There have been various discussions in Japan on how to introduce renewable energy toward the target of carbon neutrality in 2050. The “Interim Report for Network Master Plan” issued by the “Study Committee on Master Plans for Wide-Area Interconnection Systems and System Rules” on May 20, 2021 describes the possibility that large-scale, long-distance power transmission from power generation areas to large demand areas by high-voltage direct current transmission system (HVDC) is effective for mass introduction of renewable energy. The introduction of HVDC is already expanding overseas, such as in Europe, and the trend is accelerating. The background to this is that it has been demonstrated that strengthening interconnection by HVDC has economic rationality and that it brings various benefits to existing power systems such as strengthening resilience. This paper describes the latest trends in the HVDC market and technology.

In Japan, power transmission facilities which were introduced in the high economic growth period have degraded with age. Due to simultaneous lifetime of the facilities, it is concerned that reliability degradation of power system. On the other hand, electricity demand has decreased triggered by the Great East Japan Earthquake, and wheeling revenue of electricity transmission utilities has decreased in recent years. Therefore, highly reliable and economical facility planning is an important business issue of electricity transmission utilities. In this paper, we propose a facility planning method that models power system topology change according to environmental changes and makes feasible plans based on the state model.

In power systems, it is necessary to properly manage the reactive power to maintain the voltage within a desired operating range. The voltage in an Extra High Voltage (EHV) system has been maintained by using voltage controllers (Synchronous Generator (SG), Shunt (Shunt Reactor), SC (Static Condenser), On Load Tap Changer (OLTC), etc.). Currently, the introduction of Distributed Energy power Resources (DER) is increasing rapidly and the number of conventional SGs in service which have supported voltage in power systems are being decreased. Hence, it is highly required to realize more flexible voltage regulation even with the DER integration in order to avoid voltage deviation caused by insufficient reactive power support from the conventional SGs.

This paper proposes the Centralized Voltage and Reactive Power (Q) Control (VQC) which can manage the control setpoints of Local VQC in substation. The proposal controller monitors the short circuit capacity and updates the dead band width depending on the step size of the voltage control. The control effect of the Local VQC combined with the proposal controller was verified through numerical simulations by using a developed VQC simulation software.

We conducted a lightning damage survey in Tohoku region from 2010 to 2019, and classified the damaged items by infrastructure installation. Among them, explosive damages such as windowpanes and shoji (a sliding paper door) of historical buildings, and those of walls and pillars of ordinary houses have been confirmed. As explosive damages can have a significant impact on buildings, we have investigated the mechanism of damage occurrence and clarified the relationship between explosive damages and the properties of lightning. In addition we considered the effects of explosive damages on the human body.

In restricted slit-like space by two polymer plates, the effects of the space width, current and atmospheric pressure on arc electrical field were investigated experimentally for high-current air arc above several kA. As a result of the evaluations, it was found that the electrical field increases significantly with the pressure rise under condition near 0MPa-g, and it increases with current in the restricted space at the width less than 10mm. Comparing the electrical field in using polymer with glass for the restricted material, it revealed that the electrical field has current dependence caused by the space width in addition to increasing effect to above 1.5-2 times by the ablation or spallation effects of the polymer.

Applying a magnetic field to a water electrolyzer is one of the methods to improve energy conversion efficiency from electrical energy to hydrogen energy. In this study, experiments of alkaline water electrolysis with a magnetic field are carried out to elucidate the influence of a magnetic field direction and a magnetic flux density on cell voltage and bubble movement. In the case with B⊥electrode, the cell voltage decreases with the increase in current density and magnetic flux density, because the bubbles are removed from the electrode and the electrolyte is mixed with Lorentz-force. In the case with B∥electrode, the cell voltage is suppressed in low current density conditions. However, in high current density conditions, the bubbles are trapped in the electrolyte and the cell voltage is increased.