H₂ and He proved to have very much higher α than the others. This higher α of the H₂ and He was found to result in the more rapid reduction in the conductance through a thermal conduction mechanism. To interpret the phenomenon (1), β expressed as β =(h-h₃₀₀)/(ρC_P) was calculated. The SF₆, c-C₄ F₈, O₂, CO₂ and Ar were found to have higher β than N₂ and air. This higher β of SF₆, c-C₄F₈, O₂, CO₂ and Ar proved to cause the more rapid diminution in the conductance through convection mechanism.

抄録全体を表示

Fault current limiter (FCL) is a power apparatus which suppresses the fault current by generating the limiting impedance when the fault occurs and expected to be applied to electric power system. In the design of the FCL, it is important to choice the limiting impedance properly according to the purpose of the introduction of FCL, the installed location of the FCL in the power system and so on. In this paper, we investigated the influence of the magnitude and phase angle of the limiting impedance on the current limiting performance in the steady state after the FCL started the limiting operation based on the circuit theory. We supposed two installed locations of the FCL, i.e., the bus exit and bus tie. In the case of the introduction of the FCL on the bus exit, the limiting impedance having same phase angle as that of system impedance can bring about the highest limiting effect for same magnitude of limiting impedance. On the other hand, in the case that the FCL is installed on the bus tie and relatively high limiting performance is desirable, there is the situation where the limiting effect grows with phase difference between limiting impedance and power system.

抄録全体を表示

We evaluated the performance of systems composed of a solid oxide fuel cell (SOFC) using electrochemical direct oxidation of methane and a conventional steam-reforming-type SOFC (SRSOFC). Net thermal efficiency in an atmospheric partial-oxidation-type SOFC (POSOFC)-SRSOFC system was 8% higher than that in a simple SRSOFC system in the output range of more than 35 kW. The efficiency in a pressurized POSOFC-SRSOFC-gas-turbine (GT) system was slightly higher than that in a pressurized SRSOFC-GT system.

抄録全体を表示

To clarify the attachment manner of direct lightning stroke on power distribution lines with nearby trees, several experiments have been conducted to examine how the discharge occurs when an open wire as an overhead ground wire is placed near a 3.5 m tree. In the next phase, our focus is placed both the characteristics of lightning impulse discharge and switching impulse discharges on an experimental distribution line and a live 13 m tree. The results showed that the status of sparkover and pre-breakdown phenomena closely coincided with the previous experimental results obtained using an open wire and a 3.5 m tree. This finding proved that a direct lightning stroke to the distribution lines could be brought about by both the rapid progress of leaders from the overhead ground wire and the effect of the tree’s discharge attraction when trees were placed close to the lines. From this study, it was found that a tree’s shielding effect for the distribution lines is not effective; thus, countermeasures against direct lightning applying overhead ground wires and arresters are necessary when the distribution lines and trees exist close together.

抄録全体を表示

For insulation design of 22 kV overhead distribution lines, major guidelines have been specified: (1) Have enough insulation ability against the line’s internal abnormal voltage, while arresters are used against external abnormal voltage such a lightning surge. (2) Decrease the line insulation level by using specific arresters capable of regulating the switching surge, resulting in an overall BIL decrease. The first specification is commonly adopted because the arrester’s absorption energy against the switching surge is not yet identified. The revised JEC testing voltage standard specified further lowered the insulation level (LIWV 100 kV), but its target was only for the 22 kV overhead distribution lines in a resistance grounded neutral system. Recently, focus is placed on studying for protecting the lines from direct lightning strikes, thus a variety of lightning protection equipment is widely applied on the lines. Consequently, guideline (2) above is also taken into account. In short, 22 kV overhead distribution lines will achieve both decreasing insulation level and improving lightning protection ability by installing many arresters for LIWV 100 kV in an isolated neutral system. Given these circumstances, to make this idea feasible, the authors studied the absorption energy of the proposed arresters against the internal abnormal voltage of the 22 kV overhead distribution lines in an isolated neutral system. The results revealed that the arresters are well applicable to the 22 kV overhead distribution lines.

抄録全体を表示

This paper proposes an algorithm to simulate the transactions that take place in a free market of electricity. The algorithm presented is used for Bilateral Transaction Matrix (BTM) creation assuming that a day ahead load forecast is previously known. Bids can be made by both the generation side and the demand side to determine transaction prices, then the algorithm allocates the transactions according to market rules until the demand is satisfied. This creates feasible BTMs that can be used to study system security and to find future methods to regulate bilateral transactions through market mechanisms like the application of penalties to the transactions that affect the system’s security. Results show that the proposed algorithm is a good option for electricity market analysis. The proposed algorithm provides system planners with a practical tool for data creation to further study the effects of bilateral transactions in a deregulated electricity market.

抄録全体を表示

420 kV-63 kA single break gas circuit breaker (GCB) has been developed⁽¹⁾. The authors show the steps to develop new interrupting chamber and circuit breaker by using various techniques. At first two interrupting chamber models are considered and investigated conducting electric field calculation and pressure measurement at the top of fixed arc contact, and capacitive current switching test is conducted especially with short arcing times. According to the test results, basic dimensions of interrupting chamber for development is determined. Pre-series CBs are manufactured, then it is confirmed that the breaker can produce the pressure rise in puffer cylinder (ΔP) as the predicted value by calculation and can interrupt short line fault (SLF) current. The driving energy is confirmed to be sufficient by conducting asymmetrical 100% breaker terminal fault (T100_a) current interruption tests. All the type tests according to IEC are successfully conducted at the international neutral test station for the breakers for commercial use reflected the above results. The GIS layout with the above mentioned single break GCB can reduce the installation area in half comparing the case with the existing two break GCB.

