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Renewable energies such as wind power and photovoltaic systems are expected to be ones of the global warming solutions, because of their low carbon emission. Wind turbine generator has high electric power capacity, and the top of its blade exceeds 100m. As a result, lightning frequently strikes a wind tower or a blade, and the turbine sometimes stops generating for a long time. Rational lightning protection design and countermeasures for lightning damages should be studied and developed. As lightning protection design for wind turbine should be also targeted for winter lightning as well as normal lightning, there are many problems to be discussed. This report describes a grounding system, which is the most fundamental element, associated with the lightning protection for wind turbine generator system. Fundamental lightning protection design and countermeasures are mentioned. Lightning performances of grounding systems based on experimental and calculation results are shown. Low grounding resistance of a couple of Ohms is adopted in most of wind turbine generator systems. However, according to the results, the grounding resistance under high frequency currents has a high transient response, and makes steep lightning overvoltages in the system. Finally, themes on grounding system to be solved are proposed in order to establish a rational lightning protection design of wind turbine generator system. This report will be also useful for grounding systems of another electric apparatuses and instruments. |
