Regarding specifications and circuit designs of an instrument transformer (Current Transformer: CT, Voltage Transformer: VT) necessary for a protection and control system, this report arranges knowledge such as technical grounds on such designs, because the present state has not been arranged by systematization, though it has been followed from the past to the present.

This paper proposes a novel frequency control method for the management of distributed energy storage resources in AC microgrid. Distributed autonomous controls by the individual prosumers perform an efficient coordination of SOCs which are automatically controlled to a same value that indicates the total SOC in the microgrid. The coordination is realized by the proposed control law that allows frequency deviation in a specified bandwidth. The proposed method has been developed in order for the microgrid operation by SSI, the single-phase synchronous inverters developed by the authors, while useful for general AC microgrid to increase the resilience of power supply.

The reserve market was established in 2021. So far, power producers sell the electricity in the energy market and through the bilateral contract. Currently, power producers can sell the reserve in the reserve market. In order to earn well, they have to sell both energy and reserve. When they sell the reserve in the reserve market, they have to control bands of thermal generators preparing for the activation of the reserve. In this study, we present a unit commitment method which can schedule the operation of bands considering bidding for the energy and reserve market. In order to model this unit commitment problem, we apply a flow network. We link a network of transitions of band with one of transitions of on and off. The numerical results show that trading in the reserve market improves power producer's profit by 4.19% and the proposed method can schedule the operation of bands appropriately.

In recent years, the aggregation business has gained a lot of attention in Japan. Aggregators will make contracts with customers with photovoltaic (PV) power systems and battery energy storage systems (BESSs) including electric vehicles (EVs) to participate in electricity markets. Aggregators might have to pay electricity supply-demand imbalance charges when generated and consumed energies contracted at the day-ahead supply-demand market are different from those at the current day operation due to distribution network constraints such as voltage and power flow limitations. Therefore, the information on network constraints is very important for aggregators to determine their day-ahead schedules. In this paper, we evaluated the relationship between aggregator supply-demand schedules and the distribution system operation. It was assumed that the reverse power flow limitations due to network constraints are notified to the aggregators by distribution system operator (DSO). Two cases of the aggregators' schedules of PV systems and stationary BESSs were compared in the simulations. In addition, aggregator strategies for making adequate schedules were evaluated.

In this paper, the voltage control performance of several types of reactive power control by EV chargers is evaluated for the purpose of maintaining the proper voltage and improving the voltage unbalance ratio in the distribution system when EVs become more widespread. The popularity of electric vehicles (EVs) is on the rise due to environmental constraints such as reducing carbon dioxide emissions. On the other hand, there are concerns that EV charging will make it difficult to maintain proper voltage and worsen the voltage unbalance ratio in the distribution system. This is an issue that needs to be resolved as it will hinder the spread of EVs. However, it is difficult to counter the local voltage drop caused by EV charging with existing voltage control devices such as LRT and SVR. In this paper, we focus on the reactive power control function based on power factor adjustment in EV chargers, and evaluate the characteristics and voltage control performance of several reactive power control methods, from autonomous to centralized. The usefulness of each method was evaluated by numerical simulations using a model constructed based on the actual power distribution system in the Hokuriku area of Japan. From the results, it was confirmed that the reactive power control function by EV chargers contributes to the improvement of the EV installation availability ratio and the voltage unbalance ratio.

In March 2011, the earthquake off the Pacific coast of Tohoku caused a power line and a ground wire in 66kV overhead transmission line to shake heavily. That led a flashover and an AC arc discharge between the power line (TACSR 240mm²) and the ground wire (AC 70mm²), where the current and the duration of the ground fault was 596A and 0.47s, respectively. Consequently, the power line strands (aluminum strands) were melted and 0 out of 30 strands was broken, and the ground wire strands (aluminum-clad steel strands) were melted and 5 out of 7 strands were broken due to the arc of the ground fault. In this paper, numerical evaluations of melting and breaking conditions of strands of the power line and the ground wire were carried out and the calculation results were compared with the conditions observed in the actual line and wire. As a result, the calculated number of broken strands of the power line was 0, which was agreed with that of the actual line. On the other hand, the calculated number of broken strands of the ground wire was 3-4, which was less than that of the actual wire. It is considered that non-broken but partially-melted 1-2 out of 7 strands in calculations were broken due to an arc jet spouted from the arc spot on the melted strands, and the added tension because of the ground wire shaking as well as the normal tension in the actual field.

The Editorial Committee is working on planning and editing the publication of Power and Energy Society. In this article, the committee's activities of the last term are reported, and recent trends and future problems are also discussed. The process of planning and editing the publication and the challenges of reducing the necessary months for reviewing papers and increasing the number of submitted papers are shown.