Lightning protection for transmission and distribution lines and substations is a quite important issue from the viewpoint of improving the reliability of power systems. The social effect by a strong lightning which rarely occurs is so critical, so the understanding of the characteristic of natural lightning is necessary. It is desirable to directly observe the lightning for the reveal of its property, but it is a very difficult to predict where the lightning strikes on the ground. For this reason, the data sets of the direct observation result of the lightning are limited, and the detailed characteristic of the lightning phenomena has not been achieved. This paper introduces the technological change by looking back on the history of lightning observation from the past to the present.

Smart meters are installed in consumers connected to the power distribution system, and their power consumptions are measured. The authors aim to estimate the state of the distribution system from the measured values of smart meters and sensor-equipped switchgear. In this study, we report the results of our investigation on the possibility of identifing the phase connecion of single phase load connected to transposed distribution line by estimating the three-phase individual current and voltage profile.

The paper is proposed approximate formulas of the ac resistance of lead wires and coils which made by using copper clad aluminum (CCA) wires. There are the frequency range that the ac resistance of CCA wires is lower than it of cupper solid wires for lead wires and coils of an electrical equipment. It is shown that the application of CCA wires is economical as comparing with copper solid wires, if the design is due to successful calculation in the electrical equipment. The measured resistance is compared with the formula. CCA wires is an example of multiple conductors which shall be expected to apply in future.

To improve the lightning-outage-rate calculation method of medium-voltage distribution lines, it is important to accurately assess sparkover rates of insulators. In salt polluted areas, lightning outage rates may increase due to the deterioration of insulation performance of insulators. Although the sparkover characteristics of salt-polluted insulators against the standard lightning impulse voltage have been reported in previous works, the sparkover characteristics against short-wave-tail lightning impulse voltages, which occur across insulators on distribution lines by direct lightning strikes, still remain not clarified.

In this paper, first, we experimentally study the sparkover characteristics of salt-polluted insulators against a short-wave-tail lightning impulse voltage. Second, using the measured sparkover characteristics, we evaluate the influence of salt pollution on the sparkover rate of medium-voltage distribution lines due to direct lightning strikes.

In remote areas such as mountainous regions, we are building a search system that uses a drone equipped with a wireless LAN access point to communicate with the cell phone of a person in distress. In this research, a small computer is mounted on an autonomous drone, which communicates with the distressed person's smartphone or other communication device via wireless LAN to search for the person.