Implementation of Microgrid system is making progress. There are three major reasons for this. The first is the spread of renewable energy as the distributed power source and the graduate FIT. The second is the increase in local production for local consumption represented by regional revitalization. The last is the response to large scale blackouts due to natural disasters that have frequently occurred in recent years, that is, the improvement of power resilience. In addition, the DC system is being re-examined due to its affinity with renewable energy, electric power distribution in geographical vicinity for local production for local consumption, and resilience resistance due to ease of control. The author, for these reasons, describe the application of DC technology in Microgrids and examples of DC Microgrid demonstration experiments.

The authors propose a new and more efficient method to search for fault points by injected short pulse with high frequency into distribution line. This method, which is called as TDR measurement, enables to find the fault point easily by measuring propagation time of the pulse reflected due to impedance change at the fault point. In this paper, the proposed method is experimented in real-scale distribution system with about 700m distance which is isolated by DAS (Distribution Automation System) as outage area. The measurement result shows that an injected pulse with corresponding to utility pole span resolution is able to propagate through about 700m distance, and each reflected wave by several brunches and terminals is observed clearly in the real-scale distribution system. And the measurement result corresponds with the simulation result of the test equivalent circuit model. Moreover, the authors measured reflected waves from a fault point (short circuit, broken wire, or grounding) in test circuit. As the results, reflected waves from every fault point were confirmed by simulation, and they depend on the fault type. We calculated the fault location from the pulse velocity and the propagation time of the reflected wave, and the result nearly corresponded to the actual setting. In addition, the measured wave corresponds to the simulation result using equivalent circuit model of each fault point.

In this paper, we propose a prediction error model of wind power generation considering inter-temporal correlation and examine the impacts of the error on the evaluation of generation system schedules. The increasing installed capacity of renewable energy sources (RESs) raises the risk of supply shortage and surplus in operating power systems. Many researchers have developed a method based on Monte Carlo simulation for generation system scheduling with a large-scale integration of RESs. We propose an autoregressive model for the prediction error of wind power generation to be used for Monte Carlo methods. In addition, we simulated operation of a power system including unit commitment of thermal power plants, and analyzed the impacts of inter-temporal correlation in the prediction error on generation system scheduling. Fuel cost, unsupplied energy and surplus energy were evaluated with the prediction error. The results show the importance of considering inter-temporal correlation in the prediction error of wind power generation on generation system scheduling.

Recently, photovoltaic generation (PV) systems have been integrated into electricity systems in Japan to reduce carbon dioxide emissions and enhance energy security. However, high penetration of PV will cause voltage rise problems especially in suburban distribution systems. One of the promising solutions to address the voltage rise is control of distributed battery energy storage systems by distribution system operators (DSO). When feed-in tariffs for distributed PV end, some customers who own PV will purchase a battery storage system to increase their self-consumption of power. Hence, DSO can reasonably control the voltage by using those batteries if they are located on desirable sites. This paper presents the economic evaluation of batteries as alternative facilities for voltage control such as SVC in each scenario. As a result, the locational capacity value of distributed batteries varied from node to node. The maximum value was 17,800 JPY/kWh/year in SVC 1 scenario, and 8,800 JPY/kWh/year in SVC 0 scenario.

This paper described difference in cutoff frequency of TEm1 modes between the conventional approximate solution followed by the radii of the inner and outer conductors and the analytic solution in the co-axial structure as a single-phase GIS. The analytic solutions were calculated by the Bessel function based on the boundary condition and confirmed the validity by the FD-TD method in the same size structure. As a result, the approximate solution for the TE11 mode is available while the higher modes above TE21 modes are not available when the difference in the inner and outer conductor radii was increased. Thus, a new approximate equation is introduced, which allows us to obtain more precise result rather than the conventional one.

Plasma structure in a pre-ionized inert gas plasma disk-shaped Hall-type MHD generator has been examined under the isentropic gas flow with r-θ two-dimensional time-dependent numerical simulation. Although uniform plasma can be realized for adequate load resistance, non-uniform structure rotating counter-clockwise appears in the downstream region for low load resistance and strongly non-uniform spiral structure plasma rotating clockwise is caused for high load resistance. These plasma structures qualitatively coincide with the experimental observation.

Current transformers (CT) are used to measure the current in power transmission systems. Generally, the CT has an iron core. It is well known when the iron core saturates, the output signal of the CT is distorted in the commercial frequency. In short circuit testing for circuit breaker, when the prospective transient recovery voltage is measured, the CTs for high frequency measurement are often used to measure the interrupting current. However, it is not known the influence of the CT characteristics to the current measurements, for example di/dt and so on. In this paper, points to be noted at the current measurements in short circuit testing are discussed. Current was measured by shunt resistance and CT simultaneously. It was found that there is the difference of the shunt and CT output. Impedance and phase angle of high frequency CT were measured by frequency response analysis. Equivalent circuit of the CT is constructed from the results. The maximum value and di/dt of the CT output were smaller than the true current of the circuit by calculations using the equivalent circuit of the CT.