Under circumstances such as global warming caused by carbon dioxide and other green house gas and crisis of depletion of fossil resources, recyclable resources such as biomass have captured the world's attention as reproducible resources alternative to petroleum. Therefore the technologies such to manufacture chemicals from recyclable resources have been developed for the achievement of measures for controlling global warming and the low carbon society. Recently, the bioplastic such as polylactic resin is applied to the home appliances and the automobile interior part as substitution of general-purpose plastic Moreover, the insulation oil from the vegetable oil has been put to practical use. The application of recyclable resources is extending in an electric field. In this paper, we introduce the characteristic and the problem of the insulating material made from recyclable resources in the field of the solid insulation.
Recently, the introduction of decentralized generators, such as photovoltaic power generations, has been promoted rapidly. In the future, extensive use of PV is thought to give rise to the daytime surplus electricity, and a household will manage the surplus electricity rationally. The purpose of this research is to propose an innovative electric power distribution system based on packet power transactions. First, this paper explains distributed markets of which the price can easily reflect the geographical diversity of renewable energy availability and load curve characteristic within the local area. Second, this paper exemplifies the specific electronic circuit that makes pulse-shaped power transmission to develop the packet power distribution system. Finally, this paper shows the results of multi-agent simulations of electricity trading to evaluate the usefulness of the proposed system.
This paper proposes the statistical concept of “maintenance sequence” for evaluating the whole maintenances done in the life of power equipment. Stochastic property of maintenance process is modeled by applying the Poisson process. Occurrence of the successive maintenance is sequentially triggered by the fault rate. In this paper, two types of maintenance sequence have been studied. One is the constant fault rate type; the fault rate is constant until the end of sequence, and this type of sequence is applicable to the repairable equipments such as the circuit breaker. Another is the diminishing maintenance period type; the fault rate explosively increases at the end of sequence, and this type of sequence is applicable to the non-repairable equipment such as the power transformer. This paper also discusses the similarity of the transition curve of maintenance sequence and the deterioration curve of the transmission network facilities.
This paper proposes a new multi-objective meta-heuristic (MOMH) method for solving economic load dispatching (ELD) in considering of carbon dioxide (CO2 emission. The objective of ELD is to minimize the fuel cost of generators while satisfying the power balance constraint and so on. In recent years, however, the greenhouse warming becomes serious. Therefore, this paper reformulates ELD to a multi-objective problem that minimizes the fuel cost and the CO2 emission. This is because it is challenging to obtain many Pareto solutions effectively. Therefore, this paper makes use of MOPSO-based MOMH because of the effectiveness of multi-point search. MOPSO is effective for optimizing the continuous variables like the output of generators. In addition, MOPSO is developed to improve accuracy, diversification and the computational efficiency like on-line operation by EPSO and the density information of SPEA2 schemes. The effectiveness of the proposed method is tested in sample systems.
The paper proposes multi-stage long-term generation expansion planning methods to reduce CO2 emission. Firstly, we tackle a two-objective optimization problem with environmental and economy performances. Secondly, multi-stage generation expansion planning to satisfy CO2 emission boundaries with least cost is studied.
With the high economic growth era until 1990s, the power demand increased sharply year by year. Therefore, the electric power utilities installed many electric power facilities along with the predicted demand. However, in recent years, fewer infrastructures have been installed because electric power demand growth is saturated due to low economic growth. Therefore, in electric power facilities planning, it has been necessary to form a rational renewal planning which also considers social influence factors such as the construction quantity. In this paper, we propose a new transmission renewal planning method using Supply-end Reserves and Line Flow Sensitivities. We carry out simulations for the IEEJ EAST 10-machine -O/V model system and determine the transmission planning priority order to confirm the validity of the proposed method.
This paper presents short-term electricity load forecasting using dynamic neural networks, DNN. The proposed approach includes an assessment of the DNN's stability to ascertain continued reliability. A comparative study between three different neural network architectures, which include feedforward, Elman and the radial basis neural networks, is performed. The performance and stability of each DNN is evaluated using actual hourly load data. Stability for each of the three different networks is determined through Eigen values analysis. The neural networks weights are dynamically adapted to meet the performance and stability requirements. A new approach for adapting radial basis function (RBF) neural network weights is also proposed. Evaluation of the networks is done in terms of forecasting error, stability and the effort required in training a particular network. The results show that DNN based on the radial basis neural network architecture performs much better than the rest. Eigen value analysis also shows that the radial basis based DNN is more stable making it very reliable as the input varies.
