Teru Miyazaki

A Field Study of Lightning Surges Propagating Into Residences

In the highly information-based society of today, lightning damage to home electric appliances, such as personal computers and facsimile machines is having a greater impact, indicating a growing public interest in countermeasures for lightning. However, many things remain unknown about lightning surges that propagate into residences. The Tokyo Electric Power Company had observed the patterns of intrusion of lightning surges into residences using lightning surge waveform detectors installed at ordinary residences and obtained observation data on 18 lightning strokes between 2003 and 2006. These observation results can be used to examine the patterns of propagation of lightning surges into residences. In some observation cases of lightning strokes to the ground, lightning surge currents were estimated to flow from the ground into residences. These valuable data will be useful for elucidating the lightning surge propagation in the low-voltage distribution system including residences.

A Detailed Field Study of Lightning Stroke Effects on Distribution Lines

Field study of lightning stroke effects, particularly the mechanisms that produce distribution line faults, is essential for designing rational lightning protection for distribution lines. The Tokyo Electric Power Company has conducted photographic research and observed voltage and current waveforms due to lightning in actual distribution lines since 1996, obtaining 284 datasets, including 62 for direct hits to the lines. These results permit a comprehensive study of each lightning flash; the photographs show the precise location of the lightning, and the waveforms provide detailed analyses of flashovers in the distribution systems. This paper evaluates typical observed datasets, including surge insulator voltage waveforms. In some cases, the direct lightning strokes did not cause distribution line faults because the power follow current extinguished spontaneously after flashover generation. These results provide a solid basis for examining the mechanisms underlying the production of distribution line faults, and can lead to effective lightning protection practices.

An Experimental Validation of Lightning Performance in Distribution Lines

The Tokyo Electric Power Company had conducted field research of voltages and currents in actual distribution lines due to lightning strokes between 1997 and 2001. These results confirm that the distribution line faults are mainly caused by direct lightning strokes to the line. Thus, it is important to simulate lightning performance for direct strokes to establish a lightning protection design of distribution lines. In this paper, statistical data of the observed voltages and currents are analyzed, and the validation of the observation results for the direct lightning strokes using a lightning surge analysis model is conducted. The observation results and the simulation model are useful in clarifying lightning performance in distribution lines.

Lightning Overvoltages in Low-Voltage Circuit for Various Lightning Striking Points

Lightning overvoltages in low-voltage circuits in houses originating from a distribution line or an antenna have been actively studied. However, the mechanism by which damage is caused to home appliances due to a lightning strike to the ground near the house is still unclear. This paper discusses lightning overvoltages and currents in low-voltage circuits for various scenarios, such as a lightning strike to the ground, a direct strike to a distribution line, and a direct strike to an antenna. Simulations are carried out using the Electromagnetic Transients Program. From the simulation results, direct lightning strikes cause the most serious damage to home appliances, but nearby lightning strikes should also be considered when designing lightning protection schemes.

Field Analysis of the Occurrence of Distribution-Line Faults Caused by Lightning Effects

Electric supply reliability is an issue of wide importance to both an information-oriented society and electric power companies. This paper focuses on lightning effects on distribution lines. Field research is now underway in the northern part of the Kanto Plain in Japan, and voltage and current waveforms in distribution lines due to lightning hits have been observed since 1996. There are now 284 datasets; these include data on 62 direct flashes to lines. This research reveals that a distribution line can be protected from direct lightning strokes. In some cases, no power follow current was confirmed after a multiple phase flashover, and a statistical analysis was conducted to investigate factors affecting the generation of power follow current. These results can serve as a valuable resource to help clarify the mechanisms underlying the production of distribution-line faults caused by lightning effects.

A Field Study of Lightning Phenomena on Low-Voltage Distribution Lines Including Residences

As society becomes ever more dependent on electronics, interest in the patterns of lightning hazards in low-voltage distribution lines including residences is growing. However, there have been few studies on low-voltage distribution lines and many things remain unknown about the propagation patterns of lightning surges in the field, particularly the intrusion of lightning surges into residences. The Tokyo Electric Power Company has conducted field research of phenomena accompanying lightning flashes to actual distribution systems using lightning-activated cameras as well as lightning surge waveform detectors, obtaining invaluable 101 datasets of lightning flashes between 2002 and 2007. This paper analyzes typical observation examples and estimates the lightning surge propagation routes in low-voltage distribution lines. In some examples, it is inferred that a lightning current flowed in the reverse direction from the residence to the low-voltage distribution line caused by ground potential rise due to the nearby lightning to the ground. These results will be useful for clarifying lightning surge propagation patterns in low-voltage distribution lines.

Verification of the Lightning Protection Effect Produced by the Difference in the Grounding Systems at High Voltage Receipt Equipment

The integrated grounding system which bundles up all various grounding electrodes has been introduced as a new grounding system from the movement toward the formation of standard international adjustment in recent years, and the example adopted also in high voltage receipt equipment is increasing. However, there are very many differences between TN system in the West and TT system in our country and points to be checked since the grounding purpose is crossing variably as the account of the upper stated, when adopting an integrated grounding system, and there are few examples checked experimentally until now. In this research, the viewpoint was extracted to lightning protection in such a background, the grounding system and integrated grounding system which were used with high voltage receipt equipment until now were compared, and real experiment and EMTP analysis were carried out for the purpose of grasping the characteristic in an integrated grounding system. From the experiment result in high voltage receipt equipment, and an analysis result, the result verified about the usefulness of integrated grounding to lightning protection is reported.