Optical low-cost temperature point sensor

In the area of high-voltage apparatus only the use of optical sensors offers the possibility to watch important measurands, e.g. current, voltage, partial discharge and temperature, in regions of high electric or magnetic fields. Among other concepts optical point sensors are able to detect the temperature. The new temperature point sensor is based on the measurement of a varying linear birefringence in optical fibres, produced by the thermal influence of epoxy adhesives. On the basis of the different thermal expansion coefficients of the fibre and the adhesive, a temperature change results in mechanical pressure, Because of this pressure a linear birefringence is: induced into the fibre and the polarization of the light is influenced. Experimental investigations show a significant and repeatable temperature dependence of the ellipticity of the light in the range of measurement between 10 degreesC and + 120 degreesC. Among the common advantages of fibre-optical sensors the main advantages of the new sensor-system are the simple assembly, consists of low-priced standard components, and the good possibility of integration into power transformers because of its small dimensions.