FIBER OPTIC TEMPERATURE SENSING IN HEAT EXCHANGERS AND BEARINGS FOR HYDRO GENERATORS
Keywords:Temperature measurement, Fiber Bragg gratings, High power generator
This work presents the design and tests results for two temperature sensors based on quasi-distributed Fiber Bragg gratings (FBG) applied to bearings and heat exchangers of hydro generators. The temperature increase in the bearing is generally due to excessive shaft misalignment, low oil level or dirt in the lubricant oil. The heat exchanger suffer mostly because the onset of biological fouling decreasing its efficiency and increasing the generator temperature. The bearing sensor has four FBG to monitor the vertical temperature gradient in the lubricant oil. Temperature stability tests were carried out lasting twenty two hours in laboratory with bearing sensor. The calculated uncertainty of each FBG matches the requirements for temperature monitoring in hydroelectric generator bearings. Longer the heat exchanger is monitored with fifteen FBG to map the temperature of the air that comes from the generator stator and passes through the heat exchanger. A preliminary installation in the heat exchanger inside a power plant is reported. The biggest temperature reached by the fifteen FBG was 38 Â°C during the generator operating at 180 MW. The tests have proven that the temperature measured is associated with the generator load condition.
 B. Glemmestad, S. Skogestad, and T. Gundersen, “Optimal operation of heat exchanger networks,” Comput. Chem.
Eng., vol. 23, no. 4–5, pp. 509–522, May 1999.
 V. R. Radhakrishnan, M. Ramasamy, H. Zabiri, V. Do Thanh, N. M. Tahir, H. Mukhtar, M. R. Hamdi, and N.
Ramli, “Heat exchanger fouling model and preventive maintenance scheduling tool,” Appl. Therm. Eng., vol. 27,
no. 17–18, pp. 2791–2802, Dec. 2007.
 G. C. Stone and R. Wu, “Examples of stator winding insulation deterioration in new generators,” 2009 IEEE 9th
Int. Conf. Prop. Appl. Dielectr. Mater., pp. 180–185, Jul. 2009.
 D. L. Evans and U. S. Army Corps of Engineers, “IEEE Working Group Report of Problems With Hydrogenerator
Thermoset Stator Windings,” IEEE Trans. Power Appar. Syst., vol. PAS-100, no. 7, pp. 3284–3291, 1981.
 C. E. J. Bowler, P. G. Brown, and D. N. Walker, “Evaluation of the Effect of Power Circuit Breaker Reclosing
Practises on Turbine-Generator Shafts,” IEEE Trans. Power Appar. Syst., vol. PAS. 99, no. 5, pp. 1764–1779, 1980.
 D. Stojanovic, D. Petrovic, and N. Mitrovic, “Torsional Torques of Big TurbineGenerator Shafts Due To
Malsynchronization,” Mediterr. Eletrotchnical Conf. - MEleCon, vol. III, pp. 1051 – 1054, 2000.
 A. Tétrault, “Rotor shape vs . rotor field pole shorted turns,” in Internacional Conference on Condition monitoring
and Diagnosis, 2012, no. September, pp. 133–136.
 E. Wallhäußer, M. A. Hussein, and T. Becker, “Detection methods of fouling in heat exchangers in the food
industry,” Food Control, vol. 27, no. 1, pp. 1–10, Sep. 2012.
 R. Kashyap, Fiber Bragg Gratings. San Diego: Academic Press, 1999.
 T. Erdogan, “Fiber grating spectra,” J. Light. Technol., vol. 15, pp. 1277–1294, 1997.
 A. Othonos and K. Kalli, Fiber Bragg gratings, vol. 68, no. 12. 1999.
 M. Willsch, “Fiber Optical Sensors in Power Generation,” in Third Asia Pacific Optical Sensors Conference, 2012,
vol. 8351, pp. 835137–835137–9.
 C. Martelli, E. V. Silva, K. D. M. Sousa, F. Mezzadri, J. Somenzi, M. Crespin, and H. J. Kalinowski, “Temperature
sensing in a 175MW power generator,” in OFS2012 22nd International Conference on Optical Fiber Sensors,
2012, vol. 8421, p. 84212F–84212F–4.
 M. Willsch, T. Bosselmann, and M. Villnow, “Fiber Optic Sensor Solutions for Increase of Efficiency and
Availability of Electric Power Generators,” in Fourth European Workshop on Optical Fibre Sensors, 2010, vol.
7653, pp. 765337–765337–5.
 F. Mezzadri, C. Martelli, E. V. Silva, and J. C. Cardozo da Silva, “Thermal Mapping of a Radiator in a
Hydroelectric Generator using Fiber Bragg Gratings,” in Latin America Optics and Photonics Conference, 2014, p.
 U. J. Dreyer, A. B. Di Renzo, V. de Oliveira, H. J. Kalinowski, C. Martelli, I. de L. Jr., J. C. C. da Silva, and E.
Vagner, “Sensor de Fibra Ótica para Monitoração de Mancais de Gerador Elétrico de 180 MW,” in MOMAG 2014 -
Curitiba, 2014, pp. 1054–1057.
 A. D. Kersey, M. a. Davis, H. J. Patrick, M. LeBlanc, K. P. Koo, C. G. Askins, M. a. Putnam, and E. J. Friebele,
“Fiber grating sensors,” J. Light. Technol., vol. 15, no. 8, pp. 1442–1463, 1997.
 A. A. G. Jr and A. R. de Sousa, Fundamentos de metrologia científica e industrial, 1st ed. Barueri SP: Manole,
 Inmetro, GUM 2008 - Guia para a expressão de incerteza de medição. 2008.