抄録全体を表示

One of the serious problems that may happen in power XLPE cables is destruction of insulator. The best and conventional way to prevent such a crucial accident is generally supposed to ascertain partial corona discharges occurring at small void in organic insulator. However, there are some difficulties to detect those partial discharges because of existence of external noises in detected data, whose patterns are hardly identified at a glance. By the reason of the problem, there have been a number of researches on the way of development to accomplish detecting partial discharges by employing neural network (NN) system, which is widely known as the system for pattern recognition.
We have been developing the NN system of the auto-detection for partial discharges, which we actually input numerical data of waveform itself into and obtained appropriate performance from. In this paper, we employed Descrete Wavelet Transform (DWT) to acquire more detailed transformed data in order to put them into the NN system. Employing DWT, we became able to express the waveform data in time-frequency space, and achieved effective detectiton of partial discharges by NN system. We present here the results using DWT analysis for partial discharges and noise signals which we obtained actually. Moreover, we present results out of the NN system which were dealt with those transformed data.

抄録全体を表示

This paper has investigated a surge propagation characteristic of an 1, 100 kV transmission line based on field test results and EMTP simulations. It has been made clear by the EMTP simulations that the archorn voltage is almost the same as the phase-wire voltage to earth, and thus the measured archorn voltage can be regarded as the phase-to-earth voltage. Surge-wave deformation after a distance greater than 2 km measured in the field test is analytically explained due to separation of modal traveling waves, the earth-return and the aerial modes, for the traveling times of the two modes become noticeably different. A distinctive feature of the 1, 100 kV line is very small attenuation, about a half of that on a 500 kV transmission line.

抄録全体を表示

This paper proposes a high-speed reclosing operating method to improve for the stability in the power system. The proposed method calculates the reclosing time, taking the case of standard, in which the reclosing is not done using the generator phase angle δ, the anagular velocity ω and the field system voltage ed’. And, the execusion of reclosing time is calculated, considering the acceleration / deceleration energy of the generator in the during fault. It can be expected that the δ is suppressed by this optimum reclosing operation. Therefore, the system stability can be expected to improvement by carrying out the high-speed reclosing, when the fault arose. At present, it has been set at the value which seems to be optimum considering various problems in the reclosing time. However, in those methods, the system stability improvement effect can not be expected. It was demonstrated that the high-speed reclosing method have depression effect of the δ in the computer simulation.

抄録全体を表示

In this paper, the modified Euler type Moving Average Prediction (EMAP) model is proposed in order to operate a dispersed power supply system using new energy in autonomous mode. Furthermore, EMAP model is applied to operate a new type dispersed power supply system consisting of a large scale photovoltaic system (PV), a fuel cell (FC) as well as a small scale superconducting magnetic energy storage system (SMES). This distributed power supply system can meet the multi-quality electric power requirements of customers, and ensures voltage stability and UPS (Uninterruptible Power Supply) function as well. Each sub-system of this distributed power supply contributes to the above-mentioned system performance with its own excellent characteristics. Moreover, response characteristics of this system are confirmed with simulation by software PSIM, and, under collaborative operation methods by EMAP model, the required capacity of SMES to compensate the fluctuation of both PV output and load demand is examined by the simulation using software MATLAB/Simulink.

抄録全体を表示

This paper presents a new continuation power flow method with the nonlinear predictor of the Lagrange’s polynomial interpolation formula. The continuation power flow method is useful for drawing P-V curves. The conventional power flow method to be studied is based on the predictor-corrector method and has a drawback that the linear predictor of the predictor-corrector method results in heavy computational effort with the large step size. That is because the predictor deviates from an actual solution significantly. In this paper, a nonlinear approximate predictor is proposed to reduce the error between the predictor and actual solution, and enhance the solvability of the problem. To construct the nonlinear approximate predictor, this paper makes use of the Lagrange’s polynomial interpolation formula because of the straightforward algorithm. It is expected that the nonlinear approximate predictor reduces the computational time and improves the robustness of the algorithm. The proposed method is successfully applied in the 118 and 235 node systems.

抄録全体を表示

One of the most important issues for power suppliers in the deregulated electric industry is how to bid into the electricity auction market to satisfy their profit-maximizing goals. Based on the Q-Learning algorithm, this paper presents a novel supplier bidding strategy to maximize supplier’s profit in the long run. In this approach, the supplier bidding strategy is viewed as one kind of stochastic optimal control problem and each supplier can learn from experience. A competitive day-ahead electricity auction market with hourly bids is assumed here, where no supplier possesses the market power and all suppliers winning the market are paid based on their own bid prices. The dynamics and the incomplete information of the market are considered. The impact of suppliers’ strategic bidding on the market price is analyzed. Agent-based simulations are presented. The simulation results show the feasibility of the proposed bidding strategy.

抄録全体を表示

Neglect of armature transients of synchronous generator is common to stability studies of large-scale power systems. However the validity of the approximation is not successfully justified yet. This paper presents a framework to justify the approximation based on singular perturbation theory, as well as a method to measure the validity of the approximation based on singular values.

抄録全体を表示