Modelling of breather for transformer health assessment

A mathematical model for estimating the moisture content in silica‐gel inside a breather of a power transformer has been developed. The model equations are derived considering the possible real‐time operating conditions of the transformer. These operating conditions are the fast rise or decrease of oil temperature due to a step change in the electrical loads and the cyclic heating and cooling of the oil due to the natural loading of the transformer. An experimental setup has been developed for monitoring the variations in moisture concentration in silica‐gel inside an artificially constructed breather. Finally, the validation of the model has been done with the experimentally obtained data and the standard input signals. The model has been analysed using the equilibrium relations of the moisture concentration between the silica‐gel and the environment of the breather. The response of the model indicates the dynamic behaviour of a moisture sensor placed in the breather. The model has been used in predicting the moisture level in the silica‐gel, the moisture concentration inside the breather and the degradation in the performance of the silica‐gel.