Although power distribution lines are protected by ground wire systems, there are fears that these ground wires may break at their corrosion points. For practical purposes, they have therefore been removed to avoid maintenance in certain areas. The Tokyo Electric Power Company (TEPCO) has continuously observed lightning strokes and obtained 321 datasets to date. The present study has determined the potential for an anticipated lightning stroke attraction effect based on the observed data, despite the fact ground wires are eliminated while ground wire caps are left in place. Furthermore, a verification experiment using facilities simulating the power distribution system has confirmed the problem of insulated wires being struck by lightning and the extent of the impact of the ground wire cap on the lightning stroke attraction effect. These results are expected to provide a new facility-construction menu, which will help rationalize the lightning protection design.

The number of home electric appliances, such as personal computers and telephones, has been rapidly increasing. Lightning damage to these home electric appliances has a great impact on a highly sophisticated information society. There are cases in which lightning overvoltages in low‐voltage distribution lines cause malfunctions in them, even though they are equipped with surge protective devices to protect against lightning overvoltages. Therefore, for lightning protection of low‐voltage equipment including home electric appliances, it is important to understand the phenomenon of lightning overvoltages in low‐voltage power distribution lines. However, many aspects of this problem are not entirely clear, in particular how they are generated. The Tokyo Electric Power Company carried out lightning observations on low‐voltage distribution lines. The observation results provide a statistical distribution of lightning overvoltages in low‐voltage distribution lines. A mechanism for generating lightning overvoltages in low‐voltage distribution lines is inferred from the observed waveforms and facilities data. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 12–21, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21299

Recently, the number of home electric appliances, such as personal computers and telephones, is rapidly increased. Lightning damage to these home electric appliances has a great impact on highly sophisticated information society. There are some cases that lightning overvoltages on low-voltage distribution lines cause malfunction of them, though they equipped surge protective devices to protect against lightning overvoltages. Therefore, for lightning protection of low-voltage equipments including home electric appliances, it's important to understand the phenomenon of lightning overvoltages on low-voltage distribution lines. However, it's not so clear including the generation of them.The Tokyo Electric Power Company carries out the lightning observation on low-voltage distribution lines. The observation results provide the statistical distribution of lightning overvoltages on low-voltage distribution lines. The generation mechanism of lightning overvoltages on low-voltage distribution lines is assumed based on observed waveforms and facilities data.