In developed countries, the maintenance of ageing electric power equipment is an important issue, and rational measures are being pursued. This article presents the background to the focus on the asset management technique in the field of maintenance and management, the current situation and examples of specific approaches.

A large number of photovoltaic generation systems (PV) are being introduced into distribution systems. Massive PV integration requires some technical challenges such as voltage control, unbalance compensation, feeder capacity management, etc. The authors focus on the restoration process after the feeder line failure. In the restoration process, the power flow observed before the failure occurrence is often used to certainly avoid feeder overloading and voltage violation during the restoration process. However, most of the PVs are suspended by the islanding detection system, and therefore, the actual loading under the restoration process would differ from the observation before the failure. For a reliable restoration, feeder current estimation based on the actual load is important. This paper proposes a load-generation disaggregation method for an arbitrary area based on the measurement information from smart meters and IT switches. The numerical case studies for the distribution network model with 4,320 consumers were carried out to validate the estimation performance.

This study simulates supply-demand operation based on Electric Vehicle (EV) travel data and examined the impact of the amount of V2G controlled EVs installed on supply-demand operation. We evaluated the effect of reducing supply and demand adjustment costs by converting all buses, trucks, and passenger cars in the Kanto region to EVs and not converting to EVs, with a renewable energy (RE) ratio of 0-50%. In all cases, even taking EVs operation into consideration, the installation of V2G controlled EVs were confirmed to reduce the demand and supply adjustment cost. In addition, it is observed that fuel costs can be minimized by utilizing the adjustment capability of EV batteries to perform the respective functions of supply, surplus, and balancing in response to the ratio of demand and RE. The study also highlights the significant reductions in social costs achieved through the installation of EVs when considering fuel conversion and the cost of increasing stationary storage batteries.

Currently, load frequency control (LFC) in Japanese power systems is carried out in the individual control areas, and the control signal is allocated to regulated generators based on their ramp rate (RR method). In the future, a wide-LFC-system will be implemented and the LFC signal will be created by merit-order of the generators (MO method) instead. However, this approach is result in increasing frequency fluctuations. Moreover, when remote generators are controlled for the wide LFC, the tie-line available transfer capability (ATC) of the interconnection lines have to be taken into account for the LFC signal creation. To address these challenges, this paper proposes an LFC signal dispatching method that decomposes the Area Requirement (AR) signal in a layered manner to benefit from the advantages of both the RR and MO method. A simulation study shows that the proposed method has a potential to achieve both economic efficiency and frequency stability under the ATC constraints.

In order to investigate measures to prevent damage to low-voltage circuits caused by direct lightning strikes to communication towers in electric supply stations, an impulse test was conducted and evaluated the effect of improving the grounding structure on reducing surge voltage in low-voltage circuits. The measures to improve the grounding structure include: (1) Reduction of the current itself flowing to the building ground wire. (2) Suppress the potential difference that occurs between the ground of the transformer for the power supply in the station and the building ground. (3) Eliminate the mixing of low-voltage cables with metal shielding (grounding at both ends of the shielding layer) and low-voltage cables without metal shielding. As a result of the experimental verification, we have confirmed that each of the three methods is effective in reducing the surge voltage generated in low-voltage circuits.