Transformer insulation monitoring by optical sensing techniques

High voltage transformers use paper to insulate the electrical windings present in the core which is then subsequently immersed in oil. In service, the temperature of the windings will increase to typically 80 degrees C. If the transformer is loaded to beyond its design ratings, the temperature can exceed 100 degrees C causing the cellulose chains in the paper to cleave at an accelerated rate, resulting in the degradation of mechanical strength and performance of the insulation. If unchecked, this can lead to catastrophic failure of the transformed and accompanying disruption to electricity supply and large economic losses to the operating utility. Furfuraldehyde (FFA) is a chemical by-product which is released into the oil by the thermal degradation of the paper winding. The concentration of FFA within the oil has been directly related to the condition of the paper insulation. We have developed absorbance and fluorescence optical techniques incorporating a novel FFA- sensitive material which we have invested at our laboratories. This material has been incorporated into a prototype portable optoelectronic instrument for the measurement of FFA at the site of the transformer. Results of experiments will be presented, and the implication of these results for condition monitoring of HV transformer will be discussed