Fiber Optic Moisture Measurement in Transformers

The feasibility of a fiber optic measurement of the moisture content in transformer insulation was assessed. The conclusion was that it is possible and that an accuracy of a fraction of a percent is possible. We also i nvestigated the value and use of data from such a measurement. By choosing the right sensor placement, the modelling of the transformer can be improved and thus, earlier warnings of potential problems can be obtained. A third objective was to a plan for co ntinued development, which has been done and we are now investigating in what form the plan should be implemented.

The pre-study results show that it is both possible and motivated to continue developing the measurement technology. It is expected that this leads to an implementable moisture measurement technique that can improve models and contribute to better predictive maintenance of transformers. In the long term it can also be used for transformer design improvements.

The work has been a collaboration between RISE and Hitachi Energy. RISE has carried out the main part of the technical evaluation, for example the spectroscopic measurements. Hitachi, who intends want to implement the technology, has contributed with analysis on where measurements are most relevant, how the data can be used, sensor requirements, and sample preparation.