The latest trends of DC circuit breaker (DCCB) technology, SF₆ alternative gas circuit breaker technology, and high voltage vacuum circuit breaker technology are investigated and systematically summarized, including their interrupting duties and application examples.

Several-hundred gigawatts of photovoltaic power generation (PV) needs to be installed to realize carbon-neutral Japan. Municipalities are expected to set PV installation targets which corresponds to wider area targets, but the allocation method of such target into municipalities are not determined. Also, in suburban and rural areas, installed capacity of PV tends to be larger than the electricity demand, which increases the reverse power flow. To tackle future power system problems, allocation of the future PV capacity between municipalities is one of the most important factors. This paper proposes the future PV capacity allocation method between distribution areas in Chubu region, corresponding to a nationwide of 300GW in 2050. First, PV installation potentials are calculated in each municipality because many datasets are disclosed on a municipality (city, ward, town and village) basis. Second, the allocated PV capacity in each municipality is calculated based on the potential. Results indicate that the sum of PV allocated capacity into solar-sharing and abandoned farmland is more than half of the total capacity. Allocated PV capacity in some municipalities exceeds 50kW per household in 2050, which indicates that countermeasures will be needed such as reinforcement of substations or installation of energy storage systems.

Maintenance of transient stability is important for the stable operation of power systems. However, as a large amount of renewable energy sources are concerned that the transient stability deteriorates. Excitation control systems have been widely used to improve the transient stability. The defect is that only the synchronous generator (SG) near the fault location changes the excitation voltage so much immediately after the fault. In this study, we propose a novel excitation control method based on an event-based wide-area emergency control system. In this method, the SGs that are distant from the fault location play a role to mitigate the first swing as well as the SGs near the fault. The effectiveness of the proposed method is verified demonstrated by numerical simulation for a multi-machine test system.

There are increasing needs to detect abnormal signs of PV power generation system more efficiently. In terms of this issue, fill factor (FF) value of PV array/module is one of important index of its soundness. This paper proposes a novel method to estimate the fill factor of a photovoltaic module (PV module) from its output power. In the firstly step of the proposed method, we estimate the temperature and irradiance from the voltage and current of PV array/module given by MPPT (maximum power point tracking) control of power conditioning system. In the second step, we calculate the estimated FF value taking fraction of the MPP current and voltage by the short circuit current and open circuit voltage reduced by estimated temperature and irradiance. The advantage of proposed method is convenience that we only need MPP current and voltage data and PV array/module specification.

Induction motors and generators are major devices in power systems, and a high-precision induction machine model is required to perform accurate electromagnetic transient analysis in consideration of them. The electrical behavior of an induction machine can be expressed by circuit equations composed of the winding resistances and the self and mutual inductances of the stator and rotor windings. However, due to the difficulty of solving the circuit equations of the induction machine with the equation of motion of the rotor and the circuit equations of the external system simultaneously, almost all conventional models are implemented in the source code of electromagnetic transient analysis programs. Thus, it was practically impossible for users to improve the models. This paper puts forward an implementation method to express the circuit equations of an induction machine by using only basic circuit components and applying the magnetic circuit expression used for transformer modelling. An induction machine model is developed into XTAP according to the proposed method, and the accuracy of the developed model has been validated in this paper.

The purchase of electric vehicles (EVs) has been encouraged from the perspective of global environmental protection, and they have been increasing in recent years. With the spread of EVs, Vehicle-to-Grid (V2G) has been studied extensively in the power system. In many V2G studies, the batteries of EVs are mainly used at the steady state of the grid without power outages, and the charging and discharging are repeated to contribute the electricity supply-demand balancing considering the user benefits in terms of cost. This paper focuses on the automated driving, which is becoming popular increasingly. A new V2G method is proposed that the “automatically controlled EVs” contribute to restore the power outages and supply electricity sustainably at the “emergency state” of the distribution grid. The distribution grid is divided into two sections namely the failure section and the healthy section. A microgrid with EVs and a power supply vehicle, which is called Vehicle-to-Microgrid (V2MG) in this paper, is stationed in the healthy section, whereas the EVs individually supply electricity to the houses by Vehicle-to-Home (V2H) in the failure section. Thus, the EVs must continue to trip between the failure and healthy sections to supply electricity sustainably to the failure section. In this paper, the trip schedule of the EVs for the restoration is formulated as a mixed integer linear programming (MILP), and the effectiveness on the restoration and the sustainable power supply is evaluated by numerical simulations.

Time-dependent, two-dimensional (r-z) magnetohydrodynamic numerical analysis is conducted for a commercial-scale, nonequilibrium MHD generator with a thermal input of 1000 MW to clarify the effect of externally applied magnetic flux density on the control range of output power by adjusting seed fraction and load voltage. The output power is controlled more widely by lowering magnetic flux density, although the isentropic efficiency is forced to be lower. This is because both the operation ranges of seed fraction and load voltage yielding a stable plasma become wide for low magnetic flux density.

In Japan, many distribution surge arresters with an internal series gap have been installed on 6.6-kV overhead distribution lines for reducing lightning overvoltages. In contrast, surge arresters are sometimes damaged by direct lightning strikes to distribution lines, particularly in winter. Measurement of insulation resistance between terminals of the surge arrester and measurement of DC discharge voltage of the surge arrester are generally adopted to detect damaged arresters. However, if metal-oxide (MO) varistors are damaged and the internal series gap is not damaged, it is difficult to detect damaged arresters by the conventional methods.

Therefore, this paper proposes a new detection method of damaged arresters using discharge current waveforms. In the new method, first, the discharge current of the surge arrester is measured when a high DC voltage is applied to the surge arrester through an inductor. Then, the damaged arrester is detected by comparing the current waveform with that of a non-damaged arrester. The detection rate of damaged arresters by the new method is remarkably higher than those by the conventional methods.

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.