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Chiba, Japan

Yanagawa S.,Shoden Co. | Natsuno D.,Toyosekkei Co. | Yamamoto K.,Kobe City College of Technology
2011 7th Asia-Pacific International Conference on Lightning, APL2011 | Year: 2011

Accidents caused by natural phenomena such as lightning are serious problems for the diffusions of wind power generations. Those problems affect the safety and reliability of wind turbine generator systems. Most of the breakdowns and malfunctions of the electrical and control systems inside wind turbines are caused by a rise in ground potential due to lightning. To solve those problems, the field tests have been carried out so far. In this paper, new measurements of transient grounding characteristics have been carried out at a wind turbine in the vicinity of the Sea of Japan, and new data of the transient characteristics have been obvious. © 2011 IEEE. Source


Ishii M.,University of Tokyo | Saito M.,University of Tokyo | Sonehara T.,Shoden Co.
IEEJ Transactions on Power and Energy | Year: 2014

Lightning hits to Tokyo Skytree have been under observation by a high-speed camera since August 2012. First data were obtained when negative downward lightning flashes hit the tower on July 08, 2013. This letter reports on observation of a negative single-stroke flash with a positive upward leader initiated from Tokyo Skytree extended about 400m before connection with a downward leader. Simultaneously observed electric field observed by a fast antenna showed much weaker stepped-leader pulses compared to ordinary negative downward flashes hitting ground. © 2014 The Institute of Electrical Engineers of Japan. Source


Yamamoto K.,Chubu University | Yanagawa S.,Shoden Co. | Sekioka S.,Shonan Institute of Technology
Electronics and Communications in Japan | Year: 2013

When lightning strikes the tower of a cellular phone base station or other such facility, power and communications equipment in the vicinity of the tower may suffer extensive damage due to the lightning current flowing backward from the grounding system of the tower. The use of a deeply buried grounding electrode has been proposed recently to suppress such backflow currents and potential rises in the vicinity of towers. The deeply buried grounding electrode is a bare conductor buried deeply in the ground, which is connected to a lightning rod on the ground by an insulated wire. When lightning strikes the lightning rod, the lightning current is directed to the electrode, from which it diffuses to the ground. Deeply buried grounding electrodes have been installed at cellular phone base stations and other such facilities to solve problems caused by backflow currents and potential rises. A grounding mesh is usually laid around such base stations as a grounding system for the facilities on the ground. Therefore, it is important to understand the interactions between the deeply buried grounding electrode and the grounding mesh. In this paper, experiments on the interactions between a grounding mesh and a deeply buried grounding electrode are described. Additionally, the transient characteristics of the mesh grounding have been investigated. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(12): 52-60, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11488 © 2013 Wiley Periodicals, Inc. Source


Yamamoto K.,Kobe City College of Technology | Yanagawa S.,Shoden Co. | Sekioka S.,Shonan Institute of Technology | Yokoyama S.,Japan Central Research Institute of Electric Power Industry
IEEJ Transactions on Electrical and Electronic Engineering | Year: 2010

In order to exploit high wind conditions, wind turbine generator systems are often constructed in places where few tall structures exist; therefore, they are often struck by lightning. Much of the damage caused by lightning is from the resulting breakdown and malfunction of the electrical, communication, and control systems inside the wind turbine generator system; these breakdowns can be attributed to a rise in electric potential both within the system and in the surroundings due to lightning. Impulse tests were conducted on a wind turbine generator system at a disposal site where the conductivity of the ground was very low, like that found on the surface of the sea. The rise in ground potential of the system, and around its foundation, was measured. When a wind turbine generator system is constructed at a site where the grounding resistivity is very low, the potential rise at the wave front typically becomes larger than that of the steady state because of the inductivity of the grounding system. Therefore, it is very important that the transient characteristics of the grounding system are well understood. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. Source


Yamamoto K.,Chubu University | Yanagawa S.,Shoden Co.
2012 31st International Conference on Lightning Protection, ICLP 2012 | Year: 2012

Lightning damage to facilities inside or in the vicinity of wind turbines becomes remarkably common. Most of the breakdowns and malfunctions of the electrical and control systems inside or in the vicinity of wind turbines are caused by ground potential rise due to lightning current flowing into the grounding system of the turbine. To clarify the transient characteristics of the wind turbine grounding systems and to understand the mechanism of the breakdowns and malfunctions, we have carried out field tests. In this paper, the measurements of transient grounding characteristics carried out at wind turbines are descried. © 2012 IEEE. Source

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