Japan Electric Power Exchange (JEPX) commenced operation on the 1st of April 2005. It provides three types of markets, i.e., a spot day-ahead market to trade the electricity that will be delivered on the following day, a forward fixed-form market to trade the electricity that will be delivered after a certain period of time, and a forward bulletin board market as a place for free transactions. This paper summarizes the role of JEPX in Japanese deregulated electricity market and its trading rules. The performance of JEPX market in the first three months is also shown.
A PV/solar heat/cogeneration system is assumed to be installed in a hotel. The system is operated with various operation methods: CO2 minimum operation, fees minimum operation, seasonal operation, daytime operation and heat demand following operation. Of these five operations, the former two are virtual operations that are operated with the dynamic programming method, and the latter three are actual operations. Computer simulation is implemented using hourly data of solar radiation intensity, atmospheric temperature, electric, cooling, heating and hot water supply demands for one year, and the life-cycle CO2 emission and the total cost are calculated for every operations. The calculation results show that the virtual two and the actual three operations reduce the life-cycle CO2 emission by 21% and 13% compared with the conventional system, respectively. In regard to both the CO2 emission and the cost, there is no significant difference between the virtual two operation methods or among actual three operation methods.
In order to devise countermeasures for harmonic disturbances and harmonic suppression in power systems effectively, it is necessary to develop a harmonic analysis approach with high accuracy. The major harmonic analysis approach is to recreate harmonic distribution in a power system model by using a simulation method. However, in order to carry out high accuracy estimation of the harmonic distribution using the simulation method, after creating a load model which consists of several parameters associated with the measured harmonic impedance, the optimal load model parameters must be determined. So far, appropriate load model parameters have been determined by trial and error. Therefore, a systematic approach to determine the optimal load model parameters is needed to estimate the measured harmonic impedance with high accuracy. In this paper, a determination method for the optimal load model parameters to estimate the measured harmonic impedance is proposed. The proposed method is based on Particle Swarm Optimization (PSO), which is one of optimization methods by using concept of swarm intelligence. In order to check the validity of the proposed method, the load model parameters estimated by the proposed method are evaluated using test data and filed data of Hokuriku electric power company.
This paper has described a technique of calculating voltage and power flow state of a distribution system using the information measured with two or more switches with sensors installed in a distribution system. The proposed technique is that, a set of the power distribution section where two or more switches with a sensor are connected is defined as the large section, and the active power and reactive power consumption in the large section are calculated based on measurement information, voltage (RMS), current (RMS) and power factor. Using the simple distribution system model that consisted of the large sections, the power consumption of the large section is calculated by the power flow calculation to separating power consumption and power distribution loss. It is distributed to the small sections that constitute the large section, and detailed power flow calculation is performed. Verification of the proposal technique and basic estimation of the calculation error were performed using the simple power distribution system model.
In recent years, distributed resources such as photovoltaic power generation system or wind-turbine generator system are increased, therefore the distributed resources which connect to distribution networks are increased gradually. Under the situation there are several problems such as expansion of the voltage fluctuation, increase of the short circuit current, increase of harmonics phenomenon which we have to consider, and the problems make us difficult to examine the effect of interconnection and to design the distribution system. However, analysis support system to evaluate the influence to connect distributed resources to low voltage distribution system has not developed. Therefore We have developed the analysis system for low voltage for low voltage distribution systems. We can evaluate the influence of distributed resources accurately, examine the interconnection and design the configuration of distribution networks by using the analysis system. In this paper, the concept of the analysis system, the load flow method for unbalanced V-connection 3-phase 4-line distribution system and the calculation method for the connectable capacity of distributed resources. Outline of the man/machine interface and examples of calculation results for sample network are also described.
In the assessment of future energy systems including small-scale distributed generators, a proper assumption of energy transmission infrastructures, i.e. electricity transmission lines and gas pipelines, is very important. This paper describes a modeling of proper allocation of energy transmission infrastructures for a given demand area. Material use (or total weight) of infrastructure is used as a measure of optimization in this paper, while various measures such as cost can be applied also. The total weight is determined by a trade-off relationship between the transmission section and the distribution section, i.e. the lower parallel number of transmission section reduces the weight of transmission section but increases the weight of distribution section. The model calculates the total weight for various combinations of transmission and distribution sections, taking into account the nature of tree-type energy transmission infrastructures, i.e. increasing parallel number and lowering voltage class along the energy flow. We tested the proposed model for various cases with different demand distribution. The simulation results suggest that the proposed model is a practical tool for estimating a reasonable conformation of energy transmission infrastructure depending on demand distribution, and is useful for energy system assessment.
