Strain monitoring in power cables of offshore wind energy plants with femtosecond laser inscribed fibre Bragg gratings

摘要

A fibre Bragg grating sensor system used for monitoring of strain being effective on the power cable of an offshore wind turbine is presented. The Bragg grating structure was inscribed in coated non-photosensitive standard telecommunication fibres using an infrared femtosecond laser and the point-by-point writing technique. Due to the presence of the protective coating of the fibre, the mechanical stability of the resultant sensor device is better than that of a sensor consisting of a bare fibre. A system containing this sensing element was successfully installed and tested in an offshore wind turbine prototype (REpower 6M) in February 2010, near Ellhoft (Germany). The fabrication process of the fibre Bragg gratings, a comparison between the sensor signal and a commonly used strain gauge and measurement results of the online monitoring are presented.