Power transformer is the one of the largely important as well as one of the costly elements in the electricity grid. Any
malfunction of this element may affect the reliability of the entire network and could have considerable economic impact
on the system. For several reasons, overloading of power transformers beyond their rating has been reported frequently.
The primary issue leading to the failure of transformer is contamination of transformer oil by the working components
due to prolonged high temperature exposure. Transformer oil temperature can be utilized as a primary parameter in
monitoring the life of the transformer. At present, electrical approach are vulnerable to electromagnetic interference and
are limited by sensors lifetime. Other non-contact techniques are ineffective due to difficulties in processing the output
signal. In this work a CuAlNi/Polyimide shape memory alloy composite has been applied to act as a temperature sensor
in mineral oils. The composite film has been developed through thermal evaporation which exhibited two-way
displacement without and post-processing and training. The developed films are employed in a custom made oil rig and
the suitability of using it as a circuit breaker in temperature sensing application has been probed. The circuit breaker can
be triggered by measuring the displacement of the bimorph using laser displacement sensor. The measurement is of noncontact
type and the temperature can be monitored at regular intervals. For comparison a procure Nickel-Titanium spring
with transformation temperature less than 100 °C is also used for the studies. The results show that the developed
bimorphs has good sensitivity of 0.2 mm/°C and the output displacement is significant. Further the effect of
contamination in the mineral oils is also probed by adding known amounts of impurities and the ageing effect has been
studied. A higher resolution measuring system using interferometry has been proposed.
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