Fibre=optic internal temp. sensor for transformer windings - uses differential fluorescent emission of temp. sensitive phosphors stimulated by UV light

摘要

Temp. sensor (40) as designed to fit into confined spaces, esp. between the windings (34) of a transformer. It consists of an optical fibre (14) enclosed within a sheath (12) made of a fluorinated polypropylene-ethylene resin feeding light signals to a processing equipment. The probe fits into a small housing which protects it from the compressive forces of the windings by means of spacer-plates (24, 32). An end-stop (36), which has a cone-shaped void (38) in it, limits the axial movement of the fibre. The radius of the bends in the sheath are kept above 25 mm. The end of the fibre terminates in a resin module (40) which is impregnated with two sorts of phosphor. Under stimulation from UV light sent down the fibre, red or green light is emitted. One of the phosphors has a negative temp. coefft. of fluorescence and its emission will fall to around zero when at 125 deg. C. The other has constant emission with temp. using filters, the difference in the transmitted red and green light intensities is detected.