Quasi-distributed temperature measurement for stator bars in large generator via use of Fiber Bragg Gratings

This paper describes a multiplexed temperature measurement approach to monitor inner temperature of stator bars in large power generator via use of Fiber Bragg Gratings. By embedding the optical fiber with multiple Fiber Bragg Gratings into stator bars, quasi-distributed measurement is realized. Fiber Bragg Gratings are embedded at some positions closely related to temperature. Empirical results show that bare Fiber Bragg Gratings are damaged easily, and their temperature features are affected easily by insulation material. The Fiber Bragg Gratings packaged by stainless steel capillaries can avoid damage from high temperature and pressure during being embedded into stator bars. The solid strand and position switching insulation are capable to be embedded Fiber Bragg Gratings. The results of temperature experiment demonstrate that the Fiber Bragg Gratings embedded into stator bars keep good characters. The coefficient between wavelength and temperature is 0.99966. The wavelength-time response curves of the Fiber Bragg Gratings coincide with temperature-time response curves of the thermocouples at the same position, and Fiber Brag Grating sensors have the same response time to corresponding thermocouples. So the conclusion can be drawn that quasi-distributed temperature measurement based on Fiber Bragg Gratings can monitor temperature inside the large power generator in real time.