An improved power system with many potential good properties may be obtained with introduction of Superconducting Generator (SCG), which has a superconducting field winding that leads to many advantages such as small size, high generation efficiency, low impedance, and so on. Many researches have confirmed the improving-effect of SCG on power system stability. In this work, the influence of SCG on power transfer capability is studied by way of conducting real-time simulation using a digital type SCG model and an existing analog type power system simulator. In the real-time simulation with a 5-machine infinite bus power system model, ATC (Available Transfer Capability) from generator site to load site are examined and, comparison is done between the ATCs in cases of SCG and the conventional generator (CG). The real-time simulation results have verified the effect that SCG can improve the ATC of power system and illustrated the advantage of SCG over CG from the point view of ATC enhancement.
Grounding resistance is one of the important parameters in the lightning-protection design of electric power systems. The grounding resistance of electrode decreases as large currents are injected to the electrode by electric discharges in soil. This characteristic is not considered in lightning protection design. Therefore, the design level is kept on the exceeding level in actual phenomena. From viewpoint of the rational lightning protection design for the electric power systems, this characteristic should be considered in practical design. In this study, experiments were conducted using rod electrodes, and the physical phenomena of the electrical discharge in soil were considered by assuming a certain electrical discharge model in soil. Based on these results, a grounding resistance large-current characteristic analysis model that could be easily used in EMTP was developed.
In order to understand overvoltage phenomena due to the lightning surge in a low voltage wiring on a scale model of a structure, the load circuit of electrical appliances at the end of cable with circuit elements, such as resistors, capacitors and inductors, was simulated and the response at the end of cable was studied. Furthermore experimental results were compared with those of the digital simulation using EMTP (Electro-Magnetic Transients Program). The variation in the voltage waveform generated at the end of cable according to the state of the load of an electrical equipment was confirmed based on experiments and simulations. However, when a varistor (Surge Protective Device) was inserted at the end of cable, the voltage amplitude was clamped by the varistor irrespective of the load circuit.
Lightning protection measures for wind turbines are becoming important as the use of wind turbines is increasing rapidly along with its capacity and height. In order to understand the manner of lightning attachment to wind turbine blades, experiments with various types of blade samples were conducted. Experimental studies revealed following issues. Regarding a non-conductive blade sample, the 50% flashover voltage of polluted blade sample was reduced by 10% as compared to a non-pulluted blade sample. Creeping discharges on the polluted blade samples occurred more frequently, and penetrated through the surface, damaging the blade sample. The blade sample with a receptor system showed lower protection performance than the blade covered with a conducting cap.
The decay time of residual dc charge in a 500kV transmission line had once been measured during five fine and dry days of winter season. The results showed a large scattering without depending on the simultaneously observed weather conditions, such as temperature or relative humidity. Then the authors have performed an additional experiment in a laboratory to discuss the factors that affect the residual dc charge leakage in a dry condition focusing on the moisture in the air and the dusts floating in the atmosphere. It is shown that absolute humidity alone decides the decay time without scattering under clean and calm condition. The floating dusts blown up by the wind, however, reduce the decay time and bring a large scattering. The dusts should be a charge carrier moving freely in the atmosphere.
A kA-class fault current limiting unit (FCL unit) with YBCO thin films has been developed. The size of the YBCO film on a sapphire substrate with a metal shunt layer is 3cm in width and 10cm in length. The kA class unit consists of eight films in parallel. A polygonal arrangement of the YBCO films selected to keep the current distribution uniform. Moreover, the return pass of the current is set at the center axis of the unit. The model, connected to two units in series, was tested for normal operation and current limitation. The model carried 1kA for 1hour and 1.2kA for 5min without quench at normal operation, and the current distribution between the films was uniform. The short circuit tests were performed against a power line that has a prospective fault current of 8.9kA. A total of eight tests were successfully carried out at 200V, 3.5 cycles, and the model limited the fault current to 1.2kA.