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. However, when a fault occurs such as distribution line faults and bank faults, DGs connecting outage sections are disconnected simultaneously. Since the output of DGs influences feeder current and node voltage of distribution system, it is necessary to determine the optimal system configuration considering simultaneous disconnection and reconnection of DGs. In this paper, the authors propose a computation method to determine the optimal restoration configuration considering many connections of DGs. The feature of determined restoration configurations is prevention of the violation of operational constraints by disconnection and reconnection of DGs. Numerical simulations are carried out for a real scale distribution system model with 4 distribution substations, 72 distribution feeders, 252 sectionalizing switches (configuration candidates are 2252) and 23.2MW DGs (which is 14% of total load) in order to examine the validity of the proposed algorithm.
A numerical thermofluid model was developed for a simplified circuit breaker with POM or PTFE ablation phenomena to investigate their ablation effect on arc properties such as arc voltage, and temperature distribution. It is well known that polymer ablation occurs in actual circuit breakers, which markedly affects their current interruption capability. In this study, thermal plasma-polymer solid coupling phenomena such as melting and evaporation were calculated without any empirical model based on measurements unlike other existing numerical thermofluid model. Results showed that the ablated mass rate calculated with this model fairly agreed to the measurement. The influence of turbulent model on arc properties was also evaluated. As a result, it was confirmed that it was effective to consider the turbulent model.
This paper has derived analytical formulas of a voltage and a current on a grounding electrode by adopting a simple model circuit composed of R, L and C elements. Based on the formulas, its transient characteristic is discussed, and approximate formulas of the surge impedance and the propagation velocity are proposed. Also, this paper summarizes measured results of transient responses on grounding electrodes with horizontal and vertical arrangements. The characteristics of the measured results are estimated based on the analytical formulas derived in the paper. It becomes clear that most of the measured results show either an inductive or a resistive characteristic as far as the investigated cases in the paper are concerned. In the capacitive case, the transient resistance is not much different from the steady-state resistance. Also, it has been shown that measured steady-state resistances agree well with those evaluated by Sunde's formula for a horizontal electrode.
The wind power stations on the coast of the Japan Sea have high risks to be damaged by upward lightning in winter, so that sometimes lightning towers have been set up as a countermeasure. The upward leader progression model (ULP model) is proposed as a prediction method of lightning protective effect of upward lighting in winter. However, there are only few observational data, so that validation examples of lightning shielding effect using this prediction method are few. One wind turbine and one lightning tower have been set up at the Uchinada wind power station, and the lightning observations have been continued and 77 observational data have been reported so far. In this paper, we have made a comparative study of the lightning ratios estimated by ULP model and by observational data. Although there were some cases that had big differences in lightning ratio due to the wind direction, the final result of general lightning ratio was almost the same. Regarding the wind direction distribution used in ULP model, there were some differences in number between proposed wind direction distribution and observed wind direction distribution. However, it doesn't have a great impact on the calculation of the lightning ratio due to the differences in this paper.
It is possible to predict generating power of the tidal current generation, because of the tidal current's periodicity. Tidal current generation is more advantageous than other renewable energy sources, when the tidal current generation system is connected to the power system and operated. In this paper, we propose a method used to optimize the gear ratio and generator capacity, that is fundamental design items in the tidal current generation system which is composed of Darrieus type water turbine and squirrel-cage induction generator coupled with gear. The proposed method is applied to the tidal current generation system including the most large-sized turbine that we have developed and studied. This paper shows optimum gear ratio and generator capacity that make generated energy maximum, and verify effectiveness of the proposed method. The paper also proposes a method of selecting maximum generating current velocity in order to reduce the generator capacity, from the viewpoint of economics.
Calculations of transient cell voltage response of a high power density type lithium-ion secondary battery are carried out for high-rate and pulse-wave charge/discharge current by using the numerical simulation method already proposed and developed by the authors. In order to confirm the validity of the simulation method, the numerically obtained transient cell voltage responses are compared with the corresponding experimental findings under various conditions. As a result, it is successfully demonstrated that the calculated transient responses coincide well with those obtained through measurements in all cases. This indicates the usefulness of the numerical simulation method of transient cell voltage response proposed and developed by the authors, because it can calculate the transient cell voltage response with sufficient accuracy even in the case a high power density type battery experiences high-rate and pulse-wave charge/discharge current.
Charge transfer is one of the most important parameters when one discusses the damage to the equipments on a power line due to the energy of the lightning. The amount of charge transfer associated with a lightning flash or individual strokes can be estimated by using the electric field change measured with a slow antenna. In this letter, the authors propose a simplified method of analysis of charge transfer associated with cloud-to-ground strokes along with estimation of the height of a charge in the point charge model. The height is evaluated by the product of the average speed of the downward propagating stepped leader and the time difference between the beginning of the preliminary breakdown and the onset of a return stroke.